WO1996033847A1

WO1996033847A1 - Power-operated tools

Info

Publication number: WO1996033847A1
Application number: PCT/GB1996/001017
Authority: WO
Inventors: Ronald Francis Atkins
Original assignee: Atkins Ronald F
Priority date: 1995-04-26
Filing date: 1996-04-26
Publication date: 1996-10-31
Also published as: AU5505996A

Abstract

Drive to the cutter (5) of a hand-held router is made via a pin-in-slot connection (9, 10, Fig. 2) with a sleeve (8) held in the collet (6) of the router-motor (2). The pin-in-slot connection (9, 10) allows the cutter-shank (7) to slide axially within the sleeve (8), and so vary the depth of cut, in accordance with deflection of a pivoted finger-lever (20). Pivoting of the lever (20) is transmitted via an arm (18) that acts on a thrust bearing (13), to extend the cutter (5) from the sleeve (8) against the action of a spring (11, Fig. 2). The sleeve (8) may be modified to have an annular shoulder (21, Figs. 4, 5; 31, Fig. 6) that enables it to be clamped directly into the motor shaft (22) without the collet (6), and the cutter shank (7) may be retained within a modified sleeve (8', Fig. 5) solely magnetically to facilitate change of cutter. A cylindrical sleeve (41, Fig. 7) may be carried coaxially with the cutter (5) by the outer race (15') of the bearing (130) to guide cutting.

Description

Power-Operated Tools

This invention relates to power-operated tools and is particularly concerned with hand-held power-operated tools and to assemblies including cutters or other tool- bits for use with them.

The invention is especially, but not exclusively, concerned with hand-held routers. Such machines have, in their common form, a flat annular-base for standing on the surface of the workpiece and supporting a hand-held electric motor that drives the routing cutter. The motor is supported on the base on two pillars or slides that enable the motor to be slid up and down by hand with respect to the base for varying the tool height or depth in relation to the workpiece. Although hand-controlled movement of the motor up and down on the slides for varying tool-height is satisfactory for setting-up purposes, it is often difficult to achieve variation in depth with precision during the routing operation. The substantial mass of the motor and the tendency for build up of friction in the slides, make small and accurate up and down movements of the cutter difficult to achieve especially while the machine is being moved across the workpiece and is to traverses a corner or other feature.

It is one of the objects of the present invention to provide a form of hand-held power-operated tool that may be used to enable precise variations of tool-depth to be achieved.

According to one aspect of the present invention there is provided a power-operated tool having a base for standing on a surface of a workpiece and a hand-held motor mounted on the base for driving a cutter or other tool-bit in rotation, wherein the drive connection from the motor to the tool-bit includes a rotational coupling that provides for axial extension/retraction of the rotating tool-bit with respect to the motor, and wherein hand-operable means is provided for regulating the axial extension/retraction of the tool-bit as aforesaid such as to vary the tool-depth with respect to the base and thereby the workpiece.

With the power-operated tool of the present invention, variation of tool-depth is achieved through hand- regulated axial extension/retraction of the tool-bit with respect to the motor. Regulation of tool-depth in this way is inertially lighter and therefore more sensitively made, than by varying the height of the motor with respect to the base, so greater precision can generally be achieved. However, the facility for varying the height of the motor with respect to the base may still be retained as a feature of the machine according to the invention, for use in setting-up and other operations.

According to another aspect of the present invention, there is provided an assembly including a cutter or other tool-bit for a power-operated tool, wherein a shank of the bit extends into a sleeve and is coupled to the sleeve to be driven in rotation with the sleeve, and wherein the shank has freedom for axial movement within the sleeve such as to enable extension/retraction of the bit with respect to the sleeve during said rotation.

The shank of the bit may be coupled to the sleeve for rotation with the sleeve by a pin or other projection that extends transversely of the shank, the pin or other projection engaging within one or more slots of the sleeve so as thereby to enable the axial extension/retraction to take place during rotation. A power-operated hand-held router and cutter assemblies, all in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a rear view of the router according to the invention;

Figure 2 is a sectional front view of a cutter assembly in accordance with the invention, that forms part of the router of Figure 1;

Figure 3 is a sectional side view of the cutter of the assembly of Figure 2;

Figure 4 is a sectional front view of a modified form of the cutter assembly of Figure 2, shown together with part of the shaft of the router of Figure 1;

Figures 5 and 6 are sectional front views of two further modified forms of the cutter assembly of Figure 2; and

Figures 7 and 8 are, respectively, a sectional side elevation and a plan that illustrate an application of the router of Figure 1 in cutting a bevelled groove,

Figure 7 showing part of the cutter assembly of Figure 2 as modified for use with a jig in accordance with the present invention, and Figure 8 showing the cut groove with the jig still in place.

Referring to Figure 1, the hand-held router has a flat annular base 1 for support and guidance of the machine on the surface of a workpiece. An electric drive-motor 2 of the machine is supported on the base 1 on pillars 3 that act as slides to enable the motor 2 to be slid up and down to adjust its height above the workpiece-surface. Hand grips 4, which are provided either side of the motor 2 for general handling and control of the machine, facilitate the up and down sliding movement, and a releasable lock mechanism (not shown) is operable to lock the motor 2 to the support-pillars 3 once the desired height has been achieved. The height of the motor 2 above the base 1 is adjusted in this way to bring the router-cutter 5 held by a chuck or collet 6 of the motor 2, just short of or touching the workpiece, before the motor 2 is started.

To the extent the router has so far been described it is of conventional form, the normal practice being for the operator to hold the grips firmly and to release the lock mechanism once the motor is started. Release of the lock mechanism enables the operator to slide the motor down the support-pillars to urge the cutter into the surface of the workpiece. The operator then manoeuvres the machine to slide the annular base over the surface of the workpiece and draw the cutter along a path appropriate to achieve the recessing or shaping required. As the base is moved, the operator raises or lowers the motor on the support-pillars so as to vary the depth of cut and achieve the desired variation of recess-depth or cut- shape along that path.

Because of the substantial mass and consequent inertia of the motor, it is very often difficult for the operator to control depth of cut with precision using the conventional hand-held router. There is also a tendency for friction to build up in the support-pillars, adding to the difficulty of making small and accurate up and down movements of the cutter. The difficulty becomes of especial significance when the up and down movements are to be made while the machine is being moved across the workpiece and is to traverses a corner or other feature. In consequence it is common for the motor to be locked to the support-pillars with the cutter extended beyond the base, the depth of cut being then controlled by tipping the machine and varying the inclination of the base to the surface of the workpiece. This latter practice requires great skill in manipulating the machine and tipping it appropriately throughout the routing operation if the desired result is to be achieved accurately.

The hand-held router of the present invention overcomes the problems experienced with the conventional form of machine in that it enables the depth of cut to be varied with a light touch and without the difficulties experienced with moving the motor on its support-pillars or tipping the machine. In the latter respect, the machine of the invention shown in Figure 1 incorporates a facility for varying the extension of its cutter 5 through the base l without up and down movement of the motor 2. More particularly, the shank 7 of the cutter 5 used in this case, as shown in detail in Figures 2 and 3, is entered into a metal sleeve 8. It is the sleeve 8 that is inserted into and gripped by the collet 6 of the motor 2, rather than the shank 7.

Referring now especially to Figure 2, the rotational drive conveyed to the sleeve 8 held by the collet 6, is transmitted to the cutter 5 via a pin 9 that projects through the shank 7 (see also Figure 3) and is engaged within diametrically-opposed axially-extending slots 10 of the sleeve 8. Freedom of the pin 9 for movement back and forth along the slot 10 enables the cutter 5 to be extended and retracted from the sleeve 8. Movement of the cutter 5 in extension however, is subject to resilient restraint exercised by a spring 11 which acts between the upper end of the sleeve 8 and the head of a bolt 12 that is screwed into the tail-end of the shank 7.

A thrust bearing in the form of a ball race 13 is slid on the shank 7 between the head 14 of the cutter 5 and the sleeve 8. The inner race 15 bears on a shoulder 16 of the head 14, whereas a forked end 17 of a lever arm 18 (see Figure 1) bears on the outer race 15'.

As shown in Figure 1, the arm 18 is pivoted to the base 1 on a spindle 19 of a finger-lever 20 that extends close to (in the case illustrated) the right-hand grip 4 such that the lever 20 can be readily pulled up towards that grip 4 by the operator using one or more of the fingers of his/her right hand while holding that grip 4. When the lever 20 is pulled up in this way the consequent rotation of the spindle 19 causes the forked-end 17 of the arm 18 to bear down on the bearing 13 and extend the cutter 5 from the sleeve 8 against the bias action of the spring 11. Relaxation of finger pressure on the lever 20 allows the spring 11 to retract the cutter 5, so that by quite light control the depth of extension/retraction of the cutter 5 through the base 1, and therefore the depth of cut, can be very precisely regulated.

In using the hand-held router of the invention, the motor 2 is first locked in position on its pillars 3 with the tip of the cutter-head 14 just clear of the surface of the workpiece and the finger-lever 20 undeflected. The motor 2 is now started and the machine traversed across the surface of the workpiece with the cutter 5 extended and retracted as required using finger control of the lever 20. No tipping of the machine is called for and the motor 2 remains locked on the pillars 3 throughout. Accordingly, the difficulties experienced with the known machines are avoided and great accuracy and speed of operation to achieve quite delicate contours of recess and shape can be achieved.

The finger-lever 20 and the connected arm 18 may be counterbalanced or spring-biased so as to return positively to their undeflected positions with the forked bearing 13. However, in a modification, the bearing 13 instead of being slid loosely on the spindle 7 is fixed to it by a spring clip and the arm 18 has double forks for engaging the outer race 15' on the top and bottom, respectively, of the bearing 13.

With the cutter assembly of Figure 2, it is the sleeve 8, rather than the smaller-diameter shank 7, that is gripped within the collet 6 of the motor 2. Accordingly, for any particular size of machine (normally identified in terms of the maximum shank-diameter that can be accommodated within its collet) , the use of the assembly of Figure 2 imposes a reduction in the maximum size (shank-diameter) of cutter 5 it is possible to use. Where this presents a problem it can be totally, or to a large extent, overcome by a simple modification of the assembly of Figure 2; this modification will now to be described with reference to Figure 4.

Referring to Figure 4, the modification to the assembly of Figure 2 simply involves providing the sleeve 8' in this case with an annular, bevelled shoulder 21, and removing the split-bushing collet 6. In the latter respect, the shaft 22 of the motor 2 has a bore 23 and the collet 6 is conventionally secured within this by a nut 24 that when tightened onto external threads 25 of the shaft 22, urges the collet 6 against an inwardly- bevelled shoulder 26 at the mouth of the bore 23. This compresses the collet 6 so that in the circumstances of use of the unmodified cutter assembly of Figure 2, it grips the inserted sleeve 8 (instead of, in normal practice, the shank of the cutter itself) .

With the modification illustrated in Figure 4, the collet 6 is removed and the sleeve 8' is inserted into the bore 23 until the shoulder 21 abuts the inwardly-bevelled shoulder 26, bevel to bevel. Tightening of the nut 24 in these circumstances clamps the shoulder 21 tightly against the shoulder 26 so as to hold the sleeve 8' in driving engagement with the shaft 22. Thus, simply by dispensing with the collet and utilising the bore 23 itself to accommodate the sleeve 8', it is possible to increase significantly the size of cutter that can be employed.

Replacement or other change of the cutter 5, whether in the assembly of Figure 2 or 4, requires the assembly to be taken apart, and this can be time consuming and tedious where frequent changes are required during intricate work. A modification of the assembly of Figure 4 to allow the cutter to be changed in a less-demanding way, is illustrated in Figure 5 and will now be described.

Referring to Figure 5, the spring 11 and bolt 12 are in this case removed and replaced by a small magnet 27 that is secured to a bolt 28. The bolt 28 has a smaller head than the bolt 12 it replaces, such that the cutter 5 can be withdrawn from, and re-inserted within, the sleeve 8' without removing the bolt 28 and its attached magnet 27. The cutter 5 is however restrained resiliently from withdrawal from the sleeve 8' by magnetic attraction exerted on the magnet 27 by a bar-magnet 29. The magnet 29 is mounted on a non-magnetic collar 30 secured to the sleeve 8', such that the interaction between the magnets 27 and 29 fulfils the essential function of the spring 11 whilst at the same time allowing the cutter 5 to be changed without the need to unscrew the nut 24 and remove the assembly from the motor-shaft 22.

With some forms of router, the motor-shaft has an internal thread into which the collet screws. In such cases the assembly of Figure 2 may be modified as illustrated in Figure 6, to screw into the shaft in place of the collet.

Referring to Figure 6, the sleeve 8'' in this case has an unbevelled shoulder 31 and above this is provided with an external screw thread 32 to enable it to be screwed into the shaft of the motor. Flats 33 are machined into the surface of the sleeve 8'' beneath the shoulder 31 to enable a spanner to be used in screwing the sleeve 8' ' into and out of the shaft. The technique of magnetic retention used in the assembly of Figure 5 may clearly be applied as a modification to this assembly, in the same way as to the assembly of Figure 4.

The router of the present invention may be applied readily to the cutting of grooving in which variation is required from what can normally be achieved, for example in configuration and depth of cut, with known hand-held routers. One significant application in this respect is in the cutting of right-angle or other angled corners in grooving where the edges are rectilinear throughout; with known forms of hand-held router the edges of the grooving will generally be curved into the corner since the cutter is held at a fixed depth throughout. Application of the router of Figure 1 in cutting grooving with rectilinear edges into a right-angle corner, will now be described with reference to Figures 7 and 8.

Referring to Figure 7, the cutter assembly in this case is modified by the addition of a cylindrical sleeve 41 that is used in conjunction with a jig 42 for guiding the cutter 5 laterally in accordance with depth of cut into the workpiece 43. The sleeve 41, which is coaxial with the cutter-head 14 and is of a slightly larger internal diameter, is fitted fast to the outer race 15' of the ball race 13 and projects downwardly from it to the head

14. The groove 44 to be cut in this application is of V-shape in cross-section, and is intended when cut as shown in Figure 7, to include a right-angle corner. Cut of the groove 44 into this corner is carried out using the right-angle jig 42 which is clamped to the workpiece 43 back slightly from the line of the outer edge 45 of the desired groove 44. The jig 42 has inclined guide- surfaces 46 that are abutted by the sleeve 41 within the right-angle as the cutter head 14 is brought down to the position illustrated in Figure 7, in which it touches the workpiece 43 at the apex of the corner of the edge-line 45.

When the cutter 5 is now urged downwardly under hand- control of the lever 20 (acting via the forked end 17 of the arm 18) to cut into the workpiece 43, the sleeve 41 moves down between the inclined surfaces 46. This urges the sleeve 41, and with it the cutter 5 and router as a whole, diagonally of the corner, so that the cutter 5 is guided progressively towards the centre of the desired groove 44 as the depth of cut is increased. The corner is accordingly cut as a right angle as desired, without rounding.

Variation in the cross-section of the groove cut can be achieved by varying the configuration (for example, profile and inclination) of the guide surfaces of the jig. Moreover, it would be possible to profile the outer surface of the sleeve 41 and achieve interaction between this and an appropriate guide surface for guiding the cutter laterally according to depth of cut.

Existing forms of hand-held router may be readily adapted to incorporate a cutter assembly and finger-lever mechanism of the nature utilised in the router of Figure 1. In this respect, a kit comprising a finger-lever with attached or attachable spindle and lever arm (corresponding to the lever 20 with spindle 19 and lever arm 18 of Figure 1) , and a cutter assembly (such as any of those described above with reference to Figures 2 to 6) , may be made up for use in adapting standard constructions of machine to utilise the present invention. Some means of pivotally mounting the spindle on the base of the machine will in general be required, but special provision for this can be avoided in the kits for some makes of machine. In such machines, holes are already provided in the base for accommodating a side- fence guide, and the spindle may be located in these.

Although the invention has been described above in the context of a router it can be applied to hand-held power- operated tools for other purposes. It may be applied, for example, to tools used for etching (for example of glass) and for boring. In the latter regard, it is applicable to hand-held power-operated drills where conventionally there is little or no assistance to the operator in controlling bore depth. Precise control of drilling depth may be obtained with such a tool simply by mounting the drill on a workpiece-contacting base and providing for hand extension/retraction of the drill bit using a rotational coupling between the collet of the drill and the bit, corresponding to that provided for the cutter 5 by the sleeve 8 and pin 9 in the assembly of Figure 2. Such a tool is of advantage especially in the boring of blind holes in panels.

Claims

Claims !

1. A power-operated tool having a base for standing on a surface of a workpiece and a hand-held motor mounted on the base for driving a cutter or other tool-bit in rotation, wherein the drive connection from the motor to the tool-bit includes a rotational coupling that provides for axial extension/retraction of the rotating tool-bit with respect to the motor, and wherein hand-operable means is provided for regulating the axial extension/retraction of the tool-bit as aforesaid such as to vary the tool-depth with respect to the base and thereby the workpiece.

2. A power-operated tool according to Claim 1 wherein the hand-operable means includes a hand-deflectable lever and means for acting on the bit to displace the bit axially with respect to the motor in accordance with deflection of the lever.

3. A power-operated tool according to Claim 2 wherein the means for acting on the bit includes a thrust bearing carried by the bit and a pivoted arm that engages with the bearing for displacing the bit axially as aforesaid in accordance with deflection of the lever.

4. A power-operated tool according to Claim 3 wherein the thrust bearing has inner and outer races, and the arm engages with the outer race for exerting axial thrust on the bit via the inner race.

5. A power-operated tool according to any one of Claims 1 to 4 wherein the bit is a router-cutter.

6. A power-operated tool according to Claim 5 wherein a cylindrical cutting-guide is carried on the cutter coaxially with the cutter-head and with freedom for rotation relative thereto.

7. A power-operated tool according to any one of Claims 1 to 6 wherein the rotational coupling includes a sleeve that is driven in rotation by the motor, and wherein a shank of the bit extends axially into the sleeve and is coupled to it via a sliding connection for rotating the shank with the sleeve whilst allowing axial movement of the shank within the sleeve.

8. A power-operated tool according to Claim 7 wherein the sliding connection includes a pin or other projection that extends transversely of the shank to engage within one or more slots of the sleeve.

9. A power-operated tool according to Claim 7 or Claim 8 wherein the sleeve extends into a bore of a drive shaft of the motor and has an annular shoulder that is clamped to the shaft for driving engagement of the sleeve with the motor.

10. A power-operated tool according to any one of Claims 7 to 9 wherein axial extension of the bit is subject to resilient restraint exercised on the shank within the rotational coupling.

11. A power-operated tool according to Claim 10 wherein the resilient restraint is exercised by a spring acting between the sleeve and the shank.

12. A power-operated tool according to Claim 10 wherein the resilient restraint is exercised on the shank by magnetic action.

13. A power-operated tool according to Claim 12, wherein retention of the shank within the sleeve is by the magnetic action, the shank being withdrawable wholly from within the sleeve against said action alone.

14. An assembly including a cutter or other tool-bit for a power-operated tool, wherein a shank of the bit extends into a sleeve and is coupled to the sleeve to be driven in rotation with the sleeve, and wherein the shank has freedom for axial movement within the sleeve such as to enable extension/retraction of the bit with respect to the sleeve during said rotation.

15. An assembly according to Claim 14 wherein the shank of the bit is coupled to the sleeve for rotation with the sleeve by a pin or other projection that extends transversely of the shank to engage within one or more slots of the sleeve.

16. An assembly according to Claim 15 wherein axial extension of the bit is subject to resilient restraint exercised on the shank within the sleeve.

17. An assembly according to Claim 16 wherein the resilient restraint is exercised by a spring acting between the sleeve and the shank.

18. An assembly according to Claim 16 wherein the resilient restraint is exercised on the shank by magnetic action.

19. An assembly according to any one of Claims 14 to 18 wherein the bit carries a thrust bearing having inner and outer races, the inner race being arranged to transmit to the bit thrust exerted on the outer race.

20. An assembly according to Claim 19 wherein a cylindrical cutting-guide is carried by the outer race coaxially with the cutter-head.

21. An assembly according to any one of Claims 14 to 20 in combination in kit form with a hand-operated lever for pivoting to the base of a power-operated tool, and an arm for transmitting pivotal movement of the lever to the bit for extension/retraction of the bit as aforesaid.