At-mos-pher′ic Ham′mer.
A power-hammer driven by the force of compressed air.
In some cases the air is employed merely to lift the hammer; in other cases air is also employed as an adjunct in the effective stroke.
In the latter case the operation is much like that of the steam-hammer, the main difference being in the substitution of air for steam.
In
Hague's English patent some forty years since, an atmospheric hammer is shown, in which the helve is raised by the pressure of the atmosphere beneath a piston above the hammer-helve, the air being exhausted from above the piston by means of a pump; the hammer falling by its own weight when the air is admitted above the piston.
In
Fig. 409,
a b is the hammer turning upon the fulcrum at
b; c the anvil;
d a cylinder situated immediately over the hammer;
c the piston connected with the hammer by the bar
f and the slings
g, h a slide-valve worked by the lever
l, which is struck by a pin on the bar
f when the piston arrives at the top of the cylinder, depressing the valve so as to shut off communication with the air-pump and admit atmospheric air above the piston, permitting the hammer and piston to fall by their own weight.
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Hague's atmospheric hammer. |
Towards the close of the descent, the hammer, by means of a line attached to it and to the lever
l, reverses the position of the latter and of the slidevalve, thus re-opening the communication between the cylinder and the air-pump.
k is the pipe leading from the air-pump to the cylinder;
m is a cock for shutting off the communication with the air-pump when the hammer is not at work;
n n are spanners for opening and shutting the cock.
The atmospheric hammer (
Fig. 410) has an airpump and hammer combined in the same frame.
c is the band-wheel which derives its motion from the motor, — steam or water, as the case may be.
v is the pitman, and
p the piston operated by a wrist on the band-wheel
e and condensing the air in the cylinder
o. The compressed air is stored in a reservoir
a b, and conducted to the valve-chamber.
In this chamber are a slide-valve
k and stationary valve
d′ d′, the former operated by the valve-rod
w from the friction-wheels
y d.
The head of the hammer
h is attached to a piston
g, which works in the cylinder
f, into which air is admitted — like steam to a double-acting steamengine — alternately above and below the piston.
The friction-wheel
U is spline-keyed upon the shaft
[
179]
d, and is adjustable upon the latter longitudinally, so that its perimeter shall come in contact with the under side of the wheel
y at points more or less distant from the axis of the last-mentioned wheel.
In this way the valve is made to admit more or less air to the cylinder according to the force required and the duty to be performed.
If the wheel
b′ be near the center of wheel
y, hut little motion is imparted, the stroke is quick, and the blow light; but if the wheel
U is carried nearer to the periphery of the wheel
y, the hammer is slower in its motion, and a more forcible blow is given.
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Atmospheric hammer. |
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Atmospheric hammer. |
The valve-plate
d′ d′ is adjustable, but not involved in the active motions of the machine.
Its adjustment affects the area of opening in the air inductionvalve ports.
The stopcock
t is an escape for air when required.
j are hammer and anvil faces, respectively.
In another example (
Fig. 411) the hammer is reciprocated by pitman connection
K to a wrist on a crankshaft
C, operated by a band on wheel
N. The hight of the hammer
F above the anvil is graduated by the adjustment of its pistonrod
I; and its stroke by the adjustment of the wrist as the crank-shaft.
B is the standard of the frame.
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Pneumatic hammer. |
The hammer (
Fig. 412) derives the decision of its blow from the force of compressed air. The hammer-head is atatched to a piston
B moving in a cylinder
F, the latter being connected by a pitman
D to a crank-wheel
E rotated by the motor.
As the cylinder ascends, air enters the holes in the cylinder, and the air being compressed below the piston, the hammer is lifted.
As the cylinder descends, air is compressed above the piston, and is stored up to produce a sudden blow, by instant expansion after the crank and connecting-rod turn the bottom center.
