Patent Publication Number: US-10316839-B2

Title: Pump plunger for a linearly actuated pump

Description:
TECHNICAL FIELD 
     This disclosure generally relates to a linearly actuated pump and, more particularly, to a pump plunger for a linearly actuated pump. 
     BACKGROUND 
     Generally speaking, a linearly actuated pump includes a drive assembly operatively engaged with a pumping assembly. The pumping assembly generally includes a barrel having a bore extending therethrough, a head having a chamber for pressurization of a fluid, and a pump plunger positioned within the bore. The drive assembly provides reciprocating linear motion to the pump plunger, thereby causing it to reciprocate within the bore. 
     While the pump plunger is moving in a pressurization stroke or pumping direction, at least some of the energy added to the fluid is transferred to the barrel and the pump plunger, the pressure of the fluid increases, the walls of the barrel may elastically deform and expand outwardly due to the pressure increase, and the temperature of the fluid increases. Likewise, the pump plunger may also elastically deform resulting in an increased diameter. 
     However, since the barrel has greater mass than the pump plunger, and because it is immersed in the fluid, the barrel does not deform an equal amount as the pump plunger. Thus, as the pressure decreases on a return and filling stroke, the walls of the barrel may substantially return to their original configuration, while the pump plunger remains in an expanded state. Therefore, the pump plunger may rub or scuff the barrel on the return stoke, thereby reducing service life of the linearly actuated pump. 
     US Patent Application Publication US 2016/0222959 to Campion et al. (“Campion”) discloses a cryogenic piston pump with a barrel, a head with a bore, and a pump plunger slidably disposed within the bore. The pump plunger may be coated with tribological coating main layer, and a sacrificial break-in layer placed on the main layer that may also include a tribological coating, to thereby reduce rubbing, scuffing, and seizure of pump plungers and barrels. 
     The present disclosure is directed to overcoming one or more problems set forth above and/or other problems associated with the prior art. 
     SUMMARY 
     In accordance with one aspect of the present disclosure, a pump plunger is disclosed. The pump plunger may include a proximal end and a distal end opposite the proximal end. The pump plunger may also include a body portion extending between the proximal end and a second transition datum, and additionally include a transition section extending between a first transition datum and the second transition datum. The transition section may have a non-linear geometric profile. A first shoulder portion may be positioned adjacent to the transition section that may extend between the second transition datum and a third datum. The third datum may be positioned radially inward of the second transition datum. The pump plunger may also include a tip portion positioned adjacent to the first shoulder portion that may extend between the third datum and a fourth datum positioned at the distal end. The fourth datum may be positioned radially inward of the third datum. 
     In accordance with another aspect of the present disclosure, a pumping assembly is disclosed. The pumping assembly may include a head, a barrel, and a pump plunger. The head may include a chamber for pressurizing a fluid, and the barrel may have a bore extending therethrough. The pump plunger may include a proximal end and a distal end opposite the proximal end. The pump plunger may also include a body portion extending between the proximal end and a second transition datum, and additionally include a transition section extending between a first transition datum and the second transition datum. The transition section may have a non-linear geometric profile. A first shoulder portion may be positioned adjacent to the transition section that may extend between the second transition datum and a third datum. The third datum may be positioned radially inward of the second transition datum. The pump plunger may also include a tip portion positioned adjacent to the first shoulder portion that may extend between the third datum and a fourth datum positioned at the distal end. The fourth datum may be positioned radially inward of the third datum. 
     In accordance with another embodiment of the present disclosure, a linearly actuated pump is disclosed. The linearly actuated pump may include a drive assembly and a pumping assembly. The pumping assembly may include a head, a barrel, and a pump plunger. The head may include a chamber for pressurizing a fluid, and the barrel may have a bore extending therethrough. The pump plunger may include a proximal end and a distal end opposite the proximal end. The pump plunger may also include a body portion extending between the proximal end and a second transition datum, and additionally include a transition section extending between a first transition datum and the second transition datum. The transition section may have a non-linear geometric profile. A first shoulder portion may be positioned adjacent to the transition section that may extend between the second transition datum and a third datum. The third datum may be positioned radially inward of the second transition datum. The pump plunger may also include a tip portion positioned adjacent to the first shoulder portion that may extend between the third datum and a fourth datum positioned at the distal end. The fourth datum may be positioned radially inward of the third datum. 
     These and other aspects and features of the present disclosure will be more readily understood when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION 
         FIG. 1  is a cross-sectional view of a linearly actuated pump in accordance with the present disclosure. 
         FIG. 2  is a cross-sectional view of a barrel assembly that may be used in conjunction with the linearly actuated pump of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the barrel assembly of  FIG. 2  during a pressurization stroke. 
         FIG. 4  is a perspective view of a pump plunger that may be used in conjunction with the barrel assembly of  FIG. 2 . 
         FIG. 5  is a partial profile of the pump plunger of  FIG. 3 . 
         FIG. 6  is a graphical representation illustrating a non-linear geometric profile of a transition section of the pump plunger of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Referring now to the drawings, and with specific reference to  FIG. 1 , a linearly actuated pump is depicted and generally referred to by reference number  10 . As is depicted therein, the linearly actuated pump  10  may be subdivided into a drive assembly  12  and a pumping assembly  14 . The pumping assembly  14  may be configured for submersion in a tank or within a reservoir  16  as is depicted. 
     The drive assembly  12  may include a stub shaft  18  operatively connected to a drive shaft  20 , both of which are rotatable about a longitudinal axis  22 . The drive shaft  20  may be operatively coupled with a loadplate  24  via a wobble plate  26 . Each of the loadplate  24  and the wobble plate  26  may be rotatable about the longitudinal axis  22 . The loadplate  24  may be operatively engaged with an upper push rod  28  via a tappet  30 . In turn, a lower push rod  32  may be operatively engaged with the loadplate  24  via the upper push rod  28  and the tappet  30 . As the loadplate  24  rotates, the tappet  30 , the upper push rod  28  and the lower push rod  32  may reciprocate along an axis of reciprocating motion  34  that is parallel to the longitudinal axis  22 . Alternatively, the linearly actuated pump  10  may be hydraulically driven. For example, the drive assembly  12  may include a cylinder and piston (not shown) configured to operatively engage the lower push rod  32  and set the pumping assembly  14  in motion. 
     The pumping assembly  14  may include a manifold  36  operatively connected to the drive assembly  12 , and a barrel assembly  38  configured to pressurize a fluid, and more particularly, a cryogenic fluid. The barrel assembly  38  may be submerged in a tank including the fluid, or in the reservoir  16 , as is shown. The barrel assembly  38  is depicted in greater detail in  FIG. 2 . 
     The barrel assembly  38  may extend between a proximal side  40  and a distal side  42  opposite the proximal side  40 , and the proximal side  40  may be operatively connected to the manifold  36 . The barrel assembly  38  defining a barrel axis  44  extending therethrough that maybe collinear with the axis of reciprocating motion  34  and offset from the longitudinal axis  22 . Alternatively, however, in the case of the linearly actuated pump  10  having only one barrel assembly  38 , the barrel axis  44 , the axis of reciprocating motion  34 , and the longitudinal axis  22 , may all be collinear. The terms “proximal” and “distal” are used herein to refer to the relative positions of the components of the barrel assembly  38 . When used herein, “proximal” refers to a position relatively closer to the end of the barrel assembly  38  operatively connected to the manifold  36 . In contrast, “distal” refers to a position relatively further away from the end of the barrel assembly  38  operatively connected to the manifold  36 . 
     The barrel assembly  38  may include a barrel  46  positioned at the proximal side  40  and a head  48  positioned at the distal side  42 . The head  48  may be operatively attached to the barrel  46  to close off the barrel assembly  38 . Alternatively, the barrel assembly  38 , including the barrel  46  and the head  48 , may be integrally formed as a unitary piece. 
     A bore  50  may extend through the barrel  46  and be configured to receive a pump plunger  52  that is operatively engaged with the lower push rod  32 . A distal side of the bore  50  may form a chamber  54 , which may extend into the head  48 . The head  48  may further include an inlet passage  56  extending from the distal side  42  and ending at the chamber  54 , and an inlet check valve  58  may be located at the junction between the chamber  54  and the inlet passage  56 . The inlet check valve  58  may be spring-biased to a closed position that impedes passage of the fluid into the chamber  54  unless the chamber  54  is under a relative negative pressure. In another configuration, the inlet check valve  58  may lack a spring and instead be biased to the closed position due to gravity, and open due to the relative negative pressure. 
     The head  48  may additionally include an outlet passage  60  extending between the chamber  54  and the proximal side  40  of the barrel assembly  38 . An outlet check valve  62  may be positioned in the outlet passage  60 . Alternatively, the outlet check valve  62  may be positioned adjacent to the chamber  54 . The outlet check valve  62  may be spring-biased to a closed position that impedes passage of the fluid out of the chamber  54  unless the chamber  54  is under a relative positive pressure. 
     The pump plunger  52  may slidingly reciprocate within the bore  50  between a top position  64  closer to the proximal side  40  and a bottom position  66  closer to the distal side  42 . When in the bottom position  66 , at least some portion of the pump plunger  52  may be disposed in the chamber  54 . On the other hand, when in the top position  64 , little or no portion of the pump plunger  52  may be disposed in the chamber  54 . When the pump plunger  52  is moving from the top position  64  toward the bottom position  66 , the fluid in the chamber  54  is under increasing pressure until reaching maximum pressure at the bottom position  66 . Moving from the top position  64  to the bottom position  66  is a pressurization stroke. In contrast, when the pump plunger  52  is moving from the bottom position  66  toward the top position  64 , the fluid in the chamber  54  is under decreasing pressure until reaching is minimum value at the top position  64 . During this motion, the inlet check valve  58  may be open and therefore admitting liquid into the chamber  54 . Moving from the bottom position  66  to the top position  64  is a return and filling stroke. 
     When the pump plunger  52  is moving from the top position  64  toward the bottom position  66  during the pressurization stroke, energy is added to the fluid in the bore  50  and chamber  54 , and at least part of the energy added to the fluid is transferred to the barrel  46  and the pump plunger  52  as thermal energy. In response, and as is depicted by the dashed lines in  FIG. 3 , the barrel  46  may elastically deform and expand radially outward from its original configuration relative to the barrel axis  44 . Similarly, as is also illustrated by the dashed lines in  FIG. 3 , the pump plunger  52  may elastically deform and expand radially outward relative to the barrel axis  44  due to the energy transfer from the fluid. 
     However, since the barrel  46  has greater mass than the pump plunger  52 , and because it is immersed in the fluid in the tank or reservoir  16 , the barrel  46  does not deform an equivalent amount as pump plunger  52 . Thus, as the pump plunger  52  is moving from the bottom position  66  toward the top position  64  during the return and filling stroke, the barrel  46  may return to its original configuration relative to the barrel axis  44 , while the pump plunger  52  remains in the radially outwardly expanded state. Therefore, the pump plunger  52  may rub, scuff, or possibly seize with, the barrel  46  during the return and filling stroke. 
     The present disclosure is directed toward a pump plunger  52  constructed in accordance with  FIGS. 4-6 . As illustrated in  FIG. 4 , the pump plunger  52  may extend between a proximal end  68  and a distal end  70  opposite the proximal end  68 . A plunger axis  72  may extend through the proximal end  68  and the distal end  70 . Turning to  FIGS. 4-5 , a body portion  74  may extend between the proximal end  68  and a second transition datum  76 . The body portion  74  may include a transition section  78  extending between a first transition datum  80  and the second transition datum  76 . 
     Referring now to  FIG. 6 , the transition section  78  may have a non-linear geometric profile  82 , and the second transition datum  76  may be positioned radially inward of the first transition datum  80  relative to the plunger axis  72 . In other words, the radius of the pump plunger  52  at the second transition datum  76  may be less than the radius at the first transition datum  80 . In one example, the non-linear geometric profile  82  extending between the first transition datum  80  and the second transition datum  76  may conform to the following equation, where y is the radius of the pump plunger  52  and x is the axial location along the pump plunger  52 : 
             y   =       -       3   ⁢     x   3       128000       +       9   ⁢     x   2       32000     -     0.006   .             
However, as is understood by a person of ordinary skill in the art, the non-linear equation describing the non-linear geometric profile  82  may differ due to varying operating conditions. For example, the operating pressure of the pump  10 , the chemical composition of the fluid being pumped, the material utilized to manufacture the pump plunger  52 , the material utilized to manufacture the barrel  46 , and the material utilized to produce the head  48 , may each alone, or in combination, affect the non-linear equation describing the non-linear geometric profile  82 .
 
     Referring again to  FIGS. 4-5 , the pump plunger  52  may further include a first shoulder portion  84  positioned adjacent to the transition section  78 , that may extend between the second transition datum  76  and a third datum  86  that is positioned radially inward of the second transition datum  76  relative to the plunger axis  72 . Accordingly, the radius of the pump plunger  52  at the third datum  86  may be less than the radius at the second transition datum  76 . Furthermore, the first shoulder portion  84  may have a linear profile, and extend between the third datum  86  and the second transition datum  76  at an angle α relative to the plunger axis  72 . The angle α may range between 15° and 60°. 
     The pump plunger  52  may further include a tip portion  88  positioned adjacent to the first shoulder portion  84  that may extend between the third datum  86  and a fourth datum  90  positioned at the distal end  70 . The fourth datum  90  may be positioned radially inward of the third datum  86  relative to the plunger axis  72 . Therefore, the radius of the pump plunger  52  at the fourth datum  90  may be less than the radius at the third datum  86 . Moreover, the tip portion  88  may include a second shoulder portion  92  positioned adjacent to the distal end  70 , that may extend between a fifth datum  94  and the fourth datum  90 . The fourth datum  90  may be positioned radially inward of the fifth datum  94  relative to the plunger axis  72 . Therefore, the radius of the pump plunger  52  at the fifth datum  94  may be less than at the third datum  86 , and may be greater than the radius at the fourth datum  90 . Additionally, the second shoulder portion  92  may have a linear profile, and extend between the fourth datum  90  and the fifth datum  94  at an angle θ relative to the plunger axis  72 . The angle θ may range between 15° and 60°. 
     Referring to  FIGS. 4-6 , the slope of the non-linear geometric profile  82  at the first transition datum  80  is approximately zero. In addition, the slope of the non-linear geometric profile  82  at the second transition datum  76  may be approximately zero. may be approximately zero. Accordingly, the slope of the non-linear geometric profile  82  at the first transition datum  80  is parallel to the slope of the non-linear geometric profile  82  at the second transition datum  76 , and both of these slopes may be parallel to the bore  50 . 
     INDUSTRIAL APPLICABILITY 
     The disclosed plunger and pump finds potential application in any fluid system where heat transfer from a pressurized fluid to the plunger is undesirable. The disclosed plunger and pump finds particular applicability in cryogenic fluid applications, for example, power system applications having engines that combust liquid natural gas as fuel. One skilled in the art will recognize, however, that the disclosed plunger and pump may be utilized in other applications that may or may not be associated with cryogenic fluid applications, and even other applications besides power systems. Operation of the linearly actuated pump  10  will now be described in more detail. 
     The stub shaft  18  may be rotated about the longitudinal axis  22  by a power source such as, but not limited to, Otto and Diesel cycle internal combustion engines, electric motors, gas turbine engines, and the like. In turn, the drive shaft  20  may rotate the loadplate  24  via the wobble plate  26 , thereby converting rotational motion into reciprocating linear motion. The lower push rod  32  may linearly reciprocate along the axis of reciprocating motion  34  via its operative engagement with the loadplate  24  via the upper push rod  28  and the tappet  30 . 
     As the pump plunger  52  is operatively engaged with the lower push rod  32 , the pump plunger  52  may slidingly reciprocate along the barrel axis  44  of the barrel assembly  38  between a top position  64  and a bottom position  66  inside the bore  50 . When moving the pump plunger  52  from the top position  64  toward the bottom position  66 , fluid in the chamber  54  may be under increasing pressurization until reaching maximum pressure at the bottom position  66  during the pressurization stroke. When at the bottom position  66 , the relative pressure in the chamber  54  may be at a great enough value to overcome the spring-bias of the outlet check valve  62 , and as such, the fluid may exit the chamber  54  through the outlet passage  60 , and past the outlet check valve  62 , towards the proximal side  40 . 
     In turn, when moving the pump plunger  52  from the bottom position  66  toward the top position  64 , decreasing relative pressure inside the chamber  54  may eventually be at a low enough value such that the spring-bias of the outlet check valve  62  overcomes the relative pressure inside the chamber  54 , and in turn returns to its closed position, thereby stopping outflow of any fluid in the chamber  54  past the outlet check valve  62  through the outlet passage  60  toward the proximal side  40 . Further, the relative pressure inside the chamber  54  may eventually become low enough to overcome the spring-bias of the inlet check valve  58 . At this point, fluid in the tank or reservoir  16  may enter the barrel assembly  38  through the inlet passage  56 , past the inlet check valve  58 , and into the chamber  54  until the lowest relative pressure when the pump plunger  52  is at the top position  64 . Then, when moving the pump plunger  52  back toward the bottom position  66 , the relative pressure inside the chamber  54  may be great enough to overcome the spring-bias of the inlet check valve  58 , thereby stopping the inflow of fluid through the inlet passage  56 , past the inlet check valve  58 , into the chamber  54 . 
     As described before, the pump plunger  52  may elastically deform and expand radially outward while moving from the top position  64  toward the bottom position  66 . Further, the pump plunger  52  may remain in this expanded state when moving from the bottom position  66  toward the top position  64  and may rub, scuff, or possibly seize with, the barrel  46  during this return and filling stroke. However, a pump plunger  52  having the attributes of  FIGS. 4-6 , including the transition section  78 , mitigates this issue and increases service life of the linearly actuated pump  10 . 
     The above description is meant to be representative only, and thus modifications may be made to the embodiments described herein without departing from the scope of the disclosure. Thus, these modifications fall within the scope of present disclosure and are intended to fall within the appended claims.