US2138494A - Curve plotting and drafting instrument - Google Patents

Description

NOV. :29, l g 5 K 2,138,494

CURVE PLOTTING AND DRAFTING INSTRUMENT Filed Nov. 21, 1936 V I; 4L 5 a v is f f 54' ii Mzwas B.K8wx,

Patented Nov. 29, 1938 UNE'EEB STTES OFFlE CURVE PLOTTING AND DRAFTING INSTRUMENT 1 Claim.

My present invention relates to means for plotting and drafting curves, and more particularly aims to provide instrumentalities for that purpose which are readily adjustable to suit requirements for numerous different curves, yet are simple in structure and inexpensive of manufacture.

In the drawing illustrating by way of example certain embodiments of the invention,

Fig. 1 is a longitudinal edge View of one instrument in accordance with the invention, appearing in its collapsed or non-use position;

Fig. 2 is a plan View of one fiat face or side of one element of the instrument of Fig. 1, in similar condition as there;

Fig. 3 is a view similar to Fig. 2 of the other main element of the instrument of Fig. 1;

Fig. 4 is an enlarged perspective of a holding member, slider or clip useful with the instrument of my invention and forming a part thereof;

Fig. 5 is an enlarged end view of the instrument, showing a holding member in position thereon;

Figs. 6, 7, 8 and 9 are longitudinal edge views of the instrument of Figs. 1 to 3, illustrating several different typical positions of use;

Figs. 10 and 11 are edge views corresponding to one end portion of Figs. 1, the left in said figure, illustrating modified constructions, and

Fig. 12 illustrates one distinctive use position of the instrument of Fig. 11, supplemental to such positions as those of Figs. 6 to 8.

Referring to the drawing in more particular the instrument of my invention, in its form as shown in Figs. 1 to- 9 by way of example, comprises a plurality of main elements, bars or strips, two being illustrated in this instance, designated 53 and l l. These strip members or columns are formed of any suitable material having an inherent elasticity permitting them to be flexed readily into such typical positions as shown in the figures, which positions it will be understood are by no means the extremes or representative of the wide range of curvatures which may be obtained with the instrument. While the material employed is elastic and such as to afford the high degree of flexibility indicated, the strips of the instrument also have a substantial inherent stifIness, so that they are self-sustaining in their various positions of adjustment, and are susceptible of loading, either by way of longitudinal Compression or tension, and in the several positions will retain each a regular smooth curvature characteristic of the position and condition of loading, without introducing local irregularities.

One such material which I have found highly satisfactory for the purpose is a fairly high-grade tempered steel, in most cases a blued steel, having the general characteristics of that commonly used in the manufacture of flexible razor blades of the wafer type, but preferably somewhat thicker or heavier. Other materials of the requisite character may be employed, however, including various compositions, such as phenol condensation products, cellulosic compositions and others.

Turning again more particularly to Figs. 1 to 3 the strips l3 and M. as there shown have corresponding ends provided with means for interengaging them so as to limit relative lengthwise movement in at least one direction. In the construction as in Figs. 1 to 9 I have shown for this purpose one or more nibs or hooks I5 at the end of one strip, herein the member !3, two such hooks being illustrated in the present instance. They each comprise, as best seen in Fig. 1, a lateral portion and an extension or hook proper i5 These projections or hooks are adapted to be received in correspondingly located apertures l5, [6 in the other strip member Hi.

In the collapsed or non-use position of the instrument, as in Fig. 1, the members 53 and I 4 are placed together flatwise, generally with the end formations l5 and I6 interlocked as illustrated. They may be retained in this position, and also in their various positions of relative adjustment as in the other figures to be referred to, by suitable adjustable holding means adapted to be enaged with the strips at various positions along them. For this purpose I preferably employ one or more holding members in the nature of sliders or clips ll, one of which is seen separately upon a larger scale in Fig. 4, and two or more of which appear in various other figures such as Fig. 1. These clips or clamps IT as illustrated are onepiece elements of U-form having their two legs so spaced as to fit accurately the combined thickness of the two or more main strips. Preferably these clamps or saddles ill have their side faces roughened, see Fig. 4, to assist in manipulating them, and the inner lower edge portions of the legs desirably are beveled as at i9, Figs. 4 and 5, as an aid in setting them onto the strip members.

The manner of operation of the instrument will be clear from an inspection of Figs. 6 to 9, showing several different typical use positions. As is well-known to those familiar with mechanical drawing in its various fields of practical application, the usual drafting equipment for laying out curved lines comprises several different sizes of fixed curves and a few constant radius curves, with occasionally an adjustable curve of some relatively soft material that is bent, a part at a time, to fit a previously plotted curve. The use of these tools is usually slow, and oftenresults in irregular and uneven lines, depending on the compensating skill of the draftsman. The flexible curves of the prior art such as referred to, which are bent and fitted by repeated hand manipulation to conform to the required curve, and which are held in place by weights or otherwise, are unsatisfactory, particularly for curves other than long fiat curves of substantial radius. Where a line is desired which is symmetrical about some axis on the paper the prior devices such as referred to frequently complicate the operations instead of simplify them, and it is dimcult or substantially impossible to duplicate the half of a symmetrical curve accurately. With the instrument of my invention, it will be observed that the device itself serves to plot the desired curve, as contrasted with the localized bending of the previous devices until an approximation of the desired curve is reached by the trial and error method.

In obtaining this result of self-plotting or selfadjustment I avail of the principle that the elas tic failure of a uniform or symmetrical column results in the formation of a smooth symmetrical curve. If the loads imposed are below the elastic limit of the material no damage results to the column, and the removal of the load allows the latter to assume its original position. In the instrument of my invention, elastic failure is obtained by loading the two or more parallel columns or strips in opposition to each other, usually in such way that one element is in compression and the other in tension. The resulting curves depend upon the degree of loading and the nature of the interengaging or anchoring means for the ends of the columns. Where the holding is effected susbtantially at the extreme end of the compressed member, as for example at the left in Fig. 6, the resulting curve has no point of inflection. A similar result is obtained with the form of interengagement illustrated in Fig. 10 in which one of the strips, designated M has its end turned over to provide in effect an end pivot 22 bearing in a similar turned portion or hinge 23 of the other member l3. If then the opposite ends, or portions of strips remote from the interengaged ends are restrained, as by application of holding means such as the sliders H, in the manner as at the right in Fig. 6, one reversal of curvature results at said restrained end. When the other or first ends are similarly restrained, as in Fig. '7, two reversals of curvature result.

Loading such as here referred to may be obtained simply by moving or sliding one or both ends of one column in-board with respect to the end or ends of the other, and securing the members in such position. The two or more strips or columns then function as a unitary instrument and can easily be manipulated and held in place on the drawing board, usually by but one hand of the draftsman.

Fig.- 6 is typical of one family of non-symmetrical curves. To form them, starting from the collapsed position of the instrument as in Fig. 1, one of the slider clips il generally is removed. The two main members or strips l3 and M may then be moved relatively, by drawing or pushing one member through the remaining clip, while holding the other. Having made in this manner an approximate adjustment to the desired curve, a finer adjustment can then readily be made by properly applying a second clip I1 in-board of the first one, as shown in Fig. 6.

A large family of symmetrical curves may be obtained in the manner illustrated in Fig. '7, merely by applying the clips ll, I! at both ends of the curve, which accordingly will have two regions of inflection, one adjacent each restraining point or clip. Other related curves of the same general families may be obtained by bringing the two columns or strips together at an intermediate point, as illustrated for example in Fig. 8. In this particular instance one of the resulting curves, at the right in said figure, is symmetrical, having inflection points at both ends, adjacent the clips, similarly as in Fig. 7; the other curve, at the left in Fig. 8, is non-symmetrical, similarly as in Fig. 6. It will be understood that two or more symmetrical curves may similarly be obtained by applying one or more additional clips in Fig. 8, for example, adjacent the left or pinned ends of the members I3 and M. In connection with each of Figs. 6, '7 and 8 it will be noted that the member which is under tension and which receives the least curvature, namely the strip Hi in said figures, also describes a curve of which use may be made in drafting, the curve in Fig. 6 being non-symmetrical, symmetrical in Fig. '7, and part symmetrical and part non-symmetrical in Fig. 8.

A still different family of relatively long and fiat curves may be obtained in the manner as illustrated in Fig. 9. In this case the strips I3 and M are interengaged at their left ends but With the strip l3 reversed so that the hook turns in toward the other strip l4, oppositely from its position as in Fig. 1 and the others. In this instance the members are oppositely curved, symmetrically with respect to each other, but are individually non-symmetrical.

The dimensions of the columns or strip members l3, M will depend upon the scale of the curves desired. The two members generally are of the same or substantially the same length, but in some cases manipulation of the instrument is facilitated by having one strip somewhat longer than the other, particularly with instruments for the smaller scales of curves. Preferably the strip members, or one of them, are graduated or indexed upon one or both faces as indicated at 20, 2| in Figs. 2 and 3. The graduation unit may be arbitrary or any convenient dimension for example, inch. Such scales or indices are convenient for use in resetting the instrument for the same curve as at some previous time, and in any instance the particular setting may be recorded for future reference, memoranda being made, for example, that the zero point or end of strip B was set opposite point 3 on strip It, or that point 2 of the scale 20 of the strip l3 was set opposite point 5 of the scale 2| of strip 14.

In the modified construction illustrated in Fig. 10, previously described, each of the types of curves may be had as in connection with the form of the previous form, such as illustrated by way of example in Figs. 6, '7, 8, with the exception of the positioning illustrated in Fig. 9. It should be noted that in both forms the two main strip members are bodily separable, those of Fig. being separated by sliding the pin element 22 of strip [3 sidewise out of the hinge 23 of the other member. This allows of either of the strips being used separately as a straight edge, or either of them may be bent back upon itself and clamped in a looped position, producing a new family of curves characterized by a. somewhat greater curvature than those illustrated.

In Figs. 11 and 12 I have illustrated another construction in which the strip members W and I M are pinned or pivoted together flatwise as by means of the rivet 24. Such construction will not give the curves having one relatively steep side, such as illustrated in Fig. 6, but it has the advantage that the two strips may be swung oppositely into open or extended position and their opposite ends bent back and overlapped and secured, in the manner illustrated in Fig. 12, thus producing a total curve approximating or coinciding with a true circle. Similar results may be obtained with the instrument of Figs. 1 to 9 by separating the two elements, extending them into prolongation of each other, overlapping adjacent ends and securing them with a clip l1, and then flexing the opposite ends of the resulting extended strip toward each other into substantially circular or hoop form in which they may be held by clamping together the overlapped end portions. The same is true with the form of Fig. 10. Still other families of curves may be obtained with the instrument of any of the figures by swinging the free ends of the two strips laterally away from each other, while leaving the pinned or interlocked ends in engagement, and carrying the free ends of the two strips entirely around into overlapping relation, in which they may be secured by the clips, with resulting ovate, guttiform, cordate, piriform and other varieties of curves and figures.

As previously pointed out, a relatively inexpensive and easily manufactured instrument may be made with the use of a good grade of steel as the material for the columns or strips, but the invention is not limited as to the particular material employed. While I have shown but two strip members by way of illustration, it will be understood that the instrument in any given case may be composed of a greater plurality of such members, depending upon the elasticity necessary for the particular curve required. The strip members also have been illustrated as of the same thickness and cross sectional shape throughout but in some instances one or more of the strips may be provided with a uniform or symmetrical taper, or one strip may be somewhat thicker or stiifer than the other, again depending on the type of curve to be produced. The U-shaped sliders or clamps illustrated have proved eificient as the holding means, particularly with the smaller sizes of instrument, but it will be understood that if desired I may employ a clamp equipped with a set-screw which may be turned up into securing position when the proper curve has been obtained, or means of the rack and pinion type may be employed in association with the movable holders, to facilitate setting of the instrument.

My invention is not limited to the particular embodiments thereof illustrated and described herein, and I set forth its scope in my following claim.

I claim:

A manual curve-plotting and drafting instrument comprising a pair of similar normally fiat elongated strip members each having a similar thickness of but a small fraction of their width and each being of substantial rigiditycrosswise their flat faces but each similarly elastically flexible in the direction of their length, said strip members having a normal or non-use position wherein they lie fiatwise one against the other in compact closed relation substantially as a unitary ruler-like device, interengaging formations at a corresponding end of each strip member for interconnecting them and limiting longitudinal movement of one member relative to the other at least in one direction at said ends, and one or more clip-like holding elements for adjustably clamping together said strip members at a like number of points spaced from their interengaged ends thereby to hold the strip members in various flexed positions of relative curvature into which they may be manipulated for curve-plotting and drafting purposes.

THOMAS B. KNOX.

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