IMPROVEMENTS IN HYDROSTATIC JACKS OR LIFTING APPARATUS
Year: 1859

page_text: PROVISIONAL SPECIFICATION left by William Robertson and John
Tweeddale at the Office of the Commissioners of Patents, with their
Petition, on the 19th September 1859.-A communication from abroad
by John Robertson, of Brooklyn, New York, United States.
We, WILLIAM ROBERTSON and. JOHN TWEEDDALE, both of Johnstone, in the
County of Renfrew, North Britain, Engineers, do hereby declare the nature of
the said Invention for, "IMPROVEMENTS IN HYDROSTATIC JACKS OR LIFTING
APPARATUS," a communication from abroad by John Robertson, of Brooklyn,.
New York, United States, to be as follows:-
This Invention relates to an improved arrangement and construction of
hydrostatic jacks, which are compact in form, and applicable to a greater.
variety of purposes than those at present in use. Under one modification, the
jack consists of a rectangular base, by preference made of cast iron, and
hollow so as to form a holder or reservoir for the water or other actuating
fluid. Springing from the base, and forming a part of it, is a vertical cylinder,
closed at the upper end, but having a central open tube cast in one with the
cylinder and base, or these several parts may be screwed or otherwise fitted
together. The central tube descends into the chamber or reservoir in the
base, where it branches off at a right angle, and enters a transverse passage
which communicates with the chamber of the force pump, the passage of the
water or other liquid to the central tube being controlled by an outlet valve
which prevents the return of the liquid to the reservoir. The chamber of the

page_text: force pump has another tubular passage which forms the communication
between it and reservoir in the base; this inlet passage is shut by means of a
valve, which prevents the return of the liquid in that direction. The chamber
and plunger of the force pump are arranged in an angular position across the
reservoir; the plunger is made upon the trunk principle, about one-half of its
length being made tubular. The plunger is connected by a link which works
on a pin, crossing the lower end of the tubular part to the actuating hand
lever, the lower end of which is jointed to a pair of lugs cast on the pump
cylinder, and projecting out over the base. The actual lifting part of the
jack consists of a cylinder, closed at the upper end, and sliding up and down
on the vertical cylinder connected with the base. The upper end of this
sliding cylinder is fitted with the ordinary tripod head piece, which is brought
under the object to be lifted; it has also a toe piece which projects outwards
in a lateral direction from the lower part of the external or lifting cylinder.
This part is exceedingly useful for lifting anything from the floor, a pur-
pose to which the ordinary lifting jacks is wholly inapplicable. Upon the
pump lever being put into action the liquid is forced up the central tube so as
to raise the external cylinder, any leakage of the water being prevented
by a metallic or other packing placed between the upper extremity of the
tube and inner surface of the lifting cylinder; in this way, as the liquid is
forced up the pump, the external cylinder is raised, lifting with it the object
to be moved or supported. And where a longer range of lift is required, the
lifting cylinders are made telescopic so as to slide one within the other; when
the jack is to be lowered, the let-off valve is gradually eased to allow the liquid
to escape back into the reservoir. This valve is simply a rod of metal, one
end of which is pointed, and enters a hole in the central tube through which
the water is forced. The outer end of the valve spindle projects out through
the side of the reservoir, and has a thumb nut fitted thereto to allow of its
being screwed to and fro, and thus close or open the passage between
the central vertical tube and the chamber or reservoir in the base of the
machine.