GB2226530A

GB2226530A - Apparatus for describing an elliptical curve

Info

Publication number: GB2226530A
Application number: GB8923805A
Authority: GB
Inventors: Peter John Fitch
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-10-21
Filing date: 1989-10-23
Publication date: 1990-07-04
Also published as: GB8825034D0; GB8923805D0

Abstract

Apparatus 10 is provided for describing a curve in the form of a true ellipse. Two guide elements 12 are provided in guide channels 13 which are formed in a cross-shaped base part 14. The guide channels 13 are straight and perpendicular and constrain the movement of the guide elements 12 to straight and perpendicular paths. An arm 11 interconnects the guide elements 12 so that on rotation of the arm 11, each part of the arm 11 describes a true ellipse. A tool, such as a drawing implement or a router may be mounted on the edge of the arm. <IMAGE>

Description

APPARATUS FOR DESCRIBING A CURVE The invention relates to apparatus for describing a curve.

Methods are known for drawing smooth curves. In one such method a curve in the form of a true ellipse may be described. A straight edge is taken and from a set starting point, points at the desired maximum and minimum half diameter distances of the ellipse to be drawn are marked on the straight edge. The edge is then placed so that the marked half diameter distances lie on different lines of a cross marked on a sheet of paper. The position of the starting point on the edge is marked on the paper. The edge is then rotated slightly and re-aligned with the lines of the cross so that a further mark can be made. When this has been done for a full rotation of the edge, the marks produced will lie on the line of the desired ellipse and may be joined up to form the ellipse.This method allows an ellipse of any desired maximum and minimum half diameter distances to be drawn, but is laborious and time consuming.

According to one aspect of the invention therefore there is provided apparatus for describing a curve comprising two guide elements, each guide element being constrained to move along a predetermined path, the paths being at an angle to one another, and an arm interconnecting the guide elements such that when the guide elements are moved along said predetermined paths, part of the arm describes a curve.

Thus, by means of the apparatus a smooth curve can be described.

The predetermined paths may follow any convenient course, as desired, and in a preferred embodiment one, and preferably both of the predetermined paths follow a straight line course.

According to another aspect of the invention, there is provided apparatus for describing a curve comprising two guide elements, each guide element being constrained to move in a straight line, the straight lines being at an angle to one another, and an arm interconnecting the guide elements such that when the guide elements are moved in said straight lines, part of the arm describes a curve.

The angle between the paths may be adjustable or may be fixed. Preferably, where the paths are straight, the angle is 90e so that the curve described is an ellipse.

Thus, an ellipse can simply and quickly be described using the apparatus.

The guide elements may be fixed in position with respect to the arm and may be integral therewith. Preferably, however, at least one of the guide elements is a separate component to the arm and is connectable to the arm at a number of different positions thereon so as to be adjustable. In this way, curves of different sizes and curvatures can be described, and, in the case of an ellipse, the maximum diameter, the minimum diameter, or both diameters can be adjusted.

At least one of the guide elements may be connected to the arm by an intermediate member.

Preferably, the arm is received in an arm bore in the intermediate member and is held against an inner wall of the arm bore by a securing member. Preferably, the securing member is a screw threaded member mounted in a screw threaded bore in the intermediate member which intercepts the arm bore. Thus, a securing member may simply be unscrewed to release the connection between a guide element and the arm and the relative position of the two components may be adjusted and the connection remade by screwing in of the securing member.

Preferably each guide element is arranged to slide within a guide channel defined by a guide part of the apparatus, thereby being constrained to move along a predetermined path. Each guide element may include a lateral projection which is received in a complementary groove in a wall of its respective guide channel such that the guide element is prevented from moving perpendicularly out of the channel although any other suitable means of preventing such movement may be employed. Preferably, each guide member includes a pair of said lateral projections in opposed positions which are received in complementary grooves in walls of its respective guide channels. The contact surfaces of the guide elements are preferably made from a material providing a low coefficient of friction between the guide elements and the guide channels.The contact surfaces of the guide elements may be made from nylon or the like, and in a preferred embodiment the guide elements are made entirely from nylon or the like.

The guide channels may intersect each other in a simple form of the invention or alternatively may be at different spacings from the arm so that the guide elements cannot contact each other when moved.

The apparatus preferably includes non-slip means to inhibit movement of the guide parts on a work surface.

The non-slip means may comprise sharp projections on the lower surface of the guide parts or may comprise any other suitable means.

The guide parts may be integral. Thus, where the straight lines are at 900, the guide parts will form a cross.

The guide parts may be made from any suitable material and may be made from aluminium or plastics material.

The arm preferably includes mounting means for mounting a tool which may, for example, be a drawing implement or a cutting tool such as a router. The mounting means may comprise a flat plate arranged to slide in use over a work surface. The flat plate may be connected to the arm by an upward extension thereof.

The arm may be made from aluminium bar or plastics material or from any other suitable material.

In order that the length of the arm may be adjustable so that curves in a wider range of sizes can be described using the apparatus, the arm may comprise a plurality of pieces which may be adjusted to be connectable at different positions to provide different lengths for the arm. Alternatively, the arm may comprise a plurality of pieces, one of which is removable and may be replaced by equivalent pieces of different lengths. The pieces may be connectable such that a guide element is not prohibited from connection at the inter-piece connection position. Preferably the pieces are matingly connectable so that the width of the arm is not increased at the connection position. The mating connection may comprise a stud and screw threaded bore.

One embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a plan view of the embodiment, Fig. 2 is an elevation of the embodiment, Fig. 3 is a detailed elevation in cross-section of part of the embodiment, and, Fig. 4 is a detailed elevation in cross-section of part of the embodiment shown in Fig. 3 viewed from one end.

Apparatus 10 comprises an arm 11 pivotally connected to guide elements 12 which slide in guide channels 13 defined in a base part 14. The base part 14, which constitutes an integral pair of the aforesaid guide parts, is in the shape of a cross about the guide channels 13.

As shown in Fig. 2, the guide channels 13 include opposed lateral grooves 15 for receiving opposed lateral projections 16 on the guide elements 12. The guide channels 13 thus have the cross sectional form of an inverted "T". The projections 16 on the guide members 12 insure that they can not be raised out of the guide channels 13 in use.

Each guide element 12 is rotatably connected to an intermediate member 17 by means of a screw 18. The screw threaded part 19 of the screw 18 is received in a screw threaded bore 20 in the intermediate member 17. Adjacent the screw threaded part 19 is a non screw threaded larger diameter part 21 and adjacent that the head 22. Each guide element 12 includes a bore complementary to the unthreaded parts 21, 22 of the screw 18 so that the head 22 of the screw 18 does not project from the lower surface of the guide element 12, and the guide element 12 is journalled for rotation on the screw 18.

The arm 11 is received in through bore 23 in the intermediate member 17. The relatie positions of the arm 11 and a guide element 12 are fixed by a securing member 24. The securing member 24 includes a screw threaded portion 25 and a head portion 26. The screw threaded portion 25 is received in a screw threaded bore 27 in the intermediate member 17 which intercepts the arm bore 23.

The head 26 of the securing member 24 includes four outwardly extending projections 28 so that it is easily manually turned.

When the securing member 24 is screwed in, the end of the securing member 24 enters the arm bore 23 and engages with the arm 11 pushing it against the far wall of the arm bore 23 to hold the arm 11 in position. The relative positions of a guide element 12 and the arm 11 can be adjusted by unscrewing of the securing member 24 and movement of the guide element 12 along the arm 11, following which the guide element can again be fixed in position on the arm 11 using the securing member 24.

At one end of the arm 11 is secured a plate 29. The plate 29 includes an upwardly extending part 30 connected to a further horizontally extending part 31 to which the arm 11 is attached. In the embodiment shown the plate is arranged to mount a router and thus includes a central circular aperture 32 and a pair of oppositely disposed screw threaded bores 33. The lower surface 34 of the plate 29 and the lower surface 35 of the base part 14 are arranged to be in the same plane so that when the base part 14 is placed on a surface, the plate 29 will also rest on the surface and will slide thereover.

The apparatus may thus be used to cut an elliptical shape using a router (not shown) mounted on the plate 29. In order to set up the apparatus, the guide element furthest from the plate 29 should be placed at the centre of the guide channel cross. The securing member 24 should then be unscrewed to release the arm 11 and the plate 29 should be moved to a position corresponding to the desired maximum diameter of the ellipse to be cut. The securing member 24 should then be screwed in again to fix this distance between the guide element and the flat plate 29. The arm 11 should then be moved so that the other guide element 12 is positioned centrally in the guide channel cross.The position of the flat plate 29 should again be adjusted by release of the securing member 24 appropriate to the guide member 12 so that the flat plate 29 will position the router at the desired minimum diameter distance of the ellipse. The securing member 24 should then be screwed in again to hold the arm 11 in position. A router is then secured to the plate 29 using screws in the the screw threaded bores 33, and may be used to cut an ellipse of the desired dimensions.

The base part 14 may be formed from aluminium and similarly the arm 11 may be an aluminium bar and the plate 29 may be formed from aluminium plate. The base part is preferably cast to include grooves corresponding to the guide channels 13 and is then machined to provide the grooves 15. The aluminium parts may be black anodised to improve appearance and corrosion protection.

The guide elements may be made from nylon or the like to provide a low coefficient of friction between the guide elements 12 and the base part 14.

The arm 11 need not be attached to the plate 29 which is arranged to mount a router, but may be attached to mounting means of any suitable type for mounting any desired tool so that, for example, a pencil may be mounted for drawing an ellipse, or oxy-acetylene equipment may be mounted for cutting an ellipse from sheet metal.

As the apparatus describes a fixed ellipse, a router, for example, may be used to travel the same elliptical path on a piece of wood several times without loss of accuracy from the jig, thus reducing strain on the tool and allowing deeper and more accurate cuts to be made.

The guide elements 12 need not be adjustable on the arm 11 as shown but may be adjustable in any suitable way.

Similarly, the position of the guide elements 12 on the arm 11 need not be adjustable, but may be fixed if desired.

The guide channels 13 need not be shaped as shown, but may be of any suitable shape and need not be shaped to prevent the guide elements 12 from moving upwardly out of the channels 13. Similarly, the channels 13 need not be formed within the base part 14 but may be formed by upwardly extending rails on the base part 14.

In another embodiment, the angle between the two guide channels 13 is adjustable so that curves other than a true ellipse can be described by using the apparatus.

In a further embodiment, in order that the guide elements 12 should not interfere with one another the guide channels 13 may be arranged at different levels so that in use the guide elements pass over one another without contacting each other. The guide elements need not be elongate as shown, however, but may be shorter, or, for example, disk shaped. However, the elongate shape shown provides a smooth sliding action.

Where the apparatus is to be used for small scale work such as for drawing ellipses in schools, the apparatus as shown may simply be reduced in size, and if desired, may be made from a different material, such as plastics. In such a case, where the guide parts of the apparatus are relatively light, means, such as projections on the lower surface of the guide parts, may be provided for preventing the guide parts from moving while a curve is being described.

While specific reference has been made to apparatus in which the guide elements are constrained to move in straight lines, apparatus is also envisaged in which at least one of the guide elements moves along a path other than a straight line, such as a smooth curve, for example.

Claims

1. Apparatus for describing a curve comprising two guide elements, each guide element being constrained to move along a predetermined path, the paths being at an angle to one another, and an arm interconnecting the guide elements such that when the guide elements are moved along said predetermined paths, part of the arm describes a curve.

2. Apparatus as claimed in claim 1, wherein one guide element is constrained to move along a straight line path.

3. Apparatus as claimed in claim 2, wherein both guide elements are constrained to move along straight line paths.

4. Apparatus as claimed in any preceding claim, wherein the angle between the paths is fixed.

5. Apparatus as claimed in claim 4 when dependent on claim 3, wherein the angle between the straight line paths is 90".

6. Apparatus as claimed in any preceding claim, wherein at least one of the guide elements is a separate component to the arm and is connectable to the arm at a number of different positions thereon so as to be adjustable.

7. Apparatus as claimed in any preceding claim, wherein at least one of the guide elements is connected to the arm by an intermediate member.

8. Apparatus as claimed in claim 7, wherein the arm is received in an arm bore in the intermediate member and is held against an inner wall of the arm bore by a securing member.

9. Apparatus as claimed in claim 8, wherein the securing member is a screw threaded member mounted in a screw threaded bore in the intermediate member which intercepts the arm bore.

10. Apparatus as claimed in any preceding claim, wherein each guide element is arranged to slide within a guide channel defined by a guide part of the apparatus, thereby being constrained to move along a predetermined path.

11. Apparatus as claimed in claim 10, wherein each guide element includes a lateral projection which is received in a complementary groove in a wall of its respective guide channel such that the guide element is prevented from moving perpendicularly out of the channel.

12. Apparatus as claimed in claim 11, wherein each guide member includes a pair of said lateral projections in opposed positions which are received in complementary grooves in walls of its respective guide channels.

13. Apparatus as claimed in any of claims 10, 11 and 12 wherein the contact surfaces of the guide elements are made from a material providing a low coefficient of friction between the guide elements and the guide channels.

14. Apparatus as claimed in claim 13, wherein the contact surfaces of the guide elements are made from nylon or the like.

15. Apparatus as claimed in claim 14, wherein the guide elements are made entirely from nylon or the like.

16. Apparatus as claimed in any of claims 10 to 15, wherein the guide channels are at different spacings from the arm so that the guide elements cannot contact each other when moved.

17. Apparatus as claimed in any of claims 10 to 16, wherein the apparatus includes non-slip means to inhibit movement of the guide parts on a work surface.

18. Apparatus as claimed in claim 17, wherein the non-slip means comprises sharp projections on the lower surface of the guide parts or may comprise any other suitable means.

19. Apparatus as claimed in any of claims 10 to 18, wherein the guide parts are integral.

20. Apparatus as claimed in any of claims 10 to 19, wherein the guide parts are made from aluminium.

21. Apparatus as claimed in any of claims 10 to 19, wherein the guide parts are made from plastics material.

22. Apparatus as claimed in any preceding claim, wherein the arm includes mounting means for mounting a tool.

23. Apparatus as claimed in claim 22, wherein the mounting means comprises a flat plate arranged to slide in use over a work surface.

24. Apparatus as claimed in claim23, wherein the flat plate is connected to the arm by an upward extension thereof.

25. Apparatus as claimed in any preceding claim, wherein the arm is made from aluminium bar.

26. Apparatus as claimed in any of claims 1 to 24, wherein the arm is made from plastics material.

27. Apparatus as claimed in any preceding claim, wherein the arm comprises a plurality of pieces which may be adjusted to be connectable at different positions to provide different lengths for the arm.

28. Apparatus as claimed in any of claims 1 to 26, wherein the arm comprises a plurality of pieces, one of which is removable and may be replaced by equivalent pieces of different lengths.

29. Apparatus as claimed in claim 27 or 28, wherein the pieces are connectable such that a guide element is not prohibited from connection at the connection position.

30. Apparatus as claimed in claim 29, wherein the pieces are matingly connectable so that the width of the arm is not increased at the connection position.

31. Apparatus as claimed in claim 30, wherein the mating connection comprises a stud and screw threaded bore.

32. Apparatus for describing a curve substantially as described herein with reference to the accompanying drawings.