Improvements in Clutches and Friction Brakes.
Year: 1896

page_text: Date of Application, 6th Mar., 1896-Accepted, 25th Apr., 1896
COMPLETE SPECIFICATION..
Improvements in Clutches and Friction Brakes.
1. FREDERICK HARRY ELLIOTT, of Electric Station Cottage, Aberystwyth,
in the County of Cardigan, 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 has reference to the improved arrangement and combination of
friction clutch and brake to be used upon shafts subjected to axial pressure, the
object of the invention being to produce a combination which will permit of the
shaft rotating in one direction with a minimum friction, but which, when rotated
in the opposite direction, rotates against the retarding frictional action set up by
the brake.
My invention also enables me to dispense with ratchets and pawls used in
connection with such appliances, when combined for the purpose of a sustaining
brake with the worm, screw, or other shaft.
In the accompanying sheet of explanatory drawings,
Figure 1 is an elevation partly in section showing one method of making my
combination upon a worm shaft and its end bearing.
Figure 2 is a sectional end elevation showing one form of clutch.
:
Figure 3 is a similar elevation showing a modified form of clutch which I
employ.
Figures 4 and 5 are end elevations showing the brake segments, and end frame
or bearing.
Figures 6, 7, and 8 are views showing the modifications of my braking devices.
Figures 9, 10 and 11 are similar views to Figures 1,5 and 4, but with a modified
system of segments.
Figures 12, 13 and 14 show elevations and details of the form of clutch and
brake I sometimes employ, in which a slipping jaw or incline face clutch is
employed, which slips in one direction over the teeth or projections on or affixed to
the brake box.
In carrying my invention into effect when constructing a brake box and clutch
shown in Figures 1, 2, 3, 4, and 5, I mount upon the worm shaft A a bush J,
having cam-like or inclined surfaces J' formed upon it, which work into similarly
shaped spiral beds formed in the segments L, L, so that when the shaft is rotated
in the direction of the arrows, as the load is being lifted, there is no forcing out of
the segments L L, as they revolve as in one piece with the bush J being carried
round by the shoulders of the cam faces J'; but when the shaft is rotated in the
opposite direction, as when the load is to be sustained, or when it is to be lowered, the
segments L L are forced apart by means of the spiral projections J¹ moving in
the reverse direction, so that the outer surfaces of the segments L L press against
the inner surfaces b of the brake box B, causing the said box to rotate with the
shaft A.
I form the brake box B in one manner with a sleeve or bearing axis which
revolves in a fixed portion P of the frame of the pulley block, or inachine, and
within the bush I place a cap or plug C with convex face, for the end of the
shaft a to thrust against. Upon the frame P I form a cone or tapered bearing
surface F, which engages with or receives segments E carried within the brake
box B, and within the same inner end of the brake box B I introduce friction
discs, of rubber, leather metal, or other suitable material D.

page_text: I prevent the conical friction segment pieces E from rotating with the box by
means of lugs or projections ! I upon the conical segment pieces and recesses G, G,
formed upon the frame.
The action of my improved apparatus is as follows.-When the worm shaft is
turned in one direction, the thrust being always practically constant in whichever
direction it is being rotated, the axial pressure is received by the block cap C, but
this pressure is not sufficient to rotate the box B when the worm shaft is rotating
in one direction. When, however, the motion is reversed, the segments L L are
forced outwards and made to seize or press with more or less force, upon the
interior b, of the brake box B depending upon the inclination of the cams and the
load which may be put upon the shaft, and the expanded segments L L pressing
against the interior b of the box carries round the box B against the friction set
up on the frictional surfaces E and D within the other end of the box. Thus,
when it is desired to raise a load there is a minimum of friction due to the clutch
slipping round freely, but when it is desired to sustain the load, the friction is
brought into play owing to the segments L L being pressed outwards and the box B
being made practically in one with the shaft A.
In the modified arrangements shown in Figures 6, 7, 8, 9, 10 and 11, I force
outwards the friction segments E by means of conical or wedge pieces F formed
upon the frame P employing the same cam action clutch in the other end of the,
box B as hereinbefore described with reference to Figure 1.
In Figures 12, 13 and 14 I employ the same constant friction box B, but instead
of a slipping clutch with cam like surfaces J' as bereinbefore described, I make a
clutch box M N, which only drives in the one direction, a spring O being employed
to keep the teeth in contact.
By this improved combination of parts I utilize a constant frictional pressure
which is set up within a brake box B, and I cause the brake box to remain
stationary and inoperative when the shaft is turned in one direction, by means of a
slipping clutch allowing the shaft to freely rotate within the bearing of the brake
box B, whilst when the shaft is turned in the opposite direction, the cam J and
segments L L seize the brake box B, and carry the whole round as one piece with
the shaft A. I key the bush J to the shaft A by a key K, or I may form it in
one piece therewith when so desired. Similarly I attach a cone or projecting
conical wedges.to the frame P independently, or I form them in one with the same.
I sometimes arrange my cams so that the inclination will be such as to permit of
slipping within the brake box, and thus when a certain load or a certain pressure
for which the machine is safe is exceeded, the apparatus will, by its slipping, warn
the operator or workman that an excessive load or an excessive pressure has been
put upon the machine...
In other cases, when I desire to have a complete seizure and a dead lock between
the clutch surfaces, I make the inclination of the cam and the cam path such that
one part is locked to the other when the reverse motion is given to the shaft.
I do not limit the application of my invention to any particular form of pulley
block, screw or worm block, press or other device, but I modify the essential
features hereinbefore described to suit the shaft which is subjected to axial pressure,
and the work and condition to which such shaft is to be employed.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performned, I declare that what I
claim is :-
1. The improvements in combination of friction clutched and retarding or
sustaining brake devices, in which one part is free to rotate in one direction with a
minimum of friction, but to rotate in the opposite direction with a maximum
of friction substantially as hereinbefore described and as illustrated in the
accompanying drawings.
2. An automatic brake arrangement in which a box or casing is employed,
Láving on the one side a slipping friction clutch which is free to revolve within, it

page_text: in one direction, but which engages with it when rotated in the opposite direction,
and having at the opposite side segments or friction discs or rings for forming a
brake, substantially as hereinbefore described and as illustrated in the accompanying
drawings.
3. The combination and arrangement of a worm shaft or screw shaft having at
its end a brake box which is held without the intervention of ratchets or pawls
substantially as and for the purposes hereinbefore described.
Dated this 5th day of March 1896.
FREDERICK HARRY ELLIOTT,
Electric Station Cottage, Aberystwyth.