Abstract:
A circuit ( 10 ) for operating a bi-directional air motor ( 12 ) of a valve closure system for enabling a tank valve to be discretionally operated to either open or closed condition either at the tank by attending personnel or from a remote location, with the capability of closing the tank valve in the event of emergency from a remote location in the absence of attending personnel. The circuit can be constructed using two commercially available valve assemblies (( 24, 26 ).

Description:
REFERENCE TO RELATED APPLICATION AND PRIORITY CLAIM 
   This application derives from the following commonly owned patent application, the priority of which is expressly claimed: Provisional Application No. 60/430,490, filed on 02 Dec. 2002 now abandoned in the names of RICHARD FORTINO and DAVID N. MANIEZ JR. 

   FIELD OF THE INVENTION 
   This invention relates generally to valve closure systems that comprise a motor for turning a rotary actuator of a shut-off valve to operate the valve from open to closed. Such valve closure systems allow valves of vessels, such as cylinders and containers, that hold fluids, such as industrial gases for example, to be quickly closed from a remote location. More particularly, the invention relates to an improvement for enabling a motor that is capable of bi-directional operation to be discretionally operated to either open or close the valve while retaining the ability to quickly close the valve from a remote location. 
   BACKGROUND OF THE INVENTION 
   Examples of valve closure systems to which principles of the present invention may be applied are illustrated in commonly owned U.S. patent application Ser. Nos. 10/418,693 and 10/418,691, filed 18 Apr. 2003, which are incorporated herein by reference. The inventive principles may also be applied to various other valve closure systems. 
   In certain environments, it may be desirable for a valve closure system to be configured such that when installed on an open shut-off valve of a cylinder or container, it is capable of operating only to close the valve. When so configured, such a valve closure system needs to be removed from the valve before the valve can be re-opened. Removal is typically accomplished by attending personnel. Removal of a valve closure system may be inconvenient and/or time-consuming and if the system has appreciable mass, the task of removing it may be burdensome to attending personnel. 
   In those cases it may be preferable to enable the attending personnel to re-open the valve without having to remove the closure system from the shut-off valve. But when a valve closure system is enabled to open and close a shut-off valve under control of attending personnel, the ability to assure closure of an open valve from a remote location in the absence of attending personnel on the scene may continue to be required, especially where hazardous fluids may be escaping, and assurance of prompt valve closure is needed. 
   SUMMARY OF THE INVENTION 
   The present invention relates to an improvement for enabling a bi-directional motor of a valve closure system to be discretionally operated to either open or close a valve on which the system is installed, while retaining the ability to close an open valve from a remote location in the absence of attending personnel on the scene. 
   The invention endows a valve closure system with the ability to re-open a closed shut-off valve without the need to remove the closure system from the valve. 
   A presently preferred embodiment of the invention that will be described herein comprises two commercially available valves connected in a novel pneumatic circuit with a bi-directional, i.e. reversible, air motor of the closure system. The two valves are adapted to be connected to on-site pneumatic power. 
   One of the two valves is a selector valve comprising an operator that is selectively operable from a stand-by neutral position to a first position to apply air from the on-site source “shop air” or “plant air”) to a first inlet port of the air motor when the shut-off valve on which the closure system is mounted is to be operated from open to closed, and to a second position to apply air from the on-site source to a second inlet port of the air motor when the shut-off valve is to be operated from closed to open. In the stand-by position, the selector valve applies no air to either inlet port of the air motor. In the disclosed preferred embodiment, the selector valve operator is a manual one intended to be operated manually by on-site personnel. 
   The other of the two valves is a three-port directional check valve that is interposed between a source of on-site “emergency air”, a first outlet port of the selector valve, and the first inlet port of the air motor. 
   The air motor has an exhaust outlet port through which air is exhausted after having passed through the motor from either of its inlet ports. 
   The selector valve also has a second outlet port communicated to the second inlet port of the air motor, an inlet port communicated to “plant air”, and two exhaust ports. 
   Accordingly, one general aspect of the invention relates to a circuit for operating a valve closure system that has an air motor for turning a handle of a tank valve. The circuit comprises a first valve that has a first port for connection to an air source and a second port, and that is selectively operable to a first position for closing the first port to the second port and to a second position for opening the first port to the second port. The circuit further comprises a second valve that has a first port connected to the second port of the first valve, a second port for connection to a port of the air motor that operates the air motor, and a third port for connection to an emergency air source, and that, in the absence of delivery of emergency air to the third port, opens the first port to the second port to allow bi-directional airflow between its first port and its second port while closing the third port to both its first and second ports, and upon delivery of emergency air to the third port forces the third port to open to its second port regardless of whether its second port is open or closed to its first port. 
   Another general aspect relates to a valve circuit for operating a valve closure system that has an air motor for turning a handle of a tank valve. The valve circuit comprises a non-emergency air port for connection to a non-emergency air source, an emergency air port for connection to an emergency air source, and an outlet port for connection to a port of the air motor that operates the air motor. A valve arrangement operatively relates the non-emergency air port, the emergency air port, and the outlet port and comprises a first valve mechanism that is selectively operable to a first position for causing air from the non-emergency air port to be delivered to the outlet port to operate the air motor in the absence of emergency air being delivered to the emergency air port, and to a second position that does not cause delivery of air from the non-emergency air port to the outlet port. The valve arrangement further comprises a second valve mechanism that upon delivery of emergency air to the emergency air port forces the outlet port open to the emergency air port regardless of whether the first valve mechanism is in its first position or its second position. 
   Still another general aspect relates to a valve closure system comprising an air motor for turning a handle of a tank valve and a circuit for operating the air motor. The circuit comprises a) a non-emergency air port for connection to a non-emergency air source, b) an emergency air port for connection to an emergency air source, c) an outlet port for connection to a port of the air motor that operates the air motor, d) a valve arrangement for operatively relating the non-emergency air port, the emergency air port, and the outlet port. The valve arrangement comprises e) a first valve mechanism that is selectively operable to a first position for causing air from the non-emergency air port to be delivered to the outlet port to operate the air motor in the absence of emergency air being delivered to the emergency air port, and to a second position that does not cause delivery of air from the non-emergency air port to the outlet port, and f) a second valve mechanism that upon delivery of emergency air to the emergency air port forces the outlet port open to the emergency air port regardless of whether the first valve mechanism is in its first position or its second position. 
   Still another general aspect relates to a valve closure system comprising a bi-directional air motor operable in one sense for turning a handle of a tank valve to operate the tank valve from open to closed and in an opposite sense for turning the handle to operate the tank valve from closed to open. The motor has a first port for operating the motor in the one sense, a second port for operating the motor in the opposite sense, and an exhaust port for exhausting air delivered to either the first or second port. A circuit for operating the air motor comprises a) a non-emergency air port for connection to a non-emergency air source, b) an emergency air port for connection to an emergency air source, c) an outlet port for connection to the first port of the air motor, and d) a valve arrangement for operatively relating the non-emergency air port, the emergency air port, and the outlet port. The valve arrangement is operable e) to a condition that causes air from the non-emergency air port to be delivered to the first port of the air motor, but not the second port of the air motor, in the absence of emergency air being delivered to the emergency air port, f) to a condition that causes air from the non-emergency air port to be delivered to the second port of the air motor, but not the first port of the air motor, in the absence of emergency air being delivered to the emergency air port, g) to a condition that does not cause delivery of air from the non-emergency air port to either the first or second port of the air motor, and h) to a condition that upon delivery of emergency air to the emergency air port causes air from the emergency air port to be delivered to the first port of the air motor. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The accompanying drawing, which is incorporated herein and constitutes part of this disclosure, illustrates a presently preferred embodiment of the invention, and together with the written description given herein discloses principles of the invention in accordance with a best mode contemplated at this time for carrying out the invention. 
       FIG. 1  is a schematic diagram of a pneumatic circuit associated with the air motor of a valve closure system in accordance with principles of the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a presently preferred embodiment of pneumatic circuit  10  associated with an air motor  12  of a valve closure system  14  in accordance with principles of the present invention. Full detail of valve closure system  14  may be obtained from the referenced provisional patent application identified above and incorporated herein. When installed on a shut-off valve, closure system  14  is effective to turn an actuator, such as a handle, of the shut-off valve when motor  12  is operated. For example, motor  12  comprises a shaft  16  that can be coupled via a suitable adapter or coupling with the shut-off valve handle to rotate the handle about an axis coincident with that of shaft  16 . 
   Air motor  12  is a commercially available, bi-directional, i.e. reversible, device that has two inlet ports  18 ,  20  and an exhaust port  22 . When air under pressure is supplied to port  18 , air motor  12  turns shaft  16  in a clockwise sense about the shaft axis, with the air being exhausted through port  22  after having passed through the motor. When air under pressure is supplied to port  20 , air motor  12  turns shaft  16  in a counterclockwise sense about the shaft axis, with the air being exhausted through port  22  after having passed through the motor. When valve closure system  14  is operatively coupled with a shut-off valve, motor shaft  16  rotation in a clockwise sense will operate the shut-off valve, if open, from open to closed, and rotation of motor shaft  16  in a counterclockwise sense will operate the shut-off valve, if closed, from closed to open. 
   Circuit  10  comprises two commercially available valves  24 ,  26  connected in circuit with air motor  12 . Valves  24 ,  26  are adapted to be connected to on-site pneumatic power for operating motor  12 . 
   Valve  24  is a selector valve comprising an internal spool that is shifted axially by an external operator  28 , such as a lever. Operator  28  is selectively operable from a stand-by neutral position as shown to a first position P 1  that as will be more fully explained positions the valve spool to cause air under pressure from an on-site source “shop air” or “plant air”) to be supplied through valve  26  to motor inlet port  18 , causing the motor to operate in a sense that will close the shut-off valve if open. Operator  28  is also selectively operable from the stand-by position to a second position P 2  that as will be more fully explained positions the valve spool to cause air under pressure from the on-site source to be supplied directly to motor inlet port  20 , causing the motor to operate in a sense that will open the shut-off valve if closed. 
   Valve  26  is a three-port directional check valve that comprises two inlet ports  30 ,  32 , and an outlet port  34 . Valve  26  allows flow from inlet port  30  to outlet port  34 , but blocks flow in the reverse direction; it allows flow in the direction between port  32  and port  34 . 
   Valve  24  is a directional control valve that comprises an inlet port  36 , two outlet ports  38 ,  40 , and two exhaust ports  42 ,  44 . Operator  28  assumes the stand-by position with valve  24  in the stand-by position shown in FIG.  1 . 
   Inlet port  36  of valve  24  is communicated by a line, or conduit,  46  to the source of air under pressure, i.e. “shop air” or “plant air”. Outlet port  38  is communicated by a line  48  to port  32  of valve  26 . Outlet port  40  is communicated by a line  50  to port inlet port  20  of air motor  12 . Although a line  48  has been shown and described as the means for communicating port  32  and port  38 , certain specific valves may have port geometries that allow port  32  to thread directly to port  38  so that no separate line  48  is needed. 
   Inlet port  32  of valve  26  is communicated by a line  52  to a source of “emergency air”. Outlet port  34  is communicated by a line  54  to motor inlet port  18 . 
   With operator  28  and valve  24  in the stand-by position, no shop or plant air is passed by valve  24  from port  36  to either outlet port  38  or  40 , and consequently, motor  12  can be operated, as will be more fully explained shortly, only if “emergency” air is supplied to port  30  of valve  26 . However, port  40  is open to port  44  and port  38  is open to port  42 . 
   Placement of operator  28  in position P 2  from stand-by position by pivoting operator  28  in one sense from stand-by position operates valve  24  by shifting the valve spool so as to close the path between ports  38  and  42  and open port  38  to port  36  causing valve  24  to pass air from inlet port  36  to outlet port  38 . The air passes through line  48  to port  32  of valve  26 . Valve  26  passes the air from port  32  to port  34 . The air passes through line  54  to motor port  18  causing motor  12  to rotate shaft  16  clockwise. Valve  26  blocks passage of the shop or plant air to port  30 . With operator  28  in position P 2 , port  40  remains open to port  44 , providing an exhaust path for the motor that parallels the path through exhaust port  22 . 
   Placement of operator  28  in position P 1  from stand-by position by pivoting operator in an opposite sense from stand-by position operates valve  24  by shifting the valve spool so as to close the path between ports  40  and  44  and open port  40  to port  36  causing valve  24  to pass air from inlet port  36  to outlet port  40 . The air passes through line  50  to motor port  20  causing motor  12  to rotate shaft  16  counterclockwise. With operator  28  in position P 1 , port  38  remains open to port  42 , and with port  34  being open to port  32  in valve  26 , the two valves  24 ,  26  provide an exhaust path from motor port  18  that parallels the path through exhaust port  22 . With no “emergency air” being applied to port  30 , valve  24  closes the exhaust flow path between ports  34  and  32  to port  30 . 
   If “emergency air” is applied to port  30  while operator  28  and valve  24  are in stand-by position, it will pass through valve  26  to port  34  and through line  54  to port  18  to turn motor shaft  16  clockwise. Valve  26  closes port  32  so that the emergency air is not short circuited away from the motor through valve  24 , and consequently all of the “emergency air” passes to the motor and is exhausted through exhaust port  22 . 
   If “emergency air” is applied to port  30  while operator  28  is in position P 1 , air will pass from either or both ports  30 ,  26  (depending on respective air pressures) to turn motor shaft  16  clockwise. Because an exhaust path exists through valve  24  between ports  40  and  44 , air can exhaust from the motor through it and/or exhaust port  22 . 
   If “emergency air” is applied to port  30  while operator  28  is in position P 2 , emergency air will be applied to motor port  18  at the same time as air is being applied via valve  24  to motor port  20 . Assuming that the pressures at the motor ports  18 ,  20  are substantially equal, the application of emergency air will tend to stall the motor. The application of emergency air will typically be accompanied by an alarm signal of some sort that will be promptly noticed by the personnel presently operating valve  24  to open the shut-off valve. It is expected that the personnel will thereupon release operator  28  so that it and valve  24  will return to neutral stand-by position, resulting in removal of air pressure from motor port  20  so that the emergency air can then be effective to operate motor  12  to close the shut-off valve. 
   If a vessel or tank has more than one valve each requiring the use of its own valve closure system, each such valve closure system may have its own circuit like the one described. 
   While a presently preferred embodiment of the invention has been illustrated and described, it should be appreciated that principles of the invention are applicable to all embodiments that fall within the scope of the claims that follow hereinafter.