GB1593280A

GB1593280A - Wood-working cramps

Info

Publication number: GB1593280A
Application number: GB161277A
Authority: GB
Original assignee: Lowe W J
Current assignee: Lowe W J
Priority date: 1978-04-11
Filing date: 1978-04-11
Publication date: 1981-07-15

Description

(54) IMPROVEMENTS IN OR RELATING TO WOOD-WORKING CRAMPS (71) I, WILLIAM JAMES LOWE, of 118 Hinderton Road, Birkenhead, England, a British Subject, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention concerns woodworking cramps which may also be used as braces, i.e. to push two surfaces apart rather than drawing them together in a normal cramp manner.

A conventional cramp is a low-duty vice with a large distance between its jaws and can also be used for marking out or guiding a tool. It comprises an elongate beam with a stop or jaw at one end mounted for adjustable movement along the beam so as to roughly adjust the cramp to the workpieces, this stop will be termed a fixed stop, and another stop at the other end which is displaceable along the beam by suitable means to give the cramping force, this second stop will be termed a movable stop.

The present invention provides a woodworking cramp comprising an elongate beam with a fixed stop towards one end and a movable stop towards the other end, the beam having a cross-section such that the beam can rest stably with one face abutting a flat surface of a workpiece disposed between the stops and with the beam providing a straight edge on at least one side, characterised in that the stops are rotatable about axes perpendicular to said face with profiles such that they can present any one of a plurality of clamping faces to the workpiece edges.

The stops can be so mounted to the beam that the mountings leave the straight edge unimpeded at least for the depth of the face plate of a cutting tool so that the cutting tool, for example a powered portable saw, can have a run-in and a run-out. Since the cutting blade of a powered portable saw is displaced by a considerable distance from that guiding edge of the saw which abuts the straight edge, the stops can project beyond the beam below the said surface.

A means forming part of the movable stop for applying cramping force preferably lies wholly outside the path of the tool although its operating handle or other operating means could travel into the path during the application of cramping force provided that when the saw or other tool was in use the operating handle or means was outside the path. A ratchet device simplifies the construction of the means in this respect.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side elevation of a cramp according to the present invention Figure 2 is an end view of the cramp of Figure 1, Figure 3 is a detail showing a stop, Figures 4 to 7 show various applications of the stop illustrated in Figure 3, Figure 8 is a plan detail illustrating an over-centre device for securing two lengths of a sectional beam together Figure 9 is a similar view showing the use of a spring-loaded pip arrangement for the same purpose, Figure 10 is a side elevation of a second embodiment, Figure 11 is a worm's eye view of the movable stop end of the embodiment of Figure 10 with the stop in place, Figure 12 is a section on the line XII - XII of Figure 11, Figure 13 is a perspective view of a beam of a third embodiment, Figure 14 is a section of a fixed stop in the beam of Figure 13, Figure 15 is a cross-section through a beam showing a further form of a fixed stop, Figure 16 shows an adaptation of a beam for one t y p e o f s t e a d y Figure 17 shows tlult type of steady, and Figure 18 shows a helm with another type of steady.

The cramp shown in Figures 1 and 2 comprises a rectangular hollow beam 20 with a longitudinal slit 21 in one face which will rest stably on a flat workpiece surface 23, a fixed stop arrangement 24 and a movable stop arrangement 25. The fixed stop arrangement comprises a stop 26 rotatably mounted on a bolt 27 and disposed below the beam. The bolt 27 extends through the slit 21 into a body 28 within the beam 20 and extending obliquely across the interior of the beam in the lengthwise direction. At the top of this body there is a domelike protuberance 29 which engages in a selected one of a sequence of holes 30 in the top of the beam.There is a plate spring 31 secured to the body and biassing the body so that it contacts the top and bottom surfaces of the beam's interior but there is sufficient play for the stop to be gripped and tilted to free the protuberance from the hole against the bias and the stop arrangement slid along the beam to be engaged in another hole. The movable stop arrangement comprises a block 32 with a tapped hole 33 therein and which is slidable along the beam interior which possibly has keys slidably engaged by keyways in the block 32 and also comprises a stop 26 below the beam and secured through the slit 21 to the block 32 by a bolt 34. A lead screw 35 journalled in two bulk-heads 36 serves to displace the movable stop arrangement along the beam.

This lead screw is rotatable by a ratchet or other spanner engaging a non-circular end 37 of the lead screw itself or by means of a bevel gear arrangement 38 having alternative drive shafts 39 journalled in the top and one side of the beam.

When using the cramp as a brace, the fixed stop arrangement would be slid out from the beam and replaced in the reverse direction that is with the protuberance leading.

The stops 26 which are as stated rotatable on their bolts have profiles as illustrated in Figure 3. Each stop has at least one straight side 40 for use in normal cramping as shown in Figure 4, at least one outward pointing corner 41 for use in internal corner clamping as shown in Figure 5, and one re-entrant corner 42 for use in external corner clamping as shown in Figure 6. The outward pointing corner or one of the outward pointing corners can be rounded as at 43 for use when the internal corner clamped thereby is itself rounded. The straight side can be used for clamping when the workpiece surfaces clamped are not parallel or when the cramp is to be used skewed across the workpieces as shown in Figure 7.

The beam has two straight edges 44 one on each side of the beam. These straight edges have a vertical height of about one inch which is greater than the sole plate depth of known portable powered cutting tools. Any drive shaft 39 projecting from a side of the beam should be above this height and it is possible to have a longitudinal rib (not shown) above this height to protect the straight edge from knocks.

Sometimes an extremely long cramp is needed and in general cramps are not very convenient to carry. Therefore the beam is sectionalised. One or more extension pieces 45 can be attached to the cramp for example as shown in Figure 8 or Figure 9. Each extension piece has the same section as the main cramp but has at the end which fits into the cramp a dowel-like projection 46 projecting into the cramp proper. In Figure 8, two over centre devices 47 are attached to the side of the cramp proper and to the extension pieces to hold the extension piece axially in relation to the cramp. In Figure 9, the projection 46 carries two spring loaded pips 48 which engage in holes provided therefor in the cramp sides. The over centre devices and pips are disposed above the straight edges 44.

The use of sections other than rectangular is not excluded.

When using the cramp to guide a hand saw or during any other operation which may damage the straight edge, a protective cover may be applied to the straight edge.

Such a protective cover could be a strip of plastics material which could be attached magnetically to the cramp by suitable loading of the plastics material.

The embodiment of Figures 10 to 12 is given to illustrate a number of variants which can be used singly or together to modify the above described embodiment.

In this embodiment the beam is of square section externally with grooves 49 cut along the corners so as to allow sliders 50 to be attached to any face in a dove-tail manner within the width of the beam. Each of these sliders has an internally threaded boss 51 rivetted to it. Two of these sliders form the fixed and movable stops of the cramp. Stops 26 are journalled on the outside of these two sliders and at least the fixed stop has a thumb screw 52 locking the stop axially of the beam. A third slider has a cam 53 rotatable on the outside of the boss and this cam is rotatable by a handle 54 which is preferably hinged so as to hang vertically when unused and thus be out of the way.

This third slider also has a thumb screw for locking it axially relative to the beam. The cam bears on an end of the movable stop slider which can be down-turned so as to provide a shoulder 55; the clamping force is thus applied at the level of the stop 26 and there is little tendency for canting of the stop.

In this embodiment the fixed stop end of the beam has a protruding cylindrical spigot 56 for projecting into an end of an extension piece (not shown). This spigot is preferably secured permanently into the beam and has transverse pins 57 such that it can be secured axially in the extension piece by insertion and twisting in the nature of a bayonet fastening. The spigot is preferably a tight fit in the extension piece. Because of this type of fastening, a cylindrical internal bore is preferred for the beam.

The beam is preferably an aluminium alloy extrusion and this will cheapen manufacturing costs.

Instead of having the sliders fit directly onto the beam, clip-on plastics material channels can fit onto the dove-tails and then receive the sliders. This will protect the beam faces.

It is of course possible to have a slit in the end of the beam of Figure 10 and to use the lead screw of the first embodiment for displacing the movable stop.

The embodiment of Figures 13 and 14 differs from the first embodiment in the fixed stop arrangement. The holes 30 are in the bottom rather than the top of the beam and are in the form of arcuate notches 61 disposed symmetrically along the sides of the slit 21. The stop 26 is rendered captive to the beam by having a stepped boss 62 which has three different sections; the smallest section 63 allowing the boss to be slid along the slit 21, the intermediate section 64 locating in a selected one of the holes 30 to prevent such sliding and a largest section or head 65 being able to slide along inside the beam interior from an end of the beam and not being able to pass through the slit or a hole and so rendering the boss and thus the stop captive.The head 65 should be at the end of the boss remote from the stop but the order of the other two depends on personal preference; with the arrangement as shown with the section 64 nearer the stop, the stop can be slid along the beam and then locked by pushing the stop upwardly to engage the section 64 with a hole.

Whilst the invention has been described using a hollow rectangular beam, other shapes of beam could be used such as a hollow T-section with the cross piece of the T used to provide the face 22.

Figure 15 shows an alternative form of fixed stop arrangement which can be used with the beam 20 of the first embodiment. A block 66 is free to slide along the interior of the beam. The bolt 27 securing the stop 26 to this block passes through a stepped hole 67 in this block, first through a smaller diameter length and then into a larger diameter portion housing a compression spring 68. A dome-like cap 69 is fitted to the bolt, the arrangement being that normally the cap will project under the spring bias into a hole 30 but that a force applied to the stop can retract the cap into the larger diameter portion.

Figure 16 shows an adaptation of a beam to enable a steady to be fitted. A window 70 is cut out from one side of the beam, the side not intended to be used as a straight edge.

The window is generally key-hole shape with a larger portion 72 nearer the end of the beam and a slit-like portion 73. This window is intended to receive a steady as shown in Figure 17. The steady 74 basically consists of a square section bar suitable for insertion into the said portion 72 and having grooves 75 in one end so that the bar can be inserted in the portion 72 and then slid along the portion 73. The arrangement being such that a cantilever force on the bar will lock it in the portion 73. At the other end of the steady which may be cranked as shown there is a clamping device 76 carried by an articulated-joint. This steady is useful when cramping obliquely across a workpiece to help prevent slippage. Normally there will only be a steady at the movable stop end of the beam.

The steady of Figure 18 operates in a similar way but does not require any modification to the beam. The steady consists of a strip of metal cranked perpendicularly to the main body of the strip at one end into a U-formation largely complementary to the beam but having the outer leg 78 somewhat shorter to leave the edge being used as the straight edge unimpeded, so that a saw sole plate can pass, for a suitable distance up from the work piece surface. The main body of the strip is cranked in the plane of this main body and carries at the other end a block 79 which carries a clamping device such as a screw for engagement with the workpiece edge. This Figure also shows that the screw itself need not be tiltable and it is thought that this may not be desirable since it might make slipping easier.The pressure pad on the end of the screw would be capable of conforming to the work-piece edge by, for example, tilting. Instead of a screw operated pressure pad, it would be possible to use a cam or other means for clamping onto the edge or indeed something like a C-clamp or a bulldog clip to grip on opposite faces of the workpiece adjacent to the edge. In service the main body of the strip would rest on the work-piece so the strip would be itself steadied. It would of course be simple to have an ancillary Cclamp, or spring clip arrangment where the strip crosses the edge of the workpiece as well as the block 79 or instead of the block 79. When there was no lip for engagement, the steady would be arranged that any C-clamp or bull dog clip would be clear of the workpiece.When there is a lip, it would be possible to have a C-clamp sliding along the beam using the slot and possibly with one at each end of the beam. Often, and especially when the work is to be veneered or otherwise covered, screw holes are not objectionable, and it is possible to have guide blocks of a slippy plastics material, for example, within the beam. These guide blocks would be secured to the work-piece but allow relative sliding of the beam. If the beam has holes 30 along its length, except for the length over the length over the lead screw 35, wood screws fitting in the blocks could be driven home with the beam in its desired position.Preferably the block and the wood screw would have a threaded engagement so that screwing in the screw would not pull down the block so as to clamp the beam but the engagement of the screw to the workpiece would be almost incidental so allowing relative movement of the workpiece and beam during cramping operations. The most frequent need to cramp obliquely is when working on rightangled mitre joints; for working on 90" corners with the beam at 45" across the corner a steady clipping over the beam in the nature of, say, Figure 18 with a downward projection for fitting in the internal corner and so preventing outward slippage of the beam as the cramping force is increased.

On rare occasions, it may be desired to cramp circular or other non-straight-sided work-pieces. For this, a beam accessory could be used, the accessory being a bifurcated beam length comprising a 1200 spider into which three straight beam lengths could be fitted. Two of these would have a fixed stop arrangement and the third a movable stop arrangement.

WHAT I CLAIM IS: 1. A wood-working cramp comprising an elongate beam with a fixed stop towards one end and a movable stop towards the other end, the beam having a cross-section such that the beam can rest stably with one face abutting a flat surface of a work-piece disposed between the stops and with the beam providing a straight edge on at least one side, characterised in that the stops are rotatable about axes perpendicular to said face with profiles such that they can present any one of a plurality of clamping faces to the workpiece edges.

2. A cramp according to claim 1 wherein the stops are so mounted to the beam that they leave a sufficient height of the straight edge for the passage of a face plate of a tool unimpeded.

3. A cramp according to claim 2 wherein the beam has a longitudinal slit in said face to allow the stops to be mounted from within the beam.

4. A cramp according to claim 3 wherein the fixed stop is mounted from a body slidable within the beam, the beam has a sequence of holes along the top, and the body has a spring loaded projection for engagement in a selected one of said holes.

5. A cramp according to claim 4 wherein the said projection is the end of a shaft on which the stop is also mounted so that the projection can be disengaged from the hole by pulling down the stop.

6. A cramp according to claim 3, claim 4 or claim 5 wherein the movable stop is mounted from a block mounted on a lead screw for movement lengthwise of the beam.

7. A cramp according to any one of the preceding claims wherein the beam is made in clip-together sections.

8. A cramp according to any one of the preceding claims in combination with a steady which slidably engages the beam.

9. A combination according to claim 8 wherein at the end remote from the beam the steady has means for exerting a force on the edge of the workpiece, the reaction force exerting a cantilever force on the steady which locks the steady to the beam.

10. A cramp substantially as herein described with reference to the accompanying drawings and especially Figures 1 to 15.

11. A cramp according to claim 10 in combination with a steady substantially as herein described with reference to Figures 16 to 18 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. 79. When there was no lip for engagement, the steady would be arranged that any C-clamp or bull dog clip would be clear of the workpiece. When there is a lip, it would be possible to have a C-clamp sliding along the beam using the slot and possibly with one at each end of the beam. Often, and especially when the work is to be veneered or otherwise covered, screw holes are not objectionable, and it is possible to have guide blocks of a slippy plastics material, for example, within the beam. These guide blocks would be secured to the work-piece but allow relative sliding of the beam. If the beam has holes 30 along its length, except for the length over the length over the lead screw 35, wood screws fitting in the blocks could be driven home with the beam in its desired position.Preferably the block and the wood screw would have a threaded engagement so that screwing in the screw would not pull down the block so as to clamp the beam but the engagement of the screw to the workpiece would be almost incidental so allowing relative movement of the workpiece and beam during cramping operations. The most frequent need to cramp obliquely is when working on rightangled mitre joints; for working on 90" corners with the beam at 45" across the corner a steady clipping over the beam in the nature of, say, Figure 18 with a downward projection for fitting in the internal corner and so preventing outward slippage of the beam as the cramping force is increased. On rare occasions, it may be desired to cramp circular or other non-straight-sided work-pieces. For this, a beam accessory could be used, the accessory being a bifurcated beam length comprising a 1200 spider into which three straight beam lengths could be fitted. Two of these would have a fixed stop arrangement and the third a movable stop arrangement. WHAT I CLAIM IS:

1. A wood-working cramp comprising an elongate beam with a fixed stop towards one end and a movable stop towards the other end, the beam having a cross-section such that the beam can rest stably with one face abutting a flat surface of a work-piece disposed between the stops and with the beam providing a straight edge on at least one side, characterised in that the stops are rotatable about axes perpendicular to said face with profiles such that they can present any one of a plurality of clamping faces to the workpiece edges.