Sunday, May 6, 2012

11th week Ebubekir Çantı 030070154 Part II


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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