4) Washer(new)(manufacturing)
washers (as used with bolts, etc.) - are blanked
from coiled sheet metal with high-speed, multiple
blanking dies (2C4.) Washers can be made from
almost any metal, but hardware-store washers are
blanked from mild steel sheet, and are cleaned
(8Ald), and bright-zinc barrel-plated (8C3).
Handbook of Manufacturing Processes, James G. Bralla, p: 775
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there is no old description
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5)Pneumatics(new)(better)(transmission systems)
Figure 1.3 shows the components of a pneumatic system. The basic
actuator is again a cylinder, with maximum force on the shaft being
determined by air pressure and piston cross sectional area.
Operating pressures in pneumatic systems are generally much
lower than those in a hydraulic systems; 10 bar being typical which
will lift 10 kg cm -2 of piston area, so a 16 cm diameter piston is
required to lift the 2000 kg load specified in the previous section.
Pneumatic systems therefore require larger actuators than hydraulic
systems for the same load.
The valve delivering air to the cylinder operates in a similar way
to its hydraulic equivalent. One notable difference arises out of the
simple fact that air is free; return air is simply vented to atmosphere.
Air is drawn from the atmosphere via an air filter and raised to
required pressure by an air compressor (usually driven by an AC
motor). The air temperature is raised considerably by this compres-
sor. Air also contains a significant amount of water vapour. Before
the air can be used it must be cooled, and this results in the forma-
tion of condensation So, the air compressor must be followed by a
cooler and air treatment unit.
Compressibility of a gas makes it necessary to store a volume of
pressurised gas in a reservoir, to be drawn on by the load. Without
this reservoir, a slow exponential rise of pressure results in a similar
slow cylinder movement when the valve is first opened. The air
treatment unit is thus followed by an air reservoir.
Hydraulic systems require a pressure regulator to spill excess
fluid back to the tank, but pressure control in a hydraulic system is
much simpler. A pressure switch, fitted to the air reservoir, starts the
compressor motor when pressure falls and stops it again when pres-
sure reaches the required level.
The general impression is again one of complexity, but units in
the broken-lined box are again common to one plant or even a
whole site. Many factories produce compressed air at one central
station and distribute an air ring main to all places on the site in a
similar way to other services such as electricity, water or gas.
Hydraulics and Pneumatics
A technician's and engineer's guide
Second edition
Andrew Parr MSc., CEng., MIEE, MlnstMC , p:7
Pneumatics(old)
Pneumatics is the discipline that deals with mechanical properties of gases
such as pressure and density, and applies the principles to use compressed
gas as a source of power to solve engineering problems. The most widely
used compressed gas is air, and thus its use has become synonymous with
the term pneumatics. Hydraulics is the discipline that deals with the mechanical
properties of liquids, and applies the principles to solve engineering
problems. Gases and liquids are both fluids as opposed to solids.
Pneumatics and hydraulics are similar in many respects and often described
by the generic term fluid power.
(Peter Beater, Pneumatic Drives System Design, Modelling and Control, pg.1)
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