Improvements in Gear Cutting Machines.
Year: 1897

page_text: Date of Application, 31st May, 1897
Complete Specification Left, 28th Feb., 1898-Accepted. 28th May, 1898
Improvements in Gear Cutting Machines.
I, FREDERICK WILLIAM LANCHESTER, of Cobley Hill, near Alvechurch, in the
County of Worcester, Engineer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to improvements in machines for cutting worm gear and
has for its object the construction of a machine in which the teeth of both worm
and worm wheel may be cut in an accurate manner and so that the teeth shall be
of such form as will give a large wearing surface and high working efficiency.
In constructing a machine in accordance with the present invention I arrange
a bed plate of trough form which is accurately planed on the outside or walls of
the trough and the said walls of the trough are bored right through in two places
at right angles to the planed faces, these holes are bushed and (calling one end
of the trough the front and the other end the rear of the machine) the rear bushes
are arranged to project into the trough and form pivots for an upper casting which
carries a bearing at right angles to said pivots in which rotates the working man-
dril of the machine. The front end of this mandril carries a face plate for the
attachment of a cutting head or a worm wheel blank the other end is keyed fast
to a worm wheel which gears into and is driven by a worm shaft running in the
aforesaid rear bushes of the machine. On one end of this worm shaft is keyed
the driving pulley and on the other end is feathered the first of a series of change
wheels arranged to drive a shaft working in the front bushes to which the wormi
blank is keyed.
The relative positions of the face plate and worm blank are so arranged as to.
permit of the worm wheel blank or tool head as the case may be, being fixed in
the proper position for cutting the teeth and the feed is applied by rotating the
upper casting about its pivots either by a positive action feed motion or by a
permissive feed actuated by a load.
The driving worm gear is preferably made of fine pitch so as to minimise the
differential motion introduced by the rotational feed mechanism.
In gearing cut with a machine constructed as herein before described it will
be understood that the worm is curved forming a saddle to fit with the worm
wheel.

page_text: I, FREDERICK WILLIAM LANCHESTER, of Cobley Hill, near Alvechurch, in the
County of Worcester, 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 worm gear and
has for its object the construction of a machine in which the teeth of both worm
and worm whicel may be cut in an accurate manner and so that tho teeth shall be
of such form as will give a large wearing surface and high working efficiency.
The invention consists generally in providing a standard worm and worn whee]
to simultaneously feed or govern the cutting tool and the blank to be operated
upon the said standard worm operating through suitable change wheels the
required worm blank according to the pitch desired while the standard worm
wheel actuates the tool holder, or the positions of the tool holder and blank may
be reversed when a worm wheel is required. Further the whole mechanism is
arranged in a simple and novel manner upon a trough shaped bed plate with the
standard worm wheel and its shaft revolving on a bracket pivotted at right angles
to the standard worm and remaining in gear as the feed carries this bracket
radially downwards.
The mode of carrying this invention into effect is illustrated in the accom-
panying sheet of drawings as follows : -
-
Figure 1 is an elevation taken from the right hand of Figure 2 with one half
the machine in section on the lines A, B.
Figure 2 is a sectional elevation taken from the left hand of Figure 1 ou the
line C, D.
A bed plate of trough form E is provided accurately planed on its outside walls
and arranged with two shafts F and G at right angles thereto. A pair of bushes H
are fitted within the walls of the trough and form bearings for the shaft F, and
also at their inner portions h form a pivot upon which the large bracket I can
partially rotate. The bracket I is bored at right angles to the shaft F forming
a bearing for the mandril J which has keyed upon it at one end the standard worm
wheel K and upon the other end a face plate L for carrying the tool holder M
when a worm is being shaped as in the present instance, or a worm wheel blank
when a worm wheel is required. The shaft F has keyed upon it the standard
worm N and this worm is always in gear with the standard worm wheel K as in
any radial position of the bracket I the centres of N and K remain unaltered.
The shaft G is mounted in suitable bearings in the walls of the trough and it is
driven at any required speed by suitable change wheel gearing O, P, Q, and R
from the standard worm shaft F, this shaft being driven by the belt pulley S in
the usual manner. The shaft G carries upon it the worm blank to be cut when
that is required or the tool holder when a worm wheel blank is carried upon the
face plate L. A screwed feed spindle T passes through a side bracket U formed
upon one side of the large bracket I and a permissive feed of the cutting tools in
the tool holder can take place downwards by means of the weights V when the
spindle T is rotated.
The operation of the mechanism hereinbefore described with reference to the
cutting of a worm is as follows. The worm blank is threaded upon the shaft G
and secured thereon, and suitable tools W are gripped in the holder M, the said
tools being formed with their cutting edges to givo the required shape of tooth.
An appropriate set of change wheels O, P, Q, R, to produce the desired pitch
having been placed in situ the feed is applied by slacking off the feed screw T.

page_text: The large bracket I being loaded by the dead weight V the slacking of the screw
allows the tool holder to travel downwards producing a permissive feed. The
rotation of the shaft F by its pulley S revolves the standard worm N, worm
wheel K and tool holder M, and also through the change wheels herein before
referred to operates the worm blank and thus cut the desired worm.
The process for producing a worm wheel is the converse of this, the tool holder
being fixed upon the shaft G and the worm wheel blank upon the face plate L.
It is to be understood that a positive feed instead of the permissive feed described
may be employed and that the main drive pulley S may be arranged upon any
of the train of change wheels and all without departing from the subject of the
present invention.
The standard worm and worm wheel should be of very fine pitch to avoid
unnecessary side movement of tool when the feed is supplied and it is evident that
different pairs of these may be employed in the machines according to the kind
of work desired.
Having now particularly described and ascertained the nature of my suid inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:-
(1) In gear cutting machines for forming worm and worm wheels, the provision
of a standard worm upon the main shaft of the machine operating two distinct
trains of gearing; in the first instance driving a standard worm wheel fixed to a
mandril rotating in a bracket which pivots upon the same centre as the main shaft,
the mandril rotating a tool box or a wheel blank; and in the second instance
governing or driving through a train of change wheel gearing a second shaft
which rotates the worm blank or the tool box, all substantially as and for the
purposes herein before described.
(2) The improved gear cutting machine substantially as hereinbefore described
with references to the accompanying drawings.
ለሰ
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MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.