In cutting a mitre j oint it has often been the practice to employ a mitre box which has saw guides and fixed angles to produce a mitre joint of a correspondingly fixed angle, for example, mitred joints at the corners of a rectangular frame would be cut at an angle of 45 °. Mitred joints for other than rectangular frames would need either a separate mitre box for each angle or else a saw guide adjustable with respect to the mitre box. In the latter case the saw line or line of cut requires resetting for the angle of the co-operating adjacent frame part.

In some cases each mitre joint is different from a previously cut joint, for example in the case of cutting mitred joints in coving to fit around the wall/ceiling joint in a room, the fact that the room may not be square either by accident or design, means that often each corner mitred joint is different from the others.

The inventor's earlier International patent application, PCT/GB93/00941, discloses an apparatus for use in cutting a mitre joint in which a pair of workpiece guide boxes can be adjusted symmetrically relative to a saw guide. The guide boxes can be rotated beyond an in-line position to allow both internal and external mitres to be cut.

A disadvantage of the inventor's earlier apparatus is that it is relatively large, heavy and expensive to manufacture.

It is an object of the present invention to provide an apparatus for cutting mitres that mitigates at least some of the aforesaid disadvantages.

According to the present invention there is provided apparatus for use to enable the cutting of external and internal mitre joints, characterised in that the apparatus includes

a pair of adjustable workpiece locating means, each including a base plate and a pair of upstanding support surfaces.

An advantage provided by this invention is that both external and internal mitres can be cut without rotating the workpiece locating means beyond an in-line position.

Preferably the workpiece locating means can be adjusted between a position in which the upstanding walls subtend an acute angle, and one in which they are substantially aligned.

Preferably there is a gap between the forward edge of the upstanding wall and the saw line, enabling a mitre to be cut in a single cutting operation.

According to one embodiment of the invention each adjustable workpiece locating means includes a base plate and an upstanding wall dividing the base plate into an inner portion and an outer portion.

Preferably the inner and outer portions of the base plate have upstanding lips.

Preferably the inner forward corner of the inner portion of the base plate is chamfered at an acute angle to the upstanding wall. Preferably, the forward edge of the outer portion of the base plate is substantially perpendicular to the central wall.

Preferably the base plate is provided with a liner.

According to another embodiment of the invention each adjustable workpiece locating means includes an inner and an outer wall. The inner surface of each of these walls serves as an upstanding support surface.

Preferably the forward edge of the base plate is substantially perpendicular to the inner and outer walls.

Embodiments of the invention will be described, by way of example, with reference to the accompanying diagrams, in which: Figure 1 is a perspective view of a template;

Figure 2 is a plan view of the template in use to determine the angle of a joint between the two conjoined walls of part of a building; Figure 3 is a perspective view of an adjustable mitre guide device; Figure 4 is a plan view of the device in a first configuration; Figure 5 is a plan view of the device in a second configuration; Figure 6 is a sectional view on the line VI-VI of figure 4 with part of a coving in position for cutting; Figure 7 is a plan view of a second embodiment of the device, for use with a jig-saw ; Figure 8 is a perspective view of a third embodiment of the device; Figure 9 is a plan view of the third embodiment of the device in a first configuration; Figure 10 is a plan view of the third embodiment of the device in a second configuration; Figure 1 la and 1 b are sectional views on the line XI-XI of figure 8 with part of a coving in position for cutting; and Figures 12a, b, 13a, b, c and 14a, b are plan, side and end views of further embodiments of the device, that include a chop saw.

In figures 1 and 2, there is shown a template 2 which comprises arms 4,6 hinged about an axis 8 and adapted to be clamped together by a screw and wing nut 10. Each arm has secured thereto and depending downwardly therefrom a pair of pegs 12 each formed with a cylindrical shank 14 and a tapered lead portion 16.

In figure 2 the template is shown set at an angle to coincide with the angle between a pair of conjoined walls W. To arrive at such a setting, the screw and wing nut device is loosened and the template is offered up to the walls, opened until the arms are in continuous contact with both walls after which the wing nut is retightened and the template removed. The template is also shown set to form a reflex or external angle with

a pair of conjoined walls W1. Thus the template may be adjusted to conform to both internal and external angles.

A mitering device 18, shown in figures 3,4 and 5, comprises a base board 20. A Tee-slot 22 is formed in the base board 20 and an adjusting member 24 is slidable longitudinally within the Tee-slot. The adjusting member 24 and the associated adjusting mechanism are substantially as described in International patent application PCT/GB93/00941, the content of which is incorporated by reference herein.

Workpiece locating means are provided in the form of a pair of guide boxes 36 each of which includes a central upstanding wall 38 and a base plate 40 that extends laterally on both sides of the central upstanding wall 38. The base plate 40 is substantially rectangular and includes a forward edge 40a, a rear edge 40b, an inner edge 40c and an outer edge 40d. The base plate 40 is divided by the upstanding wall 38 into an inner portion 41a and an outer portion 41b. A shank portion of a bolt 42 passes through a hole 44 formed in the base plate 40. The bolt also passes through a transverse slot (not shown) in the base board 20 and is slidable therein, as described in PCT/GB93/00941. Each guide box 36 is mounted for pivoting about the axis of a pivot pin 54 which is fixed, for example by welding, to the forward end of the base plate 40 and is freely pivotable in a hole formed in the adjusting member 24. The central wall 38 of each guide box is formed with two holes 56 in the upper surface. Each of the inner and outer edges 40c, 40d of the base plate 40 terminates with an upstanding lip 58. The base plate 40 is provided with a liner 60, the upper surface of which lies in the same horizontal plane as the upper surface of a pair of longitudinal ribs 62, which extend upwardly from the adjustable member 24 to define a saw clearance slot 64. The liners provide access to the heads of the bolts 42 by a suitable ring-spanner or socket spanner.

The forward comer 65 of the inner portion 41 a of the base plate 40 is chamfered at an acute angle to the central wall 38, whilst the forward edge 40a of the outer portion 41b of the base plate 40 is perpendicular to the central wall 38. This enables the angle between the guide boxes to be adjusted symmetrically between a position in which the

central walls subtend an acute angle of, for example, 20°and one in which they subtend an angle of 180 ° : i. e., they are aligned.

As described in PCT/GB93/00941, the adjusting member 24 can be adjusted to move forwardly or rearwardly along its Tee-slot 22. In so doing, the pins 54 also move forwardly and rearwardly causing the guide boxes to rotate about the shanks of the bolts 42. Due to the restraint of the pins 54 in the longitudinal direction of motion, the bolts 42 are caused to slide laterally within the confines of the slots, resulting in a change of angle of the guide boxes with respect to the median line of the baseboard, i. e. the line along which the saw cut is made. Thus the line of cutting remains constant while the angle of the guide boxes is simultaneously and symmetrically adjustable with respect to that line.

Two pairs of roller-type saw guides 66 defining a saw line 66A are rotatably mounted on the adjusting member 24, although an alternative form of saw guide may be used instead.

The central upstanding walls 38 each have a forward edge 68 that is spaced from the saw line 66A defined by the saw guiding means 66 and from the pivotal connections 54, so that a gap is defined between the forward edge 68 of the upstanding wall and the saw line 66A. The gaps permit the upstanding walls 38 to be angularly adjusted with the workpiece locating means 36, for enabling cutting of internal and external mitre angles, without the upstanding wall forward edges 68 crossing the saw line 66A. The gaps also permit a workpiece positioned on one workpiece locating means 36, whilst the latter is adjusted for cutting internal mitre angles, to extend over the saw line and through the gap of the other workpiece locating means 36, without being blocked by the upstanding wall 38 of the other workpiece locating means 36.

In order to cut an internal mitre, after the template has been adjusted and set to the angle between the walls W as described earlier with respect to figure 2 it is then taken from the walls and laid on the top surface of the central upstanding walls 38 of the guide boxes 36, the pegs 12 of one arm of the template being gently inserted into the two holes 56 in the

top of the wall of one of the guide boxes. The guide boxes are then adjusted until the pegs in the other arm are aligned with the holes in the other guide box.

Having thus set the angles of the guide boxes, the bolts 42 are tightened by a suitable ring spanner or socket spanner in order to rigidly lock them in an operative position. The guide boxes are thus set at the same angle as the walls W and the template is then removed. A section of coving C is inserted into one of the guide boxes as indicated in figure 6 so that it rests on the inner portion of the base plate 41 a and extends therefrom at its foremost end over the median line of the base board. A saw is then guided between the roller-type saw guides 66 to mitre one end of the coving. The operation is repeated with a further section of coving using the other guide box and the two coving sections are thus provided with mating surfaces which are appropriate for the angle of the conjoined walls.

A similar procedure is used for cutting external mitres, the difference being that the coving section C'is placed on the outer portion of the base plate 41b so that it rests against the opposite side of the upstanding wall 38.

When smaller sections of coving than that shown in figure 4 are being cut a filler strip of wood is inserted adjacent to the upstanding lip 58 in order to ensure that the workpiece maintains its correct angle within the guide box.

In a further arrangement, not shown, the upstanding lips 58 may be extended upwardly beyond that shown in the drawings and a threaded screw passed therethrough to form part of a screw clamp to hold the workpiece firmly against the vertical wall 38 of the guide box 36.

It is possible to locate the coving in the guide boxes manually during sawing without the need for mechanical clamping means or even the use of the upstanding lips 58 or filler strips, although those arrangements are preferable.

In an alternative arrangement, shown in figure 7, a power operated jig-saw may be used instead of a conventional hand saw or tenon saw. In such an arrangement, the roller type

saw guides 66 are removed and replaced by vertical columns 70 which support a horizontal guide plate 72 extending above the adjusting member 24. The guide plate has upstanding lips 74 extending longitudinally along the edges of the plate to provide means for guiding the sole plate of the saw and the vertically reciprocating blade passes through a central slot 76 formed in the guide plate.

In the above arrangement the saw used may be a hand saw or a jig saw guided between the lips 74. Alternatively a circular saw may be used in a similar manner to a jig saw, its sole plate being guided by the lips 74.

In an alternative arrangement a chop saw 77 may be used. The chop saw 77 may be mounted in different positions on the device, for example, it may be mounted in a fixed position on the base 20 (figures 12a and 12b), on the horizontal guide plate 72, which has been extended for this purpose (figures 13 a, 13b and 13c), or on the adjustable member 24 (figures 14a and 14b). The chop saw may be mounted in any of these positions by means of bolts 78, thereby fixing the chop saw into position. Alternatively, the chop saw may be welded into position, or fixed in any other way. The chop saw may include an operating handle (not shown) for lowering the blade into position for cutting the coving.

A third embodiment of the device is shown in figures 8 to 11. The mitering device is similar in some respects to the first embodiment shown in figures 3 to 5, and similar reference numbers will be used where appropriate.

The device 180 includes a base board 20. A Tee-slot 22 is formed in the base board 20 and an adjusting member 24 is slidable longitudinally within the Tee-slot 22.

Workpiece locating means are provided in the form of a pair of guide boxes 136, each of which includes an inner upstanding wall 138a and an outer upstanding wall 138b on either side of a substantially rectangular base plate 140. The forward edge of the base plate 140a is perpendicular to the inner and outer walls 138a, 138b. A shank portion of a bolt 142 passes through a hole 144 formed in the base plate 140. The bolt passes through a transverse slot (not shown) in the base board 20 and is slidable therein. Each guide box is mounted for pivoting about the axis of a pivot pin 154 which is fixed, for

example by welding, to the underside of the base plate 140, directly below the forward end portion of the inner wall 138a, and is freely pivotable in a hole formed in the adjusting member 24. The inner wall of each guide box is formed with two holes 156 in the upper surface. The upper surface of the base plate 140 lies in the same horizontal plane as the upper surface of a pair of longitudinal ribs 62, which extend upwardly from the adjustable member 24 to define a saw clearance slot 64.

The adjusting member 24 can be adjusted to move forwardly or rearwardly along its Tee- slot 22. In so doing, the pins 154 also move forwardly and rearwardly causing the guide boxes to rotate about the shanks of the bolts 142. Due to the restraint of the pins 154 in the longitudinal direction of motion, the bolts 142 are caused to slide laterally within the confines of the slots, resulting in a change of angle of the guide boxes with respect to the median line of the baseboard, i. e. the line along which the saw cut is made. Thus the line of cutting remains constant while the angle of the guide boxes is simultaneously and symmetrically adjustable with respect to that line. The angle subtended between the axes of the guide boxes can be adjusted between an acute angle of, for example, 20° and an angle of 180 °, at which the guide boxes are aligned.

Two pairs of roller-type saw guides 66 defining a saw line 66A are rotatably mounted on the adjusting member 24, although an alternative form of saw guide may be used instead.

The method of cutting a mitre is broadly similar to that described above for the first embodiment, however, in order to cut an internal mitre, a section of coving C must be inserted into one of the guide boxes as indicated in figure 1 la so that it rests against the outer upstanding wall 13 8b. An external mitre can be cut by inserting a section of coving C'into one of the guide boxes as indicated in figure 1 lb so that it rests against the inner upstanding wall 138a.

Although the above non-limiting examples show and describe saw guiding means (66) attached to adjusting member 24, such guide means may, without departing from the invention, be attached to the base board 20 instead.

If desired the upper face of the base board may be provided with markings or graduations in the form of a protractor to allow manual setting of the guide boxes without resorting to the use of a template.

The specific embodiments of the invention have been described with respect to cutting mitres for a coving. They may of course be used for cutting mitre joints for any purpose and in any material, for example skirting boards, picture rails, architraves, and picture frames having non-rectangular frames.

The guide boxes, having been set symmetrically to the required angle of the mitre, may be used for the purpose of gluing or otherwise fixing together the two components of the mitre.

In an alternative arrangement, not shown, the base board may be part of, or may constitute the working surface of a work bench. It is found to be particularly useful when it is part of a portable work bench of the type readily available and marketed under the trade mark "Workmate"by Black & Decker Limited.

Various other modifications of the device are envisaged, for example, the hole and peg arrangement between the upstanding wall (38,138a) and the template (2) could be reversed. Similarly the hole and peg arrangement between the base plate (40,140) and the adjusting member (24) could be reversed.

In order to reduce the number of components required to produce the device 180, pivot pins (154) can be fixed to the underside of the base plate at both the forward and rear end portion of the inner wall (138a), allowing identical components to be used for both guide boxes.

The liner 60 may be separate from the base plate (40) or may be part of a moulding incorporating the base plate (40).

The device may be made of any suitable material.