An Improved Method of and Apparatus for Cutting Worm-wheels.
Year: 1887

page_text: COMPLETE SPECIFICATION.
An Improved Method of and Apparatus for Cutting Worm-wheels.
I, JOHAN ADOLF NORDSTEDT, of Sundbyberg, in the Kingdom of Sweden,
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:-
The method hitherto adopted of cutting worm-wheels with curved teeth is very
slow and expensive and the teeth at best are not accurately cut especially when the
pitch of the driving screw is large in comparison with its diameter, in fact, for very
large pitches it has hitherto been impossible to cut them at all. Straight teeth have
therefore generally been used because they could be easily cut in an ordinary wheel
cutting machine but their shape has of course been very far from correct. By the
method herein described, curved teeth, of any required pitch, can easily and quickly
be cut exactly and theoretically true.
In the accompanying drawing figure 1 is a front elevation, figure 2 a side
elevation and figure 3 a plan of an apparatus suitable for cutting worm-wheels
according to my invention.
A, is the wheel to be cut, B, is a spindle on which is fixed a cutter C, having the
same shape as a cross section of the thread of the scrow intended to drive the wheel
to be cut. On the spindle B, at D, there is a screw-thread cut of the same pitch as
the intended driving screw. This screw thread acts upon a worm-wheel E, fixed
upon a shaft, at the other end of which is fixed the pinion F, that operates the
wheel G. This wheel is fixed on the same shaft as the worm-wheel A, to be cut, and
the number of teeth in the pinion F and wheel G, are so proportioned that when the
spindle B, is rotated the velocity in the pitch line of the wheel A will be equal to
the velocity in the pitch line of the wheel E.
The cutting of the teeth is performed in the following manner :-
The spindle B, is rotated by the pulley H, and is moved forward in the direction of
its axis by means of the screw I, sufficiently far to cause the cutter C, to touch the
wheel A. The cutting now commences and for every revolution of the wheel A,
the spindle B, is fed forward in the direction of its axis giving a suitable feed to the

page_text: cutter ; this is continued until the cutter has reached the point K when the tooth
cutting operation is completed.
By the mechanical arrangement above described and illustrated in figures 1, 2 and 3
of the accompanying drawings it is only possible to cut worm-wheels with the same
pitch as the screw thread on the spindle B, but by means of the arrangement shewn
in figures 4, 5 and 6, wheels can be cut with a pitch different from that of the screw
thread on the spindle B. As shewn by the drawings the cutter C is in this case fixed
in a separate spindle L, rotated by the spindle B, by means of a wheel and a pinion N
and M, and both these spindles have their bearings in the same bracket O, on a
slide P. The feed motion is obtained by the screw I, acting upon the slide P, when
the spindles B, and L, will be simultaneously and equally fed forward in the direction
of their axes.
In order to cut the wheel A with a pitch of teeth different from that of the screw
thread D on the spindle B, it is evident that this can be effected by varying the
proportion between the number of teeth of the wheel N and of the pinion M. For
example if the pitch of the teeth of the wheel A is required to be double that of the
screw thread D, the number of teeth of the pinion M and wheel N, must be as 1 to 2,
and so on.
To cut worm-wheels of different diameters it is only necessary to place the bearings
of the shaft on which the wheel to be operated on is fastened on a slide by which it
can be moved towards or from the spindle L, and to employ a set of change wheels
from which suitable wheels F and G, can be selected, so that the velocity in the pitch
lines of the wheels E and A will be equal.
The wheels R and S as will be easily understood are only required to bring the
motion in the right directions.
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 described method of cutting worm-wheels in which the cutter or cutting
tool is placed in or affixed to a rotating spindle which spindle during the cutting
operation is fed forward in the direction of its axis and the wheel to be cut is
simultaneously rotated.
2. The improved apparatus for cutting worm-wheels hereinbefore described and
illustrated respectively in figures 1 to 3 and figures 4 to 6 of the accompanying
drawings.
G. F. REDFERN,
4, South Street, Finsbury, London,
Agent for the Applicant.