q 1 ¼
60
1000
pD
2 L
4t 1
p 1 þ p 2
p a
¼ 0:047
D
2 L
t 1
p 1 þ p 2
p a
ð8:23Þ
q 2 ¼ 0:047
ðD
2
À d
2
ÞL
t 2
p 1 þ p 2
p a
ð8:24Þ
where
V a1 The amount of gas consumed by driving load stroke converted into standard
gas volume under the standard condition;
V a2 The amount of gas consumed during the no-load return journey is converted
into the gas volume under the standard condition;
p a
Standard atmospheric pressure;
V 1
The working volume of the side without piston rod;
V 1
There is working volume on the side with piston rod.
p 1
Inlet pressure;
p 2
Exhaust pressure with load working stroke;
D
Piston diameter;
d
Piston rod diameter;
L
Piston stroke;
t 1 ; t 2 The time required for on-load working trip and no-load return trip.
Therefore, if the piston goes to and fro N times per minute, the theoretical value
of the volume flow rate of the gas consumed under the standard atmospheric
pressure is obtained as follows:
Q th ¼ q 1 t 1 þ q 2 t 2
ð
Þ N
ð8:25Þ
Generally, the leakage of gas in control elements (such as control valves and
pipeline systems.) and other unexpected loss of gas flow account for 35*50% of
the theoretical flow. Therefore, the actual gas required by the cylinder should be
taken as 1.5 times of the theoretical gas consumption Q th .
8.2.1.2 Dynamic Characteristics of Cylinder
In addition to the static characteristics of the cylinder as the output thrust and gas
consumption of the cylinder piston discussed above, there are also the minimum
starting pressure of the piston and the airtightness of the cylinder.
Because of the inherent physical characteristics (such as compressibility) of gas
itself, and the friction force at the inner wall of cylinder and the sealing filler of
piston rod, the dynamic characteristics of cylinder are quite different from those of
hydraulic cylinder. The dynamic characteristics of the cylinder include the starting
characteristics of the cylinder, the motion characteristics of the piston, the natural
18
8 Pneumatic Actuators, Driving Elements and Accessories
60
1000
pD
2 L
4t 1
p 1 þ p 2
p a
¼ 0:047
D
2 L
t 1
p 1 þ p 2
p a
ð8:23Þ
q 2 ¼ 0:047
ðD
2
À d
2
ÞL
t 2
p 1 þ p 2
p a
ð8:24Þ
where
V a1 The amount of gas consumed by driving load stroke converted into standard
gas volume under the standard condition;
V a2 The amount of gas consumed during the no-load return journey is converted
into the gas volume under the standard condition;
p a
Standard atmospheric pressure;
V 1
The working volume of the side without piston rod;
V 1
There is working volume on the side with piston rod.
p 1
Inlet pressure;
p 2
Exhaust pressure with load working stroke;
D
Piston diameter;
d
Piston rod diameter;
L
Piston stroke;
t 1 ; t 2 The time required for on-load working trip and no-load return trip.
Therefore, if the piston goes to and fro N times per minute, the theoretical value
of the volume flow rate of the gas consumed under the standard atmospheric
pressure is obtained as follows:
Q th ¼ q 1 t 1 þ q 2 t 2
ð
Þ N
ð8:25Þ
Generally, the leakage of gas in control elements (such as control valves and
pipeline systems.) and other unexpected loss of gas flow account for 35*50% of
the theoretical flow. Therefore, the actual gas required by the cylinder should be
taken as 1.5 times of the theoretical gas consumption Q th .
8.2.1.2 Dynamic Characteristics of Cylinder
In addition to the static characteristics of the cylinder as the output thrust and gas
consumption of the cylinder piston discussed above, there are also the minimum
starting pressure of the piston and the airtightness of the cylinder.
Because of the inherent physical characteristics (such as compressibility) of gas
itself, and the friction force at the inner wall of cylinder and the sealing filler of
piston rod, the dynamic characteristics of cylinder are quite different from those of
hydraulic cylinder. The dynamic characteristics of the cylinder include the starting
characteristics of the cylinder, the motion characteristics of the piston, the natural
18
8 Pneumatic Actuators, Driving Elements and Accessories