US2156417A - Apparatus for tracing curved lines - Google Patents

Description

y 2, 1939- D. J. WITHERSPOON 2,156,417

APPARATUS FOR TRACING CURVED LINES Filed May 20, 193' 2 Sheets-Sheet l INVENTOR '3 David J IVz'lherspoon ATTORNEY D. WITHERSPOON APPARATUS FOR TRACING CURVED LINES May 2, 1939.

Filed May 20, 1937 2 Sheets-Sheet 2 ATTORNEY Patented May 2, 1939 UNITED STAT-ES PATENT OFFICE David John Witherspoon, New York,,Nj.-.Y., .asr signorto Bee-K0 Company, a corporation of New York Application May .20, 1937, Serial No. 143,680

1 Claim.

This invention corn-prisesnovel mechanism'tor tracing elliptical. and other outlines which shall have a predetermined curvature of mathematical exactness.

The preferred form of apparatus embodying my invention is primarily designed to trace the outlines of ellipses of different predetermined dimenions, with axes and foci having given locations, by means of a marker carried by a movable or floating member supported byadjustable spaced-apart pivots which are caused to simultaneously reciprocate along lines at right angles one to the other and parallel to-and overlying the axes of the desired ellipse. Such rotation causes said floating member to complete one revolution about constantly shifting axes perpendicular to the plane in which-said member has its movement of translation, or orbitalmotion. If, then, a marker lies in aplane in whichthe axes ofboth ivots also lie and outside 'of' the space between them, an ellipse will be traced.

The best construction for such apparatus embodying my invention at present known tome is illustrated in the accompanying two sheets of drawings in which Fig. 1 is a plan viewof the apparatus in position upon a sheet oidrawing paper or other plane surface on which the curves areto be traced.

Fig. 2 is a cross section on a vertical-plane'on line 22 of Fig. 1. In this view the apparatus is shown as equipped with a lead for tracing the curved line.

Fig.3 is anenlargeddetail elevation of one end of the-mainframe,the right hand end as shown in 1, partsbeing shown in-section.

Fig. 4 is an enlarged detail elevation of the lead carrier-shown in Fig. 2, but looking at the same f-rom'the rear of Fig. 2.

Fig. 5 is a similar detail of the carrier equipped with a pen for tracing the lines.-

Fig.6 is'a detail plan in section of the carrier for .themarker taken on line 6-ii'oi Fig. 2, and

Fig. '7 is adetail side elevationof amodifioation in which the marker is mounted on the other-end of the-rod 22,. which is assumed to have been shoved to :the left; looking, at Fig. 2, for this purpose.

Referringtothe drawings,the apparatus therein shown comprises the end castings :i i. l i, which may ibeiheldby thumb tacks 23; 23, on the drawing board or clamped thereto, said castings being rigidly .;.connected :together bythe parallel rods t,-a4,&which serve :asguides for the carriage 3 :sliding .fr'eelyzthereon. The .minor axis .of theellipse to tbeadrawn will lie vbelowrand between said rods sitions thereon by thumbscrewiilc ,Said clamp maybe supported on a. foot] member =19 (Fig 2) which is adjustable-enrod:- ZZ. which in; turnis adjustable. in.:9.' Thewheel. 29:;(whic ,may in some embodiments .of. my invention bereplaced by some other anti-friction device), isjpurnaled in IS and S1ld6S.OI',;I'O11S,:O1'1 thesurfaceofthe pa per. Pen-3 t or lead. l and :itsholder are-fialilfi-fid Ion the end of. rod :22 which. is adjlletable endwise i n mp m er eand can .be c amped in admsied position by setscrew t3. Said;. c lamp is :pivotally connected .at.W- (Fig- 1) -to. the apex of -the straight line motion..systern; .of llnkS 8,- 8b,' 8;, 8d, 89. The angle apexof: link pair 8e, 8 has a fixed pivot X'carried by onepf, the castings -;i i, I i, (Fig. 3).. Theangle.apex ofpairgt ,C,-(Fig, 1) is pivotally connected at Y- to the end ot, linlg- B; which swingsfreely abouta fixed point -Z. (Fig. 1-) also carried by II.

This straight .line .motionnneeha new per so, having :beemused ,for; dra

. gee ain curved lines bymountin zitein a different way from that here shown. and. placing-a marker at one of its pivoted -joints..-, {But-"its .use-to compel motion of a member connectedsto its;=pi vot along a straight line .at rightaanglesto that pass.-

.of guides 4, .4,;.outsideof the orbit .of any marker carried .by the revolving flat barj. or. red ;;2 .,and outside the path of other moving parts,; thus simplifying thewhole supporting;. construction. The function. .of .the stra tlin otionm ch nism is .-to. compel pivot W to. ,move always and l only in a path indicated by broken line L L in Fig. l which extends across and at right angles to the line of guides i, 6. This line of travel LL is also the major axis of the ellipse to be drawn when the marker I (Fig. 7) or SI (Fig. 5) is carried at that end of the movable member formed by parts 2, 5, 6, i, ii and 22, on which it is shown as being mounted in Figs. 1 and 2 of the drawings.

I 3 (Fig. l) is a tension spring which is used to maintain the straight line motion linkage under light strains all in the same direction at all its joints at all times so as to take up any slack therein. Otherwise watchmaking precision would be required in fitting all the six pivot joints therein included to prevent the links 8 to Br from shifting slightly in their relative positions under reversals of operating strains.

38 is a pointer adjustably mounted in the lower part of clamp 53 in line with the axis of the pivotal connection W to the straight line motion linkage. Consequently, this pointer will always travel along the major axis of the ellipse when the parts are in motion and a marker located on member 22 as shown in Fig. 2. It is prevented from sticking into or scratching over the paper 25 by the anti-friction support is for the lefthand end of rod 22 (looking at Fig. 2) previously described.

In the preferred construction of carrier for the marker shown in Figs. 2, 4 and 5 there is a downwardly projecting spindle 32 on the righthand end of rod 22 (looking at Fig. 2) on which the block 33 is adjustably mounted, being held in position thereon by setscrew 2G (Figs. 2 and 6). Block 33 is also perforated to receive the adjustable supporting member 35 which is held in position by setscrew 35 and has its lower end rounded so as to run smoothly over the paper 25 on which it rests. 36 is a swinging member hinged at 37 to block 33 and carrying at its free end either the pencil I of Figs. 2, 4 and 6, or the pen 3i of Fig. 5. An upwardly projecting spring finger 38 is supported on block 33. and provided with a small projection 39 adapted to register with a companion depression in the side of the member 36 when the latter is raised so as to lift the pen free of the paper as indicated in broken lines in Fig. 5. As member 35 is turned up so as to bring the middle of spring to (Fig. 4) above pivot 31, that also tends to maintain the pen M in such raised position. The lead 5 may be clamped in the usual type of split holder 26 which, in turn, is removably held in swinging member 36 by setscrew 21, as best shown in Fig. 4. When 2'5 is loosened lead holder 25 can be removed and pen M (Fig. 5) substituted for it, being also clamped in position by setscrew 2?, as shown in Fig. 4. The tension spring til (Fig. 4) is connected at one end to hinged member 36 and at the other to swinging member LlI which may be turned on its pivot 4 by handle 42 through an angle of degrees, further swinging motion thereafter being prevented by stop 43. The purpose of this adjustment of tension on spring as, is to give a greater downward pressure to the lead I by turning member 4! into the position shown in Fig. 4 while a lesser pressure is given to pen 3! (Fig. 5) by turning said member ll up into the position shown in Fig. 5 so as to diminish the tension on the spring .19 and also elevate its anchorage.

As indicated in Fig. '7 the entire marker mechanism carried by the member 32 may be shifted to the lefthand end of rod 22, the latter being moved to the left through the opening for it in the clamp member 9 (looking at Fig. 2) When this is done, if the parts are so arranged that the point of the lead or pen is to the left of the axis of pivot 5 (Fig. 1) the ellipse then traced will have its major axis running at right angles to that of any ellipse which would be traced with the parts in the position shown in Figs. 1 and 2.

To permit the movable, floating structure comprising crank 6, pivot 5, flat strip 2, clamp 9 and rod 22 to rotate easily in carriage 3, the ball bearings 24, 24, are provided at either side of the latter as indicated in Fig. 2.

The mode of operation of the apparatus shown in Figs. 1 to 6 may be analyzed as follows:

If pivot 5 and carriage 3 could be held stationary and disconnected from links 8, 8b, revolution of crank 6 would then cause lead I to describe a circle about pivot 5, but so long as pin W connecting clamp 9 to the parallel motion mechanism is retained and carriage 3 is free to move on its guides i, the pivot W forms a shifting center of revolution for the rigid swinging system of elements composed of lead I or pen 3! and said elements, whenever the user pushes crank handle '5 around through a closed loop path such as indicated by the arrows A, A, in Fig. 1.

Since pivot 5 moves to the right when crank handle 7 is pushed in the direction of the upper arrows, A, A, and carriage 3 moves in the same direction along guides 4, 4 (all as indicated in broken lines in Fig. 1) while lead I swings to the left as indicated by arrows B (and during the return half of the crank handle "I motion the reverse of the above movements occur) it will be seen that such to-and-fro motion of the shifting pivot center 5 will be progressively lengthening or shortening the effective radius of the would be circle (on one side or the other of the ellipse major axis L, L) which lead I may be considered as trying to describe around such pivot 5 as a theoretical center, A at any one moment. Consequently, such would be circle is thereby squeezed in at each side (as an elastic ring could be deformed into an ellipse by simultaneous opposing side pressures thereon); and the would be circle thereby becomes an ellipse B which is traced by the marker on the sheet of paper 25, beneath it.

The length of the major axis of such ellipse obviousy is twice the distance from the point of lead I to pivot 5, while that of the minor axis is twice the distance from said lead point to pivot W, since said pivot always travels back and forth along the major axis of the ellipse being drawn, at right angles to the line of the guides 4, i. If the marker were shifted to: the other end of rod 22, as indicated in Fig. '7, the reverse would be true, the ellipse then traced being. of the type indicated by arrows A, A.

When clamp 9 is adjusted on member 2 so that point W is beneath pivot 5, the rotation of handle '1 will cause lead I to describe a circle the diameter of which is determined by the distance of lead I from pivot ii. transition phase through which a series of ellipses like B of gradually decreasing eccentricity might merge into another series like A of gradually increasing eccentricity.

The center of the ellipse in either case coincides with the position occupied by the axis of pivot 5 when the parts are in the position shown in full lines in Fig. 1, that being the point at which the major and minor axes intersect. The broken Such circle would constitute the lines in Fig. 1 show the parts in a position as- 75 sumed when lead I is at some point D in the ellipse periphery up to left of the major axis L, L.

The foregoing analysis makes it clear that in setting the preferred form of apparatus here shown rod 22 should be so adjusted in clamp member 9 that the distance from lead I to W is half the minor axis of the desired ellipse, and thereafter clamp member 9 carrying rod 22 with it should be so adjusted on fiat bar 2 that the distance from lead I to 5 will equal half the major axis of such ellipse.

If the lengths and locations of the axes of any desired ellipse are given, the apparatus should be so placed that the medial line of guides 4, 4' overlies the major axis while the pointer 30 rests on the minor axis, and the castingsll, ll, then secured in that position by thumb tacks 23, 23. Thereafter the locations of the marker with reference to pointer 39, and that of said pointer with reference to pivot 5, can be properly adjusted as before explained.

Adjustments necessary to draw an ellipse conforming to other given data can be worked out by the user from the principles of operation hereinbefore outlined, or by experiment.

Having described my invention, 1 claim:

In an apparatus for accurately tracing an ellipse the combination of a main frame provided with a rectilinear guide and means for fastening it in a position such that said guide will extend in parallel and fixed relation to a plane surface on which such line is to be traced, a movable member provided at one point with pivotal means adapted to slide along said rectilinear guide, and mechanism comprising a swinging straight-line motion-producing device formed of a plurality of links pivoted together and provided with elastic means for maintaining all the pivots thereof continually under a strain in the same general direction sufficient to overpower any normal operative strains in opposite directions exercised thereon, said mechanism being pivoted at one point on said guide and at another point pivoted to said movable member, combined with a marker adjustably mounted on said movable member and adapted to bear on and move over any surface on which said main frame is supported; whereby, when said frame is held in fixed relation to such surface with said marker bearing thereon and said movable member is caused to revolve about the axis of said first mentioned pivotal means, the latter and said second point on said member at which it is pivoted to said straight-line motionproducing device are then severally compelled to travel along their respective rectilinear paths, thereby causing said marker to trace the predetermined ellipse, or portion thereof, on such plane surface.

DAVID JOHN WITI-IERSPOON.

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