GB2264892A - Workcentre - Google Patents

Abstract

A workcentre (10, Figure 1, not shown) has a table (12) and frame (14a, b, c, Fig. 1, not shown) capable of moving a tool (20, Fig. 1, not shown) through three orthogonal directions, (X, Y, Z) by means of a computer (41, Fig. l, not shown), controlling driving motors (30a, b, c, Fig. 1, not shown). The worktable (12) has first and second clamping means (104, 114) to hold two pairs of workpieces (101, 102) so that dovetail slots (and other joining mortices and tenons) can be cut in the workpieces and a box section (figure 7, not shown) be formed. With this arrangement automatic cutting is feasible even for irregular dovetails. <IMAGE>

Description

WORKCENTRE This invention relates to a workcentre and particularly to a wood-machining workcentre of the type comprising a frame mounting a router or like tool for movement in the frame in two, or more likely three, orthogonal directions.

The frame comprises two (or three) linear elements each mounting a carriage slidable along the element under the action of a motor. In frames moving in three orthogonal directions, the first element is fixed with respect to a worktable, the second element is mounted perpendicularly with respect to the first element and is mounted on the carriage of the first element; and the third element is mounted perpendicularly to both the first and second elements on the carriage of the second element. A tool is mounted on the carriage of the third element.

Each carriage is driven along the element by a motor and several options are available for connecting the motor to the carriage. For example, the motor may be mounted on the carriage and acting against the element.

Alternatively, the motor may be mounted on the element and may drive the carriage through a worm-drive screw or by a belt and pulleys on the carriage.

Movement of the tool may be under the control of a computer performing the individual movements according to direct operator control or a sequence of movements according to pre-programmed control.

The computer controls movement of each motor, instructing them to move simultaneously and at different rates, so that not only are diagonals feasible but so also are curves.

A type of cut that is frequently required in wood (when the tool being used is a router) is the cutting of two pieces which are to be joined together at right angles with respect to each other. Dovetail joints fall in this category and normally require a special jig by means of which a guide on the router can follow a predetermined course and can cut the mortices and tenons with the requisite accuracy so that a good joint can be made.

Those skilled in the art will appreciate the difficulties associated with dovetail joint cutting, even with the aid of jigs, and the skill required to make good joints.

It is therefore an object of the present invention to provide a workcentre which is capable of effecting joint cuts which requires little or no skill on the part of the operator to make good joints.

It is a further object of the present invention to enable several workpieces to be cut simultaneously or in quick succession one after the other so that complete components, such as for example, the four sides of a drawer unit, can be formed with few individual operations.

In accordance with this invention there is provided a workcentre for cutting mortise and tenon joints in workpieces, the workcentre comprising:a worktable; a frame; a tool mounting means on the frame, said frame being adapted to move said tool mounting means in first, second and third orthogonal directions; motors, mounted on said frame and driving said tool mounting means in said directions; a computer, including operator input means and controlling said motors according to a program in the computer and adapted to control movement of the tool mounting means with respect to a workpiece positioned on the worktable; first clamping means on said table enabling clamping of a first pair of elongate substantially rectangular cuboid workpieces so that one end of said first workpieces is substantially parallel said first and second directions; second clamping means on said table enabling clamping of a second pair of elongate substantially rectangular cuboid workpieces so that one end of said second workpieces has edges substantially parallel said third direction; and a routing tool mounted on said tool mounting means; said program being adapted to move said tool from one or more operator input start positions along predetermined paths resulting in tenons being cut in said first workpieces and mortises being cut in said second workpieces, whereby said workpieces may be jointed together to form a box section.

Preferably said first pair of workpieces are clamped back to back with their ends flush with one another.

Preferably support means is provided on which said first pair can be positioned in said first clamping means, whereby their position in said third direction can be assured.

Preferably said second pair of workpieces are disposed on a raised sub-table fixed on the worktable, the sub-table lying parallel said first and second directions, said workpieces lying side by side separated by a separation member.

Preferably a guide is fixed to said table, the guide comprising a base element and a guide element, the guide element being adjustable between two positions, in a first of which it extends in said third direction above the plane of the sub-table, faces said sub-table and is parallel said third direction, and in the second of which it is below said plane.

Preferably said second clamping means enables said second pair of workpieces to be clamped with said end parallel said second direction, as well as parallel said third direction.

In this event, said guide element is also parallel said second direction.

Thus with this arrangement, an operator first positions said workpieces on the workcentre as described above, then he/she identifies for the computer a start position for said first pair of workpieces and commences running of the program in the computer which controls said motors to move the tool along said path cutting tenons in said first workpiece. Next the operator identifies for the computer a start position for said second pair of workpieces. If the width and length of said second workpieces are known then these can also be input to the computer and then the computer has all the information it requires to cut mortises in each end of both workpieces following a pre-programmed path.Otherwise, start positions must be identified for each end of the workpieces, and from the or each start position, mortises can be cut as the tool follows the predetermined path under computer control.

Usually the same, even pattern of the mortises and tenons would be cut in the first and second workpiece pairs so that every joint in the box section would be identical. However, the present invention is not restricted in that respect. Opposite ends of said first pair of workpieces can be given different patterns of tenons, while one of said second pair of workpieces can be given mortises matching one set of tenons while the other of said second pair can be given mortises matching the tenons of the other end of said first pair of workpieces.

Moreover, there is no requirement that the pitch of the mortises/tenons be regular since they are not being cut together.

Said start position may be input to the computer by means of direct operator control of the motors through the computer, the operator by said means positioning the tool in the start position and notifying the computer accordingly.

Alternatively, said start position may be interpolated by the computer, the operator by means of direct control of the motors through the computer positioning the tool against three orthogonal sides of the workpieces.

In either event the tool may have a right cylindrical bit adapted to be positioned against points or surfaces for position identifying purposes, the computer taking into account the thickness of the bit in calculating a centre position thereof.

The invention is further described hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a workcentre according to the present invention; Figure 2 is a top view of the workcentre of Figure 1; Figure 3a and b are a top view and front view (partly in section) respectively of a second clamping means in accordance with the present invention; Figures 4a and b are a side sectional view (on the line A-A in Figure 4b) and top view respectively of a first clamping means in accordance with the present invention; Figures 5a and b are a side view and a top view of a guide for use with said second clamping means; and Figures 6a and b are a top and side view respectively of a preferred embodiment of said second clamping means.

In Figure 1 of the drawings, a workcentre 10 comprises three box section type girder tracks or supports 14a, b and c arranged in three orthogonal directions Y, X, Z respectively. Each support mounts a carriage (not shown) and of which plate parts 16a, b, c project through top slots 18a, b, c of each support respectively. Plate 16a mounts one end of the support 14b whose other end is supported on a rail 15. The plate part 16b supports the track 14c and the plate part 16c carries a tool 20 for carrying out cutting operations on a workpiece 22 mounted on a table 112 of the workcentre 10.

Each carriage (36, for example - see Figure 2) can slide along its support and is driven by a rotating screw 38 in a nut 39 fixed in the carriage. Each support 14a, b, c has its own motor 30a, b, c driving its own screw and thence its own carriage. Thus the tool 20 is movable in three dimensions to affect various cutting operations on the workpiece 22. The motors 30 are controlled by a computer 41 and by means of which an operator can effect specific movements under direct control or a sequence of movements, under programmed control. However, such control means and methods are not the subject of the present invention, save only that the present invention requires that the computer be capable of manoeuvering the tool along a predetermined and accurate path so as to effect intricate cutting operations.However, such capability is already available and consequently the particular manner employed does not require description here.

The table 12 comprises a plurality of planks 13 in the form of aluminium extruded sections laid side by side on two supports 40, 42 (see also Figure 2). First and second clamping means 104, 114 are provided on the table 12 as described further below.

One plank, 13b has a section cut from it between the supports 40, 42. To support the cut ends 41 of the plank 13b, connecting links 44 join those ends to adjacent planks 13a, c. Over the gap between the cut ends 41 a first clamping means 104 is fixed. Said clamping means comprises a fence 46 and bar 48, two bolts 50 being fixed to the fence and having cam levers 52 screwed to their ends. The bar 48 is fixed by bolts 49 (see Figure 4a) to the table 12. Operation of the cam levers 52 presses the bar 48 towards the fence 46 clamping first workpiece pair 101 between them.

The workpiece pair 101 pass through the gap between the ends 41 of the cut plank 13b and their ends below the table 12 are supported on a support 59 (see Figure 1) suspended between braces 61 for legs 63 of the table 12.

Moreover, the workpiece pair is positioned against one of the bolts 50 (the left hand one in Figure 2) so that it should be feasible to overturn the workpiece pair and return their ends to the identical co-ordinate position employing the support 59 (and any required shims between) and the same bolt 50 as guides.

To one side of the first clamping means 104 is disposed second clamping means 114. This comprises two clamp bars 62 on clamp bases 64 (see Figures 3a and b).

On the clamp bases 64 is a sub-table 12' having separation members 66 formed thereon. The clamp bars are connected to the clamp bases at their respective ends by bolts 68 received in the bases 64 and on which are screwed clamp levers 70. Operation of the levers 70 presses the clamp bars against their bases, clamping a second workpiece pair 102 between them.

Both first and second clamping means are accurately positioned on the table 12 so that the workpieces located in and by them are square with respect to the X, Y, Z axes. Thus the first clamping means has guide faces which ensure that the ends of the workpiece pair 101 are parallel the first and second directions (Y and X respectively). Similarly, the second clamping means ensures that the ends of the workpieces 102 are parallel the first and third directions (Y and Z respectively).

In the case of the first clamping means, this is assured by faces of the fence 46 and bar 48. In the case of the second clamping means, this is assured by the separation members 66 against which each workpiece 102 is butted. To ensure that the ends of the workpieces 102 are in line with each other, a separate guide element is required. (One such element is described further below with reference to Figures 5a and b).

Referring now to Figures 3 and 4; after the workpiece pairs 101, 102 have been secured in place, as described above, they are first checked for squareness.

Once the clamping means 104, 114 are correctly positioned this procedure should become superfluous during repeated operation. However, alightment is easily checked by running a tool cutter or other measurement bit in the tool 20 along one axis at a time adjacent the workpieces 101, 102. If there is no misalignment, then the separation of the tool from the workpieces in the two other coordinate axes should remain the same.

Any misalignment noted in this way should be taken up by the use of shims or other adjustment of the first and second clamping means.

When aligned correctly, the tool of the workcentre is positioned at any convenient start position. This is best at point S1 which is the reference position for the workpiece pair 101 in the first clamping means 104, i.e.

in the angle between the bar 48 and bolt 50. This start position S1 must however be the correct position for the program in the computer 41. That program is arranged to move the tool 20 along a path P1 so that tenons 72 are cut in the ends of the workpieces 101. Needless to say, these tenons in each workpiece 101a and b are mirror images of each other. However, they need not have constant pitch nor have constant depth. The computer can centralise the tenons if it knows the width of the workpieces. The shape of the tenons is purely a programming task.

On the other hand, the computer must have means of recording what tenons have been cut because its next function is to cut mortises 74 in the workpieces 102.

Again it is convenient to notify the computer of a start position, such as S2 so that from that position the computer can control movement of the tool 20 along path P2 to cut the requisite mortises (the drawings are not to scale).

Path P2 can end as indicated in the drawings and each end of each workpiece 102 a, b can be cut separately. But there is no reason why the computer cannot be arranged to cut all four ends one after another in a single path starting at S2 if the widths and lengths of workpieces are known.

None of the mortises 74 in the four ends need match those in the other ends, except that the tenons in two ends of the first workpieces are identical and consequently two pairs of ends of the workpieces 102 must likewise be identical to match the identical tenoned ends of the workpieces 101. In practice, as will be evident from the discussion of Figure 7 below, matching mortises are usually cut at the ends of each workpiece so that the workpieces 102a, b are not necessarily identical.

While the mortises 74 are being cut in the workpieces 102, this is a convenient time to turn over the workpieces 101 in the first clamping means to make ready the other ends of those workpieces for tenon cutting as described above when the mortise cutting of the workpieces 102 is completed.

The start position S1 and S2 is of course important for accurate cutting and this is easily identified to the computer simply by positioning manually at the start position the tool 20 and notifying the computer accord ingly. In this respect, it is to be noted that the start position is a three-dimensional location (at least insofar as dovetail slots are concerned) because the depth of cut is equally as important as the size and pitch of the respective mortises and tenons.

Another way of locating the start position for the computer is to identify the co-ordinates (x, y, z) of the start position (say, position S1) by touching first side 126 of the first workpieces 101a to give the x co-ordinate of the start position; then by touching edge 128 of the first workpiece to give the y co-ordinate; and then by touching end 132 of the first workpiece 101a to give the z co-ordinate of the start position. Account will have to be taken of the dimensions of the measuring probe which could in its simplest form be the tool bit inserted in the tool 20; this is certainly preferred for the final z c-ordinate.

In Figures 5a and b a guide 150 is illustrated.

This is fixed in front of the workpieces 102 and is used to ensure exact positioning in the Y direction of both workpieces.

The guide 150 comprises a guide base 152 and guide element 154. The base is fixed to the table 12 by bolts 156 and nuts 158 captivated in slots 112 between the planks 13 of the table 12. The guide element 154 floats above the base 152 on pins 160, 162. Pins 160 ensure exact location in the Z direction of the element with respect to the base. Pins 162 prevent the element from coming right off the base.

A cam lever 164 is pivoted in the element about axis 166 and has a cam 168 which bears against a cam surface 170 in the floor of the base 150. Operation of the lever 164 raises and lowers the guide element with respect to the base between two positions. In the raised position shown in Figure 5a, the guide element 154 is at the level of the workpieces 102a, b. Consequently, if guide surface 172 of the guide element 154 is accurately positioned so that it is parallel the x axis (and of course the separation members are accurately located so that they are parallel the Y axis) then the squareness and position of the workpieces 102 can be assured.

However, it is because it is necessary to work on the ends of the workpieces 102, that the floating guide element arrangement is provided. In its second lowered position, as shown in Figure 5b, the lever 164 is pivoted down out of the way and confined within a slot 174 in the guide element 154. At the same time, the guide element 154 is lowered so that the ends of the workpieces 102 are fully exposed for machining operations. This is a convenient and quick way of accurately locating the workpieces without getting in the way of the path of the tool.

Figures 6a and b illustrate a different preferred embodiment of the second clamping means 114'. Here the levers 70' are simply inverted to more conveniently locate them, and the separation members 66 have been replaced by floating members 66' on each clamp base 64'.

A guide square 180 is fixed to the table 12 to one side of the second clamping means 114' and against which the first workpiece 102b is positioned. The second workpiece 102a is then positioned against the floating members 66' pressing them against first workpiece 102b.

Both workpieces are also pressed against the guide 150 so that their respective positions and squareness on the sub-table 12" is assured prior to tightening the levers 70'. In this arrangement the start position S2 may be moved as shown in Figure 6a.

Finally turning to Figure 7, a completed box section 200 is shown having first workpieces 101a and b joined to second workpieces 102a and b by different dovetail joints. It is to be noted that not only is irregular pitch quite feasible with the present arrangement, as shown for example at 202, but also irregular depth is feasible, as shown at 204. All this is possible with the same tool bit, although, of course, the angle of the dovetail cannot be altered without changing the bit.

A typical application for an arrangement as shown in Figure 7 is in drawer units where side 102a, for example, will form the front panel. In this event, the dovetail joints at both corners of the front should be aesthetically pleasing and be identical with each other. However, no such requirements exist for the rear corners.

Consequently the parts 101 would have different ends but be identical images of each other, while parts 102 would have identical ends but be different from each other.

Claims (11)

1. A workcentre for cutting mortise and tenon joints in workpieces, the workcentre comprising: a worktable; a frame; a tool mounting means on the frame, said frame being adapted to move said tool mounting means in first, second and third orthogonal directions; motors, mounted on said frame and driving said tool mounting means in said directions; a computer, including operator input means and controlling said motors according to a program in the computer and adapted to control movement of the tool mounting means with respect to a workpiece positioned on the worktable; first clamping means on said table enabling clamping of a first pair of elongate substantially rectangu lar cuboid workpieces so that one end of said first workpieces is substantially parallel said first and second directions;; second clamping means on said table enabling clamping of a second pair of elongate substantially rectangular cuboid workpieces so that one end of said second workpieces has edges substantially parallel said third direction; and a routing tool mounted on said tool mounting means; said program being adapted to move said tool from one or more operator input start positions along predetermined paths resulting in tenons being cut in said first workpieces and mortises being cut in said second workpieces, whereby said workpieces may be joined together to form a box section.

2. A workcentre as claimed in claim 1, in which said first pair of workpieces are adapted to be clamped back to back with their ends flush with one another.

3. A workcentre as claimed in claim 1 or 2, in which support means is provided on which said first pair can be positioned in said first clamping means, whereby their position in said third direction can be assured.

4. A workcentre as claimed in any preceding claim, in which said second pair of workpieces are adapted to be disposed on a raised sub-table fixed on the worktable, the sub-table lying parallel said first and second directions, said workpieces lying side by side separated by a separation member.

5. A workcentre as claimed in claim 4, in which a guide is fixed to said table, the guide comprising a base element and a guide element, the guide element being adjustable between two positions, in a first of which it extends in said third direction above the plane of the sub-table, faces said sub-table and is parallel said third direction, and in the second of which it is below said plane.

6. A workcentre as claimed in any preceding claim, in which said second clamping means enables said second pair of workpieces to be clamped with said end parallel said second direction, as well as parallel said third direction.

7. A workcentre as claimed in claims 5 and 6, in which said guide element is also parallel said second direction.

8. A workcentre as claimed in any preceding claim, in which said start position is input to the computer by means of direct operator control of the motors through the computer, the operator by said means positioning the tool in the start position and notifying the computer accordingly.

9. A workcentre as claimed in any of claims 1 to 7, in which the said start position is interpolated by the computer, the operator by means of direct control of the motors through the computer positioning the tool against three orthogonal sides of the workpieces.

10. A workcentre as claimed in claim 8 or 9, in which the tool has a right cylindrical bit adapted to be positioned against points or surfaces for position identifying purposes, the computer taking into account the thickness of the bit in calculating a centre position thereof.

11. A workcentre substantially as hereinbefore described with reference to Figures 1 to 5, or as modified in Figure 6, of the accompanying drawings.