WO1991019902A1

WO1991019902A1 - Hydraulic rotary radial piston pumps

Info

Publication number: WO1991019902A1
Application number: PCT/GB1991/000974
Authority: WO
Inventors: Christian Helmut Thoma; George Duncan Mcrae Arnold; Arthur Atholl Blair
Original assignee: Unipat AG
Current assignee: Unipat AG
Priority date: 1990-06-20
Filing date: 1991-06-17
Publication date: 1991-12-26
Anticipated expiration: 1992-12-20

Abstract

Two or more radial piston hydraulic pumps (12, 13) disposed within a simple housing structure, where an input shaft (5) driving through bevel gearing (8, 9, 14) serves to transmit power to the cylinder barrels (12, 13) of the hydraulic pumps (15, 16). At least one cylinder barrel (12, 13) is mounted to rotate on each respective pintle valve (10, 11) each cylinder barrel (12, 13) having a radial cylinder bores (19) each housing a piston (40) operatively connected to a slipper (42) engaging a surrounding annular track ring (43, 44). The pintle valve (10, 11) is provided with a fluid intake duct (30) positioned centrally within the housing, and where the intake duct (30) is unobstructed by any rotating or fixed components of the pump. The intake duct (30) in the end of the pintle is large in size in order to reduce the velocity of the fluid entering the pump and thereby avoid cavitation erosion of the internal pump components. The pintle valves (10, 11) are supported at both ends within the housing so as to allow the pumps to operate under high pressure without problems of hydraulic forces tending to deflect the pintle valve members.

Description

HYDRAULIC ROTARY RADIAL PISTON PUMPS

In the field of hydrostatic equipment, of prime importance is the cost of such equipment. This final cost is dependent on various factors, such as bulk, production quantity and proficient use of low-cost production engineering techniques such as sintered powder metal and aluminium die-casting.

This invention makes a bold attempt at reducing the cost of radial piston hydraulic pumps for such hydrostatic equipment, and is achievable through the use of low cost pump components located within a simple housing structure, and where a single input drive shaft driving through bevel gearing disposed between the hydraulic pump components provides a device both small in bulk size and cost effective as identical hydraulic pump components are used. The device can provide two or more independent and adjustable flow rates from a common source such as a fluid reservoir.

An important feature of this invention is the use of a large intake passage to the radial piston hydraulic pumps with minimum obstruction, and segregation of the chambers containing the rotary elements of the pumps from the chamber containing the intake passage.

The invention furthermore provides solutions in order to overcome certain current difficulties when two or more hydraulic pumps are closely coupled together through more economic use of housing members in order to not only help reduce the velocity of fluid intake into the pumps so avoiding cavitation type problems and the requirement of an auxiliary "charge" pump, but also through the use cf stiff internal structure members, the pumps can operate at higher fluid pressures without suffering from serious component load deflection.

The invention may be performed in various ways and specific embodiments with some possible modifications will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a sectional side elevation through a radial piston hydraulic pumping device according to the invention.

FIG. 2 is an end view across line I-I of FIG. 1.

FIG. 3 is a sectioned side elevation across line II-II of

FIG. 2.

FIG. 4 is a sectional side elevation through a radial piston hydraulic pumping device according to a further embodiment of the invention.

FIG. 5 is a sectional side elevation through a radial piston hydraulic pumping device according to a further embodiment of the invention.

FIG. 6 is a sectional side elevation through a radial piston hydraulic pumping device according to a further embodiment of the invention.

FIG. 7 is a sectional side elevation through a radial piston hydraulic pumping device according to a further embodiment of the invention.

FIG. 8 is a sectional end view through III-III in FIG. 7.

FIG. 9 is a sectional end view through IV-IV in FIG. 7.

FIG. 10 is a sectional end view of the pintle through V-V in FIG. 7.

FIG. 11 is a sectional end view through VI-VI in FIG. 7. FIG. 12 is a sectional side elevation through a radial piston hydraulic pumping device according to a further embodiment of the invention.

FIG. 13 is an end view across the pintle on line VII-VII of FIG. 12.

FIG. 14 is a sectional end view of the pumping device across line VIII-VIII of FIG. 12.

FIG. 15 is an end view across the pintle on line IX-IX of FIG. 12.

FIG. 16 is a modified form of the pumping device of FIG. 12.

The device illustrated in Figures 1 to 3 includes a static housing formed in two co-operating elements 1 and 2, the former supporting a drive shaft 5 via bearings 3. An fluid seal 4 disposed between the bearings 3 prevents fluid from internal chamber 6 from seeping out to the environment.

The drive shaft 5 extends into the internal chamber 6 of the device and is engaged at its inner end 7 by splines a to bevel pinion gear 8.

Pintle valve members 10, 11 of hydraulic pumps 12, 13 are disposed within the housing elements 1 , 2 perpendicular to the rotary axis of the input drive shaft 5. Each pintle 10, 11 is supported respectively between semi-circular channels 27, 28 and 29, 33 in the housing element 1, 2. The pintles 10, 11 extend through respective end walls 67, 68 so as to be rigidly held to the housing elements 1, 2, and with their outer ends exposed. Respective nuts 17 and washers 18 further secure the pintles in place. Bevel gears 9, 14 are rotatably supported on respective pintles 10, 11 and engage with the pinion 8 to connect mechanically the drive shaft 5 to each hydraulic pump 12, 13.

Each pintle valve 10, 11 serves to support, and provides fluid connections, for its respective radial piston hydraulic pump 12, 13 and is preferably manufactured as a casting.

As an alternative, the disclosed form of pintle valve 10, 11 may also be manufactured as a single piece where the ends of the pintle protrude out from the housing elements. However, the pintle as illustrated is generally preferred for reasons of simplicity and ease of manufacture.

In the first embodiment shown in Figures 1 to 3, hydraulic pumps 12, 13, having respective rotary cylinder barrels 15, 16, are mounted to rotate on pintles 10, 11 respectively.

Each cylinder barrel 15, 16 has a number of radial bores 19 each of which communicates with a respective small "radial" port 20 formed in its closed end. The ports 20 communicate in succession with two arcuate shaped ports 21 , 22 formed in the wall 23 of each pintle valve 10, 11, approximately at the midway point and on respective inclined sides of an internal inclined partition wall 24 which serves to divide the hollow interior into two chambers 25, 26 as shown in FIG. 3.

The open inner end of each pintle valve 10, 11 serves as a fluid entry duct 30 for each individual hydraulic pump 12, 13 so that the entry ducts 30 are purposely located centrally within the device. A chamber 25, formed in the interior of the pintle valve, allows for fluid communication between the entry duct 30 and the arcuated shaped port 21. The other arcuated shaped port 22 communicates via chamber 26 to a fluid exit connection 31 positioned at the outer end of each respective pintle valve 10, 11.

A hydraulic fitting 32 is shown screwed into the exit connection 31 so that pipe work can be attached to provide a hydraulic fluid circuit to the apparatus for which the hydraulic pumps provide the source of hydraulic energy.

The cylinder barrels 15, 16 of each hydraulic pump 12, 13 are provided with cylindrical pistons 40 mounted in respective radial bores 19. Each piston 40 has a ball joint 41 at its outer end engaging a slipper 42, which moves around a respective track cam ring 43, 44.

Track rings 43, 44 are arranged to be adjustable in displacement in relation to the centrally located and permanently statically held pintle valves 10, 11, and this is achieved by means of an adjustment rod 45 for each track ring 43, 44 such that movement of the rod 45 results in movement of the track ring 43, 44.

If the track rings 43, 44 are moved such that their centres are in eccentric relationship to the centre of the pintle valve 10, 11, then during rotation of cylinder barrels 15, 16, pistons 40 are urged to move radially inwards and outwards in their respective bores 19, and hence draw fluid from the port 21 in pintles 10, 11, during the suction phase in the piston cycle, and expel the fluid from port 22, during the delivery phase of the piston cycle.

A respective spring 39 is shown acting on each track ring 43, 44 for returning track ring 43, 44 into concentric relationship with pintles 10, 11, when the actuating force on rod 45 is removed.

In this description, rod 45 is manually operated although in practice, any number of control devices can be used to displace the track rings 43, 44 such as hydraulic servo valves or electrical servo motors. Furthermore, for some applications it may be desirable to bleed high pressure oil from the delivery chamber 26 to a purposely provided pressure ram that acts on the track ring 43, 44 to control pump displacement.

The ends 30 of both pintles 10, 11, are fed from a common chamber 71 internally disposed within the housing elements and which is in turn fed from an intake connection 37 on housing member 2 as shown in FIG. 2. A hydraulic fluid fitting 38 is screwed into the intake connection 37 and this connects through pipe work to a fluid reservoir (not shown) from which the hydraulic pumps 12, 13 draw their fluid.

An important feature of the invention is that the inlet duct 30 at the end of each pintle valve 10, 11 should be as large as possible in order to reduce the velocity of the fluid entering at this point, thereby avoiding cavitation erosion of internal components and fluid starvation of either hydraulic pump 12, 13. Usual prior practice for radial piston pumps operating at high rotational speed is to include an auxiliary "charge" or priming pump to fed fluid to the main pump.

Furthermore, this invention has the advantage over those hydraulic pumps known to date in that no obstruction exist in the inlet duct 30 at the end of the pintle valve 10, 11. In prior hydraulic pumps of the radial piston type, the shaft connection to the cylinder barrel imposes a certain degree of restriction at the end of the pintle and therefore would create difficulties for the smooth aspiration of the pump.

In order to maximise the advantages of mounting two or more radial piston hydraulic pumps within a common housing, it is especially important to provide ample area in chamber 71 for smooth fluid transit between the intake connection 37 in housing elements 1, 2, and the inlet ducts 30 at the ends of the pintle valve 10, 11. Furthermore, as inlet ducts 30 of each hydraulic pump 12, 13 oppose each other, and therefore draw fluid from the same source (chamber 71), it is important that chamber 71 be as large as practicable so that the fluid velocity is sufficiently low to avoid fluid starvation of either hydraulic pump.

Economic advantages follow in that only one large diameter suction pipe (rather then two or more) is required to fluidly connect the device to the reservoir, regardless if two, three or four hydraulic pumps are disposed within the device.

Bevel gears 9, 14 are engaged, by means of drive dogs 50, 51, to each respective end face 52, 53 of cylinder barrels 15, 16, and are advantageously supported on bearings 55, 56 directly upon cylindrical surfaces 58, 59 of the pintle valves 10, 11.

It is desirable to provide suitable means to support both the pressure forces imposed on the pintle valves 10, 11 and loading from bevel gearing 8, 9, 14 in such a way that the pintle valves 10, 11 do not bend in cantilever. Each pintle valve 10, 11 is therefore straddle mounted at both its ends in the housing structure in order to provide substantial rigidity to each pintle valve 10, 11 and where the cylinder barrel and bevel gearing is disposed in the centre between such housing support.

As a result of straddle mounting of the pintles 10, 11, no obstruction exists in the area of the intake duct 30 so that efficient aspiration for the hydraulic pumps 12, 13 is achieved. Furthermore, this arrangement allows for fluid segregation of intake chamber 71 from chamber 6 containing the rotatable elements of the hydraulic pumps, and as a result, no contamination from the gears can enter inlet ducts 30.

This feature overcomes the usual weakness of radial piston pumps that utilise a cantilevered mounted pintle valve supported at only one end in the housing, and as a result, the hydraulic pumps in this device can operate at higher pressures, and furthermore provide sufficient support for the bevel gears in order to avoid severe wear and possible failure through poor engagement of the meshing gears when under high load.

As an alternative, cylinder barrels 15, 16 may be formed to include tooth profiles on their end faces. However, this may require higher degrees of accuracy in machining in order to get the gears to mesh correctly, whereas as in the above described embodiment, a degree of misalignment can be accommodated in the drive dog coupling 51, 52 between cylinder barrel 15, 16 and bevel gear 9, 14.

The bevel pinion gear 8, splined at 7 to drive shaft 5, is permanently in mesh with both bevel gears 9, 14.

In order to make the device extremely compact and reduce both the material mass and cost of the housing, the invention teaches the location of bevel gearing at the end face of each cylinder barrel. The high degree of compactness for the device is defined by the centre distance between the hydraulic pumps 12, 13. This centre distance is a function of the diameter of the bevel pinion 8 in addition to the width of both bevel gears 9, 14, and as such is simply a limitation of the bevel gears rather than of the hydraulic pumps.

Any axial forces imposed on the cylinder barrels 15, 16 by the bevel gearing 9, 13 can be overcome and opposed by inserting thrust washers 65, 66 between each cylinder barrel 15, 16 and its respective end wall 67, 68 in housing elements 1, 2.

Intake fluid from a fluid reservoir (not shown) is drawn into the device by the reciprocating action of the pistons 40 within their respective cylinder bores 19. A large bore pipe connected to a hydraulic fitting 38 screwed into the device at intake connection 37 provides a source of fluid which is drawn into a large chamber 71 as shown in Figure. 2, from where the fluid flows into the intake duct 30 located at the inner end of both pintle valves 10, 11.

In each pintle valve 10, 11, the fluid is drawn through chamber 25 to arcuate port 21 and through port 20 in the cylinder bore 19 in the cylinder barrels 15, 16.

During the rotary cycle of the hydraulic pump, the fluid is then expelled through port 22 into chamber 26 in the pintle valve 10, 11 and from here the fluid is fed from the device via exit connection 31 and hydraulic fitting 32.

A simple housing structure will provide a significant cost savings over hydraulic pumps currently manufactured. This may be achieved by providing a housing structure comprising only two, preferably aluminium die-cast, housing elements that attach together on a parting plane that includes the longitudinal axis of the pintle valves. As such, pintle valves 10, 11 are held in position within an extremely stiff package.

An "0" ring type seal 72 is positioned between the housing elements 1, 2 on the parting plane during assembly of the device, seal 72 being compressed when housing elements 1, 2 are bolted together, and thereby acts to prevent fluid from inside chamber 6 from seeping out of the device.

Leakage fluid that collects in chamber 6 during the operation of the device is allowed to return to the fluid reservoir by means of an additional pipe (not shown) or by passing through a low-cost filter (not shown) such as a sintered metal porous type, into intake chamber 71.

FIG. 4 illustrates a further embodiment of the invention where either pump is able to draw fluid from its own independent intake and exit passages. As a result, the output fluid direction of either pump is reversible, and independent in action to its neighbouring pump. Therefore the hydraulic pumps are reversible flow types so as to be able to service two different hydraulic circuits.

A further feature disclosed in this embodiment teaches the use of three housing members comprising the support structure for the pumping device. Although this particular housing form is applicable to all the various embodiments shown in this invention, it will be fully described for just this emboidment.

The central housing element 73 is manufactured so as the provide support for the same drive shaft 5 and pinion 8 elements as shown in FIG. 1. Each end face 74, 75 of the central element 73 mates with a respective cover housing elements 76, 77 in order to encapsulate the radial piston hydraulic pumps 12, 13 within the device.

Therefore, as for the earlier embodiment, the bevel pinion 8 on shaft 5 is engaged to drive respective bevel gears 9, 14. Bevel gears 9, 14 being supported on each respective cylindrical pintle valves 10, 11 and connected to a respective cylinder barrel 15, 16.

In each housing cover element 76, 77, a groove 78 is provided for an "0" ring type seal 79, seals 79 being compressed when housing cover elements 76, 77 are attached to the central housing element 73 in order to prevent hydraulic fluid contained within the device from seeping out into the environment.

The central housing element 73 is preferably manufactured as a casting that includes a support wall 80 for the ends 81, 82 of each respective pintle valves 10, 11. The support wall 80 also includes a further wall 83 set at right-angles to the support wall 80, and wall 83 acts to form an independent and segregated fluid chamber 84, 85 for each respective hydraulic pump 12, 13.

For hydraulic pump 12, the end 81 of pintle valve 10 is fluidly linked via chamber 84 to a hydraulic connection 86 provided in the central housing element 73. For hydraulic pump 13, the end 82 of the pintle valve 11 is fluidly linked via chamber 85 to a hydraulic connection 87 also provided in the central housing member 73.

The system for obtaining a variation in the fluid delivery rate for both hydraulic pumps 12, 13 is the same, and it is advantageous that each pump 12, 13 is operable by its own respective track ring 120, 121. As a result, each track ring 120, 121 can be pivotally displaced about its respective fixed pin 122, 123 in order to independently vary and when required, reverse the fluid flow through the pumps.

Both track ring 120, 121 are identical and each is provided with a hole 124 into which a pivotable shaft 125 is inserted which engages with a projecting arm 126 attached to the control shaft 127.

Projecting arm 126 and pivotable shaft 125 allow movement of the control shaft 127 and translates the rotary movement of an externally operated lever (not shown) attached to the outer end of the control shaft 127 into lateral swinging movement of the track rings 120, 121.

As a result of this movement, the flow rate of each hydraulic pump 12, 13 is altered as the track ring 120, 121 pivots about its respective pin 122, 123, thus varying the eccentric position of the track ring 120, 121 relative to the cylindrical pintle valves 10, 11.

As a result, each hydraulic pumps 12, 13 can provide independent fluid flow in either forward or reverse directions.

For instance, in operation, hydraulic pump 12 could draw its fluid from a fluid reservoir (not shown) through hydraulic connection 86 and via chamber 84 into the open end 81 of the pintle valve 10. The pressurized fluid once through the operating mechanism of the pump 12, is then expelled via chamber 130 linked to hydraulic connection 131 to service any hydraulic circuit that the pump 12 is connected to. By contrast, hydraulic pump 13 can be arranged to draw fluid from the same fluid reservoir as already mentioned, through hydraulic connection 134 (located at the end of the pintle valve 11) that leads to the operating mechanism of the pump 13 via chamber 135. The fluid once through the operating mechanism of the pump 13, is then expelled through the end 82 of the pintle 11 via chamber 85 and flows out of the pump 13 by way of hydraulic connection 87 to provide pressurized fluid to service a further hydraulic circuit.

It should be noted however, that both hydraulic pumps 12, 13 can be controlled so as to draw or expel their fluid through either of their respective hydraulic connections 131, 86, and 134, 87 as desired.

FIG. 5 illustrates a further embodiment of the invention where drive shaft 5 is extended to pass through the device in order to connect with further power driven apparatus such as an auxiliary pump, or pumps.

Each hydraulic pump 12, 13 is provided with a respective pintle valve 140, 141, and each pintle 140, 141 comprises a generally cylindrical member into which two axial passages 142, 143 are machined or cast. Arcuate ports 144, 145 are formed in each pintle 140, 141 which fluidly connect each respective axial passages 142, 143 to each individual cylinders 19 via port 20 during rotation of the cylinder barrel 15, 16.

In this example, as the inner ends of pintles 140, 141 are in close proximity to shaft 159, the inner end of the pintles cannot be used as the intake chamber as shown as 25 in FIG. 3. Therefore axial passage 142, 143 are arranged to connect via a corresponding slot 144, 145 to respective hydraulic connections 148, 149 provided in the end cover housings 150, 151. The open ends of each axial passage 142, 143 is closed by the insertion of a plug 152.

Preferrably pintles 140, 141 are straddle mounted at both ends in the housing. Therefore support of pintles 140, 141 in the housing cover element 150, 151 is achieved by providing a hole 154 into which one end of each respective pintles 140, 141 is inserted for support. The other end of each pintles 140, 141 is supported in the central housing element 156 by being inserted and located in hole 155. As a result of such straddle mounting for the pintles 140, 141, both hydraulic pumps 12, 13 are capable of operating under high pressure without any problem of cantilever deflection.

In operation, fluid can be drawn or expelled from either of the two hydraulic connections 148, 149 in each pump 12, 13, and where the direction of fluid motion depends on the relative position of the track ring 120, 121 to the pintle valve 140, 141 as already described for Figure 5.

The shaft extension 159 shown as an integral part of drive shaft 5, is thereby supported by bearings 3 at one side of the central housing element 156 and by bearing 161 located the opposite side of the central housing element 156. The shaft extension 159 passes through a fluid seal 162 and is shown protruding through the device as shaft 163 to couple with any auxiliary device.

FIG. 6 illustrates a further example of the invention and combines certain features already described and illustrated in the first and fourth embodiments.

In this example, a second pinion gear 92 is included which is splined at 93 to an output drive shaft 94 for the purpose of driving ancillary machinery. Output drive shaft 94 is supported by bearings 96 in the central housing member 97, and a fluid seal 99 is provided to prevent fluid within chamber 100 from escaping.

Second pinion 92 is connected to both bevel gears 9, 14 and as a result, rotation of input shaft 5 and first pinion 8 is transmitted through bevel gears 9, 14 to drive second pinion 92 and output shaft 94. The advantage of this arrangement over that disclosed in FIG. 5 is that fluid entry chamber 25 can be positioned in the ends of the pintle valve 10, 11 in like manner as shown in FIG. 3. Chamber 103 in the central housing element 97 which fluidly connects with the open ends 30 of the pintles 10, 11 is in this example located more centrally in the device.

The fifth embodiment of the invention illustrated in FIGS. 7 to 11 has particular merit when three or more radial piston hydraulic pumps are required within a single pumping device, and where such hydraulic pumps may either comprise twin row radial piston hydraulic pumps or single row multiple pumps or any such combination that may be disposed on each side of the bevel gear driving means.

To the right side of the bevel pinion 8, a double or twin row hydraulic pump 170 is shown. This pump 170 comprises a single cylinder barrel 171 in which are disposed two rows or banks of cylinders 172, 173 for respective pistons groups 174, 175.

The fluid inlet for the device communicates through chamber 71 and passage 178 to the internally exposed end of the pintle valve 179 to connect with two axial suction passages 180, 181 that are provided as shown in FIG. 8. Passages 180, 181 connect with respective arcuate shaped ports 182, 183 formed in the pintle valve 179. Each arcuate shaped port 182, 183 is arranged to serve each respective bank of cylinders 172, 173 by means of radial ports 184, 185 provided in the rotating cylinder barrel 171 and thereby fluid is drawn into the respective banks of cylinder 172, 173.

When the surrounding track ring 187 is positioned in eccentric relationship to the centre of pintle valve 179, the rotation of the cylinder barrel 171 causes the pistons groups 174, 175 to reciprocate and inward piston movement within their respective cylinders 172, 173 causes fluid to be expelled from cylinders 172, 173.

For the first row of cylinders 172, fluid is expelled through radial port 184 formed in the rotating cylinder barrel 171, and passes into arcuate shaped port 188 and passage 190 formed in the pintle valve 179. Axial passage 190 connects through a slot 193 to a hydraulic connection 194 set at right-angles, and formed in housing cover element 196.

In a similar manner for the neighbouring row of cylinders 173, fluid is expelled through radial port 185 formed in the rotating cylinder barrel 171, and passes into arcuate port 189 and passage 191 formed in the pintle valve 179. Axial passage 191 connects with a further passage 192 set at right-angle which directs the fluid to a exit hydraulic connection (not shown) in the housing.

As passages 190, 191 are drilled from opposite ends of the pintle valve 179 and therefore do not meet, plugs 197 are fitted to the ends of each passage 190, 191 in order that all exit fluid is directed to their respective hydraulic connections and not lost through leakage at either end of the pintle valve 179.

Pump 170 therefore acts as a fluid divider as there are respective exit passages 190, 191 for each row of pistons 174, 175 so that two separate hydraulic circuits can be serviced from one single rotating cylinder barrel 171.

Alternatively, there may be four individually adjustable hydraulic pumps located within the device, two pumps being disposed to each side of the bevel pinion.

In order to teach this aspect of the invention, only two hydraulic radial piston pumps 198, 199 are shown to the left side of bevel pinion 8 in FIG. 7 although in practice two further hydraulic pumps may be disposed to the right side of the bevel pinion 8.

In this example, pump 198 contains piston group 211 and pump 199 contains piston group 212.

The configuration for two pumps 198, 199 in tandem or back-to-back arrangement is ideally achieved by coupling a further cylinder barrel 201 to the end face of the first cylinder barrel 200 by means of a drive dog connection 202. The pintle valve 205 is provided with four arcuate shaped ports, 206, 207, 208, 209 and where arcuate ports 206 and 207 communicate with an axial passage 210, and where the end of axial passage 210 opens into passage 178 and duct 71 in the device. As a result, respective piston groups 211, 212 in cylinder barrels 200, 201 are fed from the same fluid intake passage 210. Fluid from the intake duct 71 therefore feeds the piston groups 211, 212 through axial passage 210 which is shown in FIG. 9 to be larger in diameter than the two exit axial passages 215, 216. The larger the fluid entry passage 210 the better the self-aspiration capability of pumps 198, 199.

Arcuate shaped ports 208, 209 formed on the opposite side of the pintle valve 205 are each fed by respective piston groups 211 and 212, and where arcuate port 208 servicing pump 198 communicates through axial exit passage 215 and slot 217 to hydraulic connection 218.

Arcuate port 209 servicing pump 199 communicates through axial exit passage 216 and slot 220 to hydraulic connection 221.

Although the two piston groups 211, 212 can be operated by a common adjustable track ring, it is preferred that each piston group 211, 212 is operated by its own independently adjustable track ring as shown.

FIGS. 12 to 16 disclose further embodiments of the invention that differ in one main respect from all the prior embodiments in that two or more hydraulic pumps are disposed to one side only of bevel pinion gear.

This has advantage in some respect in that the hydraulic pumping device is physically smaller in size as only one cylindrical pintle member and bevel gear is required.

As a result, identical hydraulic pump components are mechanically coupled together and supported on a common cylindrical pintle valve, and the device can provide two or more independent and adjustable flow rates from a common intake line attached to a fluid source such as a reservoir. The device illustrated in FIGS. 12 to 15 comprises a static housing formed in two co-operating elements 230, 231 and where housing elements 230, 231 supports a drive shaft 233 via bearings 234. Drive shaft 233 extends into the internal chamber 237 of the device and is engaged at it inner end by splines 238 to a bevel pinion gear 240.

A cylindrical pintle valve 241 is supported between a semi-circular channel 242, 243 and 244, 245 formed in each respective housing element 230, 231. Therefore pintle valve 241 is shown extending through the end walls in housing elements 230, 231 in order that it can be rigidly held between these elements 230, 231 and where the ends are exposed to the exterior of the device.

A bevel gear 247 rotatably supported on the pintle valve 241 by bearing 248 is arranged to mesh with pinion 240. Gear 247 is connected through drive dogs 250 to the cylinder barrel 251 of the first hydraulic pump 252, and where cylinder barrel 253 of the second hydraulic pump 254 is connected to the first cylinder barrel 251 by means of further drive dogs 256. Cylinder barrels 251, 253 are mounted to rotate on the cylindrical pintle valve 241. As a result, rotation of the input shaft 233 is transmitted through gearing 240, 247 to both first and second cylinder barrels 251, 253 which rotate together in unison.

The open end of pintle valve 241 serves as the inlet opening 260 and is threaded to take a hydraulic pipe fitting which is attached by pipe work to a fluid reservoir. Inlet opening 260 connects with passage 261 within the pintle 241 to service both individual pump units 252, 254. Arcuate ports 263, 264 in the pintle 241 link with passage 261, whereas arcuate ports 266, 267 of each respective pump unit 252, 254 connect with their own axial fluid delivery passages 268, 269 leading to a respective outlet connections 270, 271 each formed in one of the housing elements 230, 231 as shown in FIG. 15.

Each respective outlet connection 270, 271 is threaded to take a hydraulic fitting (not shown) in order that pipe work can be attached to provide a hydraulic fluid circuit to any apparatus for which the hydraulic pumps provide the source of hydraulic energy. For pump unit 252, fluid is delivered along axial passage 268 to radial passage 272 and outlet connection 270. For pump unit 254, fluid is delivered along axial passage 269 to radial passage 273 and threaded end connection 271.

Each hydraulic pump is shown with a respective track ring 275, 276 in order that each hydraulic pump can be independently adjusted in fluid displacement. For some applications, track rings 275, 276 may be formed as one component if, at all times, only identical fluid outputs are required from each pump unit 252, 254. However, the most common requirement is for the hydraulic pumps to be independently operated, and therefore, each pump unit 252, 254 is provided with its own respective control rod actuating means for altering the eccentricity of its respective track ring.

During rotation of cylinder barrel 251 of pump unit 252, when track ring 275 is moved into eccentric relationship with pintle valve 241, and pistons 280 are urged through centrifugal force to move radially outwards in their respective cylinder bores 281, and hence fluid is drawn into their respective cylinders 281 via port 282, arcuate port 263 and intake passage 261. During the delivery phase of the cycle, pistons 280 moves radially inwards in their respective cylinders 281, and fluid contained within cylinders 281 is expelled through port 282 into arcuate port 266 and through axial passage 268, radial passage 272 and connection 270 to exit the device.

Similarly, during rotation of cylinder barrel 253 of pump unit 254, when track ring 276 is moved into eccentric relationship with pintle valve 241, and pistons 284 are urged through centrifugal force to move radially outwards in their respective cylinder bores 285, and hence fluid is drawn into their respective cylinders 285 via port 287, arcuate port 264 and intake passage 261. During the delivery phase of the cycle, pistons 284 moves radially inwards in their respective cylinders 285, and fluid contained within cylinders 285 is expelled through port 287 into arcuate port 267 and through axial passage 269, radial passage 273 and connection 271 to exit the device.

In Fig. 14 spring 289 acts to return track ring 276 to a concentric relationship with pintle valve 241 when the actuating force on rod 290 is removed. An identical spring (not shown) acts in same manner for track ring 275.

The final embodiment shown as FIG. 16 departs from the last embodiment in respect that a single cylinder barrel is required to enable the pumping device to provide two variable and independent hydraulic outputs.

Cylinder barrel 295 is mounted to rotate on the cylindrical pintle valve 241, and is provided with two rows of radial cylinders 296, 297. The first row of cylinders 296 containing pistons 280 comprises the first pump unit 298 and the second row of cylinders 297 containing pistons 284 comprises the second pump unit 299.

Each cylinder 296 of the first pump unit 298 communicates through its respective "radial" port 300 formed in its closed end, and each port 300 communicates in succession with two arcuate shaped ports 253, 266 formed in the wall 301 of the pintle valve 241.

Similarly, each cylinder 297 of the second pump unit 299 communicates through its respective "radial" port 302 formed in its closed end, and each port 302 communicates in succession with two arcuate shaped ports 264, 267 formed in the wall 301 of the pintle valve 241.

Arcuate ports 263, 264 feed from a common intake passage 261 provided in the pintle valve 241, whereas arcuate ports 256, 267 of each respective pump unit 298, 299 connects with their own axial fluid delivery passages 268, 269 in similar manner as illustrated in FIG. 14.

As a result, during rotation of cylinder barrel 295, if each independently operated track ring 275, 276 are positioned eccentrically with respect to the pintle valve 241, respective rows of pistons 280, 284 will draw in fluid from common intake passage 251 in pintle valve 241.

Fluid delivered by the row of pistons 280 of first pump unit 298 passes through port 300 into arcuate port 266. From here the fluid is directed along axial passage 268 and radial passage 272 to connection 270 to exit the device.

Fluid delivered by the row of pistons 284 of second pump unit 299 passes through port 302 into arcuate port 267. From here the fluid is directed along axial passage 269 and radial passage 273 to connection 271 to exit the device.

As the eccentric position of either track ring 275, 276 relative to the pintle valve 241 can be different in respect to the other, this allows the delivery flow rate from either of the pump units 298, 299 to be varied independently to suit circuit requirements.

A further advantage of this invention and applicable to all the embodiments is that by small changes in the ratio in the pinion and bevel gear, (by changing the pitch and number of teeth in the gears) the maximum output delivery of the pump units can be altered without changing the internal components in either of the pump units. As a result, simple ratio changes in the gears will allow the same size of pumps to be used for a larger range of delivery requirements that would otherwise require alternative displacement capacity pumps.

As a result, tooling costs for the pumps is reduced as only a small number of pump capacities needs to be manufactured to provide a range of pumps, and that by comparision, a larger range of gears is relatively inexpensive to manufacture.

The invention may further be adapted for a double hydrostatic transmission located with the simple housing structure of the invention. In this instance, a fixed displacement hydrostatic hydraulic motor would be fluidly coupled to each hydraulic pump. This would provide a very compact double hydrostatic transmission for use, in for instance, a vehicle transmission for tracked vehicles, such as snow-cats, where independent drive to each track is an essential feature for ease of manoeuvrability in tight spaces and for stering over slippery surfaces such as snow and ice. An advantage of the invention is that it can be applied to such vehicle transmissions through the addition of two hydraulic motors and associated fluid valving.

It is to be understood that while we have illustrated and described a number of forms of our invention, it is not to be limited to any specific form or arrangement of parts herein described and shown insofar as such limitations are included in the claims.

Claims

1. A hydrostatic unit including two radial piston machines, each containing a cylinder barrel mounted on a fixed pintle, the barrels being coaxial and longitudinally spaced from each other, and a drive unit comprising a common shaft and gear means disposed generally between the barrels and drivingly engaging respective end faces thereof.

2. A unit as claimed in Claim 1, wherein the gear means includes a bevel gear mounted on the drive shaft and respective bevel gears associated with each cylinder barrel.

3. A unit as claimed in Claim 2, wherein the bevel gears are drivingly engaged to the end faces of the cylinder barrels.

4. A unit as claimed in Claim 2, wherein the bevel gears are formed on the end faces of the cylinder barrel.

5. A unit as claimed in any one of Claims 2 to 4, wherein the bevel gears are rotatably mounted on respective pintles.

6. A unit as claimed in any one of the preceding claims including a pintle for each barrel, the pintles being axially aligned and longitudinally spaced.

7. A unit as claims in any one of the preceding claims including a housing having a first chamber in which the drive unit is disposea and a second chamber constituting a fluid inlet or outlet chamber and wherein the chambers are fluidly sealed one from the other.

8. A hydrostatic unit including two radial piston machines each having a fixed pintle, the pintles are axially aligned and longitudinally spaced, and a housing for enclosing the machines and for supporting each pintle at a pair of axially spaced locations .

9. A unit as claimed in Claim 8, wherein the housing defines a sleeve for supporting the facing ends of the respective pintles and wherein the sleeve is partially open to define a fluid inlet or outlet between the pintle ends.

10. A unit as claimed in Claim 8 and in any one of Claims 1 to 6.

11. A hydrostatic unit including two radial piston machines each having a fixed pintle, the pintles being axially aligned and longitudinally spaced, and a housing for enclosing the machines and for defining a hydraulic inlet between the fixed pintle ends.

12. A unit as claimed in Claim 11, wherein the inlet is unobstructed by any other components of the unit.

13. A unit as claimed in Claim 11 or Claim 12 and in any one of Claims 1 to 10.

14. A hydrostatic unit including two radial piston machines each having a fixed pintle, the pintles being axially aligned and longitudinally spaced and a common housing for the machines and the other components of the unit.

15. A unit as claimed in Claim 14, wherein the housing defines parts of the machines.

16. A unit as claimed in Claim 14 or Claim 15 wherein the housing is split along the pintle axis.

17. A unit as claimed in Claim 14 or Claim 15, wherein the housing includes a central portion and separate lateral portions for enclosing and forming part of the radial machines.

18. A housing as claimed in Claim 17, further including a drive unit contained in the central portion.

19. A housing as claimed in any one of Claims 14 to 18 and in any ones of Claims 1 to 13.

20. A hydrostatic unit including two radial piston machines, each containing a cylinder barrel mounted on a fixed pintle and each having a respective track ring, wherein each barrel has an associated inlet from the pintle disposed such that the flow of fluid, in use, through one inlet is either in generally the opposite direction to the flow through the other or generally in the same direction depending on the intended operational movement of the track rings.

21. A unit as claimed in any one of the preceding claims wherein there are a plurality of radial piston machines on each side cf the drive unit or on each pintle.

22. A unit as claimed in any one of the preceding claims wherein the radial piston machines on respective sides of the drive unit are drivingly engaged to the other.

23. A unit as claimed in Claim 19, wherein the radial piston machine on each side of the drive unit upon each pintle together form a hydrostatic transmission.

24. A unit as claimed in any one of the preceding claims, wherein the radial machines are pumps.

25. A unit as claimed in any one of claims 1 to 18, wherein the radial piston machines are motors.

26. A hydrostatic unit substantially as hereinbefore described with reference to the accompanying drawings.

27. A unit as claimed in claim 8, wherein the housing defines a sleeve for supporting the facing ends of the respective pintles and wherein the sleeve is partially open to define two fluid passages between the pintle ends, each fluid passage serving one pintle end and where the fluid passages are segregated from each other.

28. A hydrostatic unit including two radial piston machines, each containing a cylinder barrel mounted on a fixed pintle, the barrels being coaxial and longitudinally disposed one from the other, means for drivingly engaging one barrel to the other and a drive unit for drivingly engaging the end face of the one barrel to thereby drive both barrels simultaneously.

29. A hydrostatic unit as claimed in Claim 28, wherein the barrels are mounted on a common pintle.

30. A hydrostatic unit as claimed in Claim 28 or Claim 29, wherein the barrels are formed in a single body and a portion of the body intermediate the barrels constitutes the drivingly engaging means.

31. A hydrostatic unit as claimed in any one of the preceding Claims, wherein the drive unit comprises a drive shaft, a bevel pinion gear on the shaft and a bevel gear formed on or drivingly connected to the end face of the one barrel.

32. A hydrostatic unit as claimed in Claim 31, wherein the drive shaft extends generally at right angles to the pintle.

33. A hydrostatic unit as claimed in any one of the preceding Claims, further comprising a housing.

34. A hydrostatic unit as claimed in Claim 33, wherein the housing defines a sleeve for supporting the ends of the pintle and wherein the sleeve is partially open to define a fluid inlet or outlet between the pintle ends.

35. A hydrostatic unit as claimed in Claim 33 or Claim 34, wherein the housing forms part of the machine.

36. A hydrostatic unit as claimed in any one of Claims 33 to 35, wherein the housing is split along the pintle axis.

36. A hydrostatic unit as claimed in any one of the preceding claims, wherein the machines each include a set of cylinders each containing a respective piston and a track ring for determining piston displacement, the track rings being independently variable with respect to the barrels.