SCRIBING DEVICE FOR DECORATIVE PROFILES

This invention relates to a scribing device for guiding a routing tool or the like for cutting the ends of elongate workpieces, and in particular wooden mouldings, to enable accurate joints to be made.

Skirting boards, picture rails, dado rails, window frame sections and the like are often made with a decorative cross section. When fixing such features around a room or constructing a frame from such sections, it can be difficult to produce neat and accurate joints at corners, with the two profiled sections mating accurately and without a gap between them. If one attempts to cut a 45° mitre joint, it will often be found that the corner is not an exact right angle, particularly in an old building. This results in a gap between the ends, and it can be difficult to trim either cut end to the correct angle.

Best practice therefore is to cut the end of one profiled section to match the cross section of the other. This can be done with a router or similar tool, but an accurate guide or template is needed to enable such cuts to be made accurately and reproducibly. At present such templates can only be produced by expensive factory-based equipment, and there is a need for a portable and adaptable device that can be set up on site to reproduce any desired section.

US-B-6,450,220 discloses a coping jig for cutting end sections of decorative trims, using preformed templates which are reversible to enable either end of a length of trim to be cut. A separate template will however be necessary for each different profile. The present invention aims to provide a portable scribing device which can be adapted to any existing profile.

The present invention provides a scribing device comprising a jig with a 'comb', or set of thin parallel plates mounted thereon, each said plate being individually and reversibly slidable in one direction relative to the others, with means for locking the plates relative to one another, whereby the set of plates can be pushed against a section of the moulding, each said plate being pushed into abutment with the profile so that the abutting ends of the plates together form a cam surface in the shape of the cross section of the moulding, and can be locked in that configuration, the jig also having a slide or other movable mounting on which a cutting tool can be mounted to follow a path defined by the cam surface, to cut an end of a section to match the profile.

The jig preferably comprises a workpiece support surface with a tool support comprising a frame or platform supported above it, for example on pillars, the comb being mounted on the tool support together with the cutting tool slide and preferably also clamping means for the section to be cut and for the section whose profile is to be reproduced .

The comb is preferably made up of elongate plates or strips, each with enlarged ends and a central section of reduced width, the plate being held together by a frame comprising transverse members between their enlarged ends, the sliding movement of the plates being limited by abutment of the enlarged ends against the transverse frame members. The frame may also include the means for securing the plates in position when the cam surface or template has been formed. The plates may be made of any suitable rigid material such as steel, aluminium or plastics. They preferably have a thickness from 0.5 to 1.5 mm.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings wherein:

Fig. 1 is a perspective view from above of a scribing device in accordance with the invention;

Fig. 2 is a side elevation of the device of Fig. 1;

Fig. 3 is an end view of the device of Fig. 1;

Fig. 4 is a plan view of the workpiece support of the device of Figs. 1 to 3;

Fig. 5 is a plan view of the tool support platform of the device of Figs. 1 to 3;

Fig. 6 is an enlarged detailed illustration of the comb assembly of the device of Figs. 1 to 3;

Fig. 7 is an enlarged detailed illustration of the mounting for the comb of Fig. 6;

Fig. 8 shows plan and cross sectional views of a router carriage;

Fig. 9 is a side elevation similar to Fig. 3, showing a workpiece and router in position; and

Fig. 10 shows how the cut end of a skirting board fits at right angles to another length of skirting with a matching cross section.

Referring first to Figures 1 to 3, a scribing device in accordance with the invention comprises a portable jig with a workpiece support 10, which is a flat sheet of any suitable rigid material such as aluminium or rigid plastics material. The workpiece support is mounted on six pillars 12, preferably with non-slip bottom surfaces, for example with a layer of rubber.

The workpiece support is shown in more detail in Fig 4, which shows an aperture 15 to act as a carrying handle and a larger aperture 14 through which a routing tool can project during a scribing operation. The support surface also has a number of strips 16, 17, 18 of rubber or the like bonded to it to help prevent the workpiece from slipping. The six pillars 12, shown in Figs 2 and 3, are fixed in place by screws 13. Screw holes 23 are provided to receive screws securing the pillars 22 which support the tool mounting platform 20.

Mounted on the tool support platform 20, as shown in Fig. 1, are a sliding carriage 30 for a router, a sample clamp 40, a workpiece clamp 50 (see Figs. 2 and 3) and a profiling comb assembly 60, all of which will be described in more detail below.

The tool support platform 20, shown in detail in Fig.5, is a flat sheet which can be made of the same material as the workpiece support and has screw holes 51 for securing it to the pillars 22. It also has a large square aperture 52 for the routing tool to project through, on each side of which are grooves or rails on 53 which the router carriage 30 can be slidably mounted. At the opposite end of the platform is a central longitudinal slot 54 for adjusting and securing the sample clamp 40 and an elongate transverse slot 56, with a central enlargement 58, to receive the workpiece clamp 50. Lines 25, parallel to the longitudinal edges of the platform, are used for aligning the sample profile and workpiece. These lines lie in planes tangential to the pillars 22 supporting the platform, so that when an edge of a workpiece is placed against the pillars it is precisely aligned with one of the lines 25.

Referring again to Fig. 1 , a pattern sample in the form of an offcut or other short section 90 of a skirting board with a decorative profile is placed end-up on the tool support platform 20 against the comb 60, to form the comb into the desired profile, as will be described in more detail below. The sample clamp 40 comprises an elongate strip extending across most of the width of the platform 20, with a central longitudinal slot 41 in which are mounted sliding clamps 46 between which the pattern sample is clamped. Screw knobs 45 are provided for fixing the positions of these clamps. Midway along the length of the strip, and formed integrally with it , is a D-shaped plate 42 with a semicircular slot 43 through which passes a screw clamp 44 which, as can be seen in Fig 3, passes through slot 54. The sample clamp 40 can thus be moved longitudinally relative to the platform, and pivoted about screw clamp 44 which can then be used to fix the longitudinal and angular position of the sample clamp.

As can be seen in Figs. 2 and 3, which show the device without the sample in place, workpiece clamp 50 can slide laterally across the platform in slot 56, to clamp workpieces of varying widths on the workpiece support.

Referring to Fig. 2, the comb 60 is mounted on a comb mounting 70 and secured in position by screw knobs 24 through holes 69, shown in Fig. 1 from which the screw knobs 24 are omitted. Fig.6 shows an enlarged plan view of the comb 60, with cross sections a and b and a single plate of the comb shown as c. Each of the plates 65 is formed as a flat strip with rectangular ends 61, 66 joined by a narrower strip 63. A multiplicity of such plates, typically from 100 to 250, is stacked in an array between spacer members 64 which are in turn held in place between side frame members 62, joined by transverse strips 67,68 above and below the plates 65. As can be seen in section b, transverse strips 68 are secured to the top and bottom surfaces of the side frame members 62 by screws 71. transverse strips 67 on the other hand are received in shallow recesses of the side frame members so that their outer surfaces are flush with the surfaces of the frame members. Because the width of end sections 61, 66 of the plates corresponds to the height of the side frame members 62 and spacers 64, and thus to the spacing between transverse members 68, the plates can slide freely between the transverse members 68. On the other hand the spacing between transverse members 67 is less than the width of ends of the plates, so that only the narrower central portions 63 can pass between them. This limits the sliding movement of the plates as well as retaining them in the frame of the comb. Screws 72, passing through bores in one of the side frame members 62, can be used to fix the positions of the plates in the frame, by pressing a spacer 64 against the stack of plates, which in turn are pressed against the opposite spacer and frame member, so that friction prevents the plates sliding relative to one another.

In the position shown in Fig. 6, with the fixing screws 72 loosened, the ends 61 of the plates are abutting transverse frame members 67, and cannot therefore slide further to the right as shown in Fig. 6. They can however slide in the opposite direction Since their widened ends 66 can pass between transverse frame members 68 and continue sliding until they abut the transverse frame members 67.

Bores 69 are provided in the side frame members for the passage of screws 24, to secure the comb on its mounting 70. The comb is reversible and can be positioned either way up, as will be described below.

Referring now to Fig. 7, the comb mounting 70 comprises a rectangular plate of a rigid material, for example aluminium. Bores 78 are provided at each end to receive screws 24 to fix the comb in place. A pair of parallel shallow channels 75, 76 of rectangular cross section run the length of the plate, and either of these can receive one of the transverse frame members 68 of the comb, depending on which way up it is.

Six small screw holes 79 are provided on the bottoms of the two channels 75, 76 to receive fixing screws securing the comb mounting to the Support platform 20.

Referring now to Figs. 1, 2 and 8, the carriage 30 for the router is rectangular in plan view, extending across the width of the tool support platform 20 and has projecting elongate runners 29 on its underside which run in channels 53 to guide the carriage so that it can slide backwards and forwards on the platform 20. An aperture 35 extends over most of the length of the carriage to receive a router support plate 80 shown in more detail in Fig. 10.

As can be seen in Fig. 2, the carriage 30 is not flat but has a top surface which slopes downwards at a slight angle in a direction away from the comb so that the router support plate 80, which is flat, is tilted slightly backwards, at an angle of perhaps 2-3°, when mounted on the carriage.

Referring to Fig. 8, the router support plate is in the form of a circular disc adapted to be attached to a router and support it on the carriage 30. As seen in cross section, the plate has two channels of rectangular cross section on its underside, these channels fitting over respective parallel lengths 36 of the carriage on either side of the aperture 35. The carriage and the router support should be made of materials with a relatively low coefficient of friction, so that the router can slide easily on the carriage, which can in turn slide easily backwards and forwards without sticking.

The router support plate has a cam follower pin projecting upwards from its upper leading edge, the purpose of which will be described below. It also has a central aperture 82 through which a routing tool can project.

Referring back to Fig. 1 , to form the desired profile the comb 60 is tightly secured in position by screws 24 but whose screws 71 are loosened so that the plates 65 can slide. The moulded end of the sample to be copied is positioned, end-up on the line 25 on the tool support, its flat side against the front of the sample clamp 40, and secured between clamps 46. The comb is positioned with transverse frame member 67 nearest the sample so that the plates 65 can slide towards the sample but not away from it.

If the sample is of regular rectangular cross section the clamp 40 can be set parallel to the comb, but if the section is for example of tapered cross section the clamp can be set at a slight angle to the comb. The clamp is fixed in position by tightening screw 44 and the slide clamps 46 positioned and secured by screws 45 against the opposite ends of the sample to hold it against lateral movement.

Those plates 65 of the comb which are aligned with the profiled part of the sample are each pushed against the sample as far as they will go. A narrow blade can be used to push each plate individually, so that the plates together form a surface that can be used as a template to reproduce the cross sectional pattern on the end of a section. Screws 72 are then tightened to fix the positions of the plates.

For the actual scribing operation, the sample clamp 40 is loosened and the sample 90 removed, the screws 24 are then undone and the comb 60, with its plates 65 forming a surface having the desired profile, is inverted by rotating it through 180° about an axis passing through the aligned central portions of the plates, and repositioned on the mounting 70 with the desired profile facing the router carriage. This is the position of the comb in Fig. 9, in which it is again secured by screws 24.

Fig. 9 shows the actual profile cutting operation. A power tool 95 with a routing bit 96 is attached to the router support 80 which in turn is mounted on the carriage 30. The bit projects through the apertures 82, 35 and 14, at a slight angle to the vertical owing to the slope of the top

surface of carriage 30, to just below the workpiece support 10. The router is moved forwards on the carriage until the follower pin 84 abuts the end of the plates of comb 60.

A workpiece in the form of a length 92 of dado rail or the like, having the same cross section as the sample shown in Fig. 1, is placed on the workpiece support 10 and one longitudinal edge of it is placed against pillars 22 so that is precisely aligned with the line 25 on the platform 20. With the router moved to one side, but still in contact with the comb plates, the workpiece is moved longitudinally forwards until the end to be scribed is just past the routing bit. The workpiece is then fixed in position by clamp 50 through clamping slot 56, pressing it onto the rubber strips 16, 17, 18 to prevent slipping.

The routing tool 95 is switched on and moved from one side of the jig to the other, always keeping the follower pin in contact with the profile defined by the comb plate ends. In this way the routing bit scribes the end of the workpiece to precisely the shape of its cross section, so that the scribed end can abut a matching section at right angles without a gap.

In Fig. 11 a length of skirting 100, scribed by the method described above, is shown in front elevation adjacent another length 110, positioned at right angles to it and shown in cross section. It can be seen how the scribed end 105 precisely matches the cross section of 110, so that the end of skirting 110 can be fitted right into a corner without being cut to shape and the length 100 can be brought into abutment with it to form a neat corner without gaps.

Having set up the jig as described above, any number of lengths of moulding can be cut to the same shape.