US1710526A - Article of manufacture and method of making the same - Google Patents

Description

April 23, 1929. w. P. WITHEROW AR TICLE OF MANUFACTURE AND METHOD OF MAKING THE SAME Filed Feb. 14, 1925 V .tent that the tooth mayeasilybe broken off.

Patented Apr. 23, 1929.

UNITED STATES PATENT "OFFICE.

WILLIAM P. WITHEROW, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO COLONIAL TRUST COMPANY, TRUSTEE, OF PITTSBURGH. IENN- v SYLVANI A, A CORPORATION OF PENNSYLVANIA.

ARTICLE OF MANUFACTURE AND METHOD OF MAKING THE SAME.

Application filed February The-present invention relates broadly to the art of metal Working, and more particularly to the art as applicable to the production of articles required to have a hard, uniformnvearing surface, such as gears, cams, shafts and the like, although the utility of the invention is not limited in this respect.

I At the present time it is customary to produce articles of the general character herein contemplated by providing a blank having an amount of metal sufficient to form the desired article. This blank is then either upset to effect apreliminary distortion of-its m ass such as to facilitate subsequent operations, or it is drawn down under a-hammer for the same purpose. Thereafter, the article is produced from the roughly shaped blank by suitable machining operations. The machined article is then treated, as by case hardening, to give the desired hardness and wearing qualities.

- Actual tests, such as the so-called hardness test, are then relied upon to determine whether these hardened articles will pass inspec tion. It frequently happens that the tests show non-uniformity as to hardness in different parts of the same article, the variations being such that quite often the article haslto be rejected. This is particularly true in the case of gears, when one tooth, or certain teeth, are so soft as to render the whole gear unfit for satisfactory service.

It also frequently happens that the case hardening penetrates unequally at different portions of a tooth. In the event'of execssi-ve penetration on opposite sides of a tooth, the interior tooth structure relied .upon for carrying the load is weakened to such an ex- It is apparent, therefore, that uniform hardness of a tooth particularly,- is extremely desirable.

Ihave-found that this non-uniformity isv to a large'extent, at least, attributable to the original shaping' ope'rations on the blank. In the case either of upsettin'g or hammer shaping, the original fiberarrangement is irregularly and non-uniformly distorted. This results in the production of an article having no predetermined or uniform fiber disposition. Incase hardening, the. degree of hardness varies directly as the disposition of fiber 14, 1925. Serial No. 9,140.; i

v to reduce to a minimum variations in hardness in different parts of the same-article or in successive articles.

r In the accompanying drawings there is shown for. purposes of illustration only, a preferred embodmient of the present invention, it being understood that. the drawings do not define the limitsof my invention, as changes in the construction and operation therein disclosed may be made without departing either from the spirit of the invention or the scope of my broader claims. It' will be'further understood that the invention is not limited to the sequence of steps hereinafter set out. v I In the drawings: f

Figure 1 is a side elevation of a die rolled blank particularly adapted for the productionof a pinion shaft and gear, the general outline of the fi nished shaft and gear being v indicated in dotted lines;

Figure .2 is a longitudinal sectional view case of blanks having a substantiallycircular cross section throughout the major portion ,of their lengths, I preferablyutilize a leader having a major anda minor axis. In the illustrated embodiment of my invention,- the leaderis subjected to a die rolling operation in a pair of rolls having matrix portions adapted to form successive pairs of blanks attached in end to end relationship. After the die rolling operation the blanks may beseparated in any desired manner to provide pairs as illustrated in the drawings.

Each blank preferably comprises a shaft 1 forming portion'2, having a length and diameter suitable for the formation of the finished shaft, and'an enlarged head 3 having dimensions suitable for the production of a gear.

In actual practice the matrix portions of the from. end to end of the blanks.

grooves are preferably so shaped that alter nate blanks extend in opposite directions. By such an arrangement, the heads 3 of comparatively large diameter occupy adjacent relationship, thereby facilitating the work of the rolls and tending to eliminate abrupt changes of section such as would be necessary if successive blanks extended in the-same direction. The action of the rolls on the leader is such as not to objectionably or non-unifor'mly destroy the longitudinal arrangement or disposition of the fibers; By actual tests it has been found that the fibers tend to fol- .low the general contour of the blanks, extending continuously and substantially uniformly This uniformity is highly desirable as will hereinafter be more fully pointed out.

After the blanks have been separated into pairs 'or units in any desired manner, they may be subjected to suitable finishing operations, either in pairs or by units, to reduce the same to-the desired dimensions. veniently, this may be accomplished by subjecting the blanks in pairs to suitable finishing or machining operations in' a lathe or other form of apparatus. .After the blanks have been reduced to finished dimensions, the teeth may be formed thereon in any desired manner. It will be apparent, however, that the machining or finishing operations will i not have any effect upon the fiber disposition,

so that the uniformity in the arrangement or disposition of the fiberswill be maintained in the finished articles.

Dimensions of articles of the character herein contemplated areso figured as to provide an ample safety factor. It is essential,

however, to provide extremely hard and uni form wearing surfaces. Such wearing surfaces are ordinarily produced by case hardening to effect the formation of a case of the desired thiclmess. I havefound that with articles having non-uniform fiber arrangements, the case hardening is extremely 1rregular tending to penetrate to greater depth at certain po'itions that at other portions. It will be obvious that this results in the production of gears having one or more teeth liable to chip or break off in service. These objections are entirely obviated by the prescntinvention, by reason of the uniform fiber disposition effected by the die rolling operation. thereby insuring a uniform case hardening throughout the entire body of the article,

Con-f the case being of uniform depth throughout, with consequent uniformity of strength.

The advantages of the present invention arise from the provision of an article of manufacture having uniform wearing qualities and uniform strength throughout, by reason of the preliminary shaping of the blanks in such manner as to insure uniform fiber disposition through the entire body of the blank. Further advantages of the invention arise from the method of producing articles of the character-herein contemplated, the die rolling not only insuring the desired uniformity, but also producing such articles on a much greater scale than can possibly be ob tained by either upsetting or hammer drawlVhile I have specifically referred herein I to gears, and to case hardening, it will be apparent from a consideration of the invention, specificatlon and claims that the invention is not limited to any particular article,

'heat treating or otherwise. I therefore use the term articles? in its generic .sense as including the range of articles to which the ining also as generic expression definitive of an operation to accomplish the desired result rather than any specific operation.

I claim: V

1. In the method of producing a pinion shaft and gear, the steps consisting in die rolling a leader to producea blank following the general contour of the finished article and in which the fibreis substantially symmetrically disposed with reference to the axis of the pinion shaft and gear, working on the blank to reduce it to substantially finished dimensions, and hardening the shaped blank.

2. As an article of manufacture, a pair of blanksfor the production of pinion shafts and gears, said blanks each having enlarged vention is applicable, and the term harden portions for the formation of the gear, the

blanks being arranged inend to end relation- WILLIAM P. WITHEROW.

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