IMPROVEMENTS IN HYDRAULIC CRANES
Year: 1876

page_text: LETTERS PATENT to Robert Mills, of 3, Grove Villas, Chestnut Grove, Balham,
in the County of Surrey, for the Invention of "IMPROVEMENTS IN HYDRAULIC
CRANES."
PROVISIONAL SPECIFICATION left by the said Robert Mills at the Office of
the Commissioners of Patents on the 25th March 1870.
ROBERT MILLS, of 3, Grove Villas, Chestnut Grove, Balham, in the County of
Surrey. "IMPROVEMENTS IN HYDRAULIC CRANES."
This Invention has for its object improvements in hydraulic cranes."
In the construction of hydraulic cranes I arrange the hydraulic cylinders and
apparatus by which the crane is turned in such manner as to render them available
also for lifting or aiding in lifting loads. I also arrange the hydraulic cylinder and
apparatus which is used to return the main ram when the load upon the crane is
insufficient to carry it back in such manner that it may be used as an auxiliary
lifting cylinder; and I use it also for varying the power of the crane by in some
cases relieving its ram or piston from the water pressure, and in other cases causing
the main lifting cylinder to work against the resistance which it offers when the
water pressure is on. usually employ four cylinders, the main lifting cylinder and
two turning cylinders; these are arranged parallel the one to the other, and they
all have rams working in them. The fourth cylinder, which I term the lowering
cylinder, contains a piston, and the rod of this piston is attached to the pulley frame
which is mounted on the head of the ram of the lifting cylinder. The chain for
swinging the jib is carried round the turning drum and over the sheaves at the
ends of the turning rams as usual, but the ends instead of being made fast are
attached to the lifting sheave frame, so that the turning cylinders, in addition to
their ordinary function of swinging the jib, can be used in lifting light loads or as
auxiliaries in lifting heavy loads.
In swinging the jib the pressure of water is admitted to one only of the turning
cylinders, and the other is allowed to discharge its water into the exhaust. The
crane thus is capable of exerting several degrees of
[Price Bd/1
power.

page_text: In lifting a load by means of the turning cylinders the water is admitted to both
turning cylinders, and if the load is not too heavy to be lifted by these cylinders
the lifting sheave frames, with the ram and piston of the lifting and lowering
cylinders will be moved, the lifting cylinder and front end of the lowering cylinder
drawing water by suction from the exhaust pipes, and the water from the back of
the piston of the lowering cylinder being discharged into the front end of the
lowering cylinder or into the lifting cylinder along with the water from the exhaust.
If the power of the turning cylinder is insufficient to lift the load then the water
is admitted to the front end of the lowering cylinder to assist in lifting, when if
the load is not too heavy the lifting sheave frame with the ram and piston of the
lifting and lowering cylinders will be moved, the back of the lowering cylinder dis-
charging its water into the lifting cylinder, and the deficiency if any in the lifting
cylinder being filled from the exhaust as before. Should the turning and lowering
cylinders be of insufficient power to lift the load the pressure of water is admitted
to the lifting cylinder and shut off from the lowering cylinder; and if the power
now applied is sufficient to lift the load the front end of the lowering cylinder will
draw water from the exhaust, and the back end of the lowering cylinder will
discharge its water against the pressure into the lifting cylinder. Should the power
as last applied be insufficient to lift the load the pressure of water will be readmitted
to the front of the lowering cylinder, which will now act in conjunction with the
turning and lifting cylinders, the back end of the lowering cylinder as before dis-
charging its water against the pressure of the water into the lifting cylinder.
Should the power applied as last described be insufficient to lift the load then the
water from the back end of the lowering cylinder is allowed to discharge into the
exhaust when the full power of the crane will be exerted. In lowering the load on
allowing the water from the lifting cylinder to discharge itself into the exhaust the
load, if heavy enough, will force the water from the front of the lowering cylinder
into the pressure pipes, but if the load is insufficient to lower in this manner then
the pressure of water is admitted to the back of the lowering cylinder and the
water from the front of that cylinder discharged into the pressure pipe, the water
from the lifting cylinder being discharged into the exhaust pipes.
In some cases I employ a piston in the lifting cylinder and a ram in the lowering
cylinder. In this arrangement the action in lifting and lowering is as follows:-
The pressure of water is admitted to the front and back ends of the lifting cylinder,
the water from the lowering cylinder being allowed to flow into the exhaust, when,
if not too heavy, the load will be lifted. For the next higher power the pressure of
water is removed from the front end of the lifting cylinder, the pressure still
remaining on the back end, and the water from the lowering cylinder being forced
into the back end of the lifting cylinder against the pressure of the water, the water
from the front end of the lifting cylinder flows into the exhaust. For the full
power of the crane the pressure of the water remains on the back end of the
lifting cylinder, and the water from the front end and from the lowering cylinder is
allowed to flow into the exhaust.
In lowering a load the pressure of water is admitted to the front end of the lifting
cylinder, and if the load to be lowered is heavy enough the water from the back of
the lifting cylinder is forced into the pressure pipe, and the lowering cylinder will
draw water from the exhaust; but if the load is not heavy enough to do this the
pressure of water is admitted to the lowering cylinder also, and the load will be
lowered.

page_text: Figure 1 is a front elevation, Figure 2 is a side elevation, and Figure 3 is a plan,
all partly in section, they show the application of my Invention to the construction
of a warehouse crane suitable to be fixed against a wall. a is the main lifting
cylinder, and b is its ram. The sheaves for the lifting chain are mounted on the
head of the ram and on the lower end of the cylinder a in the usual manner. The
chain passes around them and away to the crane jib c, and so down to the load in
the ordinary way. d, d, are the cylinders for swinging the jib.
A chain e passes
around the drum c at the foot of the jib over the guide pulleys f, f, thence around
the sheaves d, d, on the rams working in the cylinders d, and then in place of
being made fast, as they would be in ordinary practice, they are carried up and over
the guide pulleys g, g, to the sheave frame on the head of the ram b, to which they
are made fast. The three cylinders are provided with valves to admit and to draw
off the water independently to and from either cylinder, and these valves may, if
convenient, be worked by two hand chains, one to control the lifting and lowering,
and the other to control the swinging of the jib. When the lifting control chain is
first moved to start the lifting it opens the valves which admit water from the
accumulator to the two cylinders d, and if the load (being heavy) does not then rise
a further movement of the controlling chain opens the valve by which the water
The motion of the same control chain
under pressure enters the main cylinder a.
in the opposite direction closes the supply valves and opens the exhaust to allow
the water to pass out of the cylinders.
The valve gear may be so arranged that the valves of the cylinder a shall be
operated before those of the cylinders d, in which case the load if heavy will descend
whilst the supply passages to the cylinders d are still open, and will force back the
water from the cylinders d into the accumulator, from which a saving of power will
result.
According as the hand chain controlling the swinging of the jib is moved in one
or other direction it first closes or partly closes the supply valve of one or the other
of the cylinders d, which often will be sufficient to produce the motion desired, but
if not, a further movement of the control chain will cause the exhaust valve of the
same cylinder to be opened. When the loads to be lifted are so light that it is
unnecessary to admit water under pressure to the cylinder a the ram of this
cylinder in rising draws in water through a suction valve, so that the ram bis
always waterborne. In certain cases the cylinder a and ram b may be dispensed
with, but it will then be necessary to apply locking mechanism to lock one of the
lifting and one of the turning sheaves in their frames at the time of turning or
lifting.

page_text: Having thus described the nature of my said Invention, and the manner of
performing the same, I would have it understood that I do not confine myself to
the exact details described, but I claim-
The construction of hydraulic cranes in such manner that the hydraulic cylinders
and apparatus by which the crane is turned may also serve to lift or aid in lifting
loads, substantially as herein described.
In witness whereof, I, the said Robert Mills, have hereunto set my hand and
seal, this Twentieth day of September, in the year of our Lord One thousand
eight hundred and seventy-six.
ROBERT MILLS. (L.S.)