Pneumatically operated valve

An improved pneumatically operated valve for controlling supply of fluid to a certain apparatus adapted to be operated for an intended purpose using the thus supplied fluid. The valve includes a valve portion on the piston rod and a flow passage of fluid is normally kept in the opened state or in the closed state by means of a the valve portion under the effect of force exerted on the piston in a predetermined direction. When any abnormal fluctuation of pressure of fluid is detected, pressurized air is introduced into the interior on the casing so ast to exert its pressure on the pistion against the aforesaid force of the piston, whereby the flow passage is shifted from the opened state to the closed state or from the closed state to the opened state. Both a normally opened type pneumatically operated valve and a normally closed type pneumatically operated valve can be constituted using parts and components having the same shape and dimension, merely by changing the direction of assembling of a certain member.

FIELD OF THE INVENTION 
The present invention relates to a pneumatically operated valve. 
BACKGROUND OF THE INVENTION 
The present invention relates to a pneumatically operated valve for 
controlling supply of a fluid to a certain apparatus adapted to be 
operated for an intended purpose using the thus supplied fluid, and more 
particularly to improvement of or relating to a pneumatically operated 
valve of the type in which a flow passage of fluid is normally kept in the 
opened state or in the closed state by means of a valve portion of the 
piston rod under the effect of a force exerted on the piston in a 
predetermined direction and. When any abnormal fluctuation of pressure of 
fluid is detected, pressurized air is introduced into the interior of the 
casing so as to allow its pressure to act on the piston against the 
aforesaid force so that the flow passage is shifted from the opened state 
to the closed state or from the closed state, to the opened state whereby 
both a normally opened type pneumatically operated valve and a normally 
closed type pneumatically operated valve can be constituted using parts 
and components having the same shape and dimension, merely by changing the 
direction of assembling of a certain member. 
DESCRIPTION OF THE PRIOR ART 
As is well known to any expert in the art, pneumatically operated valves 
are classified into two types, one of them being a normally opened type 
pneumatically operated valve in which a flow passage of fluid is normally 
kept in the opened state by means of a valve portion of the piston rod 
under the effect of a force exerted on the piston in a predetermined 
direction and in which, when any abnormal fluctuation of pressure of fluid 
is detected, the flow passage is shifted from the opened state to the 
closed state by introducing into the interior of the casing pressurized 
air which acts against the aforesaid force on the piston, and the other 
type being a normally closed type pneumatically operated valve in which a 
flow passage of fluid is normally closed with a valve portion of the 
piston under the effect of a force exerted on the piston and in which, 
when any abnormal fluctuation of pressure of fluid is detected, the flow 
passage is shifted from the closed state to the opened state by 
introducing pressurized air which acts against the aforesaid force on the 
piston. 
Both the conventional normally opened type and normally closed type 
pneumatically operated valves are constructed using parts and components 
which are almost all designed in different shape and dimension, although a 
part of them are designed in same shape and dimension. For this reason 
those parts and components can not be used in two ways as a substitute 
respectively, and this leads to problems that a large number of parts and 
components are required to build the conventional valves and their 
assembling can be achieved only by consuming many manhours because the 
assembling operation can not be performed in the same manner. 
Moreover, when a pneumatically operated valve is employed for the purpose 
of controlling flow of the pure water that is used for cleaning integrated 
circuit boards or the like, the pneumatically operated valve needs 
reliable cleaning of parts and components constituting the valve before 
their assembling in order to inhibit dust or like foreign material from 
entering therein. However, due to the fact that many members made of 
elastomeric material such as an O-ring or the like are used to build a 
valve, there is a fear of damaging or injuring said members when they are 
cleaned using supersonic or a similar intensive energy. If valve members 
such as an O-ring or the like are cleaned after their removal from the 
valve, there occurs a necessity for reassembling them after completion of 
the cleaning operation. This means increase opportunities of contact with 
valve members during the assembling operation, resulting in increased 
adhesion of dust or the like foreign material to them. Further it is 
unavoidable that members which come in contact with fluid become 
contaminated after usage for a predetermined period of time, but the 
contaminated member in conventional valves can not be easily removed 
therefrom, and therefore a cleaning operation is generally performed for 
contaminated members only with many difficulties. 
Both normally opened type and normally closed type pneumatically operated 
valves are generally constructed such that their operation of opening and 
closing is controlled by using pressurized air. For this reason the 
conventional valve requires excellently high airtightness. However, due to 
the fact that the casing in which the piston is slidably accommodated is 
designed in a cylindrical configuration of which both ends are opened, one 
of them being closed with a cover, many manhours are required for 
performing the assembling operation because of a necessity for maintaining 
airtightness in the area between the cylindrical casing and the cover, and 
the thus assembled casing causes another problem such as leakage of 
control air from the joint of this assembling, resulting in low 
airtightness of the valve. 
SUMMARY OF THE INVENTION 
Hence, the present invention has been made to obviate the above mentioned 
defects and its object resides in providing a pneumatically operated valve 
which assures that both normally opened type and normally closed type 
pneumatically operated valves are built merely by changing the direction 
of assembling of a certain member. 
Another object of the present invention is to provide a pneumatically 
operated valve which is constructed with a reduced number of parts and 
components, is assembled by way of the same steps and can be manufactured 
at a high productive efficiency and an inexpensive cost. 
Another object of the present invention is to provide a pneumatically 
operated valve which is so constructed that the piston rod is constituted 
by the combination of two separately formed members, that is, one member 
adapted to come in contact with clean fluid and having no fear of being 
damaged or injured by supersonic cleaning and the other member including 
O-rings or the like which tend to be damaged or injured during a cleaning 
operation using supersonic energy, which assures (1) that the one member 
adapted to come in contact with clean liquid is reliably cleaned by 
performing a cleaning operation separately for both the other member and 
the one member during manufacturing of the valve in a factory without 
occurrence of contamination with cleaning liquid, (2) that opportunities 
of contact with members constituting the piston rod are reduced remarkably 
during the assembling operation by simplifying the assembling operation 
and as a result preventing adhesion of dust or the like foreign material, 
(3) that both the other member and the one member are easily disconnected 
from one another so as not to hinder the cleaning operation for the 
members when the member which comes in contact with the fluid becomes 
unavoidably contaminated after usage for a predetermined period of time, 
and (4) that opportunity of contact with the members during a reassembling 
operation is minimized so as to inhibit dust or foreign material from 
being adhered to the members during the reassembling operation. 
Further, another object of the present invention is to provide a 
pneumatically operated valve serving as both a normally opened type and 
normally closed type pneumatically operated valve which is so constructed 
that the casing in which the piston is slidably accommodated is designed 
as an integral structure comprising a cylindrical portion and an upper 
wall so as to inhibit occurrence of leakage and which requires no 
assembling operation for maintaining airtightness in the area between the 
cylindrical portion and the cover. 
Still further, another object of the present invention is to provide a 
pneumatically operated valve which is operated with excellently high 
reliability and can be manufactured at a high productive efficiency and an 
inexpensive cost. 
Other objects, features and advantages of the invention will become readily 
apparent from reading of the following description which has been prepared 
in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, the present invention will be described in greater detail hereunder 
with reference to the accompanying drawings which illustrate preferred 
embodiments thereof. 
First, description will be made below as to the first embodiment of the 
invention which is applied to a normally opened type pneumatically 
operated valve with reference to FIG. 1. In the drawing reference numeral 
1 designates a piston which is slidably inserted into a cylindrical casing 
2 having an inverted U-shaped sectional configuration. The casing 2 is 
formed with an inlet port 3 on the right-hand side wall, through which 
control air is introduced thereinto. The valve is provided onto the outer 
surface of the piston 1 with two sealing portions 4 and 5 adapted to be in 
airtight contact with the inner wall of the casing 2 and an O-ring is 
fitted into each of the sealing portions 4 and 5 with an annular space 6 
located therebetween. The piston 1 is formed with a controlling passage 11 
which extends therethrough in the upwardly inclined direction, the one end 
8 of the controlling passage 11 being opened at the annular space 6 and 
the other end 10 of the same being opened at the upper surface of the 
piston 1. Further, the piston 1 is formed with an annular recess 12 which 
is located opposite to the upper opened end 10 of the controlling passage 
11. As is apparent from the drawing, the valve includes a main body 13 
which is formed with an annular recess 50 at the upper part thereof 
corresponding to the annular recess 12 of the piston 1, and a compressive 
spring 14 is accommodated between both of the annular recesses 12 and 50, 
whereby the piston 1 is normally urged in a predetermined direction (in 
the upward direction as seen in FIG. 1) under the effect of the resilient 
force of the compressive spring 14. It should be noted that an upper 
chamber A and a lower chamber B are defined by the piston 1, that is, the 
upper chamber A is located above the piston 1 and the lower chamber B is 
located below the same. The piston 1 is fixedly fitted with a piston rod 
15 by means of two snap rings 16, and the annular space 6 between both of 
the sealing portions 4 and 5 is aligned with the inlet port 3 and the 
opened end 10 of the controlling passage 11 is exposed to the upper wall 
17 of the casing 2 while the piston 1 is affected by the resilient force 
of the compressive spring 14. Once control air is introduced into the 
casing 2 through the inlet port 3, it flows into the upper chamber A via 
the controlling passage 11 in the piston 1 and thereby the latter is 
displaced toward the lower chamber B (in the downward direction as seen in 
FIG. 1) against the resilient force of the compressive spring 14. 
The casing 2 is mounted turnable relative to the main body 13 with the aid 
of a lock ring 18 which is located at the position in the proximity of the 
lower end of the casing 2. In particular, and as evident from FIG. 1, the 
casing 2 has a radially inwardly facing cylindrical surface which slidably 
engages a radially outwardly facing cylindrical surface on the main body 
13, the ring 18 being disposed in aligned annular grooves provided in 
these cylindrical surfaces. A connector 21 with a flow passage 20 formed 
therein is threadably engaged to the inner wall of the main body 13 via a 
male thread portion 22 in such a manner that the lower end part of the 
piston rod 15 enters the cylindrical hollow space of the connector 21. The 
piston rod 15 is provided with a valve portion 23 at the lowermost end 
which is orientated toward a valve seat 24 in the flow passage 20 through 
which the controlling medium flows for an intended purpose. It should be 
noted that the position of the valve portion 23 is so determined that the 
flow passage 20 is normally not closed with it. 
Refering to FIG. 1 again, the piston rod 15 is constituted by the 
combination of one member 25 corresponding to the lower part and the other 
member 26 corresponding to the upper part thereof, and a part of the one 
member 25 is covered with a bellows 27 in order to protect the controlling 
medium flowing through the flow passage 20 from contamination which may be 
caused by contact with the one member 25 of the piston rod 15. 
Specifically, the lower end of the bellows 27 is fixedly attached to the 
flange portion 28 projecting from the one member 25, in such a manner that 
the piston rod 15 is freely displaced up and down within the bellows 27. 
The upper end of the latter is fixedly attached also to a bellows flange 
30 which is inserted and fixed in the space defined between the main body 
13 and the connecter 21, whereby the one member 25 of the piston rod 15 is 
fully surrounded by the bellows 27. Connecting of the one member 25 to the 
other member 26 is effected in the following manner. The other member 26 
is provided with a plurality of engagement balls 32 which are accommodated 
in holes in an engagement sleeve 31 projected downwardly of the lower end 
thereof, and the one member 25 is connected with the other member 26 with 
the aid balls the engagement of 32 in that the upper end of the other 
member 25 is inserted within the sleeve 31 of the other member 26. 
In the illustrated case an air port 33 is drilled through the left-hand 
side wall of the casing 2 in order that air is introduced into or 
discharged from the interior of the casing 2 therethrough as the piston is 
displaced upwardly or downwardly. However, an air port such as the air 
port 33 is not always required, particularly in the case where the piston 
1 has a short distance of displacement. 
As will be readily apparent from the above description, the valve portion 
23 of the piston rod 15 assumes the position where the flow passage 20 of 
the controlling medium is normally opened under the effect of the 
resilient force of the compressive spring 14 which is exerted on the 
piston 1. If any abnormal fluctuation of pressure of the controlling 
medium is detected, pressurized air is introduced into the upper chamber A 
via the inlet port 3 and the controlling passage 11, whereby the piston 1 
is displaced downwardly against the resilient force of the compressive 
spring 14 until the valve seat 24 in the flow passage 20 is closed with 
the valve portion 23. 
The present invention has been described above with respect to the 
embodiment where it is applied to a normally opened type pneumatically 
operated valve, but it should not be limited only to this. Alternatively, 
it may be applied to a normally closed type pneumatically operated valve. 
Hence, description will be made below as to the second embodiment of the 
invention which is applied to this normally closed type valve with 
reference to FIG. 2. In this embodiment, securing of the piston 1 to the 
piston rod 15 is achieved in a reverse orientation relative to the 
foregoing embodiment which is concerned with a normally opened type valve. 
Specifically, the piston 1 is fixedly fitted onto the piston rod upside 
down by means of the snap rings 16 and a compressive spring 14 is 
accommodated in the space as defined between the annular recess 12 of the 
piston 1 and the upper wall 17 of the casing 2 while it is exposed to the 
upper chamber A. The other end 10 of the controlling passage 11 is opened 
toward the lower chamber B which is located below the piston 1, and the 
spring 14 urges the piston downwardly so that the valve portion 23 is 
maintaned in the normally closed state in which it comes in contact with 
the valve seat of the flow passage 20. When any abnormal fluctuation of 
pressure of the flowing medium flowing into the normally closed type valve 
is detected, control air is introduced into the lower chamber B via the 
inlet port 3 and the controlling passage 11 and thereby the piston 1 is 
displaced toward the upper wall 17 of the casing 2 against the resilient 
force of the compressive spring 14, which is accommodated between the 
annular recess 12 and the upper wall 17. As a result, the flow passage 20 
is opened and the valve is shifted from the closed state to the opened 
state. It should be noted that same or similar parts and components as 
those in the first embodiment are identified by the same reference 
numerals and therefore their repeated description will not be required. 
As will be readily apparent from comparison between FIGS. 1 and 2, the 
present invention consists in that a distance between the lower end of the 
piston 1 and the upper end of the main body 13, in the normally assembled 
state where the piston 1 is fixedly fitted onto the piston rod 15 and the 
compressive spring 14 is accommodated between the upper annular recess 12 
and the lower annular recess 50 as a normally opened type valve, that is, 
the size of the lower chamber B as measured in the vertical direction in 
FIG. 1, is the same in dimension as a distance between the upper end of 
the piston 1 and the upper wall 17 of the casing 2 in the reversely 
assembled state where the compressive spring 14 is accommodated between 
the annular recess 12 and the upper wall 17 of the casing 2 as a normally 
closed type valve, that is, the size of the upper chamber A in FIG. 2. 
Moreover, the compressive spring 14 employed for both the normally opened 
type valve and the normally closed type valve is designed with the same 
dimensions and in the same configuration. However, it should of course be 
understood that the compressive spring 14 for the normally opened type 
valve is designed in a different manner from that for the normally closed 
type valve in dependence on many factors such as the purpose of 
controlling the operation of a flowing medium, the pressure of fluid 
introduced into the flowing passage 20, or the like, and the difference 
therebetween can be properly compensated in accordance with the present 
invention, as required. 
Incidentally, the terms "upper" and "lower" as seen in the specification 
represent the positional terms "upper" and "lower" relative to the 
drawings and therefore they are not intended to strictly define the 
content or the scope of the invention. In some practical case when the 
pneumatically operated valve of the invention is used, "upper" and "lower" 
positions become "lower" and "upper" position or "fore" and "rear" 
positions or "left" and "right" positions in dependence on how the valve 
is mounted or arranged for a certain purpose. It should of course be 
considered that such a positional change or shift as mentioned above is 
included within the scope of the invention without any departure from the 
spirit thereof. 
Since the pneumatically operated valve of the invention is so constructed 
that, when the piston 1 is fitted onto the piston rod 15 in the normally 
assembled state, control air is introduced toward the one surface of the 
piston 1 via the inlet port while the one surface of the piston 1 and the 
other opened end 10 of the controlling passage 11 assume their normal 
position and, when the piston 1 is fitted onto the piston rod 15 in the 
reversely assembled state, control air is introduced toward the one 
surface of the piston 1 via the inlet port while the one surface of the 
piston 1 and the other opened end 11 of the controlling passage 10 assume 
their reverse position, it is assured that both a normally opened type 
pneumatically operated valve and a normally closed type pneumatically 
operated valve are constituted with the use of same parts and components, 
merely by changing the direction of fitting of the piston 1 onto the 
piston rod 15. This leads to advantageous features in that the number of 
parts and components can be reduced remarkably compared with the 
conventional valve and an assembling operation can be performed by way of 
the same steps. As a result, the valve of the invention can be 
manufactured at a high productive efficiency and an inexpensive cost. 
Further, since the piston 1 includes a plurality of sealing portions over 
the outer wall which are spaced away from one another, it is assured that 
the piston 1 comes in contact with the inside wall of the casing 2 at 
plural positions and thereby it is held stably within the casing 2 without 
any occurrence of rattling movement or a like malfunction during sliding 
of the piston 1. Thus, a pneumatically operated valve having excellently 
high operational reliability has been provided in accordance with the 
present invention. 
Next, description will be made below as to how the one member 25 is 
operatively connected to the other member 26 with reference to FIGS. 3 and 
4. 
The other member 26 has an engagement sleeve 31 projected therefrom toward 
the one member 25 and another sleeve 52 is slidably fitted onto the 
engagement sleeve 31. As is apparent from the drawing, an engagement 
flange 51 is made integral with the sleeve 52 which is slidably fitted 
onto the engagement sleeve 31, and the sleeve 52 is urged toward the one 
member 25 under the effect of the resilient force of a coil spring 53. The 
opening through the sleeve 52 is formed with an enlarged portion 54 at the 
lower end part, of which the inner diameter is dimensioned larger than 
that of the rest of the opening through the sleeve 52 and the enlarged 
portion 54 is connected to a central portion 55 of the opening located at 
the middle area of the sleeve 52 and closely engaging the engagement 
sleeve 31 via an inclined part 63. On the other hand, the sleeve 52 is 
formed with an insert recess 64 at the upper end into which the spring 53 
is inserted in such a manner that its upper end abuts against the bottom 
surface of a flange 65 of the other member 26. Further, the engagement 
sleeve 31 has a plurality of holes 56 formed around the periphery thereof 
in a spaced relation as seen in the peripheral direction and an engagement 
ball 32 having an outer diameter appreciably smaller than the inner 
diameter of the outer part 56a of the hole 56 but appreciably larger than 
the inner diameter of the inner part 56b of the same is fitted into each 
of the hole 56. To inhibit the engagement balls 32 from being projected 
inwardly into the engagement sleeve 32 after they are fitted into the 
holes 56, an insert collar 58 is previously fitted into the engagement 
sleeve 31 at the shown position. Obviously, the insert collar 58 is 
adapted to slide within the engagement sleeve 31. To this end, as shown in 
FIG. 2, the engagement balls 32 are projected outwardly of the holes 56 
but not inwardly of the same, whereby they are partially accommodated 
within the enlarged portion 54 of the sleeve 52. On the other hand, the 
one member 25 includes an engagement stem 60 on the upper end thereof 
which is projected therefrom toward the other member 26 to slidably move 
the insert collar 58 as it is inserted into the engagement sleeve 31. The 
engagement stem 60 has formed on the outer surface in a peripheral 
direction an annular engagement recess or groove 61 into which enters the 
balls 32 projected inwardly from the holes 56 and the position of the 
groove 61 is so determined that the groove 61 is located in alignment with 
the holes 56 when the engagement stem 60 is fitted into the engagement 
sleeve 31 has displaced the insert collar 58 upwardly to the position away 
from the holes 56 by the thrusting operation. On completion of fitting of 
the engagement stem 60, the engagement balls 31 are ready to project 
inwardly of the hole 56. At this moment the sleeve 52 is forcibly 
depressed under the effect of the resilient force of the spring 53 and the 
inclined part 63 of the sleeve 52 displaces the engagement balls 32 
inwardly while the depressing portion of the same inhibits the said balls 
32 from being displaced outwardly. Thus, the one member 25 is operatively 
connected to the other member 26 as shown in FIG. 4 by displacing the 
engagement balls 32 inwardly on completion of downward movement of the 
sleeve 52 along the outer surface of the engagement sleeve 31 in the 
above-described manner. If necessary, the one member 25 can be 
disconnected from the other member 26 as shown in FIG. 3 by displacing the 
engagement balls 32 to the inoperative position while the sleeve 52 is 
displaced upwardly against the resilient force of the spring 53. 
Before, the assembling operation is performed for the piston rod 15, it is 
required first that the one member 25 and the other member 26 are cleaned 
separately. It should be noted that cleaning is carefully effected for the 
one member 25 which comes in direct contact with clean fluid, whereas 
cleaning is effected for the other member 26 in such a manner that the 
sealing portions 4 and 5 in the form of O-rings are not damaged or injured 
during the cleaning operation. After completion of cleaning of the one 
member 25, the engagement stem 60 of the said member 25 is fitted into the 
engagement sleeve 31 of the other member 26 and thereby the insert collar 
58 is slidably displaced upwardly by means of the engagement stem 60 until 
the insert collar 58 is parted away from the engagement balls 32. Now, the 
balls 32 are ready to move inwardly. As the sleeve 52 is slidably 
displaced downwardly under the effect of the resilient force of the spring 
53, the engagement balls 32 are caused to partially enter the annular 
engagement groove 61 of the engagement stem 60 under the force of the 
depressed portion 55 while the residual part of the engagement balls 32 is 
retained in the holes 56. As a result, the one member 25 is operatively 
connected to the other member 26 by way of the engagement balls 32. This 
means that assembling of the piston rod 15 can be automatically achieved 
with the aid of a cleaned automatic machine without any necessity for 
manual contact with the one member 25 and the other member 26. The 
assembling is completed by threadably engaging the main body 13 to the 
connector 21. 
When it is found that the bellows 27 and other parts become contaminated 
after their usage for a predetermined period of time, the one member 25 is 
disconnected from the other member 26 so that they are ready to be 
cleaned. Specifically, disconnecting of the one member 25 from the other 
member 26 is carried out by way of the steps of disengaging the connector 
21 from the thread portion 22 of the main body 13, fitting to the 
engagement flange 51 of the sleeve 52 a suitable tool which is inserted 
through the upper end opening of the bellows flange 30, slidably 
displacing the sleeve 52 upwardly against the resilient force of the 
spring 53 with the aid of the tool, fitting another suitable tool to the 
insert collar 8 to displace the said collar 58 downwardly to the position 
where it is located in alignment with the holes 56, and then causing the 
engagement balls 32 to move toward the enlarged portion 54 which holds 
outwardly the balls 32 in the sleeve 52. After completion of disconnecting 
operation in that way both the one member 25 and the other member 26 can 
be cleaned separately. Accordingly, in the case where members adapted to 
come in contact with fluid become contaminated unavoidably after usage for 
a predetermined period of time, the one member 25 and the bellows 27 which 
are contaminated with foreign material in the flowing fluid can be cleaned 
after separating the one member 25 from the other member. As a result, the 
one member 25 and the bellows 27 are always kept clean. 
In the illustrated embodiments the valve is so constructed that the other 
member 26 includes an engagement sleeve 31 and the one member 25 includes 
an engagement stem 60. However, the present invention should not be 
limited only to this. Alternatively, the valve may be so constructed that 
the one member 25 includes an engagement sleeve 31 and the other mamber 26 
includes an engagement stem 60 in a reverse manner without any recognition 
of difference in function and effectiveness. 
As described above, the present invention involves the other member 26, 
including the piston rod 15 and O-rings which tend to be easily damaged or 
injured by supersonic cleaning, being designed separate from the one 
member 25 adapted to come in contact with clean flowing medium but not 
including O-rings or the like which tend to be damaged or injured by 
supersonic cleaning. Thus, during manufacturing of the valve, the cleaning 
operation is performed separately for the one member 25 and the other 
member 26. This leads to a characterizing feature in that the one member 
adapted to come in contact with a clean flowing medium can be cleaned 
reliably without any possibility of causing contamination after completion 
of the cleaning operation. Other characterizing features of the invention 
are that assembling is achieved simply and the occurrence of contact with 
the parts and components constituting the piston during the assembling 
operation is minimized and the possibility of causing adhesion of dust or 
the like foreign material to both the one and the other members during the 
assembling operation is reduced substantially. Further, since the one 
member 25 can be easily disconnected from the other member 26 by sliding 
movement of the sleeve, the one member 25 which becomes unavoidably 
contaminated according to the contact with flowing the medium can be 
cleaned while the other member 26 is disconnected therefrom. Thus, the one 
member 25 is always kept in the cleaned state. When the engagement balls 
are held in the outwardly displaced state by means of the insert collar 
during the cleaning operation before the assembling operation, there does 
not occur protrusion of the engagement balls into the joint area where the 
one member 25 is operatively connected to the other member 26. After 
completion of the cleaning operation, either of the one member 25 and the 
other member 26 is fitted into the engagement sleeve and thereby the 
insert collar is slidably displaced upwardly in the engagement sleeve 
until the engagement balls are released from the holding state, resulting 
in the engagement balls being protruded into the engagement sleeve. This 
means that the assembling operation can be performed by using a cleaned 
automatic machine without any necessity for manual contact with the one 
member 25 and the other member 26, contact of the first member with parts 
and components constituting the piston during assembling operation is 
minimized, and adhesion of dust or the like foreign material to the said 
parts and components during assembling operation is prevented effectively. 
As will be readily apparent from the above description, the valve of the 
invention is so constructed that a casing 2 with a piston 1 slidably 
accommodated therein is constituted by the combination of a cylindrical 
portion and an upper wall 17 in an integral structure. For this reason 
there is no necessity for performing the assembling operation under the 
airtight condition as will be seen with the conventional valve which is 
designed such that the cylindrical body is separate from the cover. Other 
advantageous features of the invention are that manhours required for the 
assembling operation can be reduced remarkably, airtight sealing members 
such as O-rings or the like are not required for the casing area, and more 
reliably airtightness is assured than with the conventional valve 
including a cover. Further, since the casing 2 is turnably mounted on the 
main body 13 with the aid of the lock ring 18, the inlet port 3 through 
which control air is introduced into the interior of the casing can freely 
assume any orientation within the range of 360 degrees. Thus, connection 
of the valve of the invention to a control apparatus (not shown) can be 
achieved without any restriction with respect to orientation of the inlet 
port.