WO2010026379A9

WO2010026379A9 - A turf aerator

Info

Publication number: WO2010026379A9
Application number: PCT/GB2009/002121
Authority: WO
Inventors: William Lyle Warke
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-09-03
Filing date: 2009-09-03
Publication date: 2010-06-24
Anticipated expiration: 2011-03-03
Also published as: WO2010026379A2; GB2476021A; GB2476021B; GB201105566D0; GB0816102D0; WO2010026379A3

Abstract

A turf aerator apparatus adapted for releasable engagement with a tractor, the turf aerator apparatus comprising drive means (5, 14) which drives a one or more cranks (8) which are arranged in an array comprising a crank-set or crank module, the or each crank-set or crank module being adapted to drive tines (13) or other ground penetrating tools into the ground wherein the or each crank-set is provided with an independent shock absorbing crank driving means (7, 16, 18).

Description

A TURF AERATOR

The present invention relates to a turf aerator, in particular to a turf aerator particularly suitable for deep aerating applications.

Turf aerators are well known whereby tines or spikes are plunged through the turf of athletic fields, playing fields, parks, golf courses or other turf grass areas in order to decompact and aerate the soil below. Typically these types of turf aerators fall into one of two categories, namely surface aerators and deep aerators. Surface aerators penetrate the top 15 cm of soil while deep aerators will penetrate down to 45 cm. It has become evident however that continued or repeated aeration of the top layer of soil can lead to or exacerbate the development of hardpan layers whereby the soil just below the aerated depth forms into a densely compacted layer. Such hardpan layers are impenetrable by grass roots and so the roots tend to grow sideways across the top of the hardpan layer which results in a grass surface that is susceptible to drought or other adverse conditions. For many years deep aerator machines have been available which are capable of penetrating the soil to depths of 45 cm and greater. In order to break up existing hardpan layers and alleviate the problem of hardpan layers developing below the surface, these machines must be used on a regular basis. The problem with deep-tine aerators is that traditionally they are slow and cumbersome. While a surface aerator will plunge the tines into the soil between 400 - 500 times per minute, a traditional heavy deep aerator will plunge the tines into the soil at a much slower rate between 100 - 200 times per minute. Thus the time in man-hours that it takes to perform deep aeration is a problem to modern sports facilities that have ever increasing demand for available playing time on their grounds. Surface aeration tends to be performed in many turf maintenance schedules while slower more expensive deep aeration is neglected. In recent times manufacturers have come to recognize the need produce faster machines that are capable of withstanding the significant impact wear, particularly on the tines and in the operating mechanism. This however gives rise to further problems because at increased depths the machine must operate through compacted hardpan layers and into soil regions where large ground inclusions such as stones or rocks are more likely to be present. Thus at high operating speeds the associated wear and damage imparted to the machines is significantly increased which leads to decreased operating efficiency and increased down-time. It is therefore an object of the present invention to alleviate the disadvantages associated with the prior art.

Accordingly, the present invention provides a deep turf aerator apparatus adapted for releasable engagement with a tractor, the turf aerator apparatus comprising drive means which drives a one or more cranks which are arranged in an array comprising a crank-set or crank module, the or each crank-set or crank module being adapted to drive tines or other ground penetrating tools into the ground wherein the or each crank-set is provided with an independent shock absorbing crank driving means.

Ideally, the independent shock absorbing crank drive means provided on each crank-set or crank module comprises a crank, a drive sprocket, a crank sprocket and a suspension sprocket, the crank being bearing mounted to the turf aerator chassis and being chain driven by drive sprocket.

Advantageously, the drive sprocket rotates in a clockwise direction so that the chain moves in a clockwise direction about the crank sprocket and the suspension sprocket, the suspension sprocket being located on the drive side of said drive sprocket.

Advantageously, the drive sprocket pulls the drive chain around the suspension sprocket from below.

Conveniently, the suspension sprocket is rotatably mounted to a suspension arm, said suspension arm being pivotal Iy mounted at its lower end about a mounting pivot which is located on the chassis proximate the drive sprocket.

Ideally, at an upper free end of the suspension arm distal from the mounting pivot there is provided a spring damping means which connects between said suspension arm and a mounting point provided at an upper part of the chassis.

Preferably, the mounting point comprises an adjustable pivot connection point which enables a precise amount of compression to be applied to the spring damping means so that the suspension arm applies a desired exact tension to the crank drive chain via the suspension sprocket. Conveniently, rotary motion of the crank moves a connecting rod and tining head in upward and downward reciprocating motion so that tines mounted to the tining head are repeatedly plunged through, and removed from, the ground surface and the subsoil.

Preferably, lateral movement of the crank, connecting rod and tining head assembly during reciprocating motion is restrained by a tining arm which is pivotal Iy connected between the turf aerator chassis and the tining head.

Conveniently, during normal operating conditions tension in the drive chain is equal on respective driving (lower) and non-driving (upper) sides of the drive and crank sprockets thereby eliminating backlash in the crank drive mechanism.

Advantageously, when a stone or similar ground inclusion is encountered by the tines of the turf aerator as they plunge into the ground, tension in the drive chain will exceed a pre-set amount as determined by the adjustment of the spring damper. Conveniently, the resulting increased tension in the drive chain causes the suspension sprocket to be pulled upwardly which in turn causes suspension arm to rotate upwardly about the suspension arm pivot and thereby compressing the spring damping means.

Conveniently, upward motion of the suspension sprocket moves said sprocket towards a notional centreline extending between the centres of the respective drive and crank sprockets thereby in effect shortening the length of the drive chain on its lower driving side. Advantageously, this enables the crank sprocket to slow or stop momentarily in order for the aerator apparatus to clear the ground inclusion.

Ideally, chain retaining rollers are provided to prevent chain from rising off or jumping the drive and/or crank sprocket as slack gathers at the top non-driving side of the chain between said drive and crank sprockets.

Preferably, each chain retaining roller is located on centreline projecting substantially orthogonal to a centreline running between the drive sprocket and the crank sprocket, each roller arranged tangentially to said drive chain thereby preventing it from rising off or jumping said sprockets. In a further aspect of the invention there is provided a tine holder suitable for mounting to the tining head of a turf aerator, the tine holder adapted to hold a plurality of tines in releasable engagement, the tine holder comprising a body portion and a plurality of movably mounted clamp caps which are held loosely against said body portion.

Ideally, the body portion comprises a plurality of arcuate recesses which are adapted to cooperate with complementary recesses provided on the clamp caps so as to define a substantially circular aperture through the tine holder when said caps are brought into close proximity with said body portion, the substantially circular apertures being adapted to receive and engage with the upper ends of tines inserted therein.

Conveniently, each arcuate recess on the body is further provided with a slot which holds an anti-release roll pin that is adapted to engage with a complementary groove formed around the upper end of a tine when said tine is inserted into a substantially circular aperture.

Advantageously, a release bolt or bolts which extend from the front to the rear of body portion and through a clamp barrel provides a locking means by which the tines are releasably secured to tine holder.

Ideally, each clamp cap is provided with at least one chamfered face, the chamfered face being arranged to contact a clamp barrel.

Conveniently, tightening of the release bolt draws the clamp barrel towards the body portion so that said clamp barrel impinges against the chamfered face of a clamp cap, thereby drawing said clamp cap towards said body portion thus tightly securing a tine or tines to the tine holder.

Ideally, each clamp cap is provided with at least one face which is arranged at an angle which extends rearward from the arcuate recess formed thereon and which in use projects away from the body portion so as to enable said clamp cap to be drawn more tightly around a tine held in the confines of the substantially circular aperture.

Conveniently, adjacent clamp caps are drawn towards the body portion by a single release bolt and clamp barrel. Conveniently, the provision of a spring bias means on the release bolt or bolts of the tine holder ensures that sufficient tension is maintained in the body portion, clamp cap, and clamp barrel assembly so that a tine or tines are retained in place against the roll pin in advance of final tightening of the release bolt or bolts which is effected by a socket, spanner or other suitable means, In use, quick and efficient removal of a tine or tines is effected by the slight loosening of the release bolt or bolts so that the tine or tines can be pulled free from tine holder.

Ideally, each clamp cap is provided with a cut-out section on the at least one chamfered face which enables a release bolt or bolts to pass between caps when arranged adjacent one another.

Advantageously, the provision of the cut-out sections prevents the clamp caps from rotating freely about their retaining bolts when release bolt or bolts are loosened to an extent that the spring bias means is no longer effective and barrel is not in forced contact with the chamfered faces of said clamp caps. Conveniently, cut out sections on clamp caps having two chamfered faces prevents said caps from falling from the tine holders when release bolt or bolts are similarly loosened.

Ideally, each release bolt is provided a collar having a recess into which the spring bias means is seated, the recess being of sufficient depth so as to fully compress the spring bias means before coming into contact with the body whereupon the release bolt can be tightened firmly in order to clamp a tine or tines with sufficient force so as to prevent movement or slippage but without imparting damage to the said spring bias means.

In a still further aspect of the invention there is provided a means for tine angle adjustment.

In a still further aspect of the invention there is provided a means for manually adjusting the tine penetration depth by raising and lowering a ground roller with respect to a turf aerator chassis, the means comprising a depth cross beam which is pivotally mounted to the chassis, the depth cross beam being manually operable by a handle so as to raise and lower ground roller legs to which the cross beam is pivotally connected and the ground roller is mounted.

Ideally, the depth cross beam extends across the width of the aerator machine about which it is rotatably mounted at each end. Conveniently, the depth cross beam is provided with a depth adjusting bracket that is attached at its upper end to said depth cross beam, the adjusting bracket being provided with a swivel nut that is connected to the handle by a screw so that rotation of said handle causes the depth adjusting bracket to rotate and depth cross beam to swivel about its mountings. Advantageously, the swivel action of the depth cross beam about its mountings raises or lowers the ground roller legs.

Ideally, each ground roller leg is maintained in a substantially upright orientation by spaced apart slide-blocks or similar suitable guides which are provided on the turf aerator.

Preferably, the slide-blocks are arranged at a position on the ground roller legs intermediate the upper end of the leg and the ground roller end of the leg.

Ideally, for ease of adjustment of the tine penetration depth, there is provided a support spring plunger that is incorporated between the ground roller and the aerator chassis, the support spring plunger being pivotally connected at its upper end and lower ends to the depth cross beam and aerator chassis, respectively, the support spring plunger acting to support the weight of the ground roller thereby relieving pressure on the depth adjusting screw and allowing the depth adjusting handle to be easily turned.

In a still further aspect of the invention there is provided a means for automatically adjusting the tine penetration depth by raising and lowering a ground roller with respect to a turf aerator chassis, the means comprising a depth cross beam which is pivotally mounted to the chassis, the depth cross beam being operable by electrically operated ram comprising a load sensing switch at its upper end which is in rolling contact with said depth cross beam, a ground roller weight sensor switch, and a roller depth sensor spring arranged so as to adjust the ground roller upwardly and downwardly according to turf conditions to maintain a specific pressure between said ground roller and the turf surface thus maintaining maximum tine penetration with maximum aerator stability.

Other aspects of the invention are defined in the appended claims which are incorporated into the description by reference. The invention will hereinafter be more particularly described with reference to the accompanying drawings which show, by way of example only, the turf aerator of the invention.

In the drawings:

Figure 1 is schematic front view of a turf aerator in accordance with the invention;

Figure 2a and Figure 2c are schematic side elevations of the turf aerator showing the operation of a crank suspension means in accordance with the invention;

Figure 2b and Figure 2d are side elevations of the turf aerator showing the operation of the crank suspension means when a rock or similar ground inclusion is encountered;

Figure 3 and Figure 4a are schematic side elevations of the turf aerator showing the function of a tine angle adjustment means in accordance with the invention, the tine angle adjustment means shown set for maximum heave, Figure 3 and Figure 4 showing the tine ground entry and ground exit positions respectively;

Figure 4b and Figure 4c are detailed views of the heave spring mechanism of the tine angle adjustment means of the invention, the tine angle adjustment means set for maximum heave;

Figure 5 and Figure 6 are schematic side elevations of the turf aerator showing the function of the tine angle adjustment means shown set for minimum heave, Figure 5 and Figure 6 showing the tine ground entry and ground exit positions, respectively;

Figure 7a, Figure 7b and Figure 7c are isometric views of a tine holder in accordance with the invention, the tine holder being adapted to releasably receive two tines;

Figure 8a is an isometric view of a tine holder in accordance with the invention, the tine holder being adapted to releasably receive three tines;

Figure 8b to Figure Be are further detailed illustrations of showing the tine holder of Figure 8a. Figure 9 is an isometric view of a tine holder in accordance with the invention, the tine holder being adapted to releasably receive six tines;

Figure 10 is a plan view of the tine holder shown in Figure 9;

Figure 11 is a detailed view of Figure 10 showing the tine holder locking means in accordance with the invention;

Figure 12 is a detailed view of a tine holder clamp camp in accordance with the invention;

Figure 13 is a schematic side elevation of the turf aerator showing the operation of a manual tine depth adjustment means, the tine depth adjustment means shown set for maximum tine penetration depth;

Figure 14 is a schematic side elevation of the turf aerator showing the operation of the manual tine depth adjustment means, the tine depth adjustment means shown set for minimum tine penetration depth;

Figure 15 is a schematic side elevation of the turf aerator showing the operation of an exemplary automatic tine depth adjustment means;

Figure 16 is a schematic illustration of the tine angle geometry showing a vertical tine at the bottom of the crank stroke;

Figure 17 is a schematic illustration of the tine angle geometry showing a vertical tine at the top of the crank stroke;

Figure 18 is a schematic illustration of the tine angle geometry showing an angled tine at the bottom of the crank stroke;

Figure 19 is a schematic illustration of the tine angle geometry showing an angled tine at the top of the crank stroke; Figure 20 is a schematic illustration of a modified tine angle adjustment means in accordance with the invention; and

Figure 21 is a schematic illustration of an adjustable means to set and maintain a desired tension in a crank drive chain; and

Figure 22 is a schematic side elevation of the turf aerator showing the operation of a modified automatic tine depth adjustment means.

Referring initially to Figure 1 and Figure 2a, a turf aerator in accordance with the invention comprises a chassis 1 adapted for mounting to a tractor by means of a harness having upper and lower linkage points 3 and 4 respectively, a drive means which drives a plurality of cranks 8 that are arranged in an array comprising a crank-set or crank module, each crank-set being adapted to drive tines 13 or other ground penetrating tools into the ground wherein each crank- set is provided with an independent shock absorbing crank driving mechanism. The turf aerator further comprises a tine angle adjustment mechanism, a depth control system and a plurality of quick-release tine holders 12.

Referring to Figure 2a, a crank drive means having a shock absorbing crank driving mechanism in accordance with the invention will be described. For clarity the drive and suspension mechanism of a single crank in the array is illustrated only. The crank drive means having a shock absorbing crank driving mechanism in accordance with the invention comprises a crank 8 which is bearing mounted to chassis 1 , a drive chain 14 which extends around a drive sprocket 5, crank sprocket 6, and suspension sprocket 7, the chain being driven by drive sprocket 5 which rotates in a clockwise direction so that said chain moves in a clockwise direction about crank sprocket 6 and suspension sprocket 7 which is located on the drive side of drive sprocket 5. Suspension sprocket 7 is rotatably mounted to suspension arm 16, said suspension arm being pivotally mounted at its lower end about pivot 17 which is located on the chassis proximate drive sprocket 5. At the upper free end of suspension arm 16 distal from pivot 17 there is provided a spring damping means 18 which connects between said suspension arm and a mounting point 18b comprising an adjustable pivot connection point provided at an upper part of chassis 1 , the adjustable pivot connection point enabling a precise amount of compression to be applied to spring damping means 18 which in turn enables suspension arm 16 to apply a desired exact tension to crank drive chain 14. During normal operation of the turf aerator chain 14 is moved around crank sprocket 6 thereby rotating crank 8 thus moving connecting rod 9 and tining head 11 in upward and downward reciprocating motion so that tines 13 held by tine holder 12 are repeatedly plunged through, and removed from, the ground surface 21 and the subsoil 22. During the reciprocating motion of the tining head 11 , crank 8 and connecting rod 9 assembly, lateral movement of said assembly is restrained by tining arm 10 which is pivotally connected between chassis 1 and tining head 11 at pivot points 19 and 20, respectively.

As shown in Figure 2a and Figure 2c, crank chain 14 remains tensioned along its length under normal operating conditions with the drive chain tension equal on the driving (lower) and the non-driving (upper) side of sprockets 5 and 6 thereby eliminating any backlash in the crank drive mechanism. Crank sprocket 6 is driven by drive sprocket 5 which pulls drive chain 14 around suspension sprocket 7 from below.

Referring now to Figure 2b and Figure 2d, when a stone 23 or other ground inclusion is encountered by a tine or tines 13 as they plunge into the soil, the tension in drive chain 14 will exceed a pre-set amount as determined by the adjustment of spring damper 18. This increased tension in drive chain 14 will cause suspension sprocket 7 to be pulled upwardly which in turn causes suspension arm 16 to rotate upwardly about suspension arm pivot 17 and thereby compressing spring damper 18. This upward motion of suspension sprocket 7 moves said sprocket towards a notional centreline extending between the centres of drive and crank sprockets 5 and 6, respectively, thus effectively shortening the length of drive chain 14 on its lower driving side thereby allowing crank sprocket 6 to slow or stop momentarily to clear the ground inclusion 23 as the tractor moves forward. As excess slack chain 14A gathering at the top non-driving side between drive and crank sprockets 5 and 6 causes said chain to loosen, chain retaining rollers 15 are provided to prevent chain 14 from rising off or jumping sprockets 5 and/or 6. As shown in Figure 2c and Figure 2d each chain retaining roller 15 is located on a centreline projecting substantially orthogonal to the centreline running between the drive sprocket 5 and the crank sprocket 6, each roller being arranged tangentially to said drive chain thereby preventing it from rising off or jumping said sprockets 5, 6.

Each crank module or series of crank modules are provided with their own independent suspension means and can work in the manner as described above independently of one another. When a stone or some other ground inclusion 23 is encountered by the tines 13 of a module, only that module is affected and the remaining modules continue operating as normal. The tines which strike the ground inclusion do not have to suddenly lift or support the weight of the module or machine, or at least do not have to do so abruptly, in order for the inclusion to be cleared. In use, and upon contact with a ground inclusion, the machine tends to be stabilized by those tines which remain in the ground as normal. The chain driving mechanism described herein enables the use of more than one driving chain 14 to drive each crank-set. The machine illustrated in Figurei utilizes two three-arm crank modules mounted to chassis 1 by means of two main bearings located between the centre and the two outside tine arms. Two crank sprockets 6 are located alongside the main bearings, each being driven by a drive chain. Adjustment of spring damper 18 ensures that each drive chain is exerting the same driving force to each of the crank sprockets 6. The resulting crank drive is more balanced and in conjunction with the crank suspension means and the elimination of backlash in the crank drive mechanism, the machine can be operated faster speeds with decreased tine and mechanism damage and less fatigue experienced by the machine operator. In order to compensate for chain stretch and wear occurring during the lifespan of drive chain 14, there is provided an adjustable means to set and maintain the desired exact tension in the crank drive chain. Referring to Figure 21 , an indicator means is provided proximate spring damper 18 which is adapted to indicate when adjustment of the chain tension is required and to indicate when the correct drive chain tension is set. As shown in Figure 21 , suspension spring damping means 18 is pivotally connect at an upper end to mounting point 18B on suspension adjuster bracket 18C which protrudes though adjuster mounting plate 18D (see Detail A). Adjuster mounting plate 18D is rigidly attached to the aerator chassis and provides an anchor point for the upper end of suspension spring damper 18. By compressing suspension spring damper 18, downward pressure is exerted to chain suspension arm 16 which pivots on suspension arm pivot 17 thereby applying tension to the said drive chain via suspension sprocket 7. More than one drive chain drives each crank set and the amount of pre-set tension that is applied to each chain should be equal. The amount of chain tension applied is determined by the degree to which the suspension spring damper 18 is compressed. This is indicated by a measuring means which measures the distance between the respective ends of the suspension spring damper. The measuring means comprises a telescopic rod and a sleeve 18J which are pivotally connected at either end of the suspension spring damper 1 at lower connection point 18H (Figure 21, Detail B) and upper connection point 18B (Figure 21 , Detail A), respectively. The amount of adjustment required is indicated by an adjustment zone under-cut portion 18G on a tension indicator rod 18F. At the bottom of an indicator sleeve 18J is a lip 18L which should coincide with an adjustment zone lower step 18K provided on the tension indicator rod 18F when the correct chain tension has been reached. When the adjustment zone under-cut 18K extends to a level or position below lip 18L, adjustment should be made to compress the suspension spring damper 18. This adjustment is effected by loosening an upper adjustment bracket lock nut 18E provided on one side of adjuster mounting plate 18D and tightening the lower lock nut 18M provided on the reverse side of adjuster mounting plate 18D. During use, the turf aerator drive train must cope with an intermittent drive as each tine set plunges into the ground. Conventional chain drives inevitably have an element of slackness in the chains however this can create drive backlash and when applied to an aerator crank and as a result chain breakages are commonplace. By preloading or tensioning the drive chains via suspension arm 16 and suspension spring damper 18 there is not only provided a means to cushion the drive mechanism from the tines impacting against intrusions in the soil but it also ensures that all drive chains are applying the same driving force to the crank and that drive backlash is eliminated.

Referring now to Figures 7a, 7b and 7c, a tine holder 12a adapted to hold two tines comprises a body portion 121 and a plurality of movably mounted clamp caps 122 which are held loosely against the rear of said body portion by retaining bolts 123 which pass through apertures 137 (Figure 12) provided through said caps. Body portion 121 further comprises a plurality of arcuate recesses 124 which are adapted to cooperate with complementary recesses 125 provided on clamp caps 122 so as to define a substantially circular aperture through tine holder 12 when said caps are brought into close proximity with said body portion. Each recess 124 is further provided with a slot 131 A which holds an anti-release roll pin 131 that is adapted to engage with a complementary groove 132 formed around the upper end of a tine 13 (Figure 7c). A release bolt 126 which extends from the front to the rear of body portion 121 via a slot 126B and through clamp barrel 127 provides the means by which tines 13 are releasably secured to tine holder 12. In use, tightening of release bolt 126 draws clamp barrel 127 towards body portion 121 and as said barrel impinges against the respective chamfered faces 128 of clamp caps 122, said caps are also drawn towards said body portion. The provision of a face 129 on each clamp cap 122 which is arranged at an angle which extends rearward from recesses 125 and which in use project away from body portion 121 enable said clamp caps to be drawn more tightly around a tine 13 held in the confines of recesses 124 and 125. Further detail of angled faces 129 is shown in Figure 10 and Figure 11. Referring to Figure 8a and Figure 8b there is shown a tine holder 12b that operates in substantially in the same manner as tine holder 12a but which is provided with additional recess 125b so that a third tine can be accommodated. In order to facilitate the provision of a third tine, tine holder 12b comprises a second release bolt 126b and clamp barrel 127b assembly and an additional clamp cap 122b which is disposed between clamp caps 122. Clamp cap 122b comprises a chamfered face 128 at each side, each chamfered face 128 being adapted to engage with a clamp barrel 127, 127b so that the tine mounted in recess 125b can be firmly secured to the tine holder. The arrangement of tine holder 12b is shown in greater detail in Figures 8b to 8e.

Referring to Figure 9 and Figure 10, it is shown how the tine holder can be readily adapted to hold multitude of tines. In the Figures tine holder 12c is shown with six tines attached. Tine holder 12c operates in substantially in the same manner as tine holder 12b but with series of end caps 122, 122b provided at each side of body portion 121 so that three additional tines can be accommodated. In this embodiment clamp barrels 127 are provided at each end of release bolts 126 so that the clamp caps 122, 122b at each side of body portion 121 are drawn towards, said body portion 121 upon tightening bolts 126.

In use the tines 13 are mounted to tine holders 12a, 12b, 12c by slightly slackening bolt 126 which loosens clamp caps 122. Each tine is then inserted upwardly from below into the aperture defined by recesses 124, 124b, 125 so that roll pin 131 engages with groove 132 formed around the upper end of said tine. The provision of a bevelled edge 132a around the circumference of the upper end of the tines as indicated in Figure 7c and Figure 8e enables said tines to be snap- fitted into the tine holder with the bevelled edge allowing the top portion of the tine to overcome roll pin 131 before it engages with groove 132. Once inserted into a tine holder the upper substantially flat ends 132c of the tines remain flush with the upper surface of the tine holder body portion 121 as shown in Figure 7a and Figure 7b. Thus upon mounting of the tine holder 12 to a tining head mounting plate 11b as described below and shown in Figure 1 and Figure 2a, the tines are prevented from being pushed upwardly through the tine holder as the ends 132c of said tines will be in abutment with mounting plate 11b. Advantageously this arrangement not only ensures that the tines are not pushed through the tine holder but also relieves the load applied to roll pins 131 during turf aeration operations. Conveniently, the provision of a spring bias means 133 acting on release bolt or bolts 126 ensures that sufficient tension is maintained in the tine holder assembly 121 , 122, 122a, 127, so that tines 13 are retained in place against roll pin 131 in advance of final tightening of release bolt 126 using a socket or spanner. Similarly, quick and efficient removal of a tine 13 is effected by the slight loosening of release bolt 126 and the tine pulled free from tine holder 12a, 12b, 12c. Advantageously, other tines which are to be retained will remain mounted to the holder 12, 12b, 12c while release bolt 126 is loosened or tightened.

Referring to Figure 7b and Figure 12, it can be seen that clamp caps 122, 122a are provided with a cut out section 134 on their respective chamfered faces 128 which enables release bolt or bolts 126 to pass between said caps. Advantageously, the provision of cut out sections 134 prevents clamp caps 122 from rotating freely about retaining bolts 123 when release bolt or bolts 126 are loosened to an extent that spring bias means 133 is no longer effective and barrel 127 is not in forced contact with chamfered faces 128. Cut out sections 134 on clamp caps 122a prevent said caps from falling from the tine holders 12b, 12c when release bolt or bolts 126 are similarly loosened. Shown also in Figures 7b, 8a and 11 there is provided a collar 135 provided with a recess into which spring 133 is seated, the recess being of sufficient depth so as to fully compress the spring before coming into contact with the side face of said body 121 whereupon release bolt 126 can be tightened firmly in order to clamp the tines 13 with sufficient force to prevent movement or slippage but without imparting damage to the spring.

Attachment of tine holders 12a, 12b, 12c to the tining heads 11 or the aerator is by means of bolts which extend through mounting plates 11b (Figures 1 , 2a) provided on the tining heads and into threaded holes 136 provided in body portion 121 of said tine holders.

Referring now to Figure 3, Figure 4a, Figure 5 and Figure 6 the principle of deep aerator heave and a means for tine angle adjustment will now be described. With most deep aerators the tining heads 11 are moved up and down in a vertical plane with no horizontal component of motion being imparted apart from that introduced by the arc transcribed by the tining arm 10 about tining arm pivot-point 19 (Figure 1, Figure 2c). With reference to Figure 3 the tines 13 are plunged vertically into the ground while the machine is travelling in forward motion as indicated in the figure, and the tining heads 11 are pulled in the direction of the aerator's travel as they exit the ground as shown in Figure 4a whereby the tines are titled. To enable the tines 13 to tilt in this manner, tining heads 11 must tilt about pivot point 20. Provision is made to enable this tilt by the introduction of heave rod 32. With reference to Figure 4b the tilting of the tining head 11 pushes a link rod 30 forward, the angled bracket 31 in turn being tilted about its pivotal mounting point 38 thereby pulling a heave rod 32 downwards and compressing heave spring 33 thus opening up gap 42 between spring seat 44 and a plunger buffer 41 which is seated on a buffer seat 40 as shown in detail in Figure 4c. When the tines 13 exit the ground heave spring 33 snaps spring seat 44 back against buffer 41 in readiness for the next ground entry plunge. Buffer 41 is made from a suitable impact absorbent material such as rubber or a similar material which is capable of cushion the impact against spring seat 44. The tilting of tines 13 as they exit the ground has the effect of heaving the soil in a manner as would be achieved by pushing a spade or a fork into the ground and pulling backwards at the handle. This heave, as indicated by reference numerals 43 (Figure 4a), 46 (Figure 4b) and 45 (Figure 6), is desirable because it helps to break up the compaction in the soil however it will also disrupts the level playing surface of a sports field so it is desirous to be able to select or alter the degree of heave imparted to the ground surface. In the present invention this adjustment is facilitated by the introduction of tine angle adjustment screw 35 and screw pivot nut 37 as shown in Figure 3, Figure 4b and Figure 4c. Screw pivot nut is pivotally attached to the upper end of substantaially L-shaped heave arm 34 and by rotating a tine angle adjustment handle 36 which is attached to tine angle adjustment screw 35 said screw pivot nut 37 is translated fore and aft thereby tilting, heave arm shaft 39 and thus heave arm 34, thereby raising and lowering spring seat 44 (Figure 4c). Spring seat 44 is pivotaily connected at its diametrically opposing sides to the rear ends of two spaced apart heave arms 34 which operate in unison and between which said spring seat 44 is arranged. By virtue of heave rod 32 and angled bracket 31 link rod 30 is shifted fore and aft thereby tilting tining head 11 and adjusting the ground entry angle of tines 13. Heave arm shaft extends longitudinally across the width of the aerator and so a plurality of heave arms fixed in an array along the length of said heave arm shaft 39 enable tine angle adjustment inputs as set and controlled by tine angle adjustment handle 36 to be imparted in simultaneous synchronization to all the tining heads 11 of the aerator. Referring to Figure 5 and Figure 6, the rearward angle entry of the tines 13 enables said tines to exit the ground imparting reduced heaving action to the soil as indicated by reference numeral 45 in Figure 6. The tine angle adjustment means as described above enables the tine entry angle to be infinitely adjustable through an effective range of approximately 35 degrees. It is particularly advantageous that the mechanism used to set the tine angle accurately maintains this selected angle throughout the plunge cycle. By maintaining this accuracy the tine is assisted in plunging straight into the soil more efficiently with reduced side friction thereby facilitating better penetration and tine lifespan. With reference to Figures 16 to 19, in the present invention tine angle accuracy is maintained by the mechanism incorporating a particular geometrical arrangement which is described as follows. The geometry associated in maintaining the accuracy of tine angle setting comprises two parallel centre lines running in a substantially horizontal plane and two parallel lines running in a substantially vertical plane. The horizontal parallel centrelines, which are shown as dashed lines in Figures 16 to 19, run between pivot point 38 and pivot point 11A through tine arm 10 and between pivot point 3OB and pivot point 3OA through link rod 30, respectively. The parallel vertical centrelines run between pivot point 38 and pivot point 3OB through angled bracket 31 and between pivot point 11A and pivot point 3OA through tining head 11 , respectively. The respective parallel centrelines of each pairing remain parallel throughout the tine angle adjustment range and similarly throughout the 360 degree revolution of crank 8 thereby maintaining the selected tine plunge angle setting throughout the plunge cycle. A range of tines can be fitted to the turf aerator machine for various effects on different turf surfaces. As these tines can vary greatly in thickness and length it is advantageous to be able to adjust the pressure exerted by heave spring 33 and so ultimately to the tines. This is achieved by tightening or loosening a heave spring pressure adjuster bolt 33c which runs through the said: heave spring and screws into the upper end of the heave rod 32. The location of the said heave spring adjuster bolt is easily accessible by the operator at the top of the machine and an indicator scale is also provided (not shown) to enable the correct and equalized pressure to be exerted on each of the tining heads.

As described previously, the tines must be allowed to pivot rearwards to enable the turf aerator to continue in forward motion while the tines are in the ground. As the resultant pivoting of the tines causes the ground to heave as indicated by reference numerals 43 (Figure 4a), 46 (Figure 4b) and 45 (Figure 6), the tine angle is often referred to as the heave angle. With reference to Figure 20, in accordance with the invention there is provided a modified arrangement whereby angling of the tine can be accommodated by transmitting the pivoting force of the tines 13 via link rod 30 and angled bracket 31 to compress an adjustable spring damper 103. In this arrangement there is provided an adjustable spring damper 103 which is mounted at its upper 105 and lower 106 pivot points to heave arm 34 and angled bracket 31, respectively. In this modified arrangement tine angle (i.e. heave) adjustment inputs as set and controlled by tine angle adjustment handle 36 are imparted in simultaneous synchronization to all the tining heads 11 of the aerator via tine angle adjustment screw 35 and screw pivot nut 37 substantially as described before. However, in this arrangement, angled bracket 30 is reversed so that the action of the tines being pulled backwards while they are in the ground imparts a compressive push rather than a pull to adjustable spring damper 103. In this arrangement rotation of adjustment handle 36 angle raises or lowers upper pivot point 105 and lower pivot point 106, respectively, thereby effectively adjusting the tine angle via angled bracket 31 and link rod 30. With this arrangement it is then possible to employ readily available conventional spring damper units having adjustable spring and damper settings which in turn conveniently enabling a turf aerator to be easily and economically tailored to suit all ground conditions. A heave adjustment locking lever 107 provided on adjustment handle 36 or on the tine angle adjustment screw 35 at a location proximate adjustment handle 36 enables the user of the aerator to both adjust the tine angle (heave) and to lock it at the desired tine angle setting. An electrically operated power ram can be incorporated to replace the tine-angle adjuster handle 36 and/or locking lever enabling the operator to adjust the tine angle (heave) from the tractor seat. A threaded adjustment means 104 provided on each adjustable spring damper 103 provides means for individually adjusting or fine tuning individual dampers. Threaded adjustment means 104 allows the distance between the spring damper upper pivot (105) and the spring damper lower pivot (106) to be extended or shortened so that any physical variations between the dampers (e.g. as a result of wear or other factors) can be compensated thereby ensuring that all the tining heads, and thus all the tines, are at the exactly same angle or as near as possible thereto.

Referring now to Figure 13 and Figure 14, in accordance with the invention there is also provided a mechanism for manually setting the depth of tine ground penetration which is achieved by adjusting ground roller 2 upwards or downwards with respect to the aerator chassis 1. When the aerator is lowered and raised to and from an operational position while mounted to a tractor by means of the linkage system comprising upper and lower linkage points 3 and 4, ground roller 2 is placed onto and lifted from the ground, respectively. As aerator is lowered, ground roller 2 comes into contact with the turf surface 21 whereby it substantially supports the weight of the turf aerator. Ground roller 2 is attached at both ends of its axle by means of bearings which are fixed to the bottom of ground roller legs 71 which are located towards opposing sides of the aerator chassis 1. Each ground roller leg 71 is pivotally connected at its upper end 71 A to depth cross beam 70. Spaced apart slide-blocks or similar suitable guides 72 which are provided on the chassis support each ground roller leg 2 at a position along the leg intermediate upper end 71 A and ground roller 2. Guides 72, which are arranged at each side of a respective leg 71 , maintain said roller legs 71 in a substantially upright orientation and prevent movement other than that in a vertical direction. Depth cross beam 70 extends across the width of the aerator machine about which it is rotatably mounted at each end at pivot points 7OA. A swivel nut 75 pivotally connected to the lower end of a depth adjusting bracket 73 that is attached at its upper end to the depth cross beam 70 provides means by which said cross beam is rotated and roller 2 thereby raised and lowered. Tine penetration depth is manually set by turning a depth-adjusting handle 76 which rotates depth adjusting screw 74 thereby moving pivot nut 75 fore or aft which in turn causes depth adjusting bracket 73 to rotate and depth cross beam to swivel about pivot point 7OA. By swivelling depth cross beam 70 about its mounting 7OA raising and lowering the machine from the grass surface 21 to achieve maximum to minimum depth as shown in figures 13 and 14 is thereby effected. The tining depth can be adjusted when the machined is raised from a working position and for ease of adjustment a support spring plunger 77 is incorporated between ground roller 2 and the aerator chassis 1 , the support spring plunger being pivotally connected at its upper end and lower ends to depth cross beam 70 and aerator chassis 1 , respectively. In use, support spring plunger supports the weight of the ground roller 2 thereby relieving pressure on the depth adjusting screw 74 and making the depth adjusting handle 76 easier to turn.

During operation of the turf aerator in compacted or variably compacted surfaces, particularly where maximum tine penetration depth is desired, the turf aerator will often be set to a penetration depth setting which is in excess of the maximum depth to which the aerator is actually capable of penetrating. In such instances ground roller 2 will lift off the ground and the turf aerator will effectively be 'dancing' on its tines. In this event the machine becomes unstable and additional, excessive stresses are placed on the machine, the tines and the operator. It is therefore desirable to maintain a certain degree of roller pressure on the ground at all times during operation. In a further embodiment of the depth setting mechanism described previously and shown in Figure 13 and Figure 14, there is provided an automatic depth control systems as shown in by way of example in Figure 15 and Figure 22. In Figure 15, an electric ram 80 suitable for operating off the tractor electrical circuit is installed to the aerator in a similar manner as the support spring plunger 77 of Figures 13 and 14. The electrically powered ram 80 linkage further comprises a load sensing switch 81 at its upper end which is in rolling contact with depth cross beam 70. The ground roller weight sensor switch 81 is double-acting with twin circuitry and in conjunction with the roller depth sensor spring 82 provides the ground roller electric ram with forward and reverse current to adjust the ground roller upwardly and downwardly according to turf conditions to maintain a specific pressure between said ground roller and the turf surface 21 thus maintaining maximum tine penetration with maximum aerator stability. In Figure 22, an electric ram 80 suitable for operating off the tractor electrical circuit is attached at its lower end to the aerator chassis at pivotal connection 80B and at its upper end at the pivotal connection 80A, which links it to depth cross beam 70 via linking roller leg 71. Load sensor switch 81 is also provided at pivotal connection 8OA and it is activated, via load sensor spring 82, by roller 2 moving in or out of contact with the ground 21. Load sensor switch 81 is double acting and is connected with twin circuitry to provide the electric ram with forward and reverse current to adjust the ground roller 2 upwardly and downwardly according to turf conditions to maintain a specific pressure between said ground roller and the turf surface 21 thus maintaining maximum tine penetration with maximum aerator stability.

When the aerator is set to penetrate less than full depth, an override switch prevents the automatic depth control from adjusting the roller beyond that set depth.

When using finer tines, particularly on fine turf surfaces, it is desirable to maintain a constant penetration depth. This is quite often difficult to achieve especially on rolling terrain such as golf courses or the like. In these instances a problem exists in that the tines 13 are spaced apart from the ground roller 2 and so when the tractor is moving up and down inclines or over uneven and rolling terrain the aerator chassis 1 is variously tilted at forward and backward angles relative to the ground surface thereby constantly altering the depth of tine penetration. With reference to Figure 15 and Figure 22, a ground roller adjusting sensor switch 84 having an adjusting sensor rod 83 which extends substantially outwardly and rearwards from the sensor switch and which has a curved portion at its terminal end is fixed to the ground roller leg 71. In use, the curved terminal portion of sensor rod 83 rests in a skid-like manner on the turf surface 21 proximate or alongside tines 13 when the aerator machine is lowered into an operational position with the ground roller in contact with the ground. The ground roller depth sensor switch is double acting with twin circuitry to provide forward and reverse current to the ground roller adjusting electric ram. The ground roller adjusting sensor rod 83 detects any forward or backward tilt of the chassis relative to the turf surface and adjusts the electric ram up or down a proportional amount to maintain a constant depth of tine penetration.

Alternatively, the depth setting can be adjusted up or down by an operator from the tractor driver compartment via a cable or cordless remote control or similar communication means having suitable switching to provide the ground roller adjusting electric ram 80 with forward and reverse current in order to raise or lower the ground roller. The automatic ground roller weight and depth sensor systems can also be activated or de-activated by the operator remotely. To prevent the automatic depth control from lowering the roller when the machine is lifted from the ground by the tractor or driving vehicle's three point linkage in order to raise it to an out of work position, load sensor switch 81 is incorporated at the top link connection point. The top link is subjected to a tension force when lifting the machine and remains in compression when the roller is on the ground and when the roller is lifted from the ground by the tines encountering a hard surface. Load sensor switch 81 is thus able to detect the difference between the different states and so it is operable to disable the automatic depth control in order to prevent the ground roller from being adjusted downwardly when the turf aerator is raised by the operator, The power to operate the ground roller can also be provided by hydraulic rams with the electric circuitry operating solenoid hydraulic control valves.

It is thought that the present invention and its advantages will be understood from the foregoing description and it will be apparent that various changes may be made thereto without departing from the scope of the invention as defined in the appended claims, the forms hereinbefore described being merely preferred or exemplary embodiments thereof. For example it is envisaged that the turf aerator in accordance with the invention and as described herein can be produced in singular or multiple crank modules to provide turf aerators in a variety of widths of tractor mounting including, but not limited to, self propelled ride-on or pedestrian operated turf aerator machines.

Claims

1. A turf aerator apparatus adapted for releasable engagement with a tractor, the turf aerator apparatus comprising drive means which drives one or more cranks which are arranged in an array comprising a crank-set or crank module, the or each crank-set or crank module being adapted to drive tines or other ground penetrating tools into the ground wherein the or each crank-set is provided with an independent shock absorbing crank driving means.

2. A turf aerator apparatus as claimed in Claim 1, wherein the independent shock absorbing crank drive means provided on each crank-set or crank module comprises a crank, a drive sprocket, a crank sprocket and a suspension sprocket, the crank being bearing mounted to the turf aerator chassis and being chain driven by drive sprocket.

3. A turf aerator apparatus as claimed in Claim 2, wherein the drive sprocket rotates in a clockwise direction so that the chain moves in a clockwise direction about the crank sprocket and the suspension sprocket, the suspension sprocket being located on the drive side of said drive sprocket.

4. A turf aerator apparatus as claimed in Claim 3, wherein tension in the drive chain is equal on respective driving (lower) and non-driving (upper) sides of the drive and crank sprockets during normal operating conditions thereby eliminating backlash in the crank drive mechanism.

5. A turf aerator apparatus as claimed in any one of claims 2 to 4, wherein the drive sprocket pulls the drive chain around the suspension sprocket from below.

6. A turf aerator apparatus as claimed in Claim 5, wherein the suspension sprocket is rotatably mounted to a suspension arm, said suspension arm being pivotally mounted at its lower end about a mounting pivot which is located on the chassis proximate the drive sprocket.

7. A turf aerator apparatus as claimed in Claim 6, wherein an upper free end of the suspension arm distal from the mounting pivot is provided with a spring damping means which connects between the suspension arm and a mounting point provided at an upper part of the chassis.

8. A turf aerator apparatus as claimed in Claim 7, wherein the mounting point comprises an adjustable pivot connection point which enables a precise amount of compression to be applied to the spring damping means so that the suspension arm applies a desired exact tension to the crank drive chain via the suspension sprocket.

9. A turf aerator apparatus as claimed in one of the preceding claims, wherein rotary motion of the crank moves a connecting rod and a tining head in upward and downward reciprocating motion so that tines mounted to the tining head are repeatedly plunged through, and removed from, the ground surface and the subsoil.

10. A turf aerator apparatus as claimed in Claim 9, wherein lateral movement of the crank, connecting rod and tining head assembly during reciprocating motion is restrained by a tining arm which is pivotally connected between the turf aerator chassis and the tining head.

11. A turf aerator apparatus as claimed in any one of claims 7 to 10, wherein tension in the drive chain will exceed a pre-set amount as determined by adjustment of the spring damper when a stone or similar ground inclusion is encountered by the tines of the turf aerator as they plunge into the ground.

12. A turf aerator apparatus as claimed in Claim 11 , wherein increased tension in the drive chain causes the suspension sprocket to be pulled upwardly thus causing suspension arm to rotate upwardly about the suspension arm pivot and thereby compressing the spring damping means.

13. A turf aerator apparatus as claimed in Claim 12, wherein upward motion of the suspension sprocket moves said sprocket towards a notional centreline extending between the centres of the respective drive and crank sprockets thereby effectively shortening the length of the drive chain on its lower driving side so that the crank sprocket may slow or stop momentarily in order for the aerator apparatus to clear a ground inclusion.

14. A turf aerator apparatus as claimed in any one of claims 2 to 13, wherein chain retaining rollers are provided to prevent the drive chain from rising off or jumping the drive and/or crank sprockets as slack gathers at the top non-driving side of the chain between said drive and crank sprockets.

15. A turf aerator apparatus as claimed in Claim 12, wherein each chain retaining roller is located on centreline projecting substantially orthogonal to a centreline running between the drive sprocket and the crank sprocket, each roller arranged tangentially to said drive chain thereby preventing it from rising off or jumping said sprockets.

16. A turf aerator apparatus as claimed in any one of claims 7 to 14, wherein there is provided a compensation means to set and maintain a desired tension in the drive chain in order to compensate for stretch or wear in said drive chain, the compensation means comprising an indicator means and an adjuster bracket, the indicator means being adapted to indicate when adjustment of chain tension is required and when the correct tension is set.

17. A turf aerator apparatus as claimed in Claim 16, wherein the indicator means comprises a measuring means which measures the distance between the respective ends of the suspension spring damper and wherein the adjuster bracket enables that distance to be altered.

18. A turf aerator apparatus as claimed in Claim 17, wherein the measuring means comprises telescopic indicator rod and a sleeve, the telescopic rod and sleeve being pivotally connected at either end of the suspension spring damper at lower connection point and upper connection points, respectively, the relative distance between the the lower end of sleeve and the upper end of the indicator rod being indicative of the adjustment required on the spring damper.

19. A turf aerator apparatus as claimed in Claim 17, wherein the adjuster bracket is provided with upper and lower lock nuts provided on either side of an adjuster mounting plate whereby loosening the upper lock nut and tightening the lower lock nut allows causes that suspension spring damper to compress.

20. A turf aerator apparatus as claimed in any one of the preceding claims, wherein the turf aerator is provided with means for enabling the tining head to pivot rearwardly to enable the turf aerator to continue in forward motion as the tines exit the ground and means for controlling the pivot angle of the tining heads of the apparatus so that the degree of heave imparted to the ground and subsoil by said apparatus can be adjusted.

21. A turf aerator apparatus as claimed in Claim 20, wherein the tining head pivot means comprises a heave rod or spring damper, link rod and angled bracket, the angled bracket being pivotally positioned intermediate the tining head and the heave rod and the tining head being pivotally connected to the angled bracket by the link rod.

22. A turf aerator apparatus as claimed in Claim 21 , wherein the heave rod comprises spring damping means or is a spring damper unit.

23. A turf aerator apparatus as claimed in Claim 22, wherein the pivoting motion of the tining head as the tines exit the ground pushes the link rod thereby causing angled bracket to pivot thus imparting compressive force on the heave rod spring damping means or the spring damper unit.

24. A turf aerator apparatus as claimed in Claim 23, wherein notional centrelines extending between the respective pivoting mounting points of the tining head, link rod and angled bracket define three sides of a parallelogram.

25. A turf aerator apparatus as claimed in any one of claim 21 to claim 24, wherein the means for controlling the pivot angle of a tining head of the apparatus so that the degree of heave imparted to the ground and subsoil by said apparatus can be adjusted, comprises a heave arm which is connected at its respective ends between an adjustment screw and the spring damping means, the heave arm being further mounted to a rotatable heave arm shaft so that rotation of the adjustment screw causes the heave arm shaft to pivot and the heave arm to tilt thus moving the heave rod or the spring damper unit and thereby change the pivot angle of a tining head.

26. A turf aerator apparatus as claimed in Claim 25, wherein the heave arm is substantially L-shaped.

27. A turf aerator apparatus as claimed in Claim 26, wherein the rotatable heave arm shaft extends longitudinally across the width of the aerator so that a plurality of heave arms can be along the length of said heave arm shaft thereby enabling tine angle adjustment inputs as from the adjustment screw to be imparted in simultaneous synchronization to all the tining heads of the aerator.

28. A turf aerator apparatus as claimed in Claim 27, wherein the adjustment screw is provided with locking means so that so that a desired tine angle setting can be maintained.

29. A turf aerator apparatus as claimed in any one of claims 25 to 28, wherein the adjustment screw is rotated by an adjustment handle.

30. A turf aerator apparatus as claimed in Claim 29, wherein the adjustment handle is electrically operated by a power ram.

31. A turf aerator apparatus as claimed in any of the preceding claims, wherein a means for manually adjusting tine penetration depth is provided, the means comprising a ground roller which can be raised and lowering with respect to the turf aerator chassis, the means further comprising a depth cross beam which is pivotally mounted to the chassis, the depth cross beam being manually operable by a handle so as to raise and lower ground roller legs to which the cross beam is pivotally connected and the ground roller is mounted.

32. A turf aerator apparatus as claimed in Claim 31 , wherein the depth cross beam extends across the width of the aerator machine about which it is rotatably mounted at each end.

33. A turf aerator apparatus as claimed in Claim 32, wherein the depth cross beam is provided with a depth adjusting bracket that is attached at its upper end to said depth cross beam, the adjusting bracket being provided with a swivel nut that is connected to the handle by a screw so that rotation of said handle causes the depth adjusting bracket to rotate and depth cross beam to swivel about its mountings thereby raising or lowering the ground roller legs and thus the apparatus.

34. A turf aerator apparatus as claimed in any one of claims 31 to 33 , wherein each ground roller leg is maintained in a substantially upright orientation by spaced apart slide-blocks or similar suitable guides which are provided on the turf aerator.

35. A turf aerator apparatus as claimed in Claim 34, wherein the slide-blocks are arranged at a position on the ground roller legs intermediate the upper end of the leg and the ground roller end of the leg.

36. A turf aerator apparatus as claimed in any one of claims 31 to 35, wherein there is provided a support spring plunger that is incorporated between the ground roller and the aerator chassis, the support spring plunger being pivotally connected at its upper end and lower end to the depth cross beam and aerator chassis, respectively, the support spring plunger acting to support the weight of the ground roller thereby relieving pressure on the depth adjusting screw and allowing the depth adjusting handle to be easily turned.

37. A turf aerator apparatus as claimed in any one of claims 1 to 30, wherein a means for automatically adjusting the tine penetration depth by raising and lowering a ground roller with respect to a turf aerator chassis is provided , the means comprising a depth cross beam which is pivotally mounted to the chassis, the depth cross beam being operable by electrically operated ram comprising a load sensing switch at its upper end which is in rolling contact with said depth cross beam, a ground roller weight sensor switch, and a roller depth sensor spring arranged so as to adjust the ground roller upwardly and downwardly according to turf conditions to maintain a specific pressure between said ground roller and the turf surface thus maintaining maximum tine penetration with maximum aerator stability.

38. A turf aerator apparatus as claimed in Claim 37, wherein an override switch is provided to prevent the automatic depth control means from adjusting the ground roller beyond that set depth when the aerator is set to penetrate less than full depth.

39. A turf aerator apparatus as claimed in Claim 37 or Claim 38, wherein control means to maintain constant tine penetration depth is provided, the means comprising a ground roller adjusting sensor switch provided on the ground roller leg and which controls the electrically operated ram, the adjusting switch further comprising a sensor rod which extends rearwards from said sensor switch,

40. A turf aerator apparatus as claimed in Claim 39, wherein a terminal portion of adjusting sensor rod contacts the ground or turf surface proximate or alongside the tines when the aerator machine is lowered into an operational position with the ground roller in contact with the ground.

41. A turf aerator apparatus as claimed in Claim 39 or Claim 40, wherein the ground roller adjusting sensor rod detects any forward or backward tilt of the aerator chassis relative to the surface of the ground, and via the sensor switch, adjusts the electric ram so that the ground roller leg is moved a proportional amount to maintain a constant depth of tine penetration.

42. A turf aerator apparatus as claimed in any one of claims 39 to 41 , wherein the sensor rod has a curved terminal portion and in use rests on the ground in a skid-like manner.

43. A turf aerator apparatus as claimed in any one of the preceding claims, wherein the apparatus further comprises a tine holder suitable for mounting to a tining head, the tine holder adapted to hold a plurality of tines in releasable engagement and comprising a body portion and a plurality of movably mounted clamp caps which are held loosely against said body portion.

44. A turf aerator apparatus as claimed in Claim 43, wherein the body portion of the tine holder comprises a plurality of arcuate recesses which are adapted to cooperate with complementary recesses provided on the clamp caps so as to define a substantially circular aperture through the tine holder when said caps are brought into close proximity with said body portion, the substantially circular apertures being adapted to receive and engage with the upper ends of tines inserted therein.

45. A turf aerator apparatus as claimed in Claim 44, wherein each arcuate recess on the body portion is further provided with a slot which holds an anti-release roll pin that is adapted to engage with a complementary groove formed around the upper end of a tine when said tine is inserted into a substantially circular aperture.

46. A turf aerator apparatus as claimed in Claim 45, wherein a release bolt or bolts which extend from the front to the rear of body portion and through a clamp barrel provides locking means by which the tines are releasably secured to tine holder.

47. A turf aerator apparatus as claimed in Claim 46, wherein each clamp cap is provided with at least one chamfered face, the chamfered face being arranged to contact a clamp barrel.

48. A turf aerator apparatus as claimed in Claim 46, wherein tightening of the release bolt draws the clamp barrel towards the body portion so that said clamp barrel impinges against the chamfered face of a clamp cap, thereby drawing said clamp cap towards said body portion thus tightly securing a tine or tines to the tine holder.

49. A turf aerator apparatus as claimed in Claim 47 or Claim 48, wherein each clamp cap is provided with at least one face which is arranged at an angle which extends rearward from the arcuate recess formed thereon and which in use projects away from the body portion so as to enable said clamp cap to be drawn more tightly around a tine held in the confines of the substantially circular aperture.

50. A turf aerator apparatus as claimed in Claim 49, wherein adjacent clamp caps are drawn towards the body portion by a single release bolt and clamp barrel.

51. A turf aerator apparatus as claimed in Claim 50, wherein each clamp cap is provided with a cut-out section on the at least one chamfered face which enables a release bolt or bolts to pass between caps when arranged adjacent one another.

52. A turf aerator apparatus as claimed in Claim 50, wherein each release bolt is provided a collar having a recess into which the spring bias means is seated, the recess being of sufficient depth so as to fully compress the spring bias means before coming into contact with the body whereupon the release bolt can be tightened firmly in order to clamp a tine or tines with sufficient force so as to prevent movement or slippage but without imparting damage to the said spring bias means.

53. A turf aerator apparatus as herein described with reference to Figures 1 to 6 and 13 to 22 of the accompanying drawings.

54. A tine holder device as herein described with reference to Figures 7 to 12 of the accompanying drawings