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(11) | EP 0 243 144 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Workpiece clamping device |
| (57) A workpiece clamping device for a workbench, comprising a housing (16) having at
least one horizontal bore (30) therein, means (18) for locating the housing on a workbench,
a plug (22) mounted for limited movement in said housing in a direction transverse
to said horizontal bore, an aperture (32) through said plug in substantial alignment
with said bore (30), an elongate screw-threaded rod (38) extending through said at
least one bore (30) and said aperture (32), the diameter of said at least one bore
(30) being slightly larger than the outside diameter of the rod (38), the aperture
(32) having a cross section including a first portion (36) having a screw-thread cooperable
with the thread of the rod (38) and a second portion (34) allowing free movement of
the rod (38) longitudinally of the rod (38), whereby movement of the plug (22) to
a first position allows the rod (38) to slide freely relative to the housing and give
coarse adjustment of the rod (38) and movement of the plug (22) to a second position
causing the thread to engage, so that rotation of the rod (38) can give fine adjustment
thereof, and a workpiece engaging member (42) mounted on, or engagable by, the rod
(38) for movement therewith, the rod (38) being rotatable relative to said member
(42). |
[0002] It is very important when carrying out any operation on a workpiece for the workpiece to be firmly held in position so that it cannot move or judder so that a good machining or other operation can be carried out on the workpiece. A particular problem arises in workbenches which are designed for the do-it-yourself man or the professional woodworker. For example, in British Patent No l 529 642 it has been proposed to provide a tooling jig comprising a base, such as a workbench, for supporting a workpiece, a longitudinally extending guide fence provided on the base, the guide fence defining a straight edge, a bridge which is directly secured to the guide fence and positioned to overlie a workpiece placed against the guide fence and a guideway on the bridge extends axially perpendicular to and intersecting the line of the straight edge, the guideway being adapted to guide for movement therealong a router accurately perpendicularly to the straight edge. Such a construction enables one to produce very accurate right angled edges to the workpiece. However, it is important that a simple arrangement be provided to secure the workpiece against the guide fence.
[0003] At least in part for use with such a device it is now proposed, according to the present invention, to provide a workpiece clamping device for a workbench, comprising a housing having at least one horizontal bore therein, means for locating the housing on a workbench, a plug mounted for limited movement in said housing in a direction transverse to said horizontal bore, an aperture through said plug in substantial alignment with said bore, an elongate screw-threaded rod extending through said at least one bore and said aperture, the diameter of said at least one bore being slightly larger than the outside diameter of the rod, the aperture having a cross section including a first portion having a screw-thread cooperable with the thread of the rod and a second portion allowing free movement of the rod longitudinally of the rod, whereby movement of the plug to a first position allows the rod to slide freely relative to the housing and give coarse adjustment of the rod and movement of the plug to a second position causing the thread to engage, so that rotation of the rod can give fine adjustment thereof, and a workpiece engaging member mounted on, or engagable by, the rod for movement therewith, the rod being rotatable relative to said member.
[0004] Such a construction could be made very simply with only a few components and can give rapid coarse adjustment simply by operating the plug, which is preferably spring urged to the second position. The operation of the plug, to the first position, therefore, can simply be achieved by pressing downwardly on it with the finger.
[0005] Advantageously, the housing is provided with a cylindrical projection on its lower surface, this projection being engagable in an aperture in the workbench. The workbench itself may be provided with several such apertures, positioned at spaced locations on the workbench, preferably at a defined modular spacing.
[0006] The member which is secured to the free end of the rod is advantageously of L shape and can be detachably mounted on the rod to enable the outside of the vertical wall to engage the workpiece or, alternatively, the inside, thereby leaving a clearance for the operation, for example, of a planer. The rod may be provided with some suitable means to facilitate rotation, for example a pivotally mounted tommy-bar.
[0007] In order that the present invention may more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawing, in which:
Figure l is a cross section through the housing and its associated plug, of one embodiment of a device according to the invention;
Figure 2 is a plan view of the device of Figure l;
Figure 3 is a side elevation of the work engaging member; and
Figure 4 is an end elevation of the member of Figure 3.
[0008] Referring to Figures l and 2, there is illustrated the upper surface board l0 of a workbench, this having therein a number of holes l2 only one of which is shown, and which are spaced at a given modular distance from one another on the board l0. Mounted on the board l0 is a device l4 of the present invention, this including a housing l6 which is generally cylindrical in shape and includes a downwardly extending projection l8 which is a sliding fit in one of the holes l2.
[0009] The housing l6 has an axial recess 20 formed therein, of circular cross section, in which is vertically slidable a plug 22 of cylindrical shape. The plug is urged upwardly by a compression spring 24 engaged in a further recess 28 in the housing.
[0010] As can be seen more clearly in Figure 2, the housing l6 is provided with two aligned bores 30 extending transverse to the axis of the plug 22. The plug itself is provided with an aperture 32 which is aligned with the bores 30 and includes an upper first portion 34 of circular cross section and a lower portion 36 also of circular cross section, but of a smaller diameter, and itself provided with a half female screw thread.
[0011] Slidable through the bores 30 and the aperture 32 is an elongate threaded rod 36. The diameter of the bores 30 and of the first part 34 of the aperture 32 is slightly larger than the outside diameter of the threaded rod 38. The second portion 36 of the aperture 32 has a diameter threadably to engage the threaded rod 38, when the plug 22 is in an upper position as shown in Figure l.
[0012] In fact, the plug 22 can be moved to a first, lower position in which the upper part 34 of the aperture 32 is in direct alignment with the bore 30 and in this condition the elongate rod 38 can be slid easily through the housing to give a coarse adjustment. If one releases the plug 22 it will be forced upwardly by the spring 24 so that the female threaded part 36 engages the screw thread of the rod 38.
[0013] The rod 38 is provided with a pivotal tommy-bar 40 by which it can be rotated, thereby giving a fine adjustment to the rod by this rotation.
[0014] Mounted on the free end of the rod is a workpiece engaging member 42 (Figures 3 and 4). This is of generally L-shaped cross section as seen in Figure 3 including a body 44 having a work engaging surface 46 with a throughbore 48 therein, and a horizontally extending lower foot 50. The throughbore 48 is engagable over a reduced diameter portion 52 at the end of the rod 38. The member 42 can be mounted either so that the face 46 of the workpiece or the face 54 at the end of the foot 50 abuts the workpiece. In this latter condition, only the bottom of the workpiece will be engaged, but this enables a top-surface machining operation, such as a planing operation, to be carried out.
1. A workpiece clamping device for a workbench, comprising a housing having at least
one horizontal bore therein, means for locating the housing on a workbench, a plug
mounted for limited movement in said housing in a direction transverse to said horizontal
bore, an aperture through said plug in substantial alignment with said bore, an elongate
screw-threaded rod extending through said at least one bore and said aperture, the
diameter of said at least one bore being slightly larger than the outside diameter
of the rod, the aperture having a cross section including a first portion having a
screw-thread cooperable with the thread of the rod and a second portion allowing free
movement of the rod longitudinally of the rod, whereby movement of the plug to a first
position allows the rod to slide freely relative to the housing and give coarse adjustment
of the rod and movement of the plug to a second position causing the thread to engage,
so that rotation of the rod can give fine adjustment thereof, and a workpiece engaging
member mounted on, or engagable by, the rod for movement therewith, the rod being
rotatable relative to said member.
2. A device according to claim l, wherein the housing is provided with a cylindrical
projection on its lower surface, this projection being engagable in an aperture in
the workbench.
3. A device according to claim l or 2, wherein the member which is secured to the
free end of the rod is of L shape and can be detachably mounted on the rod to enable
the outside of the vertical wall to engage the workpiece or, alternatively, the inside,
thereby leaving a clearance for the operation of a tool.
4. A device according to claim l, 2 or 3, wherein the rod is provided with means to
facilitate its rotation.
5. A device according to claim 4, wherein said means comprise a pivotally mounted
tommy-bar.