GB2306133A

GB2306133A - Mitre cutting guide

Info

Publication number: GB2306133A
Application number: GB9620266A
Authority: GB
Inventors: Carl Ernst Wilhelm Emmerich
Original assignee: Emmerich
Current assignee: Emmerich
Priority date: 1995-09-28
Filing date: 1996-09-27
Publication date: 1997-04-30
Anticipated expiration: 2016-09-27
Also published as: GB2306133B; GB9620266D0; GB9519742D0

Abstract

A mitre guide for cutting cornice has a planar base (1) joining parallel rails (2 and 3) defining channels (4a,4b) each side which may be laid over a length of cornice with a rail (2 or 3) abutting a longitudinal edge of the cornice. The end faces (2c,3c and 2d,3d) form cutting guides to produce the angles required for angular jointing of the two lengths of cornice.

Description

TITLE A Guide for Cutting a Cornice This invention relates to a guide for cutting cornice, of which coving is a particular example, in order to form a mitre joint between adjacent runs of cornice which abut at an angular interface.

One construction of mitre block for cutting symmetrical coving at rectangular corners is disclosed in GB 2123743A. The construction shown comprises a conventional form of mitre box wherein the saw guides are positioned at critical angles with reference to two planes in order to achieve the appropriate angle for the end face of cut coving which is placed within the box.

The construction has some disadvantages in that the saw guides are subject to wear as well as being fragile and in addition the depth of the box needs to be greater than the depth of the cornice being cut. The cornice to be cut is placed face downwards into the mitre box.

It is one of the objects of this invention to provide a much simplified and hence less costly construction for cutting a variety of cornices at any corner but wherein accuracy is maintained and in which orientation of the device by a user can be more easily effected.

Broadly and in accordance with this invention there is provided a guide for cutting cornice to form a mitre joint, the guide comprising two spaced parallel abutment rails connected together, preferably by a planar member and preferably with mutually inwardly facing abutment surfaces of each rail extending substantially perpendicular to the planar member, the rails thereby extending along each side of said planar member, complementary end faces of each abutment rail lying on a common plane with said end faces serving as guidance surfaces for a cornice cutting means, wherein, and in use, a surface of the planar member may be brought into contact with longitudinal edges of the cornice with the guide being orientated by abutment of one or other of the rails against an edge of the cornice.

The preferred form of planar member comprises a flat plate or sheet but the equivalent may be provided by using slats or other spaced cross members to link the rails together.

With such a construction the guide may be simply placed over the edges of the cornice and one or other of the abutment rails which, in use, projects from the lower surface of the planar member serves to correctly orientate and position the device on the cornice. By application of a cutting device in face contact with the end of each of the abutment rails, the cutting device may be correctly guided to produce the required angle of cut through the cornice both in relation to the longitudinal and lateral directions.

The edges of the planar member which join the ends of each opposed abutment rail will, together with the end face surfaces of the relevant abutment rails, lie at a set angle in a transverse direction with respect to the cornice to be cut. In addition, the complementary end faces of the abutment rails will enclose an angle relative to the plane of the planar member. By this surprisingly simple construction, the relevant angles in two dimensions required for cutting cornice can be accurately made. Further features of this invention and advantages thereof will now be described by reference to the accompanying drawings showing an embodiment and a modification thereof.

Referring to the drawings: Figure 1 shows a perspective view of a first embodiment, Figure 2 shows a plan view of the embodiment of Figure 1, Figure 3 shows an end view, Figure 4 shows a second embodiment, and Figures 5 to 7 illustrate the calculation of the angles for coving joints.

Referring to Figures 1 to 3 of the drawings, a mitre block for cornice comprises a planar member 1 with opposed parallel side edges which connect with parallel abutment rails 2 and 3. Each of the abutment rails has a respective "fence" surface 2a and 2b and 3a and 3b which extends substantially perpendicularly to each face surface of the planar member 1. There is thus effectively formed by the rails and the planar member 1 wide channels 4a and 4b.

The end edges of the planar member which join between the ends of the rails 2 and 3 are angled with respect to the longitudinal direction of the rails by angles B10 and B20 as indicated in Figure 2.

The end faces of each of the abutment rails 2 and 3 have angled surfaces 2c and 2d and 3c and 3d respectively. The complementary surfaces 2c and 3c are contained by or lie along the angle B10 formed by the one side end of the planar member 1 and, in addition, have an angle of rake relative to the plane of the planar member 1. This being angle A10 for surfaces 2c and 3c and A20 for surfaces 2d and 3d.

In use the channel 4b is placed on top of the two opposed edges of the cornice to be cut and the fence edge 2b or 3b formed by a respective rail can be brought into abutment with the cornice side edge in order to align the guide correctly relative to the cornice. After this operation, a saw or other cutting device may be positioned to be in face contact with surfaces 2c and 3c (or 2d and 3d) which thereby form a guide so that the correct angles for the mitre joint can be cut into the cornice. The device may be turned over and channel 4a laid on the cornice to cut complementary mitres.

The device may be constructed from a plastics material by moulding in one piece or alternatively from metal or from wood. A very economical method of construction is from an extrusion by cutting to produce the compound angles. Each length then produces a tool with no more than saw kerf waste. This method can be applied to a length of wood also. It is possible to construct the unit by grooving each of the abutment rails 2 and 3 to receive the planar member 1. The construction has excellent rigidity and is not easily deformed during use. This is an important feature as any deformation due to applied pressure on cutting the cornice can result in considerable errors in the angles of cut. The planar member 1 may be formed by slats rather than in one piece.

The guide of this invention is designed to rest on top of the cornice and thus guidance surfaces for cutting will always be presented regardless of the depth of the cornice in question. This provides a considerable advantage over mitre boxes where the sides must extend beyond the total depth of the moulding in order to provide a start for the cutting operation.

In defining the angles B1 and B2, which may be the same, and Al and A2, which also may be the same, the following criteria may be applied for mitre cutting of cornice and referring to Figures 5 to 7 wherein: a is the cornice register angle to the wall (Figure 5) b is the semiangle of the wall corner (Figure 6) (thus for external corner b = 450, internal b = 1350) A is the slice angle (relative to the base line) (Figure 7) B is the base angle (relative to fence) (Figure 7) C is the apparent guide angle (for product checking) (Figure 7) TAN B = TAN b / SIN a TAN A = TAN a / COS B TAN C = TAN a / TAN B Examnle 900 corner with symmetric cove TAN B = 1 / SIN 450 B = 35.30, complement 54.70 B is the angle of 1,52,53 triangle, A = 300 TAN C = 1 / TAN 300 C = 54.70 In summary therefore this invention provides a cornice and compound angle template with saw guiding faces to guide the cutting of compound angles and mitres relative to the face and wall edge of a moulding section.

The disposition relative to the face minimises the depth of cut required, particularly as most such mouldings are flat on the reverse.

The template being preferably in the form of an elongate H section of a width to span the moulding face and with rails of sufficient height on the underside forms a fence to an edge and on the upper side which guides the saw when commencing a cut. The template may be turned over which reverses the functions and turned end to end presenting supplementary angles.

Each end of the template is formed at a compound plane angle to its own face which guides the saw across the end of the moulding section. The angle is calculated to suit a particular situation, e.g. a cornice angle and wall corner angle around which the cornice is to be mitred.

A symmetrical template as described will suit all cornices which have show faces on which it will "balance". Those which have convex faces will require a supportive packing pw which must be taken into account when calculating the compound angle. This packing would normally be built in as a step on the template.

Four cuts in two supplementary pairs may be sawn (that is AO and 1800 - A ). Fencing from the long edge, the pair from the long face (undercutting) produces the mitres for internal corners. Sawing from the short face, cutting outwards with the saw leaning over the template, produces mitres for external corners.

When an application requires only internal or only external mitres (e.g. canted plinths, tapered tubs, etc.) then only one face of the template is involved. In such cases the reverse of the template may be angled for an alternative application involving the same base angle.

In a modification which is shown in Figure 4, a construction is illustrated which provides for two pairs of compound angles to be cut. This is achieved by providing different angles for "slice" above and below the planar member 1. Thus each end of the abutment rails 2 and 3 have two guidance surfaces 2c, 2cl: 2d,2dl: 3c,3cl: and 3d,3dl.

Claims

1. A guide for cutting cornice to form a mitre joint, the guide comprising two spaced parallel abutment rails connected together, complementary end faces of each abutment rail lying on a common plane with said end faces serving as guidance surfaces for a cornice cutting means, wherein, and in use, the guide may be brought into contact with longitudinal edges of the cornice with the guide being orientated by abutment of one or other of the rails against an edge of the cornice.

2. A guide according to Claim 1, wherein the rails are connected together by a planar member.

3. A guide according to Claim 2, wherein the mutually facing abutment surfaces of each rail extend perpendicular to the planar member.

4. A guide according to Claim 1 or 2, wherein the rails extend each side of the planar member.

5. A guide for cutting cornice to form a mitre joint, the guide comprising two spaced parallel abutment rails connected together by a planar member and with mutually inwardly facing abutment surfaces of each rail extending substantially perpendicular to the planar member, the rails thereby extending along each side of said planar member, complementary end faces of each abutment rail lying on a common plane with said end faces serving as guidance surfaces for a cornice cutting means, wherein, and in use, a surface of the planar member may be brought into contact with longitudinal edges of the cornice with the guide being orientated by abutment of one or other of the rails against an edge of the cornice.

6. A guide in accordance with any preceding claim, wherein the planar member comprises a plate or sheet member.

7. A guide in accordance with any one of Claims 1 to 5, wherein slats or spaced cross members form the connection between the rails.

8. A guide in accordance with any preceding claim, wherein the rails extend perpendicularly from each face surface of the planar member.

9. A guide in accordance with any preceding claim, wherein the edges of the planar member which join the ends of each opposed abutment rail, together with the end face surfaces of the relevant abutment rails, lie at a set angle in a transverse direction with respect to the cornice to be cut.

10. A guide in accordance with any preceding claim, wherein the complementary end faces of the abutment rails enclose an angle relative to the plane of the planar member.

11. A guide in accordance with Claim 9, wherein said angle is 35.30 for a guide intended for use in providing a 900 corner joint with symmetrical coving.

12. A guide in accordance with Claim 10, wherein said angle is 54.70 for a guide intended for use in providing a 900 corner joint with symmetrical coving.

13. A guide in accordance with any preceding claim, wherein the rails and planar member are formed from an elongate integral unit preferably comprising a plastics extrusion, the guide having been cut from said unit.

14. A guide in accordance with any preceding claim, wherein a step is provided adjacent each rail, or on the face surface of the planar member, said step forming a supportive packing for cutting the cornice.

15. A guide in accordance with any preceding claim, wherein the rails extend from each face surface of the planar member, each rail end face defining different angled guidance surfaces operative for cutting cornice brought into contact with one or other of the sides of the guide.

16. A guide for use in cutting cornice constructed and arranged as herein described and illustrated with reference to Figures 1 to 3 or 4 of the drawings and as exemplified with reference to Figures 5 to 7.