Improvements in Machines for Cutting the Teeth of Helical or Worm Gearing.
Year: 1897

page_text: Date of Application, 17th May, 1897
Complete Specification Left, 11th Feb., 1898-Accepted, 9th Apr., 1898
Date of Application, 17th May, 1897
Complete Specification Left, 11th Feb., 1898-Accepted, 9th Apr., 1898
PROVISIONAL SPECIFICATION.
Improvements in Machines for Cutting the Teeth of Helical or Worm
Gearing.
EDWARD GEORGE FIEGEHEN, Stafford Lodge, Ampthill Road, Bedford, Mechanical
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in machines for cutting the teeth of
wheels for helical or worm gearing wherein the cutting is effected (except in the
case of multiple-thread gears) by a single cutter which being rotated in a definite
ratio to the rotation of the worm wheel blank produces the correct form of tooth.
In machines of this description the cutter is fed into the wheel-blank by being.
traversed across a chord of the addendum circle.
During this traverse of the cutter it is necessary to give this cutter apart from
its primary rotation in the definite ratio aforesaid, a secondary rotation as well
as the rectilinear one for effecting the traverse; so that, assuming the wheel-blank
to be stationary, the cutter should describe a helical path identical with the form
of thread of the worm with which the wheel blank, when finished, is to gear.
In machines of this description, the wheel blank is secured to a face plate,
which is driven by worm reduction gear suitably connected to the cutter bar by
means of a train of gearing to give the desired ratio.
Now it is required that the cutter should fall into the same space in the wheel
blank under operation whatever it's (the cutter's) position upon the chord of the
addendum circle.
For the purpose of describing this, the cutter and the wheel blank may be con-
sidered as a toothed rack and wheel, and it is evident, that if as the cutter traverses
the chord the space in the wheel blank could be kept constantly in gear with it,
as in the case of the adjacent teeth of a rack and its engaging wheel, the above
conditions would be satisfied.
Again, the driving worm and wheel for rotating the face plate aforesaid can
also be considered as a rack and wheel, and an axial motion of the worm will
cause a rotary motion of the wheel.
For the purpose of illustration, we will assume that the pitch diameters of
the wheel blank and the driving worm wheel are identical.
It is evident, that the rectilinear motion of the driving worm as well as that
of the cutter for a given angular displacement of the driving worm-wheel and
the wheel blank would be equal in amount; consequently, if the cutter holder
and driving worm were free to slide axially, and were coupled together so that
the cutter was constrained to move at the same rate as the driving worm, the
cutter and wheel blank would move with respect to one another so as to keep.
the cutter always in the same space in the wheel blank, or in other words the
two would gear correctly as a rack and wheel.
In the case where the diameter of the wheel blank differs from that of the
driving worm wheel, the driving worm and the cutter must be geared together so.

page_text: as to make their respective axial motions directly proportionate to the diameters
of the driving worm wheel and the wheel blank.
Thus, in the case where the wheel blank is of twice the pitch diameter of the
driving worm wheel, the axial displacements of the cutter and driving worm
would require to be as 2 is to 1.
In my improvements I regulate the relative axial motions of the driving worm
and cutter as follows:-
I provide sliding carriages for both the cutter head and the driving worm,
(the latter being of suitable length) and impart axial motion thereto by means of
suitable leading screws and nuts.
By means of suitable change gearing I am enabled to give any desired velocity
ratio of rotation to their respective leading screws, and consequently any required
ratio between the axial displacements of the driving worm and the cutter.
I also provide suitable reversing gear for the purpose of cutting either right or
left handed gearing.
Dated this 10th day of May 1897:
Improvements in Machines for Cutting the Teeth of Helical or Worm
Gearing.
EDWARD GEORGE FIEGEHIEN, Stafford Lodge, Ampthill Road, Bedford, 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 relates to improvements in machines for cutting the teeth of
wheels for helical or worm gearing wherein the cutting is effected (except in the
case of multiple thread gears) by a single cutter which, being rotated in a definite
ratio to the rotation of the worm wheel blank, produces the correct form of tooth.
In machines of this description the cutter is fed into the wheel. blank by being
traversed across a chord of the addendum circle; during this traverse of the
cutter it is necessary to give it, apart from its primary rotation in the definite
ratio aforesaid, a secondary rotation as well as the rectilinear one for effecting
the traverse, so that, assuming the wheel blank to be stationary, the cutter should
describe a helical path identical with the form of thread of the worm with which
the wheel blank, when finished, is to gear.
In machines of this description the wheel blank is secured to a face plate which
is driven by worm reduction gear suitably connected to the cutter bar by means
of a train of gearing to give the desired ratio. Now, it is required that the
cutter should fall into the same space in the wheel blank under operation what-
ever it's (the cutter's) position upon the chord of the addendum circle. For the
purpose of describing this, the cutter and the wheel blank may be considered as
a toothed rack and wheel, and it is evident that if as the cutter traverses the
chord the space in the wheel blank could be kept constantly in gear with it, as
in the case of the adjacent teeth of a rack and its engaging wheel, the above
conditions would be satisfied. Again; the driving worm and wheel for rotating
the face plate aforesaid can also be considered as a rack and wheel and an axial
motion of the worm will cause a rotary motion of the wheel.
-
For the purpose of illustration, we will assume that the pitch diameters of the
wheel blank and the driving worm. wheel are identical. It is evident that the

page_text: rectilinear motion of the driving worm as well as that of the cutter for a given
angular displacement of the driving worm-wheel and the wheel blank would be
equal in amount; consequently, if the cutter holder and driving worm were free
to slide axially and were coupled together so that the cutter was constrained to
move at the same rate as the driving worm, the cutter and wheel blank would
move with respect to one another so as to keep the cutter always in the same space
in the wheel blank, or, in other words, the two would gear correctly as a rack
and wheel.
In the case where the diameter of the wheel blank differs from that of the
driving worm wheel the driving worm and the cutter must be geared together
so as to make their respective axial motions directly proportionate to the
diameters of the driving worm wheel and the wheel blank. Thus, in the case
where the wheel blank is of twice the pitch diameter of the driving worm wheel,
the axial displacements of the cutter and driving worm would require to be. as
2 is to 1.
In my improvements I regulate the relative axial motions of the driving worry.
and cutter as follows:-I provide sliding carriages for both the cutter head and
the driving worm (the latter being of suitable length) and impart axial motion
thereto by means of suitable leading screws and nuts.
By means of suitable change gearing I am enabled to give any desired velocity
ratio of rotation to their respective leading screws and consequently any required
ratio between the axial displacements of the driving worm and the cutter.
I also provide suitable reversing gear for the purpose of cutting either right or
left handed gearing.
In the accompanying drawings which illustrate my invention Fig. 1 is an
elevation of the complete machine, Fig. 2 is an end elevation from the headstock
end, Fig. 3 is an end elevation from the operating end, and Fig. 4 is a plan of
the whole machine. Fig. 5 being a vertical section through the face plate and
driving worm gear. Fig. 6 a vertical section through the driving worm with
its carriage, guide and leading screw.
Throughout the drawings the same parts are indicated by the same reference
figures.
The machine consists of a cutter head A containing one or more suitable
cutters B revolved by a shaft C which has a keyway. its whole length for the
reception of a feather fixed in the cutter head A which permits of the cutter head
being fixed at any convenient position along the shaft C. This shaft C runs in
suitable bearings 1) on the sliding carriage E which can be moved along the
bed F by means of a suitable leading screw G. An ordinary lathe headstock H
is provided having a hollow spindle through which the shaft C can slide freely
the rotary motion being communicated thereto by means of a suitable feather
or feathers. A face plate I upon which to bolt the wheel blank to be operated
upon is provided and is suitably secured to a vertical spindle J running in a boss
in the carriage K which is capable of being fixed in any position along the ways L
at right angles to the ways upon which the carriage E slides. The spindle J
has secured to it a worm wheel M driven by a worm N of extra length having
thrust bearings O in the carriage P the whole being made to slide in the guide Q
by means of the leading screw R running in the nut S fixed to the worm carriage P.
The worm N is driven by a shaft T connected to a shaft U by means
of bevel or mitre gears V (the shaft T having a feather of sufficient length to
permit the traverse of the worm N). The shaft U is connected to the spindle of
the headstock H by means of change wheels W and suitable reversing wheels X:
as in an ordinary lathe for screw cutting, the shaft U taking the place of the
leading screw. The leading screw R for moving the worm carriage P is coupled
in a similar manner by means of mitre or bevel wheels Y to a shaft Z this shaft.
being in turn coupled to the leading screw G in any desired ratio by means of
suitable change wheels.

page_text: The operation is as follows:-
The wheel blank to be cut having been secured to the face plate I the latter is
moved along the ways L until the distance of its centre from the centre of the
shaft C is that at which the finished worm and wheel are to gear.
The worm
shaft T is next coupled to the spindle of the headstock H by means of suitable
change wheels W so that the ratio between the speed of the face plate I and that
of the cutter head A is the same as that of the finished worm and wheel, the
reversing wheels X being adjusted for cutting either a right or left handed wheel
as the case may be. The leading screw G is next geared to the shaft Z in a
suitable manner by means of change wheels so that the ratio of its speed to that
of the shaft (the pitches of the leading screws G and R being for illustration
assumed as identical and the gear at Y being mitre) is the same as the ratio of
the pitch diameter of the wheel to be cut to that of the driving worm wheel M
which latter for convenience is made an even number. A suitable feed gear is
employed for rotating the leading screw G and consequently the leading screw P
once eacli revolution of the face plate I thus giving the desired feed of the cutter B
across the addendum circle of the wheel to be cut.
By the aforesaid means I am enabled to impart to the cutter B with respect
to the wheel blank to be cut the relative motions of a rack and wheel so that
the traversing of the cutter across the addendum circle is accompanied by a com-
pensating movement caused by the sliding of the worm N either in advance or
behind its normal motion thus enabling the cutter to fall into the correct track
at each revolution of the wheel blank whatever its position along the chord of
the addendum circle may be.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed I declare that I claim as
my invention of "Improvements in Machines for Cutting the Teeth of Helical or
Worm Gearing":
First. The means as herein before described and illustrated of effecting the
helical adjustment of a traversing worm wheel cutter by the use of a sliding
driving worm connected to the aforesaid cutter by means of suitable ratio gearing.
Secondly. The arrangement and combination of parts constituting a worm or
helical wheel cutting machine as herein before described and illustrated wherein
the helical adjustment of the cutter is effected by means of a sliding driving worm
coupled to the cutter head in any ratio desired by means of a leading screw and
change gearing.
Thirdly. The use and application of a sliding driving worm of suitable length
for effecting the necessary angular advance or retreat of the worm wheel blank
in worm or helical wheel cutting machines.
Dated the 9th day of February 1898.