GB2056366A

GB2056366A - Rotary cutter heads

Info

Publication number: GB2056366A
Application number: GB8026106A
Authority: GB
Original assignee: WHITEHILL SPINDLE TOOLS Ltd
Current assignee: WHITEHILL SPINDLE TOOLS Ltd
Priority date: 1979-08-16
Filing date: 1980-08-11
Publication date: 1981-03-18
Also published as: GB2056366B

Abstract

A rotary cutter head comprises a body formed with one or more parallel walled grooves 3 each for receiving an outwardly projecting cutter, the general plane of the or each groove being parallel with, but offset from, the axis of the body, a recess 6a formed in a wall of the or each groove, a clamping device located in the or each recess, the or each clamping device including a screw device 8 and a (optionally floating) clamping block 9, the screw device being operable to produce a compressive clamping force for holding a cutter in position in the groove, the compressive clamping force being imparted to the clamping block radially outwardly of the screw axis. A backing plate 16 may be mounted in each groove for engaging the surface of a cutter remote from the block, at least one projection on the backing plate engaging in a corresponding recess in the cutter to prevent the cutter from flying out. <IMAGE>

Description

SPECIFICATION Improvements in or relating to rotary cutter heads Description of Invention The present invention relates to rotary cutter heads of the type described in, for example, British Patent Specifications Nos. 721,379, 814,580 and 893,198 and especially those sold under the Registered Trade Mark "WHITEHILL".

The rotary cutter heads are particularly for woodworking machines such as routing machines and spindle moulders (but not restricted thereto).

Whilst the cutter heads in accordance with British Patent Specifications Nos. 814,580 and 893,198 have been satisfactory (and still are), it is desired to enable production costs to be reduced and it is also desirable to make the cutter heads safer to use. One problem that could be encountered if these cutter heads are misused is that the cutter head might not hold the cutter sufficiently tightly if too small a piece of cutter is used (the size of the cutter having been reduced by repeated re-grinding).

It is thus an object of the present invention to provide an improved/modified rotary cutter head which can be produced more cheaply and/or result in a cutter head that is more difficult to misuse and/or is inherently safer to use.

According to the first aspect of the present invention there is provided a rotary cutter head which comprises a body formed with one or more parallel walled grooves each for receiving an outwardly projecting cutter, the general plane of the or each groove being parallel with, but offset from, the axis of the body, a recess formed in a wall of the or each groove, a clamping device located in the or each recess, the or each clamping device including a screw device and a (optionally floating) clamping block, the screw device being operable to produce a compressive clamping force for holding a cutter in position in the (respective) groove, the compressive clamping force being imparted to the clamping block radially outwardly (with respect to the cutter head axis) of the screw axis.This aspect of the invention enables a cutter of reduced size to be used more safely, as well as enables the cost of manufacture to be reduced, especially compared with the ball arrangement disclosed in British Patent Specification No.

814,580.

According to a second aspect of the present invention there is provided a rotary cutter head which comprises a body formed with one or more parallel walled grooves each for receiving an outwardly projecting cutter, the general plane of the or each groove being parallel with, but offset from, the axis of the body, a recess formed in a wall of the or each groove, a clamping device located in the or each recess, the or each recess including a screw device and a (optionally floating) clamping block, the screw device being operable to produce a compressive clamping force for holding a cutter in position in the (respective) groove, a backing plate being mounted in the or each groove for engaging the surface of the cutter therein remote from the clamping block, at least one projection being provided on the backing plate that will, in use, engage in a corresponding recess(es) in the cutter to prevent the cutter flying out of the cutter head, even if the clamping force perse is insufficient to hold the cutter in the head.

Generally, two projections will be provided on the backing plate with two corresponding recesses in the cutters which recesses will generally be holes extending through the cutters. The backing plate could be omitted and the projection(s) then provided on the cutter head itself, but of course a wider jaw would be needed. However, when the projections are provided on the backing plate, alternative projection arrangements can be provided. The projections would be in line with the pressure point of the clamping block on the cutter or, more preferably, would be radially outwardly (with respect to the cutter head axis) of the pressure point. Alternatively, the projection(s) could be provided on the (floating) clamping block, in which case the backing plate could be omitted if so desired.

In accordance with a preferred aspect of the invention, there is provided a cutter head having the features of a cutter head in accordance with the first aspect of the present invention and the features of a cutter head in accordance with the second aspect of the present invention.

Preferably, in a cutter head in accordance with the invention, the (floating) clamping block is retained by a "Seloc" pin (or other suitable retaining means) or by interlock of the clamping block with the screw device. The word "Seloc" is a Trade Mark.

The invention described and claimed in British Patent Specification No. 893,198 may also be incorporated in a cutter head in accordance with the present invention.

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, to the accompanying drawings, in which: Figure 1 shows a diagrammatic cross-sectional view of a rotary cutter head in accordance with the first aspect of the present invention (with the provision of a backing blade being shown in hatched lines), Figure 2 shows a diagrammatic cross-sectional view of another rotary cutter head in accordance with the first aspect of the present invention, Figure 3 shows a diagrammatic cross-sectional view of a further rotary cutter head in accordance with the first aspect of the present invention, Figure 4 shows a diagrammatic cross-sectional view of a rotary cutter head in accordance with the first and second aspects of the present invention (with the provision of a backing plate mounting as described in British Patent Specification No. 893,198 being shown in hatched lines), Figure 5 shows a partial diagrammatic crosssectional view of a rotary cutter head in accordance with the present invention, showing the optional use of a serrated backing plate or a backing plate with a projection for cooperating with a corresponding cavity in a blade, and Figure 6 shows a partial diagrammatic crosssectional view of a further rotary cutter head in accordance with the invention, with a blade held in place.

Whilst only one parallel walled groove is shown in each of the Figures of the drawings, rotary cutter heads in accordance with the invention will generally be provided with two (or more) parallel walled grooves (and, therefore, in use generally two (or more) blades) peripherally equidistantly spaced.

Referring to the drawings, there are shown four embodiments of cutter heads embodying the present invention. In many respects, the cutter heads are similar to the cutter heads described in detail in British Patent Specifications Nos.

814,580 and 893,198 and reference should be made thereto for a more detailed description of the various parts that are described therein.

Briefly, each cutter head comprises a flat cylindrical steel body 1 having formed at the centre thereof an axial bore 2 to enable the cutter head to be attached to a spindle of a woodworking machine. A cutter (not shown) fits into a deep, narrow groove 3, formed in the body 1, the groove extending parallel to, but offset from, the axis of the body 1. The cutter is held in position by a clamping device which comprises a clamping block 4 (which is normally cyanide case hardened steel) located in a recess 5 formed in the wall of the groove 3 which is nearer the axis of the body 1. The block 4 has an axial extension 6 which extends into a parallel sided bore, notch or groove 7, cut into the body 1 to intersect the recess 5, within which groove 7 the extension 6 abuts a screw device 8.

The screw device 8 comprises a block 9 which is slidably mounted within groove 7. The block 9 is loosely coupled to the axial extension 6 in the embodiment shown in Figure 2 (whereas in Figures 1, 3 and 4 the clamping block 4 is retained in the recess 5 by means of a "Seloc" pin 6a). The screw device 8 is formed with an axial threaded extension 10 which is engaged by a nut 11 disposed within a parallel-sided notch or groove 12 cut into the body 1 to intersect the groove 7.

The axial extension 6 is supported in a bearing collar 13 (which is normally cyanide case hardened steel) fitted in the groove 7, the collar 13 also acting to restrain the nut 11 against longitudinal movement. It will be appreciated that rotation of the nut 11 will move the screw device 8 along the groove 7 to apply a compressive force on the clamping block 4 thereby to hold a cutter in the groove 3. The upper surface of the screw device 8 is formed with a longitudinal groove or flat surface 14 which can be engaged by an "Allen" screw 1 5 so as to prevent rotational movement of the screw device 8. The word "Allen" is a Trade Mark.

A backing plate 1 6 may be provided in the groove 3one is shown in hatched lines in Figure 1. The backing plate 1 6 may be held in place by the provision (illustrated in hatched lines in Figures 1 and 4) of an axial extension 1 7 thereon which is apertured to form a passageway 18 to receive a pin 19. The pin 19 is doubleheaded and the outer head 20 is externally threaded for engaging a threaded bore 21 extending parallel to the groove 3 and communicating therewith. The head 20 is an "Allen" screw which is adjustable from outside the body 1.Reference is directed to Figure 2 of British Patent Specification No. 893,198 which illustrates very clearly this manner of retaining a backing plate and fhe description relating to said Figure 2 in British Patent Specification No.

893,198 should be referred to for further description thereof.

Referring now specifically to the differences between the cutter heads shown in the accompanying drawings and those shown in the drawings of British Patent Specifications Nos.

814,580 and 893,198, in Figure 1 the axial extension 6 of the block 4 abuts the block 9 of the screw device radially outwardly (with respect to the cutter head axis) of the axis of the screw device 8, so that the compressive clamping force is imparted to the clamping- block 4 radially outwardly of the axis of the screw device 8. It is, of course, very unusual deliberately to impart forces offset from the axis of a screw device. However, if one moves the screw device radially outwardly of the cutterhead axis, the cutter head itself could be considerably weakened and the same could become unsafe and potentially dangerous to use.

Similar considerations apply to the embodiments shown in Figures 2,3 and 4.

Figure 4 additionally shows a modified backing plate 16, having two axially spaced apart pins 22 for projecting into corresponding recesses to be formed in a cutter, the pins 22 being at (or preferably radially outwardly of) the pressure point of the screw device 8 on the clamping block 3.

The two pins 22 are spaced apart axially so that only one is seen in Figure 4. In fact, only one pin 22 could be provided on the backing plate 16, in which case, of course, the cutters for use with such-a cutter head would be provided with a corresponding recess. The recess(es) in the cutters would generally be holes extending therethrough.

Claims

1. A rotary cutter head-which comprises a body formed with one or more parallel walled grooves each for receiving an outwardly projecting cutter, the general plane of the or each groove being parallel with, but offset from, the axis of the body, a recess formed in a wall of the or each groove, a clamping device located in the or each recess, the or each clamping device including a screw device and a-(optionallyfloating) clamping block, the screw device being operable to produce a compressive clamping force for holding a cutter in position in the groove, the compressive clamping force being imparted to the clamping block radially outwardly of the screw axis.

2. A rotary cutter head which comprises a body formed with one or more parallel wailed grooves each for receiving an outwardly projecting cutter, the general plane of the or each groove being parallel with, but offset from, the axis of the body, a recess formed in a wall of the or each groove, a clamping device located in the or each recess, the or each recess including a screw device and a clamping block, the screw device being operable to produce a compressive clamping force for holding a cutter in position in the groove, a backing plate being mounted in the or each groove for engaging the surface of a cutter therein remote from the clamping block, at least one projection being provided on the backing plate that will, in use, engage in a corresponding recess(es) in the cutter to prevent the cutter flying out of the cutter head, even if the clamping forceperse is insufficient to hold the cutter in the head.

3. A rotary cutter head according to Claim 2, wherein the clamping block is a floating clamping block.

4. A rotary cutter head according to Claim 2 or 3, wherein two projections are provided on the backing plate with two corresponding recesses being provided in the cutters.

5. A rotary cutter head according to Claim 4, wherein the two corresponding recesses are holes extending through the cutters.

6. A rotary cutter head according to Claim 2 or 3, wherein the backing plate is omitted and the projections are provided on the cutter head itself.

7. A rotary cutter head according to any one of Claims 3 to 6, having the features defined in Claim 1.

8. A rotary cutter head according to any one of the preceding claims, wherein the (floating) clamping block is retained by a "Seloc" pin or by interlock of the clamping block with the screw device.

9. A rotary cutter head, substantially as hereinbefore described with reference to, and as shown in, Figure 1 of the accompanying drawings.

10. A rotary cutter head, substantially as hereinbefore described with reference to, and as shown in, Figure 2 of the accompanying drawings.

11. A rotary cutter head, substantially as hereinbefore described with reference to, and as shown in, Figure 3 of the accompanying drawings.

12. A rotary cutter head, substantially as hereinbefore described with reference to, and as shown in, Figure 4 of the accompanying drawings.

1 3. A rotary cutter head, substantially as hereinbefore described with reference to, and as shown in, Figure 5 of the accompanying drawings.

14. A rotary cutter head, substantially as hereinbefore described with reference to, and as shown in, Figure 6 of the accompanying drawings.

1 5. Any novel feature or combination of features described herein.