Year: 1899

page_text: I, CHARLES DENTON ABEL, of Birkbeck Bank Chambers, Southampton Build-
ings, in the County of London, Consulting Engineer and Chartered Patent
Agent, do hereby declare the nature of this invention (as communicated to me
from abroad by Chemnitzer Strickmaschinen Fabrik, of 60, Zschopauer Strasse,
Chemnitz, Germany) to be as follows -
This invention relates to a method for cutting worm-wheels by means of worm
cutters in a similar manner to the cutting of spur-wheels.
For the clearer understanding of the invention therefore, the cutting of a
spur-wheel by means of a single thread worm cutter shall first be described.
In cutting the teeth of a spur-wheel by means of a single thread worm cutter,
the latter is made to perform as many revolutions during one revolution of the
spur wheel blank as teeth have to be cut on the latter.
The axis of the cutter being situated at an angle to the plane of the wheel to
be cut corresponding to the pitch of the worm cutter, the latter is advanced
in a direction parallel to the axis of the wheel, whereupon it will begin to cut
some of the teeth on the latter, and in revolving while at the same time the
wheel blank is rotated, it will by degrees cut the commencement of all the
teeth on the latter on then gradually advancing the worm cutter in the same
direction, it will gradually cut the teeth across the whole width of the wheel
periphery in a direction parallel with the axis of the wheel, as is required for
spur wheels. Figs. 1 to 4 of the accompanying drawings illustrate this process.
Fig. 1 shews the angular position of the worm cutter before commencement
of the work, Fig. 2 shews its position after the wheel blank has completed one
revolution Fig. 3 shews the position after about one half the width of the teeth
have been cut by a corresponding number of revolutions of the wheel, and
Fig. shews the finished spur wheel with the worm cutter moved beyond it.
The present invention for cutting worm-wheels is distinguished from the
above described method mainly in that the advance of the worm cutter does not
take place in a rectilinear direction but in a helical direction relatively to the
axis of the wheel blank, as shewn at Figs. 6 and 7.
A direct movement of the worm cutter in this direction leads to practical
difficulties but indirectly it can readily be obtained as the resultant of a recti-
lineal forward motion (as with the spur wheel cutter) and a lead in the advance
of either the cutter or the wheel blank during the rotation. Thus according to
the present invention a worm wheel is produced in such manner that the number
C
077

page_text: of revolutions of the worm cutter which are necessary for cutting the complete
teeth of a spur wheel as above described has to be increased, for example by one
revolution while the number of revolutions of the wheel blank remains the
same as before. This one additional revolution of the cutter in combination
with its advancing motion gives as resultant the helical direction required for
the teeth of the worm wheel. This action is indicated at Fig. 5. It will be
evident that by a kinemetic reversal of the action, the helical motion can be
imparted to the wheel blank, or the two separate motions, performed only by
the cutter as above described can also both be performed by the wheel blank,
or the one motion can be effected by the cutter (either the forward motion or
the additional rotation) and the other by the wheel blank. For in all these
cases the same end result will be obtained, namely the relative change of posi-
tion between the cutter and the wheel blank which has to be effected for
producing helically formed teeth.
°
In. the above description it has been assumed for the sake of simplicity that
the number of revolutions of the worm cutter relatively to a certain number of
revolutions of the wheel blank have to be increased for example by one revolu-
tion. It will be evident however that every other proportional increase of the
number of revolutions can be employed, such for instance two, three or more
additional revolutions or a fraction of a revolution, or one or more and a frac-
tion &c., according as a greater or smaller pitch of the worm teeth may be
required. The number of revolutions of the worm cutter could also be reduced
by one or more revolutions or fractions thereof, as above stated instead of being
increased, whereby helical teeth of the opposite pitch would be produced with
an opposite inclination of the axis of the worm cutter.
Also, instead of a single thread worm cutter, cutters with two or more threads
may be used in the above described manner. In this case the number of revolu-
tions of the cutter would be decreased in proportion to the number of its threads, as
at each revolution of the wheel blank two, three, or more teeth will be cut
simultaneously.
In the above described manner worm wheels can be cut by one and the same worm
cutter having a pitch varying from 0° to 180°, according as the cutter has one
or more additional or one or more less revolutions imparted to it. At the limits 0°
and 180° the worm wheel of course reverts to the ordinary worm and at 90°
the cutter forms spur wheels. In all cases the worm cutter must of course have
the corresponding greater or less inclination to the axis of the worm wheel
blank. so that the direction of pitch of the cutter teeth always coincide with
the direction of inclination of the teeth spaces.
Figs. 9 to 11 of the drawings shew a machine by means of which the above
described method can be carried out in the case in which the relative motion of
the worm cutter to that of the wheel blank in a helical path round the latter is
effected by an axial advancing motion, and the above described increase or
decrease of the number of revolutions of the cutter.
The worm cutter is designated by a and the wheel blank to be provided with
helical teeth, by b. Both are made to rotate on their axes, as ordinary worm and
worm wheel gear, with a prescribed motion, according to the ratio between the
number of threads of the cutter and number of teeth of the wheel. this motion
being effected by means of intermediate gear. The rotation of the wheel blank b
and worm cutter a is effected from a shaft with stepped belt pullies d. In
the arrangement shewn the rotation of the wheel blank b is obtained through
the train of wheels e, bevil wheels f and worm and worm wheel gear driving
the shaft h on which the wheel blank is situated as shewn at Figs. 9, 10 and 11,
while the rotation of the worm. cutter, is obtained through intermediate gear
which produces a rectilinear advance of the cutter towards the wheel blank and
the requisite acceleration or retardation of the revolutions thereof relatively to
the revolutions of the wheel blank. In addition the cutter is so arranged that

page_text: its axis can be adjusted in any angular direction relatively to the axis of the
wheel blank, as at Figs. 8, 9, 10, and 11.
The intermediate mechanism employed in the arrangement shewn for effecting
the above described relative motion of the worm. cutter a is as follows:
The rotary motion transmitted from the driving shaft c to the cutter is effected
by means of a train of differential gear i, k, n, which transmits the rotation of
shaft c to shaft g and from this by means of the bevil gear r and s and spur
wheels to the cutter shaft u.
The gear i, k, n, is so arranged that the wheel i is fixed on shaft c while wheel k
revolves loose on a pin m projecting at right angles from the shaft q.
The pinion n is fixed to a worm wheel o both being mounted loose on the
shaft g.
The worm wheel o can have a special rotation imparted to it through a worm p
and spur wheels z as also bevil wheels y from a spindle v.
This special rotation effects the acceleration of the rotary motion of the cutter
relatively to the wheel blank. The spindle is constructed as a screw spindle
the screw thread of which serves to shift the slide carrying the cutter in the
direction of the shaft carrying the wheel blank b, for which purpose the arm x
of the slide is formed to serve as nut for the spindle.
This shifting motion effects the rectilinear motion of the cutter towards the
wheel blank.
The cutter a together with its support and the driving gear t is mounted on a
disc rotatable round a vertical axis, the said axis serving at the same time as
the shaft for the horizontal bevil wheels so that the rotation of the cutter can
be effected from the shaft 7 in every position into which the disc or the cutter
may be adjusted relatively to the wheel blank for cutting helical teeth thereon
at a greater or less pitch.
The working operation in cutting helical teeth is as follows:
If a wheel blank is to have helical teeth cut thereon by means of a single
thread worm cutter, the latter must have a certain increased or decreased number
of rotations imparted to it relatively to the number of teeth to be formed on
the wheel.
For this purpose the shaft q has an accelerated or retarded motion imparted
to it, proportionate to the pitch of the helical line of the teeth to be cut, by means
of a corresponding rotation of the worm wheel o actuated by the spur gear z,
bevil geary and spindle .
Assuming for instance that a single thread cutter with a pitch of 20 m.m. a
screw spindle with 5 m.m. pitch and a wheel blank of a width of 20 m.m. be
employed, on which latter thirty teeth with a pitch of 45° are to be cut, thus
requiring for one revolution of the wheel blank 30 revolutions of the cutter;
then in order to cause the cutter to travel over a wheel blank 20 m.m. wide,
4 revolutions of the screw spindle are required (its pitch being 5 m.m.) whereby
the slide carrying the cutter will be shifted 20 m.m. But at the same time
the cutter is required to describe helical lines of 45° pitch relatively to the wheel
blank.
For this purpose the 4 revolutions of the screw spindle are made to act in
such manner upon the cutter through the wheels y, and the differential
gear i, k, n as to cause it to perform one revolution more (or less). This
additional revolution is effected during the advance of the slide through 20 m.m.
and during rotation through 20 m.m. of the wheel blank. The resultant of
these two separate motions of 20 m.m. each, will produce the relative motion
between cutter and wheel blank at an inclination of 45° to the wheel axis.
By the above described method worm wheels with any desired number of teeth
can be cut by means of one and the same worm cutter.
By this limitation to one cutting tool the occurrence of faults is correspond-
ingly limited to those existing in such tool. The work of cutting the teeth is
rendered independent of the care and intelligence of the operatives and it can

page_text: be carried out rapidly and cheaply as the personal manipulations are limited
to the introduction of a fresh wheel blank, and the removal of the finished
wheel.
ד.
•
1
1
1000
ABEL & IMRAY,
Agents for the Applicant."
Method and Apparatus for Cutting Worm-wheels.
I, CHARLES DENTON ABEL, of Birkbeck Bank Chambers, Southampton Build-
ings, in the County of London, Consulting Engineer and Chartered Patent
Agent, do hereby declare the nature of this invention (as communicated to me
from abroad by Chemnitzer Strickmaschinen Fabrik, of 60, Zschopauer Strasse,
Chemnitz, Germany) 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 a method for cutting worm-wheels by means of worm
cutters in a similar manner to the cutting of spur-wheels.
For the clearer understanding of the invention therefore, the cutting of a
spur-wheel by means of a single thread worm cutter shall first be described..
In cutting the teeth of a spur-wheel by means of a single thread worm cutter,
the latter is made to perform as many revolutions during one revolution of the
spur wheel blank as teeth have to be cut on the latter.
The axis of the cutter being situated at an angle to the plane of the wheel to
be cut corresponding to the pitch of the worm cutter, the latter is advanced
in a direction parallel to the axis of the wheel, whereupon it will begin to cut
some of the teeth on the latter, and in revolving while at the same time the
wheel blank is rotated, it will by degrees cut the commencement of all the
teeth on the latter; on then gradually advancing the worm cutter in the same
direction, it will gradually cut the teeth across the whole width of the wheel
periphery in a direction parallel with the axis of the wheel, as is required for
spur wheels. Figs. 1 to 4 of the drawings accompanying my Provisional Specifi-
cation illustrate this process. Fig. 1.shows the angular position of the worm
cutter before commencement of the work, Fig. 2 shews its position after the
wheel blank has completed one revolution, Fig. 3 shews the position after about
one nalf the width of the teeth have been cut by a corresponding number of
revolutions of the wheel, and Fig. 4 shews the finished spur wheel with the
worm cutter moved beyond it.
The present invention for cutting worm-wheels is distinguished from the
above described method mainly in that the advance of the worm cutter does not
take place in a rectilinear direction but in a helical direction relatively to the
axis of the wheel blank, as shewn at Figs. 6 and 7.
A direct movement of the worm cutter in this direction leads to practical
difficulties but indirectly it can readily be obtained as the resultant of a recti-
lineal forward motion (as with the spur wheel cutter) and a lead in the advance
of either the cutter or the wheel blank during the rotation. Thus according to
the present invention a worm wheel is produced in such manner that the number
of revolutions of the worm cutter which are necessary for cutting the complete
teeth of a spur wheel as above described has to be increased, for example by one
revolution while the number of revolutions of the wheel blank remains the
same as before. This one additional revolution of the cutter in combination
with its advancing motion gives as resultant the helical direction required for
the teeth of the worm wheel. This action is indicated at rig. 5. It will be
evident that by a kinemetic reversal of the action, the helical motion can be

page_text: imparted to the wheel blank, or the two separate motions, performed only by
the cutter as above described can also both be performed by the wheel blank,
or the one motion can be effected by the cutter (either the forward motion or
the additional rotation) and the other by the wheel blank. For in all these
cases the same end result will be obtained, namely the relative change of posi-
tion between the cutter and the wheel blank which has to be effected for
producing helically formed teeth.
In the above description it has been assumed for the sake of simplicity that
the number of revolutions of the worm cutter relatively to a certain number of
revolutions of the wheel blank have to be increased for example by one revolu-
tion. It will be evident however that every other proportional increase of the
number of revolutions can be employed, such as for instance, two, three, or more
additional revolutions or a fraction of a revolution, or one or more and a frac-
tion &c., according as a greater or smaller pitch of the worm teeth may be
required. The number of revolutions of the worm cutter could also be reduced
by one or more revolutions or fractions thereof, as above stated instead of being
increased, whereby helical teeth of the opposite pitch would be produced with
an opposite inclination of the axis of the worm cutter.
Also, instead of a single thread worm cutter, cutters with two or more threads
may be used in the above described manner. In this case the number of revolu-
tions of the cutter would be decreased in proportion to the number of its threads, as
at each revolution of the wheel blank two, three, or more teeth will be cut
simultaneously.
In the above described manner worm wheels can be cut by one and the same worm
cutter having a pitch varying from 0° to 180°, according as the cutter has one
or more additional or one or more less revolutions imparted to it. At the limits 0°
and 180° the worm wheel of course reverts to the ordinary worm and at 90°
the cutter forms spur wheels. In all cases the worm cutter must of course have
the corresponding greater or less inclination to the axis of the worm wheel
blank, so that the direction of pitch of the cutter teeth always coincide with
the direction of inclination of the teeth spaces.
Figs. 9 to 11 of the drawings shew a machine by means of which the above
described method can be carried out in the case in which the relative motion of
the worm cutter to that of the wheel blank in a helical path round the latter is
effected by an axial advancing motion, and the above described increase or
decrease of the number of revolutions of the cutter.
The worm cutter is designated by a and the wheel blank to be provided with
helical teeth, by b. Both are made to rotate on their axes, as ordinary worm and
worn wheel gear, with a prescribed motion, according to the ratio between the
number of threads of the cutter and number of teeth of the wheel, this motion
being effected by means of intermediate gear. The rotation of the wheel blank b
and worm cutter a is effected from a shaft c with stepped belt pullies d. In
the arrangement shewn the rotation of the wheel blank bis obtained through
the train of wheels e, bevil wheels f and worm and worm wheel gear y driving
the shaft h on which the wheel blank is situated as shewn at Figs. 9, 10 and 11,
while the rotation of the worm. cutter, is obtained through intermediate gear
which produces a rectilinear advance of the cutter towards the wheel blank and
the requisite acceleration or retardation of the revolutions thereof relatively to
the revolutions of the wheel blank. In addition the cutter is so arranged that
its axis can be adjusted in any angular direction relatively to the axis of the
wheel blank, as at Figs. 8, 9, 10, and 11.
The intermediate mechanism employed in the arrangement shewn for effecting
the above described relative motion of the worm cutter a is as follows:
The rotary motion transmitted from the driving shaft c to the cutter is effected
by means of a train of differential gear i, k, n, which transmits the rotation of
shaft c to shaft q and from this by means of the bevil gear rands and spur
wheels to the cutter shaft u.

page_text: The gear ik n is so arranged that the wheel is fixed on shaft a while wheel k
revolves loose on a pin me projecting at right angles from the shaft q.
The pinion is fixed to a worm wheel o both being mounted loose on the
shaft q.
The worm wheel o can have a special rotation imparted to it through a
and spur wheels as also bevil wheels y from. a spindle e.
worm
P
This special rotation effects the acceleration of the rotary motion of the cutter
relatively to the wheel blank. The spindle is constructed as a screw spindle
the screw thread of which serves to shift the slide carrying the cutter in the
direction of the shaft carrying the wheel blank b, for which purpose the arm æ
of the slide is formed to serve as nut for the spindle.
This shifting motion effects the rectilinear motion of the cutter towards the
wheel blank.
The cutter together with its support and the driving gear t is mounted on a
disc rotatable round a vertical axis, the said axis serving at the same time as
the shaft for the horizontal bevil wheels so that the rotation of the cutter can
be effected from the shaft q in every position into which the disc or the cutter
may be adjusted relatively to the wheel blank for cutting helical teeth thereon
at a greater or less pitch.
The working operation in cutting helical teeth is as follows:
If a wheel blank is to have helical teeth cut thereon by means of a single
thread worm cutter, the latter must have a certain increased or decreased number
of rotations imparted to it relatively to the number of teeth to be formed on
the wheel.
For this purpose the shaft y has an accelerated or retarded motion imparted
to it, proportionate to the pitch of the helical line of the teeth to be cut, by means
of a corresponding rotation of the worm wheel o actuated by the spur gear z,
bevil gear y and spindle v.
Assuming for instance that a single thread cutter with a pitch of 20 m.m. a
screw spindle with 5 m.m. pitch and a wheel blank of a width of 20 m.m. be
employed on which latter thirty teeth with a pitch of 45° are to be cut, thus
requiring for one revolution of the wheel blank 30 revolutions of the cutter;
then in order to cause the cutter to travel over a wheel blank 20 m.m. wide,
4 revolutions of the screw spindle are required (its pitch being 5 m.m.) whereby
the slide w carrying the cutter will be shifted 20 m.m. But at the same time
the cutter is required to describe helical lines of 45° pitch relatively to the wheel
blank.
For this purpose the 4 revolutions of the screw spindle are made to act in
such a manner upon the cutter through the wheels y, z and the differential
gear i, k, n as to cause it to perform one revolution more (or less). This
additional revolution is effected during the advance of the slide through 20 m.m.
and during rotation through 20 m.m. of the wheel blank. The resultant of
these two separate motions of 20 m.m. each, will produce, the relative motion
between cutter and wheel blank at an inclination of 45° to the wheel axis.
By the above described method worm wheels with any desired number of teeth
can be cut by means of one and the same worm cutter.
By this limitation to one cutting tool the occurrence of faults is correspond-
ingly limited to those existing in such tool. The work of cutting the teeth is
rendered independent of the care and intelligence of the operatives and it can
be carried out rapidly and cheaply as the personal manipulations are limited
to the introduction of a fresh wheel blank, and the removal of the finished
wheel.
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. The method of cutting worm-wheels by means of worm cutters whereby

page_text: the wheel blank and cutter having imparted to them in addition to their rotary
motion, a relative motion to each other in the direction of a helical line, sub-
stantially as described.
2. In the method of cutting worm-wheels by means of worm cutters referred
to in the first claim, producing the relative motion between the wheel blank
and the cutter by imparting either to the wheel blank or to the cutter, a lead in
advance of the others rotary motion, substantially as described.
3. A machine for carrying out the method of cutting worm wheels referred
to in the first and second claims, wherein the helical motion of the worn cutter
relatively to the wheel blank is produced by the combination of a rectilinear
motion in the axial direction of the wheel blank with a differential rotary motion
thereof, such, that on the rotation of the screw spindle that effects the rectilinear
advance of the cutter towards the wheel blank, the cutter at the same time has
the required acceleration or retardation of its rotary motion imparted to it by
means of differential gear such as i kno, substantially as described.
4. In a machine for cutting worm wheels such as is referred to in the third
claim, imparting the motion to the worm cutter from the differential gear in
every position of the cutter relatively to the wheel blank by means of a shaft which
at the same time serves as the axis for the adjustment of the oblique position
of the cutter relatively to the wheel blank, substantially as described.
Dated this Brd day of April 1900.
ABEL & IMRAY,
Agents for the Applicant.