Improvements in Apparatus for Cutting the Teeth of Bevel Wheels.
Year: 1894

page_text: Date of Application, 8th Nov., 1894
Complete Specification Left, 8th Aug., 1895-Accepted, 19th Oct., 1895
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Cutting the Teeth of Bevel
Wheels.
I, JOSEPH HAMILTON GIBSON, of 12 Brattan Road, Birkenhead, in the County
of Chester, Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention relates to apparatus for cutting the teeth of bevel wheels so that
the working surfaces of the teeth shall have, as nearly as possible, the theoretically
perfect configuration.
In the ordinary construction of bevel wheels the shape of the teeth is usually
correct as described on one or other of the conical bounding surfaces which limit
the length of the teeth, but in order that the rest of the tooth shall be of correct
configuration it is necessary that the working surface of the tooth shall be generated
by a line, one end of which is fixed at the vertex of the pitch cone, and the other
end of which is moved over the curve which gives the outline of the tooth on the
said conical bounding surface. In an ordinary wheel cutting machine these
conditions may be approximated to by suitably angling the cutting tool but they
can never be absolutely complied with, and the object of my present invention is to
provide a machine in which the cutting edge of the tool always moves in directions
coincident with the successive positions of the said generating line, so that it not
only cuts a tooth of correct shape on the conical bounding surface but one whose
shape at any transverse section is that which theoretical considerations show to be
the best.
A machine for cutting the teeth of bevel wheels constructed according to my
invention comprises, broadly, the following parts:-A mandrel on which the wheel
to be cut is supported, one end of the said mandrel being pivoted, and the position
of the wheel thereon being such that this pivot is coincident with the vertex of the
pitch cone, and the other end of the mandrel moving over a graduated are and being
provided with a suitable clamping device to locate it at the appropriate angle; a
dividing apparatus consisting preferably of a worm wheel keyed to the mandrel
and a worm operated by spur or other gearing whereby the wheel is divided in
the ordinary way; a slide in which the tool carriage moves, the said slide being
supported by an arm so pivoted to the frame of the machine as to be capable of
universal motion about a point coincident with the pivot of the mandrel, and
therefore with the vertex of the pitch cone of the wheel to be cut; and an enlarged
copy of the shape of the tooth to be cut which copy serves as a template to guide
the free end of the arm carrying the tool carriage. These different parts of the
machine are, of course, connected by a suitable frame which also carries a driving
shaft having an adjustable crank for giving the necessary reciprocating motion to
the tool carriage; and a pivoted feed screw working in a nut on the free end of the
slide arm may also be provided to control the movement of the said arm about the
guide or template and so regulate the cut.
The method of pivoting the arm so that it may have a universal radial motion
about the pivot of the mandrel, consists in making the arm fork-ended and pivoting
the fork ends to two brackets carried at the extremities of a semi-circular annular
plate guided in a circular guide whose centre is coincident with the pivot of the
mandrel, and as the horizontal axis of the forked end and the two brackets, passes
through the said pivot it will be seen that while the free end of the arm can be

page_text: moved about in any direction the centre line of the arm will always radiate about
the vertex of the pitch cone.
The machine is operated as follows;-An enlarged copy of the shape of the
tooth, as described on the outer bounding conical surface of the wheel, is con-
structed, which copy is as many times larger than the shape aforesaid as its distance
from the vertex is greater than the distance of the said bounding conical surface
therefrom the template to guide the end of the arm is now constructed from this
copy but in making the template, allowance is made for the fact that the
end of the arm is guided over the template by a roller; a constant quantity equal
to the radius of the roller is therefore added to the enlarged copy with the result
that the centre of the roller moves over the enlarged copy. The cutting corner
of the tool is so adjusted in its slide that it always moves in the line joining the
centre of the roller to the vertex of the pitch cone, and in this way the conditions
mentioned for obtaining a perfectly shaped tooth are complied with. As it is
necessary to use a corner of the tool for cutting it will be seen that after one side
of a tooth is cut it will be necessary to use the other corner of the tool to cut the
other side; this necessitates the tool being moved across the slide so as to bring the
other corner in the line joining the centre of the roller on the arm to the vertex of
the pitch cone.
I may use a milling cutter instead of an ordinary tool in which case provision
must of course be made for driving the cutter as the carriage reciprocates.
Dated this 7th day of November 1894.
SLOAN & LLOYD BARNES,
Castle Chambers, 26 Castle Street, Liverpool, Agents for the Applicant.
Improvements in Apparatus for Cutting the Teeth of Dever
Wheels.
J, JOSEPH HAMILTON GIBSON, of 12 Brattan Road, Birkenhead in the County
of Chester, 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 relates to apparatus for cutting the teeth of bevel wheels so that
the working surfaces of the teeth shall have, as nearly as possible, the theoretically
perfect configuration.
In the ordinary construction of bevel wheels the shape of the teeth is usually
correct as described on one or other of the conical bounding surfaces which limit
the length of the teeth, but in order that the rest of the tooth shall be of correct
configuration it is necessary that the working surface of the tooth shall be
generated by a line, one end of which is fixed at the vertex of the pitch cone,
and the other end of which is moved over the curve which gives the outline of
the tooth on the said conical bounding surface. In an ordinary wheel cutting
machine these conditions may be approximated to by suitably angling the cutting
tool but they can never be absolutely complied with, and the object of my present
invention is to provide a machine in which the cutting edge of the tool always
moves in directions coincident with the successive positions of the said generating
line, so that it not only cuts a tooth of correct shape on the conical bounding
surface but one whose shape at any transverse section is that which theoretical
considerations show to be the best.
In the accompanying drawings which illustrate my invention,
Fig. I is an elevation of the machine, partly in section on the line A. A. of

page_text: Fig. II is a plan, Fig. III a fragmentary section on the line D. D. or rig.
and Fig. 1V is a detail view.
Throughout the drawings similar parts are indicated by the same reference
figures, aud in the case of sections, the direction in which they are viewed is
indicated by the small arrows placed adjacent to the letters denoting the plane of
section.
1 is the mandrel on which the wheel to be cut is supported; one end of the
mandrel is carried in the pivotal bearing 3, the pivots of the bearing being so carried
in the bracket 4, fixed to the main frame 12, that the mandrel capable of angular
movement about the axis X. X. which passes through the apex of the pitch cone of
the wheel to be cut. The other end of the mandrel is supported in a bearing 5
which moves over, and which can be clamped to, a graduated arc 6, and the mandrel
is provided with a suitable dividing apparatus. In the drawings the bearing 5 is
constructed after the manner of the loose headstock of a lathe, and it carries a
dividing shaft on which is keyed a worm, gearing into a worm wheel 7 on the
mandrel, and the said dividing shaft is provided with a dividing plate and means for
operating it.
It will be
8 is the slide on which the tool carriage reciprocates; this slide is forked as
shown and the forked ends are pivoted on two studs 9; the studs 9 are carried
from the ends of a semicircular annular plate 10, guided in a circular guide 11
whose centre is coincident with the apex of the pitch cone, and the studs are so
placed that their axis also passes through the apex of the pitch cone.
seen therefore that the slide can be angled about either of two axes which intersect
at right angles at the apex of the pitch cone; in the drawings the position of the
slide is such that one of the axes coincides with the axis X. X. of the pivoted
bearing of the mandrel; the other axis Y. Y. is shown in Fig. I.
The tool carriage 13 reciprocates on the slide 8 being guided by the usual form
of sliding surfaces; the carriage 13 is provided with a tool box 14 which is
capable of being adjusted laterally, relatively to the carriage, by a traversing
screw after the manner of a slide rest. The carriage receives its reciprocating
motion from an adjustable crank 15 on the driving shaft of the machine, and the
connection between the carriage and the crank consists of a connecting rod 16,
having universal joints at each end (only one of which is, for the sake of clearness,
shown in the drawings), and an adjustable bracket 17 to allow the tool to be moved
to suit the wheel.
The tool is adjusted so that its cutting point moves in a line whose prolongation
passes through the point of intersection of the axes X. X. and Y. Y., and it will
be seen that if the tool be thus adjusted for any particular position of the slide,
the same conditions will obtain for any other position into which the slide may be
angled; this ensures that the cut will always take place in lines radiating from
the apex of the pitch cone, and it only remains to guide the slide as it is angled
so that each of the said lines shall pass through the profile of the tooth as described
on one of the bounding conical surfaces of the wheel, to ensure the formation of a
correctly shaped tooth.
-The slide is
The guiding of the slide, as it is angled, is effected as follows;-
provided with a guide roller 18 whose axis is on the prolongation of the line
joining the point of intersection of the axes X. X. and Y. Y. to the cutting point
of the tool. A template 19 is fixed normal to the axis of the roller and the
template is so shaped that as the roller runs over the guide surface the centre of it
describes a curve (shown in dotted lines in Fig. IV) which is an enlarged copy of
the shape of the tooth as described on the outer couical bounding surface of the
wheel, and the said copy is as many times larger than the shape aforesaid, as its
distance from the apex of the pitch cone is greater than the distance of the said
bounding surface therefrom.
The template is formed by marking out the enlarged copy of the tooth as
described, and then adding to the profile so obtained a constant quantity all round
equal to the radius of the guide roller 18.

page_text: After the space has been roughed out, which may be accomplished by feeding
the slide vertically downwards by means of a guide 20 which can be raised and
secured in position for this purpose, the profile of the tooth is cut out by the point
of the tool; and it will be seen that to do this one point of the tool must be used
for the right side and the other for the left side. In Fig. IV it is assumed that
the left side is being cut, the left. point of the tool must therefore be on the line
joining the centre of the roller 18 to the point of intersection of the axes X. X.
and Y. Y.; when however the right side of the tooth has to be cut the roller is
moved over to the other side of the template and the tool is traversed across the
carriage, by the means described, till the right point of the tool is on the line
joining the centre of the roller 18 to the point of intersection of the axes X. X.
and Y. Y. The roller 18 is kept in contact with the guide surface by means of a
spring 21 which can be applied on either side by placing the eccentric stud 22 in
one or other of the holes 23. The feed is regulated by a feed screw 24 pivoted to
the main frame 12, the nut on which is articulated to the slide 8 by means of a ball
joint and which is rotated by the hand-wheel 25.
The machine is driven by the usuai speed cone 26 and a Hy-wheel 27 may be
fitted to ensure steadiness of running.
Instead of an ordinary cutting tool, I may use a rotary cutter, in which case
means are of course provided for rotating the cutter as it reciprocates.
Automatic means may be provided to operate the feed screw.
I attach considerable importance to the fact that in a machine constructed
according to my invention a very considerably magnified copy of the shape of the
tooth may be used as a template, and for this reason the template is placed as far
away from the apex of the pitch cone as possible.
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;-
1. In apparatus for cutting the teeth of bevel wheels, in combination;-a
mandrel, on which the wheel is carried, capable of pivoting about an axis
containing the apex of the pitch cone and provided with dividing gear; a slide
pivoted on studs carried at the ends of an annular plate and capable of angular
movement about two rectangular axes intersecting in the apex of the pitch cone,
said slide being adapted to carry a reciprocating tool carriage with a transversely
adjustable tool box and having a guide roller adapted to move
over a fixed
template as the slide is angled; and means for reciprocating the tool carriage
and regulating the feed of the cutting tool; substantially as described and
illustrated.
2. In apparatus for cutting bevel wheels, in combination with the angling slide
and guide roller, the means for regulating the feed, comprising the template
shaped as specified, the reversible spring, the pivoted feed screw, and the nut
articulated to the slide; substantially as described and illustrated.
3. The combination and arrangement of parts forming the improved machine
for cutting the teeth of bevel wheels, substantially as described and illustrated in
the drawings.
Dated this 7th day of August 1895.
SLOAN & LLOYD BARNES,
Castle Chambers, 26 Castle Street, Liverpool,
Agents for the Applicant.