Certain Improvements in Automatic Brakes for Pulley Blocks, Hoists, and other Lifting Appliances.
Year: 1893

page_text: Date of Application, 13th Oct., 1893
Complete Specification Left, 12th July, 1894-Accepted, 1st Sept., 1894
PROVISIONAL SPECIFICATION.
Certain Improvements in Automatic Brakes for Pulley Blocks, Hoists,
and other Lifting Appliances.
WC, JOSEPH HOLT and CHARLES WILLETTS, trading together as Holt &
Willetts, of Lion Works, Cradley Heath, Staffordshire, Manufacturers, and JOHN
WILLIAM POWELL, of 20 Mallin Street Smethwick, in the County of Stafford,
aforesaid, Foreman Fitter, do hereby declare the nature of this invention to be as
follows:-
This invention consists of the hereindescribed improved construction and
arrangement of the parts of automatic brakes for pulley blocks hoists cranes and
other lifting appliances. By our said invention a brake for the purposes set forth
is so arranged as to offer no resistance against the turning of the motion shaft to
lift the load but when the load is suspended or being lowered the brake is instantly
automatically applied in exact proportion to the lifted weight so that in any
particular pulley block or other lifting appliance to which our said invention is
applied the power required to lower the weight remains about the same for a light
load as for the heaviest load.
We will describe our said invention as applied to a pulley block of that kind in
which the weight is lifted by a worm and worm wheel the worm being mounted on
a horizontal shaft below or above the worm wheel. The worm wheel and worm
are made of so coarse a pitch that if there were no brake on the worm wheel shaft
the load would lower itself reacting through the worm wheel and worm and turning
the worm wheel shaft.
In carrying out our invention the hand chain wheel (over which passes the
endless hand chain for lifting and lowering) is mounted loosely upon the worm
shaft that is to say the hand chain wheel can turn through a certain angle
independently of the worm shaft. A hoss formed on one side of the hand chain
wheel has a helicoidal inclined plane or screw thread formed upon it or in it which
acts against a corresponding helicoidal inclined plane or screw thread formed upon
a collar fixed to the worm shaft or formed upon the worm shaft itself. A boss
formed upon the other side of the hand chain wheel made conical and turned
and fitting loosely upon this conical boss is a ratchet wheel made conical inside
corresponding with the boss of the hand chain wheel. A pawl on the pulley
block frame engages with the teeth of the ratchet wheel to prevent the ratchet
wheel turning with the worm shaft when the load is being lowered. A collar fixed
on the worm shaft keeps the coned ratchet wheel in position on the conical boss of
the hand chain wheel.
The automatic brake above described acts as follows:-When the hand chain
wheel is turned in the direction to lift the load the resistance to the turning of the
worm shaft caused by the load makes the helicoidal inclined plane or screw of
the hand chain wheel to act against the helicoidal inclined plane on the collar or the
screw thread on the worm shaft so as to thrust the conical boss of the hand chain
wheel against the conical ratchet wheel and the latter against the collar fixed on the
shaft so that the hand chain wheel ratchet wheel and worm shaft all turn together
in the same direction the teeth of the ratchet wheel passing the pawl and offering
no resistance against the lifting of the load. When the hand lifting chain is
released the lifted load tends to turn the worm shaft ratchet wheel and hand chain
wheel in the opposite direction but the turning of the ratchet wheel in this direction
is arrested by the pawl the friction between the conical boss of the hand chain

page_text: wheel and the conical ratchet wheel being sufficient to maintain the load so that
with a very slight pull on the hand lowering chain the hand chain wheel and worm
shaft can be turned together to lower the load.
It will be seen that by means of the helicoidal inclined planes or screw surfaces
acting as above described the thrust of the coned boss of the hand chain wheel
against the conical ratchet wheel and the resultant friction between these coned
surfaces is in exact proportion to the load being lifted so that the brake will sustain
either a heavy load or a light load and will offer no more resistance to the lowering
of a light load than it does to the lowering of a heavy load.
Instead of the frictional surfaces of the boss of the chain wheel and the
ratchet wheel being conical as above described they may be flat or otherwise
shaped. When made flat such flat surface forms the face of the boss of the hand
chain wheel which works against the corresponding flat face of the ratchet wheel.
Our invention above described is similarly applied to other lifting appliances
whether the power be obtained by worm and worm wheel gearing or by spur
gearing or by other means.
Dated this 12th day of October 1893.
CHARLES BOSWORTH KETLEY,
Agent for the Applicants.
COMPLETE SPECIFICATION.
Certain Improvements in Automatic Brakes for Pulley Blocks, Hoists,
and other Lifting Appliances.
We, JOSEPH HOLT and CHARLES WILLETTS, trading together as Holt &
Willetts, of Lion Works, Cradley Heath, Staffordshire, Manufacturers, and JOHN
WILLIAM POWELL, of 20, Mallin Street, Smethwick, in the County of Stafford,
aforesaid, Foreman Fitter, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
This invention consists of the hereindescribed improved construction and
arrangement of the parts of automatic brakes for pulley blocks, hoists, cranes
and other lifting appliances. By our said invention a brake for the purposes set
forth is so arranged as to offer no resistance against the turning of the motion shaft
to lift the load but when the load is suspended or being lowered, the brake is
instantly automatically applied in exact proportion to the lifted weight so that in
any particular pulley block or other lifting appliance to which our said invention is
applied the power required to lower the weight remains about the same for a light
load as for the heaviest load.
We will describe this invention as applied to a pulley block of that kind in which
the weight is lifted by a worm and worm wheel which are made of so coarse a pitch
that if there were no brake on the worm shaft the load would lower itself re-acting
through the worm wheel and worm and turning the worm shaft.
On the accompanying drawings Fig. 1 is a sectional side elevation of a worm and
worm wheel pulley block with our invention applied; Fig. 2 is a side elevation of the
same with the hand chain wheel removed; Fig. 3 is a plan of the same with
the hand chain wheel removed;
Figs. 4 and 5 are sectional elevations of the hand chain lifting wheel and
automatic brake parts of the said pulley block on an enlarged scale.
The same letters of reference indicate the same or corresponding parts in all the
figures of the drawings.
A is the worm wheel of the upper block gearing with and arrangel to be turned
by the worm B formed with the worm shaft C. Formed with the worm wheel A
is the toothed chain wheel D. E is the liiting chain which at one er is fixed at e¹

page_text: to one of the cross bars F' of the upper block and then passes underneath the
sheave G of the lower block and up and over the chain wheel D of the upper block,
so that as the worm shaft C is turned in one or the other direction the worm wheel A
and chain wheel D will be turned and the weight suspended by the lower block will
be raised or lowered as is well understood. The parts above described are of
ordinary construction and their action is well known.
In carrying out this invention the hand chain wheel H (over which passes the
endless hand chain I for lifting and lowering) is mounted loosely upon the worm
shaft C that is to say the hand chain wheel H can turn through a certain angle
independently of the worm shaft C. Formed on one side of the hand chain,
wheel H there is a boss ¹ which has a helicoidal inclined plane h² formed upon it
which acts against a corresponding helicoidal inclined plane formed upon the
collar J which is fixed to or formed on the worm shaft C. The boss h³ formed
upon the other side of the hand chain wheel H is made flat and turned (or as
hereinafter described this boss may be conical or otherwise shaped) and fits against
the face of the ratchet wheel K which is made to correspond with the face of the
boss and which rides loosely on the worm shaft C. The spring pawl / on the
cross bar F2 of the pulley block frame engages with the teeth of the ratchet
wheel K (see Figs. 2 and 3) to prevent the ratchet wheel turning with the worm
shaft C when the load is being lowered. A collar M rigidly fixed on the worm
shaft C keeps the ratchet wheel K in position against the boss h³ of the hand chain
wheel H. The worm shaft C is prevented from moving endwise by the collar c¹
formed thereon bearing against the cross bar F2 and by the end of the worm shaft C
taking against the closed end of its bearing in a cross bar F.
The automatic brake above described acts as follows:-When the hand chain
wheel H is turned in the direction to lift the load, as indicated by the arrow on the
right hand side of Fig. 2, the resistance to the turning of the worm shaft C caused
by the load makes the helicoidal inclined plane 2 of the hand chain wheel H to
act against the helicoidal inclined plane on the collar J on the worm shaft C, so as to
thrust the hand chain wheel H against the face of the ratchet wheel K (see Fig. 4)
and the latter against the collar M fixed on the shaft C, so that the hand chain
wheel H ratchet wheel K and worm shaft C all turn together in the same direction,
the teeth of the ratchet wheel K passing the pawl which offer no resistance
against the lifting of the load. When the hand lifting chain I is released the
lifted load tends to turn the worm shaft C, collar M, ratchet wheel K, and hand
chain wheel H, in the opposite direction (shewn by the arrow on the left hand side
of Fig. 2) but the turning of the ratchet wheel K in this direction is arrested by
the pawl and then the friction between the boss 3 of the hand chain wheel H and
face of the ratchet wheel K and fixed collar M as aforesaid is sufficient to
maintain the load, so that a very slight pull on the hand lowering chain I, in the
direction shewn by the arrow on the left hand side of Fig. 2, will turn the hand
chain wheel H collar J and worm shaft C together slightly loosening the face of
the hand chain wheel H from the ratchet wheel K (see Fig. 5) and lowering the
load.
It will be seen that by means of the helicoidal inclined planes as above described
the thrust of the boss of the hand chain wheel H against the face of the ratchet
wheel K is in exact proportion to the load being lifted so that the brake will
sustain either a heavy load or a light load and will offer about the same resistance
to the lowering of a light load as it does to the lowering of a heavy load.
It will be evident that without departing from the nature of our invention the
boss of the hand chain wheel H may be made with two or more of the helicoidal
inclined planes 2 and the collar J be made with two or more helicoidal inclined
planes to correspond therewith also that instead of the frictional surface of the
boss and the hand chain wheel H and the corresponding face of the ratchet
wheel E being made flat as above described and shewn in Figs. 1, 3, 4 and 5
these frictional surfaces may be made conical or otherwise shaped as will be well
understood.

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 :-
In an automatic brake for pulley blocks hoists and other lifting appliances, the
combination with the worm shaft C, having a collar provided with an incline or
inclines, of a chain wheel loose on the shaft and having a corresponding incline or
inclines, a ratchet wheel K, also loose on said shaft and having frictional contact
with said chain wheel, a pawl engaging said ratchet wheel, and a collar M, for
holding said ratchet wheel against lateral movement, substantially as hereinbefore
described.
Dated this 11th day of July 1894
CHARLES BOSWORTH KETLEY,
Agent for the Applicants.