IMPROVEMENTS APPLICABLE TO LIFTS OR HOISTS
Year: 1878

page_text: PROVISIONAL, SPECIFICATION left by Astley Paston Price at the Office of
the Commissioners of Patents on the 1st May 1878. A communication from
abroad by Emile Heurtebise, of Paris, in the Republic of France.
ASTLEY PASTON PRICE, of 47, Lincoln's Inn Fields, in the County of Middlesex.
"IMPROVEMENTS APPLICABLE TO LIFTS OR HOISTS." A communication from abroad
by Emile Heurtebise, of Paris, in the Republic of France.
This Invention relates to a hydraulic safety apparatus or brake, more particularly
applicable to direct-acting lifts or hoists, that is to say, those in which the load is
supported directly by the rod of the rau or plunger piston, serving to elevate it,
and which is balanced by counterweights.
The connection of the cage, for example, in the case of an ordinary lift with the
rod of the ram or piston may be so formed as to obviate all liability of the two
parts becoming separated, and the sole possible cause of accident is the rupture of
the chain of the counterweights. It is evident that in case of such rupture taking
place the cage with the persons or other weights with which it is loaded, and the
ram or plunger piston being no longer supported by the counterweights, will descend
with a rapidity which increases continually, the ram or plunger piston re-entering
the cylinder, and rapidly forcing back the water through the discharge orifice or
through the inlet orifice, according as an accident takes place during an ascent or a
descent of the cage. Hence it is apparent that the rupture of the connection with
the counterweights results in an increase of pressure on the water contained under
the ram in a proportion which principally depends upon the weight of the said
ram and of the load which it carries.
This Invention consists in utilising this excess of pressure which is generated in
the cylinder of the lift at the moment when a rupture occurs for the purpose of
automatically closing the orifice of the water by means of an apparatus suitably
arranged, and consequently forming a stationary column of water under the ram,
which supports it in a fixed position with its load, thus obviating all danger of
further injury.
An apparatus of this description forms in principle a safety valve interposed
between the distributing valve and the ram cylinder, and loaded to support the

page_text: greatest normal pressure in the apparatus, that is to say, a pressure slightly in
excess of that of the water on admission, this valve being arranged so as to inter-
cept all communication between the cylinder and its pipe connected with its lower
end directly the pressure in the cylinder exceeds the limits of normal maximum
pressure at which the lift is to be worked.
In carrying out this Invention the apparatus is composed of a vertical tube
provided with two horizontal tubular connections, and at its lower end closed by a
disc perforated with a small orifice, and at its upper end closed by a cover, through
which is passed a rod carrying a roller at its upper extremity, and forming part of
a hollow cylinder which fits into the lower part of the tube. The upper part of this
cylinder is provided with an enlargement or piston working in the upper part of
the tube (which is made of corresponding size), suitable leather packing rings being
provided both on the cylinder and on the piston to prevent leakage, and the orifice
in the disc admits of the escape of any water which may gain access beneath the
cylinder in consequence of any imperfections in the joint, and ensures the proper
working of the apparatus.
The cylinder is provided with two apertures similar to those in the plug of a
stop-cock, and which allow free communication between a distributing valve and
the cylinder of the ram of the lift or hoist when the said apertures are situate
opposite the two tubular connections, as is the case when the movable cylinder is in
its lowest position.
The diameter of the piston which forms part of the movable cylinder being greater
than that of the cylinder an annular space is formed underneath the former, which
is exposed to the pressure of the water.
The piston forms part of a rod which is bifurcated at its upper extremity, and
carries a roller supporting a lever jointed at one end to a fixed bar, and loaded at
the other end with a weight calculated according to the length of the lever and the
maximum pressure which the piston is required to resist without rising.
From the foregoing it is evident that a slight excess of pressure exerted on the
annular piston will cause the movable cylinder to rise and with it the apertures,
thus partially or wholly closing the tubular connections, and restraining or entirely
arresting the flow of the water from under the ram cylinder, and thereby retarding
or suspending the motion of the cage.
It is evident that this improved apparatus will act not only as a brake in case of
accident, but even as a regulator of the motion when the cage is descending over-
loaded, as the excess of pressure will then cause the piston to rise to a certain extent,
and with it the cylinder, thus reducing the sectional area of the channel for the
escape of the water.
°
The counterweight employed for balancing the pressure to which the piston is
exposed may obviously be replaced by a spring acting upon the piston, either directly
or through the intervention of a lever.