GB2289646A - Router attachment and router attachment kit - Google Patents

Abstract

A router attachment comprises a shaft, a bit head and a collar having a profiled guide surface, the collar being releasably and rotatably located on the shaft by attachment of the bit head to the shaft. A roller bearing or low friction plastics bearing rotatably locates the collar on a part of the shaft of reduced diameter between an end of the portion of reduced diameter and an abutment surface of the bit head. A template has a front surface which, in use, is located at a predetermined distance from a surface of a workpiece with a slot having a profiled edge of varying depth for cooperating with the profiled guide surface of the collar for guiding the router attachment. A two-piece template is described. <IMAGE>

Description

ROUTER ATTACHMENT AND ROUTER ATTACHMENT KIT The invention relates to a router attachment, to a router attachment kit and to a template for use with the router attachment.

Many different types of routers are known for different types of routing operations. A simple router attachment will include an elongate bit including a shaft and an integral cutting head bit with an appropriate profile. Router bits are also known with guide wheels in the form of roller bearings.

One form of routing operation which is particularly difficult to perform is variable depth routing. Variable depth routing operations can be performed with complex digitally controlled machine tools.

However, such tools are not normally available to amateur craftsmen and women, nor to joiners and carpenters because of their cost.

A router attachment is known from US patent 5,146,965 which is adapted for use with a conventional plunge router and avoids the need for complex digitally controlled machined tools. US patent 5,146,965 describes two basic embodiments. One has a guide surface fixed to a plunge router with a centrally located router bit. The second comprises a router bit with a sleeve and a conical end portion forming a guide surface which is rotatably mounted on the sleeve by means of a caged bearing. A router bit comprising a shaft with an integral cutting head. The shaft and sleeve are connected to one another by means of a screw.

Whereas the router attachments described in US patent 5,146,965 permit variable depth routing with relative ease, there are a number of problems associated with them.

Particularly where soft wood is concerned, a cutter head as provided for the router attachment described in that patent will give a very rough finish. In view of the shape of the grooves which made by such a router attachment, smoothing the inside of the grooves with sandpaper or the like is difficult and does not give very satisfactory results. Accordingly, it would be desirable to be able to use a finishing tool with a burred or scored surface for finishing the routed grooves formed by the cutting tool. However, with the tools described in the US patent, it is a difficult and time consuming operation to remove and replace the tool and it is also difficult to obtain the correct alignment of the finishing tool to the cuts initially made by the cutting tool. Also, the part of the attachment which is subjected to most wear, namely the cutting tool. is relatively expensive to replace.

In accordance with the present invention, there is provided a router attachment comprising: - a shaft having head attachment means for a bit head; - a bit head with cooperating attachment means for cooperating with the head attachment means releasably to attach the bit head to the shaft; and - a collar having a profiled guide surface. the collar being releasably and rotatably located on the shaft by attachment of the bit head to the shaft.

A router attachment in accordance with the invention provides the advantage that cutting and finishing bits can readily and easily be exchanged simply by changing the working head and without removing the attachment from the router, that is by switching off the router, removing the bit head (e.g. the cutting bit head) while the main body stays in the router and attaching the replacement bit head (e.g. a finishing bit head).

The invention also provides the advantage that the correct depth adjustment for the cutting and finishing tools can readily be achieved as the remaining components of the attachment have the same relative displacements after replacement of the working head.

The invention provides a further advantage that because the cutting/finishing bit heads are small and are simply attached to the shaft, the cost of replacing the cutting/finishing elements is reduced compared to previous tools as less materials are involved.

Bearing means are preferably provided for rotatably locating the collar on the shaft in order to permit free rotation of the collar.

The bearing means can include a conventional roller bearing.

Alteratively, the bearing means can comprise a bearing surface of low friction plastics material integral with, or separate from the collar. This provides a low cost alternative to providing roller bearings. particularly where the collar is also made of low friction plastics material. Such a low cost version is particularly suitable for the DIY market. Preferably, the low friction plastics material is polytetrafluoroethylene (PTFE).

For mounting the collar, the shaft preferably comprises a portion of reduced diameter, the bearing means being located at the portion of reduced diameter between an end of the portion of reduced diameter and an abutment surface of the bit head and/or a spacing member positioned between the bearing means and the abutment surface.

Preferably, the head attachment means comprises an end region of the shaft provided with an external thread and the cooperating attachment means comprises an internally threaded bore of the bit head.

This provides a particularly easy connection of the bit head(s) to the shaft. Preferably the hand of the thread is chosen such that the bit head tends to tighten onto the shaft during use.

The profiled surface of the collar preferably defines a generally conical surface with an external diameter which increases linearly.

However, the profiled surface of the collar can alternatively define a generally conical surface with an external diameter which increases non-linearly.

Preferably also, the collar comprises an annular skirt for surrounding the bit head for at least part of its axial extent in order to avoid the bit head damaging the inside of a guide slot in a template as the bit turns.

The skirt preferably includes apertures permitting entry of a tool for releasing the bit head from the shaft.

The bit head can be in the form of a cutting tool or a finishing tool, and as a result of the invention these bit heads are readily interchangeable.

The invention also provides router attachment kit comprising a router attachment as defined above including a plurality of different bit heads including at least one cutting tool and at least one finishing tool.

Preferably, the router attachment kit comprises at least one template having at least one slot configured to cooperate with the collar for producing variable depth routing.

The invention further provides a router attachment kit in combination with a template holder.

More preferably. the template has a first surface which, in use, is located at a predetermined distance from a surface of a workpiece and wherein the slot has a profiled edge adjacent to the first surface for cooperating with the profiled guide surface of the collar, the profiled edge varying in depth in accordance with a desired depth of a routing groove to be made in the workpiece.

The invention also provides a template for a router kit as defined above, the template comprising a first surface, means for, in use, locating the first surface at a predetermined distance from a surface of a workpiece, the first surface comprising at least one slot profiled to cooperate with the collar for producing variable depth routing, wherein the slot has a profiled edge adjacent to the first surface for cooperating with the profiled guide surface of the collar, the profiled edge varying in depth in accordance with a desired depth of a routing groove to be made in the workpiece.

Preferably, said slot is profiled adjacent a second surface, opposite said first surface to mirror said profiling adjacent said first surface.

Preferably, said template comprises a first plastics member defining said first surface and the adjacent profiled slot edges and connected thereto a second plastics member defined said second surface and the adjacent profiled slot edges.

The use of a template with a groove with a profiled front edge to match the profiled surface of the collar means that it is possible to achieve correct alignment of the router bit when preparing variable depth routed grooves without the expense of, for example, a plunge router. In other words, as the tool rides along within the sloped channel formed by the profiled upper edge of the slots, it is easy to maintain the router bit in a substantially vertical direction using, for example, a conventional domestic drill. Thus, this embodiment is particularly advantageous for the DIY market.

Embodiments of the invention are described hereinafter, by way of example only, with reference to the accompanying drawings which are not drawn to scale and in which: Figure 1 is a schematic cross-section view of a first embodiment of a router attachment in accordance with the invention; Figure 2 is a schematic exploded diagram, shown partly in section, of the router attachment of Figure 1; Figure 2A is a schematic representation of a finishing tool which can be used to replace a cutting tool shown in Figures 1 and 2; Figure 3 is a schematic exploded view, partially in section, of a second embodiment of a router attachment in accordance with the invention; Figures 4 and 4A are schematic illustrations of a first example of a template for use with the router attachments of Figures 1 to 3;; Figures 5 and 5A are schematic illustrations of a second example of a template which can be used with the router attachments of Figures 1 to 3; Figure 6 is a cross-sectional view of part of a particular example of a template of the type shown in Figures 5 and 5A; and Figure 7 is a schematic plan view of a template holder.

Figure 1 is a schematic cross-sectional view of an example of a router attachment in accordance with the invention. The router attachment comprises a shaft 12, a rotatably mounted collar 15 with a profiled lower guide surface 16 and a working bit head 22. The collar 15 is rotatably mounted with respect to the shaft 12 and the bit head 22 by means of a bearing 21 which is removably secured between the bit head 22 and the shaft 12 on attaching the bit head 22 to the shaft 12.

Figure 2 illustrates the router attachment of Figure 1 in more detail, by means of an exploded view, partially in cross-section.

It can be seen that the shaft 12 comprises a portion at a mounting end, 11, of larger cross-section and a portion at a working end with a smaller cross-section joined by a shoulder 13 with a sloping profile. At the working end of the shaft beyond the portion of smaller cross-section, a screw thread 14 is provided for the attachment of the bit head 22. The working end portion with the screw thread 14 preferably has an even smaller diameter that the adjacent portion of "smaller cross-section". This change in cross-section prevents the bit head 22 from being screwed too far onto the shaft 12.

The collar 15 comprises a lower profiled guide surface 16 with a generally flat upper surface 17 to define, substantially, a frustoconical shape. A central bore 19 is delimited at its upper end by an annular abutment 18 for retaining a bearing 21 which can be inserted from the lower end of the bore 19 as shown in Figure 2. Alternatively, it will be appreciated that the abutment 18 could be moved or the shape of the bore 19 redefined to permit entry of the bearing from the upper end of the bore 19.

At the lower end of the profiled guide surface 16, the collar is formed with an annular skirt 20 for reasons to be described later.

The bore and the bearing are configured such that the bearing 21 is a tight fit in the bore 19. The bearing is pushed up the bore until it abuts with the annular abutment 18. The collar with the bearing 21 can then be inserted over the narrower end portion of the shaft 12 with the inner ring at the inner core of the bearing abutting against the inner end of the shoulder 13 and with the outer ring of the bearing 21 clear of the outer end of the shoulder 13. The portion of the shaft of smaller cross-section is configured to be a tight fit within the centre of the bearing.

The collar 15 is rotatably retained in position on screwing on the bit head 22 by engagement of the internal screw thread in a bore 25 in the bit head 22 with the screw thread 14 at the working end of the shaft 12. The bit head 22 is formed with a raised ring 23 on its rear surface so that this engages the central portion of the lower surface of the bearing 21 whereby the outer portion of the bearing and, consequently, the collar 15 may rotate freely with respect to the bit head and the shaft 12. Shims 24 of similar diameter to the raised ring 23 and of varying thickness can be provided to give a desired spacing between the collar 15 and the bit head 22 for adjustments to the depth of cut required.

The hand of the threaded portions 14 and 25 is chosen so that the bit head 22 is self-tightening on operation in a manner well known to the person skilled in the art.

In order to assist the release of the bit head for replacement of that head, apertures (e.g., slots) 26 can be provided in the annular skirt 19 to enable entry of a release tool (for example a small screwdriver or a calliper-like tool) into recesses 27 which can be provided in the bit head 25. As the collar 15 is mounted for free rotation with respect to the bit head 22 and the shaft 12, it will be appreciated that turning the screwdriver or calliper-like release tool will enable easy release of the bit head from the shaft 12.

After releasing a cutting head such as the head 22 shown in Figure 2, a finishing head, for example the finishing head 28 shown in Figure 2A, may easily be attached to the end of the shaft 12, once again with the collar in place and, if required with shims 24 of an appropriate thickness, to finish the groove cut by the cutting head.

The finishing head 28 can be any conventional construction with a burred or grooved upper surface.

The shaft 12 can be made of any suitable material used for the shaft of a drill or router bit, for example of steel. The collar 15 is preferably manufactured of aluminium, but could alternatively be manufactured of steel, or from a suitable hard plastics material. The bit heads 22 and 28 are preferably made of steel with, in the case of the cutting tool 22, tungsten carbide cutting surfaces. However, in a lower cost version of a cutting head, e.g., for the DIY market, the cutting surfaces could be made of hardened steel.

The router attachment can be made in any suitable size to meet the requirements of the cutting operations to be performed. As an example, the overall length of the router attachment including the shaft and the bit head when attached could be of the order of 75mm with the external diameter of the collar being of the order of 50mm.

However, it will be appreciated that this is purely one example of an appropriate size for the router attachment. The shaft mounting end can be any suitable diameter. For example a standard router bit shaft could be > " (12.8mm) or alternatively t" (6.4mm).

Figure 3 illustrates a second embodiment of the invention. This embodiment is substantially the same as the first embodiment of Figures 1 and 2, with the exception that rather than a collar 15 with a separate bearing member 21, a collar made of a low friction material, for example a low friction plastics material, and more particularly polytetrafluoroethylene, can be provided. The use of a low friction material such as PTFE enables the collar 31 to be manufactured as a unitary construction with bearing surfaces 32 projecting inwardly into the central bore 19, avoiding the need for the provision of a separate bearing.

However, as alternatives to the embodiments shown, it will be appreciated that a metal collar could be provided with a plastics bearing (e.g. of block(s) or a ring of PTFE), and a plastics collar could be provided with roller bearings.

Figure 4 is a perspective view of a simple template for producing a curved groove of varying depth. The template 34 comprises, for example, a rectangular sheet of material with a curved slot 35 extending between a front face and a rear face of the block. The thickness of the template is chosen such that, by the provision of a variable width groove. the degree of penetration of the bit head through the template as guided by the guide surfaces 16 of the collar enables a groove of varying depth to be cut.

It will appreciated that a rectangular template will enable patterns to be formed with 2-way (or with inversion 4-way) symmetry, a hexagonal template will enable patterns to be produced with 6 or 12 way symmetry, and so on.

In use, the template 34 is secured over the surface of a workpiece to be worked. Preferably this is achieved by locating the template within a template holder (see for example Figure 7) having an appropriately sized hole for receiving the template in the various orientations to achieve the desired symmetrical patterns. The depth of the template is chosen to be such that when the slot 35 corresponds in the width to the minimum diameter of the profile surface 16 of the collar, the tip of the bit head is just clear of the workpiece. As the slot 35 increases in width, the contact point with the profile surface of the collar moves away from end of the bit head, with the result that the bit head penetrates into the work piece to form the groove. The wider the slot 35, the wider and deeper the groove formed in the workpiece.The maximum width of the slot 35 is chosen to be less than the maximum diameter of the collar 15.

The purpose of the annular skirt 20 is to ensure that the sides of the bit head 22 do not come into contact with the inner sides of the slot 35.

Figure 4A illustrates a cross section through part of the template 34 showing that the inner sides of the slot 35 are substantially perpendicular to the front and rear surfaces of the template 34.

Thus, in use, a template holder (e.g. Figure 7) having a hole defined to receive the template 30 in various orientations to achieve the desired patterns is clamped to the workpiece. A template holder may be configured to receive a number of differently shaped templates for making composite patterns, as illustrated in Figure 7 to be described later.

The template 30 is then placed in the template holder in a first orientation. After routing one set of shapes using the slot(s) in the template, the template will be replaced by another template and/or reversed and/or inverted a required number of times until the desired final pattern has been achieved.

In Figure 4, and also in the following Figures 5/5A and 6, only a single slot is shown. However, it will be appreciated that in practice a plurality of slots will usually be provided in each template in order to provide a desired pattern. The complete pattern to be made need not be provided on each template. In particular, if a pattern with two, or four way symmetry is to be made for example, one half, or one quarter of the pattern only is provided on the template, this then being turned an appropriate number of times to complete the pattern.

The template shown in Figures 4 and 4A works perfectly well as long as the router to which the router attachment is attached is of the plunger type so that vertical movement of the router attachment can be ensured. However, it may be desired, particularly for the DIY market to use the router attachment with a conventional domestic drill. It would be possible with a conventional domestic drill to use a drill stand. However, in this case, the movement of the drill over the top of the workpiece is limited by the drill stand itself. Often, it is not possible to move the workpiece under the drill stand because of the vertical support of the drill stand and or the pressure exerted by the router bit on the workpiece.

Figures 5 and 5A illustrate a modified template 36 with a modified groove 37 which enables better control of the movement of the router attachment and makes it more practical to use a conventional drill in place of a plunge router. In particular, rather than having vertical sides to the slots 35 of the template 34, in the embodiment shown in Figure 5, slots 37 are formed near the front surface of a template 36 with profiled edges 38 having a profile to correspond to a profiled surface of the collar of the router attachment. The result of using a template such as shown in Figure 5 is that the overall thickness of the template 36 needs to be greater than that for the template 34. However, significant advantages result from this.

Firstly, the contact of the profiled surfaces 16 of the collar with the sloping surfaces 38 inside the slots 37 means that it is much easier to keep the shaft vertical. Also, as the contact occurs over a wider area, this reduces the wear on the contact point between the profiled surface 16 of the collar and the slot 37 compared to the arrangement of Figure 4 where the contact point result from the sharp upper edges of the slot 35. The slot 37 can be provided with simply the profiled upper portion 38 and a substantially vertical portion 39.

Preferably, however, in order to enable the template to be reversed to take full advantage of the symmetry available, the lower edges of the slots 37 are also profiled at 40 as illustrated in Figure 5A.

Thus the overall operation of the template shown in Figures 5 and 5A is substantially similar to that of Figure 4 and 4A with the improved guidance control by means of the profiled edges 38. The template shown in Figures 4/4A and 5/5A can be formed from any suitable material such as, for example, medium density fibreboard, wood, cast aluminium or other metals or a suitable plastics material.

Figure 6 illustrates part of a template 41 forming a particular example of a template of the type shown in Figures 5 and 5A. In this embodiment, in order to reduce the amount of material required and also to facilitate mass manufacture of the template, the template is formed in two parts. An upper part 42 of the template 41 has an upper surface 46. A lower part 44 has a lower surface 48. Both the upper and lower parts are provided with strengthening walls 50, possibly in a matrix or triangular grid structure. Slots 37 with profiled edges 58 are provided in the upper and lower surfaces 46 and 48, the slots being in mirror configuration and communicating with one another at a join line 52. The strengthening walls preferably also meet at the join line 52.

The two parts 42 and 44 of the template 41 can readily be manufactured of, for example, a hard plastics material such as a conventional thermoplastics material, which provides sufficient rigidity to resist deformation in normal use. The two parts 42 and 44 of the template 41 can be glued or welded along the join line 52 to form a unitary template member. Alternatively, the upper and lower parts 42 and 44 could be provided with conventional interlocking elements enabling the two parts 49 and 44 to be connected together in a snap-fit manner.

By constructing the two parts 42 and 44 of the template 41 in plastics material, mass production with the provision of a wide number of different templates can easily be achieved, making this form of template particular suitable for a mass market.

Figure 7 is a plan view of a template holder 60 for receiving a rectangular template in the rectangular hole 62 and a smaller hexagonal template 66 with lugs 68 for fitting in the notches 64.

Although particular embodiments of the invention have been described herein, it will be appreciated that many modifications and/or additions are possible within the scope of the invention.

Thus, although particular materials have been described for the various components of the examples of the router attachments and templates described herein, it will be appreciated any other suitable materials may be chosen.

As shown in the drawings of the embodiments described above the collar can be a relatively large component extending outwardly from the shaft in use. In this case the bearing (e.g. a roller bearing) would be confined generally to a narrow region around the shaft with a relatively small static component. Alternatively the collar could be little more than the outer rotating part of a bearing having a relatively large, suitably shaped static portion to be in contact with the shaft.In this case the outer surface of the bearing could define the profiled guide surface, or alternatively a separate profiled guide surface could be attached to the rotatable part of the bearing Also, although the diameter of the collars 15/30 have been shown to increase linearly along the profiled guide surface 16, it will be appreciated that in other embodiments, profiled guide surfaces 16 with diameters which increase in a non-linear fashion could be chosen in order to give a different effects with a single template.

By the same token, the cutting surfaces and the finishing surfaces of the bit heads could also be chosen to have non-linear cutting and/or finishing profiles, for cutting, for example, grooves which have a curved side profile.

It will be appreciated that the construction of the template shown in Figure 6 could also be used for constructing a template of the type shown in Figures 4 and 4A.

The router attachment could be sold as a unit. Alternatively, or in addition, the individual components of the router attachment could be sold separately, for example by way of spares. Also, a complete set of different router heads giving different shapes, angles of cuts, cutting edges, etc., and different finishing tools, adapted to the different cutting heads and/or to give different degrees of smoothness of finish could be provided separately. Likewise, the various templates could be sold separately, with or without suitable template holders (e.g. as shown in Figure 7). It will be appreciated that the invention could also be sold as a kit including one or more of the various elements described in the patent application in combination.

Thus, for example, a kit comprising one or more cutter and/or finishing heads could be provided with a shaft, the collar and one or more templates and/or template holders.

Claims (24)

1. A router attachment comprising: - a shaft having head attachment means for a bit head; - a bit head with cooperating attachment means for cooperating with said head attachment means releasably to attach said bit head to said shaft; and - a collar having a profiled guide surface, said collar being releasably and rotatably located on said shaft by attachment of said bit head to said shaft.

2. A router attachment as claimed in claim 1 comprising bearing means for rotatably locating said collar on said shaft.

3. A router attachment as claimed in claim 2, wherein said bearing means comprises a roller bearing.

4. A router attachment as claimed in claim 3, wherein said bearing means comprises a bearing surface of low friction plastics material integral with, or separate from said collar.

5. A router attachment as claimed in any one of the preceding claims wherein said collar comprises a low friction plastics material.

6. A router attachment as claimed in claim 4 or claim 5, wherein said low friction plastics material is polytetrafluoroethylene.

7. A router attachment as claimed in any one of claims 2 to 6, wherein said shaft comprises a portion of reduced diameter, said bearing means being located at said portion of reduced diameter between an end of said portion of reduced diameter and an abutment surface of said bit head and/or a spacing member positioned between said bearing means and said abutment surface.

8. A router attachment as claimed in any one of the preceding claims wherein said head attachment means comprises an end region of said shaft provided with an external thread and said cooperating attachment means comprises an internally threaded bore of said bit head.

9. A router attachment according to any one of the preceding claims, wherein said profiled surface of said collar defines a generally conical surface with an external diameter which increases linearly.

10. A router attachment according to any one cf claims 1 to 8, wherein said profiled surface of said collar defines a generally conical surface with an external diameter which increases non-linearly.

11. A router attachment according to claim 8 wherein said collar comprises an annular skirt for surrounding said bit head for at least part of its axial extent.

12. A router attachment according to claim 11 wherein said skirt includes apertures permitting entry of a tool for releasing said bit head from said shaft.

13. A router attachment according to any one of the preceding claims, wherein said bit head comprises a cutting tool.

14. A router attachment according to any one of the preceding claims, wherein said bit head comprises a finishing tool.

15. A router attachment kit comprising a router attachment as claimed in any one of claims 1 to 12 including a plurality of different bit heads including at least one cutting tool and at least one finishing tool.

16. A router attachment kit comprising a router attachment as claimed in any one of claims 1 to 14 or a router attachment kit as claimed in 15 and at least one template having at least one slot configured to cooperate with said collar for producing variable depth routing.

17. A router attachment kit as claimed in claim 16 wherein said template has a first surface which, in use, is located at a predetermined distance from a surface of a workpiece and wherein said slot has a profiled edge adjacent to said first surface for cooperating with said profiled guide surface of said collar, said profiled edge varying in depth in accordance with a desired depth of a routing groove to be made in said workpiece.

18. A router attachment kit according to any one of claims 15, 16 and 17 in combination with a template holder.

19. A template for a router attachment kit as claimed in claim 16, said template comprising a first surface, means fcr, in use, locating said first surface at a predetermined distance from a surface of a workpiece, said first surface comprising at least one slot profiled to cooperate with said collar for producing variable depth routing, wherein said slot has a profiled edge adjacent to said first surface for cooperating with said profiled guide surface of said collar, said profiled edge varying in depth in accordance with a desired depth of a routing groove to be made in said workpiece.

20. A template as claimed in claim 19 wherein said slot is profiled adjacent a second surface, opposite said first surface to mirror said profiling adjacent said first surface.

21. A template according to claim 20 comprising a first plastics member defining said first surface and the adjacent profiled slot edges and connected thereto a second plastics member defined said second surface and the adjacent profiled slot edges.

22. A router attachment substantially as hereinbefore described with reference to the accompanying drawings.

23. A template substantially as hereinbefore described with reference to Figures 5, 5A and 6.

24. A router attachment kit substantially as hereinbefore described with reference to the accompanying drawings.