GB2232381A - Proportional dividers - Google Patents

Abstract

Proportional dividers comprise two pointed arms 1 and 2 with integral loops 4, for thumb or finger, having slots 5 fitted with slides 6 which engage in grooves 9 representing a selection of scale ratios. The arms and slides are held together by a nut 8 and bolt 7 which acts as a pivot and locks the slides in the selected scale ratio grooves 9, at the same time permitting the arms to be opened or closed scissor fashion. Pencil type leads 11 fitted in pointed ends of the arms permit a measurement taken to be marked on the drawing in progress. <IMAGE>

Description

ARTISTS' PROPORTIONAL DIVIDERS This invention relates to Artists' proportional dividers.

Proportional dividers are a well known instrument by means of which a draughtsman is able to prepare a drawing to an enlarged or reduced size in a number of indicated scale ratios, from that of an original.

Artists also have a need to prepare drawings or sketches either from life-size subjects or flat copy (e.g. photographs) to an enlarged or reduced size. Much greater accuracy and saving in time can be achieved by the use of these proportional dividers than the usual methods readily to hand and normally employed, that of using a scale grid or whatever drawing implement is being used, i.e. pencil, pen or brush handle held at arms length towards the life subject and used as a measure by sliding the thumb along the implement's length from one end.

According to the present invention the artists' proportional dividers comprise two arms each with a loop for thumb or finger and a slot fitted with a slide which engages and is locked into any one of thirteen pairs of grooves, each pair setting the instrument to a different scale ratio between .75:1 and 10:1. Both arms and slides in their selected grooves are held together by means of a nut and bolt which also act as a pivot about which the arms can be opened or closed scissor fashion.

The ends of each arm are shaped into a point and also drilled to take, if so desired, a pencil type lead locked in by means of a small thumb screw. When leads are fitted any measurement between their points can be marked on the drawing being prepared.

The invention will now be described in detail with reference to the accompanying drawing in which: Fig. 1 shows in perspective the proportional dividers in a partially open mode.

Fig. 2 illustrates a plan view of the dividers in a closed mode.

Fig. 3 illustrates a side view of the dividers in a closed mode.

Fig. 4 illustrates a section through part of the dividers showing how the two slides are located and locked into a selected scale ratio groove.

Lerring to the drawing, the proportional dividers comprise two arms 1 and 2 shaped to a point 3 and 3A at each end and drilled, 10, to take pencil type leadsllif desired, locked in by thumb screws 12. Each arm has an integral loop 4 on one of its sides to accommodate thumb or finger.

A number of grooves 9, some of which are marked with scale ratios between .75:1 and 10:1, are incorporated in one face of each arm at right angles to slots 5 running part of the length of both arms.

Two slides 6, one in each arm, are located in and move freely along the slots 5. The underside of each slide is shaped to locate in the grooves 9 in the arms 1 and 2.

The arms with their respective slides are fitted, smooth undersides together, by a bolt 7 and knurled nut 8, which has a pivot enabling the arms to be opened or closed scissor fashion by a thumb and finger inserted in loops 4.

The slides 6 are moved along the slots 5 until they locate in a pair of grooves 9 of the scale ratio selected and are then locked in this position by the knurled nut 8.

Once a scale ratio is selected, by opening or closing the arms a measurement can be taken between the points 3 and 3A. A measurement between points 3 will give an enlarged measurement in the ratio selected between points 3A. Likewise a measurement between points 3A will give a reduced measurement between points 3. These enlarged or reduced measurements can be marked by the lead points 11 on the drawing in progress.

Claims (6)

1. Artists' proportional dividers comprising two arms each with an integral loop for a finger or thumb, have points at each end and can be fitted with pencil type leads. Slots running lengthwise in each arm are each fitted with a slide shaped on its underside to engage into grooves at right angles to the slot and representing a selection of scale ratios.

The two arms with their respective slides are fitted together by a nut and bolt which locks the slides in the chosen scale ratio grooves but allows the arms to pivot and be opened or closed, scissor fashion, with a thumb and finger in the loops.

Measurements can then be taken between the points at one end which will give corresponding enlarged or reduced measurements between the points at the opposite end.

2. Artists' proportional dividers as claimed in Claim 1 wherein means are provided by integral loops for a finger or thumb to open or close the arms scissor fashion.

3. Artists' proportion dividers as claimed in Claim 1 wherein each of the two arms can be fitted at their pointed ends with a pencil type lead held in place by a thumb screw.

4. Artists' proportional dividers as claimed in Claim 1 wherein a slot is provided in each arm fitted with a slide shaped to engage into grooves, representing scale ratios, at right angles to the slots.

5. Artists' proportional dividers as claimed in Claim 1 or Claim 4 wherein the slides located in the slots and grooves, of the chosen scale ratio, in the arms, are assembled and fastened together by a nut and bolt which act as a pivot when the arms are opened or closed.

6. Artists' proportional dividers substantially as described herein with reference to figures 1-4 of the accompanying drawing.