CLAMPING DEVICE

Abstract: The invention concerns a clamping device for use by individuals when cutting sheet material, such as planks or boards. The device comprises an upper clamping surface (1), a lower clamping surface (2) and a projection (3) extending downwardly from the upper clamping surface (1) into an aperture (4) of the lower clamping surface (2). In use, the clamping device is slipped onto an end face of sheet material after an initial cut has been made. The user can then proceed to extend the saw cut using a hand saw, jigsaw etc., safe in the knowledge that the clamping device will prevent excessive vibration of the cut ends of the material and that the projection (3) will maintain the gap (known as the kerf) between the cut open.

Description: CLAMPING DEVICE The invention relates to a clamping device and, in particular, to such a device for use in connection with the sawing or cutting of material. When cutting sheet materials such as metal, wood, MDF etc., problems often arise caused by vibrations due to the sawing or cutting. Such vibrations can cause the saw to bind, with the width of the cut (known as the Kerf) tending to close and pinch the saw blade, thus making further sawing problematic. Prior solutions to the problem of binding are known from the logging industry in the United States and involve placing a wedge into the Kerf to keep it open. However, as will be appreciated, such solutions are not really appropriate for sheet material as the wedges will either on the one hand fall out or, on the other, damage the material. US 4,418,890 discloses a device which is intended to overcome some of the problems with prior wedges and spread the Kerf to prevent the saw from binding. This patent describes a conventional wedge design which is relatively thin and has flanges above and below the wedge. In use, the leading edge of the wedge is placed or lightly forced into the Kerf opening, with the flanges above and below helping to support the cut end of the board and keep the board essentially in one plane. Also, the flanges help, at least to an extent, in preventing the wedge from falling free. Whilst the abovementioned device goes someway towards solving the problems it is still of relatively bulky construction and, by having the flanges placed above and below the wedge, it will be appreciated that the range of thicknesses of material which can be accommodated by a single device are relatively limited. It is an aim of preferred embodiments of the present invention to provide a clamping device for maintaining a kerf open during a cutting or sawing operation, the device being of simplified construction and able to accommodate a wide range of thicknesses of material to be cut or sawn. According to a first aspect of the invention, there is provided a clamping device, the device comprising a clip having upper and lower clamping surfaces for receiving between them a material which it is desired to cut, and kerf maintaining means extending between said upper and lower clamping surfaces for insertion into a cut space (kerf), said upper and lower clamping surfaces being positively biased, in use, towards one another so as to grip the material therebetween. Preferably, said upper and lower clamping surfaces form part of a single piece of material. Said kerf maintaining means preferably has a width which is substantially the same as the kerf width. In preferred embodiments, the upper clamping surface is a predominantly flat surface and the lower clamping surface is curved. The curve of the lower clamping surface is preferably arranged such that the upper and lower clamping surfaces are nearest to one another along a line extending across the width of the lower clamping surface and passing through the Kerf maintaining means. The device may comprise the upper clamping surface, which is essentially arranged in a horizontal plane, a rear wall which depends substantially vertically from a rear edge of the upper clamping surface, a bottom ledge which extends essentially parallel to the upper clamping surface and is joined to a bottom edge of the rear wall and the lower clamping surface which curves upwardly from a forward edge of the bottom ledge, toward the upper clamping surface and then curves away again from the upper clamping surface, the Kerf maintaining means being arranged to extend through the lower clamping surface at the point at which the lower clamping surface is closest to the upper clamping surface. The lower clamping surface preferably does not have a constant radius of curvature. The device preferably has an entry portion which facilitates insertion of the material to be cut and a jaw region in which the material is clamped. The entry portion may be formed by the free ends of said upper and lower clamping surfaces being physically separated from one another by a distance greater than the thickness of the material to be cut so as to aid insertion of the material between the upper and lower clamping surfaces. Preferably, the lower clamping surface is curved in such a manner that the radius of curvature of the lower clamping surface is much greater at the point at which the lower clamping surface is closest to the upper clamping surface than it is at the free end of the lower clamping surface. By reducing this radius of curvature progressively toward the free end of the lower clamping surface, insertion of material between the upper and lower clamping surfaces is facilitated. In other words, by arranging the lower clamping surface to curve in this manner, a piece of material may be easily inserted between the two clamping surfaces without compromising the clamping force when the material is in place. The jaw region is preferably arranged such that in that region the upper and lower clamping surfaces are separated from each other by a distance which, prior to insertion of the material to be cut, is less than the thickness of the material to be cut. Preferably, said upper and lower clamping surfaces comprise a single piece of resilient elastically deformable material, such as spring steel. The clamping surfaces may be formed from a single piece of material, by folding and stamping operations. In certain embodiments, the entire device may be formed from a single piece of material. The kerf maintaining means may be integral with the upper clamping surface and downwardly depend from it through an aperture in the lower clamping surface. Alternatively, the kerf maintaining means may be integral with the lower clamping surface and depend upwardly from it through an aperture in the upper clamping surface. In other preferred embodiments of the present invention, the kerf maintaining means may comprise a pin having a first end and a second end, the first end being connected to a support means of the device, and the pin being arranged to extend through said upper and lower clamping surfaces. The support means may comprise a tab formed out of material from the lower clamping surface. A second end of said pin may be attached to the upper clamping surface. Alternatively, the support means may comprise a tab formed out of material from the upper clamping surface. The second end of the pin may be attached to tem lower clamping surface. Said pin may be removable and alternative sized pins substituted therefor according to desired kerf widths and/or according to the thickness of the material to be cut. Visual guide means may be formed in the upper clamping surface to enable a cut space in the material to be cut to be observed. The visual guide means may comprise one or more apertures formed in the upper clamping surface and arranged between a front edge of the upper clamping surface and the Kerf maintaining means. The aperture may be in the shape of an arrow head, wherein the point of the arrow head is arranged to correspond to a mid-position of the cut space. A plurality of such apertures may be provided, so as to enable the Kerf maintaining means to be easily guided into the cut space. Hanging means may be provided for facilitating storage of the device in a tool rack or the like. The hanging means may comprise a hole formed in the upper or lower clamping surface, so that a hook or the like may engage with the hole. Preferably, the hole is formed adjacent to one side edge of the upper clamping surface. By way of example only, specific embodiments of the present invention will now be described with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a perspective view of the first embodiment; Figures 2A and B are respectively a plan view of the device of the first embodiment as seen from arrow A and a side view from arrow B of Figure 1; Figures 2C and D are side and plan view of the first embodiment and showing a piece of material to be cut; Figure 3 is a side view of a second embodiment of the device; Figure 4A is a perspective side view of the device of Figure 3 and Figure 4B is a detailed view showing how a pin of the device may be retained; Figure 5 shows how the device of Figures 3 and 4 may be stamped and folded from a single sheet of material; Figure 6 is a detailed view of different pins which may be used with the device of Figures 3 to 5; and Figure 7 shows further optional features of the device. Referring now to Figures 1, 2A and 2B, a first embodiment of the invention will now be discussed. The device of Figure 1 is a clip formed from a single piece of material, such as spring steel, by stamping and folding operations. The clip has an upper clamping surface 1 which extends generally in a single plane, a lower clamping surface 2 which is curved and a kerf maintaining means 3 which in the embodiment shown is formed by cutting or stamping three sides of a rectangle out of the upper clamping surface and folding down the material from the cut or stamped area on the fourth side of the rectangle so as to make a downwardly depending projection. In the lower clamping surface 2, there is formed an aperture 4, into which the projection 3 is arranged to extend, in use. The aperture 4 (hidden detail of which is shown in Figure 2A by broken lines) and projection 3 are formed generally centrally with respect to the width of the clamping surfaces. The upper clamping surface 1 has an upwardly extending lip 5 toward a free end portion thereof and the lower clamping surface 2 has a downwardly sloping portion 6 towards its' free end, such that between the lip 5 and the sloping portion 6, there is defined an entry region into which sheet material may be guided until it comes to a region of reduced width, which is shown best in the enlarged detail view of Figure 2B and labelled "x". It is this area "x" that forms a jaw region in which the sheet type material is gripped between the lower 2 and upper 1 clamping surfaces. The upper clamping surface 1, at a rear fold thereof is joined with an upstanding wall 7 arranged generally perpendicular to the main extent of the upper clamping surface. At the base of the wall 7, there is a bottom ledge 8 which, at its forward edge joins with the lower clamping surface 2. The lower clamping surface 2 extends upwardly from the bottom ledge so as to approach the underside of the upper clamping surface 1 and then curves back down away from the upper clamping surface 1. The aperture 4 formed in the lower clamping surface is positioned so as to traverse the line X-X shown in Figure 1 which represents the points across the width of the lower clamping surface 2 which are closest to the upper clamping surface 1. Use of the device of Figures 1, 2A and 2B will now be described with the aid of Figures 2C and 2D. Typically, a user will wish to cut sheet material, such as planks or boards. The user will make an initial saw cut from the edge of the board and extend that cut inwardly by a few centimetres. The cut 10 needs to be extended inwardly in this manner by a distance corresponding approximately to the dimension Y shown in Figure 2B. Once such a cut has been made, the device may be inserted onto the board by pushing the entry region formed between areas 5 and 6 of the device against the cut edge of the board 9. As the edge of the board proceeds further into the entry region, the upper 1 and lower 2 clamping surfaces will tend to diverge. By arranging for the lower clamping surface 2 to slope downwardly in a progressively steeper fashion from line X-X toward its free end, insertion is facilitated. The projection 3 is guided into the saw cut 10 and the remainder of the device eased onto the board such that the board 9 sits in the fashion shown in Figure 2C and 2D. It will be appreciated that once the device has been inserted onto the cut edge of the board 9, the clamping surfaces grip the board 9 across the width of the clamp on either side of the saw cut 10 so that relative up and down movement of the material on one side of the kerf 10 with respect to material on the other side of the kerf 10 is inhibited by the clamping action. By inhibiting such further movement, the action of a saw (such as a jigsaw or other cutting means) to extend the saw cut 10 further inwardly is able to proceed in a relatively smooth manner without the vibrations from the cut material causing the blade to bind. The projection 3 which is inserted into the saw cut 10 acts so as to keep the saw cut open - i.e. the kerf is maintained. Referring now to Figures 3 to 5, there is shown an alternative embodiment. The embodiment shown is particularly effective for use with very thin material such as metal sheets. This alternative embodiment is also formed by stamping and folding operations and may be formed from a single piece of sprung steel to the pattern shown in Figure 5. From Figure 5 it will be appreciated that the upper clamping surface 1 has a pin receiving hole 11 formed in it, and the lower clamping surface 2 has a tab of material 12 stamped from it to provide a lower support for a second end of a pin 13. The pin 13 extends upwardly through the aperture caused by stamping of the tab 12 and may be held in place between the tab 12 and upper clamping surface 1 by means of a circlip or similar (as shown in the detailed view of Figure 4A) . In Figure 4A the circlip 14 has an area of reduced circumference 15 for gripping a notch (not shown) formed in an upper part of the pin 13 and also has an area of enlarged circumference 16. The circlip may be mounted onto the end of the pin 13 by first putting the area of enlarged circumference over the end of the pin and then laterally displacing the circlip 14 such that the area of reduced circumference 15 moves into contact and securely engages with the groove formed at the top of the pin 13. Similar means are provided at the bottom of the pin 13. In fact, due to the resilient nature of the material of the clamp, a circlip may not be required and the pin 13 may be held in place between tab 12 and upper clamping surface 1 by spring force. By having the pin 13 removable, it is possible to use pins of different diameters according to the desired width of saw cut to be made or the type of cutting operation to be performed. Also, the provision of a replaceable pin enables easy repair of the device if a pin 13 becomes damaged. Use of the second embodiment is generally similar to use of the first embodiment and will not be described further. Figure 6 shows a number of alternative pin sizes (widths) which can be adopted. Figure 7 is a view similar to the view of Figure 2A and shows the upper surface 1 of a clamp, Kerf maintaining means 3 and the upwardly extending lip 5 of the entry portion. Also seen on that Figure is a pair of apertures 14A, 14B. These two apertures are stamped or cut out of the upper surface 1 and are in the form of arrow heads. The arrow heads are aligned with the Kerf maintaining means 3 along a line Y-Y. By providing these two apertures 14A, 14B the clamp may be easily positioned onto the piece of material to be cut, with the initial cut space being viewed through apertures 14A and 14B and aligned such that the point of the arrow is in the middle of the cut space as the device is pushed on. By aligning in this manner, the Kerf maintaining means 3 fits neatly into the cut space. Another optional feature also shown in Figure 7 is an aperture 15 formed adjacent to a side edge of the upper clamping surface 1. Aperture 15 may be used to hang the device from a hook in a workshop. It will be appreciated that the formation of this aperture may be varied so as to assume whatever shape is required. It will have been appreciated from the foregoing discussion that devices in accordance with embodiments of the present invention provide a simple means for allowing trouble free cutting or sawing of a diverse range of materials such as boards, planks, metal sheets, etc. Because the device is formed from a material such as spring steel, a single device is able to accommodate , a range of different thickness of materials, the clamping action being brought about by the device enabling the kerf maintaining means to sit securely within the kerf and inhibit saw blade binding. The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) , may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment (s) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims: CLAIMS 1. A clamping device, the device comprising a clip having upper and lower clamping surfaces for receiving between them a material which it is desired to cut, and kerf maintaining means extending between said upper and lower clamping surfaces for insertion into a cut space (kerf), said upper and lower clamping surfaces being positively biased, in use, towards one another so as to grip the material therebetween. 2. A device according to claim 1, wherein said upper and lower clamping surfaces form part of a single piece of material. 3. A device according to claim 1 or 2, wherein said kerf maintaining means has a width which is substantially the same as the kerf width. 4. A device according to claim 1, 2 or 3, wherein the upper clamping surface is a predominantly flat surface and the lower clamping surface is curved. 5. A device according to claim 4, wherein the curve of the lower clamping surface is arranged such that the upper and lower clamping surfaces are nearest to one another along a line extending across the width of the lower clamping surface and passing through the kerf maintaining means . 6. A device according to any of the preceiding claims, wherein the device comprises the upper clamping surface, which is essentially arranged in a horizontal plane, a rear wall which descends substantially vertically from a rear edge of the upper clamping surface, a bottom ledge which extends essentially parallel to the upper clamping surface and is joined to a bottom edge of the rear wall and the lower clamping surface which curves upwardly from a forward edge of the bottom ledge, toward the upper clamping surface and then curves away again from the upper clamping surface, the kerf maintaining means being arranged to extend through the lower clamping surface at the point at which the lower clamping surface is closest to the upper clamping surface. 7. A device according to claim 6, wherein the lower clamping surface does not have a constant radius of curvature. 8. A device according to any of the preceding claims, in which the device has an entry portion which facilitates insertion of the material to be cut and a jaw region in which the material is clamped. 9. A device according to claim 8, in which the entry portion is formed by the free ends of said upper and lower clamping surfaces being physically separated from one another by a distance greater than the thickness of the material to be cut so as to aid insertion of the material between the upper and lower clamping surfaces. 10. A device according to any of the preceding claims, in which the lower clamping surface is curved in such a manner that the radius of curvature of the lower clamping surface is much greater at the point at which the lower clamping surface is closest to the upper clamping surface than it is at the free end of the lower clamping surface. 11. A device according to claim 8 or 9, or 10 as dependent thereon in which the jaw region is arranged such that in that region the upper and lower clamping surfaces are separated from each other by a distance which, prior to insertion of the material to be cut, is less than the thickness of the material to be cut. 12. A device according to any of the preceding claims, in which said upper and lower clamping surfaces comprise a single piece of resilient elastically dformable material, such as spring steel. 13. A device according to claim 12, in which the clamping surfaces are formed from a single piece of material, by folding and stamping operations. 14. A device according to claim 12 or 13, wherein the entire device is formed from a single piece of material. 15. A device according to any of the preceding claims, in which the kerf maintaining means is integral with the upper clamping surface and downwardly depends from it through an aperture in the lower clamping surface. 16. A device according to any of claims 1 to 14, the kerf maintaining means is integral with the lower clamping surface and depends upwardly from it in which through an aperture in the upper clamping surface. 17. A device according to any of claims 1 to 14, in which the kerf maintaining means comprises a pin having a first end and a second end, the first end being connected to a support means of the device, and the pin being arranged to extend through said upper and lower clamping surfaces. 18. A device according to claim 17, in which the support means comprises a tab formed out of material from the lower clamping surface. 19. A device according to claim 17 or 18, in which a second end of said pin is attached to the upper clamping surface. 20. A device according to a claim 17 or 18, wherein the support means comprises a tab formed out of material from the upper clamping surface. 21. A device according to claim 20, wherein the second end of the pin is attached to the lower clamping surface. 22. A device according to any of claims 17 to 21, wherein said pin is removable and alternative sized pins may be substituted therefor according to desired kerf widths and/or according to the thickness of thematerial to be cut. 23. A device according to any of the preceding claims, visual guide means is formed in the upper clamping surface to enable a cut space in the material to be cut to be observed. 24. A device according to claim 23, in which the visual guide means comprises one or more apertures formed in the upper clamping surface and arranged between a front edge of the upper clamping surface and the kerf maintaining means . 25. A device according to claim 24, in which the aperture is in the shape of an arrow head, wherein the point of the arrow head is arranged to correspond to a mid-position of the cut space. 26. A device according to claim 24 or 25, in which a plurality of such apertures are provided, so as to enable the kerf maintaining means to be easily guided into the cut space. 27. A device according to any of the preceding claims, in which hanging means are provided for facilitating storage of the device in a tool rack or the like. 28. A device according to claim 27, in which the hangin means comprises a hole formed in the upper or lower clamping surface, so that a hook or the like may engage with the hole. 29. A device according to claim 28, in which the hole is formed adjacent to one side edge of the upper clamping surface .

Inventors: CARTWRIGHT BERNARD, CARTWRIGHT, BERNARD
Applicants: CARTWRIGHT BERNARD, CARTWRIGHT, BERNARD
Application year: 1999
Main classification: B27G19
IPC codes: B23K37, B25B5, B27G19