IMPROVE- MENTS IN SCREW OR WORM GEARING FOR TRANSMITTING OR MODIFYING MOTION
Year: 1876

page_text: LETTERS PATENT to Charles Gittens Hawkins, of Number Three, Allendale
Road, Denmark Hill, in the County of Surrey, for the Invention of "IMPROVE-
MENTS IN SCREW OR WORM GEARING FOR TRANSMITTING OR MODIFYING
MOTION."
Sealed the 23rd March 1877, and dated the 3rd October 1876.
PROVISIONAL SPECIFICATION left by the said Charles Gittens Hawkins at
the Office of the Commissioners of Patents on the 3rd October 1876.
CHARLES GITTENS HAWKINS, of Number Three, Allendale Road, Denmark Hill,
in the County of Surrey. "IMPROVEMENTS IN SCREW OR WORM GEARING FOR
TRANSMITTING OR MODIFYING MOTION."
The object of my Invention is to diminish the amount of friction which
accompanies the use of ordinary worms and worm wheels, and in carrying the same
into effect I employ either a straight or parallel screw, that is, one in which the
threads are of equal diameter throughout its length; or else I employ a spiral worm,
that is, one in which the threads are not of equal diameter throughout, but increase
in diameter each way from the centre of its length or about the centre of its length
outwardly.
Parallel screws are most applicable to those arrangements of my Invention where
rectilinear motions are produced from circular motions of the driver, and spiral
worms are applied when a circular motion is given by the driver and imparted
to the driven wheel The threads of a spiral worm instead of gearing into teeth
like those of ordinary worm wheels actuate a series of rollers turning upon studs,
which studs are attached to a wheel whose axis is not parallel to that of the worm,
but placed at a suitable inclination thereto. When motion is given to the worm
then rotation produced in the roller wheel at a rate proportionable to the pitch
of worm and diameter of wheel respectively.
In the arrangement of my Invention for transmitting rectilinear motion from a
screw, rollers may be employed whose axes are inclined to the axis of the driving

page_text: screw, or else at right angles to or parallel to the same.
When separate rollers are
employed with inclined axes or axes at right angles with that of the main driving
screw each thread in gear touches a roller at one part only; but when rollers are
employed with axes parallel to that of the driving screw a succession of grooves are
turned in these rollers, into which the threads of the driving screw will be in gear
throughout the entire length of the roller. These grooves may be separate and
apart from each other, or else form a screw whose pitch is equal to that of the
driving screw or some multiple thereof. When two or more (of the latter arrange-
ment of) rollers are employed they may be connected together by gearing if
desired.
By suitable adjustment of pitch that which has hitherto been called the driving
screw may be driven by the rollers.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles Gittens Hawkins in the Great Seal Patent Office on the
28th March 1877.
CHARLES GITTENS HAWKINS, of Number Three, Allendale Road, Denmark Hill,
in the County of Surrey. "IMPROVEMENTS IN SCREW OR WORM GEARING FOR
TRANSMITTING OR MODIFYING MOTION."
My said. Invention consists of improvements in transmitting or modifying motion
by means of screw or worm gearing, and in carrying the same into effect I employ
either a straight or parallel screw, that is, one in which the threads are of equal
diameter throughout its length; or else I employ a spiral worm, that is, one in
which the threads are not of equal diameter throughout, but increase in diameter
each way from the centre of its length or about the centre of its length out-
wardly.
Parallel screws are most applicable to those arrangements of my Invention when
rectilinear motions are produced from circular motions of the driver, and spiral
worms are applied when a circular motion is given by the driver and imparted to
the driven wheel. The threads of a spiral worm instead of gearing into teeth like
those of an ordinary worm wheel actuate a series of rollers turning upon studs,
which studs are attached to a wheel whose axis is not parallel to that of the worm,
but placed at a suitable inclination thereto. When motion is given to the worm
then rotation is produced in the roller wheel at a rate proportionable to the pitch of
worm and diameter of wheel respectively.
In the arrangement of my Invention for transmitting rectilinear motion from a
screw roller may be employed whose axes are inclined to the axis of the driving
screw, or else at right angles to or parallel to the same. When separate rollers are
employed with inclined axes or axes at right angles with that of the main driving
screw each thread in gear touches a roller at one part only; but when rollers are
employed with axes parallel to that of the driving screw a succession of grooves are
turned in these rollers, into which the threads of the driving screw will be in gear
throughout the entire length of the roller. These grooves may be separate and
apart from each other, or else form a screw whose pitch is equal to that of the
driving screw or some multiple thereof. When two or more (of the latter arrange-
ment of) rollers are employed they may be connected together by gearing if
desired.
By suitable adjustment of pitch that which has hitherto been called the driving
screw may be driven by the rollers.
In order that iny said Invention may be fully understood I shall now proceed
more particularly to describe the same, and for that purpose shall refer to the several
Figures on the Drawings hereunto annexed.

page_text: Figs. 1 & 2 show an arrangement for transmitting circular motion in either
direction. Fig. 1 is a plan, where A is the spiral worm made of such a length that
the edge of one roller does not cease contact until the edge of the next comes into
contact, and B is a wheel carrying rollers C, C, which turn on studs D, D, the latter
being attached to B by cottars; the axis of A is at right angles with that of B.
The edges of the rollers C, C, come near together, leaving sufficient space for the
thread of the worm to fit between any two contiguous rollers. The pitch line of
the screw thread forms an arc of a circle, whose centre coincides with that of the
wheel B, therefore the thread will always bear fairly against the rollers and
maintain rolling contact therewith during the whole of the time each roller
is in gear, and by turning A in either direction the wheel B will rotate. Fig. 2
is a section through the wheel B, showing the studs D cottared in.
Figs. 3 & 4 show an arrangement for transmitting circular motion in one
direction only, as indicated by the arrow. Fig. 3 is a plan and Fig. 4 a section
through the wheel B; the axes maintain the same relative position to each
other as Figs. 1 & 2. In this case the edges of adjacent rollers C, C, do not come
together, but overlap each other, the studs D, D, not being set radially in the
wheel B. The shape of the spiral screw A. is determined in the same way as for
Fig. 1, and the length I make sufficient to ensure each succeeding roller coming into
action before the preceeding one has gone out.
Figs. 5 & 6 show an arrangement for transmitting rectilinear motion from
circular motion, Fig. 5 being a plan and Fig. 6 a side elevation partly in section.
A is a parallel screw which can pass through the box B. The latter is fitted with
rollers C, C, at intervals along its length; these rollers are inclined to A at an angle
here shown as 45°, and they turn on pins D, D. On turning the screw A in one
direction it will rise through the box B; when turned in the contrary direction it
will fall, its own weight keeping the thread against the rollers.
Figs. 7 & 8 show a plan and elevation of a modification of the arrangement
shown in Fig. 1 for obtaining a partially circular motion, and at the same time a
gradually augmenting force from an uniformly applied power. A is a portion of a
spiral worm, the thread of which gradually diminishes in pitch towards the smaller
end of the worm; B, B, is a forked lever carrying two rollers C, C, which gear with
the worm thread, as in the first illustration. In ordinary worm and toothed wheel
gearing the rate of motion given by the worm is unvarying, but by making the
rollers bear upon the thread in the manner shown, namely, on opposite sides, I can
vary the pitch as desired. If the worm A be turned in the direction of the arrow
and the rollers are in contact at the large end of the worm the lever B, B, will
move upwards with a speed that gradually decreases to a minimum when the rollers
have arrived at the other end of the worm, but the power will increase in an inverse
ratio. Instead of the forked lever B, B, with two rollers I may use a lever B¹, as
shown by dotted lines, with only one roller C¹, the axis of the latter being set at
about right angles to the thread. The greater pitch being on the larger part and
the lesser pitch on the smaller part of the worm the inclination of the thread can be
equal all along, although the pitch varies.
Figs. 9 & 10 show another arrangement for obtaining rectilinear from circular
motion. Fig. 9 is a side view with the end plates D in section, Fig. 10 being an
end view with one of the plates D removed; E, E, E, are bolts tieing the end plates
together. The parallel screw A has placed round it a number of rollers C, C, C ; I
prefer three, whose axes are parallel to that of the screw. Upon the rollers are
grooves corresponding to the screw thread, in which the said thread works or gears
by rolling contact. These grooves may be separate from each other or form a screw
thread along the whole length of the roller, the pitch corresponding to that of A or
some multiple thereof. When A is turned its thread rolls in the grooves of the
rollers C, C, C, and the screw advances or recedes, according to the direction in
which it is turned. If I wish to obtain a greater advance of A than is due to its
pitch I make a thread on the rollers the same hand as that on the screw, that is to

page_text: Bay, if the thread on A be right-handed then that on C, C, C, will be right-handed
also; but when the object is to obtain great power I make the thread on C, C, C,
the contrary hand to that on A, then the advance of A will be determined by the
contrary-handed threads counteracting each other, and by the relative diameters of
the screw and rollers respectively. C, C, C, can also be geared to A with toothed
gearing when desired. In each case the screw A is supposed to receive the driving
power, but by suitable adjustment of the pitch of the screw the power may be
applied through that part of the mechanism which carries the rollers.
Figs. 11 to 23 inclusive on the second Sheet show methods by which my improved
worm gearing may be applied to various machines and apparatus.
Fig. 11 is a back view and Fig. 12 a side view of a crane; the arrangement
shewn in Figs. 1 & 2 is here applied; A is the worm; B, the wheel fitted with
rollers C, C; the axis of B is shown inclined at right angles to the jib; D is the
chain barrel attached to B by a clutch.
Fig. 13 is a side view and Fig. 14 a cross section shewing an arrangement similar
to that last described applied to a winch with the worm A driven by steam power.
If Fig. 14 be supposed to be a plan and the spindle forming the axis of B to be
vertical, which might represent a capstan spindle, then the same arrangement would
be complete for driving a steam-power capstan.
Fig. 15 shows a plan and Fig. 16 an elevation of a steering apparatus for ships.
_A, A, shows the spiral worm made in two halves with axes at right angles to each
other;
the larger ends of A, A, are geared together with toothed gearing; B,-B, are.
two arms of a lever forming the tiller, which is firmly keyed to the rudder head X;
C, C, are two rollers gearing with the worm thread, as in Fig. 1; D is the steering
wheel; E, E, the framing upon which the apparatus is fitted: F, F, are two sinall
toothed bevel wheels for working one of the worms from the steering wheel D.
The thread upon A, A, I make to diminish in pitch from the larger to the smaller
ends to compensate for the increased resistance of the water when the rudder is put
over to either side. With the apparatus in the position here shown the rudder is
supposed to be amidships in a line with the axis of D. The axes of A, A, may be
fixed to the framing E, E, and A, A, turning loose upon them, or else A, A, may be
keyed to the axes, which turn in bearings on the framing.
Figs. 17, 18, & 19 show the plan illustrated by Figs. 9 & 10 applied to a
punching bear or boiler punch, Fig. 17 being a section showing a parallel
screw A and rollers C, C, C; Fig. 18 is a plan with the cover removed, and Fig. 19
a front elevation.
Fig. 20 is a side elevation and Fig. 21 a front view of a drilling machine driven
with gear, as shown at Figs. 1 & 2. A is the spiral worm; C, C, C, C, the rollers
carried on a wheel, through which the drill spindle can rise and fall as ordinaryly
constructed.
Figs. 22 & 23 show a punching and shearing machine, Fig. 22 being a side eleva-
tion and Fig. 23 a cross section. A, B, & C represent as formerly the worm, the
wheel, and the rollers. The axis of B is the shaft D, which has upon each end a
small crank working in a block E, which slides in a slot cut across the slide plate F,
the length of the slot being sufficient to allow E to move from side to side in F as D
revolves, and F rises and falls to work the punch on one side and shears on the
other.
Having now described and particularly ascertained the nature of my said In-
vention, and the manner in which the same is or may be used or carried into
effect, I would have it understood that I do not limit myself to the number of
rollers, form of thread, or other details shown by the Drawings, as these may be
modified according to circumstances, but I declare that the improvements which I
claim as comprehended in my said Invention are as follows:-
1st. The application of rollers for the threads of worms or screws to work against
instead of rubbing against teeth of a wheel or rack a nut for transmitting motion,
substantially as herein-before described.

page_text: 2nd. The arrangement of varying the pitches of threads on spiral worms, sub-
stantially as herein-before described.
3rd. The application of these improvements to cranes, stearing apparatus, and
other machinery.
In witness whereof, I, the said Charles Gittens Hawkins, have hereunto set
my hand and seal, this Twenty-eighth day of March, in the year of our
Lord 1877.
CHARLES GITTENS HAWKINS. (LS.)