GB2491830A - Log Grip for Rotating Log for Cutting - Google Patents

Abstract

A log handling machine comprising a log grip 80 coupled to a support and moveable relative thereto such that a log can be rotated about its longitudinal axis to be presented to a saw blade 6. Two pairs of log grips or toggle clamps may have teeth 82 to cut into the cut surfaces at either end of the log, each pair gripping on one side of the log such that when the log is cut in a plane including the longitudinal axis each portion of the log is held by one pair of grips. The grips may slide around a curved rail 84 to cause rotation of the log and may fold about hinge 88 away from the cut end to release the log after cutting. There may be an alignment section (Figure 3) including supports moveable to raise and lower the end of the log and move the log side to side to align it for gripping. The grips may be shrouded to protect them from debris from the cutting operation. The machine may accurately cut clefts of wood to form items such as wooden shingles or cricket bats.

Description

A Log Handling Machine The present invention relates to a log handling machine. In particular, the present invention relates to a log handling machine for engaging logs so that they may be presented to a saw blade and rotated relative to the saw blade for cutting the log in a plane generally parallel to a longitudinal axis of the log extending along the length of the log between the two cut ends of the log. Particular embodiments of the invention are arranged to align the natural centre of the log relative to the saw blade so that the log may be cut in a plane substantially passing through the natural centre of the log. The machine may be of particular use in the manufacture of cricket bats.

The traditional method of manufacturing cricket bats, known as pod shaving, is labour intensive. Even with the introduction of machines optimised to mass produce cricket bats, certain parts of the process cannot currently be fully automated. The wood used to produce at least the blade of a cricket bat is willow. Specifically a variety of white willow called Salix Alba var Caerulea, more commonly known as Cricket Bat Willow. The blade is formed from a log cut from a section of willow trunk typically 15 to 20 years old. The felled trunk may be cut into logs of the required length, usually 71.1 to 76.2cm (28 to 30 inches) using conventional sawmill techniques which will not be further described. The logs must then be cut into clefts of wood which are approximately the shape of a cricket bat blade. The clefts are air dried for up to a year or kiln dried for 6 to 8 weeks and then further shaped and treated before coupling to a handle.

It is important that the grain of the willow runs along the length of the cricket bat blade to ensure that the blade does not split prematurely. This is ensured by forming the clefts from segments of the cut logs that have their apex at the natural centre of the log. The natural centre of the log is defined by a straight axis extending through the centre of the wood growth rings at each end of the log. It will be appreciated that logs are rarely exactly cylindrical in shape. Furthermore, the natural centre of the log may not be exactly aligned with the geometric centre of the log owing to variable growth rates of different parts of the willow tree including thicker growth in the side of the tree facing the sun, and other natural variation. It may be that the natural centre of the wood, defined as an axis extending through the centre of the wood growth rings at each end of the log, will not pass exactly through the centre of the growth rings at every point along the length of the log.

To ensure that the log segments are cut through the natural centre of a log it is currently necessary to manually align the log with a hydraulic splitting machine or use a mallet and wedges to split the log into two halves. A saw such as a band saw or a circular saw could be used, however this is difficult and time consuming to do due to the size and weight of the logs. The log is initially split into two halves along a plane including the natural centre of the log. Each log half may then be separately aligned to the hydraulic splitting blade to cut individual segments, with each cut aligned to the natural centre of the log. The number of segments formed, and hence the angle subtended at the apex of each segment, is variable according to the circumference of the log which may vary from 121.9cm to 254.0cm (48 inches to 100 inches). Figure 7 schematically illustrates a log 200 in a perspective view showing a first end 202. The first end is marked with dashed lines indicating eight segment lines 204 for splitting the log 200, each segment 206 having its apex at the natural centre 208 of the log 200. First end 202 is shown again in figure 8 in an end view. Typically a log may be cut into between 6 and 12 segments, though a log with a 254.0cm (100 inch) circumference could be split into 20 or more segments. Each segment broadens towards the outside of the log to a sufficient thickness to form a cleft. Each segment requires further cuts to form approximately cricket bat blade shaped clefts. A single cleft 210 is illustrated in figure 9, with the segment 206 from which the cleft 210 is cut shown with dashed lines. In particular one face 212 of the segment (one of the sides extending to the apex of the segment) must be cut with a circular saw to provide a flat surface with the irregularities resulting from the log splitting processes removed. It will be appreciated that this requirement to cut along the segment face is an undesirable additional processing step. While other aspects of cricket bat manufacture may be partially or fully automated, cutting a log into segments to form clefts remains a skilled manual process.

Similar requirements occur in the manufacture of wooden shingles for roofing and similar applications. Wooden shingles are typically formed from thin segments of wood. While the need to align the segments such that their apexes meet at the natural centre of the log is less pronounced than in cricket bat manufacture, doing so increases the strength of the shingles and maximises the number of shingles that can be cut from a single log.

It is an object of embodiments of the present invention to obviate or mitigate one or more of the problems associated with the prior art, whether identified herein or elsewhere.

According to a first aspect of the present invention there is provided a log handling machine comprising: a support; and a log grip coupled to the support and arranged to grip a log; wherein the log grip is arranged to move relative to the support such that a gripped log can be rotated about a log longitudinal axis extending through the log between first and second ends of the log such that the log can be presented to a saw blade to cut the log in a plane including the log longitudinal axis.

An advantage of the first aspect of the present invention is that the log handling machine is able to rotate logs a log longitudinal axis extending through the log between first and second ends of the log without requiring the log to be manually repositioned to change the plane of a cut. If the log longitudinal axis is aligned to the natural centre of the log, this allows the log to be cut into segments each having their apex at the natural centre of the log without manual realignment of the log with the saw blade prior to performing each cut when cutting multiple log segments. This is particularly advantageous in the manufacture of cricket bats and wooden shingles.

The log grip may be arranged to rotate a log about a log longitudinal axis extending through the log between first and second ends of the log such that the log can be presented to a saw blade to cut the log in a first plane including the log longitudinal axis and in a second plane intersecting the first plane at the log longitudinal axis, the second plane extending at an angle relative to the first plane.

The log handling machine may comprise a pair of log grips, each log grip having teeth arranged to bite into a cut surface at opposite ends of a log to grip the log.

The log handling machine may comprise two pairs of log grips arranged to grip the log on opposite sides of the log such that the log can be presented to a saw blade to cut the log into two half logs in a plane including the log longitudinal axis extending between the two pairs of log grips such that each half log is separately gripped by a pair of log grips.

The or each log grip may be coupled to a curved rail extending partially about a machine axis arranged in use to be aligned with the log longitudinal axis such that the or each log grip is arranged to slide around a curved rail to cause the log to rotate about its longitudinal axis.

The or each log grip may be further arranged to move relative to the support such that a log gripped by the or each log grip is fed into a band saw to cut the log in a plane including the log longitudinal axis.

The or each log grip may be arranged to grip a log such that no portion of the log grip extends outside of a triangle having a first corner on the log longitudinal axis, the first corner having an internal angle less than a predetermined angle.

The or each log grip may be arranged to fold away from a cut end of a log to release the log.

The log handling machine may further comprise a log alignment section, the log alignment section comprising a pair of log supports arranged to support a log towards first and second ends of the log, each log support being arranged to raise and lower the end of the log and move the end of the log from side to side in a plane generally perpendicular to the log longitudinal axis.

The log supports may be further arranged to rotate a log about a log longitudinal axis.

The log handling machine may further comprise a log transfer grip is arranged to move relative to the log supports to grip a log supported on the log supports and remove the log from the log supports to a position in which the log can be engaged by the or each log grip.

According to a second aspect of the present invention there is provided a method of handling a log comprising: gripping a log with a log grip coupled to a support; and moving the log grip relative to the support such that the log is rotated about a log longitudinal axis extending through the log between first and second ends of the log such that the log can be presented to a saw blade to cut the log in a plane including the log longitudinal axis.

According to a third aspect of the present invention there is provided a log segment cut from a log by a method comprising: gripping a log with a log grip coupled to a support; moving the log grip relative to the support such that the log is rotated about a log longitudinal axis extending through the log between first and second ends of the log; presenting the log to a saw blade to cut the log in a first plane including the log longitudinal axis; moving a portion of the log retained by the log grip relative to the support such that the log portion is rotated about a log longitudinal axis extending through the log between first and second ends of the log; and presenting the log portion to the saw blade to cut the log in a second plane including the log longitudinal axis, the second plane intersecting the first plane at the log longitudinal axis and extending at an angle relative the first plane.

According to a fourth aspect of the present invention there is provided a cleft of wood formed from a log segment formed according to the above method, the log segment being further processed to form the approximate shape of a cricket bat blade.

According to a fifth aspect of the present invention there is provided a cricket bat formed from a cleft of wood formed according to the above method, the cleft of wood being further shaped to form a cricket bat blade and coupled to a cricket bat handle.

According to a sixth aspect of the present invention there is provided a wooden shingle formed from a log segment formed according to the above method, the log segment being further processed to form a wooden shingle.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates a log handling machine in accordance with an embodiment of the present invention; Figure 2 illustrates in an enlarged view a log feed section of the log handling machine of figure 1 removed from the remainder of the machine; Figure 3 illustrates in an enlarged view a log alignment section of the log handling machine of figure 1 removed from the remainder of the machine; Figure 4 illustrates in an enlarged view a transfer section of the log handling machine of figure 1 removed from the remainder of the machine; Figure 5 illustrates in an enlarged view a log rotation and translation section, a band saw and a log segment removal section of the log handling machine of figure 1 removed from the remainder of the machine; Figure 6 is an end view of the log rotation and translation section in combination with a band saw; Figure 7 schematically illustrates a log marked with segment lines for splitting the log into eight log segments; Figure 8 schematically illustrates and end view of the log of figure 7; and Figure 9 schematically illustrates a cleft of wood for forming a cricket bat cut from a single log segment.

Referring first to figure 1, this presents an overview of a log handling machine in accordance with an embodiment of the present invention. The remaining figures present -7.-enlarged views of particular sections of the log handling machine. The log handling machine generally comprises a log feed section 2, a log alignment section 3, a log transfer section 4, a log rotation and translation section 5, a band saw 6 and a cut segment removal section 7. It will be appreciated that in certain embodiments the log feed section 2, the band saw 6 and the cut segment removal section 7 may be entirely conventional and fall outside of the scope of the log handling machine. In other embodiments all of the component parts may be fully integrated into a single machine.

Each individual section of the log handling machine will be separately described below in connection with figures 2 to 6. However, their broad functions will now be briefly described. The log feed section 2 generally comprises a conveyor belt arranged to supply log sections (not illustrated) to the log handling machine. Log handling machines in accordance with certain embodiments of the present invention may be typically arranged to process logs from 12 1.9cm to 254.0cm (48 inches to 100 inches) in circumference and 7 1.1cm to 76.2cm (28 inches to 30 inches) in length. These correspond to the typical dimensions of logs suitable for forming cricket bat blades. It will be appreciated that in alternative embodiments of the invention, in particular where the log segments are intended for other uses such as making wooden shingles, any size logs may be processed.

The log feed section 2 generally comprises a cage surrounding a conveyor belt arranged to store the logs such that the logs are arranged to be supplied to the log alignment section side on. Logs may be supplied to the log feed section 2 by individually lifting logs or groups of logs into the cage. Alternatively, the log feed section may be arranged to be coupled to conventional saw mill machinery for processing and transporting logs. In certain embodiments the log feed section 2 allows access for operators to manually mark the natural centre of the logs at each end for use in the log alignment section 3, as will be described below in connection with figure 2. Alternatively, this marking may be performed automatically or may not be required. The marking may be done with a pen or paint, or using stickers, or in any other way.

The log alignment section 3 receives individual logs from the log feed section 2 and aligns a log longitudinal axis of each log to a predetermined machine axis before the logs are transferred to the log translation and rotation section 5 via the log transfer section 4. The log longitudinal axis is any axis which extends along the length of the log and intersects both cut end faces of the log. In particular, the log alignment section 3 is arranged to align the natural centre of the logs to the machine axis. That is, the log longitudinal axis may be the natural centre of the log defined as an axis extending between the centres of the growth rings at both ends of the log. The machine axis may be an axis extending through the log alignment section 3, the log translation and rotation section 5 and the blade of the band saw 6. In other embodiments, the machine axis may only be defined relative to the log alignment section 3 and may not extend through the saw blade, if for instance logs are translated sideways between the log alignment section and the band saw. If the natural centre of a log is aligned with the machine axis the log translation and rotation section 5 can feed the log into the band saw such that the log is cut in a plane including the natural centre of the log by translating the log in a straight line parallel to the machine axis. As discussed above, it is typically the case that the natural centre of a log deviates from a straight line along the length of a log. Additionally, for the manufacture of cricket bats and shingles it is acceptable for a cutting plane to be offset slightly from the natural centre of the log. Preferably the log alignment section 3 is arranged to automatically align the natural centre of the log to a machine axis to within a predetermined tolerance at each end of the log. The tolerance may, for instance, be plus or minus 2cm. It will be appreciated that in alternative embodiments the geometry of the machine may be such that a correctly aligned log in the log alignment section 3 cannot be fed into the band saw 6 by simple translation in a single direction. For instance, the band saw may be offset relative to the log alignment section 3 such that a log must be translated in first and second orthogonal directions to be fed into the band saw 6.

The log alignment may be done by aligning marks added to the logs in the log feed section 2 to the machine axis. Alternatively, the marking may be performed in the log alignment section 3 or may not be needed at all (the log alignment being performed with respect to the unmarked centres of the log growth rings). The alignment is performed by raising and lowering each end of the log perpendicularly to the machine axis and moving each end of the log from side to side perpendicularly to the machine axis. Additionally, the log may be rotated in order to position any defects in the log in a desired position relative to the first chosen cutting plane. As noted above, logs are rarely perfect cylinders, and the natural centre rarely passes through the geometric centre of the log. Consequently in order to align the natural centre of the log to the machine axis the outer edge of the log may appear far from aligned with the machine axis.

The log transfer section 4 is arranged to couple to a log which has been correctly aligned in the log alignment section 3 and move the log to a position in which it can be engaged by the log translation and rotation section 5. Specifically, the log transfer section 4 is arranged to travel over the log alignment section 3 and grip the log. The log alignment section 3 can then disengage from the log allowing the log transfer section to remove the log from the log alignment section 3, which is then free to accept another log from the log feed section 2. The log transfer section 4 moves the log to a position in which one half of the log translation and rotation section 5 can grip the log allowing the log transfer section 4 to release the log and move out of the way. The other half of the log translation and rotation section 5 can then grip the log, as will be described below in connection with figure 5.

The log translation and rotation section 5 is arranged to present the log to the saw 6 such that the saw 6 can cut the log in a plane including the natural centre of the log for a correctly aligned log to within a predetermine alignment tolerance. In particular embodiments the saw 6 is a band saw 6 and the log translation and rotation section 5 is arranged to couple to a log such that the log can be moved relative to the stationary band saw 6 to cut the log. In altemative embodiments the log translation and rotation section 5 may be arranged to move the log to a position in which a movcablc saw such as a circular saw can cut the log. The log translation and rotation section 5 is formed in two halves, each half being arranged to separately couple to the log on opposite sides of the log such that as the log is moved relative to the band saw 6 the log is cut down the middle leaving each half of the log separately gripped by the log translation and rotation section 5. One half of the log may then be moved out of the way while the other half of the log is rotated about the natural centre of the log and cut again to form a plurality of segments. Once one half of the log has been fully cut into segments the other half of the log may then be rotated and cut into segments. The cut segment removal section 7 is arranged to catch the log segments as they are cut from each half of the log and remove the segments from the machine. The cut segment removal section may be essentially a conventional conveyor belt.

Referring now to figure 2, this illustrates an enlarged view of the log feed section. The log feed section 2 generally comprises a cage 20 having a floor 22 to support the logs, side bars 24 and roof struts 26. Logs are loaded into the cage 20 at a first end 28 either manually or by machine such that the logs extend across the floor 22 between the side bars 24. The side bars 24 serve to roughly position the logs such that they are side by side along the length of the floor 22. As the logs are previously cut to a standard length the side bars 24 may be positioned to contact the ends of the logs to keep them in position.

Gaps between the side bars 24 allow access for workers to mark the centre of the growth rings at both ends of the logs, where this is required, for aligning the logs in the log alignment section 3. The marking may be any form of visible mark applied to the centre of the growth rings indicating where the natural centre of the log emerges from the ends of the log. For instance the workers may apply a sticker or paint or dye to the centre of the growth rings.

The floor 22 of the log feed section 2 comprises a conveyor belt which is driven to supply one log at a time to the log alignment section 3. Figure 2 illustrates the log feed section 2 with the conveyor belt removed; however conveyor belt drive roller 30 is visible, driven by motor 32. Logs are fed one at a time into the log alignment section 3 by the conveyor belt under the control of a sensor (not illustrated) for instance a through beam sensor. More generally, the whole log handling machine is controlled by a computer arranged to receive various sensor inputs and to activate a number of actuators and motors. Once a log has been removed from the log alignment section 3 by the log translation and rotation section 5 a new log may be supplied by the log feed section 2 while the first log is still being cut.

This allows a second log to be correctly aligned, as will be described below, while the first log is cut to maximise the throughput of the machine. The computer controls the log alignment section 3 to raise the rollers 44, 48 (described below) to ensure that a log does not drop too far into the log alignment section. The computer then drives the conveyor belt in the log feed section 2 until the sensor indicates that a log has dropped from the end of the conveyor belt into the log alignment section. The conveyor belt is then stopped until the log alignment section is free to receive another log. In certain embodiments a stop gate may be provided to stop further logs rolling from the end of the conveyor belt, however this may not be needed if the conveyor belt is driven sufficiently slowly, especially considering that logs are rarely perfectly round.

Referring to figure 3 this illustrates an enlarged view of the log alignment section 3 separated from the remainder of the machine. The log alignment section 3 generally comprises a pair of moveablc scissor lifts 40. A log supplied from the log feed section 2 is supported at two points along its length generally towards each end of the log by the pair of scissor lifts 40. More specifically, for each scissor lift 40 one upper arm 42 terminates in a smooth roller 44 which freely rotates underneath the log. The other upper arm 46 of each scissor lift 40 terminates in a spiked roller 48 which can be driven by a motor within motor housing 50. The log rests upon the four rollers 44, 48 such that it extends generally parallel to a line extending between the centre pivots 52 of the scissor lifts 40. As noted above, scissor lifts 40 are raised when a log is supplied to the log alignment section 3 in order to minimise the height drop and so avoid damage to the scissor lifts 40, or the risk of a log bouncing out of the scissor lifts 40. Additionally, motor housings 50 further include a clutch mechanism allowing the motor to be disengaged from the spiked rollers 48 to prevent damage to the motors if the log causes the rollers 48 to turn as the log drops in.

The centre of gravity of the log is arranged to lie between the two scissor lifts 40 and between the rollers 44, 48 of each scissor lift 40. Driving spiked rollers 48 in unison causes the log to rotate within the upper forks of the scissor lifts 40 about a log longitudinal axis. It is necessary that there is a driven spiked roller 48 on each scissor lift to ensure that logs can be continuously rotated upon the scissor lifts 40 even in the event of an extremely uneven log which causes the log to lose contact with one spiked roller when rotated to a certain position. Additionally, if only a single spiked roller 48 were driven this could cause a log to twist and fall from the scissor lifts 40. The size of the scissor lifts 40 and rollers 44, 48 are chosen to ensure that for typical diameter logs the log is supported only by the rollers 44, 48 and does not contact the upper arms 42.

Each scissor lift 40 has a pair of lower arms 54, 56 coupled to a carriage 58. Each carriage 58 is coupled to a track 60 on a base plate 62 and arranged to be driven along the track by a motor 64 along a drive axis extending perpendicularly to a machine axis and generally parallel to a line drawn between the pairs of rollers 44, 48. Each carriage 58 is controllable so that each end of the log can be separately moved horizontally in a plane perpendicular to the machine axis.

For each scissor lift 40 a first lower arm 54 is pivotally coupled to the carriage 58 and a second lower arm 56 is pivotally coupled to a slider 66 arranged to slide along the length of the carriage 58 driven by a motor 68. Moving a slider 66 towards the first lower arm 54 causes the scissor lift 40 to raise the rollers 44, 48. Each slider is separately controllable so that each end of the log can be separately moved vertically in a plane perpendicular to the machine axis. Drive of sliders 66 is achieved by motor 68 rotating a threaded rod 70 which passes through a threaded nut 72 towards the bottom end of legs 56. Rotating rod 70 in a first direction causes the scissor lift 40 to rise up, and rotating rod 70 in the opposite direction causes the scissor lift 40 to lower.

It will be understood that appropriate control of the motors 50, 64, 68 allows the log to be rotated about a log longitudinal axis and each end of the log to be independently raised or lowered and moved from side to side in a plane perpendicular to a machine axis. The machine axis runs generally through the pair of scissor lifts, and in a preferred embodiment passes directly through the blade of the band saw 6. More specifically, the natural centre of the log may be aligned to the machine axis (to within a predetermined tolerance) such that the cutting plane of band saw 6 passes through the natural centre of the log. Control of the motors 50, 64, 68 may be performed manually. However, in particularly preferred embodiments of the invention the motors may be controlled automatically to automatically align the log. For instance a vision tracking system (not illustrated) may be provided to automatically identify the centre of the growth rings at either end of the log (either by processing images of the ends of the log or by identifying the marks applied to the ends of the logs in the log feed section). The current location of the centre of the growth rings and the difference between the current position and the machine axis may be processed to provide appropriate control signals to the motors 64, 68 so that they may drive the carriage 58 and slider 66 until the natural centre of the log is aligned with the machine axis. Once a log is correctly aligned it can be passed to the log translation and rotation section 5.

In a specific embodiment the vision tracking system comprises a pair of cameras (not illustrated) position at either end of a log supported on the scissor lifts 40. The cameras may be positioned on moveable anns so that they can be steered clear of the log transfer section 4 as required. Each camera is arranged to measure the offset between the known machine axis and the marked log centre. Motors 64, 68 are provided with appropriate drive signals through a feedback loop arranged to minimise the offset until it falls within an acceptable tolerance. Rotation of the log through driving rollers 48 may not be required to perform this alignment.

After the natural centre of a log is aligned to the machine axis the log may be rotated by driving spiked rollers 48 in order to position any log defects such as splits or knots to a desired rotational position. This rotation may be judged by an operator manually.

Additionally, in certain embodiments of the invention there may be provided a laser projection system at a first end of the log arranged to project one or more lines onto an end of a log indicating the cutting plane. The projected line may be rotated to allow an operator to select the required angle of segments to be cut from the log. The segment angle may be freely varied or may be selected from one of a range of different segment angles.

The selected segment angles are automatically transferred to the log translation and rotation section 5.

Referring now to figure 4, the log transfer section 4 will now be described. The log transfer section 4 is arranged to pass over a log which is supported by the scissor lifts 40 in the log alignment section 3, lower over the log and grip the log to engage the log allowing the log to be lifted out of the scissor lifts 40. The log transfer section 4 can then move the log to a position in which it can be engaged by the log translation and rotation section 5.

More specifically, the log transfer section 4 comprises a pair of log grips 130 arranged to grip a log by each end. Each log grip 130 comprises a fixed plate 131 and a moveable plate 132 having an array of spiked teeth 133 arranged to bite into an end of the log such that the log is positively gripped at each end. Figure 4 shows the teeth 133 covered by wooded safety plates 134 which can be used during maintenance procedures to protect The log grips 130 are coupled to either end of a carriage 136, which is turn is supported on a rail 138 extending generally parallel to the log. The log grips 130 may also be arranged to slide relative to one another along carriage 136 to adjust for variable length logs, though this is not shown in figure 4. To engage a log, the carriage 136 is moved to a position in which the log grips 130 are adjacent to each end of the log (as will be described below).

For each log grip moveable plate 132 is coupled to the fixed plate via an actuator 135 arranged to drive the moveable plate 132 towards the end of the log such that the teeth 133 bite into each end of the log allowing the log to be lifted. To later release the log the actuator 135 is controlled to retract the moveable plate 132 towards the fixed plate so that the teeth 133 pull out of the log. To ensure that the teeth smoothly disengage from the log a release pin 137 is provided in each log grip 130. The release pin 137 can be driven through each moveable plate 132 to push the end of the log off teeth 133.

The rail 138 extends between the log alignment section 3 and the log translation and rotation section 5. When a log has been correctly aligned in the log alignment section 3 the carriage 136 is arranged to slide along the rail 138 over the log alignment section 3 until the carriage is parallel to the log and log grips 130 are above either end of the log. Rail 138 is coupled to pylons 140 by vertical carriages 142 which are arranged to slide up and down within vertical slots 144 within the pylons 140 under the control of pneumatic actuators positioned within the base of each pylon 140 (not visible in figure 4). One the log grips 130 are positioned above either end of the log the rail 138 is lowered until the log grips are adjacent to the ends of the log and each moveable plate 142 can engage the log.

When the log is correctly gripped, the rail 138 is raised to clear the log from the scissors lifts 40 and then carriage 136 is driven along rail 138 to move the log to the log translation and rotation section 5. To release the log to the translation and rotation section 5 it may be necessary to lower the rail 138 again to the correct height.

Referring now to figure 5, the log translation and rotation section 5 will now be described.

Figure 5 also shows the log segment removal section 7, which will be described afterwards. The log translation and rotation section 5 is arranged to grip the log to feed the log into the band saw 6. More specifically, the log translation and rotation section 5 comprises first and second pairs of log grips 80, also referred to as toggle clamps, arranged to grip a log such that the log is supported at generally radially opposite sides of the log.

The log translation and rotation section 5 may also be referred to as ajig for lifting and rotating a log. Each log grip 80 is generally similar to the log grips 130 of the log transfer section 4, except that as illustrated in figure 5 the log grips 80 may be shrouded to prevent debris from the band saw 6 clogging the mechanism. That is, each log grip 80 comprises a fixed plate and a moveable plate (not directly visible in figure 5) with an actuator 81 arranged to move the moveable plate relative to the fixed plate to move teeth 82 mounted on the moveable plate towards and away from the log so that the teeth can bite into an end of the log. As there are two pairs of log grips 80, each side of the log the log is positively gripped at each end by a pair of log grips 80. Referring also to figure 6, this illustrates an end view of the log translation and rotation section 5 in combination with the band saw 6.

It can bc seen that the log grips 80 are positioned on either side of the band saw blade 104.

Gripping the log on both sides in this way prevents the log from twisting. Each log grip 80 is supported on a respective curved rails 84 such that the log grip can travel along the rail 84 at a constant radial distance from the machine axis, and hence a constant radial distance from the centre of the log. To engage a log, each log grip 80 is coupled to a respective curved rail 84 by a hinge 88 so that the log grip 80 may initially be folded back to allow the log grip 80 to clear the log before being folded inwards to the position shown in figures and 6 to engage the end of the log and allow teeth 82 to bite into the wood.

Each pair of curved rails 84 are coupled together by a pair of braces 86. The braces 86 also support a curved shield 87 arranged to be positioned around one half of the log between the log grips 80. The shields 87 serve to contain saw debris to limit the potential for damage to the machinery. The braces 86 for each half of the log translation and rotation section 5 are in turn coupled to and arranged to slide along a pair of rails 90 such that each pair of log grips 80 can be driven generally parallel to the log longitudinal axis. Furthermore, each pair of log grips 80 may be separately driven along their associated pair of rails 90.

The process of transferring a log to the log translation and rotation section 5 will now be described. When the log removal section 4 has removed a log from the log alignment section 3 towards the band saw 6 the pair of log grips 80 on the opposite side of the log from the log transfer section 4 can be driven along their associated rails 90 (with the log grips 80 folded out of the way) until the curved rails 82 are positioned at either end of the log. The log grips 80 may then fold inwards to the position shown in figures 5 and 6 allowing the moveable plates within the log grips 80 to actuate such that the teeth bite 82 into the log to securely grip the log. Once the log is gripped by the first pair of log grips 80, the log grips 130 of the log transfer section may be released from the log such that the weight of the log is solely supported by the log grips 80. The log transfer section 4 may then be raised up such that log grips 130 clear the log and driven out of the way of the log translation and rotation section 5. The second pair of log grips 80 can be driven along their associated rails 90 (with the log grips 80 folded out of the way) until the curved rails 82 are positioned at either end of the log. The log grips 80 may then fold inwards to the position shown in figures 5 and 6 to securely grip the log such that the log is engaged on both sides by a pair of log grips 80 gripping the log at either end of the log.

Once the log has been engaged the log is driven towards the band saw 6 by driving the log grip mechanism along rails 90. The band saw 6 comprises a pair of drive wheels 100, 102 driving blade 104 and driven by motor 106. The machine axis to which the natural centre of the log is aligned in the log alignment section 3 extends through the band saw blade 104.

Driving the carriage rails 86 towards the band saw 6 causes the log to be cut in a first plane which includes the natural centre of the log. The first cut extends between the log grips 80 on either side of the log and splits the log into two half logs which are separately gripped by a log grip 80 at each end.

The curved rails 82 extend partially around the log at a constant radius from the machine axis, and therefore at an approximately constant radius from the natural centre of a log if the log has been correctly aligned to the machine axis. Each log grip 80 is arranged to slide around the respective curved rail 84 under the control of a motor 110. To cut segments from each half log, firstly one half log must be moved out of the way along rails to create space for rotating the other half log. The other half log may then be rotated about the machine axis (and therefore also the natural centre of the log) by driving the pair of log grips 80 in unison around the pair of curved rails 82. The half log is rotated by a predetermined amount (which may have previously been set by an operator, for instance using the laser projection system in the log alignment section) until the log is in the required position to form a cut segment having its apex at the natural centre of the log with the apex subtending a predetermined angle, for instance 30° for forming cricket bat clefts, or smaller for roof shingles. When the half log is correctly rotated it may be driven towards the band saw 6 along rails 90 such that the half log is cut again in a plane which intersects the original cut plane at the natural centre of the log at the predetermined angle.

It will be appreciated that by appropriate rotation of the log grips 80 in both directions about the curved rails 82 a series of log segments may be cut from each half log. To ensure that the maximum amount of segments may be cut from a single log, the log grips are shaped such that they do not extend outside of a predetermined triangle having a first t 5 corner at the natural centre of the log with an interior angle at the first corner smaller than or equal to a predetermined angle, for instance 30°. For the manufacture of cricket bat clefts the portion of the log gripped by a pair log grips may itself be used to form a cleft.

For the manufacture of roof shingles it may be necessary to separately process this portion of the log, or it may be discarded.

Once a first half log has been fully cut into segments, the last segment, which remains gripped by the log grips 80, is released by opening hinges 88. As for the log grips 130 in the log transfer section 4 the log grips 80 may include a release pin to assist removing the teeth 82 from the log. The other half log may then be processed in the same way.

Figures 5 and 6 also illustrate the cut segment removal section 7. As each log segment is cut by the band saw 6 the segment which is not gripped by log grips 80 falls free and lands on a first conveyor belt 120 and is transported away from the band saw 6 to a second conveyor belt 122 which transports the segments away from the machine for further processing to form clefts, which will not be further described here.

While a particular embodiment of the present invention of the present invention described above relates to the manufacture of cricket bats, the present invention is not limited to this.

In particular, embodiments of the present invention may be of particular use in the manufacture of wooden shingles. More generally, the present invention is of particular use whenever there is a requirement to hold a log in position and present the log to a saw to cut the log before rotating the log to form a second cut at an angle to the first cut.

Further modifications to, and applications of, the present invention will be readily apparent to the appropriately skilled person from the teaching herein without departing from the scope of the appended claims.

Claims (16)

1. CLAIMS: 1. A log handling machine comprising: a support; and a log grip coupled to the support and arranged to grip a log; wherein the log grip is arranged to move relative to the support such that a gripped log can be rotated about a log longitudinal axis extending through the log between first and second ends of the log such that the log can be presented to a saw blade to cut the log in a plane including the log longitudinal axis.
2. 2. A log handling machine according to claim 1, wherein the log grip is arranged to rotate a log about a log longitudinal axis extending through the log between first and second ends of the log such that the log can be presented to a saw blade to cut the log in a first plane including the log longitudinal axis and in a second plane intersecting the first plane at the log longitudinal axis, the second plane extending at an angle relative to the first plane.
3. 3. A log handling machine according to claim 1 to claim 2, comprising a pair of log grips, each log grip having teeth arranged to bite into a cut surface at opposite ends of a log to grip the log.
4. 4. A log handling machine according to claim 3, comprising two pairs of log grips arranged to grip the log on opposite sides of the log such that the log can be presented to a saw blade to cut the log into two half logs in a plane including the log longitudinal axis extending between the two pairs of log grips such that each half log is separately gripped by a pair of log grips.
5. 5. A log handling machine according to any one of the preceding claims, wherein the or each log grip is coupled to a curved rail extending partially about a machine axis arranged in use to be aligned with the log longitudinal axis such that the or each log grip is arranged to slide around a curved rail to cause the log to rotate about its longitudinal axis.
6. 6. A log handling machine according to any one of the preceding claims, wherein the or each log grip is further arranged to move relative to the support such that a log gripped by the or each log grip is fed into a band saw to cut the log in a plane including the log longitudinal axis.
7. 7. A log handling machine according to any one of the preceding claims, wherein the or each log grip is arranged to grip a log such that no portion of the log grip extends outside of a triangle having a first corner on the log longitudinal axis, the first corner having an internal angle less than a predetermined angle.
8. 8. A log handling machine according to any one of the preceding claims, wherein the or each log grip is arranged to fold away from a cut end of a log to release the log.
9. 9. A log handling machine according to any one of the preceding claims, further comprising a log alignment section, the log alignment section comprising a pair of log supports arranged to support a log towards first and second ends of the log, each log support being arranged to raise and lower the end of the log and move the end of the log from side to side in a plane generally perpendicular to the log longitudinal axis.
10. 10. A log handling machine according to claim 9, wherein the log supports are further arranged to rotate a log about a log longitudinal axis.
11. 11. A log handling machine according to claim 9 or claim 10, further comprising a log transfer grip is arranged to move relative to the log supports to grip a log supported on the log supports and remove the log from the log supports to a position in which the log can be engaged by the or each log grip.
12. 12. A method of handling a log comprising: gripping a log with a log grip coupled to a support; and moving the log grip relative to the support such that the log is rotated about a log longitudinal axis extending through the log between first and second ends of the log such -21-.that the log can be presented to a saw blade to cut the log in a plane including the log longitudinal axis.
13. 13. A log segment cut from a log by a method comprising: gripping a log with a log grip coupled to a support; moving the log grip relative to the support such that the log is rotated about a log longitudinal axis extending through the log between first and second ends of the log; presenting the log to a saw blade to cut the log in a first plane including the log longitudinal axis; moving a portion of the log retained by the log grip relative to the support such that the log portion is rotated about a log longitudinal axis extending through the log between first and second ends of the log; and presenting the log portion to the saw blade to cut the log in a second plane including the log longitudinal axis, the second plane intersecting the first plane at the log longitudinal axis and extending at an angle relative the first plane.
14. 14. A cleft of wood formed from a log segment according to claim 13, the log segment being further processed to form the approximate shape of a cricket bat blade.
15. 15. A cricket bat formed from a cleft of wood according to claim 14, the cleft of wood being further shaped to form a cricket bat blade and coupled to a cricket bat handle.
16. 16. A wooden shingle formed from a log segment according to claim 13, the log segment being further processed to form a wooden shingle.