Patent Publication Number: US-9903487-B2

Title: Valve system for pneumatic cylinders

Description:
FIELD OF THE INVENTION 
     The present invention relates to a valve system, and more particularly to a valve system for use with a pneumatic cylinder. 
     BACKGROUND OF THE INVENTION 
     Pneumatic cylinders utilize a compressed gas to produce a force and axially translate an extensible rod and piston. A single acting cylinder includes a piston which is biased in a single direction by a spring or alternative biasing member. When the pressurized gas exerts a force against the biasing member great enough to overcome a spring force, the biasing member compresses, thereby allowing the piston and extensible rod to translate. When the gas pressure decreases, the piston and extensible rod translate in the opposing direction. A double acting cylinder does not include a spring or biasing member, but instead relies upon gas pressure to move the piston and extensible rod in opposing directions, thereby requiring an influx of gas into the pneumatic cylinder to both extend and retract the piston and extensible rod. 
     SUMMARY OF THE INVENTION 
     The invention provides, in one aspect, a valve system for use with a cylinder having an extensible rod. The valve system includes a first valve assembly having a first inlet/outlet port, a check valve biased toward a closed state, the check valve having a check valve body at least partially receivable within a first port of the cylinder, a flow control valve positioned in series between the first inlet/outlet port and the check valve, and a first pilot port selectively communicable with a source of pressurized gas for opening the check valve. The valve system further includes a second valve assembly having a second inlet/outlet port, a second pilot port through which the pressurized gas must flow before being introduced to the first pilot port, and a valve body at least partially receivable within a second port of the cylinder. 
     The invention provides, in another aspect, a method of controlling actuation of an extensible rod of a cylinder. The method includes directly attaching a first valve assembly to a first port on the cylinder, directly attaching a second valve assembly to a second port on the cylinder, fluidly communicating a first pilot port of the first valve assembly and a second pilot port of the second valve assembly with a hose, directing pressurized gas through a check valve in the first valve assembly and the first cylinder port to cause the rod to undergo one of an extension operation or a retraction operation, directing pressurized gas through the second valve assembly and the second cylinder port to cause the rod to undergo the other of the extension operation or the retraction operation, and directing pressurized gas from the second valve assembly, through the hose, to the first valve assembly to release the check valve and permit pressurized gas to be exhausted from the first cylinder port and the first valve assembly. 
     Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a valve system in accordance with an embodiment of the invention for use with a cylinder. 
         FIG. 2  is a top view of the valve system and cylinder of  FIG. 1  with a schematic representation of adjoining valve structure. 
         FIG. 3  is a cross-sectional view of the valve system and cylinder of  FIG. 1 , along section  3 - 3  in  FIG. 2 , illustrating an extensible rod of the cylinder in a central position. 
         FIG. 4  is a cross-sectional view of a first valve assembly of the valve system of  FIG. 1  along section  4 - 4  in  FIG. 3 . 
         FIG. 5  is a cross-sectional view of the first valve assembly of  FIG. 1  along section  5 - 5  in  FIG. 2 . 
         FIG. 6  is a cross-sectional view of a second valve assembly of the valve system of  FIG. 1  along section  6 - 6  in  FIG. 3 . 
         FIG. 7  is a cross-sectional view of the second valve assembly of  FIG. 1  along section  7 - 7  in  FIG. 2 . 
         FIG. 8  is a cross-sectional view of the valve system and cylinder of  FIG. 1 , illustrating the cylinder during an extension operation. 
         FIG. 8A  is an enlarged view of the first valve assembly of the valve system and cylinder of  FIG. 8 . 
         FIG. 8B  is an enlarged view of the second valve assembly of the valve system and cylinder of  FIG. 8 . 
         FIG. 9  is a cross-sectional view of the valve system and cylinder of  FIG. 1 , illustrating the cylinder during a retraction operation. 
         FIG. 9A  is an enlarged view of the first valve assembly of the valve system and cylinder of  FIG. 9 . 
         FIG. 9B  is an enlarged view of the second valve assembly of the valve system and cylinder of  FIG. 9 . 
         FIG. 10  is a cross-sectional view of the valve system and cylinder of  FIG. 1 , illustrating the cylinder pressure being vented by depressing a manual release button. 
         FIG. 10A  is an enlarged view of the first valve assembly of the valve system and cylinder of  FIG. 10 . 
         FIG. 10B  is an enlarged view of the second valve assembly of the valve system and cylinder of  FIG. 10 . 
         FIG. 11  is a perspective view of a valve system in accordance with another embodiment of the invention for use with a cylinder. 
         FIG. 12  is a top view of the valve system and cylinder of  FIG. 11  with a schematic representation of adjoining valve structure. 
         FIG. 13  is a cross-sectional view of the valve system and cylinder of  FIG. 11 , along section  13 - 13  in  FIG. 12 , illustrating an extensible rod of the cylinder in a central position. 
         FIG. 14  is a cross-sectional view of the valve system and cylinder of  FIG. 11 , along section  14 - 14  in  FIG. 12 . 
         FIG. 15  is a perspective view of a second valve assembly of the valve system of  FIG. 11 . 
         FIG. 16  is a cross-sectional view of the second valve assembly along section  16 - 16  in  FIG. 15 . 
         FIG. 17  is a cross-sectional view of the second valve assembly along section  17 - 17  in  FIG. 15 . 
         FIG. 18  is a cross-sectional view of the valve system and cylinder of  FIG. 11 , illustrating the cylinder during an extension operation. 
         FIG. 18A  is an enlarged view of the first valve assembly of the valve system and cylinder of  FIG. 18 . 
         FIG. 18B  is an enlarged view of the second valve assembly of the valve system and cylinder of  FIG. 18 . 
         FIG. 19  is a cross-sectional view of the valve system and cylinder of  FIG. 11 , illustrating the cylinder during a retraction operation. 
         FIG. 19A  is an enlarged view of the first valve assembly of the valve system and cylinder of  FIG. 19 . 
         FIG. 19B  is an enlarged view of the second valve assembly of the valve system and cylinder of  FIG. 19 . 
         FIG. 20  is a cross-sectional view of the valve system and cylinder of  FIG. 11 , illustrating the cylinder pressure being vented by depressing a manual release button. 
         FIG. 20A  is an enlarged view of the first valve assembly of the valve system and cylinder of  FIG. 20 . 
         FIG. 20B  is an enlarged view of the second valve assembly of the valve system and cylinder of  FIG. 20 . 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1-3 , a valve system  10  for use with a pneumatic cylinder  12  is shown. The cylinder  12  includes a housing  14 , dual inlet/outlet ports  16 ,  18  in fluid communication with a chamber  20  defined within the housing  14 , and an extensible rod  22  ( FIG. 3 ). The extensible rod  22  includes a piston  24  that separates the chamber  20  into a first chamber portion  26  and a second chamber portion  28 , the volume of each of which is variable and dependent upon the position of the piston  24  within the chamber  20 . As described in further detail below, the valve system  10  is operable to direct pressurized gas (e.g., air) into the first chamber portion  26  or the second chamber portion  28 , respectively, to cause the rod  22  to extend or retract. 
     With reference to  FIG. 2 , the valve system  10  is in fluid communication with a supply  30  or source of pressurized gas and an exhaust  32  (e.g., a vent to atmosphere or a gas recycling system) via pneumatic lines  34 ,  36  and a three-position valve  38 . As described in further detail below, in a first position of the three-position valve  38  (shown in  FIG. 2 ), both of the first and second chamber portions  26 ,  28  of the cylinder  12  are vented, through the valve system  10 , to the exhaust  32 . In a second position ( FIG. 8 ), the three-position valve  38  and the valve system  10  direct pressurized gas from the pressurized gas source  30  to the first chamber portion  26 , while the second chamber portion  28  is vented to the exhaust  32 , causing the rod  22  to extend. In a third position ( FIG. 9 ), the three-position valve  38  and the valve system  10  direct pressurized gas from the pressurized gas source  30  to the second chamber portion  28 , while the first chamber portion  26  is vented to the exhaust  32 , causing the rod  22  to retract. 
     With reference to  FIGS. 1 and 3 , the valve system  10  includes a first valve assembly  42  fluidly connected with the rear inlet/outlet port  16  of the cylinder  12  or first cylinder port  16 , which is in fluid communication with the first chamber portion  26 . The first valve assembly  42  includes a check valve  44  ( FIG. 5 ) having a check valve body  46  directly attached and at least partially receivable within the rear inlet/outlet port  16  of the cylinder  12  ( FIG. 3 ). Specifically, the check valve body  46  includes a threaded end  48  ( FIG. 5 ) having a universal thread form compatible with multiple different thread configurations (e.g., unified, metric, square, etc.). In this manner, the first valve assembly  42  is compatible with pneumatic cylinders  12  having inlet/outlet ports with NPT, NPTF, BSPP, BSPT, JIS (PF) and JIS (PT) thread forms. The check valve body  46  also includes a seal  50  positioned adjacent the threaded end  48  that is engageable with the opening of the inlet/outlet port  16  to prevent leakage from the inlet/outlet port  16 . The seal  50  may be made from a polymer or another material. 
     With continued reference to  FIG. 5 , the check valve  44  also includes an internal seat  52  defining a circular orifice  54  coaxial with a longitudinal axis  56  of the check valve body  46 , a seal member  58  (e.g., a check ball), and a biasing member  60  (e.g., a compression spring) for biasing the ball  58  against the seat  52  to thereby close the orifice  54 . Accordingly, when the check ball  58  is in a closed position, the orifice  54  is closed and the interior of the check valve body  46  is separated into an upper cavity  62  above the valve seat  52  (from the frame of reference of  FIG. 5 ) and a lower cavity  64  beneath the valve seat  52 . The check valve body  46  includes multiple apertures  66 , each of which is oriented transverse to the longitudinal axis  56 , exposed to the upper cavity  62 , while the lower cavity  64  is directly exposed to and in fluid communication with the first chamber portion  26  of the cylinder  12  when the first valve assembly  42  is attached to the rear inlet/outlet port  16  of the cylinder  12 . 
     With continued reference to  FIG. 5 , the check valve  44  further includes a sleeve  72  positioned within the check valve body  46 , a plunger  74  that is slidable within the sleeve  72  along the longitudinal axis  56 , and a biasing member  76  (e.g., a compression spring) for biasing the plunger  74  upwards (from the frame of reference of  FIG. 5 ) and away from the check ball  58 . The sleeve  72  defines an internal chamber  78  that is sealed from the upper cavity  62  by an O-ring  80  on an exterior of the sleeve and a lip seal  84 , through which a tip  86  of the plunger  74  extends, within a stepped aperture  88  in a bottom end  90  of the sleeve  72 . The plunger  74  also includes a circular lip seal  92  on its exterior that is in sliding contact with an interior wall of the sleeve  72 , thereby separating the sleeve chamber  78  into an upper sleeve chamber  94  (from the frame of reference of  FIG. 5 ) and a lower sleeve chamber  96  in which the spring  76  is located. The volume of each of the upper and lower sleeve chambers  94 ,  96  is variable depending upon the position of the plunger  74  relative to the sleeve  72 . 
     The sleeve  72  includes an upper circumferential recess  110  on its exterior and multiple apertures  112 , each of which is oriented transverse to the longitudinal axis  56 , fluidly interconnecting the upper sleeve chamber  94  and the upper circumferential recess  110 . The check valve body  46  includes a single aperture  114 , which is also oriented transverse to the longitudinal axis  56 , having a radially inner end directly exposed to and in fluid communication with the upper circumferential recess  110  in the sleeve  72  and a radially outer end exposed to an exterior surface of the check valve body  46 . The sleeve  72  also includes a lower circumferential recess  116  on its exterior and multiple apertures  118 , each of which is oriented transverse to the longitudinal axis  56 , fluidly interconnecting the lower sleeve chamber  96  and the lower circumferential recess  116 . The check valve body  46  includes a single aperture  120 , which is also oriented transverse to the longitudinal axis  56 , having a radially inner end directly exposed to and in fluid communication with the lower circumferential recess  116  in the sleeve  72  and a radially outer end exposed to the exterior surface of the check valve body  46 . 
     With continued reference to  FIG. 5 , the check valve  44  also includes an end cap  122 , positioned above the sleeve  72 , having a cylindrical bore  124  coaxial with the longitudinal axis  56  and a manual release button  126  slidably positioned within the cylindrical bore  124 . A top end  128  of the button  126  is exposed and accessible by an operator outside the check valve body  46 , while a bottom end  130  of the button  126  is abutted with the plunger  74 . The button  126  includes an O-ring  148  on its exterior to prevent any pressurized gas within the upper sleeve chamber  94  from escaping through the cylindrical bore  124  in the end cap  122 . 
     With reference to  FIGS. 4 and 5 , the first valve assembly  42  also includes a first flow control valve  136  coupled to the check valve body  46 . The first flow control valve  136  includes an insert  138 , a valve member or needle  140 , and a one-way seal  142 . The first flow control valve  136  is received within a banjo fitting  144 , a hoop portion  146  of which is slip-fit over the check valve body  46  and overlapping the apertures  66  in the check valve body  46  exposed to the upper cavity  62 . The hoop portion  146  is stepped to seal against an O-ring  82  located above the apertures  66 , and another O-ring  150  located within a recess  152  in the check valve body  46  below the apertures  66  (from the frame of reference of  FIG. 5 ). The O-rings  82 ,  150  provide a seal between the banjo fitting  144  and the check valve body  46  to prevent unwanted leakage of the pressurized gas. The banjo fitting  144  further includes a cylindrical portion  154  that extends transverse to the longitudinal axis  56  and is hollow, defining a fitting chamber  156 , to support the insert  138 , needle  140 , and one-way seal  142 . 
     The insert  138  is tubular, including a stepped inside diameter, and is axially aligned with the cylindrical portion  154  of the banjo fitting  144 . The insert  138  includes radially extending apertures  158  that provide a fluid flow path between the fitting chamber  156  and the interior of the insert  138 . The insert  138  further includes respective openings  160  at opposite ends  162 ,  164 , with a first end  162  of the insert  138  being exposed to the upper cavity  62  of the check valve body  46 , and a second end  164  to which an end cap  98  is affixed through which the needle  140  extends. The needle  140  includes a threaded portion  166  engaged with corresponding threads on the end cap  98 , and a lock nut  168  is threaded onto the threaded portion  166  of the needle  140  for abutting the end cap  98  and rotationally constraining the needle  140  relative to the end cap  98  once the position of the needle  140  within the insert  138  is set. The needle  140  also includes a knob  170  at the distal end thereof that is graspable by an operator for setting the position of the needle  140  within the insert  138 . 
     With continued reference to  FIGS. 4 and 5 , the needle  140  includes a step  172  that rests against a seat  174  of the insert  138  when the needle  140  is in a fully closed position. Fluid flow between the needle  140  and insert  138  is prohibited when the needle  140  is in the fully closed position. The needle  140  is unseated from the seat  174  into an open position (i.e., any position except the fully closed position) by rotating the knob  170  in an opening direction, which rotates the threaded portion  166  of the needle  140  relative to the end cap  98  to translate the needle  140 . Fluid flow between the needle  140  and insert  138  is allowed when the needle  140  is in the open position and is variable based on the displacement of the step  172  relative to the seat  174 . As the distance between the step  172  and the seat  174  increases, the rate at which gas can flow between the needle  140  and the insert  138  also increases. The needle  140  also includes an O-ring  176  located between the step  172  and the threaded portion  166  that prohibits gas within the insert  138  from leaking past the end cap  98 . 
     The one-way seal  142  surrounds the insert  138  and abuts both the insert  138  and the cylindrical portion  154  of the banjo fitting  144 . The one-way seal  142  is made of a resilient material, permitting the seal to selectively deflect or deform in response to the application of a gas pressure on one side of the seal  142  to provide a flow path from the fitting chamber  156  to the check valve  44 , thereby bypassing the needle  140 . Specifically, the one-way seal  142  includes an annular rim  178  that is obliquely oriented relative to a longitudinal axis  180  of the needle  140 , such that pressurized gas acting on a first side  182  of the seal  142  is capable of deflecting the rim  178  to provide a flow path between the seal  142  and the cylindrical portion  154  of the banjo fitting  144 , and preventing such a path in the opposing direction. In the opposing direction, pressurized gas presses a second side  184  of the seal  142  (i.e., opposite the first side  182  of the seal  142 ) into contact with the cylindrical portion  154 , preventing the flow of pressurized gas therebetween. In this manner, the flow control valve  136  selectively provides a flow path between the check valve  44  and a first inlet/outlet port  186 . 
     As shown in  FIG. 4 , first valve assembly  42  further includes a first inlet/outlet port  186  coupled to the banjo fitting  144  and in communication with the fitting chamber  156 . In the illustrated embodiment, the first inlet/outlet port  186  and the banjo fitting  144  are connected by a swivel joint  188 , which permits the first inlet/outlet port  186  to be reoriented relative to the banjo fitting  144 . An O-ring  190  is located adjacent the swivel joint  188  to seal the banjo fitting  144  to the first inlet/outlet port  186 . 
     The first inlet/outlet port  186  communicates with the three position valve  38  via the hose  34  (see  FIGS. 1 and 2 ). When connected to the exhaust  32 , the first inlet/outlet port  186  functions as an outlet to allow pressurized gas to exhaust from the first chamber portion  26  of the cylinder  12 , through the check valve  44 , through the first flow control valve  136 , and through the first inlet/outlet port  186  before being discharged to the exhaust  32 . When connected to the air supply  30 , the first inlet/outlet port  186  functions as an inlet to allow pressurized gas to flow into the first inlet/outlet port  186 , through the first flow control valve  136 , and through the check valve  44  before entering the first chamber portion  26  of the cylinder  12 . With reference to FIG.  4 , the inlet/outlet port  186  includes a stepped region  192  sized to receive a quick-lock fitting  194  (e.g., a push-lock fitting) for connecting the hose  34  (i.e., from the three position valve  38 ) to the inlet/outlet port  186 . Such a push-lock fitting  194  is commercially available from Camozzi Pneumatics, Inc. of McKinney, Tex., United States of America. 
     With reference to  FIG. 5 , the first valve assembly  42  also includes a first pilot port  196  in communication with the check valve  44 . In the illustrated embodiment, the first pilot port  196  is defined by a cylindrical portion  198  of a banjo fitting  210  in which a fitting  212  (e.g., a push-lock fitting) is received. The hoop portion  214  of the banjo fitting  210  is slip-fit over the check valve body  46  and overlaps the single aperture  114  in the check valve body  46  exposed to the upper sleeve chamber  94 . As shown, the banjo fitting  210  defining the first pilot port  196  is stackable upon the banjo fitting  144  in which the first flow control valve  136  is received. The hoop portion  214  seals against the check valve body  46  via two O-rings  216 ,  218 , one located above the single aperture  114 , the other located below the single aperture  114  (from the frame of reference of  FIG. 5 ) and located within respective recesses  220 ,  222  in the check valve body  46 . The O-rings  216 ,  218  provide a seal between the banjo fitting  210  and the check valve body  46  to prevent unwanted leakage of the pressurized gas. The cylindrical portion  198  of the banjo fitting  210  extends transverse to the longitudinal axis  56  and is hollow, defining the first pilot port  196 , to support the fitting  212 . The first pilot port  196  is in communication with the single aperture  114 , and therefore the upper sleeve chamber  94 , via a cavity  208  that interconnects the hoop and cylindrical portions  214 ,  198  of the banjo fitting  210 . The fitting is sized to accept a hose or pneumatic line  206  ( FIGS. 1-3 ), the purpose of which is described in further detail below. 
     With reference to  FIGS. 1-3 and 6-7 , the valve system  10  includes a second valve assembly  224  fluidly connected with the front inlet/outlet port  18  of the cylinder  12  or second cylinder port  18 , which is in fluid communication with the second chamber portion  28 . The second valve assembly  224  includes a valve body  226  ( FIG. 7 ) directly attached and at least partially receivable within the front inlet/outlet port  18  of the cylinder  12  ( FIG. 3 ). Specifically, the valve body  226  includes a threaded end  228  ( FIG. 7 ) having a thread form compatible with multiple different thread configurations, identical to the threaded end  48  of the check valve body  46 . The valve body  226  also includes a seal  200  positioned adjacent the threaded end  228  that is engageable with the opening of the inlet/outlet port  18  to prevent leakage from the inlet/outlet port  18 . Similar to the seal  50 , the seal  200  may be made from a polymer or another material. 
     With continued reference to  FIG. 7 , the interior of the valve body  226  includes a single chamber  230  in continuous fluid communication with the second chamber portion  28  of the cylinder  12 , a second flow control valve  232 , and a second pilot port  234 . Unlike the first valve assembly  42 , the valve body  226  does not include a check valve, and therefore permits free flow of pressurized gas at all times throughout the single chamber  230  of the valve body  226 . The single chamber  230  includes a first cavity  236  having a lower end in fluid communication with the front inlet/outlet port  18  and an upper end in fluid communication with radially extending apertures  238  exposed to the outer periphery of the valve body  226 . The single chamber  230  also includes a coaxial second cavity  240  having a smaller diameter than the first cavity  236 , and a third cavity  242  that extends transverse to a longitudinal axis  202  of the valve body  226  and that is exposed to an outer periphery of the valve body  226 . 
     With reference to  FIGS. 6 and 7 , the second valve assembly  224  also includes a second flow control valve  232  coupled to the valve body  226 . Though annotated with new reference numerals, except as otherwise described, the second flow control valve  232  is identical to the first flow control valve  136 . The second flow control valve  232  includes an insert  244 , a valve member or needle  246 , and a one-way seal  248 . The second flow control valve  232  is received within a cylindrical portion  250  of a banjo fitting  252 , a hoop portion  254  of which is slip-fit over the valve body  226  and overlapping the apertures  238  in the valve body  226  exposed to the first cavity  236 . The hoop portion  254  is stepped to seal against an O-ring  256  located above the apertures  238 , and another O-ring  258  located within a recess  260  in the valve body  226  below the apertures  238  (from the frame of reference of  FIG. 7 ). The O-rings  256 ,  258  provide a seal between the banjo fitting  252  and the valve body  226  to prevent unwanted leakage of the pressurized gas. The banjo fitting  252  further includes a cylindrical portion  250  that extends transverse to the longitudinal axis  202  and is hollow, defining a fitting chamber  262 , to support the insert  244 , needle  246 , and one-way seal  248 . 
     As shown in  FIG. 6 , the second valve assembly  224  further includes a second inlet/outlet port  266  coupled to the banjo fitting  252  and in communication with the fitting chamber  262 . In the illustrated embodiment, the second inlet/outlet port  266  and the banjo fitting  252  are connected by a swivel joint  268 , which permits the second inlet/outlet port  266  to be reoriented relative to the banjo fitting  252 . An O-ring  270  is located adjacent the swivel joint  268  to seal the banjo fitting  252  to the second inlet/outlet port  266 . 
     The second inlet/outlet port  266  communicates with the three position valve  38  via the hose  36  ( FIGS. 1 and 2 ). When connected to the exhaust  32 , the second inlet/outlet port  266  functions as an outlet to allow pressurized gas to exhaust from the second chamber portion  28  of the cylinder  12 , through the single chamber  230  of the valve body  226 , through the second flow control valve  232 , and through the second inlet/outlet port  266  before being discharged to the exhaust  32 . When connected to the air supply  30 , the second inlet/outlet port  266  functions as an inlet to allow pressurized gas to flow through the second inlet/outlet port  266 , through the second flow control valve  232 , and through the single chamber  230  of the valve body  226  before reaching the second chamber portion  28  of the cylinder  12 . With reference to  FIG. 6 , the inlet/outlet port  266  includes a stepped region  272  sized to receive a quick-lock fitting  274  (e.g., a push-lock fitting) for connecting the hose  36  (i.e., from the three position valve  38 ) to the inlet/outlet port  266 . Such a push-lock fitting  274  is commercially available from Camozzi Pneumatics, Inc. of McKinney, Tex., United States of America. 
     With reference to  FIG. 7 , the second valve assembly  224  also includes a second pilot port  234  in communication with the single chamber  230 . In the illustrated embodiment, the second pilot port  234  is defined by a cylindrical portion  278  of a banjo fitting  280  in which a fitting  282  (e.g., a push-lock fitting) is received. The hoop portion  284  of the banjo fitting  280  is slip-fit over the valve body  226  and overlaps the outlets  286  of the third cavity  242 . As shown, the banjo fitting  280  defining the second pilot port  234  is stackable upon the banjo fitting  252  in which the second flow control valve  232  is received. The hoop portion  284  seals against the valve body  226  via two O-rings  288 ,  290 , one located above the outlets  286 , the other located below the outlets  286  (from the frame of reference of  FIG. 7 ) and located within respective recesses  292 ,  294  in the valve body  226 . The O-rings  288 ,  290  provide a seal between the banjo fitting  280  and the valve body  226  to prevent unwanted leakage of the pressurized gas. The hoop portion  284  is sized to provide an annular gap  296  outside the valve body  226  and between the O-rings  288 ,  290  to connect the outlets  286  of the third cavity  242 . The cylindrical portion  278  of the banjo fitting  280  extends transverse to the longitudinal axis  202  and is hollow, defining the second inlet/outlet port  266 , to support the fitting  282 . The second inlet/outlet port  282  is in communication with the third cavity  242  via a channel  298  that interconnects the hoop and cylindrical portions  284 ,  278  of the banjo fitting. The fitting  282  is sized to accept the hose or pneumatic line  206  ( FIGS. 1-3 ) described above with respect to the first pilot port  196 . 
     The valve system  10  is operable in three modes depending upon the position of the three position valve  38 : a first mode, a second mode, and a third mode. As shown in  FIGS. 8, 8A, and 8B , an extension operation is performed in a first mode. In the first mode, the three position valve  38  is shifted to the second position and connects the pressurized gas source  30  to the first valve assembly  42 , and the second valve assembly  224  to the exhaust  32 . The first inlet/outlet port  186  functions as an inlet to direct the pressurized gas toward the first flow control valve  136 . Upon entering the first banjo fitting  144  at the fitting chamber  156 , the pressurized gas acts on the first side  182  of the one-way seal  142  to inwardly deflect the rim  178  of the one-way seal  142  ( FIG. 8A ), permitting the pressurized gas to bypass the flow control valve  136  on route to the check valve  44  (arrow A 1 ). 
     Once past the flow control valve  136 , the pressurized gas enters the upper cavity  62  of the check valve body  46  via the apertures  66 . Upon the upper cavity  62  reaching a high enough pressure to overcome the spring force of the biasing member  60  and unseat the seal member  58  from the valve seat  52 , the pressurized gas flows around the seal member  58  and flows through the lower cavity  64  in the check valve body  46  on route to the first cylinder chamber or first chamber portion  26 . The increase in pressure in the first cylinder chamber  26  applies a force to the piston  24 , thereby extending the rod  22 . The rod  22  extends at a speed that is dependent upon the degree to which the second flow control valve  232  is opened (and the exhaust flow rate of the pressurized gas from the second cylinder chamber or second chamber portion  28  as metered by the second flow control valve  232 ) until the piston  24  bottoms out or stops in response to the application of a reaction force on the rod  22  equal and opposite the force applied to the piston  24  by the pressurized gas in the first cylinder chamber  26 . 
     Simultaneously with pressurized gas entering the first cylinder chamber  26  via the first valve assembly  42  (arrow A 1  in  FIG. 8A ), the pressurized gas within the second cylinder chamber  28  is exhausted through the second flow control valve  232  and the second inlet/outlet port  266  (i.e., functioning as an outlet port) on route to the exhaust  32  (arrow A 2  in  FIG. 8B ). Because the second valve assembly  224  does not include a check valve, the pressurized gas in the second cylinder chamber  28  is exhausted through the flow control valve  232  at a volumetric or mass flow rate that is dependent upon the degree to which the flow control valve  232  is opened. In other words, the greater the spacing between the step  300  on the needle  246  and the seat  302  defined on the insert  244 , the higher the flow rate that gas can be exhausted from the second chamber portion  28 , and the smaller the spacing between the step  300  on the needle  246  and the seat  302  defined on the insert  244 , the lower the flow rate that gas can be exhausted from the second chamber portion  28 . Accordingly, during the extension operation shown in  FIGS. 8, 8A, and 8B , the second flow control valve  232  meters the return of pressurized gas from the second cylinder chamber  28  to the exhaust  32 . In practical applications, the degree to which the flow control valve  232  is opened is preset and remains unchanged during operation. 
     When the extensible rod  22  has translated the desired amount, or attained an equilibrium of forces acting on it, the three position valve  38  is returned to the first position, coinciding with the second mode of operation. In the second mode, the three position valve  38  connects both of the first and second inlet/outlet ports  186 ,  266  to the exhaust. The seal member  58  is biased against the valve seat  52  to prevent the first cylinder chamber  26  from being vented to the exhaust  32 , maintaining the pressurized gas within the first cylinder chamber  26  and the resultant force acting on the piston  24  of the extensible rod  22 . However, the second cylinder chamber  28  remains vented to the exhaust  32 . The valve system  10  and cylinder  12  may be operated in the second mode, for example, when it is desired to maintain a clamping force on an object, with the rod  22  extended, but fluidly disconnect the first cylinder chamber  26  from the source  30  of pressurized gas. 
     As shown in  FIGS. 9, 9A, and 9B , a retraction operation is performed in the third mode. In the third mode, the three position valve  38  is shifted to the third position and connects the pressurized gas source  30  to the second valve assembly  224  and connects the first valve assembly  42  to the exhaust  32 . Specifically, the second inlet/outlet port  266  functions as an inlet to direct the pressurized gas toward the second flow control valve  232 . Upon entering the banjo fitting  252  at the fitting chamber  262 , the pressurized gas acts on a first side  304  of the one-way seal  248  to inwardly deflect the rim  306  of the one-way seal  248  (arrow A 3  in  FIG. 9B ), permitting the pressurized gas to bypass the second flow control valve  232  and enter the first cavity  236  of the valve body. Once in the first cavity  236 , the pressurized gas branches along two paths (designated by arrows A 4  and A 5 ). On the first path (arrow A 4 ), the pressurized gas builds pressure within the second cylinder inlet/outlet port  18  and the second cylinder chamber  28 . The increase in pressure in the second cylinder chamber  28  (i.e., applied by the pressurized gas) applies a force to the piston  24 , thereby retracting the rod  22 . The rod  22  retracts at a speed that is dependent upon the degree to which the first flow control valve  136  is opened (and the exhaust flow rate of the pressurized gas from the first cylinder chamber  26  as metered by the first flow control valve  136 ) until the piston  24  bottoms out or stops in response to the application of a reaction force on the rod  22  equal and opposite the force applied to the piston by the pressurized gas in the second cylinder chamber  28 . 
     Simultaneously, the pressurized gas continues along the second path (arrow A 5 ), which extends from the first cavity  236  of the valve body to the second pilot port  234  and the second fitting  282  (which supports a second end of the hose  206 ) via the second and third cavities  240 ,  242 . The pressurized gas enters the second end of the hose  206 , traverses the hose  206 , and exits the first end of the hose  206  to flood the upper circumferential recess  110  and the upper sleeve chamber  94  of the first valve assembly  42  (at arrow A 6 ). Pressure builds within the upper sleeve chamber  94  against the top surface of the plunger  74  until the return force of the spring  76  biasing the plunger  74  is overcome, displacing the plunger  74  along the longitudinal axis  56  until it contacts and unseats the seal member  58 , overcoming the spring force of the biasing member  60  and allowing pressurized gas in the first cylinder chamber  26  to vent to the exhaust  32  through the first flow control valve  136  as the second cylinder chamber  28  is simultaneously flooded with pressurized gas. A positive piston ratio (e.g., one that is greater than 1:1) of the plunger  74  allows the pressurized gas within the upper sleeve chamber  94  to overcome the backpressure in the first cylinder chamber  26  acting on the ball  58 . The piston ratio is the quotient of the area of the top surface of the plunger  74  divided by the area outlined by the orifice  44 . The lower sleeve chamber  96  is vented to the atmosphere via the radially extending apertures  118  through the sleeve  72 , the lower circumferential recess  116  on the outer periphery of the sleeve  72 , the aperture  120  in the banjo fitting  210  and check valve body  46 , and an axial gap  308  defined between the banjo fittings  144 ,  210 . Accordingly, additional gas pressure does not build in the lower sleeve chamber  96  as the plunger  74  is displaced downward within the sleeve  72 . Accordingly, a pneumatic pilot circuit for actuating the plunger  74  and opening the check valve  44  is directed through the second valve assembly  224  on route to the first valve assembly  42 . 
     Further, as shown in  FIGS. 10, 10A, and 10B , the plunger  74  may be manually actuated via operator input or contact with the button  126 . When an operator depresses the button  126  (e.g., with a screwdriver, with a finger, etc.), the button  126  and plunger  74  move toward the seal member  58  in unison to unseat the seal member  58  as described above, venting pressurized gas from the first cylinder chamber  26  through the flow control valve  136  along arrow A 7 , to the exhaust  32  when the valve  38  is in the first position. 
     Regardless of the method (i.e., using a pneumatic force on the plunger  74  or a physical input of force on the plunger  74  by depressing the button  126 ), once the seal member  58  is unseated, the pressurized gas within the first cylinder chamber  26  is exhausted through the first flow control valve  136  and the first inlet/outlet port  186  (i.e., functioning as an outlet port) on route to the exhaust  32  (arrow A 7 ). The pressurized gas in the first cylinder chamber  26  is exhausted through the first flow control valve  136  at a volumetric or mass flow rate that is dependent upon the degree to which the flow control valve  136  is opened. In other words, the greater the spacing between the step  172  on the needle  140  and the seat  174  defined on the insert  138 , the higher the flow rate that gas can be exhausted from the first chamber portion  26 , and the smaller the spacing between the step  172  on the needle  140  and the seat  174  defined on the insert  138 , the lower the flow rate that gas can be exhausted from the first chamber portion  26 . Accordingly, during the retraction operations shown in  FIGS. 9, 9A, 9B, 10, 10A, and 10B , the first flow control valve  136  meters the return of pressurized gas from the first cylinder chamber  26  to the exhaust  32 . In practical applications, the degree to which the flow control valve  136  is opened is preset and remains unchanged during operation. 
     When the extensible rod  22  has translated the desired amount, or attained an equilibrium of forces acting on it, the three position valve  38  is returned to the first position. As the pressure within the second valve assembly  224  and the second chamber portion  28  is exhausted, pressure within the upper sleeve chamber  94  decreases, allowing the plunger  74  and the seal member  58  to return to their biased positions. Therefore, the exhaust passage of the first chamber portion  26  past the seal member  58  is blocked, and the second cylinder chamber  28  vents to the exhaust  32  until the first and second chamber portions  26 ,  28  achieve equilibrium. 
     The valve system  10  can be tightly packaged around the cylinder  12 , requiring less space for installation of the cylinder  12  in its end-use application and reducing clutter of pneumatic hoses connected to the cylinder  12 . Specifically, by directing the pneumatic pilot circuit for actuating the plunger  74  through the second valve assembly  224 , less hose is required for plumbing the valve assemblies  42 ,  224  to the cylinder  12 , reducing the likelihood of a hose or fitting failure and the cylinder  12  going off-line within its end-use application. 
     With respect to  FIGS. 11-20B , another embodiment of a valve system is shown with like features being identified with like reference numerals incremented by one-thousand.  FIGS. 11-20B  illustrate a valve system  1010  for use with a pneumatic cylinder  1012 . The cylinder  1012  includes dual inlet/outlet ports  1016 ,  1018  in fluid communication with a chamber  1020  defined within the housing  1014 , and an extensible rod  1022  ( FIG. 13 ). The extensible rod  1022  includes a piston  1024  that separates the chamber  1020  into a first chamber portion  1026  and a second chamber portion  1028 , the volume of each of which is variable and dependent upon the position of the piston  1024  within the chamber  1020 . As described in further detail below, the valve system  1010  is operable to direct pressurized gas (e.g., air) into the first chamber portion  1026  or the second chamber portion  1028 , respectively, to cause the rod  1022  to extend or retract. 
     With reference to  FIGS. 11-17 , the valve system  1010  includes a second valve assembly  1224 , fluidly connected with the front inlet/outlet port  1018  of the cylinder  1012  or second cylinder port  1018 , which is in fluid communication with the second chamber portion  1028 . The second valve assembly  1224  includes a valve body  1226  ( FIG. 15 ) directly attached and at least partially receivable within the front inlet/outlet port  1018  of the cylinder  1012  ( FIG. 13 ). Specifically, the valve body  1226  includes a threaded end  1228  ( FIGS. 15 and 16 ) having a thread form compatible with multiple different thread configurations. The valve body  1226  also includes a seal  1200  positioned adjacent the threaded end  1228  that is engageable with the opening of the inlet/outlet port  1018  to prevent leakage from the inlet/outlet port  1018 . The seal  1200  may be made from a polymer or another material. 
     With reference to  FIGS. 16 and 17 , the interior of the valve body  1226  includes a chamber  1230  that provides fluid communication between the second chamber portion  1028  of the cylinder  1012 , a second inlet/outlet port  1266 , and a second pilot port  1234 , with the inlet/outlet port  1266  and the pilot port  1234  being separated from the second chamber portion  1028  by a second flow control valve  1232  located within the chamber  1230 . The second flow control valve  1232  includes an insert  1244 , a valve member or needle  1246 , and a one-way seal  1248 . 
     The insert  1244  is tubular, including a stepped inside diameter, and is axially aligned with a longitudinal axis  1180  of the chamber  1230 . The insert  1244  includes radially extending apertures  1310  that provide a fluid flow path between the inlet/outlet port  1266  and the interior of the insert  1244 . The insert  1244  further includes respective openings at opposite ends  1312 ,  1314 , with a first end  1312  of the insert  1244  being exposed to the second chamber portion  1028 , and a second end  1314  to which an end cap  1316  is affixed and through which the needle  1246  extends. The needle  1246  includes a threaded portion  1318  engaged with corresponding threads on the end cap  1316 , and a lock nut  1320  is threaded onto the threaded portion  1318  of the needle  1246  for abutting the end cap  1316  and rotationally constraining the needle  1246  relative to the end cap  1316  once the position of the needle  1246  within the insert  1244  is set. The needle  1246  also includes a knob  1322  at the distal end thereof that is graspable by an operator for setting the position of the needle  1246  within the insert  1244 . The needle  1246  includes a step  1300  that rests against a seat  1302  of the insert  1244  when the needle  1246  is in a fully closed position. Fluid flow between the needle  1246  and insert  1244  is prohibited when the needle  1246  is in the fully closed position. The needle  1246  is unseated from the seat  1302  into an open position (i.e., any position except the fully closed position) by rotating the knob  1322 . Fluid flow between the needle  1246  and insert  1244  is allowed when the needle  1246  is in the open position and is variable based on the displacement of the step  1300  relative to the seat  1302 . As the distance between the step  1300  and the seat  1302  increases, the rate at which gas can flow between the needle  1246  and the insert  1244  also increases. 
     The one-way seal  1248  surrounds the insert  1244  and abuts both the insert  1244  and the valve body  1226  (defining the chamber  1230 ). The one-way seal  1248  is made of a resilient material, permitting the seal to selectively deflect or deform in response to the application of a gas pressure on one side of the seal  1248  to provide a flow path from the second inlet/outlet port  1266  to the front inlet/outlet port  1018 , thereby bypassing the needle  1246 . The one-way seal  1248  does not deform or deflect in response to the application of a gas pressure on the other side of the seal  1248 , thereby preventing a gas pressure from the front inlet/outlet port  1018  from bypassing the needle  1246 . In this manner, the flow control valve  1232  selectively provides a flow path between the second inlet/outlet port  1266  and the front inlet/outlet port  1018 . 
     The chamber  1230  includes a first cavity  1236  having a lower end in fluid communication with the front inlet/outlet port  1018  and an upper end in communication with a second cavity  1240 . The second cavity  1240  is connected to the first cavity via the gap between the step  1300  and the seat  1302  when the needle  1246  is in an open position, and selectively via the one-way seal  1248  (i.e., when the one-way seal  1248  is deformed). The second cavity  1240  is delimited by the valve body  1226 , the insert  1244 , and the one-way seal  1248  and is exposed directly to the pilot port  1234  and inlet/outlet port  1266 . As shown in  FIG. 17 , the second cavity  1240  has an annular cross-sectional shape and fluidly connects the pilot port  1234  and the inlet/outlet port  1266 , such that fluid flow between the inlet/outlet port  1266  and the pilot port  1234  is permitted around the flow control valve  1232  regardless of the position of the needle  1246 . 
     As shown in  FIGS. 15 and 17 , the second inlet/outlet port  1266  is formed integrally with the valve body  1226 . The second inlet/outlet port  1266  communicates with the three position valve  1038  via the hose  1036  ( FIGS. 11 and 12 ). When connected to the exhaust  1032 , the second inlet/outlet port  1266  functions as an outlet to allow pressurized gas to exhaust from the second chamber portion  1028  of the cylinder  1012 , through the chamber  1230  of the valve body  1226 , through the second flow control valve  1232 , and through the second inlet/outlet port  1266  before being discharged to the exhaust  1032 . When connected to the air supply  1030 , the second inlet/outlet port  1266  functions as an inlet to allow pressurized gas to flow through the second inlet/outlet port  1266 , through the second flow control valve  1232 , and through the chamber  1230  of the valve body  1226  before reaching the second chamber portion  1028  of the cylinder  1012 . With reference to  FIG. 17 , the inlet/outlet port  1266  includes a stepped region  1272  sized to receive a quick-lock fitting  1274  (e.g., a push-lock fitting) for connecting the hose  1036  (i.e., from the three position valve  1038 ) to the inlet/outlet port  1266 . Such a push-lock fitting  1274  is commercially available from Camozzi Pneumatics, Inc. of McKinney, Tex., United States of America. 
     With continued reference to  FIGS. 15 and 17 , the second pilot port  1234  is also formed integrally with the valve body  1226 . The second pilot port  1234  includes a hollow cylindrical portion  1278  in which a fitting  1282  (e.g., a push-lock fitting like fitting  1274 ) is received. The fitting  1282  is sized to accept a hose or pneumatic line  1206  ( FIGS. 11-13 ), the hose  1206  additionally connected to a first pilot port  1196  ( FIG. 18A ) of a first valve assembly  1042 . 
     Like the valve system  10  described above, the valve system  1010  is operable in three modes depending upon the position of the three position valve  1038 : a first mode, a second mode, and a third mode. As shown in  FIGS. 18, 18A, and 18B , an extension operation is performed in a first mode. In the first mode, the three position valve  1038  is shifted to the second position and connects the pressurized gas source  1030  to the first valve assembly  1042 , and the second valve assembly  1224  to the exhaust  1032 . The first valve assembly  1042  functions in the same manner as described above with respect to the first mode of valve system  10 . Pressurized gas from the first valve assembly  1042  flows into the first chamber portion  1026 . The increase in pressure in the first cylinder chamber  1026  applies a force to the piston  1024 , thereby extending the rod  1022 . The rod  1022  extends at a speed that is dependent upon the degree to which the second flow control valve  1232  is opened until the piston  1024  bottoms out or stops in response to the application of a reaction force on the rod  1022  equal and opposite the force applied to the piston  1024  by the pressurized gas in the first cylinder chamber  1026 . 
     Simultaneously with pressurized gas entering the first cylinder chamber  1026  via the first valve assembly  1042  (arrow A 8  in  FIG. 18A ), the pressurized gas within the second cylinder chamber  1028  is exhausted through the second flow control valve  1232  and the second inlet/outlet port  1266  ( FIG. 14 ; i.e., functioning as an outlet port) on route to the exhaust  1032  (arrow A 9  in  FIG. 18B ). Because the second valve assembly  1224  does not include a check valve, the pressurized gas in the second cylinder chamber  1028  is exhausted through the flow control valve  1232  at a volumetric or mass flow rate that is dependent upon the degree to which the flow control valve  1232  is opened. In other words, the greater the spacing between the step  1300  on the needle  1246  and the seat  1302  defined on the insert  1244 , the higher the flow rate that gas can be exhausted from the second chamber portion  1028 , and the smaller the spacing between the step  1300  on the needle  1246  and the seat  1302  defined on the insert  1244 , the lower the flow rate that gas can be exhausted from the second chamber portion  1028 . Accordingly, during the extension operation shown in  FIGS. 18, 18A, and 18B , the second flow control valve  1232  meters the return of pressurized gas from the second cylinder chamber  1028  to the exhaust  1032 . In practical applications, the degree to which the flow control valve  1232  is opened is preset and remains unchanged during operation. 
     When the extensible rod  1022  has translated the desired amount, or attained an equilibrium of forces acting on it, the three position valve  1038  is returned to the first position, coinciding with the second mode of operation. In the second mode, the three position valve  1038  connects both of the first and second inlet/outlet ports  1186 ,  1266  ( FIG. 12 ) to the exhaust. The valve system  1010  and cylinder  1012  may be operated in the second mode, for example, when it is desired to maintain a clamping force on an object, with the rod  1022  extended, but fluidly disconnect the first cylinder chamber  1026  from the source  1030  of pressurized gas. 
     As shown in  FIGS. 19, 19A, and 19B , a retraction operation is performed in the third mode. In the third mode, the three position valve  1038  is shifted to the third position and connects the pressurized gas source  1030  to the second valve assembly  1224  and connects the first valve assembly  1042  to the exhaust  1032 . Specifically, the second inlet/outlet port  1266  functions as an inlet to direct the pressurized gas toward the second flow control valve  1232 . Upon entering the second inlet/outlet port  1266 , the pressurized gas passes to the second cavity  1240  and acts on a first side  1304  of the one-way seal  1248  to inwardly deflect the rim  1306  of the one-way seal  1248  (arrow A 10  in  FIG. 19B ), permitting the pressurized gas to bypass the second flow control valve  1232  and enter the first cavity  1236  of the valve body  1226 . Once in the first cavity  1236 , the pressurized gas builds pressure within the second cylinder inlet/outlet port  1018  and the second cylinder chamber  1028 . The increase in pressure in the second cylinder chamber  1028  (i.e., applied by the pressurized gas) applies a force to the piston  1024 , thereby retracting the rod  1022 . The rod  1022  retracts at a speed that is dependent upon the degree to which the first flow control valve  1136  is opened until the piston  1024  bottoms out or stops in response to the application of a reaction force on the rod  1022  equal and opposite the force applied to the piston by the pressurized gas in the second cylinder chamber  1028 . 
     Simultaneously, the pressurized gas continues along a second path (arrow A 11 ), which extends around the flow control valve  1232  and through the second cavity  1240  of the valve body  1226 , to the second pilot port  1234  and the second fitting  1282  (which supports a second end of the hose  1206 ). The pressurized gas enters the second end of the hose  1206 , traverses the hose  1206 , and exits the first end of the hose  1206  to displace the plunger  1074  and unseat the seal member  1058  in a manner similar to that described above with respect to the third mode of valve system  10 . Pressurized gas within the first cylinder chamber  1026  is vented to the exhaust  1032 , past the unseated seal member  1058  and through the first flow control valve  1136  (arrow A 12  in  FIG. 19A ) as the second cylinder chamber  1028  is simultaneously flooded with pressurized gas (arrow A 10 ). 
     As shown in  FIGS. 19, 19A, and 19B , when the extensible rod  1022  has translated the desired amount, or attained an equilibrium of forces acting on it, the three position valve  1038  is returned to the first position. As the pressure within the second valve assembly  1224  and the second chamber portion  1028  is exhausted, pressure within the hose  1206  decreases, allowing the plunger  1074  and the seal member  1058  to return to their biased positions. Therefore, the second cylinder chamber  1028  vents to the exhaust  1032  until the first and second chamber portions  1026 ,  1028  achieve equilibrium. 
     Further, as shown in  FIGS. 20, 20A, and 20B , the plunger  1074  may be manually actuated via operator input or contact with the button  1126 . When an operator depresses the button  1126  (e.g., with a screwdriver, with a finger, etc.), the button  1126  and plunger  1074  move toward the seal member  1058  in unison to unseat the seal member  1058  as described above, venting pressurized gas from the first cylinder chamber  1026  through the flow control valve  1136  along arrow A 12 , to the exhaust  1032  when the valve  1038  is in the first position. 
     Various features of the invention are set forth in the following claims.