DRAWING AID

Abstract: The principles of geometrical projection can be demonstrated with a drawing aid which preferably can be assembled from a kit of parts and which comprises an elongate base (10) carrying a number of object and image elements which can be set at different positions along the base and in different attitudes. These elements may com­ prise for example a sighting rod (19), a transparent sheet­ form element (17) which defines a picture plane and on which the user draws images, an object (15), and a reflector (18). Perspective, orthographic and oblique projections can be demonstrated with just the one instrument using appro­ priate slots and holes to mount the elements.

Description: DRAWING AID SPECIFICATION This invention relates to a drawing aid which is designed to facilitate the teaching of the principles of geometrical projection in drawing. The invention is particularly concerned with a drawing aid which in just the one instrument enables one to demonstrate the principles of geometrical projection which form the basis of a range of projections, for example perspective, orthographic and oblique projections. It is an object of the present invention to provide a drawing aid which enables the user to learn the principles of geometrical projection in a simple and clear manner. It is another object of the invention to provide a drawing aid which is cheap to produce and which, if desired, can be made from materials which enable the drawing aid to be produced in kit form for assembly by the user, thereby reducing the problems of storage and packaging, and also enabling the kit to be sent easily by post. In accordance with one aspect of the present invention there is provided a drawing aid comprising an elongate base, an object which is to be drawn arranged to be mounted on the base, a reflector which can be mounted on the base, and a transparent drawing plate which defines a picture plane also arranged to be mounted on the base, wherein the base is provided withaplurality of alternative mounting positions for said mounted elements to enable their relative positions to be varied in such a way that at least two types of projection drawings can be carried out. In accordance with another aspect of the invention there is provided a drawing aid comprising an elongate base arranged to support a number of objedt and image elements thereon including a sheet-form element on which the user can draw and which defines a picture plane, in which the base is provided with a plurality of apertures for the alternative mounting of said elements, the apertures being spaced and orientated such that at least two typesofprojection drawing can be carried out. Preferably, the drawing aid is such that one can carry out at least perspective, orthographic and oblique drawing. In a preferred embodiment, specific provision is also made for special forms of oblique projection, i.e. cabinet and cavalier projection. According to a preferred embodiment of the invention, the elongate base comprises a triangular cross-section tube which has holes and slots at spaced intervals along its apex. Preferably, the triangular cross-section tube can be formed from a flat sheet of material pre-cut with the necessary slots and holes and arranged to be folded into tubular form. A more detailed description of the drawing aid in accordance with the invention will now be given by way of example and with reference to the accompanying drawings, in which: Fig. 1 shows a first embodiment of drawing aid in accordance with the invention; and, Fig. 2 is a plan view of an alternative form of base for the drawing aid. Referring first to Fig. 1, it will be seen that the drawing aid which is here assembled from a kit of parts comprises a base or rack, indicated generally at 10. The rack 10 is here shown as consisting of two stiff cardboard sheets 11 and 12, scored and folded so that they form two triangular cross-section tubes which can be placed end to end and secured, for example b means of adhesive tape, around the central joint 13. In a preferred arrangement, the base is approximately 600 mm long. Alternatively of course, the base can be made in one piece, or in a greater number of pieces. The base or rack 10 is provided with a number of holes and slots, the purpose of which will be described hereinafter. The slots and holes are formed along the apex of the tube. In the case where the rack is formed from cardboard sheets, then the cardboard is preferably precut with the necessary slots and holes and is also preprinted with the necessary numbers and letters to identify the slots and holies. Alternatively, if the rack is a solid elongate bar, then the slots and holes would be drilled and cut into the solid. Similarly, if the rack has a cross-sectional shape which is other than triangular, then the necessary slots and holes would be provided in or along the appropriate sides and/or edges of the rack. The rack can also conveniently be printed or marked with a linear measuring scale 14. The several holes 01, 02, 03 04 which are spaced at intervals along the rack 10 are for the mounting of an object 15 which is to be drawn using the drawing aid. The object 15 is here shown as a cuboid, formed as an open framework of rods. This cuboid 15 is supported on a flexible wire 16 so that the object can be formed for example from plastics tubes cut to an appropriate length and joined at the corners by plastics three-way connector pieces 15'. At the bottom corner of the object 15 is a four-way connector piece 15'' by means of which the cuboid is attached to the wire 16. Alternatively, and preferably, the support wire 16 is rigid, not flexible, and a suitable universal joint (not shown) is provided to connect the wire 16 to the object 15 so that it can be orientated in different attitudes. A flat sheet 17 which defines a picture plane or projection plane is provided in the form of a sheet of rigid transparent material, preferably a plastics material. The user of the drawing aid can draw on this sheet 17, for example with a "chinagraph" pencil. A number of slots are provided in the rack 10 for the projection sheet 17, as will be described later. Also mountable on the rack 10 is a reflector 18. This is preferably a mirror made for example from a sheet of self-adhesive reflecting material supported on a cardboard sheet. Any reflecting material can be used for the reflector, provided that it has a plane surface and will produce images without substantial distortion. Naturally, a conventional glass mirror could be used, although this is less attractive in a kit-form drawing aid which is designed to be sent through the post. The reflector 18 is designed to be mounted in a slot M adjacent to one end of the rack, as indicated. As mentioned above, the drawing aid can be used to teach the principles of geometrical projection which form the basis of various types of drawing. The drawing aid of the present invention is particularly versatile in this respect because the range of possibilities is determined merely by the provision of appropriate holes and slots in the supporting rack. The rack shown in Fig. 1 is appropriate for perspective, orthographic and oblique drawings, although a simplified form of rack could be limited to a more restricted range of possibilities if desired. The method of using the drawing aid of Fig. 1 for different types of projection will now be described. For perspective drawing the viewpoint is designated by the top of a vertical rod 19 which is designed to be pushed into a hole E adjacent to one end of the rack. The reflector 18 is not used for perspective drawing. The object 15 is supported by the rack at one of the object holes 01, 2 03 or 04. The user places one eye at the viewpoint which the rod top provides, and draws on the surface of the picture plane sheet 17 the view of the object 15 which is seen. By altering the spatial attitude of the object 15 one can obtain one-, two- and three-point perspectives. The picture plane sheet 17 can be positioned in any of four slots PP1, PP2, PP3, PP4 spaced along the length of the rack, in each of which the picture plane sheet 17 is set at right-angles to the longitudinal axis of the rack 10. For orthographic drawing, the reflector 18 is placed in its slot M on the opposite side of the object 15 from the sheet 17 defining the picture plane. The viewpoint rod 19 at E is here discarded, The picture plane sheet 17 is now mounted in the slot marked Orth, parallel to the reflector 18. The user then aligns each corner-point of the object 15, e.g. the cuboid, with its own reflection and with the reflection of the pupil of his own eye, and marks its projected image on the picture plane sheet 17. Dimetric, trimetric and isometric views can be drawn in this way. In this embodiment of rack, greater provision is made for making oblique drawings. Two slots Cab and Cav are provided for making cabinet and cavalier projections respectively, each of these projections being special cases of oblique projection. These slots Cab and Cav are cut so that the picture plane sheet 17 is tilted forward towards the mirror and is also set' askew with reference to a transverse plane at right-angles to the longitudinal axis of the rack. It will therefore be appreciated that the drawing aid of the present invention is extremely versatile in the range of geometrical projections which can be demonstrated with it, and that it is also capable of construction in kit form for low cost and for ease of packing, storage and transportation.

Claims: CLAIMS: 1. A drawing aid comprising an elongate base arranged to support a number of object and image elements thereon including a sheet-form element on which the user can draw and which defines a picture plane, in which the base is provided with a plurality of apertures for the alternative mounting of said elements, the apertures being spaced and orientated such that ,at least two types of projection drawing can be carried out. 2. A drawing aid comprising an elongate base, an object which is to be drawn arranged to be mounted on the base, a reflector which can be mounted on the base, and a transparent drawing plate which defines a picture plane also arranged to be mounted on the base, wherein the base is provided with a plurality of alternative mounting positions for said mounted elements to enable their relative positions to be varied in such a way that at least two types of projection drawing can be carried out. 3. A drawing aid as claimed in claim 2, in which the reflector is a sheet-form element mounted at rightangles to the longitudinal axis of the base. 4. A drawing aid as claimed in any preceding claim, in which the base is provided with slots and holes to support the mounted elements. 5. A drawing aid as claimed in any preceding claim, in which the base comprises a triangular cross-section tube. 6. A drawing aid as claimed in claim 5, in which the tube is made from one or more sheets of material pre-cut with slots and holes for the mounted elements and folded ite tubular form. 7. A drawing aid as claimed in any preceding claim, in which the base enables the sheet-form element which defines the picture plane to be positioned in any of a plurality of positions each set at right-angles to the longitudinal axis of the base to enable perspective drawing to be effected. 8. A drawing aid as claimed in any preceding claim, in which the base enables the sheet-form element which defines the picture plane to be positioned at an inclined angle to the longitudinal axis of the base to enable oblique drawing to be effected. 9. A drawing aid as claimed in claim 8, in which the available orientations of the sheet-form element which defines the picture plane enable cabinet and/or cavalier projections to be drawn. 10. A drawing aid as claimed in any preceding claim, which includes as an object to be drawn in different projections a hollow cuboid formed from an open framework of rods mounted so that it can be orientated in different attitudes.

Inventors: STEADMAN, JOHN PHILIP
Applicants: THE OPEN UNIVERSITY
Application year: 1981
Main classification: G09B23
IPC codes: B43L13, G09B23