Improvements in Pulley Blocks, Hoists, and similar Lifting Appliances.
Year: 1893

page_text: Date of Application, 8th June, 1893
Complete Specification Left, 8th Mar., 1894-Accepted, 21st Apr., 1894
PROVISIONAL SPECIFICATION.
Improvements in Pulley Blocks, Hoists, and similar Lifting
Appliances.
We, ROWLAND PRIEST, of Pulley Block Works, Cradley Heath, Staffordshire,
Hydraulic and General Engineer, and WILLIAM MORRALL, of 5, Upper Grove
Street, Smethwick, Staffordshire, Fitter, do hereby declare the nature of this
invention to be as follows:-
:-
This invention has reference to all kinds of pulley blocks hoists and similar
lifting appliances in which the lifting power is obtained by worm and worm wheel
and this invention consists of the hereindescribed improved arrangement of
automatic break mechanism to prevent the load running back or lowering itself
such said break mechanism being so arranged that whilst it offers no obstruction to
lifting the load it is instantly automatically applied to sustain the lifted load and
whilst the load is being lowered in the exact proportion to the load so that whether
the load be light or heavy the resistance to the pull of the hand chain by the
person operating the lift or hoist or other lifting appliance will be about the same
in all cases.
We will describe this invention in connection with a pulley block in which one
end of the lifting chain is fixed to a cross bar or other fixed part of the block and
passes around the shaft of the bottom block and then up and through the chain
wheel in the top block this chain wheel being mounted on a worm wheel axle and
turning with the worm wheel which is operated by a
worm mounted upon a
horizontal shaft either above or below the worm wheel.
We arrange
for this worm shaft to have some little end play in its bearing and
when the weight is being lifted the reaction of the worm shaft on the worm forces
the worm shaft endwise against the end pivot or bearing situated at one end of
the worm shaft the hand chain wheel being situated on the other end thereof.
Fixed to or formed with the crossbar or bearing of the worm shaft next to the
hand chain wheel is a cam (which we call the fixed cam) having an inclined plane
upon its face. Fitting between this fixed cam and the hand chain wheel is another
cam which we call the moving cam and which is mounted loosely upon the worm
shaft. One face of this moving cam is inclined to match the fixed cam and the
other face of the moving cam is flat or coned or otherwise formed to present a
frictional surface to a similar face on the hand chain wheel. Between the hand
chain wheel and the moving cam there is or may be a leather or other washer to
increase the friction between them.
When the load is being lifted by turning the band chain wheel the load acting
through the worm and worm wheel forces the worm shaft end wise against the said
end pin or bearing and the moving cam then offers no appreciable resistance to the
turning of the worm shaft. Immediately the hand chain is released the lifted
weight causes the worm wheel to turn the worm and its shaft through a small angle
in the opposite direction the friction between the hand chain wheel and the moving
cam causing the moving cam to turn also and its incline acting upon the inclined
surface of the fixed cam moves the worm shaft end wise away from its end pin or
bearing so that the end thrust of the worm shaft is now taken by the hand wheel
and moving cam and fixed cam and the cross bar of the block the amount of friction
between the hand chain wheel and the moving cam increasing or diminishing in
proportion to the load which is being lifted.
The inclined surface on the said cam may take the form of screw threads or
0

page_text: instead of the inclined surface or screw threads the moving cam may act upon a
lever which moves the worm shaft end wise as above described; or instead of
moving the worm shaft endwise away from its end pin or bearing the end pin or
bearing may by the movement of the moving cam be arranged to move away from
the worm shaft.
There is or may be a spiral or other spring to keep the moving cam in contact
with the surface of the hand chain wheel and there are or may be stops to prevent
the moving cam turning too far.
Dated this 6th day of June 1893.
CHARLES BOSWORTH KETLEY,
Agent for the Applicants.
Improvements in Pulley Blocks, Hoists, and similar Lifting
Appliances.
We, ROWLAND PRIEST, of Pulley Block Works, Cradley Heath, Staffordshire,
Hydraulic and General Engineer, and WILLIAM MORRALL, of 5, Upper Grove
Street, Smethwick, Staffordshire, Fitter, 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 all kinds of pulley blocks hoists and similar
lifting appliances in which the lifting power is obtained by worm and worm wheel
and this invention consists of the herein described improved arrangement of
automatic break mechanism to prevent the load running back or lowering itself
such said break mechanism being so arranged that whilst it offers no obstruction to
lifting the load it is instantly automatically applied to sustain the lifted load and
whilst the load is being lowered in the exact proportion to the load so that whether
the load be light or heavy the resistance to the pull of the hand chain by the person
operating the lift or hoist or other lifting appliance will be about the same in all
cases.
We will describe this invention in connection with a pulley block in which one
end of the lifting chain is fixed to a cross bar or other fixed part of the block and
passes around the sheave of the bottom block and then up and through the chain
wheel in the top block this chain wheel being mounted on a worm wheel axle and
turning with the worm wheel which is operated by a worm mounted upon a
horizontal shaft either above or below the worm wheel.
A pulley block of this kind with our invention applied is illustrated on the
accompanying drawings in sectional elevation by Fig. 1;
Fig. 2 is a front sectional elevation of the same with the hand chain lifting
wheel removed and Fig. 3 is a part sectional plan of the same;
Fig. 4 is a sectional elevation and Fig. 5 is a side elevation of the hand chain
lifting wheel separately on an enlarged scale;
Fig. 6 is a front elevation Fig. 7 is a side elevation and Fig. 8 a back elevation
on an enlarged scale of what we call the moving cam of the said pulley block and
Fig. 9 is a front elevation plan and side elevation of the crossbar and fixed cam
of the said pulley block drawn to the same scale as Figs. 4, 5, 6, 7 and 8; and
Fig. 10 is a modified form of the moving cam and cross bar of the said pulley
block.
The same letters of reference indicate the same or corresponding parts in all the
figures of the drawing.
A is the lifting chain which at one end a¹ is fixed to the crossbar B of the pulley
block and passes round the bottom sheave C and then up and through the chain
wheel D in the top block this chain wheel D being mounted on the worm wheel
axle e and turning with the worm wheel E which is operated by the worm F

page_text: mounted upon a horizonal shaft f' which is arranged to be turned by the endless
hand chain g passing round the hand chain wheel G.
In carrying out our invention we arrange for the worm shaft f¹ to have some.
little end play in its bearings bh' and when the weight is being lifted the re-action
of the worm wheel E on the worm F forces the worm shaft fendwise against
the end pivot or bearing I situated at one end of the worm shaft f' the hand chain.
wheel G being fixed on the other end of the shaft. Fixed to or formed with the
cross bar H in which is the bearing h¹ of the worm shaft next to the hand chain
wheel G is a cam h² (which we call the fixed cam) having an inclined plane upon
its face. This cross bar H with its cam 2 is shewn separately by Fig. 9..
Fitting between this fixed cam 2 and the hand chain wheel G there is
another cam J shewn separately by Figs. 6, 7 and 8 which we call the moving cam
and which is mounted loosely upon the worm shaft f¹. One face marked j¹ of this
moving cam J is inclined to match the fixed cam h² and the other face of the
moving cam J is coned to present a frictional surface to a similar face 92 on the
hand chain wheel G. Or instead of the face j³ of the cam J and the face y of
the hand wheel G being coned these faces may be made flat or otherwise formed so
as to increase the friction between them but the coned sheave shewn upon our
drawings is what we find to answer best in practice.
When the load is being lifted by turning the hand chain wheel G in the direction
shewn by the arrow in Fig. 2 the load on the bottom block acting through the
worm wheel E and worm F forces the worm shaft f' end wise against the end pin
or bearing I and the moving cam J then offers no appreciable resistance to the
turning of the worm shaft because if this cam J is turned slightly in the direction
shewn by the arrow in Fig. 2 the inclined surfaces j¹cause the cam J to recede
or loosen itself from the wheel G. Immediately the hand chain gl is released the
weight_suspended by the bottom block causes the worm wheel E to turn the
worm F and its shaft f' through a small angle in the opposite direction to that
shewn by the arrow in Fig. 2 the friction between the surface 92 of the hand chain
wheel G and the coned surface of the cam J causing the moving cam J to turn
also and then its incline acting upon the inclined surface 12 of the fixed cam
moves the worm shaft "endwise away from its end pin or bearing I so that the
end thrust of the worm shaft f¹ is now taken by the hand wheel G and moving
cam J and fixed cam 2 and the cross bar H of the block the amount of friction
between the hand chain wheel G and the moving cam J being sufficient to sustain
the load and increasing or diminishing in proportion to the load which is being lifted.
There is a spring k fixed to the eye of the cam J and to one of the side
plates of the pulley block which pulls the moving cam J round slightly in the
opposite direction to the arrow shewn by Fig. 2 thus keeping the coned surface
of the moving cam in contact with the surface g of the hand chain wheel G.
There is also a stop on the moving cam J which when the moving cam is turned
through a certain angle in the opposite direction to that shewn by the arrow in
Fig. 2 comes in contact with the stop h³ formed on the cross bar H and thus
prevents the cam J turning too far in that direction. The cam J is prevented
from turning too far in the direction shewn by the arrow in Fig. 2 by the
termination of the incline ¹ coming in contact with the termination * of the
incline h².
.
The inclined surfaces h² and j¹ of the cams may as shewn by Fig. 10 take the form
of screw threads instead of as above described being formed on the faces of the
cams. In this arrangement the screw thread is cut on the outside of a boss
on the moving cam Jengaging in corresponding screw threads h² in a boss * on the
cross bar H.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
In pulley blocks hoists and similar lifting appliances in which the lifting power

page_text: is obtained by a worm and worm wheel, the employment on the worm shaft of the
moving cam constructed with a frictional surface against the hand chain wheel and
an inclined surface or its equivalent against a corresponding surface of the fixed
cross bar or bearing in which the worm shaft works, the said parts being so
arranged that when the hand chain wheel is turned in the direction to lift the load
the moving cam is loosened from the hand chain wheel and the end of the worm
spindle is thrust against its end pivot or bearing and when the hand chain is released
and the load is suspended or being lowered the moving cam is by friction so turned
between the hand chain wheel and fixed cross bar or bearing as to move the worm
shaft away from its end pivot or bearing and throw the thrust of the worm shaft
on the hand chain wheel, moving cam, and cross bar, and thus sustain the load by
the friction between the hand chain wheel and moving cam all substantially as
herein before described.
Dated this 7th day of March 1894.
CHARLES BOSWORTH KETLEY,
Agent for the Applicants.