GB2374568A

GB2374568A - Clamping device

Info

Publication number: GB2374568A
Application number: GB0108121A
Authority: GB
Inventors: William Hamilton
Original assignee: Coincheck Electronics Ltd
Current assignee: Coincheck Electronics Ltd
Priority date: 2001-03-30
Filing date: 2001-03-30
Publication date: 2002-10-23
Also published as: GB0108121D0

Abstract

A clamp for clamping eg a length of wood or log for use when sawing comprises a fixed jaw 9 secured to a support 8 and a second jaw 12 mounted above the first jaw movable towards the second jaw under its own weight. Jaw 12 may be mounted on a shaft 11 which can slide within a tubular support 8 or jaw 12 may include a tubular member slidable on a vertical post of the support 8. Jaw 12 may be retained in a raised position, eg by a tongue (32 fig 7) and one or more slots (33 fig 7) or by an oversized slidable connection (fig 5), and may be released from the raised position by applying to the first jaw the weight of an item to be clamped, eg by releasing a latch or trigger, which may be in the form of an eccentric cam (14 fig 3). The jaws may have spikes or studs 10, 13 to grip the wood and the support may be mounted on a stand or tripod 1, 2 and 3, on a wall or on a vehicle.

Description

DESCRIPTION "A CLAMPING DEVICE" The present invention relates to a clamping device and, more specifically to a clamping device for securing lengths of timber in such a way as to facilitate sawing thereof.

It is difficult to support long lengths of timber for sawing into short manageable lengths, particularly where the timber in question is logs obtained from felling trees.

Where tree felling is carried out as a commercial enterprise specialised tree felling and cutting apparatus is employed. However, this sort of equipment is not available for those engaged in tree management where, perhaps, a single tree is to be felled or simply pruned by the removal of branches. In these circumstances it is usual either to lay the log to be cut on the ground or to rest the log on a saw horse. Neither of these approaches is entirely satisfactory.

Where the log is cut on the ground there is a tendency for it to move about as the saw passes through it, particularly if the ground is rough and uneven. To prevent this the user might stabilise the log with a hand or foot. In addition, the lie of the log on the ground may cause the two sides of the cut to close together around the saw blade.

Finally, as the saw blade passes through the log it may contact the ground. All of these circumstances are potentially hazardous to the saw operator.

The alternative of using a saw horse raises the log to be cut off the ground and ensures that the problems associated with cutting it on the ground, referred to

hereinabove, are avoided. A saw horse essentially comprises a horizontal beam on four slopping legs. A log to be cut is laid lengthways along the horizontal beam with one end thereof overhanging the beam by the amount which is required to be cut off. After each cut the length of timber is slide up along the beam to allow the next piece to be cut.

A saw horse is ideally suited to cutting relatively short lengths of timber, where the main weight thereof is fully supported on the four slopping legs thereof However, where the length of the timber is such that it overhangs one end the horizontal beam by a considerable amount, the saw horse may become unbalanced and unstable. This applies particularly where the saw horse is used on rough and uneven terrain. Here again the user must stabilise the log with a hand or foot. In these circumstances use of a saw horse is unsafe.

It is an object of the present invention to provide a clamping device for securing a length of timber to be sawn into short lengths which obviates or at least substantially mitigates the disadvantages referred to hereinabove.

It is yet another object of the present invention to provide a clamping device which can be operated single handedly to clamp a length of timber and which, having clamped the timber, leaves both the user's hands free to operate a chain saw.

It is still another object of the present invention to provide a method of clamping a length of timber and sawing into shorter lengths.

According to the first aspect of the present invention there is provided a clamping device for clamping a length of wood to be sawn into two or more shorter lengths comprising support means, a first clamping jaw fixedly carried by the support

means and a second clamping jaw mounted above the first clamping jaw and moveable relative thereto, the second clamping jaw being moveable towards the first clamping jaw under its own weight.

In a preferred embodiment of the present invention the second clamping jaw is fixedly mounted on an upright shaft or post which is slidably received within a vertically extending tubular member carried by the support means. However, as an alternative the second clamping jaw may comprise a tubular member which is slidable on a shaft or post extending vertically from the support means. In use, the second clamping jaw is raised relative to the first clamping jaw to admit one end of a length of timber therebetween and the second clamping jaw is then released to drop it onto the timber located therebetween and clamp it.

Preferably, means are provided for retaining the second clamping jaw in a raised position above the first clamping jaw and the retaining means is released by the application of weight to the first clamping jaw. In use, an operative simply drops one end of the length of timber to be cut onto the first clamping jaw to cause the retaining means to release the second clamping jaw from its raised position. Under its own weight the second clamping jaw drops down onto the said end, securing it in place between the clamping jaws.

Various means may be employed to retain the second clamping jaw in a raised position. In one embodiment of the present invention the slidable connection between the tubular member and the said shaft or post is oversized so that either the tubular member or the shaft may be angled from the vertical as it is raised relative to the other.

It will be understood that in this position the weight of the raised part is supported against the side of the static part. However, by dropping a weight onto the first clamping jaw the raised part is effectively bounced off the supporting surface of the static part and slides downwards under its own weight. Conveniently, the said shaft and the said tubular member define a pair of abutment surfaces which are engageable to support the raised part above the static part.

As an alternative the static part of the clamping device may carry a latch or trigger which engages with the raised part to hold it in the raised position, which latch or trigger is caused to be released by the application of a weight to the first clamping jaw.

In one embodiment of the present invention the latch comprises a tongue which extends from a rearward surface of the first clamping jaw and the first clamping jaw is pivotable between a first position in which the tongue engages in a slot provided in a post or shaft carrying the second clamping jaw and a second disengaged position. It may be convenient to provide more than one slot in the said post or shaft so that the height to which the second clamping jaw is raised and retained above the first clamping jaw can be varied.

In another embodiment of the invention the latch comprises an eccentric cam member which is mounted in a slot in the side wall of the tubular member through which extends the shaft or post carrying the second clamping member. In use the cam member is rotated into engagement with the shaft or post to secure it in a raised position. On dropping a weight onto the first clamping jaw this causes the cam to

bounce out of engagement with the said shaft, thereby allowing the shaft to descend.

In yet another embodiment of the present invention the shaft is at least partially rotatable about a substantially vertical axis relative to the tubular member to cause a pin mounted on an internal surface of the tubular member to engage in a horizontal slot or channel in the shaft, or vice versa. Preferably the said horizontal channel opens into the lower end of a channel which serves to guide the shaft in the tubular member. The guide channel may define a helical portion towards the lower end thereof, immediately before the said horizontal slot, which helical portion allows the shaft and the upper clamping jaw carried thereby to be pivoted about the said vertical axis relative to the lower clamping jaw as it reaches the fully raised position. This allows the upper clamping jaw to be moved to one side relative to the lower jaw and allows unimpeded access to drop a length of timber onto the lower clamping jaw. It will be understood that when the latch mechanism is operated the shaft is guide around by the guide pin moving in the guide channel to bring the upper clamping jaw into position directly above the lower clamping jaw.

Preferably, one or both facing surfaces of the first and second clamping jaws is provided with wood gripping means. Conveniently, the wood gripping means takes the form of short spikes or studs.

The clamp may be supported on the ground by means of a stand. This conveniently takes the form of a tripod. Preferably, one leg of the tripod is longer than the other two and extends in the same direction as the two clamping jaws. As an alternative the clamping device may be permanently sited on a wall or for portability

it may be permanently attached to a vehicle.

In a preferred method of using the clamping device of the present invention the upper clamping jaw is raised relative to the lower clamping jaw and held in position on the latch, a length of timber to be clamped is dropped onto the lower jaw which causes the latch retaining the upper clamping jaw up to be released, thus allowing the upper clamping jaw to descend under its own weight onto the length of timber.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a front view of a clamping device embodying the present invention; Figure 2 shows a side view of the clamping device shown in Figure 1; Figure 3 is a partial sectional view of the latch mechanism of the clamping device shown in Figure 1; Figure 4 shows the clamping jaws of a clamping device according to the present invention using an alternative form of latching mechanism; Figures 5 (a) and (b) each show a sectional view of the latching mechanism of the clamping device shown in Figure 4, the former showing the latch prior to engagement and the latter showing the latch when engaged; Figure 6 shows the clamping jaws of a clamping device according to the present invention using yet another form of latching mechanism; Figure 7 shows a sectional view of the latching mechanism of the clamping device shown in Figure 6 when the latch is engaged;

Figure 8 is a view of the clamping jaws of a clamping device according to the present invention using yet another form of latching mechanism; Figure 9 is a section along lines D-D of the tubular support to which the lower jaw is fixedly mounted; and, Figure 10 is a view of the cylindrical shaft to which the upper jaw is mounted and shows the helical channel therein which serves to guide the shaft as it descends.

Referring to Figures 1 and 2 of the accompanying drawings there is shown a clamping device for clamping a length of timber, typically a branch or trunk of a tree which has been felled and which is required to be sawn up into manageable lengths.

The clamping device may be used with a hand saw, but it is primarily intended for use with a chain saw. As will be readily appreciated safety procedures must always be followed when working with a chain saw. Not least of these is that the workpiece, that is to say the length of timber which is to be cut must be properly secured.

The clamping device comprises a support frame consisting of two outwardly extending legs 1 and 2 and a third longer leg 3 which extends perpendicular to the legs I and 2, and in the direction in which timber extends from the clamping device. As will become apparent hereinafter this arrangement is highly stable and lengths of timber of considerable length can be accommodated within the clamping device before it becomes unstable. Indeed, in practise the length of the leg 3 will be such that any length of timber which would unbalance the clamping device will be too heavy to be lifted manually into it. To facilitate transport and storage of the clamping device when it is not in use, each of the legs 1,2 and 3 is received within a tubular socket 4,5 and 6,

respectively, and releaseably secured therein by means of a removable locking pin 7. Each of the tubular sockets 4,5 and 6 is fixedly secured to an upright tubular member 8 which forms the backbone of the clamping device.

Fixedly secured to the tubular member 8 is an upwardly facing clamping jaw 9.

Being fixedly secured to the tubular member 8 the height above the ground of this jaw 9 is not adjustable. For convenience of use it is set at around waist height, at which height lengths of timber can be lifted onto it without too much difficulty. The upwardly facing surface of this jaw 9 is provided with pointed studs or spikes 10 which help to grip and secure the end of a length of timber dropped onto the jaw 9.

Slidable within the tubular member 8 is a post or shaft 11 which carries a second downwardly facing jaw 12 directly above the jaw 9. To facilitate raising the second jaw 12 a hand grip 16 is provided on its upper surface. The lower surface of this second jaw 12 is, like the jaw 9, provided with studs or spikes 13 which help to grip and secure the end of a length of timber between the jaws 9 and 12.

Referring now also to Figure 3, on the rearward face of the tubular member 8 there is mounted an eccentric locking cam 14 which is pivotable about a horizontal axis by means of a handle 15. The eccentric surface of the cam 14 can be engaged with the post or shaft 11 through a slot in the rearward face of the tubular member 8 to lock the shaft 11 in a raised position within the tubular member 8 by rotating the cam 14 in a clockwise direction as view in Figure 3. This is achieved by the simple expedient of pulling downwards on the handle 15 when the shaft 11 has been raised to the desired height. With the jaws 9 and 12 of the clamping device now held open, as shown in

Figure 2, the device is ready to receive and clamp a length of timber. To this end, one end of the length of timber is dropped onto the lower jaw 9. This has the effect of bouncing the shaft 11 upwardly, which in turn causes the cam 14 to disengage from it. Now with the cam 14 disengaged the shaft 11 is free to slide downwards within the tubular member 8 under the weight of the jaw 12. The cam 14 itself is prevented from rising back into engagement with the shaft under the weight of the handle 15 by the downward descent of the shaft 11 within the tubular member 8. The weight of the upper jaw 12 is such that it descends with some considerable force onto the end of the timber positioned on the lower jaw 9, causing it to be impaled on the spikes 10 and by the spikes 13. Now with the shaft 11 fully descended there is no longer a downward acting force on the cam 14 to prevent it from engaging with the shaft, and under the weight of the handle 15 it rises upwards again to engage with the shaft and secure it in place within the tubular member 8.

Now with a length of timber secured between the jaws 9 and 12 of the clamping device sawing may commence. It will be understood that the length of timber extends from the jaws 9 and 12, substantially parallel to the ground at approximately waist height and in the direction of the longer leg 3. This configuration is very stable on the ground and it is a simple matter for an operator to approach with a chain saw and successively cut short lengths from the length of timber.

Referring now to Figures 4 and 5 (a) and (b) of the accompanying drawings there is shown an alternative form of latch mechanism for use in a clamping device according to the present invention. For ease of illustration the support frame has not been shown

and the same reference numerals have been used to identify those elements of the clamping device which are also to be found in Figures 1,2 and 3.

It will be seen that the rear surface of the shaft 11 defines a downward facing horizontally extending lip 20. As shown in Figure 5 (a), this lip 20 does not impede movement of the shaft 11 within the tubular member 8. However, the lip 20 is engageable with the rear upper edge 21 of the tubular member 8 to retain the shaft 11, and the upper clamping jaw 12 carried thereby, in a raised position. Retention of the lip 20 on the upper edge 21 of the tubular member 8 is assisted by tilting the shaft 11 at a slight angle to the horizontal so that the centre of gravity thereof is shift towards upper edge 21. However, it is to be noted that the width of the lip 20, together with the combined weight of the shaft 11 and the upper clamping jaw 12, ensure that the lip 20 can easily slip of the upper edge 21.

In use the upper clamping jaw 12 is raised relative to the lower clamping jaw 9 by pulling upwards on the hand grip 16 until the lip 20 is above the upper edge 21 of the tubular member 8. The shaft 8 is then tilted backwards and allowed to descend to engage the lip 20 on the upper edge 21. With the clamping jaws 9 and 12 held open a length of timber to be clamped is dropped onto the lower clamping jaw 9. This has the effect of bouncing the shaft 11 in the tubular member 8 which in turn causes the lip 20 to slip off the upper edge 21. The shaft 11 is now free to slide downwards within the tubular member 8 under its own weight.

Referring now to Figures 6 and 7 of the accompanying drawings there is shown yet another form of latching mechanism for use in a clamping device according to the

present invention. Here again for ease of illustration the support frame has not been shown and the same reference numerals have been used to identify those elements of the clamping device which are also to be found in Figures 1,2 and 3. In contrast to the previous embodiments of the present invention described hereinbefore the lower clamping jaw 9 is not rigidly fixed to the tubular member 8, but rather it is supported on a pivot pin 30 between two plates 31 (only one of which is visible). This arrangement allows the lower clamping jaw 9 to rock about the horizontal axis defined by the pivot pin 30, thereby allowing the rear edge of the jaw 9 to move towards and away from the shaft 11. The rear edge of the tubular member 8 defines a tongue 32 which is engageable in a slot 33 in the lower end of the shaft 11 to support the shaft in a raised position relative to the tubular support 8.

In use the jaws of the clamping device are opened by lifting the upper clamping jaw 12 until the tongue 32 engages in the slot 33 and the shaft 11. Now, if the upper clamping jaw 12 is released the shaft 11 and the upper clamping jaw 12 can be supported on the tongue 32 and maintained in this raised position. Here it should be noted that the combined weight of the shaft 11 and the upper clamping jaw 12 acting downwardly on the tongue 32 causes the lower clamping jaw 12 to pivot upwardly and rearwardly towards the shaft 11. With the clamping jaws 9 and 12 held open a length of timber to be clamped is dropped onto the lower clamping jaw 12. The causes the lower clamping jaw 9 to pivot downwardly and away from the shaft 11 which in turn causes the tongue 32 to disengage from the slot 33. With the shaft 11 no longer supported by the tongue 32 it is free to slide downwardly within the tubular member 8

under its own weight, thereby causing the length of timber to be clamped between the two jaws 9 and 12.

Referring now to Figures 8,9 and 10 there is shown yet another latch mechanism for use in a clamping device according to the present invention. Here once again for ease of illustration the support frame has not been shown and the same reference numerals have been used to identify those elements of the clamping device which are also to be found in Figures 1,2 and 3.

In this embodiment of the invention the shaft 11 is cylindrical and is partially rotatable about a substantially vertical axis relative to the tubular member 8. The path followed by the shaft 11 relative to the tubular member 8 is determined by a channel 40 cut in the outer surface of the shaft and a guide pin 41 mounted in the wall of the tubular member 8 which engages in the said channel 40. The upper end of the channel is essentially vertical, but towards the lower end it leads into a curved or helical portion which covers a 90 degree arc around the cylindrical shaft. Finally the curved section ends in a horizontal slot.

In use, when the upper clamping jaw 12 is raised to open the jaws of the clamping device the guide channel 40 serves to turn it through an angle of 90 degrees as it reaches the top of the channel 40 and at the very top of its travel the shaft 11 and the jaw 12 are supported in the raised position by the guide pin 41 within the horizontal slot. With the upper clamping jaw 12 lying to one side of the lower clamping jaw 9 an operator is able to drop a length of timber onto the lower jaw 12 without having to guide it past the upper jaw 9. Now the jaws may be closed by rotating the upper jaw

12 to disengage the guide pin 41 from the horizontal slot at the end of the channel 40. Immediately the guide pin 41 is disengaged from the slot the shaft is free to descend under its own weight. As it does so the guide pin 41 acting in the channel 40 causes the shaft to rotate to bring the upper jaw 12 back into alignment with the lower jaw.

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Claims

1. A clamp for clamping a length of wood to be sawn into two or more shorter lengths comprising support means, a first clamping jaw fixedly carried by the support means and a second clamping jaw mounted above the first clamping jaw and moveable relative thereto, the second clamping jaw being moveable towards the first clamping jaw under its own weight.

2. A clamp according to claim 1, wherein the second clamping jaw is fixedly mounted on an upright shaft or post which is slidably received within a vertically extending tubular member carried by the support means.

3. A clamp according to claim 1, wherein the second clamping jaw comprises a tubular member which is slidable on a shaft or post extending vertically from the support means.

4. A clamp according to claim 1,2 or 3, wherein means are provided for retaining the second clamping jaw in a raised position above the first clamping jaw and the retaining means is released by the application of weight to the first clamping jaw.

5. A clamp according to claim 4, wherein the slidable connection between the tubular member and the said shaft or post is oversized so that either the tubular member or the shaft may be angled from the vertical as it is raised relative to the other.

6. A clamp according to claim 5, wherein the said shaft and the said tubular member define a pair of abutment surfaces which are engageable to support the raised part above the static part.

7. A clamp according to claim 4, wherein the static part of the clamping device carries a latch or trigger which engages with the raised part to hold it in the raised position, which latch or trigger is caused to be released by the application of a weight to the first clamping jaw.

8. A clamp according to claim 7, wherein the latch comprises a tongue which extends from a rearward surface of the first clamping jaw and the first clamping jaw is pivotable between a first position in which the tongue engages in a slot provided in a post or shaft carrying the second clamping jaw and a second disengaged position.

9. A clamp according to claim 8, wherein more than one slot is provided in the said post or shaft so that the height to which the second clamping jaw is raised and retained above the first clamping jaw can be varied.

10. A clamp according to claim 7, wherein the latch comprises an eccentric cam member which is mounted in a slot in the side wall of the tubular member through which extends the shaft or post carrying the second clamping member.

11. A clamp according to claim 7, wherein the shaft is at least partially rotatable about a substantially vertical axis relative to the tubular member to cause a pin mounted on an internal surface of the tubular member to engage in a horizontal slot or channel in the shaft, or vice versa.

12. A clamp according to claim 11, wherein the said horizontal channel opens into the lower end of a channel which serves to guide the shaft in the tubular member.

13. A clamp according to claim 12, wherein the guide channel defines a

helical portion towards the lower end thereof, immediately before the said horizontal slot, which helical portion allows the shaft and the upper clamping jaw carried thereby to be pivoted about the said vertical axis relative to the lower clamping jaw as it reaches the fully raised position.

14. A clamp according to any preceding claim, wherein one or both facing surfaces of the first and second clamping jaws is provided with wood gripping means.

15. A clamp according to claim 14, wherein the wood gripping means takes the form of short spikes or studs.

16. A clamp according to any preceding claim, further comprising a stand to support the clamp on the grounds.

17. A clamp according to claim 16, wherein the stand takes the form of a tripod.

18. A clamp according to claim 17, wherein one leg of the tripod is longer than the other two and extends in the same direction as the two clamping jaws.

19. A clamp according to any of claims 1 to 15, wherein the clamping device is adapted to be permanently sited on a wall or for portability it may be permanently attached to a vehicle.