Improvements in Pneumatic Hoists.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Pneumatic Hoists.
1, STEPHEN EVANS ALLEY, of the Sentinel Works, Polmadie, in the County of
Glasgow, North Britain, Engineer, do hereby declare the nature of this invention
to be as follows, that is to say:
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My said invention has for its object to improve the construction of pneumatic
hoists so as to render them more easily controlled and more satisfactory and reliable
in use than such hoists as hitherto constructed.
In carrying out my invention I provide in addition to the ordinary valve
for controlling the admission of the compressed air to the suspended vertical
cylinder of the hoist in which the piston works, a valve in the air admission
passage and between the controlling valve and the cylinder. This valve is arranged
to be acted on by a collar or nut formed or fixed on the piston rod or by a ring
clipped thereon at any required part of its length the collar or ring automatically
closing the valve on the hoist reaching the desired height. A spring ordinarily
holds this additional valve open. In some cases the collar or ring on the piston
rod is arranged to also act through a lever or otherwise on a further additional
valve, and if the load on the hoist becomes reduced after having been raised this
valve is opened by a small further rising of the piston and its rod and the air in
the cylinder escaping through the valve the internal pressure is correspondingly
reduced to exactly balance the altered load. When the desired reduction in the
internal air pressure is effected the ring ceases to act on the valve, the valve is
automatically closed by the action of a spring and this prevents the piston from
falling below its proper position.
To allow of the piston and its rod being held up independently of the air pres-
sure in the cylinder when necessary or desirable a pair of brake blocks are
arranged in guides formed in parts formed on or fixed to the bottom of the
cylinder and can be made to grip the piston rod by pulling a chain or cord
attached to the inner ends of levers fixed on eccentrics acting on the brake blocks.
When the chain or cord is let go a spring attached to the inner end of the levers
causes them to withdraw the blocks from the piston rod and allow the piston to be
raised or lowered as may be required.
Dated this Twenty-seventh day of May 1898
EDMUND HUNT,
Applicant's Agent.

page_text: air pressure in the cylinder, A, when necessary or desirable a pair of brake
blocks, H1, H2, are arranged in guides, J 1, 2, formed on the gland, A2, in
the bottom of the cylinder (A). These parts are shown separately in Figures, 4,
5, 6. Figures, 4, and 5, are vertical sections as at right angles to each other;
and Figure, 6, is a horizontal section. As shown the brake blocks, H1, H2, can
be made to grip the piston rod, B1, by pulling a chain or cord (not shown) but
attached to and extending down from the inner ends of levers, K1, K2, fixed on
When the chain or
eccentrics, L1, L2, acting on the brake blocks, H1, H2.
cord is let go a spring, M, also attached to the inner end of the levers, K1, K2,
and to the gland, A2, causes the levers to withdraw the blocks, H1, H2, from
the piston rod, B1, and allow the piston, B, to be raised or lowered as may be
required.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:.
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1. In a pneumatic hoist fitting in the air admission passage between the
ordinary controlling valve and the cylinder a spring valve to be acted on through
a lever by a collar or nut on the piston rod or by a ring clipped thereon sub-
stantially as and for the purposes herein before described.
2. In a pneumatic hoist fitting in the cylinder an air escape valve held closed
by a spring on its spindle and opened through the action of a lever which is
acted on by a collar or nut on the piston rod or by a ring clipped thereon sub-
stantially as and for the purpose hereinbefore described.
3. In a pneumatic hoist the application to the piston rod of a pair of brake
blocks arranged in guides and actuated through levers fixed on eccentrics acting
on the brake blocks substantially as and for the purpose herein before described.
Dated this Twenty-second day of February 1899.
EDMUND HUNT,
Applicant's Agent.