Improvements in the Manufacture of Bevel Gear Wheels, and Appliances therefor.
Year: 1898

page_text: Date of Application, 22nd Mar., 1898-Accepted, 4th June, 1898
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Bevel Gear Wheels, and
Appliances therefor.
I, JAMES WARING SEE, of Hamilton, Butler County, Ohio, United States of
America, Mechanical Engineer, do hereby declare the nature of this invention, and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This invention pertains to improvements in toothed gearing and in the method
and appliances for making the same, and the invention will be readily understood
from the following description taken in connection with the accompanying drawings
in which:-
Fig. 1 is a diametrical section of a typical bevel gear to be produced.
Fig. 2 a side elevation, half diametrical section, of the same gear partially
finished:
Fig. 3 a diametrical section of the partially finished gear in conjunction with
exemplifying upsetting dies:
Fig. 4 a face view of one of the exemplifying upsetting dies:
Fig. 5 a end elevation of a few of the teeth of the finished product:
Fig. 6 an end elevation of a few of the teeth of the partially finished product:
Fig. 7 an end elevation, on an enlarged scale, of one of the finished teeth,
the dotted line giving the contour of the partially finished tooth: and
Fig. 8 a front elevation of a typical machine for operating the dies.
It has been an accepted maxim that accurate toothed gearing could only be
produced by cutting processes. In cutting spur gears one cut may finish a tooth-
space and the cutting cost will obviously be directly as the number of teeth in
the gear.
Bevel gearing making any pretension to accuracy cannot be produced
with a single cut for each tooth-space, even crudely cut work calling for two
cuts for each tooth-space. Regardless of expense, correct bevel gears cannot
have their teeth cut with rotary cutters. In correctly formed bevel gears all of
the lines lying along the teeth converge to a focus, and this result cannot be
produced by circular toothed contour cutters. It has therefore become customary,
in using circular cutters for cutting bevel gears, to accept distorted teeth. The
focal planing machine, planing the sides of the teeth with a sharp tool-corner
moving in focal lines, is capable of producing theoretically perfect work, but in
practice the delicate tool-corner wears away and accuracy becomes defeated.
Spiral cutters making motions of reciprocation and partial rotation, would produce
theoretically correct bevel gearing, but the work is slow and expensive. In
any of the cutting operations the cost increases with the number of teeth.
accurate bevel gears are required in large quantities the question of cost of
tooth-cutting becomes a serious one, and the cost and maintenance of plant is
equally serious.
Where
"By my improved method it is believed that bevel gearing can be produced
in quantities at a trifling cost compared with that of any tooth-cutting process,
and with a degree of accuracy not attainable in a system of extended manufacture

page_text: by the tooth-cutting process. The gears produced by my improved method
must be of metal possessing some degree of malleability, say wrought iron or
steel. I form a tooth-gear by die or drop forging process, with teeth abnormally
thin and high I then upset the teeth to proper thickness within a die confining
the tooth sidewise and controlling its contour.
Referring to the drawing:-
1, indicates a typical bevel gear such, for instance, as is adapted for use on
bicycles, such gears being required in great numbers and of exceptional
accuracy:
2, the finished teeth thereof, having the usual approved cross-sectional contour:
3, the partially finished gear, the same being a drop forging of but ordinary
accuracy of production:
4, the teeth of the partially finished gear, the same being abnormally thin
and high:
5, material in the partially finished gear under the teeth 4:
6, an anvil-die on which the partially finished gear is laid:
7, an upsetting die adapted to operate upon the teeth of the partially finished
gear:
8, the tooth spaces of the upsetting die, the same conforming in cross-sectional
contour with the teeth 2 of the finished product, the tooth-spaces in the upsetting
die having greater lengthwise extent than the teeth in the partially finished
gear:
9, (Fig. 7) the flanks of the teeth of the finished product:
10, the crown of the teeth of the partially finished gear, the same representing
the abnormal height of these teeth as compared with the teeth of the finished
product: and
11, a typifying machine, in the form of a hydrostatic press, for pressing the dies
together.
In making the gears a gear is first produced by drop forging or equivalent
process, with teeth of abnormal thinness and height, only good ordinary accuracy
and smoothness being sought for at this stage of the process. The partially
finished gear is then accurately faced on its back under the metal 5 so as to lie
fairly on the anvil die 6. The partially finished gear is then to be pickled and
cleaned so as to be as free as possible from scale and, if found needful, it is to be
annealed. In facing the back of a gear it is to be chucked true with the roots of
the teeth or the floors of the tooth-spaces. The partially finished gear is now
to be subjected to powerful pressure between the anvil-die and the upsetting
die, the upsetting die squeezing down the crowns 10 of the teeth and expanding
them in thickness to fill the tooth-spaces of the upsetting die.
The gear is
then to be chucked true and the necessary lathe work done upon it to remove
extra metal 5 and the surplus metal at the ends of the teeth and to bring the web
to the proper thickness.
The upsetting die is to be formed with extreme accuracy. Assume that, by
the best known methods of cutting bevel gearing, it is proposed to produce a single
gear of great accuracy. Such a gear would be expensive, but the expense would
be multiplied if great numbers of such gears were wanted. The upsetting die 7
is to be made with the same care and accuracy as in the case of the assumed
single bevel gear, but when this die is done the production of a large number of
accurate gears by means of the die does not call for a multiplication of the expense.
By the most accurate system of tooth-cutting the wear of the cutting tool will
result in eccentricity of gear or in thickening of the teeth in succession along
the series of teeth being cut. By proper testing and correction a sufficiently
accurate result may be attained, either in a cut gear or in the upsetting die 7.
But the cost of accuracy in cut gearing will be multiplied as more gearing is
produced, while with the upsetting dies the cost is not multiplied as more gears
are produced. The gear teeth produced by the upsetting; die will therefore
possess the accuracy of the die and that accuracy can be considerably in excess

page_text: of anything practically attainable in the production of cut gears in quantities.
The upsetting operation is to be performed while the partially finished gear is
cold and consequently the faces of the teeth of the finished gear are formed of
highly condensed metal swaged between the sides of the tooth-spaces of the
upsetting die. Should it be desirable to harden the finished gears some distortion
may result but no superior degree of distortion and hardening is chargeable to
the improved method by which the gear was produced.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. In means for making toothed gears, the combination, substantially as set
forth of a toothed forging die, a toothed upsetting die corresponding with said
forging die but having its toothed-spaces of greater width and less depth than the
tooth-spaces in said forging die, and anvil dies to oppose and co-operate with said
toothed dies.
2. In means for making toothed gears, the combination, substantially as set
forth, of a toothed upsetting die adapted to receive a partially finished toothed
gear of malleable material, the tooth-spaces of said die being of greater width
and less depth than the teeth in said partially finished gear, an anvil die to engage
upon the opposite side of said partially finished gear, and means for forcibly
approaching the two dies while the partially finished gear is between them.
3. That improvement in the art of making toothed gears which consists, first,
in forging the gear with teeth of abnormal height and thinness, second, in
pickling the partially finished gear, and, third, in upsetting the teeth to normal
height and thickness.
Dat this 00nd lov of March 1998