US3435528A - Drafting styli and material therefor - Google Patents

Description

April 1, 1969 H. w. FERCHLAND ETA L 3,435,528 DRAFTING STYLI AND MATERIAL THEREFOR- Filed Dec. 6, 1966 DRAFTING A? MACHINE #L fig? ! l I I I I I 1 .1 E y W y W W Ff INVENTORS Ware/a llfizrJ/azzd flqyzzsi/ke JZh/hcqJ: w

ATTORNEY United States Patent 0.

DRAFTING STYLI AND MATERIAL THEREFOR Harold W. Ferchland, Troy, and Augustine J. Wallace,

Jr., Southfield, Mich, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Dec. 6, 1966, Ser. No. 599,470 Int. Cl. B431: 1/00 US. CI. 33-18 2 Claims ABSTRACT OF THE DISCLOSURE A drafting stylus in the form of a thin pointed rod is composed of a tin-nickel alloy in the ratio of approximately 65% tin and 35% nickel.

This invention relates to drafting styli and the composition thereof. In the automotive and aircraft industries it is necessary to produce very accurate drawings, for example, of body parts which may be directly scaled or gauged to make dies and templates. It has become customary to make these drawings upon a very stable material comprising a metal plate covered with seven layers of white paint. The drawings ordinarily have been executed by draftsmen using a gold alloy stylus sharpened to a paddle shaped point which will indent the paint to a prescribed depth, usually .003 inch, without cutting or scoring the paint and which will simultaneously make a black line. These gold alloy styli however, erode so rapidly that very frequent redressing of the point is necessary and in addition, when the line to be drawn changes direction as at a corner or a curve, the stylus must be manually indexed so that the long dimension of the stylus point will be in the direction of the stylus movement.

With the advent of drafting machines, the gold alloy styli became impractical and a demand arose for a stylus which would require less frequent redressing and which would execute arcs of any radius or sharp corners without indexing. Other requirements were that the line left by the stylus must be erasable yet must be resistant to an ammonia solution since the drawings have to be cleaned by washing with an ammonia solution. Further, because the drawings have to be reproduced photographically, the lines produced on the plate must be indented in the paint to help achieve proper lighting of the lines.

It is an object of this invention, therefore, to provide a material for a drafting stylus meeting all of the above requirements.

Another object of the invention is to provide a drafting stylus having a configuration and strength suitable for meeting the above requirements.

The invention is carried out by providing an alloy which when used in a drafting stylus will produce an erasable black mark resistant to an ammonia solution. The alloy also has the characteristics to minimize the redressing requirements of the stylus.

The invention is further carried out by providing a stylus of a tin-nickel alloy having a specific type of conical point.

The above and other advantages of the invention will become more apparent from the following specification taken in conjunction with the drawings in which;

FIGURE 1 is a schematic view of a drafting machine having a stylus, and;

FIGURE 2 is a side view of a drafting stylus according to the invention.

As represented in FIGURE 1 an automatic drafting machine includes a stylus holder 12 for maneuvering and controlling a stylus 14.

It has been found that a suitable stylus for drafting machines of the type described above is a thin rod 14,

Patented Apr. 1, 1969 as best shown in FIGURE 2, formed with a conical point 16 wherein the included angle of the point is 60 to 90 and has a small radius on the tip 18. The material of the stylus is a tin-nickel alloy.

The preferred composition of the stylus material is 65% tin and nickel. It has been found that this c0mposition is rather critical in that if the nickel content is made much higher the stylus becomes brittle and will tend to break. On the other hand, if the tin content is made higher, the alloy will be too soft so that an excessive wear rate results which requires too frequent redressing. However, acceptable results can be obtained when the tin-nickel alloy contains a proportion of tin in the range of 62% to 68%.

The stylus may be fabricated by casting or rolling metals of the prescribed composition. However, the preferred method of fabrication is electro-plating where the alloy is deposited in a rod shape onto a conductive steel wire 20 from a plating solution having the following composition: 49 g./l. SnCl 300 g./l. NiCl -6H O, 56 g./l. NH HF and, NH OH to raise pH to 2.0. The plating operation conditions are the same as those given in Modern Electra-plating, second edition, by F. A. Lowenheim, 1963, p. 500.

Typical dimensions for a drafting stylus made by this method are a rod diameter of 0.072 inch and total length of 1.5 inches. The steel wire 20 upon which the tin-nickel alloy is deposited is 0.032 inch in diameter and extends approximately one inch from the blunt end of the stylus. The cone-shaped point '16 of the stylus includes a 60 angle and the extreme tip 18 has a radius of 0.005 inch.

It has been found in practice that the stylus of this invention successfully meets the rigorous requirements set forth above. The device has sufficient structural strength to indent three layers of paint on the drafting medium as is desired and leaves a fine uniform black line which is erasable and yet is resistant to a cleaning solution of one part ammonia to five parts water. The angle of the point produces an indentation in the paint which enables superior photographic reproductions of the drawing to be made. It has also been found that the stylus has a much greater wear resistance than the previous gold alloy.

While the preferred embodiment of the invention is disclosed herein the scope of the invention is not limited thereto.

It is claimed:

1. A drafting stylus comprising a thin rod terminating in a conical point defining an included angle in the range of 60 to 90, the rod being composed of a material capable of producing an erasable black line resistant to removal by an ammonia solution, the material comprising a tinnickel alloy containing tin in the range of 62% to 68%.

2. A drafting stylus for a mechanical drafting machine comprising a thin rod terminating in a conical point defining an included angle in the range of to 90, the

stylus point being composed of a material capable of producing an erasable black line resistant to removal by an ammonia solution comprising an alloy of tin and 35% nickel.

References Cited UNITED STATES PATENTS 2,557,148 6/1951 Schimmel. 5 3,129,512 4/1964 Schiler.

3,192,630 7/1965 Dineson 33-138 X OTHER REFERENCES Publication: Metallurgia, Developments in the Met- 70 allurgy of Tin and its Alloys, December 153, pp. 277-281.

HARRY N. HAROIAN, Primary Examiner.

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