Abstract:
A gas pressure driven fluid pump comprising a pump tank having a liquid inlet and a liquid outlet. A float, carried within the interior of the pump tank, is operable to move between a low level position and a high level position. A snap-acting valve control mechanism uses magnetic interaction to switch between exhaust porting and motive porting. Fluid exiting the pump tank causes the float to fall from the high level position to the low level position due to introduction of motive gas during motive porting. Exhaust porting begins when the float falls to the low level position.

Description:
PRIORITY CLAIM 
   This application claims priority to U.S. Provisional Application Ser. No. 60/436,047, filed Dec. 23, 2002, which is hereby incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates generally to gas pressure driven fluid pumps. More particularly, the invention relates to such a pump utilizing a magnetic valve control mechanism which selectively opens and closes gas ports in a snap acting manner. 
   Condensate removal systems in steam piping arrangements often utilize gas pressure driven pumps that function without electrical power. As described in U.S. Pat. No. 5,938,409 to Radle (incorporated herein by reference), such a pump typically will have a tank with a liquid inlet and a liquid outlet. The liquid inlet and liquid outlet, which are located near the bottom of the tank, will be equipped with an inlet check valve and an outlet check valve to permit liquid flow only in the pumping direction. A pair of interconnected valves control a gas motive port and a gas exhaust port. 
   The pump operates by alternating between a liquid filling phase and a liquid discharge phase. During the liquid filling phase, the motive port is closed while the exhaust port is open. A float connected to a snap acting linkage rises with the level of liquid entering the tank. When the float reaches a high level position, the linkage snaps over to simultaneously open the motive port and close the exhaust port. As a result, the pump will switch to the liquid discharge phase. 
   In the liquid discharge phase, steam or other motive gas is introduced into the pump tank through the motive port. The motive gas forces liquid from the tank, thus causing the float to lower with the level of the liquid. When the float reaches a low level position, the linkage snaps over to simultaneously open the exhaust port and close the motive port. As a result, the pump will again be in the liquid filling phase. 
   While snap acting linkages used in gas pressure driven pumps of the prior art generally have functioned well, there exists room in the art for additional snap acting valve arrangements. 
   SUMMARY OF THE INVENTION 
   The present invention recognizes and addresses the foregoing considerations, and others, of prior art constructions and methods. 
   In one aspect, the invention provides a gas pressure driven fluid pump. The pump comprises a pump tank having a liquid inlet and a liquid outlet. A float is carried within the interior of the pump tank and moves between a low level position and a high level position, depending upon the fluid level within the pump tank. 
   A first magnet portion is operatively connected to the float and moves between a first position and a second position as the float moves between its low level position and its high level position. A second magnet portion is operatively associated with the first magnet portion. 
   The pump also includes a valve assembly connected to the second magnet portion, which is switchable in a snap-over fashion between exhaust porting and motive porting due to magnetic interaction between the first magnet portion and the second magnet portion. 
   When the first magnet portion is located in its first position, the valve assembly is positioned for exhaust porting. The valve assembly snaps over to motive porting when the first magnet portion reaches its second position. As a result, liquid will be alternatively introduced into and discharged from the pump tank. 
   In another aspect, the invention provides a snap-acting valve control mechanism for controlling at least one valve. The mechanism includes a first magnet portion that is movable between a first position and a second position. A second magnet portion is operatively associated with the first magnet portion. 
   The mechanism also includes an actuator connected to the second magnet portion such that movement of the actuator results from magnetic interaction between the first magnet portion and the second magnet portion. When the first magnet portion reaches its first position, the actuator moves the valve to an open position. The actuator moves the valve to a closed position, however, when the first magnet portion reaches its second position. 
   The invention also includes a method of operating a magnetic snap acting valve actuator assembly. The method comprises moving an annular magnet in a direction substantially parallel to its central axis. This movement of the annular magnet increases the magnetic force exerted on an inner magnet located at least partially within the annular magnet. Continued movement of the annular magnet will continue to increase the magnetic force on the inner magnet until the relative displacement of the two magnets results in the magnetic force snapping over to act in the opposite direction and quickly moving the inner magnet. When the inner magnet is moved, a valve is actuated in a snap over manner. 
   The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full and enabling disclosure of the present invention, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the accompanying drawings, in which: 
       FIG. 1A  is a side cross sectional view of a pressure driven pump constructed in accordance with the present invention with the float in the low level position; 
       FIG. 1B  is a side cross sectional view of the pressure driven pump of  FIG. 1A  with the float moving toward, but not yet reaching the high level position; 
       FIG. 1C  is a side cross sectional view of the pressure driven pump of  FIG. 1A  with the float in the high level position; 
       FIG. 1D  is a side cross sectional view of the pressure driven pump of  FIG. 1A  with the float moving toward, but not yet reaching the low level position; 
       FIG. 2A  is a detailed perspective view, partially in section, of a valve control mechanism for a pressure driven pump constructed in accordance with the present invention with the float in the low level position; 
       FIG. 2B  is a view similar to  FIG. 2A  but with the float in the high level position; 
       FIG. 3A  is a detailed side cross-sectional view of the magnetic interaction between the inner magnet and outer magnet in accordance with the present invention with the float in the low level position; 
       FIG. 3B  is a view similar to  FIG. 3A  but showing magnet positions with the float moving toward, but not yet reaching the high level position; 
       FIG. 3C  is a view similar to  FIG. 3A  but showing magnet positions in the high level position; and 
       FIG. 3D  is a view similar to  FIG. 3A  but showing magnet positions with the float moving toward, but not yet reaching the low level position. 
   

   Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. 
     FIGS. 1A–1D  illustrate a pressure driven pump  10  constructed in accordance with the present invention. As shown, pump  10  has a tank  12  defining an interior in which a float  14  is located. Float  14  is attached to the end of a float arm  16 , which is operatively connected to a valve control mechanism  18 . Valve control mechanism  18 , in turn, controls the operation of a valve assembly  19  including a motive valve  20  and an exhaust valve  22 . 
   Valves  20  and  22 , respectively, function to introduce motive gas into and exhaust gas out of the interior of tank  12  based on the position of float  14 . Toward this end, a motive pipe  24  is connected between motive valve  20  and a source of motive gas, such as a source of steam. Similarly, a balance pipe  26  is connected between exhaust valve  22  and a suitable sink to which gas inside of tank  12  can be exhausted. In some cases, for example, balance pipe  26  can terminate such that the gas will simply exhaust to the ambient atmosphere. 
   As shown, tank  12  defines a liquid inlet  28  through which the liquid to be pumped is introduced. Tank  12  further defines a liquid outlet  30  through which the liquid passes when pumped into return line  32 . Respective check valves  34  and  36  are provided at liquid inlet  28  and liquid outlet  30  so that the liquid flows in only the desired direction. 
   When tank  12  is emptied, float  14  will fall to the low level position LP shown in  FIG. 1A . Upon reaching position LP, mechanism  18  simultaneously switches motive valve  20  and exhaust valve  22  in a snap over manner from motive porting to exhaust porting. During exhaust porting, exhaust valve  22  is open to allow fluid communication between the interior of tank  12  and balance pipe  26 ; motive valve  20 , however, is closed to block fluid communication between motive pipe  24  and tank  12 . It should be appreciated by one of ordinary skill in the art that various types of valves could be used for motive valve  20  and exhaust valve  22 . 
   At the beginning of the liquid filling phase, liquid will begin flowing into tank  12  when the pressure is sufficient to overcome the pressure drop across check valve  34 . If the pressure of the liquid is high enough, it will continue through check valve  36  and into return line  32 . When the back pressure in return line  32  exceeds the pressure in the interior of tank  12 , however, the liquid will begin to fill tank  12 . As the level of the liquid rises, so does float  14 . As seen in  FIG. 1B , however, the positions of motive valve  20  and exhaust valve  22  do not change when float  14  is rising. 
   When float  14  reaches position HP, however, as shown in  FIG. 1C , mechanism  18  simultaneously switches motive valve  20  and exhaust valve  22  in a snap over manner from exhaust porting to motive porting. During motive porting, motive valve  20  allows fluid communication between the motive pipe  24  and the interior of tank  12 . Motive gas thus introduced into tank  12  will force the liquid through liquid outlet  30  and into return line  32 . In contrast, exhaust valve  22  is closed during motive porting as shown. Float  14  drops along with the level of the liquid. As shown in  FIG. 1D , however, the positioning of motive valve  20  and exhaust valve  22  remains the same until float  14  reaches position LP. When float  14  eventually falls to position LP, the pumping cycle will begin again. 
   The construction of valve control mechanism  18  will now be described with reference to  FIGS. 2A and 2B . Mechanism  18  contains a fulcrum  38  about which float arm  16  is pivotally connected. One of ordinary skill in the art should recognize that there are numerous devices that could be used to pivotally connect float arm  16  to mechanism  18 . As shown, for example, mechanism  18  could include a pair of depending rails  40  with a pin  42  extending therebetween. Pin  42  extends through float arm  16  so as to pivot at this location. Alternatively, float arm  16  could pivot from a shaft transversely attached to the interior of tank or using another pivotal connection. 
   Float arm  16  is also pivotally connected to a push rod  44 . As shown, the pivot point between float arm  16  and push rod  44  is offset from fulcrum  38  by a predetermined lateral distance. Thus, rotation of float arm  16  causes vertical movement of push rod  44  along its longitudinal axis. The movement of float  14  from position LP toward position HP moves push rod  44  in a first direction along its longitudinal axis (downward as shown in  FIGS. 1A–1B ). As float  14  moves from position HP to position LP, however, push rod  44  moves in an opposite direction along its longitudinal axis (upward as shown in  FIGS. 1C–1D ). 
   Mechanism  18  includes a pair of repelling magnets that facilitate snap-over action: an outer magnet  46  and an inner magnet  48 . In some embodiments, movement of push rod  44  along its longitudinal axis causes movement of outer magnet  46  along a parallel axis. Upon reaching an extreme position, outer magnet  46  causes movement of inner magnet  48  along an approximately parallel axis. It will be appreciated that the use of repelling magnets reduces the number of moving parts and linkages relative to spring-type mechanisms. Moreover, the number of friction points is reduced. Thus the use of repelling magnets reduces the potential for failure. Both inner magnet  48  and outer magnet  46  could be formed from various suitable materials, such as neodymium iron boron or samarium cobalt. Furthermore, it should be appreciated that attractive magnets may also be used. 
   A retaining structure  50  connected to push rod  44  holds outer magnet  46 . As can be seen, support structure  50  has a generally cup-like configuration in this embodiment in which magnet  46  is inserted. As one skilled in the art will appreciate, structure  50  and push rod  44  can be constructed as a unitary member or can be two pieces that are connected together. It should also be appreciated that structure  50  is preferably formed from a nonmagnetic material, such as aluminum. Outer magnet  46  moves linearly with the movement of push rod  44 , which is controlled by the movement of float  14 . Thus, outer magnet  46  reaches its extreme positions when float  14  does the same. 
   Inner magnet  48  is attached to an actuator plate  52  via shaft  51 , such that movement of inner magnet  48  also moves actuator plate  52 . One of ordinary skill in the art should recognize that inner magnet  48  and actuator plate  52  can be constructed as a unitary member or can be two pieces that are connected together. It should also be appreciated that inner magnet  48  could be held within a sheath formed from a nonferrous material, such as copper, aluminum or suitable polymeric materials. The sheath will protect and guide the inner magnet as it may rub against the inner diameter of the outer magnet. 
   As shown, actuator plate  52  is in communication with both motive valve  20  and exhaust valve  22 . Thus, movement of actuator plate  52  controls the porting of motive valve  20  and exhaust valve  22 . As seen in  FIGS. 1A and 1B , motive valve  20  is closed and exhaust valve  22  is open when actuator plate  52  rests on stop  54 . With actuator plate  52  in an elevated position, however, motive valve  20  is open and exhaust valve  22  is closed, as seen in  FIGS. 1C and 1D . Stop  54  limits downward movement of actuator plate  52  while upward movement is limited by exhaust valve  22  in this embodiment. One skilled in the art should recognize that multiple methods could be used for communication between the valves and actuator plate  52 . 
   As outer magnet  46  moves through its range of motion, based upon the position of float  14 , the relative magnetic force imparted upon inner magnet  48  changes. When outer magnet  46  reaches either extreme position (corresponding with either position HP or position LP of float  14 ), the magnetic interaction between outer magnet  46  and inner magnet  48  is sufficient to cause repelling movement of inner magnet  48 . 
   When float  14  reaches position LP, the magnetic interaction between outer magnet  46  and inner magnet  48  imparts a sufficient downward force on inner magnet  48  to move inner magnet  48  in a snap over manner to its exhaust position (actuator plate  52  resting on stop  54 ). Thus, motive valve  20  is closed and exhaust valve  22  is open. When float  14  reaches position HP, the magnetic interaction between outer magnet  46  and inner magnet  48  imparts a sufficient upward force on inner magnet  48  to move inner magnet  48  in a snap over manner to its motive position (actuator plate  52  in an elevated position). Thus, motive valve  20  is open and exhaust valve  22  is closed. 
   Magnets  46  and  48  could be configured numerous ways to produce sufficient magnetic interaction to cause snap over movement. As shown, for example, an annular outer magnet  46  could be used to provide a surrounding magnetic force to move a cylindrical inner magnet  48 . With this configuration, cylindrical inner magnet  48  is received within the inner diameter of annular outer magnet  46 . 
   In some embodiments, magnets  46  and  48  could be configured as planar magnets. For example, magnet  48  could be configured as a single planar magnet with one or more adjacent planar magnets. Moreover, a guide (not shown) could be used to reduce lateral movement of inner magnet  48 . Particularly with a guide, a single planar magnet could be used to impart movement of inner magnet  48 . In addition, one skilled in the art will appreciate that the configuration of structure  50  may change based upon the configuration of outer magnet  46 . In other embodiments, valve control mechanism  18  could be mounted to a vertical cover flange (not shown) using mounts on the side of the pump tank. 
   The interaction between outer magnet  46  and inner magnet  48  during a pumping cycle will now be discussed. When tank  12  is emptied, float  14  will fall to position LP. The movement of float arm  16  causes upward movement of push rod  44  and outer magnet  46 . Upon reaching position LP, the position of outer magnet  46  with respect to inner magnet  48  causes sufficient magnetic interaction to move inner magnet  48  in a snap over position to its exhaust position as shown in  FIGS. 1A and 3A . In the exhaust position, actuator plate  52  rests on stop  54 , thereby placing motive valve  20  in a closed position and exhaust valve  22  in an open position. Exhaust valve  22  thus allows fluid communication between the interior of tank  12  and balance pipe  26  while motive valve  20  prevents fluid communication between motive pipe  24  and tank  12 . 
   As liquid begins flowing into tank  12 , float  14  rises. The movement of float arm  16  causes downward movement of push rod  44  and outer magnet  46  as indicated by arrow H in  FIG. 3B . As seen in  FIGS. 1B and 3B , however, the positioning of inner magnet  48  remains the same until outer magnet  46  reaches a position corresponding with position HP of float  14 . Thus, the position of motive valve  20  and exhaust valve  22  also remains the same. 
   When float  14  reaches position HP, the position of outer magnet  46  with respect to inner magnet  48  causes sufficient magnetic interaction to move inner magnet  48  in a snap over manner to its motive position as shown in  FIGS. 1C and 3C . In the motive position, actuator plate  52  is elevated, thereby placing motive valve  20  in an open position and exhaust valve  22  in a closed position. Motive valve  20  thus allows fluid communication between the interior of tank  12  and motive pipe  24  while exhaust valve  22  prevents fluid communication between balance pipe  26  and tank  12 . When float  14  eventually falls to position LP, the pumping cycle will begin again. 
   One skilled in the art will appreciate that the valve control mechanism of the present invention could be utilized in various applications other than a gas pressure driven pump as described above. In such applications, the mechanism could be operated by various devices and mechanisms other than a float (e.g., by hand, electric, pneumatic, etc.). Moreover, it is often not necessary or desirable to attach physically the stem of valve  20  to plate  52 . In such embodiments, plate  52  can push the stem up when plate  52  rises from stop  54 . The pressure inside of motive pipe  24  will close valve  20  when plate  52  is resting on stop  54 . 
   While preferred embodiments of the invention have been shown and described, modifications and variations may be made thereto by those of ordinary skill in the art without departing from the spirit and scope of the present invention. It should also be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to be limitative of the invention as further described in the appended claims.