US2666261A - Drafting instrument - Google Patents

Description

Patented Jan. 19, 1954 UNITED STATES PATENT oFFIcE" John Arlon Buick, Norfolk, Va. Application August 15, 1951, Serial No. 241,975

'The present invention relates to drafting instruments, and more particularly to an instrument for use on drawing boards and the like for drawing and marking lines at various predetermined angles with respect to a reference edge.

One object is to provide a drafting instrument having a pivoted straight edge provided with an indicator arm which is movable over a protractor scale to indicate the angular position of the pivoted straight edge. Y 1' Another object is to provide a draftinginstrument, includinga tri-square to which is pivoted a straight edge such that the opposite sides of the .tri-square may be used as a reference edge when the device is employed on a drafting board for marking or drawing lines on a drawing.

Another object is to provide a drafting instrument, including a pivoted straight edge having anindicator arm adjacent the pivot point of said straight edge, which is arranged to cooperate with a protractor scale so that both sides of the straight edge will be unobstructed to permit the drawing of lines on both sides thereof.

Another object is to provide a drafting instrument having a combination straight edge which is pivotally attached to one corner of a tri-square,

and is provided'with locking means for holdingv the straight edge arm in a predetermined angular position with respect to the opposite sides or reference edges of the tri-square.

Another object is to provide a drafting instru- 7' ment having a locking element which can be quickly and easily manipulated to lock the combination straight edge arm in a preselected angular position.

'Another object is to provide a guide strip for maintaining the indicator arm in position on the surface of the tri-square which can "be conveniently employed for lifting the instrument with respect to the drawing surface by inserting the fingers thereunder so that in the event'that ink or other drawing fluid is employed, smearing and the like will not occur. 7

Another object is to provide a locking member for maintaining the straight edge arm in a pre selected angular position which includes cooperating threaded fasteners, which may be formed of a resinous plastic composition having an enlarged head portion at one end to overlie a relatively large area of the indicator arm adjacent the pivot point of said straight edge arm, and thereby securely lock the straightedge arm in a predetermined position. I

Other objects and advantages of the invention will become apparent during the course of the 1 Claim." (CI. 33-93) following description of the accompanying drawing wherein:

Figure 1 is a plan view of the drafting instru-' ment showing the straight edge arm in its fully extended position in dotted lines, and its retracted position in full lines. The indicator arm is attached to the straight edge arm adjacent the pivot thereof, and is shown in cooperation with a protractor scale.

Figure 2 is an oblique cross-sectional" view taken on line 2-2 of Figure 1, and looking in the direction of the arrows to illustrate the indicator arm and the combination retainer strip therefor and finger grip.

Figure 3 is an oblique cross-sectional view taken on line 3-3 of Figure 1, and looking in the direc- I tion of the arrows to illustrate the arm locking" threaded fastener unit, and'the-manner in which angular position.

Figure 4 is a fragmentary bottom or rear elevational view, showing the manner in which the straight edge arm is pivo-tally connected to the base or tri-square, and the manner in which one end thereof is beveled to limit movement of the straight edge arm beyond a angular position with respect to one of the reference edges of the base or tri-square, and

Figure 5 is a fragmentary cross-sectional view of a modified form of straight edge arm locking means, including separable threaded fastener elements one of which may be formed of a synthetic resin plastic composition similar to the base and pivoted straight edge.

In the drawing, and more in detail there is shown a base member designated 5 which may be formed of transparent clear synthetic resin plastic or Celluloid, and said base is shaped in the form of a 45 angle tri-square havingrefen. ence edges 6 and 1 extending at an angle of 90. with respect to one anothenand connected at their outer ends by a hypotenuse edge 8. The right angle corner 9 connects the edges 6 and I, while the opposite corners I 0 and H form included 45 angles. The base or tri-square 5 is provided with an opening 12 having straight edges !3 and I4 parallel with the reference edges 1 and 8 respectively and a curved edge l5. The

straight and curved edges I3-M and I5 are con- The triangular base 5 or 45 angl trI square may be placed on a drafting board with either of the opposite reference edges 6 or 1 in registry with a reference line in a conventional manner. Usually, a T-square is employed for this purpose.

Pivotally attached to the corner I of the triangular base is an arm which is pivotally connected by means of a pivot screw 2| to the base 5, and said pivot screw 2| extends through an opening in the corner I l and similarly passes through an opening in the arm 20, so that the threaded end of said pivot screw may receive a correspondingly threaded knurled clamping nut 22. Attached to the underside of the arm 20 is a straight edge arm 23 (Figs. 1 and 4), and said straight edge arm 23 is diagonally cut at the upper and lower portions as at 2* andto form a continuation of the reference edge T and abut the hypotenuse edge 8 respectively. It is intended to form the pivotedstraight edge arm 23 and arm 20 of a synthetic resin plastic or Celluloid composition similar to the base- 5'. such that the draftsman may have clear vision of the drawing on which the instrument is used and other delineations thereon. In the event that the straight edge arm 23 is formed of a synthetic resin plastic composition,- the arm 20 may be joined thereto by a plastic to plastic adhesive, or if desired, the arm 20 ,rnay be integrated with the straight edge arm 23 in the usual manner;

Formed integral with the arm 20 is an indicator arm- 2} which extends at an angle approximately 45 to the pivoted straight edge arm 23-,. and said arm 21 is connected to the arm 20 by an-arcu ate portion 23 (Fig. 1) extending along a radius with the pivot screw 2| as its center; The arcuate edge 28 is adapted to be clampingly engaged by; a locking member, including-a locking screw 29 having an upper threaded end anda head 30 on the opposite end which is countersunk in an opening in the corner H spaced from the pivot screw 2| a distance slightly greater than the radius of the arcuateedge 28. A-locking knurled thumb nut 3| is provided'wit'h an internally" threaded opening for receiving the correspondingly threaded end 29 of the screw 3E), and said knurled thumb nut 31- is provided with a flanged lowerportion 32 adapted to overlie the arcuate edge; 28 so as to frictionally engage the arm 20 adjacent theedge' 2'3 and hold the straight edge arm 23 in a preselected angular position The indicator arm 21 is adapted to cooperate with a protract'o'r' scale 34, and the end of said arin is'prov ided' with a datum line marlied or otherwise applied to the beveled end edge 33 thereof so that it will register with the various degree markings 34 of the protractorscaler The protfactor" scale is marked with legends or'nu- Ineral's 31 which read from zero to 4 5- degrees? aifi'dwith' numerals 38 reading; in a reverse directiorifrom to 90 degrees; Thus; both reference edges 6 and 1' may be used by simply' turning the. instrument about an angleo'f 45.-

Mounted on the triangular base 5 is a retainer strip!!! which has its ends angularly be'n't'asf; at 4| to provide offset'foot portions 42 The offset footportions 42 are riveted or otherwise secured as'at' 43 to the triangular base 5, and is arranged above the free end of the indicator arm 21' so as to maintain said arm in position with the beveled end 36 projecting or presented to the protractor scale 34. When the draftsinan mayinsert his fingersbeneath the retaining strap 49 to facilitate lifting the instrunent-{ism the drawin'giboai'd; whenit'i's desired to? change the pus'iuqrr thereof.

Iii" the modified forn'i (armament-ita drawing angular lines,

4 in Figure 5, a separable threaded fastener element is shown which can be substituted for the locking and pivot screws illustrated in the form of the invention shown in Figures 1 to 4 inclusive. In the event that the pivot screw 2| and retaining nut 22 is replaced, the separable threaded fastener shown in Figure 5 may be used both as a pivot screw and locking means. In Fig. 5 the base 51; is the same as before, and includes a triangular base similar to that shown in Fig. 1. The arm 20a is adapted to be pivotally connected to the base 5a by means of a tubular fastener element 50a having a head 5|a which is received in theren larged portion of an opening 52a in the base 5a. The fastener element 50a is provided with an internally threaded bore 53a and said fastener is adapted to extend through an opening 541: in the arm 20a such that it projects therebeyohd a slight distance. The tubular threaded fastener 50a may be formed of a syntheticresinplasticcomposition similar to v the base 5a; The tubular threaded fastener 509i is adapted to receive the externally threaded portion 55a of a retaining screw having an enlarged head portion 56 and a downwardly directed rim portion 51a spaced from the externally threaded portion 55a by an annular channel 53d. Thus, the arm 20a maybe frictionally and clampingly'f secured to the" base 5a by turning the knurled peripheral portion (not shown) (5r meningestion 51a in a direction to thread the externally threaded portion 55a; in the internally threaded portion 53a of the cooperating tubular fastener 50a.

If the locking fasftenerfshown in Figure his employed in lieu of the locking screw and nu-t 29-3| shown in Figs. 1 to 44 inclusive, the downwardly directed rim portion 51a will engagethe arm 20a and overlie the areuate' edge" thereof to lock the arm in a pre-selected position when the head 56a is turned in a right directioni The cooperating fastener element 560/ shown mm; 5, may likewise be formed of a" synthetic resin plastic of a color '11 contrast to the base" and pivoted straight edge arm as well as the indicator arm;

It" will thus be' Senjthat the straight edge arm 23in Figs. 1 to 4 hasits o pcsedeu es in parallel relation one with the other, and with the hypotenuse edge 8 when the instrument is in its retracted position. When in this position, 45 degree lines may be drawn insubstantially the same manner as a tri-square is employed-by placing the reference edges reference line or surface on the drawing board.

When it is desired to draw lines from zero td 45 degrees; the" reference edge 1 is placed against a horizontal or longitudinal reference surface'i Similarly, by

ii against horizontal reference surface, angles froiri 45 to degrees may bed'rawn". Obviously, the'-triangularbase 5 or tri-s'duare can beplaced m otherpositions so that the straight edge arm 23 can be adjusted to various predetermined angular positions and held therein by the looking fastener elements 29-3|' shown" in Figs. 1 to -inclusi've, and Eta-55d shown in Fig. 5i-

It is to be understood, that the forms of the invention herewith shown and described areto be takenas preferred embodiments thereof, and that various changes in the shape, size and arrangement of parts may be resorted" to without departing from the s pirit ofthe invention or the scope of the subjoined claim.

In a drafting instrument, a trianguier" base 6 and I against a placing the reference edge-- straight edge arm having one end pivotally con-' nected to a corner of said triangular base at a point in the angle between the hypotenuse and base and near the intersection thereof, an indicator arm integrally connected to said straight edge arm adjacent the pivoted end thereof and projecting over the base to cooperate with a protractor scale thereon, a guide' strap having its ends afiixed to said triangular base adjacent the ends of said scale to guide said indicator arm in close proximity to the graduations of said scale, an arcuate portion connecting said straight edge arm and said indicator arm, the rim of the are extending along a radius having the common pivot of the straight edge arm and the indicator arm as its center, said arcuate rim lying in close proximity to said center, and a threaded fastener for ill holding said straight edge and indicator arms 20 in a position of angular adjustment, said threaded fastener being arranged on the base between said arms with a rim of the fastener overlying and frictionally engaging said arcuate rim.

JOHN ARLON BUICK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,365,779 Grave June 18, 1921 1,755,152 Parker Apr. 15, 1930 2,104,354 Rich Jan. 4, 1938 2,154,753 Kallio Apr. 18, 1939 FOREIGN PATENTS Number Country Date 2,813 Great Britain Feb. 5, 1907 355,856 Great Britain Sept. 3, 1931 548,282 Great Britain Oct. 1, 1942

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