US2043759A - Bicycle frame - Google Patents

Description

June 9, 1936. G. s. LEWIS BICYCLE FRAME Filed Aug 9, 1934 Patented June 9, 1936 UNITED STATES BICYCLE FRAME George S. Lewis, Evanston, Ill., assignor to Battery Patents Corporation, Chicago, 111., a corporation of Illinois Application August 9,

6 Claims.

This invention relates to a bicycle frame and more particularly to a frame for a girls bicycle.

An object of the invention is to provide a novel brace-frame construction which is' simple but which greatly increases the strength of the frame without adding any substantial weight or bulk.

A further object is to provide a lightweight frame consisting of castings and tubes secured together without welding and without bolts, screws and other like devices. Other specific objects and advantages will appear as the specification proceeds.

The invention is illustrated in a preferred embodiment, by the accompanying drawing, in which Fig. l is a side View in elevation of a frame embodying my invention; and Fig. 2, a broken plan view of the same.

In the illustration given, A designates a head casting; B, a cluster casting; C, a hanger casting; and D, a brace-casting. V

The head casting A is preferably formed of a light metal such as duralumin or other light and sturdy aluminum alloy. Preferably, the casting is designed to provide a streamline structure providing at its front a tubular part I 0 adapted to receive the steering shaft and with a rearwardly extending tube ll bifurcated at i2. Also, the casting is provided with a tube It which is bifurcated at I4.

The cluster casting B is provided with a main body portion 15 providing therethrough a central bore adapted to receive the vertical tube IS. The cluster casting B is preferably formed of the same material used in casting A and is provided at its rear side with an integral rearwardly extending fork portion ll bifurcated at l8.

The hanger casting C is provided with a central horizontal aperture receiving the bearing IQ for the crank. The casting is provided with a tubular extension 2! directed toward the head casting A and with a tubular extension 2! receiving the lower end of tube It. integrally formed with casting C is a rearwardly projecting extension 22 which is bifurcated at 23. Each of the forks of the bifurcated portion of casting C is provided with heads 2Q as in the usual bicycle frame construction.

In the manufacture of bicycle frames for girls bicycles, where the top bar or tube is eliminated, I have found that severe strain has been placed upon the vertical tube connecting the cluster casting to the hanger casting, and also upon the upper tube extending from the head casting.

1934, Serial No. 739,158

After some use, there is a tendency for the vertical tube to bend under the strain. In most cases where the frame has broken down, I have discovered that the yielding occurred in the vertical tube or in the connection leading from the head casting to the vertical tube. In order to overcome such defects, without, at the same time, adding to the weight of the structure in any substantial degree, I have provided a bracecasting D which is provided centrally with a tubular collar portion 25 receiving tube It and with a downwardly turned brace-arm 26 bifurcated so as to provide flanges 21 straddling the top portion of the extension 22. A pin 28 may be passed through the flanges 21 and the extension 22 to hold the arm 26 against rattling, etc. At its forward side, the casting D is provided with a curved extension 29 bifurcated at 3B and receiving the end of tube 3!. The tube 3| is received at its other end within the tubular socket H of head casting A.

A tube 32 connects the tubular extension l3 of casting A with the tubular extension 20 of casting C.

With the construction shown, it that casting D is curved upwardly at its forward end so as to receive straight tube 3|. The casting is then curved almost to a horizontal plane so that the collar 25 is in complete alignment with the tube It. sharply downwardly to rest upon the extension 22 of casting C, the collar 25 of casting D centering the brace-arm 26 so that it remains always in true alignment with casting C.

As stated above, I prefer to form the castings of aluminum alloy, such as, for example, duralumin. Preferably, the tubes are also formed of this material, although other suitable metals may be used. The use of aluminum or aluminum alloys has been considered impractical heretofore for this purpose owing to the comparatively low tensile strength of aluminum or aluminum alloys. To gain the proper strength, castings of other metals would be too heavy and unwieldly. Aluminum alloys, such as duralumin can be heat-treated to give them a tensile strength comparable to steel, with the weight only one-third of a similar casting of steel. Should, however, the casting after being heat treated be subjected to a welding or brazing heat, the benefit from the heat treating would be lost and the casting would be no stronger than ordinary commercial aluminum. It is apparent, therefore, that to preserve the strength of the heat treated alloy, no fusing temperature may be will be noted The brace 26 is then curved used. I have found that a temperature of 300 F. may be maintained for a limited time without danger or for a brief period, it is possible to go as high as 350 F.

I have found that a satisfactory aluminum alloy frame can be produced through the use of aluminum castings to which tubing is joined by shrinking the castings upon the tubing. For example, one of the castings, say casting A, is heated, preferably in a liquid bath, to a temperature of around 300 F. so that the tubular extensions II and I3 expand sufficiently to receive connecting tubes that are normally too large to be received within the tubular extensions. I have found that a satisfactory joint can be made by having the tubes from 1 1000th t 1000ths larger than the bore of the tubular extensions.

By the above method, I have connected the head casting A to the tubes 3! and 32, the cluster casting B to the tube iii, the hanger casting C to the tubes l6 and 32, and the brace-casting D to the lower end of tube 35.

An extremely sturdy connection may be formed through the expansion of the casting by heat and the subsequent contraction thereof about a tube which is several thousandths greater in diameter than the diameter of the bore in the casting. Additional strength for the connection can be obtained by chilling the tube while at the same time heating the casting. When the chilled tube is placed within the expanded bore of the casting, a substantial shrinking of the bore and expansion of the tube occurs which produces a very tight fit.

In order to facilitate securing an effective shrunk fit, an aluminum alloy having a high lineal coefiicient of thermal expansion is used. Duralumin, for example, has a coefficient about two and one-half times that of ordinary cast iron, and slightly more than double that of steel. To secure a strong connection if iron were used for the castings in a bicycle frame, it would be necessary to hold the internal diameter of the opening in the casting and the external diameter of the tube within limits of less than a thousandth of an inch, limits not economically practicable in bicycle manufacture. The alloy used, on the other hand, permits manufacturing limits several times those possible with cast iron, due to its higher coefficient of expansion, and has a tensile strength, when properly treated, comparable to that of steel.

The resultant frame is light in weight, devoid of objectionable welding marks, screw and bolt connections, and is sturdy and substantially integral in construction.

While I have described the castings as being secured to the tubes by shrinking the castings thereon, it will be understood that, if desired, the tubes may be expanded within the castings or both methods may be used simultaneously; and in using the words shrunk fit in the appended claims, I intend to cover either or both methods. It will also be understood that my invention may be employed by forcing one of the tubes within the tubular extensions of a casting. Such a force fit may be supplemented by passing pins or other connecting means through the telescoping parts.

With respect to the brace-casting D, and its connections with the frame, I have found that this construction is not only desirable with an aluminum alloy frame, but also very satisfactory with steel frames or frames of other metals, and I do not desire to be limited in the appended claims to aluminum metal alloys.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible, in View of the prior art.

I claim:

7 1. In a bicycle frame of the character set forth, a head member, a hanger member equipped with a rear extension, a cluster member, a tube connecting the cluster and hanger members, and a tube extending downwardly from the top portion of the head member and resting on said hanger member extension, said last-mentioned tube being equipped with a transverse collar receiving said first-mentioned tube.

2. In a bicycle frame of the character set forth, a head member, a hanger member equipped with a rear extension, a cluster member, a tube connecting the cluster and hanger members, a brace-member equipped with a collar receiving said first-mentioned tube and with a brace-arm resting on said hanger member extension, said brace member being also provided with a forward tubular extension, a tube connecting said tubular extension with the top portion of said head member, and a second tube connecting said head and said hanger members.

3. In a bicycle frame of the character set forth, a head casting, a hanger casting equipped with a rear extension, a cluster casting, a tube connecting the cluster and hanger castings, and a tube extending downwardly from the top portion of said head casting and resting on said hanger casting extension, said last mentioned tube being equipped with a transverse collar receiving said first mentioned tube.

4. In a bicycle frame of the character set forth, a head casting, a hanger casting, a cluster casting, a tube connecting the cluster and hanger castings, a brace-casting provided with a transverse opening receiving said tube and having a downwardly curved brace resting on said hanger casting, and a tube connecting said brace-casting to a top portion of said head casting.

5. In a bicycle frame of the character set forth, a head casting, a cluster casting, a hanger casting equipped with a rear extension, a tube connecting the cluster and hanger castings, a curved brace-casting having a substantially horizontal central portion provided with a transverse collar receiving said tube and having also a downwardly extending brace arm resting on said hanger casting extension, and a tube connecting said brace-casting to the top portion of said head casting.

6. In a bicycle frame of the character set forth, a head casting, a hanger casting, and a cluster casting, said hanger casting being provided with a rear extension, a tube connecting the cluster and hanger castings, a substantially S-shaped brace-casting provided with a transverse opening receiving said tube, the lower end portion of said brace-casting resting on said hanger casting extension, and a straight tube connecting the forward end of said brace-casting with said head casting.

GEORGE S. LEWIS.

Images