IMPROVEMENTS APPLICABLE TO HYDRAULIC LIFTS FOR THE PURPOSE OF ECONOMIZING POWER IN WORKING SUCH LIFTS
Year: 1877

page_text: LETTERS PATENT to James Leonard Plimpton, of Bedford Place, in the County
of Middlesex, Gentleman, for the Invention of "IMPROVEMENTS APPLICABLE
TO HYDRAULIC LIFTS FOR THE PURPOSE OF ECONOMIZING POWER IN WORKING
SUCH LIFTS."
A communication from abroad by Henry Richards Plimpton, of
Boston, in the State of Massachusetts, United States of America.
Sealed the 20th October 1877, and dated the 27th April 1877
PROVISIONAL SPECIFICATION left by the said James Leonard Plimpton at
the Office of the Commissioners of Patents on the 27th April 1877.
JAMES LEONARD PLIMPTON, of Bedford Place, in the County of Middlesex,
Gentleman. "IMPROVEMENTS APPLICABLE TO HYDRAULIC LIFTS FOR THE PURPOSE
OF ECONOMIZING POWER IN WORKING SUCH LIFTS." A communication from abroad
by Henry Richards Plimpton, of Boston, in the State of Massachusetts, United
States of America.
This Invention has for its object first to economize the power used in working
hydraulic lifts, so that the amount of power employed to first start the ram will not
have to be increased as the ram or piston rises in the cylinder, but that the amount
of power that is lost by the rising of the ram or piston shall be compensated for in
an automatic manner as it rises.
The second object of this Invention is to prevent the unnecessary use of power
in elevating a given weight, for instance (according to the present system), no
matter whether it is desired to raise 100 or 1000 lbs. weight to a given altitude, it
would be necessary to exercise the maximum force in order to elevate the smallest
quantity, thus causing a waste of power which would be sufficient to have done
nine times the amount of work it was desired to do at that moment.
The first portion of this Invention refers to the economy of hydraulic power, and
relates to a new method of developing sufficient power (as the ram or piston rises)
to overcome the extra weight which is caused by the elevation of the ram or piston.
TD AJ1

page_text: It is a well-known physical fact that any substance lying or floating in water may
be raised or moved with very much less effort than if the substance were lying in
or suspended simply in atmospheric air, the difference being equal to the weight of
water displaced by the substance lying in or on the water. By applying to the
hydraulic lift a compensating counterweight, the same force which was found
sufficient to start the ram upwards while the piston was entirely immersed in water
will be found sufficient to force the ram upwards to the utmost limit of its
capacity.
In carrying out this portion of the Invention I use any ordinary hydraulic
cylinder and ram, or piston, with its usual appurtenances, such as stuffing boxes,
valves, inlet and outlet pipes, this part of the apparatus not forming any portion of
the Invention. To the upper end of the ram or piston is attached a box or plat-
form suitable for the reception of goods. To one or both sides of this platform, or
to the centre of it, is firmly attached a strong chain, the total weight of which
should be equal to half the weight of water displaced by the ram or piston from the
cylinder when the ram is in its lowest position. This chain passes vertically
upwards and over a pulley of sufficient diameter to cause the chain to fall clear of
the platform when dropping on the other side. To the opposite end of the chain is
attached a counterbalance or dead weight which slides up and down in grooves as
the platform rises and falls, and the weight of which must be proportionate to the
dead weight of the car or platform and its appendages.
The effect of this combination would be, that as the ram or piston is raised from
the water contained within the cylinder its weight will increase in proportion to
the amount of water which replaces it within the cylinder. This increasing weight
is counterbalanced by the weight of that portion of the chain which passes over
the pulley as the platform rises, the counterbalance thus diminishing upon one side
of the pulley and increasing upon the opposite side, which tends to counteract the
decreased buoyancy of the water as the ram or piston rises out of it.
As a modification of the above mode of fixing a compensating counterweight,
the weighted portion of the chain may be supported entirely upon pulleys, and lie
in a horizontal position, one end of the chain being attached direct to the dead
weight, and the other end made fast to a rope, wire, or other light and flexible
medium of sufficient strength to support the weight of the platform to which the
rope or wire is attached. In this case the weight of the chain, which is supported
on the pullies, should be of the same weight as the water which is displaced by the
ram or piston from the cylinder, so that as the platform rises the weight of chain
passing over from the horizontal and supported position into the vertical or
descending position will counteract the increased weight of the piston or ram as it
rises from the water in the cylinder ;, or in other words, every foot that the ram rises
vertically adds an amount of weight to the vertically suspended portion of the
counterbalance, equal to the weight of water which the piston has displaced in the
cylinder; this extra weight is neutralized and a balance maintained by the chain
passing from the horizontal position where it is supported on the pullies into the
descending vertical position, where it is entirely unsupported, and the length of
chain that passes over is equal in weight to the water which replaces the ram as it
rises in the cylinder.
Should it become inconvenient to obtain a chain of the absolute weight required,
an ordinary cord or wire may be employed, but in order to give the requisite weight
to the cord or wire a number of metal rings or annular metal washers may be strung
on to the cord or wire like beads upon a thread. It is evident that by this means
any weight may be obtained as it will be only necessary to increase the diameter or
thickness of the rings or washers in order to have the desired weight.
Should it be constantly the case that the increasing length of the piston varies
the weight at regular intervals, the counterbalancing chain or weight must be so
made as to adjust itself regularly to such variations. This is effected by increasing
or diminishing the size of the links of the chain at such intervals as are necessary,
or where a greater counterbalance is required to overcome the greater dead weight

page_text: to be lifted. It is evident that the rings on the cord may also be varied in weight
so as to have the desired effect.
From the above description it will be clear that a great economy of power is
effected by the use of the compensating counterbalance chains or cords; for instead
of having to continually increase the hydraulic power as the ram rises from the
cylinder, this power is obtained by utilizing the weight of the chain, which as it
passes over the pulley reduces the weight to be lifted, and at the same time increases
by as much more the counterbalance weight which assists in lifting, thus causing,
as previously stated, a very considerable economy in the amount of hydraulic
power employed.
The second object of this Invention is to prevent the unnecessary use of or waste
of power in elevating a given weight less than the full load. In order to attain
this object it is necessary to employ a ram or piston of varying capacities, whether
such ram or piston be telescopic or otherwise, so that should it be desirable to raise
a weight of, say 100 lbs., it will not be necessary to employ power to raise, say, ten
times that amount.
One mode of constructing this improved hydraulic lift consists in arranging
several cylindrical pistons, one inside the other, the whole being contained within a
large cylinder and operated by one cock or valve. The inside piston may be worked
independently of the middle or outside one, the middle one also may be worked
without the outside one, but only in conjunction with the inside one, but the out-
side one can be worked only together with the other two. By this arrangement it
will be possible to raise a weight of, say 100 lbs., by using only the inside piston,
leaving the others in a quiescent state; but should it be necessary to raise, say
250 lbs., the inside and middle piston may be used conjointly; and if it be desirable.
to raise 700 lbs. or more, all three pistons would then be brought into use. By the
employment of this kind of lift a great waste of power will be prevented, and
thereby an economy of wear and tear will be effected. It will of course be
necessary to have bolts of sufficient power to hold the unused pistons down to
resist the strain that would be brought upon either of the pistons that are not
required to be used.
It is not essential that the pistons should work within one another in the same
cylinder, but three pistons of unequal sizes may be placed alongside of one another
in the same cylinder, or may be arranged in a triangle, or, in fact, in any way that
may be found in practice to work best. The advantage of this method would be
that the same inlet and outlet pipes would serve for all the pistons, and each piston
would be absolutely independent of the other, and a greater variety of lifting
powers obtained; for instance, say No. 1 piston is equal to 200 lbs., No. 2 is equal
to 400 lbs., and No. 3 is equal to 700 lbs. Should it be necessary to raise 900 lbs.,
Nos. 1 and 3 would be employed; if 300 lbs. were to be raised, No. 2 would be
used; if 1100 lbs., Nos. 2 and 3; and if 1300 lbs., all three would be brought into use.
In order to economize the lifting power each one of the pistons may have a counter-
balance proportionate to its lifting power attached to it. The counterbalance should
preferably be of the same kind as that described in the first part of this Speci-
fication.