GB2213947A - Drawing instrument - Google Patents

Abstract

A drawing instrument 1 comprises a roller parallel to a first straight edge 2 and which contacts the drawing surface. The roller is provided with three calibrated scales and as the instrument is moved in the direction normal to the first edge, the scales indicate the distance moved by each straight edge 2, 3, 4 in the direction of the normal to each such edge. The instrument may be provided with other drawing aids such as a protractor 21 and circle drawing holes 22. <IMAGE>

Description

"Drawing Instrument" This invention relates to a drawing instrument.

Many different types of drawing instruments have been developed over the years to facilitate the accurate preparation of drawings, and in particular technical drawings. Such drawing instruments include rulers, set squares, protractors etc.

One problem that has not been met by such drawing instruments in the past is the difficulty of drawing accurate spaced parallel lines, and in particular where such lines are at an angle to a predetermined direction. Furthermore, in prior designs, one particular instrument can only perform one task.

Viewed from one broad aspect the present invention provides a drawing instrument comprising a straight edge and a roller element mounted with its axis at an angle to said straight edge, wherein said roller element has associated therewith a calibrated scale for measuring the distance moved by said straight edge in the direction normal to said edge when the drawing instrument is moved in a direction normal to the axis of the roller.

By means of this arrangement, it is possible to draw parallel lines that are spaced by a desired distance and are at an angle to a predetermined direction.

In a preferred form the drawing instrument comprises a first straight edge parallel to the roller axis and a second straight edge at an angle to said first straight edge.

Preferably the drawing instrument further comprises a third straight edge at a second angle to said first edge and wherein said roller element has associated therewith a second calibrated scale for measuring the distance moved by said third edge in a direction normal to said third edge when the drawing instrument is moved in a direction normal to said axis.

The angles of said second and third edges relative to said first edge may be any desired value, but typical preferred angles would be 300 and 450.

Preferably the roller element may also have associated therewith an additional scale calibrated for measuring the distance moved in the direction parallel to the roller axis.

In their simplest form each calibrated scale may comprise indicia, for example printed, on the roller element. Another possibility would be to provide an electronic, mechanical or other type of sensor for detecting rotation of the roller element and connected to a digital, analog or any form of display means.

The roller element is preferably retractable from an operative position to a non-operative position.

This may be achieved in many ways, but in a preferred embodiment the roller element is mounted between a pair of support arms, the suport arms being pivotally mounted in a roller element housing and being pivotable between said operative and non-operative positions.

In addition to the roller element, the drawing instrument may be provided with other features to aid a drawing operation. In a particularly preferred embodiment the instrument may have a series of circle drawing holes. Preferably the holes are so spaced that the circles that may be drawn, by rotating the instrument about one hole with a drawing implement in another hole, increase incrementally in radius by lmm steps in any convenient range, e.g. from 14mm to 213mm. Another possibility is that the drawing instrument may be provided with a protactor element.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is an exploded perspective view of a drawing instrument according to an embodiment of the present invention, Fig. 2 is a perspective view of the roller housing, Fig. 3 is a perspective view along the line A-A in Fig. 2, Figs. 4(a) and (b) are end elevation views of the roller housing with the roller in non-operative and operative positions respectively, Fig. 5 is a view of a roller element, and Fig. 6 is a view of circle drawing holes.

Referring firstly to Fig. 1 there is shown a drawing instrument 1 of a generally triangular shape. The drawing instrument has three straight edges 2,3 and 4 which are provided with graduations at a suitable spacing, e.g 1 mm. The straight edges may be used for drawing lines or for measuring the distance between points in a conventional manner.

In this embodiment the second straight edge 3 is at an angle of 300 to the first edge 2, and the third straight edge 4 is at an angle of 450 to the first edge, but other angles could be chosen.

A roller 5 is rotatably mounted in a roller housing 6 through support arms 7, in a manner to be described below, with its axis parallel to a first straight edge 2. As will also be described below the roller 5 is movable between operative and non-operative positions. In its operative position, a part of the roller 5 passes through a rectangular aperture 8 formed in the drawing instrument so that in use it may contact a drawing surface.

The roller 5 is provided with three scales 9, 10, 11 which may be either printed on the roller, moulded with the roller or applied in any other conventional form. The scales 9, 10, 11 are viewed through a transparent window 12 framed in the roller housing. The window may be also provided with a fixed mark or pointer by means of which movement of the scales may be judged.

The scales are calibrated so that as the drawing instrument is moved in the direction normal to the first straight edge 2 and the roller rotates each scale measures the distance moved by one straight edge in the direction normal to that straight edge.

Thus, as the drawing instrument is moved in a direction normal to the first straight edge 2, one scale measures the distance moved in that direction; a second scale measures the distance moved by a second straight edge 3 in the direction normal to the second edge 3; and the third scale measures the distance moved by the third straight edge 4 in the direction normal to the third edge 4. It is thus possible to draw accurately spaced parallel lines, and in particular such lines at an angle to a first line or series of parallel lines.

The mounting of the roller 5 within the roller housing 6 will now be described, it being noted that the mounting arrangement is the same at each end of the roller and therefore only one end will be described.

As is shown in Figs. 1 and 3, a cap 13 is fitted tightly over the end of the roller 5, the cap 13 in turn being provided with a pin 14. The pin 14 is located in a pin locating hole 15 provided substantially half-way along support arm 7. The fit of the pin 14 in hole 15 is sufficiently loose to permit the roller 5 to rotate freely about its axis.

The support arm 7 is provided at one end with a pin 16 which is received within a pin locating hole 23 provided in the roller housing 6 in such a manner that the support arm 7 may be pivoted about the pin 16. To enable the arm to be pivoted, one end of the arm extends through a slot 20 formed in the roller housing. At the other end of the support arm 7 from the pin 16 there is provided a boss 17. The roller housing is formed with two boss receiving recesses 18,19 at each end, corresponding to operative and non-operative positions of the roller.

In the operative position, the boss 17 is received in the lower 18 of the two recesses, and as can be seen from Fig. 4(b) the cap 13 of the roller 5 extends through the aperture 8 to contact the drawing surface. To retract the roller 5 to its non-operative position the support arm 7 is flexed inwardly until the boss 17 is disengaged from recess 18. The support arm is then pivoted upwardly about pin 16 in the direction of the arrow in Fig. 2 until it is the direction of the arrow in Fig. 2 until it is in the position shown by broken lines in Fig. 2 and boss 17 engages recess 19. In this position, as is shown in Fig. 4(a), the roller 5 does not extend through the aperture 8. To move the roller from its non-operative to operative position the above procedure is simply reversed.

In addition to the roller 5, the drawing instrument may be provided with other means to facilitate accurate drawing, for example a protractor 21 formed as an arc cut out of the instrument.

The drawing instrument is also provided with a series of circle drawing holes 22. Using these holes a circle may be drawn by fixing a pin or the like through a first hole and the tip of a drawing implement through a second hole. By rotating the drawing instrument about the first hole a circle is drawn having a radius corresponding to the distance between the two holes.

Fig. 6 shows in detail the spacing of the holes, the figures above the holes giving the distance in millimetres of that hole from a central reference hole. It will be seen that the holes are divided into five groups, a first spaced by 5mm, a second spaced by lOmm, a third spaced by 5mm, a fourth spaced by 7mm and lastly a fifth spaced by 9mm.

In total there are 36 holes, but there may be different numbers in different arrangements.

The smallest circle that can be drawn is of Smm radius, and the largest of 245mm radius.

With these spacings a series of. circles can be drawn having radii increasing in lmm steps from 14mm to 213mm, in this example. As an example a circle of 117mm radius can be drawn usng the holes spaced 10mm in one direction and 107mm in the other direction, 56mm can be achieved using holes spaced at 35 mm and 21mm, and so forth.

The drawing instrument is preferably made of plastics material, and in particular generally transparent plastics material, and may be manufactured by a batch process. The roller housing 6 is preferably translucent with either a transparent window 12 or an opening forming the window.

Claims (13)

CLAIMS:

1. A drawing instrument comprising, a first straight edge and a roller element mounted with its axis at an angle to said straight edge, wherein said roller element has associated therewith a calibrated scale for measuring the distance moved by said straight edge in the direction normal to said edge when the drawing instrument is moved in a direction normal to the axis of the roller.

2. An instrument according to claim 1 comprising a first straight edge parallel to the roller axis and a second straight edge at an angle to said first straight edge.

3. An instrument according to claim 2 further comprising a third straight edge at an angle to said first edge and wherein said roller element has associated therewith a second calibrated scale for measuring the distance moved by said third edge in the direction normal to said third edge when the drawing instrument is moved in a direction normal to said axis.

4. An instrument according to claim 3 wherein one of said second and third edges is at an angle of 300 to said first edge, and the other of said second and third edges is at an angle of 450 to said first edge.

5. An instrument according to any preceding claim wherein said roller element has associated therewith a calibrated scale for measuring the distance moved in the direction normal to the axis of the roller.

6. An instrument according to any preceding claim wherein each said calibrated scale comprises indicia on the surface of said roller element.

7. An instrument according to any of claims 1 to 5 wherein a sensor is provided for detecting rotation of the roller element, said sensor being connected to display means calibrated to display the distance moved by said straight edge.

8. An instrument according to any preceding claim wherein said roller element is retractable from an operative position in which said roller element contacts a drawing surface to a non-operative position.

9. An instrument according to claim 8 wherein said roller element is mounted between a pair of support arms, said support arms being pivotally mounted in a roller element housing and being pivotable between said operative and non-operative positions.

10. An instrument according to any preceding claim further comprising a series of circle drawing holes.

11. An instrument according to claim 10 wherein said holes are so spaced that the circles that may be drawn increase incrementally in radius by lmm from 14mm to 213mm.

12. An instrument according to any preceding claim further comprising a protractor.

13. A drawing instrument substantially as hereinbefore described with reference to the accompanying drawings.