US3375589A - Drafting instrument - Google Patents

Description

April 1963 G. s. DOLGORYUKOV 3,375,589

DRAFTING INSTRUMENT Filed Dec. 19, 1963 v 2 SheetsSheet 1 IN VENTOR.

gm sbo go'lukq/ April 2, 1968 G. s. DOLGORUKOV 3,375,589

DRAFTING INSTRUMENT Filed Dec. 19, 1963 2 Sheets-Sheet 51 //////////%g! m w United States Patent Ofifice Patented Apr. 2., 1968 3,375,589 DRAFTING INSTRUMENT Gregory S. Dolgorukov, Ferndale, Mich. (407 Fisher Bldg, Detroit, Mich. 48202) Continuation-impart of abandoned application Ser. No. 835,118, Aug. 20, 1959. This application Dec. 19, 1963, Ser. No. 331,800

3 Claims. (Cl. 33104) ABSTRACT OF THE DISCLOSURE The present application discloses a drafting triangle which provides for using the sides formed at the inner opening of the triangle for drawing lines at angles different than those which can be drawn parallel to the outer guiding sides of the triangle, and particularly drawing with the use of a 45 90 triangle lines at and 60 angles. The inner sides parallel to the outer guiding sides are not intended to be used as guiding means and have provided therein finger lift recesses of arcuate cross section forming two sharp edges at the intersection of said recesses with the top and bottom surfaces of the triangle body and therefore disposed at the highest possible distance from the drawing with the triangle of a given thickness.

This invention relates to drafting instruments and more particularly but not exclusively to improved drafting triangles.

The present application is a continuation-in-part of my copending application Ser. No. 835,118, filed Aug. 20, 1959, for Drafting Instruments, now abandoned.

One of the difficulties in the use of drafting triangles results from the necessity of picking up the triangle for the purpose of moving it on the drawing, such as removing it from the ink line and/ or turning it over. The thickness of a drafting triangle being usually from to does not provide a convenient finger hold thereon, and therefore ink lines are often smeared and considerable inconvenience to the user is otherwise caused in attempts to raise the triangle from the drawing.

It has been attempted to solve this problem by providing so-called finger lifts or beveling notches of the segmental shape with three of such notches usually provided k on one surface of the triangle body and two or three on the other. It has been found, however, that such finger lifts are not fully operative for the intended purposes since they recess the body thickness only through very short distance and at their middle portions at that. The user would actually have to have a long nail on his thumb with which to get under the triangle at such short thumb recesses, which is not fully practicable.

It has been attempted to solve this problem by providing so-called continuous finger lifts, or, in effect, beveling L the inner sides of the triangle from both top and bottom surfaces thereof to provide a virtually sharp edge. It has been found, however, that while such expedient operates satisfactorily while the triangle is new, as time goes on and the beveling becomes smooth, such expedient actually properties of the material used rather than to the construcsofter vinyl plastics did not solve the difiiculty of nicking, sincethe edges of such triangles, while not brittle, are so soft that they can be easily nicked with ones nail; since their weak corners easily bend in fall, precision of such triangles is easily destroyed. In their prolonged use the middles of the guiding sides wear and cause formation of valleys therein.

In the search for greater transparency of such triangles and in the mistaken belief that highly polished surfaces are necessary therefor, resulting use of highly polished plastic sheeting made drafting triangles, by reflecting the windows and the overhead lights directly into draftsmens eyes, a source of eye strain cumulating through a period of years in injurious effect on draftsmens eyesight.

One of the objects of the present invention is to provide an improved drafting instrument such as drafting triangle whereby the above difiiculties and disadvantages are overcome and largely eliminated without introducing other problems or appreciably increasing the costs involved. Another object of the invention is to provide an improved drafting triangle which is more convenient to use and particularly is much easier to pick up from the drawin g, and therefore is more efiicient in use. v

A further object of the present invention is to provide an improved drafting triangle which can be used for inking with the possibility of smearing wet inked lines be ing greatly reduced. I A still further object of the present invention is to provide a drafting triangle made of harder plastics and therefore presenting a harder edge but with the tendency of such edges and corners to nick, chip and break off, as observed in conventional triangles, being greatly reduced.

A still further object of the present invention is to provide an improved drafting triangle of the nature specified in the preceding paragraph in which nicking of the edges both caused by hitting hard objects as well as by formation of cracks, due to internal stresses or machining, is greatly reduced.

A still further object of the present invention is to provide an improved 9045 triangle including means provided therein for drawing 30 degree and degree lines inclined in either direction.

A still further object of the present invention is to provide an improved triangle,-the use of which greatly reduced general fatigue and eye strain. 1

Further objects and advantages of this inventionwill be apparent from the following description and appended claims, references being had to the accompanying drawings forming a part of this specification, wherein like reference characters designate corresponding parts in the several views.

FIG. 1 is an elevational view showing an improved 45 ".-45 triangle embodying the-present invention.

FIG. 2 is a fragmentary sectional view taken in the direction of the arrows on the plane passing through the section line 22 of FIG. 1.

FIG. 3 is a fragmentary sectional view taken ,at'the direction of the arrows on the section plane passing through-the line 33 of FIG. '1.

FIG. 4 is an elevational view showinga 30-90-60 drafting triangle embodying the present-invention.

FIG. 5 is a fragmentary view showing on an enlarged scale the portion of the triangle of FIG. 4 encircled by the circle 5.

FIG. 6 is a fragmentary sectional'view taken in the direction of the arrows on the section plane passed through the section line '66 of FIG. 4.

FIG. 7 is a view showing on an enlarged'scale the corners of the triangle of FIG. 4, encircled in FIG. 4 by the circles 7.

FIG. 8 shows an improved 45 -90-,45 triangle with provision therein to draw lines at 30 and 60 to the lines drawn along its guiding sides.

FIG. 9 is a diagrammatic view giving outline of the center aperture of the triangle of FIG. 8 and illustrating the angles formed by the inner guiding sides thereof.

FIG. 10 is a perspective view of one of the triangle corners constructed in accordance with the present 1nvention.

FIG. 11 is a fragmentary view showing the triangle of FIG. 8 provided with finger lifts such as disclosed herein and illustrated in FIG. 2.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways within the scope of the claims. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

In the drawings there are shown, by way of example, drafting triangles embodying the present invention. It is to be understood that the novel features of the constructions illustrated therein are represented graphically in a greatly exaggerated manner in order to permit making geometric constructions illustrating such features. Showing these features of construction to exact proportional scale would make the drawings impracticably large or the novel features of construction so small as not to be legible.

Referring specifically to FIGS. 1-3, the drafting triangle illustrated therein comprises a fiat body generally designated by the numeral 11 and having top and bottom surfaces and outer guiding sides 12, 13, and 14. The sides 12 and 13 form between them an angle of 90, and the third side or hypotenuse 14 makes the angles of 45 with said sides 12 and 13, respectively. The guide sides are of a square cross section, as is best shown in FIG. 2, and are adapted to guide an instrument point, such as that of a pencil or an inking pen.

In the middle portion of the body 11 there is provided a triangular aperture having inner sides 15, .16, and 17, generally parallei to the outer guiding sides of the triangle body. The inner sides 15, 16, and 17 are not guiding sides, but are provided with concave recesses 20, v21, and 22, respectively, to impart to the inner sides a concave cross section such as illustrated in FIG. 2. The recesses are symmetrical with respect to the axis of the cross section in order to provide substantially sharp edges, such as edges 22a and 22]), substantially along the entire lengths of therespective inner sides and both along the top and bottom surfaces of the body. By virtue of such a construction the sharp edges provide a more effective hold for the users thumb, with such sharp edge being disposed twice as high from the drawing surface than is the case with beveling the inner sides from the top and bottom. Wearing out of the triangle affects such edges very little and therefore their effectiveness is preserved for many years.

In accordance with the invention, means are provided eliminating the possibility of origination of cracks and breakage of the triangle at the corners of the inner aperture. It has been found that drafting triangles usually break through their corners even if such corners have square cross sections. Presence of sharp edges such as 22a and 22b in the corner would promote such breakage and could, in effect, defeat advantages of the present invention.

In accordance with the present invention, the corners of the aperture are rounded as illustrated in the drawings. The rounded corners such as illustrated in the drawings may be formed by drilling them with ball or spherical mills with which the recesses are cut. By virtue of such a method, rounding of the cornersand provision of recesses may be made in a single operation, such as by recessing the inner sides with a spherical milling cutter the elevation of which with respect to work is adjusted to have its center on the axis of the body thickness, and thereupon sinking and withdrawing such cutter at each corner.

Of course, these two operations maybe performed in reversed order. Also, the corner holes may be drilled and relieved or chamfered at the edges in separate operations first, and thereupon the aperture may be cut out with square sides and recessed as explained above to provide the continuous concave finger lifts as explained. It is of importance that the sharp edges of the corners are relieved for a small distance, such as .010 as indicated at 25 in FIG. 3. By virtue of such'an expedient, breakage of the triangles at the corners are greatly reduced as compared with conventional triangles.

FIG. 4 shows a 3090-60 triangle in which the continuous finger lifts are formed by cutting them in the inner sides of the triangle body at the aperture to extend further into the sides than do the corners of the aperture as illustrated in FIGS. 4 and 3 wherein such recesses are designated by the numerals 30, 31,.and 32. In this construction the sharp edges of the body at the round corners of the aperture are also removed, as is best illustrated in FIGS. 5 and 6 wherein such relief on the corners is designated by the numerals 33 and 34. Since these corners are not guiding elements the precise depthof the relief is not critical and may be made larger.

The triangle illustrated in FIGS. 1-3 as well as other triangles illustrated and described below are made of hard plastic to provide hard edges and particularly from cast and annealed acrylic sheets, from which such triangles are cut by milling operations. While such material provides for hard guiding sides not susceptible of nicking by nail pressure and rapid wear, causing bowing or caving in wear of the sides by the action the instrument points, the brittleness of such material makes their sharp edgessusceptible to deterioration because of the formation of minute cracks at sharp edges in the process of milling. Such cracks rapidly grow inwardly of the body of the triangle and causing crumbling out of the material when two adjacent cracks meet. In addition, such edges are exceedingly susceptible of nicking even by light impacts on hard objects, such as frames of the drawing boards should the triangle happen to fall down. It is well. appreciated in the art that even a small nick on a triangle guiding side may cause the draftsman to discard the triangle as being a source of faulty work and extreme annoyance.

The sharp edges of the guiding sides along the top and bottom surfaces of the body 11 are cut away as indicated at 18 and 19 in FIG. 2. It is preferred to cut such edges to a uniform depth around the entire triangle for the depth of from .003" to .010", preferably at a 45 angle, thus making the exposed edges of the guiding sides forming the angles of 135 instead of The edges so produced may be polished, if desired. It should be undertood that. the depth of such edge relief on guiding sidesis critical:

and it should not affect squareness of the sides. Generally this relief, in spite of its critically important efiect, isso small as to be invisible by the naked eye and its presence may not be realized by the triangle user.

By virtue of the above described expedientthe sharp edge in which minute cracks have been formedin milling are removed, and a single 90* edge is substituted by two edges, producing a hard andstrong edge thathas extremely long life, makes smearing of ink lines less likely, and provides formore pleasant handling of the triangle. This expedient has a number of further important advantages.

FIG. 8 illustrates at 45-90-45 triangle having outer.

guiding sides 40, 41, and 42 and a central aperture hav-.

ing inner guiding sides 43,44, 45, '46, and 47. It isimportant to appreciate that in this particular triangle all five inner sides of the body at the inner aperture are guiding sides, i.e., are adapted to guide. instrument points. It is also important to appreciate that while in the triangles of FIGS. 1 and 4 the sides of the inner opening are generally parallel to their respective outer guiding sides, in those constructions this relationship is not of a precision nature and such parallelism is sufficient if it satisfies the requirements of appearance. On the other hand in the triangle FIG. 8, the angular relationship of the inner sides with respects to the outer sides is a precision relationship. Particularly, the inner side 43 is parallel to the outer guiding side 40 and perpendicular to the outer guiding side 41. The inner guiding side 44 is parallel to the outer guiding side 41 and is perpendicular to the outer guiding side 40. The inner guiding side 46 is parallel to the outer guiding side 42 and forms angles of 45 with sides 40 and 41. The inner side 47 forms an angle of 60 with the outer guiding sides 41, and a 30 angle with the outer guiding side 40. Also, the sides 45 and 47 make the angles of 105 and 75 with the sides 42 as illustrated. In addition, the guiding sides of the aperture make between themselves angles of 90, 120, and 105 as illustrated in FIG. 9. Thus, the angles most useable in an engineering drawing maybe laid off with the use of the triangle of FIG. 8 without changing to a 30-90-60 triangle or to a protractor. The inner angles of the aperture may be rounded on a radius such as in order to produce a more durable triangle and to enable drawing rounded corners and fillets without the use of a compass.

An important advantage of all of the triangles illustrated herein lies in the provision of outer corners which resist chipping and breaking, an exceedingly objectionable occurrence frequently observed in conventional triangles.

It is important to appreciate that mere rounding such corners is not fully effective to eliminate such condition, and this fact proved very misleading to those skilled in the art. I have found that this results from the fact that triangles seldom fall remaining in a position perpendicular to the floor. In a fall, a triangle usually assumes an inclined position and hits the floor not with the rounded but with the sharp edge of the corner which sharp edge mere rounding of the corners does not eliminate. As a result of such fall, a large scale or piece of the plastic is broken ofif the corner, and the final result is usually the same as that which follows if a triangle hits the floor with a sharp or unrounded corner.

In accordance with the present invention the sharp edges at the rounded triangle corners are removed both at the top and bottom surfaces of the triangle as is best illustrated in FIG. 10, wherein the sharp corner 50 at which the two guiding sides meet is eliminated to provide a rounded surface 51. The sharp edges 52 and 53 formed by such rounding at the top and bottom surfaces of the triangle body are eliminated by angular cuts to provide surfaces such as illustrated at 54. Use of the designating numeral for a similar surface at the bottom of the triangle is avoided in FIG. to prevent confusion of the leader lines.

In accordance with the invention the radius on which rounding of the corners of the triangles are made is inversely proportional to the size of the angle, i.e., the larger is the angle the smaller is the radius on which such rounding is made. Since provision of the surface such as 54 depends in its size on the radius at which the corners are rounded, the same relationship remains with respect to provision of such surface. I prefer to provide such surfaces to approximately one-half of such circle as is best illustrated in FIG. 7, at an angle from to 50. Use of the straight cut is preferable as easily done, but use of curved cuts may be still more advantageous.

As illustrated in said FIG. 7, triangle shown therein has the largest radius at its corner, while the 90 corner has the smallest. Under some conditions, and particularly with smaller triangles, rounding of the 90 corner may be eliminated entirely. The size of the corner radii also depends on the size of the triangle. With the large triangle, such as those of 24" size, such radii are much greater than in the corresponding corners of small triangles. For instance, a 30 corner of a 24" triangle may have a radius of while the same corner of an 8" triangle may have that radius equal to only ,6

Within the last 20 years or so the eye strain in drafting work increased at an alarming rate, producing severe headaches and nervous strain and causing inability of a draftsman to continue with drafting work and retirement several years earlier than before. Such condition prevailed in spite of the fact of presumably better lighting in drafting rooms.

I have found that while the intensity of illumination did increase in general and in drafting rooms in particular, the lighting fixtures became very large, often being continuous from wall to wall of a drafting room and having considerable width. In addition, the windows in drafting rooms have also greatly increased in size. This made it impossible to eliminate reflection of such lighting fixtures, shining directly into draftsmens eyes from the reflecting surface of a drafting triangle, merely by slightly changing the working position as was possible to do with smaller round lights before the advent of the present-day fluorescent lighting fixtures.

Another difiiculty resulting from such a condition is found in the necessity of straining draftsmens vision to distinguish a transparent edge of the drafting triangle, particularly those made of colorless acrylic plastic from the lines on the drawings, particularly in operations such as section lining, in the performance of which the draftsman has to set an almost invisible edge of a drafting triangle from the thinnest line on the drawing. While old celluloid material had amber tint which became darker with age, acrylic plastic, a material of the highest transparency, remains colorless, greatly enhancing the eye strain problem. Attempts have been made to use colo acrylic such as green or pink fluorescent, providing a clearly visible and distinguishable edge on the triangle. It has been observed, however, that such expedient was not only ineffective to relieve the eye strain but in many cases increased it. I have found that this condition resulted from providing a color contrast between the triangle body and the paper, which is also an injurious condition. Some draftsmen having particularly sensitive eyes see a complementary color on the paper when using such color triangles.

In accordance with the present invention, the top surface of the drafting instruments such as triangles is made non-reflecting, such as providing a satin or frosted finish thereon. By virtue of such an expedient, reflections of overhead lights and windows are eliminated, thus relieving severe eye strain on draftsmens eyes.

It should be understood in providing the satin or frosted finish, that in cases of 4590 45 triangles such as shown in FIGS. 1 and 8, it is generally suflicient to provide such finish on one surface only and use the triangle to have its frosted or satin finish surface as the top surface. Such triangles need not be turned over to get all of the angles which may be set with such a triangle. On the other hand with 30-90-60 triangles, such as one shown in FIG. 4, it is necessary to provide the frosted or satin finish on both top and bottom surfaces thereof since it is necessary in use to turn such triangle over.

In addition, in acordance with the invention I eliminate use of the colors in a manner used before and use acrylic material of very light green or yellow color, in effect only faint light color tint, sufiicient only to distinguish the edge of the triangle but not sufiicient to give the color contrast of the objectionable nature. Triangles made of acrylic material of a very light green tint proved to be of greater benefit to draftsmens eyesight and their working efficiency.

It will be understood that the guiding edges of all triangles illustrated herein are constructed as illustrated in FIG. 2 to eliminate the sharp edges and that all of the corners of the triangles may be constructed as illustrated in FIG. 7.

By virtue of the above described constructions the objects of the present invention listed above and numerous additional advantages are attained.

I claim:

1. A drafting triangle comprising a body made oftransparent sheet material and having top and bottom surfaces, with each of said surfaces adapted to lie on straight surface in full surface-to-surface contact therewith, two outer guiding sides forrning between them an angle of 90 degrees, with the third outer guiding side forming 45 degree angles with said two sides, respectively, a single central aperture provided in said body to form five inner point-guiding squared sides, with the three of said inner sides being parallel to the outer guiding sides, respectively, and with the remaining two of said inner sides forming 30 degree and 60 degree angles with each of said two sides, respectively, in either direction, with each of the two inner guiding sides forming the 90 angle therebetween being decreased in their respective lengths by the provision of said two remaining sides by a length smaller than one half of the total length of each said guiding side forming the 90 angle therebetween.

2. The drafting triangle defined in claim 1, with at least 45 degree corners formed by the outer guiding sides being rounded and relieved to remove their sharp edges at both top and bottom surfaces of the body, and all guiding sides being square and angularly chamfered for approximately .003" to .007" to remove the sharp line edges thereof at both top and bottom surfaces of the triangle.

3. The drafting triangle defined in claim 2 with the sides of the triangle at the central aperture thereof which are parallel to the outer guiding sides of said triangle being provided with finger lift recesses of arcuate concaved cross section symmetrical with respect to the thickness of the triangle body to form sharp edges along the inner sides of the central aperture extending inwardly thereof, with the radius of curvature of said recesses being larger than half of the thickness of the triangle body.

References Cited UNITED STATES PATENTS 583,058 5/1897 King 33--112 509,3-35 11/1893 Stowell 33--107. 1,334,145 3/1920 Eaton 33107 X 2,181,081 11/1939 GanaWay 3352 X 2,401,265 5/1946 Nash 33104 2,428,699 10/1947 Elbert et al 33-110 2,512,852 6 1950 Dolgorukov 33.174 l 2,589,525 3/1952 Absher 33-104 2,610,407 9/ 1952 McQuaid 33-104 2,748,474 6/1956 Brown 33--18 X 2,820,294 1/1958 Dolgorukov 33-104 1 3,103,071 9/1963 Dolgorukov 33-112 FOREIGN PATENTS 572,288 2/ 1964 France.

919,388 11/ 1946 France.

606,280 11/ 1934 Germany.

709,790 8/1941 Germany.

139,110 2/ 1920 Great Britain.

581,013 9/1946 Great Britain.

520,237 3/ 1955 Italy.

124,367 2/ 1928 Switzerland.

OTHER REFERENCES Publication: Designers Triangle, copywright 1947, by Dolgorukov Mfg. Co. (Copy Group 430.)

HARRY N. HAROIAN, PrimaryExaminer.

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