AN IMPROVED AUTOMATIC BRAKE FOR CRANES, CRAB WINCHES, HOISTS, ROPE AND CHAIN PULLEY BLOCKS, AND OTHER USEFUL PURPOSES."
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by Charles Thomas Powell at the Office.
of the Commissioners of Patents on the 25th August 1879.
"
CHARLES THOMAS POWELL, of 174, Lodge Road, Birmingham, Engineering
Draughtsman. AN IMPROVED AUTOMATIC BRAKE FOR CRANES, CRAB WINCHES,
HOISTS, ROPE AND CHAIN PULLEY BLOCKS, AND OTHER USEFUL PURPOSES."
This Invention of an improved brake arrangement for cranes, crab winches, hoists,
rope and chain pulley blocks, rolling stock, and all kinds of machinery where a
reverse motion should either be automatically stopped, checked, or under perfect
control, consists of a combination of mechanical arrangements by which a sufficient
amount of friction is produced which will prevent the running down of the load
suspended when the motive power which has raised it is removed, whilst by the
said arrangement the friction may be reduced so as to lower it at will, or removed
so as to allow the load to run down rapidly. To obtain these results I arrange the
parts so that the pressure of the load or weight being lifted or lowered acts upon
a rotary part of the arrangement of such a diameter, or with the intensity of the
pressure applied to it, so arranged with respect to the other parts of the machinery
that the load or weight itself will not overcome the friction produced by itself, and
the load or weight consequently will not run down.
When lifting, these frictional parts are kept clear of each other, but in lowering
are brought into operation, a lever with or without a cord or other equivalent being
used for this purpose.
In carrying my Invention into effect when applied to cranes, crab winches, and
similar purposes where there is a brake wheel and brake band I employ the fol-
lowing method :-
The brake wheel is secured in the ordinary manner, and in the ordinary position.
The iron or steel band the section of which shall be determined by the requirements
of each particular case of application with or without wood blocks or other material
for regulating the amount of friction. To the one end of this band I attach by
necessary means a roller of such diameter as may be necessary with respect to the
other parts of the construction which is acted upon by the part of the brake wheel
not covered by the band, also capable of rolling upon a lever whose business it is to
keep the said roller constantly pressed against the wheel to insure its rolling action,
either whilst raising or lowering the load. The other end of the band is secured
either to the framework of the construction or to the lever itself.

page_text: Upon this lever there may or may not, as the case may require, be attached
another roller upon which the roller which is attached to the band may revolve
freely when the load is being raised.
In applying this Invention to pulley blocks and machinery requiring similar
treatment the brake is made to act upon the rope or chain itself or upon a brake
wheel attached, and either to be secured to the frame or to the lever, as before
described. The one end of this lever which is operated upon to reduce the friction
that is free the roller.shall be made of such a form with or without a roller attached
so that the said reduction of friction may be accomplished either by a separate cord
attached thereto or the hoisting rope or chain itself.
This Invention may be applied to rolling stock when a retrograde motion is to be
checked or avoided and to other useful purposes where a reverse motion is required
to be checked.