Safety Apparatus for Hydraulic Lifts.
Year: 1895

page_text: Date of Application, 8th Mar., 1895
Complete Specification Left, 6th Dec., 1895-Accepted, 11th Jan., 1896
PROVISIONAL SPECIFICATION.
Safety Apparatus for Hydraulic Lifts.
We, JAMES PITCAIRN HALKET of 135 East India Road, Poplar, in the
County of Middlesex, Engineer, and JOHN KENNEDY of 11 Fellows Road, South
Hampstead, in the County of Middlesex, Engineer, do hereby declare the nature of
this invention to be as follows:-
:-
Our invention relates to safety apparatus applicable to hydraulic lifts for
preventing a sudden descent of the cage in case of the pressure supporting it being
accidentally relieved by the bursting of a pipe or otherwise.
To provide against the danger of such an accident due to the bursting of the
service high pressure supply pipe, we introduce between it and the regulating valve
of the lift a check valve provided with a spring which in case of the sudden relief
of pressure in the service pipe, closes against escape of water from the lift
cylinder.
Also to provide against any accident occurring below the cage we provide under
the bottom of the cage a hydraulic cylinder communicating with the lift cylinder
preferably through the ram which is purposely made tubular, or it may be by a
flexible tube communicating with the ram cylinder. The piston or plunger of this
hydraulic cylinder is urged by a spring suitably adjusted so as to apply a brake or
shoot a bolt whenever the pressure in it is unable to overcome the spring. Thus
in case of sudden relief of pressure in the lift cylinder from any cause there is a
corresponding reduction of pressure in the cage cylinder and thereupon the spring
causes the brake to be applied or the bolt to be shot preventing the cage from
descending. The bolt may shoot into links of a chain or into teeth of a rack and
there may be several such cylinders with bolts or brakes operating together.
Instead of the bolt or brake being actuated by a spring brought into action by
relief of pressure, a load or weighted lever may be actuated by such relief of
pressure.
Dated this 8th day of March 1895.
ABEL & IMRAY,
Agents for the Applicants.
Safety Apparatus for Hydraulic Lifts.
We, JAMES PITCAIRN HALKET, of 135 East India Road, Poplar, in the
County of Middlesex, Engineer, and JOHN KENNEDY of 11 Fellows Road, South
Hampstead, in the County of Middlesex, Engineer, 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 :-
Our invention relates to safety apparatus applicable to hydraulic lifts for
preventing a sudden descent of the cage in case of the pressure supporting it being
accidentally relieved by the bursting of a pipe or otherwise.
To provide against the danger of such an accident due to the bursting of the
service high pressure supply pipe, we introduce between it and the regulating valve
[Price 8d.]

page_text: of the lift a check valve provided with a spring which in case of the sudden relief
of pressure in the service pipe, closes against escape of water from the lift
cylinder.
Fig. 1 of the accompanying drawings is a vertical section of a valve for this
purpose. The supply through the regulating valve from the pressure main,
entering at A raises the valve C in opposition to the adjustable spring D, and
passes by B to the lift cylinder. Should the pressure in the pipe leading to A
suddenly drop, the valve C is caused by the spring D to close preventing escape
from the lift cylinder.
In order to diminish shock resulting from the sudden closing of the valve C, a
small spring relief valve E can open relieving the pressure in the passage above the
valve C.
Also to provide against any accident occurring below the cage, we provide under
the bottom of the cage a hydraulic cylinder communicating with the lift cylinder
preferably through the ram which is purposely made tubular, or it may be by a
flexible tube communicating with the ram cylinder. The piston or plunger of this
hydraulic cylinder is urged by a spring suitably adjusted so as to apply a brake or
shoot a bolt wherever the pressure in it is unable to overcome the spring.
Fig. 2 is a section of a cylinder for this purpose to be fixed on the bottom of the
cage. The lift cylinder communicates preferably through its tubular ram, with
the passage F so that the pressure of the water in the lift cylinder acts on a
piston G and forces it back in opposition to an adjustable spring H.
To the rod of the piston G is attached a latch bolt L which can engage with
ratchet teeth K on one of the vertical guides of the cage. Should the pressure in
the lift cylinder become greatly reduced, the spring H pushes forward the
piston G and its latch bolt L causing it to engage in the ratchet teeth K and so
stop the descent of the cage. For the ratchet teeth K may be substituted a fixed
chain into the links of which the latch bolt L may shoot.
Instead of the cage
being completely stopped by a bolt as above described, its descent may be retarded
by substituting for the latch bolt L a brake block bearing against the face of the
vertical guide.
Two or more sets of the apparatus described may be applied to the cage, all
their cylinders communicating with the lift cylinder so as to act together in case of
serious relief of the pressure in the lift cylinder. For the spring H may be
substituted a bell crank lever having its vertical arm bearing against the piston
rod M and its horizontal arm loaded with an adjustable weight.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what
we claim is :-
1. In combination with the passage to and from a hydraulic lift cylinder an
adjustable loaded check valve and relief valve, arranged and operating substantially
as described with reference to Fig. 1.
2. In combination with a hydraulic lift, a cylinder fixed on the cage and
communicating with the lift cylinder and an adjustably loaded piston arranged to
work a bolt or brake, substantially as and for the purpose set forth.
Dated this 6th day of December 1895.
ABEL & IMRAY,
Agents for the Applicants.