GB2368917A

GB2368917A - A device for measuring the cutting angles for mitre joints

Info

Publication number: GB2368917A
Application number: GB0027349A
Authority: GB
Inventors: Dennis Alvin King
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-11-07
Filing date: 2000-11-07
Publication date: 2002-05-15
Also published as: GB0027349D0

Abstract

A device for calculating the cutting angles in making mitre joints, comprising a first arm 3 and a second base arm 2A connected to the first arm via a pivot pin 4. The pivot pin is also connected to a first gear wheel 8 of an angle measuring device 2, relative movement of the first and second arms 3, 2A about the pin 4 rotating the first gear wheel 8. The angle measuring device further comprises gear wheels 5, 6, 7 each of which has a circular protractor on its surface, protractors being scaled such that gear wheel 5 displays the angle subtended between the first and second arms, gear wheel 6 displays a predetermined fraction (half in this case) of the angle displayed by gear wheel 5 and gear wheel 7 displays 90 degrees minus the angle displayed by gear wheel 6.

Description

Title: Device For Measuring Angles The present invention relates to a device for measuring angles.

It is often a requirement to measure the angle two pieces of wood need to be joined at. This task in itself is not always easy. For example two pieces of wood may be needed to be mitred together at an angle other than 900, e. g. at 1350. To do this a carpenter would need to cut each piece of wood at an angle of 67. 5 . If this cut is made on a mitre saw, this angle can be measured off easily. If this cut is made on a"chop saw", there is a problem as a chop saw is usually graduated to changes in its angle 450 either side of 00. The carpenter then has to subtract 67. 5 from 90'to work out that the chop saw needs to cut at 22. 50. It takes the carpenter time to make these calculations, and if the carpenter makes a mistake in any of these calculations, then material is wasted. The invention seeks to provide a solution to this problem. According to the present invention there is provided a device for measuring angles comprising: a) a base member having a base straight edge, b) an arm pivoted to rotate relative to the base member having an arm straight edge, c) a first wheel supported to rotate in said base member as said arm rotates relative to the base member, said first wheel indicating the angle of the arm straight edge relative to the base straight edge.

Preferably a second wheel is provided to indicate an angle value of half that displayed by the first wheel.

Preferably a third wheel is provided to indicate 900 less the angle indicated by the second wheel.

Preferably the or each wheel includes a circular protractor on one face thereof at least part of which is displayed through a window in the base.

In one embodiment three wheels are provided in a row with the circumference of the third wheel engaging with the circumference of the second wheel, and the circumference of the second wheel engaging with the circumference of the first wheel. Preferably each wheel is of the same diameter and each wheel rotates through the same angle. Preferably the third wheel engages with a fourth wheel which co-rotates with the arm on the pivotal axis of the arm. Each wheel may have a toothed circumference.

An embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure I shows a perspective part cut away view, Figure 2 shows the protractors on the three wheels of Figure 1, and Figure 3 shows a chart of angles.

Referring to Figure 1 there is shown a device 1 for measuring angles. Device I has a base member in the form of an elongate rectangular box 2 having a base straight edge 2A formed by its lower surface.

An elongate arm 3 is pivoted by a pivot shaft 4 extending through the box 2. Ann 3 can rotate relative to the box 2. Arm 3 has an arm straight edge 3A. Arm 3 is fixed to the shaft 4 so that when arm 3 is rotated relative to the box 2, shaft 4 will also rotate.

A first toothed wheel 5 is supported to rotate in box 2 by a pivot pin 5A. A second toothed wheel 6 is supported to rotate in box 2 by a pivot pin 6A. A third toothed wheel 7 is supported to rotate in box 2 by a pivot pin 7A. A fourth toothed wheel 8 is mounted on shaft 4 and rotates when shaft 4 rotates with rotation of arm 3.

A four wheels 5,6, 7,8 are of the same size. The teeth of each wheel engage one another so that wheel 8 rotates wheel 7, wheel 7 rotates wheel 6, and wheel 6 rotates wheel 5. Being of the same size the wheels all rotate by the same amount (i. e. if wheel 8 rotates 450, then all other wheels rotate 450.

On the front face of the wheels 5,6, 7 are circular protractors each giving different measurement angles as described with reference to Figure 2 below. Values of angles on each wheel are displayed respectively in windows 5B, 6B, 7B and can be read against a airline (not shown) in each window. Each window may magnify the numerical angle to be displayed.

When arm 3 is rotated so that it lies alongside box 2 against a stop 9, the value in window 5B reads 0 .

As shown in Figure 1, the straight edge 3A of arm 3 is at 135 to the straight edge 2A of box 2.

First wheel 5 indicates the angle of the arm straight edge relative to the box straight edge and thus reads 135 . Second wheel 6 indicates an angle value of half that displayed by the first wheel 5 and thus reads 67. 50. Third wheel 7 indicates 900 less the angle indicated by the second wheel 6 and thus reads 22. 50.

Supposing this represented the angle two pieces of wood need to be joined at, then the value of the second wheel would be the angle the wood needs to be cut at (and the angle taken for a mitre saw), and the value of the third wheel would be the angle a chop saw would need to be set at.

Referring now to Figure 2 there is shown the make up of the protractors of the wheels 5,6, 7 of Figure 1. Assuming arm 3 has been rotated 135 , then wheel 8 would rotate clockwise 135 . This action would rotate wheel 7 anticlockwise 1350 so that the value of 22. 5 would appear in the

centre of window 7B. Wheel 7 would rotate wheel 6 clockwise 135'so that the value of 67. 5 would appear in the centre of window 6B. Wheel 6 would rotate wheel 5 anticlockwise 13 5'so that the value of 135 would appear in the centre of window SB.

Referring now to Figure 3, there is shown a table giving in the first column the values of possible angles from 840 to 2760 the arm 3 might be relative to box 2 as shown in window 5B. The second column gives the corresponding angles the mitre (or mitre saw) needs to be as displayed in window 6B. The third column give the corresponding angles a chop saw needs to be set at as displayed in window 7B.

It will be appreciated that the measuring device can be used just to measure the angle between two abutting surfaces, e. g. two abutting walls or tow roof timbers in a truss, as straight edge 2A can be placed against one surface and straight edge 3A placed against another. The device may thus be used for purposes other than finding the"cut"angle of timber or other work pieces. It is envisaged that the device of the invention has good application in the making of wood and plastic conservatory frames.

The invention may take a form different to that specifically described above. For example the device could just measure the angle of the arm relative to the box, i. e. only wheel 5 could be present. The wheels could be other than cogs.

The box and arm may be made of any suitable material such as metal or plastics.

Further modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

Claims

Claims Claim 1 A device for calculating the cutting angles in making mitre joins.

The device comprising of first arm, a second arm connected there to and an angle measuring device connected to said arms, the angel measuring device having means to divide a measured angle into a pre-determined fraction of that angle Claim 2 A device as claimed in claim 1 in which the required cutting angle is displayed in a viewing window.

Claim 3 A device, as claimed in claim 1 or 2 for measuring angles comprising: a) a base member having an arm straight edge, b) an arm pivoted to rotate relative to the base member having an arm straight edge, c) a first wheel supported to rotate in said base member as said arm rotates relative to the base member. -said first wheel indicating the angle of the arm straight edge relative to the base straight edge.

Claim 4 A device as claimed in claim 3 in which the second wheel is provided to indicate an angle value of half that displayed in the first wheel ClaimS A devise as claimed in claim 3 or 4 in which a third wheel is provided to indicate 900 less the angle indicated by the second wheel.

Claim 6 A devise as claimed in claims 3-5 where each wheel includes a circular protractor on one face thereof at least part of which is displayed through a window in the base.

Claim 7 A device for calculating the cutting angles in mitre joins subsequently as herein described which refers to any one of the accompanying drawings (figures 1 and 2)