Hydro-static press.
A machine in which the pressure of a piston on a body of water of relatively small sectional area is made to propagate the force to a cylinder of multiple area, where the force is directly as the difference and the speed inversely as the difference.
Pascal (1650) demonstrated the power of a column of water in a vertical pipe inserted into a barrel.
In filling the barrel and pipe, he found the pressure to be as the hight of the column and the area of the base, as if the cask had preserved its diameter throughout the whole length of the column.
Supposing the barrel to have an area of three square feet, and the pipe of twelve feet length to have a capacity of two pints, the effective pressure of the quart of water on the heads of the cask is equal to a cylinder of water containing thirty-six cubic feet.
If a properly fitting piston of a weight equal to the quart of water be placed in the pipe, it will have the same effect as the water for which it is a substitute.
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Conway bridge hydrostatic press. |
If, instead of the mere weight of the piston, it be loaded with a weight nine times that of its own, the bursting pressure in the barrel will be tenfold greater than before.
If, instead of a weight upon the piston, a lever be placed above it, the increased force may be immensely multiplied and a power obtained which is beyond all others of equal compactness and facility of manipulation.
This is the Bramah hydraulic press.
The first one ever made is in the museum of the
Commissioners of Patents (
England), and is inscribed, “Bramah, Invt.
Et fect.
1796.”
The celebrated
Maudslay was mechanically educated in Bramah's shop.
In
N (page 1157) the operation of this machine may be readily understood.
a is a reservoir of water on which is a pump, the piston-rod
b of which is worked by the hand-lever
c. The water is conveyed by the pipe
d to the cylinder
e, where it elevates the piston
f and table
g, which rises between the guides that hold the upper plate, against which the object under pressure is driven.
The elevation of the table
g is proportionate to the quantity of water injected.
The power is proportionate to the respective areas of the pump and the cylinder
a.
Fig. 2627,
A is an elevation of the press and crosssection of the tube employed in the Conway tubular bridge, and
B a vertical section of the press and a portion of the tubing.
a is the pump piston and
b the cylinder, which is supported upon double iron girders
c c, resting on girders
d, built in the masonry.
Water is forced through the pipe
c into the cylinder by an engine of 40-horse power. The piston has a cross-head
f provided with clamps
g which hold the ends of the lifting chain links and are screwed up firmly against them.
The alternate links are notched, as shown at
h h, so as to fit into corresponding grooves in the cross-girders
i i, which are temporarily bolted to the walls
k k of the tube.
The force actually exerted by the pump in raising one end of the tube, a weight of 900 tons, was two and a quarter tons per square inch.
Three hydrostatic presses were used at the raising of the tubes of the
Menai Railroad Bridge. One of them worked at one end of the tube and two smaller ones at the other end. The larger one had a cylinder 11 inches thick and 20 inches in internal diameter.
Its lift was 6 feet. The weight of the cylinder was 16 tons, and of the machine 40 tons.
Its power was estimated as equal to that of 30,000 men. The smaller presses had rams 18 inches in diameter.
The presses stood on the summits of the piers, and lifted by means of chains having alternately eight and nine links.
The weight of a chain was 224,000 pounds. They were attached to the rams by iron cross-heads of great thickness.
The two chains passed through square holes at each end of the cross-head, and were gripped above by clamps of wrought-iron, screwed like a vise.
At the lower end, the chains were attached to the tube, or rather to lifting-frames within its extremities, by three sets of massive castiron beams, crossing one above another, and secured by wroughtiron straps passing over the upper pair and descending into the bottom cells where they were keyed.
The ends of the chains fitted under deep shoulders or notches in the lifting-frames, where they were secured by screw-bolts; these lifting-frames and beams added 448,000 pounds to the weight to be lifted.
Each of the middle tubes weighed 4,032,000 pounds (1,800 English tons), and they were lifted by successive lifts of 6 feet to a hight of 100 feet above tide-water.
The motive force was two
steam-engines of 40-horse power each, and the water was delivered through a 1/2-inch pipe into the cylinder below the ram.
That shown at
D, plate opposite page 1150, is adapted for pressing the printed sheets of books, etc. It is arranged with either one or two pumps for forcing water into the lifting-cylinder, whose piston raises the platform on which the sheets are placed.
This is kept in horizontal position by upright standards, and between it and the head of the press the sheets are compressed.
In the
sterhydraulic press of Mm. Desgoffe and
Olivier, a coil of gut-rope passing through a stuffing-
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Applications of the hydrostatic press. |
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box into the cylinder is wound upon an interior pulley, displacing part of the fluid (oil) and causing the piston to rise.
See hydraulic press,
Fig. 2617. Among the applications of the hydrostatic press may be found : —
| Accumulator. | Hydraulic slip. |
| Boiler-power. | Hydraulic spring-tester. |
| Coal-breaking jack. | Hydrostatic baling-press. |
| Crank-puller. | Hydrostatic bellows. |
| Hydraulic crane. | Jim-crow. |
| Hydraulic dock. | Pipe-prover. |
| Hydraulic elevator. | Punching-bear. |
| Hydraulic hoist. | Rail-bender. |
| Hydraulic lift. | Rail-punch. |
| Hydraulic lifting-jack. | Shaft-straightener. |
| Hydraulic platform-lift. | Ship-jack. |
| Hydraulic press. | Spring-tester. |
| Hydraulic pulling-jack. | Testing-machine. |
| Hydraulic punch. | Traversing-jack. |
| Hydraulic shaft-straightener. | Wagon-tipper. |
| Wheel-jack. |
| Hydraulic shears. | Wheel-press. |
