Improvements in Automatic Breaks for Pulley Blocks and Hoists.
Year: 1893

page_text: Date of Application, 18th Mar., 1893-Accepted, 13th May, 1893
COMPLETE SPECIFICATION.
Improvements in Automatic Breaks for Pulley Blocks and Hoists.
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 consists of the herein described improved construction of auto-
matic breaks to be applied to geared pulley blocks and hoists and particularly to
those geared pulley blocks and hoists in which the lifting power is obtained by
worm and worm wheel gearing.
The object of the break is to prevent the worm and worm wheel or other
gearing running back when a weight is being lifted or lowered and by this inven-
tion the break mechanism is so arranged that while it offers no obstruction to lifting
the weight the break is instantly applied in exact proportion to the weight being
lifted or lowered so that if the weight be light the holding power of the break will
be less than when lifting a heavier weight thus the resistance to the pull of the
hand chain by the person operating the lift or hoist is about the same in all cases.
We will describe this invention by referring to the accompanying drawings on
which
Fig. 1 is a sectional elevation of a worm and worm wheel pulley block with this
invention applied; Fig. 2 is a front sectional elevation of the same on line X X
of Fig. 1; Fig. 3 is a plan of the same;
Figs. 4 and 5 are sectional elevations of the break mechanism of the said pulley
block on an enlarged scale Fig. 4 shewing the parts in the positions which they
occupy when a load is being lifted and the break is "off" and Fig. 5 shewing the
parts in the positions which they occupy when the break is "on" and a load is held
suspended by the block or the load is being lowered ;
Figs. 6 7 and 8 shew details of the said break mechanism on the same scale as
Figs. 4 and 5;
Fig. 9 shews in sectional side elevation a slightly modified form of this invention
applied to a pulley block of the kind described in the Specification No. 22173 of
1892 in connection with Priest and Millward's application for Letters Patent for
an invention entitled "Improvements in pulley blocks and in certain other lifting
appliances; " Fig. 10 is an end sectional elevation of the said modification and
Fig. 11 is a plan of the same.
The same letters of reference indicate the same or corresponding parts in all the
figures.
Referring firstly more particularly to Figs. 1 to 8 both inclusive it will be seen
that the top block consists of a worm A mounted on a shaft B and gearing with a
worm wheel C which is mounted on an axle c', and cast with or fixed to the worm
wheel C so as to turn with it is the chain wheel D made with the usual teeth
between which the links of the hoisting chain E fit. One end of the hoisting
chain E is fixed at el to the frame of the pulley block and is carried down and
under the sheave f in the bottom block and then up and over the chain wheel D
he remaining portion of the chain hanging down loosely as shewn in Fig. 1. The
vorm shaft B is turned by the endless hand chain 9 passing over the break
wheel H which is fixed to the worm shaft B. The worm shaft B revolves in
ournals or bearings in the cross pieces I'I' of the pulley block frame. So far,
with the exception of the form of the worm A hereinafter described, this is a usual
onstruction of geared pulley block which is well known.
We apply and arrange this invention as follows:-The break wheel H has aq
ΓΟ

page_text: annular rim / cast on one side of it and to act upon the outside of this rim we
provide a break lever J (shewn separately by Fig. 6) the outer end of which is
formed to fit against the outside of the rim. This break lever J is free to turn
upon an eccentric k which is formed on the cross piece I' of the pulley block frame
and through which the worm shaft B also passes. This cross piece I² is shewn
separately by Fig. 7. The hole forming the bearing in the cross piece I' for the
worm shaft B is, for the purpose hereinafter described, made slightly elongated as
shewn to allow of the worm shaft B moving up or down to a small extent. Or for
the same purpose there may be a bearing block in which the worm shaft B fits and
which is free to move up and down to a small extent in the cross piece I'. M is
another break lever which we provide and form to act upon the inner surface of
the rim. This break lever M is centred on a pin m² fixed to the cross piece I'
and the outer end m³ of the said break lever M is so located as to be operated upon
by the other lever J when the break is acting as hereinafter described. 12 18 &
small spring connecting the lever J to the cross piece I and keeping the outer
end of the break lever J in contact with the rim. A. The worm wheel C and
worm A are by preference made of coarse pitch and the latter is by preference not
arranged on the centre line of the worm wheel as is usual, but, as shewn in Fig. 1,
the worm is at that side of the worm wheel C nearer to the break wheel H so
that the downward push of the worm wheel on the worm will be greater at the
break wheel than would be the case if the worm were placed under the centre of
the worm wheel. The worm may however be placed under the centre of the worm
wheel if desired.
The break mechanism above.described operates as follows
When the load is being lifted by turning the worm shaft B in the direction
shewn by the arrow in Figs. 2 and 4 the worm shaft B, being forced outwardly by
the worm wheel C re-acting upon the worm A, bears upon the bottom of its
bearing in the cross piece 12 and the little friction which there is between the
acting surfaces of the break rim h¹ and break lever end j' causes the break lever .)
to turn about the eccentric to the position shewn by Figs. 2 and 4 so that the
break lever imparts no appreciable pressure on the break rim. The inner break
lever M is then also inactive. When however the hand chain g is released by the
person operating the pulley block, or the worm shaft B is turned in the opposite
direction as indicated by the arrow in Fig. 5 to lower the load, then the friction
between the break rim h¹ and the break lever J causes the break lever J to turn
about the eccentric K in the opposite direction and to act upon the break rim to
such an extent as to lift the same and the worm shaft B in its bearing against the
outward pressure of the teeth of the worm wheel and to ultimately assume the
position shewn in Fig. 5. Thus it will be seen that the pressure of the break
rim h on the break lever j' and the break friction is in exact proportion to the
load lifted.
When the break lever J has moved far enough to come into contact with the
inner break lever M as shewn in Fig. 5 it presses this lever M against the inside
of the break rim and the lever M and increases the break friction and also forms
a stop to prevent the outer break lever J turning too far and holding the break rim
with too much friction.
In those pulley blocks and hoists where the worm is located above the worm
wheel the break mechanism above described would act equally well but break
levers J and M would then act upon the upper part of the wheel rin; or as shewn
by Figs. 9, 10 and 11 the break lever J may be rigidly fixed to the pulley block
frame just above the rim h¹ so that the act of pulling down the hand chain
g to lift
the load also pulls down the worm shaft B in its oval bearing and the break rim /
away from the fixed break h' and the latter does not act upon the break rim; but
when the band chain g is released the teeth of the v worm wheel acting upon the
worm force the worm shaft and break wheel Ḥ upwardly against the fixed break
portion j and thus cause break friction in proportion to the load which is being
lifted.

page_text: 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 :-
:―
1. The hereindescribed improvements in automatic breaks for pulley blocks and
hoists to cause the amount of break friction to be automatically regulated by the
load and in proportion thereto, that is to say, making the hand gear shaft such
as B with some side play in combination with a break lever such as j¹ mounted
eccentrically to the said shaft and shaped to act upon a break wheel fixed thereto
so that when the said shaft is turned to lift the load the break lever will be free
on the break wheel and the shaft will be thrust outwardly by the hoisting gear,
and when the said shaft is turned in the opposite direction the break lever will
grip the break wheel and thrust the said shaft inwardly towards the gearing,
substantially as hereinbefore described with reference to Figs. 1 to 8 both inclusive
of the accompanying drawings.
2. In pulley blocks and hoists the combination of parts constituting the means
for regulating the break friction in proportion to the load, arranged and operating
substantially as herein before described and illustrated by Figs. 1 to 8 both inclusive
of the accompanying drawings.
3. The combination and arrangement of parts forming the improved worm and
worn wheel pulley block hereinbefore described and illustrated by Figs. 1 to 8 of
the accompanying drawings.
4. The hereindescribed improvements in automatic breaks for pulley blocks and
hoists to cause the amount of break friction to be automatically regulated by the
load and in proportion thereto, that is to say, making the hand gear shaft such
as B with some side play in combination with a stationary break such as j' fixed
adjacent to and shaped to act upon a break wheel fixed on the said shaft and so
arranged that in the act of turning the shaft to lift the load the said shaft is pulled
sideways against the gearing and away from the fixed break and when the load is
Suspended or being lowered the gearing thrusts the shaft sideways and the break
wheel against the break so as to support the load substantially as hereinbefore
described with reference to Figs. 9, 10 and 11 of the accompanying drawings.
Dated this 13th day of March 1893.
CHARLES BOSWORTH KETLEY,
Agent for the Applicants.