Improvements in Devices for Forming Gear Teeth.
Year: 1898

page_text: Date of Application, 2nd Apr., 1898-Accepted; 14th May, 1898
COMPLETE SPECIFICATION.
Improvements in Devices for Forming Gear Teeth.
I, OSCAR JAMES BEALE, of the City and County of Providence, State of Rhode Island,
United States of America, Mechanical Engineer, do hereby declare the nature of this
invention, and in what manner the same is to performed, to be particularly
described and ascertained, in and by the following statement :-
The present invention is based upon the principle that if two pitch surfaces be
rolled together without slip, a tooth upon one surface will develope or generate a
tooth upon the other pitch surface which is conjugate to the generating tooth, and
consists in a generator having a series of edges or points so arranged with relation to
the pitch surface that they will remove the surplus stock on the blank teeth and
reduce the teeth to the correct shape by the rolling together of the pitch surfaces of
the blank and generator. As the pitch surfaces of the blank and generator are rolled
together, each edge or point of the generator removes a portion of the surplus stock
on the blank and forms a conjugate line or point on the surface of a tooth of the
blank. Thus line by line or point by point the surfaces of the teeth upon the blank
are developed or generated by the action of successive edges or points upon the
generator. The edges or points on the generator correspond to lines or points in the
tooth surfaces of a gear conjugate to the gear to be generated, and in order that
the edges or points of the generator which act successively upon the same tooth of
the blank may remove the surplus stock at varying points upon the tooth surface, the
location of the edges or points with relation to the pitch surface of the generator is
varied.
The generator is preferably in the form of a gear, and the edges or points may be
formed by cutting away or removing portions of the tooth surfaces of the gear. The
arrangement and character of the edges or points may be varied as desired without
departing from the invention. Thus a series of edges or points may be formed upon
the same tooth surface if desired, and these edges or points may be so arranged that
the surfaces of the tooth become in effect abrading surfaces. In such a case a tooth
upon the generator will generate a conjugate tooth upon the blank, the edges or points
upon a single tooth acting successively upon the surface of a tooth upon the blank
as the pitch surfaces roll together and cutting away or abrading the surplus stock.
Again a single edge or line of points may be formed upon each tooth surface.
this case as the pitch surfaces roll together an edge or series of points upon the
generator will generate a line upon a tooth surface of the blank, and the number of
teeth in the generator and in the blank should be so proportioned that each
generator tooth will act upon a different tooth in the blank at each revolution of the
generator until every tooth of the blank has been engaged by every tooth of
the generator, and has therefore been acted upon successively by all the cutting
edges or points upon the generator.
In
In this case, as well as where a series of edges or points are formed on a single
tooth of the generator, the generator may be so formed that it may act to drive the
blank, or be driven thereby, while the blank teeth are being reduced to the correct.
form, and it is preferred to so construct the generator that it may thus drive the
blank. If desired, however, the surfaces of the generator teeth may be so cut away.:

page_text: that the generator will not act as a driver, in which case mechanism must be used
for producing the proper rolling motion between the pitch surfaces of the blank and
generator.
The invention may be used in the manufacture of any form of gearing, but is
especially useful in the manufacture of bevel-gearing in which the curvature of the
tooth surfaces change from one end of a tooth to the other, and which cannot there-
fore be accurately cut in the usual way, but require filing and fitting before they will
run properly. In the application of the invention to the manufacture of bevel-
gearing the pitch cone of the generator may be varied, and the edges or points of
the generator may be arranged to develope any desired form of teeth upon the blank,
but it is preferred to use a generator in the form of a crown gear, and to so arrange
the edges or points that they correspond to edges or points in the surfaces of teeth
having plane surfaces, since such surfaces may be readily and accurately cut, and the
gears which are formed by such a generator will accurately run with each other and
form an interchangeable set.
-
Referring to the drawings,
Fig. 1 is a diagrammatic view indicating two forms of generators, and the manner
in which they operate upon the gear blank.
Fig. 2 is a perspective view of a preferred form of generator for generating the
teeth of bevel-gears.
Fig. 3 is an end elevation of a modified form of generator.
Fig. is a detail showing a portion of a modified form of generator, and
Fig. 5 is a plan view of so much of a milling machine as is necessary to show one
manner of using the generator.
In Fig. 1, A represents a portion of a generator in the form of a spur gear having
a series of edges a arranged in varying relation to the pitch surface of the generator.
These edges a are formed by cutting away portions of the surface of the gear teeth
and a series of edges are formed upon each tooth surface so that said surfaces become
substantially filing or abrading surfaces. B represents a blank, the teeth b of which
have been roughed out to approximately the correct form. As the pitch surfaces of
the blank and generator roll together, the edges a upon the generator, acting upon
the teeth of the blank, remove the surplus stock and reduce the teeth to the correct
form shown at c. D in the same figure shows a similar generator in the form of a
rack, and it will be understood that where the term "gear" is used in the claims and
specification, it is intended to include racks also.
In Fig. 2 is shown a preferred form of generator for forming the teeth of bevel-
gears. This generator is in the form of a crown-gear E which is the dividing line
between an external bevel-gear and an internal bevel-gear, and corresponds to the
rack in spur gearing, that is to say, its pitch surface is a plane surface. The
teeth e, e of the generator may be of any desired shape, but are perferably truncated
wedges in cross section, and their surfaces plane surfaces as this form of teeth may
be conveniently and accurately cut. The generating edges may be formed upon the
generator in any desired manner, but it is preferred to form a series of edges upon
each surface and to convert the surfaces of the teeth into substantially file surfaces
which will act to abrade or cut away the surplus stock of the blank by an action
similar to the action of a file. The edges are produced by removing portions of the
surfaces of the teeth, and the direction of these edges in relation to the pitch surface
may and preferably does vary upon different teeth. The edges may be sub-divided
by grooves so that said edges become substantially points, and the surfaces of the
teeth are formed by a number of points arranged in varying relation with the pitch
surface. In the generator shown the edges are formed by cutting a series of grooves
in the surfaces of the teeth at varying distances from the pitch surface. When the
pitch surface of this generator rolls upon the pitch surface of a blank, the teeth of
which have been roughed to approximate from the edges or points upon each tooth
act successively upon the surface of a blank tooth, and thus the surfaces of the blank
teeth are reduced to the correct shape conjugate to the surfaces of teeth of the
generator by the cutting or abrading action of the generating surfaces.

page_text: Instead of generating the surface of a blank tooth, by a series of edges or points
upon the same surface of a generator tooth, the surface of a tooth on the blank may
be generated by the action of a series of surfaces of different teeth of the generator,
and the number of edges upon the same tooth surface may be reduced to a single
edge if desired. In Fig. 3 is shown one form of such generator. In this view the
generator is shown in the form of a bevel-gear G having varying portions of its
teeth g removed to form edges g¹ which lie in the surfaces of the gear teeth. The
dotted lines indicate the outline of the portions of the teeth which are removed.
The portions of the teeth remaining are preferably so related to each other that the
edges upon every tooth are in a different relation to the pitch surface from the edges
upon every other tooth.
It is also preferred to so cut away the teeth that any tooth
having the greater portion cut away will lie between two teeth which are only
slightly cut away so that there will always be at least one tooth in mesh with the
blank teeth of sufficient height to drive said blank. With this form of generator
the number of teeth in the blank should be so related to the number of teeth in the
generator that each tooth of the generator will in turn act upon each tooth of the
blank.
Then at each revolution of the blank one of the tooth surfaces of the generator
will act upon a tooth surface of the blank, and the edges gl upon that surface of the
generator will remove a portion of the surplus stock upon the blank tooth and
generate a line upon the tooth surface of the blank. When the blank has made as
many revolutions as there are teeth in the generator, every tooth surface of the
blank will have been acted upon by an edge upon each of the teeth of the generator,
and the blank tooth will be generated therefrom by generating a series of lines upon
the tooth surfaces.
In case it is not desired to drive the blank by the action of the generator teeth,
the surfaces of the generator teeth may be entirely cut away leaving only a series of
edges. A fragment of such a generator is indicated in Fig. 4 in which the dotted
lines indicate the form of tooth which is conjugate to the teeth to be formed by the
generator. In this form of generator the edges are formed by cutting away the
tops of the teeth, and the surfaces of the teeth below the edges are also cut away.
The edges are arranged in varying relations to the pitch surface as in the other forins
of generators. The operation is the same as the operation of the generator shown in
Fig. 3 so far as the action of the edges upon the blank is concerned, but the generator
will not act to drive the blank.
In Fig. 5 is shown one manner of using a generator which is adapted to drive the
blauk. In said figure, 1 represents the spindle of a milling machine. The genera-
tor 8 is secured to an arbor 2 carried by the spindle 1, and a gear blank 3 is mounted
to rotate freely upon an arbor 4 secured to the support 5 carried by the carriage 6.
The carriage 6 is adjusted to bring the axis of the blank 3 into proper relation to the
axis of the generator 8, and the teeth of the blank 3 are brought into mesh with the
teeth of the generator.
The spindle now revolves and the saddle 7 is gradually fed forward until the pitch
surfaces of the blank and generator are in contact. In case a generator with teeth
having abrading surfaces is used, a single revolution of the blank after the pitch
surfaces are in contact will be sufficient to finish the teeth of the blank, but in case a
generator is used in which the generating is done by the action of edges or points
located upon the different teeth of the generator, then the blank should make as
many revolutions after the pitch surfaces are in contact as there are teeth in the
generator. Instead of mounting the generator on the spindle 1, the blank may be
mounted thereon, if desired, in which case the blank will act to drive the
generator.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is

page_text: stock when the pitch surfaces of the generator and blank are rolled together, substan-
tially as described.
2. A device for generating gear teeth which removes the surplus stock when the
pitch surfaces of the generator and blank are rolled together, substantially as
described.
3. A device for generating gear teeth provided with a series of edges or points
corresponding to lines or points in the tooth surfaces of a gear, and arranged in
varying relation to the pitch surface of said gear, substantially as described.
4. A device for generating gear teeth provided with a series of edges or points
corresponding to lines or points in the tooth surfaces of a bevel-gear, and arranged in
varying relations to the pitch surface of the gear, substantially as described.
5. A device for generating gear teeth in the form of a gear having a series of edges
or points arranged in varying relation with the pitch surface, substantially as
described.
6. A device for generating gear teeth in the form of a bevel-gear having a series of
edges or points arranged in varying relation to the pitch surface, substantially as
described.
7. A device for generating gear teeth in the form of a crown-gear having a series
of edges or points arranged in varying relation to the pitch surface, substantially as
described.
8. A device for generating gear teeth in the form of a gear having a series of edges
or points in the same tooth surface, substantially as described.
9. A device for generating gear teeth in the form of a gear having a series of edges
or points in each tooth surface, the arrangement of the edges or points varying upon
alternate teeth, substantially as described.
10. A device for generating gear teeth in the form of a gear having varying
portions of the tooth surfaces removed to form edges or points, substantially as
described.
11. A device for generating gear teeth in the form of a gear provided with teeth
having abrading surfaces, substantially as described.
12. A device for generating gear teeth in the form of a gear provided with teeth
having plane abrading surfaces, substantially as described.
13. A device for generating gear teeth in the form of a bevel-gear provided with
teeth having abrading surfaces, substantially as described.
14. A device for generating gear teeth in the form of a crown-gear provided with
teeth having abrading surfaces, substantially as described.
15. A device for generating gear teeth in the form of a crown-gear provided with
teeth having plane abrading surfaces, substantially as described.
16. The generator shown in Fig. 2.
17. The generator shown in Fig. 3.
18. The generator shown in Fig. 4.
Dated this 14th day of March 1898.
OSCAR JAMES BEALE.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.