Abstract:
A sanitary pump and sanitary valve is provided employing a dual action piston for providing a constant pressure metering and delivery of fluids utilizing a drive shaft positively driven and controlled by a drive motor for sanitary applications. The novel sanitary pump may be fabricated from stainless steel, glass, plastic or other materials which do not include surface imperfections that would allow the growth of bacteria or allow the contamination of foods, medicines and other products that may be precisely metered by the novel sanitary pump. The novel sanitary pump includes novel sanitary check valves for opening and closing a high speed dependably and reliably and cycles up to 200 cycles per minute and preferably in the range of 60 to 160 cycles per minute by providing guides for maintaining check valve stem stability. The novel sanitary pump further include compression seals for sealing the drive piston to maintain high reliability and dependability in high speed constant pressure applications.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     (1) Field of the Invention  
         [0002]     The invention pertains to a constant pressure sanitary pump with sanitary check valves possessing metering capabilities. The novel sanitary pump and check valves are capable of rapid disassembly for cleaning and maintenance. The novel pump utilizes a drive shaft for operation of a double action piston head that is capable of reliable and high speed operation having components and check valves that may be removed from the pump and cleaned and quickly reassembled for sanitary hygienic filling operations as is required in the food handling and pharmaceutical processing arts.  
         [0003]     The simplicity of the novel sanitary pump and sanitary check valves also provide for high speed pumping operations in pressure ranges of 400 p.s.i. pounds per square inch and greater and pumping cycles in the range of about 20 to 200 cycles per minute and preferably in a range of 60 to 160 cycles per minute to provide virtually constant flow. The novel sanitary pump includes interchangeable check valves designed for high speed and reliable operation which can be rapidly removed and interchanged and are compatible with CIP (clean in place) cleaning as is required for sanitary pumps and metering operations in sanitary environments such as is found in the pharmaceutical and food processing industry with CIP (clean in place) cleaning as is required for sanitary pumps and metering operations in sanitary environments such as is found in the pharmaceutical and food processing industry.  
         [0004]     The novel sanitary pump provides a double acting piston coupled to a drive shaft which may be interchanged for left hand or right hand drives or provides for driving from both sides by a drive shaft disposed through the pump housing. Adjustment of the stroke of the double acting piston may be provided in the drive shaft or the drive motor which can be of various types of mechanical drivers such as motors of various types, including electric motors, as well as pneumatic drive motors for the operation of the novel sanitary pump with metering capabilities.  
         [0005]     (2) Description of the Related Art Including Information Disclosed Under 37 C.F.R. 1.97 and 1.98  
         [0006]     The prior art includes a variety of pumps for transporting various types of fluid and semi-fluid products to a filling machine designed for dispensing food and dairy products in sanitary operations. In the prior art, the pump for transporting such fluid material to a separate metering and filling pump is generally referred to as a dosing or feed pump, which provides input feed to a metering and filling machine which in many cases employ a double action piston cylinder combination for alternately transporting the fluid product to a filler head under constant pressure.  
         [0007]     The feed pump or dosing pump is generally of many different configurations and include screw conveyors, single acting piston cylinder pumps, pressurized vessels, and other devices for supplying fluid under pressure to a metering filling machine which then employs a double acting piston for metering and transferring the fluid to fill heads. The known prior art has not combined a feed pump and a double acting constant pressure metering machine into a single constant pressure pump with metering capabilities for application in the food processing industry for filling containers with various food products such as milk, yogurt, cream, cream cheese, and other viscous products so that the fill product is delivered from the metering filling machine by a constant pressure sanitary pump to the fill heads.  
         [0008]     The prior art metering filling machines typically employ a double acting piston cylinder combination and a combination of valves and adjustment mechanisms for metering the amount of fluid to a fill head. Representative prior art of metering filling machines include Lamb, et al. U.S. Pat. No. 1,932,976, Lamb, U.S. Pat. No. 1,470,381, Buford, et al. U.S. Pat. No. 3,447,281, Curtis, et al. U.S. Pat. No. 1,777,293 and Johanssen U.S. Pat. No. 3,370,759. These metering filling devices utilize a double acting piston for providing constant pressure operation for use in the food processing industry, i.e. Lamb, et al. U.S. Pat. No. 1,932,976 and Buford, et al. U.S. Pat. No. 3,447,281.  
         [0009]     The prior art metering filling machines are not pumps, but instead include a pressure differential activated piston cylinder combination having rods disposed axially through the ends of the cylinder wall for determining the position of the piston head and operating the valves for a substantially free floating piston head. Johanssen U.S. Pat. No. 3,370,759 employs a free floating piston head without rods or shafts extending through either end wall of the cylinder and provides a truly free floating piston head which like the other prior art metering filling machines are activated by fluid pressure differential acting upon either side of the piston head.  
         [0010]     Unlike the prior art, the novel sanitary pump utilizes a positively controlled pump drive shaft and does not employ a free floating piston head or a piston with a head for operation in a free floating pressure differential environment. The invention in marked contrast to the prior art, provides a double acting piston head cylinder combination having at least one drive shaft connected to the piston head for positively controlling and driving the piston head in the cylinder. The novel sanitary pump further includes metering capabilities, like the prior art, but in contrast to the prior art, the metering capabilities of the sanitary pump of the invention are achieved by positively controlling the position of the piston head within the cylinder of the novel sanitary pump.  
         [0011]     The prior art metering and filling machines, instead of utilizing a drive shaft, utilize piston rods or shafts that extend through the end walls of the cylinders to adjust the position of the piston head in the cylinder or to activate various valving mechanisms to open or close various types of ball valves, tapered valves, such as in Lamb, U.S. Pat. No. 1,470,381, or pneumatically controlled valves such as in Buford, et al. U.S. Pat. No. 3,447,281 for admitting pressurized fluid into the pressure differential operated piston head. The prior art valves utilized in the prior art metering and filling machine are not check valves and do not provide for high cycle pumping operations. Prior art valves of various designs and configurations while suitable for the metering and filling of machines, the prior art are not suitable for the high pressure, rapid cycled pumps of the invention.  
         [0012]     The prior art also includes various types of manifold and valve arrangements for the double acting metering piston head cylinder combinations. Examples of such manifolds are included in Lamb, et al. U.S. Pat. No. 1,932,976 and Shultz, et al. U.S. Pat. No. 5,992,696. These manifolds and valves do not include check valves and such valves do not provide stem guide means and seat guide means for preventing radial motion of the valve. Furthermore, the valves of the prior art do not include check valves that are opened and closed by the positive pumping action of a positively controlled pump drive shaft connected to the piston head which positively drives and controls the operation of the piston head in response to the drive motor. The prior art check valves are designed to operate by the indirect pressure from a feed pump or dose pump imparted upon a substantially free floating piston head in a metering and filling machine as opposed to the direct pumping action of a pump drive shaft.  
         [0013]     The novel sanitary pump of the invention utilizes reliable high speed sanitary check valves designed to open, close and obviate the problems of wear and tear encountered in a high pressure operation of up to 400 p.s.i. and greater and high speed operation of from about 60 to 160 cycles per minute and up to 200 or more cycles per minute. The novel sanitary pump and sanitary check valves are designed for reliability as well as being easily cleaned by CIP (clean in place) procedures as well as being easily taken apart for periodic cleaning operations. CIP operations in food and pharmaceutical operations presume cleaning without disassembly, although ease of disassembly provides advantages in replacing parts or rapidly removing and replacing components or parts in the event of contamination.  
         [0014]     The prior art does not include a sanitary pump having detachably sealable ends having a positively controlled piston head controlled by a drive motor of an electrical, gasline or pneumatic configuration which positively controls the position of the piston head. The prior art has not provided a double acting sanitary pump having a sanitary check valve capable of high speed dependable operations for high speed cycles from 60 to 160 and up to 200 cycles per minute or more depending on the positively controlled piston head. The prior art has also not provided a novel seal for providing a compression sealing of the piston control shaft in one or both ends of the novel detachable and easily cleanable sanitary pump and sanitary valves by CIP or rapid disassembly into their component parts.  
       BRIEF SUMMARY OF THE INVENTION  
       [0015]     One of the objects of the invention is to provide a sanitary pump having metering capabilities for providing a constant pressure filling operation in a sanitary environment utilizing a double action piston head. The requirements for a sanitary piston pump in a sanitary environment include reducing the number of parts of the sanitary pump to a bare minimum and having all parts capable of clean-in-place operations for periodically cleaning the sanitary pump, as well as the ability to rapidly disassemble the sanitary pump into its component parts. The requirements further include seamless unthreaded components made of stainless steel or other material that can be easily disassembled, sterilized and reassembled back into a working condition.  
         [0016]     Another object of the invention is to provide a constant pressure sanitary pump that is reliable and capable of high speed operations in the range of about 60 to 160 cycles per minute and pressures up to about 400 p.s.i. or greater that includes a piston head driven by a drive shaft that provides a constant pressure operation capable of precise measuring and dispensing of fluid filled materials in a constant pressure filling operation.  
         [0017]     A further object of the invention is to provide a sanitary pump that has a minimum of parts that are interchangeable and can be quickly and easily set up, reconfigured and repaired, that can accommodate a right hand drive motor, a left hand drive motor, or both, and that can be easily transported in component parts and set up in the field and provide reliable constant pressure pump operation. A further object of the invention is to provide a pump and preferably a sanitary pump having a minimum of seals that are readily replaced and easily adjusted in a double acting constant pressure pump. It is an object of the invention to provide a sanitary pump that accommodates a wide range of fluid dispensing operations which within the size and limits of the pump capacity can be modified by adjusting the length of the drive shaft, the linkage connecting the drive shaft to the drive engine or the engine for driving the drive shaft to provide adjustments of the volume of fill materials.  
         [0018]     A further object of the invention is to provide a pump and preferably a sanitary and metering pump that does not depend upon the physical characteristics of the fluid such as compressibility of the fill substance for operation of the piston head, but instead provides a positive control over the piston head through the use of an associated drive motor for driving the piston drive shaft of the novel sanitary pump to dispense the fluid without the introduction of air, turbulence and cavitation that destroy an accurate metering of fill materials. In achieving this object it is also an object to control the stroke of the associated drive motor to within limits to provide further control over the amount of dispensed fluid.  
         [0019]     These and other objects of the invention are achieved by the novel sanitary pump and sanitary valves which can be easily disassembled into their component parts. The novel sanitary pump includes a substantially cylindrical shaped housing body, having a first removably sealable end and a second removeably sealable end with inlet and outlet ports disposed intermediate the removeably sealable ends or disposed in the removeably sealable ends with a piston head disposed intermediate the inlet and outlet ports driven by a drive shaft disposed in substantial axial alignment with the substantially cylindrical pump housing having at least one of the detachably sealeable ends having wiper seals and an adjustable tensioning means for adjustably tensioning the wiper seals around the drive shaft to provide a constant pressure pump having a drive shaft driven by a motor means which preferably includes adjustment means for adjusting the length of travel of the piston head in the novel piston pump.  
         [0020]     The reliability of the novel high speed constant pressure sanitary pump is provided by employing a plurality of interchangeable novel check valves preferably detachably mounted to the inlet and outlet ports of the novel constant pressure pump. The novel sanitary check valves required for high speed and dependable operation include spring biased check valves having a stem guide for limiting the movement of the check valve and a valve seat guide for limiting the radial movement of the check valve. The sanitary check valves are responsive to the pressure provided by the drive motor operating the piston drive shaft to open and close in response to the operation of the drive shaft by opening and closing at high rates of speed to up to 200 cycles per minute or more while providing long term reliability.  
         [0021]     The novel check valve in its preferred configuration is disposed in an upper and lower or clam shell type housing having a valve stem surrounded by a spring constrained in a guide cavity for guiding the stem during the compression of the spring while the seat end of the check valve includes a seal and collar guide having an opening for accommodating flow within the collar while providing a guide at the opposite end for maintaining the check valve in a substantial parallel alignment with the stem constrained in place by a combination of the compression of the spring and spring guide cavity.  
         [0022]     In the best mode of the invention, the sanitary check valve includes a fully detachable upper and lower housing held together by flanges as well as at either end of the upper and lower housings for connection to one of the ports of the novel constant pressure pump. Preferably, each of the flanges can be clamped together with a flange clamp and sealed with an O-ring.  
         [0023]     The novel pump of the invention may be used not only in sanitary operations but all high speed high capacity pumping operations particularly where a constant pressure is desired. The novel high speed constant pressure pump can be configured with a single drive shaft for right and left hand applications since the pump housing is symmetrical and the end plates closing the substantially cylindrical housing can be interchanged. The novel sanitary constant pressure pump can include two drive shafts extending from opposite ends of the piston head to not only provide for right and left drive operations, but also to equalize the volume on both sides of the double acting piston of the novel piston sanitary pump to assist in balancing the volume of fluid metered from the novel sanitary pump.  
         [0024]     The novel double acting piston pump may further include drive stabilize mechanisms to stabilize and maintain a horizontal reciprocal operation of the drive shaft to prevent wearing of the seals and may also include adjustment mechanisms and linkages for adjusting the position of the piston head in the novel sanitary pump. The compact design of the novel constant pressure pump allows for applications of the constant pressure pump in a parallel or tandem operations for increasing pumping throughput and capacity utilizing the novel design and components of the novel sanitary pump.  
         [0025]     These and other advantages of the invention will be further recognized from the accompanying brief description of the drawings as well as the detailed description of the invention. 
     
    
     DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0026]     The objects and advantages of the invention will become more apparent to those skilled in the art from the following detailed description of the invention in relation to the accompanying drawings in which:  
         [0027]      FIG. 1  is a side elevational view partly in section illustrating the novel sanitary pump of the invention;  
         [0028]      FIG. 2  is an enlarged view of the sanitary pump along reference line  2 - 2  illustrating a portion of the drive shaft and novel sealing arrangement of the novel sanitary pump;  
         [0029]      FIG. 3  is an alternative embodiment of the novel sanitary pump of  FIG. 1  including a dual drive shaft and associated detachable sanitary check valves of the novel sanitary pump;  
         [0030]      FIG. 4  is a side cut-away diagrammatic view of the operation of the check valves in relation to the piston head;  
         [0031]      FIG. 5  is a cross-sectional view of a novel check valve in a manifold of the novel sanitary pump;  
         [0032]      FIG. 6  is a pair of check valves disposed in a manifold of the novel sanitary pump;  
         [0033]      FIG. 7  is a cross sectional view of the novel sanitary check valve of the novel sanitary pump in a closed position;  
         [0034]      FIG. 8  is a cross sectional view similar to  FIG. 7  illustrating the novel sanitary check valve in an open position;  
         [0035]      FIG. 9  is a bottom plan view of the valve stem guide of the novel check valve of  FIG. 7 ;  
         [0036]      FIG. 10  is a bottom plan view of the check valve seat of  FIG. 7 ;  
         [0037]      FIG. 11  is an exploded view of the novel sanitary check valve of  FIG. 7  of the novel sanitary pump;  
         [0038]      FIG. 12  is a top plan view of a pair of novel sanitary pumps disposed in a parallel pumping arrangement activated by a single drive motor;  
         [0039]      FIG. 13  is a side elevational view of  FIG. 12 ;  
         [0040]      FIG. 14  is a portion of the novel sanitary pump and drive motor arrangement illustrating a stabilizing means for the drive piston of the novel constant pressure pump; and  
         [0041]      FIG. 15  is a further embodiment of the novel pump illustrating an alternative arrangement of check valves and ports disposed in endplates of the novel pump.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0042]     The advantages inherent in the novel sanitary pump of the invention reside in its simplicity of design, interchangeable parts, novel sealing arrangement for the drive shaft and high speed sanitary and interchangeable check valves which allow the novel sanitary pump to operate at speeds up to and exceeding 200 cycles per minute utilizing a positively controlled drive shaft. It will be recognized the same advantages in simplicity in design, interchangeability of parts and the rapid disassembly of the components provide for clean-in-place (CIP) advantages required for dispensing fluid materials in the food processing and pharmaceutical industry.  
         [0043]     These advantages of the novel sanitary pump are further augmented by the utilization of stainless steel, glass, high density plastic or other material in the fabrication of the novel pump and components that are compatible with high purity material handling requirements in components substantially free from cracks, seams, threads and other components that would capture and provide breeding surfaces for bacteria or other deleterious substances. These same clean-in-place and disassembly advantages allow the novel sanitary pump and sanitary valves to be disassembled and transported easily to remote locations and set up for pumping operations in either sanitary or non-sanitary environments or applications where reliability, high pressure, high flow and particularly a constant pressure pump is desired.  
         [0044]     Referring now to  FIGS. 1-3  a novel sanitary pump in accordance with the best mode of the invention is illustrated. The novel sanitary pump  10  contains a substantially cylindrical housing  12  for accommodating a double acting piston head  14  driven by a drive shaft  16  disposed in substantial axial alignment with the cylindrical housing  12 . The interchangeable, removeable and detachably sealable cylindrical plates  18  and  20  are provided to close the ends of the substantially cylindrical housing.  
         [0045]     Interchangeable, removeable and detachably cylindrical plates  18  and  20  are secured to the substantially cylindrical housing  12  in the preferred embodiment by removeably detachably clamps  22  and  24  which may be flange clamps or tri clover clamps to seal the ends of the substantially cylindrical housing by means of O-rings  26 . The interchangeable, removable and detachably sealable cylindrical plates  18  and  20  are preferably utilized so that plate  18  may be placed on the opposite end of substantially cylindrical housing and plate  20  may be placed at the opposite end of cylindrical housing  12  to allow drive motor  28  to drive shaft  16  of the novel sanitary pump from the left side as opposed to the right side as illustrated in  FIG. 1 .  
         [0046]     Drive motor  28  can be any type of motor to provide reciprocal motion for driving drive shaft  16  reciprocally within housing  12 . In the preferred embodiment, drive motor  28  is a pneumatically activated having air inlets  30  and corresponding air outlets (not shown) for driving piston head  32 . Drive motor  28  may include means for adjusting the reciprocal travel provided for drive shaft  16  such as adjustment screws  34  or adjustment valves for adjusting the length of stroke of drive motor  28 . In addition to adjustment means  34  on drive motor  28  various other types of adjustment means for changing the length of the stroke of drive shaft  16  may be utilized such as linkages, levers and others mechanical means for adjusting the length of the stroke of drive shaft  16  which can be calibrated to adjust the travel of double acting piston head  14  within substantially cylindrical housing  12 . In addition to adjustment means  34  for adjusting the length of the stroke of motor  28 , a further adjustment means  36  is provided at the end of drive shaft  16 . The adjustment means  36  provided on drive shaft  16  may include a threaded opening  38  into which threaded shaft  40  of drive motor  28  may be adjusted by the utilization of adjustment nut  42  ( FIG. 2 ).  
         [0047]     Adjustment means  36  alone or in combination with an adjustment means  34  on drive motor  28  is designed to control the exact position of double acting piston head  14  in cylinder  44  to assist in precisely metering fluids pumped by the novel sanitary pump. In sanitary pump applications, a clamp  46  is designed to connect drive shaft  16  to a threaded shaft  40  of shaft  49  by a nut  48  having a threaded opening  38 . Nut  48  is held in place by clamp  48  with an O-ring seal  50 .  
         [0048]     Referring now again to  FIGS. 1-3  the novel sealing arrangement for sealing drive shaft  16  within interchangeable, removeably and detachably sealable cylindrical plate  18  includes a compression nut  52  for compressing the seals  54  and  56  against drive shaft  16 . Compression nut  52  is adjustably secured to plate  18  by threads  58  to provide for the compression of bushing  60  against seals  54  and  56 , as well as a compression washer  62  disposed between seals  54  and  56 . Seals  54  and  56  are preferably a loaded lip seals or seals that have a lip on it such as cap seals, V-ring seals, quad seals or other types of O-ring seals having a flat surface to provide for a compression and wiping against shaft  16 . The combination of a loaded lip seal together with compression nut  52  provides a tight reliable seal, which may be augmented by a drive shaft stabilizing device, as will be described hereafter in greater detail with respect to  FIGS. 12-14 .  
         [0049]     Referring now to  FIG. 3  an alternative embodiment of the best mode of the invention is illustrated in which drive shaft  16  has been extended in both directions from double acting piston head  14  and interchangeable, removeable, detachably sealable cylindrical plate  18  has been utilized on the seal both ends of cylinder  44 . The advantages of the alternative embodiment as illustrated in  FIG. 3  include the fact that drive rod  16  can be either driven from the left side, as shown in  FIG. 3 , or from the right side by utilizing a drive motor  28 . The alternative embodiment as illustrated in  FIG. 3  further allows the volume on both sides of double acting piston head  14  to be substantially the same or equalized to assist in the precise pumping and metering of dispensed fluids. The positive control over drive shaft  16  by drive motor  28 , and hence piston head  14  is markedly different than the prior art since the novel sanitary pump maintains positive control over the pumped fluid and does not depend upon the physical characteristics over the pumped fluid such as density and compressibility of the dispensed fluid to provide an accurate pumping and metering of the dispensed fluid.  
         [0050]     Referring again to  FIGS. 1-3  the substantially cylindrical housing  12  includes a pair of inlet/outlet ports  64  and  66  disposed on one side of piston head  14  and a second pair of inlet ports  68  and  70  on the other side of piston head  14 . The provision of a pair of inlet and outlet ports, in combination with check valves as will be described hereinafter allows the novel sanitary pump to efficiently pump fluid without entrapping air and to reduce turbulence and cavitation to substantially eliminate frothing and/or other physical disturbances of pumped fluid that would otherwise detract from the metering capabilities of the novel sanitary pump.  
         [0051]     The inlet/outlet ports  64 , 66 ,  68  and  70  in sanitary pumps terminate in flanges  72  for accommodating a similar flange  74  for sealing with an O-ring  76 . The flanges  72  are designed to accommodate a corresponding flange on a detachably separable check valve housing  78 ,  80 ,  82  and  84 . The detachably separable check valve housing ( FIG. 3 ) are held in place by clamps  86  and  88  and sealed by O-ring  76 .  
         [0052]     Referring now to  FIGS. 3-11  the components of the detachably separable check valve housing  78 ,  80 ,  82  and  84  in the novel sanitary pump  10  is illustrated. Each of the detachably separable check valve housing  78 ,  80 ,  82  and  84  are interchangeable and may be rapidly and quickly removed and disassembled or replaced on the novel sanitary pump  10 . The detachably separable check valve housing  78  can be taken apart by removing a flange  88  to disassemble or replace the components of check valve  90 . The check valve is constrained within a separable lower check valve housing  92  that includes upper and lower valves sealed by an O-ring and held together with flange clamp  88 . The check valve  90  includes at the lower end an O-ring seal  94  and at the upper end a spring  96  captured within a cavity  98  disposed within check valve guides  100  ( FIGS. 7 and 8 ) housed by detachably separable check valve housing  78 . O-ring seal  94  on the check valve ( FIG. 11 ) seals and protects the seal area. In the preferred embodiment of the invention check valve guide  100  may be removed from detachably separable check valve housing  78  for cleaning.  
         [0053]     The configuration of the novel check valve is best illustrated in  FIGS. 8-11  which illustrate the arrangement of the check valve in open position ( FIG. 8 ) and closed position ( FIG. 7 ) for the novel sanitary pump. One half of the check valve housing  78  terminates in a flange  101  with a groove for an O-ring  102  for mating with a similar flange and groove on novel sanitary pump housing  10 . As heretofore indicated, a flange clamp  88  is used to connect the two halves of the detachably separable check valve housing  78  to each other utilizing flanges  104  and an O-ring  95  housing  78  to sanitary pump  10 . Separable check valve housing  102  is designed to closely fit around the bottom check valve seat  106  of check valve  90  so that when check valve  90  is in an open position ( FIG. 8 ) the constraining walls of the separable check valve housing  92  are designed as a guide to limit radial movement and maintain check valve  90  in a radially constrained position. The lower guide in limiting radial movement cooperates with spring  96  which as the spring compresses into cavity  98  guides the check valve stem into cavity  98  along with spring  96  and together with constraining walls  108  and check valve seat  106  holds the check valve in axial alignment so as to prevent wobbling or radial movement which otherwise destroys or prevents the check valve from operating in a high speed environment such as is required for check valves operating around or above 200 cycles per minute and generally in a range from 60 to 160 cycles per minute.  
         [0054]     The check valve stem guide support  100  also includes a tight collar  110  for maintaining and guiding the stem of check valve  90  in a substantial axial position. The thickness of collar  110  can also be utilized to assist in maintaining the check valve in substantial axial alignment. The check valve stem guide support  100  also includes vanes  112  which allow products to move through the check valve as illustrated by arrows  114 . The check valve seat  106  also include vanes  118  and openings for allowing fluid to pass around and through the sides of bottom stem  106  as illustrated by arrows  120 .  
         [0055]     The operation of the check valves in the novel sanitary pump is best illustrated in  FIGS. 3-6  and particularly  FIG. 4  in which movement of piston  14  in the direction of arrow  122  causes outlet check valve  128  to open and forces inlet check valves  130  to close. At the same time, the action of double acting piston  14  results in outlet check valve  126  to close and forces inlet check valve  124  to open. Once the stroke of piston head  14  is complete, piston head  14  moves in the direction of arrow  132  causing outlet check valve  128  to open and inlet check valve  130  to close while at the same time forcing inlet check valve  124  to close and outlet check valve  126  to open. The motion of piston head  14  is positively controlled by drive shaft  16  to positively maintain control over fluids entering and exiting the novel sanitary pump without the necessity of relying upon compressibility of the fluid to drive piston head  14 .  
         [0056]     The fact that piston head  14  is positively controlled is of significant advantage in not having lead and lag time in operation as it does not rely upon compressibility of the fluid for operation, a much greater control is maintained over the fluids pumped by piston head  14 . In addition, the positive control over piston head  14  by drive shaft  16  in combination with the check valves eliminates frothing and undue turbulence imparted to the dispensed fluids imparted by feed or dosing pumps to more precisely control and meter dispensed fluids where precise metering is desired. In filling operations in most applications a separate feed of dosing pump is not required. As will be recognized the operation of the double acting sanitary pump provides a constant pressure pump for dispensing fluids in filling and transferring fluid operations.  
         [0057]     As heretofore discussed, the novel sanitary pump may be configured in a variety of configurations with right drive and left drive operations as well as the provision for tandem and parallel applications of the novel sanitary pump. These configurations and applications of the sanitary pump  10  by way of illustration included in  FIGS. 12-14  in which a single drive motor  28  is provided to drive two sanitary pumps,  140  and  142  in a parallel application for increased capacity. Drive motor  28  drives a gear box  144 , which is a prior art gear box, such as is available from Leeson Electric Motor of Grafton, Wis. for driving the two novel sanitary pumps  140  and  142 . Gear box  144  includes a pair of crank mechanisms  146  and  148  for driving adjustable linkages  150  and  152  adjustably connected to two drive shafts  216  and  316  of novel sanitary pumps  140  and  142 . In such operations the provision of stabilizing means  152  is provided to stabilize drive shafts  216  and  316  to prevent undue lateral movement and wear on seals  54  and  56  in interchangeably removeable and detachably sealable cylindrical plates  18 . Stabilizing means  152  may include confronting wheels  154  and  156  for maintaining drive shaft  216  in a substantial fixed radial position while drive piston  216  reciprocates axially within cylinder  44  of cylindrical housing  12  of sanitary pump  142 .  
         [0058]     As will be recognized by those skilled in the art the novel sanitary pump may be modified in a number of ways to suit particular applications. One or both inlet and outlet ports disposed in the interchangeable and removeably sealable end plates  18  and  20  as illustrated in  FIG. 15 . In  FIG. 15  end plates  18  and  20  have been modified to include an outlet port  200  and an inlet port  202  with sanitary inlet check valve  124  and sanitary outlet check valve  126  and sanitary inlet check valve  130 . The novel sanitary pump substantially cylindrical housing  12  may be closed by removeably sealable end plates  18  and  20  utilizing a plurality of bolts  204  with a plurality of nuts  206 . As will be further recognized drive shaft  16  may extend from both sides of piston head  14  and end plate  18  may be used on both ends of cylindrical housing  12  in a configuration similar to the novel sanitary pump as described with reference to  FIG. 3 .  
         [0059]     The novel sanitary pump of the invention may be configured and implemented in a number of ways to achieve the advantages of a constant pressure reliable pump having high capacity, high reliability and easily detachable and easily assembable components for a variety of configurations and operations. It will be recognized that the novel sanitary pump can be utilized in non-sanitary application where the end plates may be threaded into the housing or sealed in various prior art ways in non-sanitary applications. It will be further recognized that the sanitary valves of the novel sanitary pump may be modified and implemented in a number of different ways to achieve the advantages of the invention.  
         [0060]     It will be recognized by those skilled in the art the various modifications and substitutions may be made to suit particular requirements and applications, including right hand drive, left hand drives or the utilization of a drive shaft extending from both ends of the piston head and through the end plate of the constant pressure pump. It will be further appreciated that the size of the pump may be changed to various sizes and shapes to fit particular application and implementation of the invention. It will be understood the inlet and outlet ports of the novel pump may be reconfigured in a number of ways on the pump housing or on the endplates. It will also be recognized the check valves may be incorporated into or on the novel pump in a variety of ways and the inlet and outlet check valves may be designed to prevent improper orientation in the novel sanitary pump. It is to be understood that these and other changes may be made by those skilled and with are within the scope of the appended claims.  
         [0061]     As used herein and in the following claims the word “comprising,” or “comprises” is used in its technical sense to mean the enumerated elements include but do not exclude additional elements which may or may not be specifically included in the appended claims. It will be understood that such additions whether or not made in the dependent claims are modifications that can be made within the scope of the invention. It will be further appreciated by those skilled in the art the wide range of changes and modifications can be made to the invention without parting from the spirit and scope of the invention as defined in the following claims.