Compass, particularly for draughtsmen

Abstract: A bow compass includes a first (2) and a second (3) rod elements hinged to each other at their upper ends; a point (5) is associated with the lower end of the first element, and a fastening means (6) for a drawing means is associated to the lower end of the second element. The compass further includes a slider member (9), having a first end slidable in a first runner (7) in the first rod element, and a second end slidable in a second runner (8) in the second element; the runners are laid out in the rod elements such that a progressive shift of the slider corresponds to a progressive opening relatively to one another of the rod elements.

Description: The present invention relates to a compass, particularly to a draughtsman compass of the type usually called bow compass or spring bow compass. The bow compass is a compass adapted to draw circles or sections of circles of small radius and it is generally provided in two basic types. A first type of bow compass has two hinged rods holding a point at each of their lower ends; one of the points can be substituted by a lead holder or a drawing pen. A threaded bar has one end fastened to a median portion of one of the rods and engages a ring associated to the other rod but adapted to be rotated to finely adjust the distance between the two rods. In the other type of how compass, a rod element has a longitudinal bore in which a point is slidable along its longitudinal axis; a resilient member is associated to the rod element and its distance from the rod element itself, i.e. the aperture of the compass, is adjusted by means of a screw. A lead holder or a drawing pen can he fastened to the resilient member. British Patent No. 448.202 discloses a drawing compass wherein the legs are connected together by means of a link having an end engaging a slot in one of the legs. The bow compasses of the prior art are susceptible to improvements regarding their mechanical reliability and their operation, especially if their structure is provided in plastics, for example, instead of the usual metallic materials. The traditional bow compasses are also rather heavy in order to ensure a sturdy structure for a precise operation. The aim of the present invention is that of providing a compass for draughtsmen, particularly a bow compass, that, owing to a particular geometrical configuration, eases the hand movement in the drawing and at the same time ensures an absolute precision. Within this aim, an object of the invention, is that of providing a bow compass which is constructively simple and easy to use. Another object of the invention is that of providing a bow compass having low manufacturing costs. A further object, is that of providing a compass with a new and likeable styling. The above aim, as well as these and other objects that will be more apparent later, are achieved by a compass, particularly for draughtsmen, comprising a first and a second rod element, said second rod element being hinged to said first rod element at their upper ends, a point being associated with the lower end of said first rod element, a fastening means for a drawing means being associated with the lower end of said rod second element, a slider member having a first end slidable in a first runner in said first rod element, characterized in that said slider member has a second end slidable in a second runner, said second runner being laid out in said second rod element, a screw element being associated with said first rod element and being adapted to cooperate with a threaded bore of said slider such that to a rotation of said screw element corresponds an axial shift of said slider. Further characteristics and advantages of the invention will be more apparent by the following description of a preferred embodiment of the invention, illustrated, by way of example in the enclosed drawings in which: Fig. 1 is an isometric view of a bow compass according to the invention; Fig. 2 is a side elevated view of the bow compass; Fig. 3 is a sectioned side view of the bow compass; Fig. 4 is an isometric view of the slider element; Fig. 5 and 6 are side elevated view of the bow compass, respectively in the closed position and in a partially open position; Fig. 7 is partially sectioned side elevated view of the bow compass. With reference to the above figures, a draughtsman compass 1 will be described, of the type usually called bow compass, adapted to draw circles of small radius. The bow compass 1 comprises a first rod element 2 hinged to a second rod element 3 by means of an upper head 4. The lower end of the first rod element 2 has a point 5, while the lower end of the second rod element 3 has a fastening means 6 for drawing means such as, for example, a lead holder or a drawing pen, not illustrated in the drawings for brevity. On the first rod element 2, a first runner is provided by means of two rectilinear grooves 7, on opposite sides of the first rod element, parallely laid out on the axis of the same first rod element. A second runner is formed on the second rod element 3 and is provided by means of two grooves 8, again on opposite sides of the second rod element, slanted of a set angle relatively to the axis of the second rod element. The runners of the first and second rod elements are engaged by the ends of a slider element 9 comprising a core 10 and two plates 11 provided with pins 12 adapted to slide in the grooves 7 and 8. A threaded bore 13 is provided in the core 10 and is engaged by a screw element 14 supported on the first rod element 2. As better shown in Fig. 7, the screw element 14 is substantially at the axis of the first rod element 2 and is inserted upwardly in the hand grip 15 of the bow compass. A knob 16 is fastened on the upper end of the screw element to manually rotate the screw element itself. The operation of the bow compass is very simple, it is in fact sufficient to rotate the knob 16 for axially displacing the slider 9 causing the two rod elements 2 ,3 to open or close, adjusting the aperture of the compass, because of the relative configuration of the grooves 7 and 8. It has been practically observed how the invention achieves the intended aim and objects by providing a bow compass of great mechanical precision and at the same time of easy use; an advantage of the invention is that of the hand grip which is provided on the axis of rotation of the bow compass itself and which comprises also the aperture adjusting knob. Another advantage of the particular structure of the bow compass according to the invention is that of allowing the use of different materials still keeping a remarkable mechanical reliability. The materials employed, as well as the dimensions, may be any according to the specific needs and the state of the art. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: Compass (1), particularly for draughtsmen, comprising a first (2) and a second (3) rod element, said second rod element (3) being hinged to said first rod element (2) at their upper ends, a point (5) being associated with the lower end of said first rod element (2), a fastening means (6) for a drawing means being associated with the lower end of said second rod element (3), a slider member (9) having a first end (12) slidable in a first runner (7) in said first rod element (2), characterized in that said slider member (9) has a second end (12) slidable in a second runner (8), said second runner (8) being laid out in said second rod element (3), a screw element (14) being associated with said first rod element (2) and being adapted to cooperate with a threaded bore (13) of said slider (9) such that to a rotation of said screw element (14) corresponds an axial shift of said slider (9). Compass, according to claim 1, characterized in that said screw element (14) is operated by a knob (16) arranged at the hand grip (15) of the compass (1). Compass, according to claim 1, characterized in that said first runner (7) has a rectilinear configuration parallel to the axis of said first rod element (2), said second runner (8) having a rectilinear configuration and being slanted at an angle relatively to the axis of said second rod element (3). Compass, according to one or more of the preceding claims, characterized in that said first rod element (2) has an axis, said axis extending longitudinally and comprising said point (5) and said hand grip (15), said screw element (14) being laid out substantially at said axis.

Inventors: BERGONZI ROBERTO, BERGONZI, ROBERTO
Applicants: ILCA SPA, ILCA S.P.A.
Application year: 1990
Main classification: B43L9
IPC codes: B43L9