GB2243576A

GB2243576A - Mitre guide

Info

Publication number: GB2243576A
Application number: GB9009654A
Authority: GB
Inventors: Thomas Wilfred Woodward
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-04-30
Filing date: 1990-04-30
Publication date: 1991-11-06
Anticipated expiration: 2010-04-30
Also published as: GB2243576B; GB9009654D0

Abstract

An adjustable mitre guide comprises a centre arm having a longitudinally aligned guide slot 2 to receive and guide a saw blade, two side arms 5, 11 hinged to a front end of the centre arm whereby each side arm is capable of pivotal movement through at least 90 DEG from a position substantially adjacent and parallel to the centre arm to an angled position at which the angle of each arm to the centre arm is greater than 900, and location means including link arms 30, 31 to adjustably secure the side arms at equal angles to the centre arm. <IMAGE>

Description

MITRE GUIDE The present invention relates to an improved form of mitre guide usable for cutting material at a range of angles including angles greater than 90 and less than 45 .

Mitre guides, commonly known as mitre blocks, are well known in the woodworking and engineering industries for cutting materials at angles of 45" or 90 , e.g. to fit architrave around a door frame or coving at the corners of a room. In the latter instance if the angle between two walls of a room is, say, 80 rather than a right angle, then that angle has to be measured and the coving marked for cutting in a conventional manner. There is, therefore, a need for a mitre guide that is adjustable and can be used for cutting materials at a wide range of angles including angles less than " up to ap'.roachinS; sp; a~hin for internal corners and from greater than 180 up to more than 270 for external angles.

In accordance with one aspect of the present invention there is provided an adJustable mitre guide comprising a centre arm having longitudinally aligned guide means to receive and guide a saw blade, two side arms hinged to a front end of the centre arm whereby each side arm is capable of pivotal movement through at least 9" from a position substantially adjacent and parallel to the centre arm to an angled position at which the angle cf each arm te the centre arm is greater than 90", and location means to adjustable secure side arms at equal angles to the centre arm.

Freferably.the location means is arranged to ensure that the side arms lie at equal angles to the centre arm during said pivotal movement. More preferably the location means comprises two link elements pivotally attached at one end to respective side arms and at the other end pivot ally attached relative to each other and to a locking member lockable in position relative to the centre arm at a required position relative to the length of the centre arm.

The locking member and centre arm may be provided with complement ary shaped format ions, and preferably those formations cause the locking member to be captively guide for sliding movement relative to the length of the centre arm. Suitable pairs of complementary formations for captive sliding movement comprise in cross-section a male formation such as that of a T head or the tongue of a dovetail and a female formation such as that of a T section channel and dovetail mouth respectively. Preferably the male formation is carried by the centre arm. The locking member may be provided with a clamp screw or like securing means operable to lock the locking member against sliding movement.

The centre arm may comprise a longitudinally continuous slot for receiving and guiding a saw blade or it may comprise two or more longitudinally spaced saw guides.

The side arms may be of a right angled section, either along the whole length of each arm or t two or more longitudinally spaced positions whereby the arm is inherently provided with a support for material to be cut.

Alternatively the side arms may have support elements selectively movable or positionable to a support position for assisting with support of material to be cut.

The side arms may be mounted for pivotal movement about about a common axis, the pivotal mounting in that case needing to be partitioned clear of the normal blade position. Preferably, however, the side arms are hinged for pivotal movement about respective axes which lie close and more prefer ably as close as possible to but symmetrically at either side of the longitudinal line cf the blade position.

Preferably the link elements are pivot ally secured to the side arms at a distance from the pivotal axis of the respective side arm which is in the range of one third to three times, and more preferably one half to two times, the distance between said axis and the pivotal mounting of the other end of the link elements when the side arm lie at their maximum angle relative to the centre arm. The link elements may be of similar dimensions to result in a symmet ri col arrangement.

In accordance with another aspect of the present invention an adjustable mitre block comprises a centre arm containing a longitudinally aligned cutting slot to receive a saw blade, two side arms having right angled sections and hinged to the front end of the centre arm on either side thereof for pivotal movement from a position substantially adjacent and parallel to the arm to an angled position where the angle of each arm to the centre arm is greater than 90, and means to adjustably secure the side arms at equal angles to the centre arm.

Embodiments of the invention will now be described with reference to the accompanying diagrammatic drawings in which: Figure 1 is a perspective view of a guide block according to the present invention with the side arms positioned to cut material at an angle of less than 45", Figure 2 is a perspective view of the mitre block with the side arms each forming a right angle with the centre arm, Figure 3 is a perspective diagrammatic view of the mitre block with the side arms positioned at angles greater than 90 to the centre arm, Figure 4 is a perspective view of the underside of the mitre block of Figs. 1-3, Figure 5 shows means for locating the side arms, Figure 6 shows a side arm including a workpiece clamping means, Figure 7 and 8 are exploded views of parts of a mitre guide in accordance with another embodiment, Figure 9 is a perspective view of the guide of figures 7 and 8, and Figure iO shows parts of yet another mitre guide in accordance with the invention.

Referring to the drawings a mitre guide block comprises an elongate rectangular section centre member 1 and two side arm members 5 and 11. A longitudinally extending slot 2, dimensioned to receive a saw blade, is formed in the upper surface la of member 1, the slot extending partway through member 1 parallel to the sides thereof. A T shaped slot 3 is formed in the underside ib ci member 1 and extends longitudinally of member 1 for approximately 4/5 of its length but does not communicate with slot 2.

A tongue portion generally indicated at 4 and consisting of elements 4a and 4b divided by slot 2 is formed at the forward end 1c of member 1 by machining back to provide shoulders 21 and 22 at the upper la and lower ib surfaces of member 1. Shoulders 21 and 22 are cut back at an angle of 45 to longitudinal axis of member 1.

Two side members, 5 and 11, are formed of right angled section material having vertical portions 6 and 12 and horizontal portions 9 and 14 respectively. The forward ends 7 and 13 of arms 5 and 11 are cranked and grooves S d 19 in sides 6 and 12 to provide jaws 8A and 19A to receive the respective halves of tongue portions 4a and 4b cf member 1. Jaws 8A and 19A are pivot ally connected to tongue portions 4a and 4b by pivot pins 16 and 17 respectively. The angle at which the forward ends 7 and 13 of arm members 5 and 11 are cranked is about 45 to conform with the angle of shoulders 21 and 22 of member 1.Sides 9 and 14 cf side members 5 and il lie at an angle of 45' to provide edge portions 10 and 15 respectively and enable the members to be individually pivoted forwardly at an angle of more than a0 from member 1. At a 45' angle of cut back the side arm members 5 and 11 can be pivoted forwardly so that side members 5 and 11 form a right angle, as illustrated in figure 3.

The means for fixedly positioning arms 5 and 11 et equal angles to member 1 comprises two flat strip-like link elements 30 and 31 of equal lengths pivotally located on the undersides of arm portions 9 and 14 at 32, 33 equidistant from the centre axis of member 1 and equispaced at one third of the distance along the underside of arm members 9 and 14 from the forward end of the device. Link elements 30 and 31 extend rearwardly and are pivot ally located on a thumb screw 34 the lower end portion of which is screw threadly located in a slide 35 which in turn is positioned for captive sliding movement along a T-shaped slot 3.The device is mounted on studs 40, 41, 42 and 43 pcsitioned respectively on the lower portion ib of member 1 the underside portions 9 and 11 of arm members 5 and 11 and in sliding engagement with slot 3.

In use for cutting an architrave to fit into the edge of a door frame, the device is offered up to an internal corner of the door frame and members 5 and 11 are extended outwardly from member 1 until the edge portions 9 and 14 are parallel to the frame members. Thumb screw 34 is then tightened down to lock side 35 against cross arms of slot 3 and secure arm members 5 and 11 in position. The mitre block is then moved to a workbench, the architrave for one side of the frame is placed in the angle formed between sides 6 and 9 of member 5 and the end of the architrave is cut at the correct angle by means of a saw directed along the guide slot 2 in member 1. The architrave to fit along the other side of the door frame is then placed in the angle formed between arms 12 and 14 of side member 11 and the end portion cut to shape as before.It is then located around the door frame, the two cut edges forming a perfect mitre.

For external angles the device is used in the manner illustrated in Figure 3 for angles between 90 and 1bf)e.

The mitre may be used to cut through material at 90' by extending both arms out to an angle of 90' from the body member as shown in the illustration of the device shown in Figure 2.

In the device illustrated in Figures 1 to 5 the most acute angle that can be encompassed by arms 5 and 11 when in the position generally illustrated in Figure 3 will depend upon the angle of cut back of sides 9 and 14 to produce edges 10 and 15 and also the angle at which the forward ends of members 9 and 11 are cranked; the smaller the angle of cranking and the greater the outback of sides 9 and 14 then the more acute will be the angle that can be encompassed b the edges of sides 9 and 14.

Sides 5 and 11 may be attached to the forward end of member 1 by the use of a simple hinging mechanism in which case the members 5 and 11 will not need to have cranked forward portions ncr will it be necessary to produce the tongue portion 4 of member 1. In this construction the primary restraint on the acuteness of the angle between arms 5 and 11 for use on external corners will be the cut back 10 of arm portions 9 and 14.

Strip elements 30 and 31 may be excluded and arms 5 and 11 located in position by locking means acting on the hinge pivot pins. In this case jaws 8A and 19A may have intermeshing teeth to result in the side arms always lying at equal angles to the centre arm.

In figure 6 there is illustrated, with reference to one of the side arms only, a means attached to the side arm for clamping a workpiece in position during sawing. The means consists of a vertical rod member 50 which is screw threadedly secured to the top edge of side 6 of arm 5 (a corresponding rod is secured to arm 12 of side 11). One end of a swinging arm element 51 is located on rod 50 which passes through an over-sized hole 52 in element 51. The other end of element 51 is formed a screw threaded hole 56 through which passes a correspondingly screw threaded clamp rod 53 having at it's upper end a wing nut 54 and at the lower end a clamp dolly 55.

Waxen a workpiece is positioned in the angle between the sides 6 and 9 of arm 5 the element 51 is pivoted about rod 50, from the out of the way position shown in figure 6, to permit the dolly 55 of clamp rod 53 to locate on the workpiece. Element 51 is allowed to slide down rod 50 te the maximum extent permissible. Clamp rod 53 is then thightened against the workpiece ty rotating wing nut 54. Since hole 52 is oversize the opposite end of element 51 carrying clamp rcd 53 rises and the sides of hole 52, at opposite ends of a diameter parallel to the axis cf element 51, grip rod 50 snd prevent the element sliding up rod 50.

i=rten the workpiece has been cut to shape the clamp rod 53 is released and can be removed from rod 50 and placed on the corresponding rod secured to side arm 11 to clamp a second workpieee in position on that side arm.

Rod 50 may have a roughened or serrated surface to permit improved grip. Alternativelv both it and hole 52 'of appropriate size) may be correspondingly threaded. Other shapes for rods may be used although there may then be a requirement that the element 51 be removed from rod 53 when needing to change the position of the element with reference to the workpiece positioned on the side arm.

In a second embodiment of the invention illustrated in Figures 7-9 a mitre guide 60 is constructed generally as described with reference to Figures 1-6 apart from three main exceptions.

One exception is that the front end 61 (see Figure 7) of the centre arm 62 is not cranked but is rebated to receive, at each side of the blade slot 63, a hinge plate 64 positioned such that the hinge axes 65 lie symmetrically close to the slot 63.

A second exception is that the centre arm slot 3 of Figure 2 is replaced by a tongue formation 65 (see Figure 8) along which a captive locking member 66 is free to slide.

The third main difference is that each rectilinear link element 30 is replaced by a cranked element 67 (see Figure 8) which is of bent form so that in a storage configuration (shown in Figure 9) the two link elements 67 lie in a nested, superimposed configuration adjacent the locking member.

In a further embodiment, illustrated by Figure 1D, a mitre guide has a centre arm 70 having two longitudinally spaced saw guides 71. The side arms 72 likewise are of a discontinuous form and in this case each is of a right angled section at'three discrete positions 73.

The mitre guide blocks of the present invention may be formed from metal such as aluminium or steel or other materials such as plastics or wood.

Claims

CLAIMS:

1. An adjustable mitre guide comprising a centre arm having longitudinally aligned guide means to receive and guide a saw blade, two side arms hinged to a front end of the centre arm whereby each side arm is capable of pivotal movement through at least 90" from a position substantially adjacent and parallel to the centre arm to an angled position at which the angle of each arm to the centre arm is greater than 90 , and location means to adjustable secure the side arms at equal angles to the centre arm.

2. A mitre guide according to Claim 1 wherein the location means serves to ensure that the side arms lie at equal angles to the centre arm.

3. A mitre guide according to Claim 1 or Claim 2 wherein the location means comprises two link elements pivotally attached at one end to respective side arms and at the other end pivotally attached relative to each other and to a locking member lockable relative to the centre arm.

4. A mitre guide according to Claim 3 wherein the locking member and centre arm are provided with complementary shaped formations.

5. A mitre guide according to Claim 4 wherein said formations serve to captively guide the locking member for sllding movement relative to the centre arm.

6. A mitre guide according to Claim 5 wherein the centre arm is provided with a male formation and the locking member has a female formation.

7. A mitre guide according to any one of the preceding claims wherein the side arms are of s right angled section.

8. A mitre guide according to any one cf the preceding claims wherein the side arms are hinged for pivotal mcvement about respective axes which lie at either side of the longitudinal line of the blade position.

9. h mitre guide according to Claim 8 wherein said axes lie close to and symmetrically at either side cf said longitudinal line.

10. A mitre guide according to any one of the rre.eoin claims wherein the link elements are pivot ally secured to the side arms at a distance from the pivotal axis of the respective side arm which is in the range one third to three times the distance between said axis and the pivotal mounting of the other end of the link elements when the side arms lie at their maximum angle relative to the side arm.

11. A mitre guide according to Claim 10 wherein said range is one half to two times.

12. A mitre guide according to any one of Claims 3 to 6 wherein the two link elements are of corresponding dimensions.

13. A mitre guide constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

13. An adjustable mitre guide comprising a centre arm containing a longitudinally aligned cutting slot to receive a saw blade, two side arms having right angled sections and hinged to the front end of the centre arm on either side thereof for pivotal movement from a position substantially adjacent and parallel to the arm to an angled position where the angle of each arm to the centre arm is greater than 90', and means to adjustable secure the side arms at equal angles to the centre arm.

14. A mitre guide constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS.

1. An adjustable mitre guide comprising a centre arm having longitudinally aligned guide means to receive and guide a saw blade, two side arms hinged to a front end of the centre arm whereby each side arm is capable of pivotal movement through at least SO from a position substantially adjacent and parallel to the centre arm to an angled position at which the angle of each arm to the centre arm is greater than 90 , and location means to adapted to ensure that the side arms lie at equal angles to the centre arm.

2. A mitre guide according to Claim 1 wherein the location means comprises two link elements pivotally attached at one end to respective side arms and at the other end pivotally attached relative to each other and to a locking member lockable relative to the centre arm.

3. A mitre guide according to Claim 2 wherein the locking member and centre arm are provided with complementary shaped formations.

4. A mitre guide according to Claim 3 wherein said formations serve to captively guide the locking member for sliding movement relative to the centre arm.

5. A mitre guide according to Claim 4 wherein the centre arm is provided with a male formation and the locking member has a female formation.

6. A mitre guide according to any one of the preceding claims wherein the side arms are of a right angled section.

7. A mitre guide according to any one of the preceding claims wherein the side arms are hinged for pivotal movement about respective axes which lie at either side of the longitudinal line of the blade position.

8. A mitre guide according to Claim 7 wherein said axes lie close to and symmetrically at either side of said longitudinal line.

9. A mitre guide according to any one of the preceding claims wherein the link elements are pivotally secured to the side arms at a distance from the pivotal axis of the respective side arm which is in the range one third to three times the distance between said axis and the pivotal mounting of the other end of the link elements when the side arms lie at their maximum angle relative to the side arm.

10. A mitre guide according to Claim 9 wherein said range is one half to two times.

11. A mitre guide according to any one of Claims 2 to 5 wherein the two link elements are of corresponding dimensions.

12. An adjustable mitre guide comprising a centre arm containing a longitudinally aligned cutting slot to receive a saw blade, two side arms having right angled sections and hinged to the front end of the centre arm on either side thereof for pivotal movement from a position substantially adjacent and parallel to the arm to an angled position where the angle of each arm to the centre arm is greater than 90-, and means to adjustably secure the side arms at equal angles to the centre arm and ensure that they lie at equal angles to the centre arm.