Abstract:
A valve and an actuator for vacuum insulated line includes a housing that attaches to the vacuum insulated line. A valve is positioned in the vacuum insulated line, so that the vacuum that insulates the line from ambient temperature also insulates the valve from ambient temperature.

Description:
[0001]    This application claims priority of U.S. provisional application Ser. No. 61/698,123 filed Sep. 7, 2012. 
     
    
       [0002]    This invention was made with Government support under Contract No. SP4701-10-C-0029 awarded by the Defense Logistics Agency (DLA). The Government has certain rights in the invention. 
     
    
     FIELD 
       [0003]    The device relates to an actuator for an in-line vacuum jacketed control valve for cryogenic fluids that is able to be installed on and removed from a line without creating a break in the line. 
       BACKGROUND 
       [0004]    Modern machining processes are increasingly being performed at cryogenic temperatures to achieve improved results. Typically, cryogen is delivered from a supply source to the machining zone through a vacuum insulated line. The vacuum insulated line may comprise an inner line containing the cryogen and an outer line which is exposed to ambient temperatures with a vacuum being maintained between the two lines. In order to be able to turn off the source of cryogen when it is not required, and to meter the flow of cryogen when less than full flow is needed, a valve has to be installed in the line. Any such valve has to be designed to minimize heat gain by the cryogen, and to be immune from frost and operational issues that are associated with frost. The valve should have minimal flow restriction in the open position, provide both on-off and metered flow control, and have minimal power requirements. The valve should also be designed for minimal component wear, and to prevent flow when power is lost. If the valve is installed in a vacuum insulated line, the vacuum in the line should be continuous with a vacuum that is maintained around the valve, and the need for a bellows connection to allow a change of length of the inner line relative to the outer line should be eliminated. The actuator for the valve should have a compact, low-profile design, and be able to be installed on and removed from the line for service and replacement without having to create a break in the line. 
       SUMMARY OF THE DEVICE 
       [0005]    An actuator for a control valve for cryogenic fluids in a vacuum insulated line comprises a housing that is clamped directly onto the line and a split annular magnet. The housing and the magnet may be installed on and removed from the line without disassembling the line. The vacuum in the insulated line surrounds the valve that is controlled by the actuator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of an actuator and a magnet for an in-line control valve. 
           [0007]      FIG. 2  is a sectional view taken along line  2 - 2  of  FIG. 1  showing the valve in a closed position. 
           [0008]      FIG. 3  is a sectional view similar to  FIG. 2  but showing the valve in an open position. 
           [0009]      FIG. 4  is a sectional view taken along line  4 - 4  of  FIG. 3 . 
           [0010]      FIG. 5  is a sectional view taken along line  5 - 5  of  FIG. 2 . 
           [0011]      FIG. 6  is an exploded perspective view of the actuator and magnet of  FIG. 1 . 
           [0012]      FIG. 7  is a view showing the actuator and magnet separated into pieces for removal from a line. 
           [0013]      FIG. 8  shows an alternate form of the actuator that uses a cylindrical piston and piston housing to actuate the in-line control valve. 
           [0014]      FIG. 9  shows an alternate form of the actuator that uses a linear variable position transducer to actuate the in-line control valve. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]      FIG. 1  is a perspective view of an actuator for an in-line control valve generally designated by the reference numeral  10 . The actuator comprises a U-shaped housing  12  having two legs  14  that are spaced by a gap  15 . The gap  15  formed between the two legs is dimensioned and shaped to fit around a vacuum insulated line  16  as shown in  FIGS. 2 and 5 . The ends of the two legs  14  are bridged by a keeper plate  18  that is attached to the two legs by threaded fasteners  19 . Bolting the keeper plate  18  to the ends of the two legs  14  secures the housing  12  on the vacuum insulated line  16 . A cover plate  20  is mounted on the keeper plate  18 , and signal leads  21  extend from a potentiometer  24  (best seen in  FIG. 6 ) that is mounted under the cover plate  20 . A pair of pneumatic couplers  26  are mounted on the housing  12  and lead to opposite ends of a cylinder in the interior of the actuator housing. A two piece shell  27  is used to hold a two-piece annular magnet  28  that is suspended from one end of the actuator housing  12 . Threaded fasteners  30  may be used to hold the two piece shell in place around the annular magnet  28 . The annular magnet  28  surrounds a portion of the vacuum insulated line  16  that contains a control valve  40  (best seen in  FIGS. 2 and 3 ). 
         [0016]      FIG. 2  is a sectional view of the valve and actuator taken along lines  2 - 2  of  FIG. 1  showing the valve in a closed position.  FIG. 3  is a sectional view similar to  FIG. 2  but showing the valve in an open position allowing cryogen to flow through the line  16 . The vacuum insulated line  16  is designed to conduct cryogenic fluid, and the line  16  comprises an inner tube  41  surrounded by an outer tube  42  with a vacuum maintained in the space  50  between the two tubes to provide insulation for the cryogen in the inner tube  41 . A control valve  40  is mounted in a portion of the vacuum insulated line  16  that extends outside of the housing  12 . The valve  40  is positioned in the outer tube  42  and comprises a tubular valve body  45  that is coupled on either end to the inner tube  41  of the cryogen supply line. The coupling of the tubular valve body  45  to the inner tube  41  may be weld joints  47  or other coupling mechanism that provides a leak tight seal between the inner tube  41  and the tubular valve body  45 . A perforated ring  52  may be installed between the inner tube  41  and the outer tube  42  to maintain the inner tube centered in the outer tube and to allow the propagation of the vacuum within the space  50  between the two tubes. 
         [0017]    The tubular valve body  45  contains a movable shuttle valve element  46  that has opposed tapered ends  48  that engage an inlet seat  43  and an outlet seat  44 , respectively, at the two ends of the tubular valve body  45  to control the flow of cryogen in the line  16 .  FIG. 2  shows in full the annular magnet  28  in a retracted position next to the end of the actuator housing  12  and the shuttle valve element  46  in a closed position against the inlet seat  43 .  FIG. 2  shows in phantom the magnet  28  in a fully extended position and the shuttle valve element  46  in a closed position against the outlet seat  44 .  FIG. 3  shows the valve element  46  in an open position between the inlet seat  43  and the outlet seat  44 . 
         [0018]    The shuttle valve element  46  comprises a central body  49  of magnetic material, or material that is attracted to a magnet. The annular magnet  28  is positioned around the portion of the outer tube  42  that surrounds the tubular valve body  45  and movement of the magnet  28  relative to the housing  12  is used to control the position of the shuttle  46  and the flow of cryogen through the inner tube  41 . The vacuum that is maintained in the space  50  between the outer tube  42  and the inner tube  41  flows around and surrounds the valve  40 . By positioning the tubular valve body  45  in the outer tube  42  and by using the vacuum from the outer tube to insulate the tubular valve body  45 , the vacuum surrounding the valve body is reliably maintained with longer service life than if the valve  40  were insulated using a separate evacuated volume. 
         [0019]      FIG. 4  is a sectional view taken along line  4 - 4  of  FIG. 2  showing the shuttle valve element  46 . The shuttle valve element  46  may be formed with axial ridges  51  from one end to the other to assist in centering the movable shuttle valve element  46  in the tubular valve body  45  and to permit cryogen to flow around it when the valve  40  is in the open position. 
         [0020]      FIG. 5  is a sectional view taken along line  5 - 5  of  FIG. 2  showing the cylinder, piston, and magnet assembly. One of the pneumatic couplers  26  communicates with a first passage  31  that leads to the far end of the cylinder  54 . The other pneumatic coupler  26  communicates with a second passage  32  that communicates with the near end of the cylinder  54 . Seals  39  are provided at the lower end of the housing  12  to maintain pressure in the cylinder  54 . Two piston rods  35  are coupled between a U-shaped piston  34 , best seen in  FIG. 4 , and the shell  27  that surrounds the annular magnet  28 .  FIG. 3  shows the piston rods  35  in a fully retracted position in which the shell  27  surrounding the annular magnet  28  is next to the end of the actuator housing  12 . 
         [0021]      FIG. 6  is an exploded perspective view of the actuator housing  12  and magnet  28  of  FIG. 1 . The gap  15  between the legs  14  of the housing is shaped and dimensioned to fit closely around the vacuum insulated line  16 . The annular magnet  28  is formed by two semicircular halves  29  that are mounted in the shell  27 . The interior of the U-shaped housing  12  contains the U-shaped cylinder  54  and the U-shaped piston  34  having the two piston rods  35  that are coupled to the shell  27 . A wiper element  56  is coupled to and moves fore and aft together with the shell  27 . The keeper plate  18  contains a cavity  57  for the potentiometer  24 , and the end of the wiper element  56  that is in contact with the potentiometer  24 . The potentiometer  24  develops signals that are representative of the position of the wiper element  56  on the potentiometer, and the signals are coupled to the signal leads  21  that extend from the potentiometer for connection to outside circuit elements (not shown). 
         [0022]      FIG. 7  shows the manner for removing the actuator housing  12  and the magnet  28  from the line  16  without having to break the line  16 . The keeper plate  18  is unbolted from the legs  14  of the U-shaped housing  12 , freeing the housing to be removed from the line. The threaded fasteners  30  holding the two halves of the shell  27  together are removed allowing the semi-circular magnet halves  29  to be separated and removed from the line  16 . 
         [0023]    In operation, the position of the piston  34  is controlled by pneumatic fluid that enters the interior of the U-shaped housing  12  through the pneumatic couplers  26 . By admitting pneumatic fluid through the passageways  31  and  32  to both sides of the piston  34 , the position of the piston can be positively controlled in the cylinder  54  for precise control of the shuttle valve element  46 . The movement of the piston  34  is directly transferred by the piston rods  35  to the shell  27  that holds the magnet  28 . Movement of the annular magnet  28  causes a corresponding movement of the movable shuttle valve element  46  in the valve  40 . As the magnet  28  moves, the wiper  56  moves, and a signal is developed on the linear potentiometer  24  that is indicative of the position of the annular magnet  28 , and hence the position of the movable shuttle  46 . The signals from the linear potentiometer  24  are used to monitor the position of the annular magnet  28  for feedback control. 
         [0024]    The valve  40  is closed when the shuttle  46  is in either the fully upstream or downstream position and one of the tapered ends  48  of the shuttle is pressed against one of the valve seats  43  or  44 . Full open flow rates occur in the mid-position of the shuttle  46 , half-way between the two valve seats  43  and  44 . A smooth metered flow can best be achieved as the shuttle  46  approaches the inlet seat  43 . Using the position feedback control derived from signals from the potentiometer  24 , it is possible to meter flow though the vacuum insulated line  16  using the in-line valve  40  with negligible heat gain. Flow rates can be precisely controlled by using a programmable actuator to control the position of the magnet  28  and the shuttle valve element  46 . In the event of loss of power, fluid drag through the valve will press the shuttle valve element  46  against the outlet seat  44 , shutting off flow through the valve. 
         [0025]      FIG. 8  shows an alternate form of the actuator that uses a cylindrical piston and cylinder to actuate an in-line control valve. A mounting block  50  may be used to mount a piston assembly  52 , a magnetic housing  53 , and a position sensor  54  to a vacuum insulated line  16  that may contain a cryogenic fluid stream. The piston assembly  52  may comprise an outer housing  55  for a piston cylinder with a cylindrical bore  56  that contains a cylindrical piston  57 . Pneumatic couplers  58  may be provided at either end of the outer housing  55  for coupling to pneumatic lines that are used to position the piston  57  in a desired location within the cylindrical bore  56 . The cylindrical piston  57  is coupled to a piston rod  59  that extends out of the housing  55  and through the mounting block  50  and is attached to the magnetic housing  53 . The magnet housing  53  contains a magnet (not shown) and slides freely over the vacuum insulated line  16 . The magnet in the magnet housing  53  may control a valve similar to the valve  40  shown in  FIGS. 2-4  as described above. A rod  64  is connected to the mounting block  50  and extends through a bushing  65  that is mounted in the magnetic housing  53 . The position sensor  54  contains a potentiometer (not shown) that is coupled by signal leads  67  to external circuitry. A wire or string  68  extends from the potentiometer and is coupled to the magnet housing  53 . A change in position of the magnet housing  53  relative to the mounting block  50  is coupled to the position sensing potentiometer by the string  68 , and the potentiometer develops a representative signal that is coupled by the signal leads  67  to external circuitry. The actuator shown in  FIG. 8  has the advantage of using a cylindrical piston  57  that fits into a cylindrical bore  56  instead of a U-shaped piston and cylinder as described above and shown in  FIGS. 5 and 6 . As in the embodiment of  FIGS. 1-7 , the actuator of  FIG. 8  may be installed and removed from the line  16  without having to break the line, the valve within the line does not require a separate vacuum connection in order to be vacuum insulated, and the actuator for the valve element, the magnet housing  53 , is not a source of heat gain for the cryogen within the line. 
         [0026]      FIG. 9  shows an alternate form of the actuator that uses an actuator with a position sensor to actuate an in-line control valve. A mounting block  70  may be used to mount a housing  71  containing an actuator with a position sensor  72  to a vacuum insulated line  16  that may contain a cryogenic fluid stream. The actuator may be a ballscrew or other linear actuator producing a mechanical displacement in response to an electrical input signal. The position sensor may be a variable differential transformer (LVDT) or other device producing an electrical signal in response to a mechanical displacement. The actuator within the housing  71  is coupled to an output rod  74 . The output rod  74  extends or retracts relative to the outer housing  71  in response to an electrical input signal that is applied to the actuator by the signal leads  76 . The output rod  74  extends out of the housing  71  and through the mounting block  70  and is attached to a magnet actuator housing  78 . The magnet actuator housing  78  contains a magnet and slides freely over the vacuum insulated line  16 . The magnet in the magnet actuator housing  78  may control a valve similar to the valve  40  shown in  FIGS. 2-4  as described above. A guide rod  81  is connected to the mounting block  70  and extends through a bushing  82  that is mounted in the magnet actuator housing  78 . The guide rod  81  and the bushing  82  limit the motion of the magnet actuator housing  78  so that it does not rotate or bind relative to the vacuum insulated line  16 . The motion of the output rod  74  is coupled to the LVDT in the housing  71 . The resulting signal from the LVDT is used as a feedback control on the signal leads  76  to indicate the position of the magnet actuator housing  78  and thus the shuttle valve element (not shown) in the vacuum insulated line  16 . The actuator with an integral position sensor  71  as described herein has the advantage of eliminating the need for pneumatics to actuate a piston in order to change or control the position of the magnet actuator housing  78  and the valve in the vacuum insulated line  16 . As in the embodiments described above, the actuator of  FIG. 9  may be installed and removed from the line  16  without having to break the line  16 , the valve within the line does not require a separate vacuum connection in order to be vacuum insulated, and the actuator itself is not a source of heat gain for the cryogen within the line. 
         [0027]    Having thus described the invention, various modifications and alterations will occur to those skilled in the art, which modifications and alterations will be within the scope of the device as defined by the appended claims.