GB2261853A

GB2261853A - Drawing instrument for circles of large and small radius

Info

Publication number: GB2261853A
Application number: GB9125359A
Authority: GB
Inventors: Dominic Vigne Mccannon
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-11-28
Filing date: 1991-11-28
Publication date: 1993-06-02
Anticipated expiration: 2011-11-28
Also published as: GB2261853B; GB9125359D0

Abstract

A drawing instrument has a planar base (10) and a planar pivoting member (12) rotatably mounted towards one end of the base. Both the base (10) and the pivoting member (12) are provided with apertures (22a, 22b; 28a, 28b) which can receive a drawing implement. By pressing on the pivoting member (16) and inserting the drawing implement in the base apertures (28a, 28b) the base can be pivoted about the pivoting member by moving the drawing implement, enabling arcs of predetermined, relatively large, radii to be drawn. By pressing on the base (10) and inserting the drawing implement in the apertures (22a, 22b) in the pivoting member (12), the pivoting member can be rotated to produce arcs of predetermined, relatively small, radii. Slots (20, 26) in the member (12) and base (10) enable the drawing of lines inclined to one another. <IMAGE>

Description

DESCRIPTION DRAWING INSTRUMENT The present invention relates to drawing instruments.

When it is desired to draw curved outlines, particularly circles or arcs, at present it is necessary either to use a pair of compasses or to use a special stencil having a plurality of apertures of different diameters formed therein.

Many people, especially children, find the use of a pair of compasses rather difficult, and it is also rather tricky to produce circles of small diameter accurately with a pair of compasses. In contrast, a stencil allows the accurate formation of circles of small diameter, but if it is desired to produce circles of a larger diameter then the stencils required tend to be rather large in size.

Furthermore, if one is to be able to produce circles of widely varying diameters, then it has been necessary to use a plurality of stencils.

One of my earlier devices, published in GB 2 237 245 goes a long way to solving these problems. It comprises an elongate planar base and a pivoting member located at each end. A series of apertures extends between the pivoting members and by inserting a pen or pencil in a selected one of the apertures the base may be pivoted around one of the pivoting members which is pressed into contact with the drawing surface. Circles and arcs may thereby be drawn.

Although this device is extremely useful, some users have found it difficult to draw circles of small diameter accurately, since the configuration can cause the pivot to slip on the drawing surface when the required increased pivoting force is applied.

It is an object of the present invention to provide a drawing instrument which overcomes or alleviates the problems associated with the prior art devices.

In accordance with a first aspect of the present invention, a drawing instrument comprises a generally planar base, a pivoting member rotatably mounted with respect to the base about an axis substantially perpendicular to the plane thereof, and a plurality of apertures in the base and in the pivoting member for receipt of a pencil, pen or other drawing implement.

By pressing on the pivoting member and inserting a drawing instrument in one of the apertures in the base, the base can be pivoted about the pivoting member by movement of the drawing implement thereby producing a circle or arc of a given, relatively large, radius.

For smaller radii, by pressing on the base and inserting a drawing instrument in one of the apertures in the pivoting member, the pivoting member can be rotated with respect to the base, thereby producing an arc or circle of a given radius.

This overcomes the problems associated with the prior art, and enables circles of a very wide range of radii to be drawn accurately and quickly.

Preferably, the apertures for receipt of a drawing implement are equally spaced apart, and in a preferred embodiment, they are arranged substantially radially with respect to the rotational axis of the pivoting member.

In one embodiment, the drawing instrument comprises a second pivoting member rotatably mounted with respect to the base about an axis substantially perpendicular to the plane thereof, and the apertures in the base for receipt of a drawing implement extend along an axis which intercepts the rotational axes of each of the pivoting members, the distance between the centre of one pivoting member and the apertures being equal to an even number of half the minimum radial increment, and the distances between the apertures and the other pivoting member being equal to an odd number of half the minimum radial increment. This allows, for example, radii to be drawn to a resolution of 0.5mm if the apertures permit radii to be drawn in steps of linin using one pivoting member alone.Such radii are also calibrated, in contrast to the position with, for example a conventional drawing compass.

The provision of two pivoting members at the aforementioned spacings from the apertures allows the drawing of circles and arcs having a radius of a length inbetween that which may be drawn using one pivoting member alone and enables the instrument to be used in a left- or right-handed mode.

In one embodiment, both pivoting members are provided with apertures for the receipt of a drawing implement.

One or both of the first and second members may project below the lower surface of the base, in order to allow improved frictional contact between the or each member and a drawing surface, when desired.

The instrument may also be provided with one or more slots extending radially from the centre of the or each pivot member. The slot may be in the body and/or in one or both pivoting members. This assists in the drawing of radial lines and is useful, for example, for drawing pie charts, chords and tangents.

Preferably the drawing instrument comprises a ruler portion having two parallel straight edges and a protractor portion located at one or each end of the ruler.

Preferably, the width of the or each protractor portion is substantially equal to the width of the ruler portion, so that the drawing instrument is in the form of two parallel edges joined at one or both ends by a semi-circular edge.

Advantageously, the two protractors located on the two ends of the ruler are arranged with their markings running clockwise and anti-clockwise, respectively, and preferably the or each pivoting member is located at the origin of a protractor portion, with the result that arcs of specified angular projection can be drawn.

By this means, four instruments can be combined into a single instrument.

In accordance with a second aspect of the present invention, a drawing instrument comprises a base portion and a rotatable portion mounted on the base portion, at least one of the base portion and the rotatable portion being provided with a slot extending radially with respect to the rotational axis of the rotatable portion for receipt of a drawing implement.

This arrangement enables radially extending lines to be drawn, and by adjustment of the relative angular orientation of the base portion and the rotatable portion, the drawing of lines which are inclined to one another is possible.

In one embodiment, each of the base portion and the rotating portion is provided with its own slot.

This enables short-radius lines to be drawn with the slot in the rotatable portion and large-radius lines to be drawn with the slot in the base portion.

Preferably, the instrument is provided with markings indicating the relative angular orientation of the base member and the rotatable member.

Preferably, the base portion and the rotatable portion are generally planar. The instrument may be provided with one or more straight edges parallel to a slot in the base, and the base portion may be provided with a protractor portion.

There may also be apertures in the base portion and/or in the rotatable portion for receipt of a drawing implement, to enable arcs or circles of predetermined radius to be drawn. Preferably both the base portion and the rotatable portion are provided with such apertures, and preferably each is provided with a series of apertures.

In one embodiment, a plurality of rotatable portions is mounted on the base portion, each rotatable portion being provided with a radial slot.

By way of example only, specific embodiments of the present invention will now be described, with reference to the accompanying drawings, in which: Fig.1 is a plan view of a first embodiment of drawing instrument in accordance with the present invention; Fig.2 is an enlarged cross-section looking in the direction of arrows II-II of Fig.1; and Fig.3 is a plan view of a second embodiment of drawing instrument in accordance with the present invention.

The drawing instrument is in the form of a generally oval, transparent plastics lamina 10 having two elongate parallel edges 12a, 12b joined at their ends by first and second semicircular edges 14a,14b.

The lamina 10 has substantially flat, parallel, planar upper and lower surfaces, but it will be noted from Fig.2 that the elongate edges 12a, 12b and the semicircular edges 14a,14b are bevelled.

The semicircular ends of the drawing instrument are each printed with protractor markings having 10 spacings. The protractor markings are printed on the undersurface of the instrument to reduce parallax errors.

The drawing instrument is also provided with two pivoting members 16,18 which are pivotable with respect to the lamina 10 about axes which are substantially perpendicular to the plane of the lamina. The pivoting members 16,18 are circular in plan and their centres coinccide with the centres of the semicircular ends formed by the semicircular edges 14a,14b respectively. The pivoting member 16 is larger than the pivoting member 18 and extends across most of the width of the lamina 10. The pivoting member 16 is also provided with a radially extending slot 20and two radially extending series of circular apertures 22a,22b. Adjacent apertures are spaced lmm apart, and the apertures 22a and 22b are offset by 0.5mm, so that circles of different diameters can be drawn, as will be explained.It will also be noted that the member 18 is provided with angular markings 24. The pivoting member 18 is similar, but is not provided with a slot or aperture.

The lamina 10 is provided with a straight elongate slot 26 extending parallel to the edges 12a,12b and between the centres of the two pivoting members 16,18. On each side of the slot 26 is provided a series of aligned, circular apertures 28a,28b arranged in a straight line, adjacent apertures being spaced apart by 2mm, and the apertures 28a being offset by lmm from the apertures 28b.

The pivoting member 16 is shown in more detail in Fig.2. The member is in the form of a flat cylinder 30 having a flat annular securing rim 32 extending from its cylindrical walls. The member 16 is received in an aperture in the lamina 10 which comprises a first bore 34 adapted to receive the lower portion of the cylindrical body 30 of the member 16 and a second, under bore 36 adapted to receive the annular rim 32.

The undersurface of the annular rim 32 rests on a flat shoulder 38 defined between the bores 34,36. The member 16 is held in place by means of a flat retaining ring 40 whose undersurface, in use, rests on a flat shoulder 42 defined between the second, wider bore 36 and a third, even wider bore 44. The undersurface of the ring 40 is provided with a plurality of spaced-apart lugs 46 which are adapted to be a press-fit in complementarily-shaped and located recesses in the shoulder 42. It will also be noted that the centre of the undersurface of the member 16 is provided with a central point 50, In practice, the various interengaging edges of the body 30 and the aperture are rounded, to provide a smoother movement, but this is not visible in the drawings.

Only the pivoting member 16 has been described in detail, but the construction of the other pivoting member 18 is identical apart from the fact that its size is reduced compared with that of the member 16.

Each pivot is provided with two pairs of intersecting cross wires 52, best seen in Fig.l, and the cross wires intersect directly above the apex of the small conical point 50. The centre of the lefthand pivot 16 is located 25mm from the nearest of the apertures 28a, and in use the cross wires 52 and cone 50 are placed at the centre of where the arc or circle is to be drawn, and the user presses downwardly on the upper surface of the pivot 16. By inserting a pencil, pen or other drawing implement in one of the apertures 28a,28b, the pencil may be moved to rotate the lamina 10 about the pivot 16, thereby forming an arc or circle.Since adjacent apertures 28 are spaced apart by 2mm intervals, circles or arcs differing by a radius of 2mm may be produced with the upper apertures 28a, e.g. with radii of 26mm, 28mm, 30mm, 32mm, etc., and circles or arcs having radii in between those produced by the apertures 28a, e.g. 25mm, 27mm, 29mm etc. may be produced with the lower apertures 28b. It will be noted that the apertures are not on an exact radius from the centre of the pivot 16, but the error involved in practice is negligible.

The other pivoting member 18 is positioned such that it is 13.5mm from the nearest aperture 28. Since adjacent apertures 28 are spaced apart by 2mm, the member 18 can be used in conjunction with the lower apertures to draw circles of radius 13.5mm, 15.5mm, 17.5mm etc., and can be used in conjunction with the upper apertures 28a to draw circles of radius 14.5mm, 16.5mm, 18.5mm etc.

Thus, by selection of the appropriate pivoting member 16,18 and apertures 28, circles of any radius from 13.5mm upwards can be drawn in steps of 0.5mm.

However, as mentioned previously, it can sometimes be difficult to draw circles as described above, when the radius is small. For drawing circles of small radius, the pivoting member 16 alone is used. As mentioned previously, the member 16 is provided with a series of apertures 22a,22b which are spaced radially outwardly in increments of 0.5mm from 5mm to 20mm. Thus, if it is desired to draw a circle with a radius of from 5mm to 20mm, it is merely necessary to insert a pen or pencil in the appropriate aperture 22, locate the centre of the member 16 over the centre point, hold the lamina firmly against the drawing surface and rotate the member 16 with the pen or pencil, thereby producing a circle having the desired radius. Circles of radii greater than 20mm can be produced using one of the pivoting members 16,18 in conjunction with the apertures 28a,28b.

In view of the fact that the above arrangement does not permit circles of radii 21mm, 22mm, 23mm or 24mm to be drawn, the lamina is provided with two further groups of apertures 52a,52b near the pivoting member 18, the upper group being located at distances of 20mm, 22mm and 24mm from the centre of the pivot 18 and the lower group being located at distances of 21mm, 23mum and 25mm from the centre of the pivot. The holes 28a,28b in conjunction with the pivot 18 permit circles of radii + 0.5mm different from the above radii to be drawn.

It will also be noted that the slots 20 and 26 enable radial lines to be drawn at a predetermined angle with respect to one another. If the length of the lines is small then the slot 20 alone may be used, the angle between the two lines being set by aligning one of the datum marks 24 on the member 16 with the appropriate angular settings on the protractor portion 14a, while holding the lamina steady. Similarly, longer lines can be drawn using the slot 26, the angle between the lines being set by moving the lamina 10 and holding the pivoting member 16 against the drawing surface, and again using the datum marks 24 in conjunction with the protractor portion 14a. Pie charts are particularly easy to draw by virtue of the above features.

It will also be noted that the drawing instrument comprises a number of stencil functions, including lettering A to Z, horizontal graph markings 54, a series of chain dot stencils 56, a dotted line stencil 58 and a plurality of other shapes such as rectangles 60, arrows 62 and small circles 64. It will also be noted that the elongate parallel straight edges are provided with ruler graduations printed on the undersurface of the lamina 10.

The second embodiment is very similar to the first embodiment, except that the small pivoting member 18 is replaced with a pivoting member 18' which is identical to the member 16 of the first embodiment.

However, the centre of the member 18' is located at the same point as that of the member 18 of the first embodiment, in order to increase the number of different radii available. The Fig.3 embodiment is very similar to the first embodiment, and identical reference numerals have been used to identify identical features. It will also be noted that the increased size of the member 18' necessitates the omission of some of the supplementary features, e.g.

the apertures 52.

The invention is not restricted to the details of the foregoing embodiments.

Claims

1. A drawing instrument comprising a generally planar base, a pivoting member rotatably mounted with respect to the base about an axis substantially perpendicular to the plane thereof, and a plurality of apertures in both the base and the pivoting member for receipt of a pencil, pen or other drawing implement.

2. A drawing instrument as claimed in claim 1, wherein the apertures for receipt of the drawing implement are at different distances from the rotational axis of the pivoting member.

3. A drawing instrument as claimed in claim 2, wherein the apertures are substantially equally spaced apart.

4. A drawing instrument as claimed in claim 2 or claim 3, wherein the apertures in the base and in the pivoting member are arranged substantially radially with respect to the rotational axis of the pivoting member.

5. A drawing instrument as claimed in any of the preceding claims, wherein the pivoting member projects below the lower surface of the base.

6. A drawing instrument as claimed in any of the preceding claims, further comprising a radially extending slot in the pivoting member.

7. A drawing instrument as claimed in claim 6, wherein the slot extends from the rotational axis of the pivoting member.

8. A drawing instrument as claimed in any of the preceding claims, wherein the pivoting member is generally planar.

9. A drawing instrument as claimed in any of the preceding claims, further comprising a slot in the base, extending substantially radially with respect to the rotational axis of the pivoting member.

10. A drawing instrument as claimed in any of the preceding claims, further comprising a second pivoting member rotatably mounted on the base about an axis substantially perpendicular to the plane thereof.

11. A drawing instrument as claimed in claim 10, wherein the apertures in the base for receipt of a drawing implement are substantially equally spaced apart and extend along an axis which intersects the rotational axes of the two pivoting members.

12. A drawing instrument as claimed in claim 11, wherein the distances between the pivotal axis of one pivoting member and the apertures in the base are equal to an even number of half the minimum radial increment and the distances between the pivotal axis of the other pivoting member and the apertures in the base are equal to an odd number of half the minimum radial increment.

13. A drawing instrument as claimed in any of claims 10 to 12, wherein the second pivoting member is provided with apertures for receipt of a drawing implement.

14. A drawing instrument as claimed in any of the preceding claims, comprising markings indicating the relative angular orientation of the base and a pivoting member.

15. A drawing instrument as claimed in any of the preceding claims, wherein the markings comprise a protractor portion whose origin coincides with the rotational axis of a pivoting member.

16. A drawing instrument as claimed in claim 15, wherein the base comprises a ruler portion having two parallel straight edges, the width of the ruler portion being substantially equal to the width of the protractor portion, the protractor portion being located at one end of the ruler portion.

17. A drawing instrument as claimed in claim 16, wherein the base comprises two protractor portions located one at each end of the ruler portion.

18. A drawing instrument comprising a base portion and a rotatable portion mounted on the base portion, at least one of the base portion and the rotatable portion having a slot extending radially with respect to the rotational axis of the rotatable portion for receipt of a drawing implement.

19. A drawing instrument as claimed in claim 18, wherein the base portion and the rotatable portion are each provided with a radially extending slot.

20. A drawing instrument as claimed in claim 18 or claim 19, comprising markings indicating the relative angular orientation of the base portion and the rotatable portion.

21. A drawing instrument as claimed in any of claims 18 to 20, wherein the base portion and the rotatable portion are generally planar.

22. A drawing instrument as claimed in any of the preceding claims, further comprising stencilling apertures.

23. A drawing instrument substantially as herein described, with reference to and as illustrated in Figs. 1 and 2 or Fig.3 of the accompanying drawings.