US2357553A

US2357553A - Handle-bar stem

Info

Publication number: US2357553A
Application number: US370634A
Authority: US
Inventors: Frank W Schwinn
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-12-18
Filing date: 1940-12-18
Publication date: 1944-09-05
Anticipated expiration: 1961-09-05

Description

Patented Sept. 5, 1944 UNIT-'ED STAT E S PATEN T OFFICE HANDLE-BAR VSTEM Frank W. Schwinn, Chicago, Ill.

Application December 18, 1940, Serial No. 370,634

.2 Claims. (Cl. 287-54) The present invention relates to a handlebar stem for bicycles and is particularly'conce'rned with the development of an improved handlebar stern and a simplified and improved method of making such stem.

In the manufacture of bicycles it has been customary to forge the -blanks for the handlebar stems to a formapproximating-thei-r final shape. rIhis shape included a straight cylindrical lower portion, and an angularly disposed upper portion. This bar was subsequently formed, by suitable grinding, drilling and slotting operations, into a handlebar clamp.

The finished handlebar stems are highly polished and plated, and, in the prior construction of such stems, the machining, polishing and plating v operations performed thereon, were necessarily numerous and difcult, and were not adapted vto low price, large quantity lproduction methods on standard types of machines.

The forging of the blanks approximately to the shape of the finished stem required a large number of forging operations with the result that the blanks were frequently pitted, so that it wasnecessary to form the blanks with a relatively large excess amount of material which subsequently was removed by machining.

' It is difficult to discover hidden' flaws and Yweaknesses in a forging thus formed, and since the breaking of a handlebar stem in'use is apt to have serious consequences, increased assurance of freedom from such hidden imperfections is of extreme importance.

An object of the present invention is to simf plify 4and improve the manufacture of bicycle handlebar stems.

Another. object is to develop an improved handlebar stem from a simple blank with a minimum number of operations and maximum characters of reference indicate similar partsthroughout the several views.

Referring to the drawing, of which there is onesheet,

Figure 1 is a view'v in perspective of aforged blank for -a handlebar stem made accordi-ng .to-

the present invention, the flash from a forging operation having been removed therefrom;

Figure 2 is a View in side elevation of the blank shown in Figure 1, after machining, an end po-rtion thereof being lbroken away to show a longitudinal sectional View through the center of -a hole therein;

Figure 3 is a View in perspective of the machined blank illustrated in Figure 2 after forming to final shape;

Figure 4 is a plan View of the formed, machined blank shown in Figure 3 with a bolt hole drilled therethrough; and

Figure 5 Yis a vertical longitudinal sectional View through a completed stem having its asso- Vciatred parts assembled therewith.

In Figure 1 of the drawing, the numeral -II indicates generally a forged blank made according to vthe invention a'fter the trimming of vthe ash, not shown, which projects laterally from substantially the horizontal median plane -of the leted vand of cylindrical section with a radius o-f curvature approximately equal to that of a handlebar I 6, such as is shown in Figure 5. Each of the fillets which comprise the curved ends of the depression I5, has a circumferential length equal to approximately one-fourth of the circumference of the handlebar I6 with which the vstern is to be used, while the length 4of the intermediate flat portion is equal in length to slightly less than one-half of the circumference of such handlebar vwhen bent to finished form.

The plane of the bottom of the depression I5 is tangent to the curve of each of the ends of vthe depression so vthat when the head I4 of the stem is formed by bending to the shape illustrated in Figure 5, it will conform to the shape of the handlebar I6.

The head I4 has two holes I'I and I8 therein one in each of the thicker end portions of said head, said holes preferably being punched while c the piece is hot as a part or continuation of the The hole I'I is formed with-a' forging process. pair vof laterally extending kerf-like recesses I9, as shown in Figures 3 and 4, toreceive locking shape.

, mately 90 degrees.

fins 20 on a bolt 2| used to clamp the handlebar I6 in the finished stem as shown in Figure 5.

It has been customary in the manufacture of handlebar stems, initially to forge an oversize blank substantially to form, and then to grind the piece to size. The ground blank was drilled and slotted to provide the handlebar clamp, and the piece was then polished in three successive polishing operations, each of which was performed with a nner grained polishing medium than the preceding one, so that each polishing operation removed the line scratches left by the preceding operation. Y

In making a handlebar stem according to the present invention, it is preferred to perform the grinding operations and the first two of such polishing operations while the piece is straight, as shown in Figures l and 2'. The cylindrical stern I2, and tapered neck portion I3, being of round section, are well adapted to rapid, inex- 'I pensive machine grinding and polishing on .ishing operations, as above set forth, the reduced thickness, recessed portion I of the head I 4 is bent beyond the elastic limits of the material thereof around a mandrel, not shown, of approximately the samel diameter as the vhandlebar I6 to form a handlebar clamping eye. As a result,

.the fibers of the material in the reduced thickness portion I5 are so stretched and re-alined in the outer peripheral part of the clamping eye and compressed in the inner peripheral part of the eye that it will not spring back to the straight form but permanently retains the curved eye The portion of the head I4 having the recess I5 therein, is of a length so proportioned to the circumference of the handlebar I6 as to leave a space 22 separating the head portions having the holes II and I8 therein, as illustrated in Figures 3 and 5, thus permitting the head portions to be drawn together by the bolt 2l for tightening the clamp thoroughly to the embraced portion of the handlebar.

The tapered neck portion I3 is bent laterally toward the side of the blank having the recess I5 therein, the bend in the present illustrated construction being through an angle of approxi- Both of the above mentioned bending operations are preferably performed While the piece is cold. If the blank is free from defects or hidden weaknesses, such cold bending will not affect its strength, but if a serious defect or hidden weakness exists, the piece will fail or will tend to kink at the point of flaw and maybe scrapped. The bending of the piece to shape thus acts to test the blank for flaws.

A hole 23 is drilled lengthwise through the cylindrical portion I2 of the bolt, being continued in a straight line upwardly and through a side of the neck portion I3 as shown in Figures 4 and 5. The lower portion 24 of the hole 23 is counterbored to permit a slight lateral'movement of a stem bolt 25, and the upper end of the hole 23 is also enlarged as at 26 and is machined to provide a flat face 2'I as by means of an end mill, not shown.

The stem bolt 25 is provided with an enlarged cylindrical head portion 28 adapted to rest on the face 2'I and to extend upwardly beyond the counterbored portion 26. The upper portion of the head 28 of the bolt 25 is of hexagonal shape as at 29 to permit turning the bolt with a wrench.

The lower end of the stem I2 is cut off at an angle acute to its axis as at 30 to provide a cam face to cooperate with a similarly disposed cam face 3| on a conventional wedge member 32.

The wedge member 32, which is preferably an aluminum die casting, is of cylindrical shape, of approximately the same diameter as the portion I2 of the stem, and is made with an internally threaded bore 33 to receive the bolt 25 in a conventional manner.

The present structure is cheaper and easier to manufacture than the conventional type of handlebar stem for a number of reasons, as well as being less apt to have hidden flaws or defects which might result in failure of the stem while in use.

A considerable saving in material is accomplished because of the practicability of forging closer to finished dimensions as above set forth, which in turn has the desirable result of requiring the removal of less material to attain the nished dimensions. The handlebar bolt holes may be punched instead of being drilled as in the prior construction, while the drilling of a hole and the milling of a slot for the handlebar clamp are eliminated and replaced by a simple bending operation.

These advantages are of course in addition to the important advantages which include the simplication of the grinding and polishing operations achieved by my invention, and the cold forming to shape which discloses any dangerous hidden aws or Weaknesses in the forging.

While the description of the illustrative embodiment of the invention has been based on the making of the blank by forging, it will be apparentA to those versed in the art that the blank can be made by other methods, such as by the machining of a blank bar or billet of bendable metal such as steel, and cutting or formingr such piece of metal'to the form of the nished blank, such as that illustrated in Figure l, by means of suitable machining operations.

The forming of the machined or partly machined blank to shape by the bending of the upper portion of the stem to offset the clamp from its original position of alignment with the lower or main portion of the stem, produces a structural change in the metal of the stem itself which constitutes a slight stretching of the metal on the outer side of the bend, and a tendency toward the compression of the metal on the inside of the bend. The set-up of these stresses causes a rupture or deformation of the blank at the areas of bend incase of a rejectionable naw in the piece.

The grinding and preliminary polishing operations above referred to, which are performed upon the piece while in the original or straight form, are preferably performed while the piece is being rotated, `and AWhen so performed, the finish producd upon the blank is substantially uniformv throughout the entire area of circular cross section. This characteristic produces a uniform polish on the entire area after the piece is bent to nal shape, as illustrated in Figure 4,

and greatly facilitates the final polishing operation prior to plating.

While I have illustrated a preferred embodiment of my invention, many modications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth,

but desire to avail myself of al1 changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. A handlebar stem comprising a body of originally straight bar stock, but in the nished form having a substantially gooseneck shape, including a straight cylindrical lower portion adapted to lit within the fork stem of a bicycle, a head return bent and internally dimensioned to embrace a handlebar, the end portions of the head being in opposed spaced relation, means for drawing the opposed portions of the head together to effect tight frictional engagement between the head and the handlebar, an integral intermediate portion extending as a continuation of the upper end of the lower portion and of one of the end portions of the head, angularly to the axis of said lower portion, and laterally spacing the head therefrom, and means for securing the stem in the fork stem of the bicycle including a stem bolt extending axially through said lower portion and having its head accessible to a wrench at the upper end of said lower portion.

2. A handlebar of substantially gooseneck shape comprising a substantially straight lower portion adapted to t within the fork stem of a bicycle, a head which is return bent and internally conformed and dimensioned to embrace a handlebar, aligned apertures in said superposed spaced ends of the head', a bolt occupying said apertures whereby said ends may be drawn together to effect tight frictional engagement between the head and a handlebar embraced thereby, a curved intermediate portion integral with the straight lower portion and one of the ends of the head and serving laterally to space the head from said straight lower portion, and means for securing they stem in the fork stem of a bicycle, said last-mentionedv means including a stem bolt extending axially through said straight lower portion and having its head accessible ,to a wrench at the upper end of said lower portion.

FRANK w. SCHWINN.