IMPROVEMENTS IN HYDRAULIC LIFTING APPARATUS
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by Michael Scott at the Office of the
Commissioners of Patents on the 9th February 1881.
MICHAEL SCOTT, of No. 9,.Great Queen Street, Westminster, in the County of
Middlesex. <
IMPROVEMENTS IN HYDRAULIC LIFTING APPARATUS."
My Invention relates to appliances to be employed in connection with hydraulic
lifts and cranes, of the kind in which the weight of the moving parts of the lift or
crane and load is raised by hydraulic pressure, my object being to economise the
bydraulic power employed, by utilising the descent of the weights for accumulating
pressure to be subsequently used for raising the weights. For this purpose, instead
of allowing the discharge water from the hydraulic cylinders of the lifts or cranes
to flow away, I cause it to enter a hydraulic cylinder, having a plunger loaded so
as to give such pressure as will nearly balance that required for supporting the
crane or lift plunger, and from this cylinder I draw the water for supplying the
hydraulic pumps that charge the accumulator at the higher pressure required for
working the lifts or cranes. The pumps are thus supplied with water already
under considerable pressure, and the work which they have to perform is reduced
to that of giving the additional pressure required. This action of the pumps in
conjunction with the intermediate cylinder may be obtained by combining the
intermediate cylinder with a pump or accumulator in the following manner:-I
make the cylinder with a loaded trunk piston, so as to present on one side the full
area of the piston, and on the other side a smaller annular area; and I arrange in
passages to the two ends of the cylinder suitable valves, by which the following
action is effected :-When the lift or crane weight is descending, the water from its
cylinder is admitted to act on the full area of the loaded piston, causing it to rise,
the smaller quantity of water from the annular space above the loaded piston being
allowed to flow to waste. When it is required to raise the lift or crane, commu-
nication is opened between the two ends of the cylinder, and also with the high
pressure supply main; the loaded piston thereupon descends, forcing the contents
of the cylinder partly along the supply pipe to the lift or crane, and partly to the
annular space above the piston. Two or more cylinders with their loaded pistons
may be arranged to work alternately or successively, as above described, so that
their action may be continuous, as might be required when they are employed in
connection with several lifts or cranes, and in such a case the piston of each may
37

page_text: by means of suitable tappets work the valves of the others. When it is required
to make these pistons act with varying pressure, I arrange in connection with their
cylinders two or more smaller subsidiary cylinders, the pistons of which may, when
required, be connected to the load on the main piston so as to increase or diminish
it according as these subsidiary pistons are subjected to pressure in the one
direction or the other.
Hydraulic cranes of the kind referred to are often arranged so as to turn on
their hydraulic plungers as on crane posts.
In order to diminish the friction of
the bearing surfaces I form in either of them a hollow, into which I force liquid,
under sufficient pressure to relieve a considerable part of the weight, and this
liquid may be oil or other lubricant.