GB2264893A - Workcentre - Google Patents

Abstract

A workcentre (10, Figure 1) has a table 12 and frame (14a, b, c) capable of moving a tool (20) through three orthogonal directions, (X, Y, Z) by means of a computer (41) controlling driving motors (30a, b, c). The worktable (12) has first and second clamping means (114, 104, Figure 2 not shown) to hold two workpieces (101, 102, Fig. 2, not shown) at right angles to each other so that dovetail slots (and other joining mortices and tenons) can simultaneously be cut in the workpieces. <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 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.

In accordance with this invention there is provided in its broadest aspect a workcentre comprising a frame and a worktable, the frame mounting a tool mounting means adapted for movement over the worktable in three orthogonal directions and adapted to receive a routing tool; a computer, controlling movement of said tool mounting means and having operator input means and a program; and clamping means adapted to clamp two workpieces to the worktable, said workpieces to be joined together by a mortise and tenon joint, the requisite cuts thereof to be machined by said workcentre, said program being adapted to direct movement of the tool mounting means through a predetermined path from a start position input to the computer by an operator through said operator input means so that said tool cuts mortises and tenons in said workpieces.

In accordance with another aspect of this invention there is provided a workcentre for cutting mortice/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 elongate substantially rectangular cuboid workpiece so that one end of said first workpiece has edges substantially parallel said first and second directions;; second clamping means on said table enabling clamping of a second elongate substantially rectan gular cuboid workpiece so that one end of said second workpiece has edges substantially parallel said second and third directions, said end of the second workpiece abutting the side of the first workpiece so that said end of the first workpiece is substantially flush with a top side of said second workpiece and said second workpiece being offset in said second direction with respect to said first workpiece by an amount equal to the pitch of the mortise and tenon joint to be cut in said workpieces by the workcentre; and, a routing tool mounted on said tool mounting means; said program being adapted to move said tool from an operator input start position along a predetermined path resulting in tenons being cut in said first workpiece and mortises being cut in said second workpiece, whereby said workpieces may be joined 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.

Where the work table comprises a series of planks laid side by side between two support elements, said first clamping means may comprise a pivotable section of one plank between said support elements, the pivotable section being pivotable between a first position in which it is flush with the other planks and a second position in which it is perpendicular to its first position and in which it opens a gap in the worktable between said section and an adjacent plank and through which gap said first workpiece may be inserted and clamped against said section.

Preferably said section has at either end thereof a plate by means of which said section is pivoted to said support elements, at least one of the plates having an arcuate slot through which a pin of a clamp passes, which clamp is fixed to said elements and is adapted to clamp said plate and hence the section with respect to the worktable. Any convenient means may be provided physically to clamp the first workpiece to the section and accordingly said first clamping means may further comprise a bar mounted on pins fixed in said section near its ends and cam means arranged on said pins to press said bar towards said section to clamp a workpiece positioned therebetween.

Said second clamping means, where the worktable comprises said series of planks laid side by side between said two supports, preferably comprises at least two of said planks adjacent said section being mounted on end plates adjustably fixable with respect to said supports so that said at least two planks form a sub-table capable of being raised and lowered with respect to the worktable. Preferably, the sub-table is capable of being raised at least to the level of said section when it is pivoted through a right angle from said flush position.

Said second clamping means conveniently further comprises a bar mounted on pins fixed in said sub-table and cam means arranged on said pins to press said bar towards the sub-table to clamp a workpiece positioned therebetween.

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 front view of part of the workcentre of Figure 1; Figure 3 is a plain side view of part of the workcentre of Figure 1; Figure 4 is perspective view of two workpieces cut by a workcentre; and Figure 5 is a top view of the workpieces in Figure 4.

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 of which 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 12 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 moveable 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 Figures 2 and 3). First and second clamping means 104, 114 are provided on the table 12 as described further below.

At one point in the table 12, one plank 13b is cut between the supports 40, 42 (the ends 41 thereof being supported by connecting bars 44 secured to adjacent plank 13a. The central section 46 of the plank 13b is pivoted to the supports 40, 42 by plates 48, 50 about pivot axis 52. The plate 50 has an arcuate slot 54 whose radius of curvature is centred on axis 52. A clamp 56 is fixed in a member 58 secured to the support 40. The clamp 56 has a handle 60 operable from the side of the table 12. The clamp 56 has a bolt head 62 passing through the slot 54 and which clamps the plate 50 to the member 58 when the handle 60 is tightened.

Thus the section 46 can be pivoted from the vertical position shown in Figures 2 and 3, through a horizontal position in which it is flush with the other planks 13 and to a reverse vertical position.

In either vertical position, the section 46 opens a gap 64 in the table 12.

Most of the planks 13 are secured to the supports 40, 42 by connection elements 66 screwed to the supports by screws 68. The planks have longitudinal undercut slots 70 adapted to captivate nuts 72. Bolts 74, passing through a flange 76 of the connection elements 66, clamp the planks 13 to the connection elements 66. Indeed, this is how the ends of the plank 13b, along with plank 13a, are connected to the supports.

However, next to the plank 13b with its pivoting section 46, the planks 13c and 13d are secured on the supports 40, 42 by modified connection elements in the form of end plates 66'. These are not connected to the supports by screws but by clamps 68' which are operable from the side of the table 12. The clamps are bolts passing through slots 78 in the end plates 66' which thereby enable vertical adjustment of the planks 13c and d and which together thus constitute an adjustable subtable 12' which may be raised as shown in Figure 2 or lowered so that it is flush with the rest of the table 12.

Thus both the pivoting section 46 and sub-table 12' can be rendered flush with the table 12 so that the workcentre 10 can be operated in a normal mode. However, when it is decided to cut dovetail joints or other mortise and tenon joints in first and second workpieces 101, 102 then the table 12 is placed in the position shown in Figure 2 and the clamps 60, 68' are tightened.

The second workpiece 102 is laid on the sub-table 12'. Then a clamp bar 106 is loosely engaged with the workpiece. Two cam levers 108 at either end of the clamp bar 106 are screwed onto a bolt 110 captivated in the slot 112 between planks 13c, 13d. A spring 113 (not visible) biases the clamp bar away from the sub-table 12'.

The second workpiece 102 is passed through the gap 64 and loosely secured to the back or underneath of section 46 by a like clamp bar 106'. Cam levers 108' are similarly screwed onto bolts 110'. Bolts 110' pass through holes formed in the section 46. Furthermore, springs 113' likewise bias the clamp bar 106' away from section 46.

Turning now to Figures 4 and 5, the art of cutting dovetails in two pieces of wood to be joined at right angles is well-known. However, for the sake of completeness a short description is given here. One method of cutting mortises 120 in the second workpiece 102 and tenons 122 in first workpiece 101 is to position them as shown in Figures 4 and 5. That is to say, at right angles to one another with the end of the first workpiece flush with the top side of the second workpiece and with an offset 124 equal to the pitch L of the finished joint.

The outsides of the finished joints are arranged towards the inside for cutting.

A router is then fitted with a dovetail cutter and moved from a start position S along path P. This cuts the mortises 120 and tenons 122 as shown in the drawings.

Assuming that the correct path has been followed and the depth of cut D is matched to the pitch L, then, when the first workpiece is folded up with respect to the second, the tenons 122 should be a perfect fit in the mortises 120 and a good, tight joint should be made. However, even with the best jigs available, by which to follow the path P, this is still a highly skilled operation which is not easily accomplished.

However, in a workcentre according to the present invention, almost perfect dovetails can be cut with relative ease and little skill. This is achieved by two features in particular. First is the clamping arrangement provided by said first and second clamping means 104, 114. In this regard, the first and second clamping means comprise raisable sub-table 12' and pivotable section 46' respectively, as well as their respective clamp bars and cam levers. Together, these enable two workpieces to be secured together on the worktable 12 in the correct orientation for dovetail cutting as described above.

Second, is the fact that the computer is easily programmed, not only to follow the path P from a start point S, but also to calculate that path given the requirement to match the pitch L against the depth of cut D for the given angle of the dovetail. Furthermore, the start position S is all the information the computer requires if the workpieces 101, 102 are accurately aligned with respect to the X, Y and Z co-ordinates.

This 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 co-ordinate 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.

Another feature of the present invention is that it is a simple matter to inform the computer as to the widths W of the workpieces so that the computer can calculate where to make the first cut C so as to equalise the lip 124 at each end of the first workpiece 101. The width W also tells the computer where to finish path P at F.

The start position S is easily identified to the computer simply by manually positioning there the tool 20 and notifying the computer accordingly. However, another way is to identify the co-ordinates (x, y, z) of the start position by touching first side 126 of the first workpiece 101 to give the x co-ordinate of the start position; then by touching end 128 of the first workpiece (or side 130 of the second workpiece 102) to give the y co-ordinate; and then by touching side 132 of the first workpiece 101 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 co-ordinate.

Moreover, if the side 130 of the second workpiece is employed to input the y co-ordinate of the start position, account will also need to be taken of the thickness of the workpiece 102. However, none of these matters pose any difficulties for a competent programmer.

Finally, it is to be noted that other than dovetail joints could be cut using a workcentre according to the present invention. Moreover, the exact location of the start position is purely a matter of choice and convenience and need not be at the point S indicated in the drawings. Furthermore, the application of the present invention, while primarily concerned with right angled joints between workpieces, is not limited to right angles and could even be employed in compound joints, let alone in mitre joints.

Claims (12)

1. A workcentre comprising a frame and a worktable, the frame mounting a tool mounting means adapted for movement over the worktable in three orthogonal directions and adapted to receive a routing tool; a computer, controlling movement of said tool mounting means and having operator input means and a program; and clamping means adapted to clamp two workpieces to the worktable, said workpieces to be joined together by a mortise and tenon joint, the requisite cuts thereof to be machined by said workcentre, said program being adapted to direct movement of the tool mounting means through a predetermined path from a start position input to the computer by an operator through said operator input means so that said tool cuts mortises and tenons in said workpieces.

2. 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 elongate substantially rectangular cuboid workpiece so that one end of said first workpiece has edges substantially parallel said first and second directions; second clamping means on said table enabling clamping of a second elongate substantially rectangular cuboid workpiece so that one end of said second workpiece has edges substantially parallel said second and third directions, said end of the second workpiece abutting the side of the first workpiece so that said end of the first workpiece is substantially flush with a top side of said second workpiece and said second workpiece being offset in said second direction with respect to said first workpiece by an amount equal to the pitch of the mortise and tenon joint to be cut in said workpieces by the workcentre; and, a routing tool mounted on said tool mounting means; said program being adapted to move said tool from an operator input start position along a predetermined path resulting in tenons being cut in said first workpiece and mortises being cut in said second workpiece, whereby said workpieces may be joined together.

3. A workcentre as claimed in claim 1 or 2, 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.

4. A workcentre as claimed in claim 1 or 2, in which 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.

5. A workcentre as claimed in claim 3 or 4, 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.

6. A workcentre as claimed in claim 2 or in any of claims 3 to 5 when dependent on claim 2, in which the worktable comprises a series of planks laid side by side between two support elements, and said first clamping means comprises a pivotable section of one plank between said support elements, the pivotable section being pivotable between a first position in which it is flush with the other planks and a second position in which it is perpendicular to its first position and in which it opens a gap in the worktable between said section and an adjacent plank and through which gap said first workpiece may be inserted and clamped against said section.

7. A workcentre as claimed in claim 6, in which said section has at either end thereof a plate by means of which said section is pivoted to said support elements, at least one of the plates having an arcuate slot through which a pin of a clamp passes, which clamp is fixed to said elements and is adapted to clamp said plate and hence the section with respect to the worktable.

8. A workcentre as claimed in claim 6 or 7, in which said first clamping means further comprises a bar mounted on pins fixed in said section near its ends and cam means arranged on said pins to press said bar towards said section to clamp a workpiece positioned therebetween.

9. A workcentre as claimed in claim 6, 7 or 8, in which said second clamping means comprises at least two of said planks adjacent said section being mounted on end plates adjustably fixable with respect to said supports so that said at least two planks form a sub-table capable of being raised and lowered with respect to the worktable.

10. A workcentre as claimed in claim 9, in which the sub-table is capable of being raised at least to the level of said section when it is pivoted through a right angle from said flush position.

11. A workcentre as claimed in claim 8, 9 or 10, in which said second clamping means further comprises a bar mounted on pins fixed in said sub-table and cam means arranged on said pins to press said bar towards the subtable to clamp a workpiece positioned therebetween.

12. A workcentre substantially as hereinbefore described with reference to the drawings.