Apparatus for and Method of Cutting Joints

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which:

FIG. 1 illustrates an apparatus in accordance with the present invention;

FIG. 2 is a cross section through the sliding carrier of the apparatus shown in FIG. 1;

FIG. 3 shows the movable jaw of the clamping means shown in the apparatus illustrated in FIG. 1;

FIG. 4 is a cross section through the jaw shown in FIG. 3;

FIGS. 5a and 5b and FIGS. 6a and 6b illustrate the manner in which the dovetails and pins are cut;

FIG. 7 shows how a recessed dovetail pin would be cut;

FIG. 8 illustrates an apparatus in accordance with the present invention showing an alternative mechanism for mounting and moving the router;

FIG. 9 is a cross-section through the apparatus of FIG. 8 illustrating the various plates supporting the router at the pivot point;

FIG. 10 is a plan view of the router mounting mechanism of the apparatus shown in FIG. 8;

FIG. 11 illustrates how a dovetail slot is cut using the apparatus shown in FIG. 8;

FIG. 12 illustrates the cuts required in forming a dovetail pin;

FIGS. 13a, 13b and 13c illustrate how the width of the dovetail pin may be adjusted;

FIGS. 14 and 15 illustrate how the right and left hand cuts for a dovetail pin are made using the apparatus shown in FIG. 8; and

FIGS. 16 and 17 illustrate end profiles of boards cut with dovetails and pins respectively using the apparatus of FIG. 1 or FIG. 8.

FIG. 1 illustrates a dovetail cutting apparatus 1 comprising a support 2, a movable, linear carrier 3, a first clamp 4, a second clamp 5 and mounting means 6 for a cutting implement (not shown). The clamps 4 and 5 are identical in construction and each comprise a first jaw 7 and a second jaw 8. All four jaws are movable along the carrier 3 and may be locked at various positions. Each of the first jaws 7 is integral with the carrier 2 and are set at a predetermined spacing from the other jaw. Each of the second jaws 8 is capable of locking a component A, B, against the first jaw 7 in the gap between the jaws. Operation of the movable jaw 8 is described in more detail with reference to FIGS. 3 and 4.

The first clamp 4 is adapted to clamp a first component A in position (the cutting position) under the cutter mounting means 6 whilst the second clamp 5 is adapted to secure a second component B in a position (the marker position) in relation to a datum or marker 9 held in a slot in the support by an adjustable screw 9'.

A knurled knob 10 is provided which is connected by wires to the carrier 3 for moving the carrier 3 along the support 2. The gearing of the wiring is such that the carrier 3 will only move when the knob 10 is turned and not the reverse. The carrier 2 is, therefore, effectively locked or fixed in position when it is moved, by the knob 10, to a new location on the support 2.

The mounting means 6 for the router (not shown) comprises two outer grooved rails 11, a base plate 12, a turntable 13 having an upper housing 13' and a sliding plate 14 on which the router is mounted. The base plate 12 is held in the grooves in the rails 11 and supports the turntable 13 and housing 13'. The sliding plate 14 slides in the housing 13'. The base plate 12 may be moved in a direction perpendicular to the carrier 3 by a rack and pinion mechanism 15. Moreover, the turntable 13 and associated housing 13' may be set at selected angles inclined to the plane of the carrier 3 dependent upon the angles of the dovetails cut in the component B in the marker position. The sliding plate 14 carrying the router is then slid in the housing 13' across the end of the component A supported in the first clamp 4 to cut a slot therein. Straight slots may be cut if the turntable is set at 90.degree. to the plane of the carrier 3, whilst inclined slots may be cut if the turntable 12 is inclined to the carrier 3.

In use of the device, a series of dovetails is first cut by setting the turntable 13, 13' perpendicular to the plane of the carrier. A dovetail router is then passed through the end region of the component supported in the first clamp 4 a series of times to produce a series of dovetail-shaped slots such as shown in the end of the component B in FIG. 1 in the marker position. The component B having the cut dovetails is then placed in the second clamp 5 in the marker position adjacent the marker 9 and the first dovetail shaped slot B1 is aligned with the marker 9. The turntable 13, 13' is then slackened from its position perpendicular to the carrier 3 and is moved to an angle inclined to the carrier, this angle being dependent upon the angle of the dovetail router used in cutting the dovetails in the component B. A cylindrical router bit is then passed across the end of component A at this inclined angle and the turntable is then rotated to an angle inclined to the perpendicular but on the opposite side of the perpendicular to the first cut and a further slot is cut at an angle to the end of the component A. The material between the two cuts is then removed by the router in a conventional manner to yield a groove between which the sides of two pins are defined.

The carrier 3 is then advanced such that the end region of the component B lies in a second position against the marker 9 with a second dovetail B2 against the datum. The component in the first clamp 4 is then machined as above to produce a further groove defining the opposite edge of the pin already machined and a first edge for another pin. This procedure is repeated until all the pins have been cut.

The carrier 3 is shown in cross-section in FIG. 2. The carrier 3 has an upper angled end 20 and a lower grooved end 21. The angled end 20 and groove 21 are received by cooperating parts in the support 2 which permits the carrier to slide longitudinally. The carrier 2 has a toothed track 22 for locking the moveable jaws which are carried on the carrier 3. The jaws are held in the carrier by the square grooves 23 between which is defined a track 24. A movable jaw 8 is shown in FIG. 3. The jaw 8 slides in the track 24. The jaw 8 has a first part 25 which is loosely supported on a housing 26 by a cam 27 which is rotatably fixed to the housing 26 and which has a handle 28. As the handle 28 is turned, the rotatable cam 27 urges the first part 25 of the jaw to the left into a buttment with a component held in the gap between the jaws.

In FIG. 4, which is a cross-section through the jaw shown in FIG. 3, the mechanism by which the movable jaw 8 may be secured to the carrier 23 is shown. This mechanism comprises the row of teeth 22 on the carrier 3 and a sprung dog 30 which engages, in ratchet-like fashion, the teeth 22 on the carrier 3 to lock the movable jaw 8 in relation to the carrier 3.

FIGS. 5 and 5a illustrate, in plan, the upper edges of two components (A and B) in the apparatus of the present invention, spaced apart on the carrier 3. The apparatus itself is not shown. FIGS. 6 and 6a illustrate the end regions of the components shown in FIGS. 5 and 5a in elevation. Thus, the left hand component A which is the template component in the marker position is aligned so that one of the dovetail slots is aligned with the marker 9. Using the apparatus shown in FIG. 1 two cuts may be made in the component B using router 43; one the N-right axis cut which is identified by reference numeral 40, the other being the N-left axis identified by the reference numeral 41. These cuts are made with the turntable at the same angle but to either side of the Y-axis. The material between the cuts constitutes the pin which will fit into the dovetail slot 42 shown in FIGS. 5 and 6. From FIG. 1, it will be understood that the router is supported on the turntable and pivots about a centre point 44 (shown in FIG. 6A). This centre point 44 can be moved forward and backward by moving the base plate 11 in FIG. 1 generally backwards or forwards. This alters the width of the dovetail pin created and thus, before cutting the dovetail pins, the position of the baseplate, hence the centre point 44 must be determined empirically using scrap material.

In FIG. 7, the passage of a router for cutting recessed pins is shown. In this embodiment, the router does not pass completely through the end region of the wood, only through a portion thereof there to give a pin which does not extend across the entire width of the component.

The apparatus illustrated in FIG. 8 is similar to that shown in FIG. 1, and the same reference numerals are used to represent corresponding components. However, a different mounting arrangement for the router is shown. In this enbodiment, a base-plate 100 is provided as with the embodiment of FIG. 1, but this base-plate 100 is fixed in relation to the support 2. The router (shown by a dotted outline 102) is secured to a router plate 104 which is movable in a controllable manner with respect to the base plate 100. The router 102 may, for instance, be screwed to the router plate 104. The cutting bit (not shown) of the router 102 extends through a suitably shaped aperture 110 in the base plate 100 so that cutting of a part in the cutting position of the apparatus may be accomplished. The router plate 104 is rotatable on the base-plate 100 about a pivot point 112 and this pivot point 112 is capable of being moved backwards and forwards to a selected position and locked in that position. The router plate 104 is secured to the upper surface of the base plate 100, whilst still permitting the router plate 104 to move backwards and forwards and to rotate, as follows, reference being made to FIGS. 8 and 9. The baseplate 100 is provided with a stepped, or inverted T-shaped groove 120 (see FIG. 9) which groove is mirrored, albeit on a larger scale, by an upper stepped groove 108 in the router plate 104. A centre plate 106 having a profile to cooperate with the upper stepped groove 108 is received in the groove 108 and may, in some circumstances, be permitted to slide in the groove (see above). Normally., however, the centre plate 106 is held in relation to the baseplate 100 by a mechanism which permits rotation of the centre plate 106 and therefore of the router plate 104. This mechanism comprises a T-nut 124 which cooperates with the stepped groove in the baseplate 100 and into which a bolt 126 screws. The head of the bolt 126 rests in a circular button 122 which button has an outer flange 122a cooperating with a stepped aperture in the centre plate 106. Thus, when the bolt 126 is securely tightened into T-nut 124, the button 122 is held tightly against the baseplate 100. However, a slight tolerance is left between the button flange 122a and the centre plate 106 allowing the centre plate 106 and associated router plate 104 to rotate, if desired. Moreover, this also permits the router plate 104 to move backwards and forwards with the centre plate 106 sliding in groove 108. If the bolt 126 is loosened, the centre plate 106 can be moved in relation to the baseplate 100 thereby moving the axis 112 about which the router plate 104 rotates (see FIGS. 13a, b and c). The router plate 104 may rotate about the pivot point 112 between an extreme left and an extreme right hand position defined by dotted lines 116 and 117 which represent the extremes of movement of the router plate permitted by stops 118. Oblique cuts may be made in the material supported in the cutting position as described above in relation to FIG. 1. The backwards travel of the router 102 may be limited by an adjustable stop 151 which is an Alan key adjustable in a block 150 secured to the centre plate 106.

In FIG. 10, a piece of material in which a profile is to be cut, for example a wooden board 130 in the cutting position, is shown shortly after a cut perpendicular to the board 130 has been made by the router 102. Thus, the router 102 moves on the router plate 104 from the position shown by dotted lines 132 to the position shown by the solid line of the router plate 104. The cut is a dovetail slot. FIG. 11 is an elevation view of the parts shown in FIG. 10.

Turning now to the method by which a dovetail pin is cut, reference should be made to FIGS. 12 to 15. The router plate pivots between the positions set by the stops 118 about the pivot point 112 and two cuts are made, one at each of the opposite angles dictated by the position of the stops 118. Reference here should also be made to FIGS. 14 and 15. Thus, the router plate is caused to slide such that its edge contacts stop 118 along the entire length of its travel, therefore providing the cuts 132 and 134. It is to be noted here that the cutting angles are set to equal the angle of the previously cut tail to which the pin being machined will cooperate. As will be seen, the material 136 remaining between cuts constitutes the desired pin. The material between adjacent pins may be removed by simply moving the router back and forth through the material to be removed.

In FIGS. 13a, 13b and 13c, the effect of moving the pivot point 112, but maintaining the position of the stops 118 (i.e. the same cut angles) can be seen. Thus, the width of the pin can be adjusted. The width of the pin (W', W", and W'",) can be made equal to the width of the base of the dovetail slot so that the slot and pin will fit perfectly. The arrangement is simple to operate and easily to adjust finally.

In FIGS. 16 and 17, the machined ends of two cooperating end profiles are shown. In FIG. 16, a profile having a series of dovetail slots 150 is shown whilst, in FIG. 17, the end profile comprises a series of dovetail pins 152 which cooperate with the slots 150. These end profiles may be machined using the apparatus of FIG. 1 or FIG. 8.

Finally, it is to be appreciated that the mechanism whereby the cutting means is movable with respect to the support about a movable axis is usable in respect of other machines in which material is cut by a cutting means, for instance a dovetail cutting machine having only one machining position.