US2824373A - Compass - Google Patents

Description

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United States PatetltO COMPASS Ake Gottfrid Sjiilund, Stockholm-Vallingby, Sweden Application October 5, 1954, Serial No. 460,360 Claims priority, application Sweden October 5, 1953 4 Claims. (Cl. 33-27) This invention relates to compasses particularly of the type to be used by draftsmen, and a first object of the invention is to improve and simplify the general construction of such compasses in order to make them more adapted to an all-round use on the drawing desk or the like.

Another object of the invention is to provide compasses of a construction ensuring a correct drawing line and circular form of such line within a wide range comprising very small. as well as large circles of all diameters more frequently used in a drawing.

Further objects of the invention are to provide compasses having a locking device permitting the two compass legs to be rigidly retained in any selected angular relation to each other and to provide compasses of a con struction permitting a precision adjustment of the points of the compass legs relatively to each other in order to facilitate adjustment of the pencil or pen particularly in drawing small circles.

With, the above and other objects in view the invention consists in general of certain novel details of construction and combination of parts hereinafter fully described and illustrated in the accompanying drawing, wherein- Fig. 1 is a front elevation of a preferred form of the compasses according to the invention,

Fig. 2 is a side elevation thereof, and

Fig. 3 is a partial section taken along the line III-III in Fig. 2.

In the drawing, 1 designates a center needle or pin preferably made from steel and having a point 2 and a knurled button or head 3. The pin 1 extends through a tubular leg member 4, which is rotatably mounted on the pin but held against axial displacement relatively thereto. At its upper end, near the head 3 of the pin 1, the tubular leg member 4 has a knurled disc or flange 5. A slide member 6 embraces the leg member 4 and is vertically adjustable therealong. More particularly the slide member 6 comprises a piece of sheet metal which is bent partly around the leg member 4 so that its ends or shanks project laterally therefrom in parallelly spaced apart relationship. As will particularly appear from Fig. 1 the sheet metal piece is cut through by two horizontal, spaced apart slots 7 and 8 and a vertical slot 9 adjoining said horizontal slots so that two clamping jaws 11 and 12 integral with the slide 6 are formed. The jaw 11 has secured thereto a threaded pin 13 extending through a hole in the other jaw 12 and carrying at its outer end a knurled nut 14. By tightening the nut 14 the jaws 11 and 12 are pressed together and thus the slide member 6 may be clamped and locked to the leg member 4 in any desired vertical position.

Between the shanks of the slide member 6 there are pivoted two substantially parallel link rods 15 and 16 on vertically spaced apart and offset pivot pins 17 and 18 respectively. The lower ends of said link rods are pivoted to a link member 19 by means of pivot pins 20 and 21 respectively. The link member 19 is formed as a pencil 2,824,373 Patented Feb. 25, 1958 and includes a screw 22 and a knurled nut 23 for clamping a pointed lead 24 therein. The link rods 15 and 16 are preferably of equal length and the distance between the pivot pins 17 and 18 in the slide member 6 is equal to that between the pivot pins 20 and 21 in the link member 19 so that a parallelogram movement of the related parts is normally obtained.

To the upper portion of the link rod 15 there is secured a pin 25 forming a pivot for a link strip 26 having a longitudinal slot 27 therein. The threaded pin 13 is passed through this slot 27 so that the link strip will be firmly clamped to the slide member 6 as soon as the nut 14 is tightened. Thus the link rods 15 and 16 forming the second leg of the compasses are retained in a selected angular position relatively to the leg member 4 as soon as the slide member 6 is firmly clamped to the latter in suitable vertical position.

In use, the compasses so far described are first prepared by loosening the nut 14, adjusting the link rods 15 and 16 to the angular position necessary to obtain the desired radius of the curve or circle to be drawn and adjusting the vertical position of the slide member 6 relatively to the leg member 4 until the point of the lead 2 touches the drawing when the center pin 1 is perpendicular to the latter.

and 16 in set positions and the compasses are ready for drawing the desired curve or circle which is done by turning the knurled disc or flange 5 on the leg member 4. it will be clear that this causes the whole assemblage of the'leg member 4, the slide 6, the link rods 15and 16, and the lead 24 to rotate as a unit aboutthe vertical center pin 1. Since the center pin" 1 is held against axial displacement relatively to the surrounding leg member 4 there will be no danger of a varying radius of the curve or circle, and the parallelogram movement of the link system parts 6, 15, 16 and 19 will assure that the lead 24 always touches the paper at the same angle. This is, of course, particularly advantageous if the pencil is replaced by a drawing pen.

Evidently the compasses so far described may be used for drawing circles having a maximum radius which depends on the length of the link rods 15 and 16the latter occupying a position substantially at right angles to the leg member 4 when the maximum circle is drawn. The minimum radius on the other hand will obviously be obtained when the inner link rod 16 abuts the lower end portion of the tubular leg member 4. To avoid such a limitation the link rod 15 may be lengthened when necessary by an arrangement particularly illustrated in Fig. 3. in fact the rod 15 is cut or interrupted at 28 and the adjacent ends of the parts 29 and 30 thus obtained are threaded in opposite directions and interconnected by means of an externally knurled sleeve 31, which is internally threaded to receive the threaded ends of the parts 29 and 30.

By turning the sleeve 31 the length of the link rod 15 may be slightly varied and such variation will cause the pencil 19 to swing about the pivot pin 21 so that the point of the lead 24 may come very close to the point 2 of the pin 1 when the link rod 16 abuts the leg member 4. In fact, this arrangement makes it possible to use the compasses shown as a substitute for bow compasses when drawing very small circles, and it also makes possible a very delicate adjustment of the radius when the legs of the compasses are spread apart. Thus an allround instrument for correctly drawing all circles and curves having a radius between zero and a predetermined maximum is obtained.

Of course, the invention is not limited to the preferred form of the compasses herein shown and described but Then the nut 14 is again tightened to lock the slide member and the link rods 15 3 may be varied in several details within the scope of the appended claims.

I claim:

1. In a drawing compass; the combination of an elongated needle member pointed at one end, an elongated tubular leg member telescoping rotatably over said needle member with at least said pointed end of the latter projecting from the leg member and with the latter being held against axial displacement with respect to said needle member, a slide member displaceable axially on said leg member, clamping means for locking said slide member relative to said leg member in any adjusted position along the latter, two substantially parallel and spaced apart link rods pivoted, at one end, to said slide member for swinging in a common plane passing through the longitudinal axis of said leg member, a drawing element pivotally connected to the ends of said rods remote from said slide member, means for securing one of said link rods in any angular position with respect to-said leg member and ineluding said clamping means, and means interposed in at least one of said link rods operative to adjust the length of the related rod so that said drawing element can thereby he angularly displaced with respect to the axis of said leg member between a normal substantially parallel condition and a converging condition making possible the positioning of said element closely adjacent said pointed end of the needle member for the drawing of small diameter circles.

2. In a drawing compass; the combination according to claim 1, wherein said securing means includes a link member pivoted at one end to said one link rod and having an elongated slot receiving said clamping means of the slide member so that, when the latter is released for adjustment along said leg member, said link member is simultaneously released to free said link rods for angular adjustment relative to said leg member.

3. In a drawing compass; the combination according to claim 1, wherein said means interposed in at least one of the link rods to adjust the length of the related rod includes an open ended sleeve, said related rod including two separate, longitudinally aligned sections having oppositely directed threads on the adjacent ends which extend into said sleeve, said sleeve having internal threads corresponding to the threads on the adjacent ends of said rod sections so that rotation of said sleeve causes longitudinal movement of said rod sections toward and away from each other.

4. In a drawing compass; the combination according to claim 1, wherein said slide member resiliently embraces said leg member and said clamping means includes a screw extending acrosssaid slide member and a nut on said screw to contract said slide member on the leg memher, and wherein said securing means includes a link member pivoted, at one end, to said one link rod and having an elongated slot receiving said screw with the link member being disposed between said slide member and said nut to be held by the latter when the nut and screw contract the slide member on the leg member.

References Cited in the file of this patent UNITED STATES PATENTS 383,696 Bormann May 29, 1888 567,810 Klaui Sept. 15, 1896 807,660 Clutter Dec. 19, 1905 985,978 Coxhead Mar, 7, 1911 2,136,140 Langsner Nov. 8, 1938 FOREIGN PATENTS 419,225 Italy Mar. 17, 1947

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