Fluid pump with pressure relief path

Abstract

A liquid pump includes a pump housing having an inner wall defining an interior. The housing has an inlet port and an outlet port. A liner is disposed within the interior and has opposed lateral openings aligned with the inlet and outlet ports. The liner has a longitudinally extending central bore. A pump piston is axially and rotatably slidable within the liner's longitudinal bore to pump liquid from the inlet port to the outlet port. A seal assembly is fixed to the pump housing adjacent an upper end of the liner. The seal assembly includes a seal body, the upper end of the piston extending through the cap and in sealing engagement with the seal body, and the seal assembly and the liner upper end form a cavity therebetween. The housing has a passageway providing fluid communication between the cavity and the inlet port.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This international application claims priority from U.S. Provisional Patent Application No. 63 / 000,914, filed March 27, 2020, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates generally to liquid pump systems in which one liquid is pumped or dispensed into another liquid stream. More particularly, the present invention relates to a liquid pump with a liquid reservoir and an improved pressure relief slot to minimize leakage. [Background technology]

[0003] There are situations where it is necessary to inject or feed one liquid into another liquid stream. Some liquid pumping systems require occasional injection of liquid, while others require a more continuous supply of liquid. It is contemplated that still other liquid pumping systems may require a combination of the two. For purposes of this disclosure, the term "feeding" is understood to include "injecting."

[0004] One such common application is in the field of water treatment, where certain chemicals, such as chlorinated solutions, fluorinated chemicals, and other liquids, are added to a water stream prior to its delivery for end use by the consumer. To ensure proper functionality, it is important to maintain certain percentage levels of these added liquids without exceeding predetermined concentrations that are considered objectionable or even potentially harmful to the consumer.

[0005] A variety of devices are available in the industry to perform this chemical delivery task. Such devices typically take the form of pumps, with the pump speed and chemical delivery rate controlled by well-known electronic means that use chemical concentration sensing means and provide a voltage or current signal output for use by the pump drive system to regulate its delivery rate. The system operates in a closed loop to maintain a relatively stable concentration of the desired chemical in the water stream.

[0006] Pumps used to inject chlorinated solutions such as sodium hypochlorite (NaOCl) into pressurized water streams often face problems related to the crystallization of NaOCl. While crystallization, due to its tendency to set parts, has been considered in various pump designs, the abrasive nature of these crystals has not been adequately considered.

[0007] Positive displacement pumps with ceramic pistons and liners often suffer from the resulting problems caused by such abrasive crystals. During normal pump operation, the piston will rotate and reciprocate within and out of the pump head. During the piston's outward movement, a properly designed sealing element wipes the piston surface, minimizing the drag of any pumped liquid out of the pump head. However, this squeegee action of the seal is not perfect. Some liquid is always present as a thin film on the exposed piston surface.

[0008] This first difficulty arises most frequently in installations where the NaOCl injection pump is not continuously operated. In such applications, the pump may operate for only an hour and then sit idle for the next 23 hours. During such idle times, if the piston is partially or completely withdrawn from its mating pump head, the aforementioned thin NaOCl film dries, resulting in hard, abrasive crystals forming on the piston surface. At this point, the piston surface resembles a nail file with a fine abrasive.

[0009] When the pump is next started, the piston with the newly formed polished surface will pass the seal element on its way into the pump head. This has been found to prematurely wear the seal element such that it gradually loses its ability to perform a squeegee action on the piston. This leads to increased crystallization during idle time and ultimate failure of the seal.

[0010] Once the seal has completely worn out, further problems arise during idle time. NaOCl infusion pumps of the type being addressed typically utilize a slight negative pressure of approximately 1 psig to 2 psig at the inlet port to prevent NaOCl leakage out of the pump head during idle time. Prior art pumps typically include a pressure relief slot, also known as a "scavenger slot," to provide such negative pressure. However, the combination of a worn seal with a pressure relief slot allows negative pressure to draw air into the pump head. This airflow gradually leads to evaporation of the NaOCl liquid within the pump head, such that crystallization jams the piston, rendering it immobile when later energized.

[0011] Although pump drive mechanisms can be designed to ensure full piston insertion into the pump head during idle times, such mechanisms significantly increase complexity, size, and cost.

[0012] Previous attempts have been made to address the problems of the prior art, such as that shown in U.S. Patent No. 5,629,999, in which a slot is cut on the inner surface of the liner from the inlet port upward to the top of the liner, where an annular liquid reservoir resides. This allows liquid to pass down the slot and prevent the cavity from filling up.

[0013] An internal groove version has also been developed as another solution to the problem. A slot is formed on the inside diameter of the liner, starting at the inlet port but not rising to the top of the liner. Instead, an annular liquid reservoir is created on the inside surface of the liner bore, located between the port and the top of the liner. The slot is fashioned into a groove, achieving the same pressure relief.

[0014] However, these designs require a larger overall clearance between the piston and liner, an open path between the inlet port and the top of the liner, and difficulty in measuring the clearance of the piston / liner set. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] U.S. Patent No. 9,261,085 Summary of the Invention [Problem to be solved by the invention]

[0016] It would therefore be desirable to provide an effective solution to the aforementioned crystallization and leakage problems at minimal cost and without increasing the size or complexity of the pump. More particularly, it would be desirable to provide a simply designed pump that has provisions for reducing leakage at the seal and piston interface and mitigates this using a relatively thin walled liner. [Means for solving the problem]

[0017] The present disclosure provides a liquid pump including a pump housing having an inner wall defining an interior. The housing has an inlet port and an outlet port. A liner is disposed therein and has opposed lateral openings aligned with the inlet and outlet ports. The liner has a longitudinally extending central bore. A pump piston is axially and rotatably slidable within the liner's longitudinal bore to pump liquid from the inlet port to the outlet port. A seal assembly is fixed to the pump housing adjacent an upper end of the liner. The seal assembly includes a seal body, with the piston's upper end extending through the seal assembly and in sealing engagement with the seal body. The seal assembly and the liner upper end form a cavity therebetween. The piston's upper end extends through the seal assembly and in sealing engagement with the seal body, with the seal body and liner upper end forming the cavity therebetween. The housing has a passageway providing fluid communication between the cavity and the inlet port.

[0018] The present disclosure also provides a liquid pump including a pump housing defining a central longitudinal bore. A side bore communicates with the central bore for conveying liquid through the pump housing. A pump piston is axially and rotatably slidably disposed within the central longitudinal bore for pumping liquid through the side bore. The piston and housing define a cavity therebetween, and the housing includes a passageway in fluid communication with the cavity and an inlet port.

[0019] The present disclosure provides a method for reducing leakage in a liquid pump, comprising: generating a negative pressure at an inlet of a pump housing of the pump using a piston axially movable inside a liner disposed within a central bore of the pump housing; creating a positive pressure at the outlet of the pump housing with a piston; transporting fluid from a cavity formed in the pump housing to and from the inlet through a passage formed in the pump housing extending between the inlet and the cavity; Further provided is a method comprising: [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a cross-sectional view of a first embodiment of a fluid pump. FIG. [Figure 1A] FIG. 1 is a perspective view of a fluid pump of the present disclosure. [Figure 2] FIG. 2 is a detailed cross-sectional view taken from FIG. 1. [Figure 3] FIG. 2 is a top plan view of the pump embodiment of FIG. 1. [Figure 4] FIG. 1 is a cross-sectional view of the pump in the base assembly. [Figure 5] FIG. 1 is a cross-sectional view of a pump housing with a liner. [Figure 6] FIG. 1 is a cross-sectional view of a pump housing with the liner removed. [Figure 7] FIG. 10 is a cross-sectional view of a second embodiment of a fluid pump. [Figure 8] FIG. 8 is a detailed cross-sectional view taken from FIG. 7. [Figure 9] FIG. 8 is a top plan view of the pump embodiment of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0021] 1 through 6, a fluid pump 10 generally includes a pump housing 12 and a piston 14 disposed therein. The pump housing 12 has an inlet port 16 and an outlet port 18. The inlet port 16 and the outlet port 18 are connectable to fluid conduits (not shown) operatively connected thereto for supplying fluid to and transporting fluid away from the pump 10. The pump housing defines a cylindrical chamber 20 in fluid communication with the inlet port 16 and the outlet port 18. The chamber 20 has a sidewall 22 extending between a closed bottom end 24 and an open top end 26. The sidewall 22 has a surface 25 exposed to and defining the housing chamber 20.

[0022] A ceramic piston liner 28 having a longitudinally extending central bore 30 and a side bore 32 in communication with the longitudinal bore is received within the cylindrical chamber 20. The side bore 32 includes opposed side openings including an inlet portion 34 in fluid communication with the outlet port 18 of the pump housing so that a liquid, such as a chlorine solution, can be pumped from the inlet port through the liner to the outlet port in a manner described below.

[0023] 4, the pump 10 may be disposed within a base assembly 42 that is covered by a cap 40. The piston 14 is operably secured to a motor (not shown) that actuates the piston 14. The housing 12 may include a threaded portion 44 into which a sleeve 46 is threadably engaged. The sleeve 46 provides a uniform mounting surface when the pump housing 12 is attached to the base assembly 42.

[0024] The piston 14 is axially and rotatably slidable within the longitudinal central bore 30 of the piston liner 28. A clearance space 48 exists between the piston and the liner central bore 30 to allow the piston 14 to move smoothly relative to the reinforcing liner. This clearance 48 can be very small, approximately 0.000100 inches. One end of the piston 14 forms a shaft 50 that extends outward from the open end 26 of the pump housing. The opposite end of the piston is formed with a relief portion 52. As previously mentioned, the relief portion 52 is designed to direct fluid into and out of the pump 10.

[0025] 1 and 2, a seal assembly 54 is provided in the open end 26 of the pump housing 12 to seal the piston 14 and housing chamber 20 and maintain fluid within the pump housing 12. The seal assembly 54 is secured to the open end 26 of the pump housing 12 by a rigid holder 62. The seal assembly 54 includes a seal body 56 and a resilient biasing member 58, which may be in the form of an O-ring. The seal assembly 54 has a central opening 60 for receiving the piston shaft 50. The seal body 56 includes an outer flange 61 held between the holder 62 and a washer 64. The washer 64 has a central opening 65 and is disposed between the seal outer flange 61 and the housing upper end 74 to support the seal body 56. The seal body 56 also includes an annular recess 63 for receiving the biasing member 58. The annular innermost portion of the seal body is a flexible wall 67 having an end that forms a lip seal 69. The biasing member 58 has a diameter greater than the recess 63. Thus, when the biasing member 58 is forced into the recess 63, the biasing member 58 urges the lip seal 69 radially inward so that the lip seal 69 sealingly engages the piston 14.

[0026] Referring to FIG. 4, the base assembly 42 includes an abutment surface 66 that engages the holder 62 when the cap 40 is secured to the base assembly 42, thus securing the seal assembly, piston 14, and pump housing 12 together.

[0027] A cavity 70 is formed between a liner upper end 72 and the seal assembly 54. The liner upper end 72 is disposed below a housing upper end 74, thereby creating space that contributes to the volume of the cavity 70. The washer central opening 65 also creates space that contributes to the volume of the cavity 70.

[0028] In operation, a motor (not shown) drives the piston 14 to move axially and rotate within the liner longitudinal bore 30, drawing liquid from the inlet port 16, into the side bore 32, and out the outlet port 18. The piston 14 is retracted as required to draw a desired amount of liquid into the bore 30 of the pump liner 28, thereby creating negative pressure in the inlet portion 34 of the liner side bore 32 and drawing liquid from the inlet port 16. The piston 14 is then rotated to align the relief portion 52 with the outlet port 18 of the pump housing. The piston is then advanced a desired distance, creating positive pressure and urging liquid through the outlet portion 36 of the side bore 32 and into the outlet port, creating the desired discharge flow.

[0029] During operation, fluid may migrate into gap 48. Eventually, the fluid fills gap 48 and reaches the top of liner 28. The fluid then collects in cavity 70. As cavity 70 fills, any excess fluid seeping out of gap 48 begins to build pressure within cavity 70. If this pressure is not relieved, it is believed that fluid may begin to pass through seal assembly 54 as piston 14 moves into and out of liner 28.

[0030] To relieve fluid pressure and prevent leakage, a pressure relief passage 80 is provided to allow fluid collected within the cavity 70 to be discharged therefrom. The passage provides fluid communication between the cavity 70 and the inlet port 16. The passage 80, extending from the inlet port 16 to the cavity 70, may be disposed on the housing chamber side wall 22.

[0031] As shown in FIGS. 1-6 , in one embodiment, the pressure relief passage 80 may be a channel 82 formed in the housing sidewall surface 25. The channel 82 may be in the form of a groove that is open along its length and exposed to the gap between the liner and the housing sidewall surface 25. The channel 82 has an apex end that terminates at the top end of the housing, the apex end opening into the cavity 70. The channel has a bottom end 86 that opens into the inlet port 16. Thus, upon actuation of the piston, fluid flows from the cavity 70 back into the inlet port 16 and through the pump 10. The channel 82 may be formed, for example, by cutting or molding a groove into the housing inner wall. When the piston 14 is actuated, fluid collected in the cavity 70 flows through the channel 82 and into the inlet port 16 due to the pressure differential between the cavity and the inlet port 16.

[0032] An alternative embodiment is shown in Figures 7 through 9. Elements of the pump 10 are similar to the embodiment shown in Figures 1 through 6, except that the pressure relief passage 80 can be a conduit 88 formed within the housing sidewall 22. The conduit 88 can be formed by drilling a through-hole within the sidewall 22. The conduit 88 is sealed along its length and open at opposing first and second ends 90 and 92. The first end 90 of the conduit is disposed at the top edge of the housing sidewall and communicates with the cavity 70. The washer 64 can include a notch 94 extending from the central opening 65 to provide clearance for the first end 90 of the conduit. The second end 92 of the conduit opens to and engages the inlet port. Thus, the passage 80 is formed between the cavity and the inlet port. By including the passage within the useful housing, the wall thickness of the liner can be made thinner than if the passage were formed within the liner. Fluid collected within cavity 70 flows through conduit 88 into inlet port 16 due to the pressure differential between cavity 70 and inlet port 16 created by moving piston 14 .

[0033] In one exemplary application, the pump 10 of the present disclosure may be used to inject a chlorinated solution, such as sodium hypochlorite (NaOCl), into a pressurized water stream, often encountering problems associated with NaOCl crystallization. However, it is contemplated that the pump 10 may be used in any application in which a fluid is moved in a controlled manner.

[0034] While preferred embodiments of the present disclosure have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those detailed embodiments, and various other changes and modifications may occur to those skilled in the art without departing from the scope or spirit of the invention, and it is intended to claim all such changes and modifications that fall within the scope of the invention. [Explanation of symbols]

[0035] 10 Fluid Pump 12 Pump housing 14 Piston 16 Inlet Port 18 Exit Port 20 Cylindrical chamber, housing chamber 22 (housing chamber) side wall, housing side wall 24 Bottom end 25 (Housing sidewall) surface 26 upper end, open end (of pump housing) 28 Ceramic piston liners, pump liners 30 (liner) longitudinally extending central hole, longitudinal central hole 32 Horizontal hole 34 (Entrance of the horizontal cave) 36 (Exit of the horizontal tunnel) 40 Cap 42 Base Assembly 44 Screw part 46 Sleeve 48 Interstitial space, gap 50 (Piston) shaft 52 Release part 54 Seal Assembly 56 Seal body 58 Elastic biasing member 60 (Seal assembly) central opening 61 (Seal) outer flange 62 Rigid holder 63 Circular depression 64 Washer 65 (Washer) Central opening 66 (Seal assembly) contact surface 67 Flexible Wall 69 Lip seal 70 Cavity 72 (liner) upper end 74 (Housing) Upper End 80 Pressure relief passage 82 channels 86 Lower end (of channel) 88 Conduit 90 (of the conduit) first end 92 (of the conduit) second end 94 (Washer) Notch

Claims

1. a pump housing having a sidewall defining an interior, the pump housing having an inlet port and an outlet port; a liner disposed within the interior and having opposing lateral openings aligned with the inlet and outlet ports, the liner having a longitudinally extending central bore; a pump piston axially and rotatably slidable within the liner longitudinal bore to pump liquid from the inlet port to the outlet port; a seal assembly secured to the pump housing adjacent an upper end of the liner, the seal assembly including a seal body, an upper end of the pump piston extending through the seal assembly and in sealing engagement with the seal body, the seal assembly and the upper end of the liner defining a cavity therebetween; Including, the pump housing having a passageway providing fluid communication between the cavity and the inlet port; The passageway is formed in the side wall of the pump housing.

2. The liquid pump of claim 1 , wherein the passage is a channel formed on a surface of the side wall.

3. 3. The liquid pump of claim 2, wherein said channel is open along its length into said liner.

4. a pump housing having a sidewall defining an interior, the pump housing having an inlet port and an outlet port; a liner disposed within the interior and having opposing lateral openings aligned with the inlet and outlet ports, the liner having a longitudinally extending central bore; a pump piston axially and rotatably slidable within the liner longitudinal bore to pump liquid from the inlet port to the outlet port; a seal assembly secured to the pump housing adjacent an upper end of the liner, the seal assembly including a seal body, an upper end of the pump piston extending through the seal assembly and in sealing engagement with the seal body, the seal assembly and the upper end of the liner defining a cavity therebetween; Including, the pump housing having a passageway providing fluid communication between the cavity and the inlet port; the passageway is a conduit formed in a sidewall of the pump housing, the conduit having a closed sidewall extending along the length of the conduit, a first opening in communication with the cavity, and a second end in communication with the inlet port.

5. 2. The liquid pump of claim 1, wherein said pump housing has a top end, and said passageway extends between said pump housing top end and said inlet port.

6. 6. The liquid pump of claim 5, wherein the liner has a top end, the liner top end being disposed below the pump housing top end and defining a space.

7. The liquid pump of claim 6 , wherein the space contributes to the volume of the cavity.

8. a pump housing defining a central longitudinal bore, with side bores communicating with the central bore for conveying liquid through the pump housing from an inlet port to an outlet port; a liner disposed between the pump piston and the pump housing; a pump piston axially and rotatably slidable within the central longitudinal bore for pumping the liquid through the lateral bore; Including, a cavity defined between the pump piston, the pump housing, and an upper end of the liner, the pump housing including a passage disposed above the upper end of the liner in fluid communication with the cavity and the inlet port.

9. 9. The liquid pump of claim 8, wherein the liner has a top end, the liner top end being disposed below the pump housing top end to define a space.

10. The liquid pump of claim 9 , wherein the space contributes to the volume of the cavity.

11. 9. The liquid pump of claim 8, wherein the passage is formed in a side wall of the pump housing.

12. 10. The liquid pump of claim 9, wherein the pump housing includes a sidewall, and the passageway is a channel formed in a surface of the sidewall of the pump housing.

13. 13. The liquid pump of claim 12, wherein the channel opens along its length into the liner.

14. 9. The liquid pump of claim 8, wherein the passage is a conduit formed in a side wall of the pump housing, the conduit having a closed side wall extending along the length of the conduit, a first opening in communication with the cavity, and an opposing second end in communication with the inlet port.

15. 9. The liquid pump of claim 8, further comprising a seal assembly secured to the pump housing adjacent an upper end of the liner, the seal assembly including a seal body having a recess for receiving a biasing device for urging a portion of the seal body into sealing engagement with the pump piston.

16. 1. A method for reducing leakage in a liquid pump, comprising: creating a negative pressure at an inlet of the pump housing of the pump using a piston axially movable inside a liner disposed within a central bore of the pump housing; generating a positive pressure at an outlet of the pump housing with the piston; transferring fluid to and from the inlet via a passageway formed in the pump housing and extending between the inlet and the cavity, the cavity being formed in the pump housing and disposed above an upper end of the liner; Including, The pump housing central bore has a sidewall, and the passageway includes a channel formed in the sidewall.

17. 1. A method for reducing leakage in a liquid pump, comprising: creating a negative pressure at an inlet of the pump housing of the pump using a piston axially movable inside a liner disposed within a central bore of the pump housing; generating a positive pressure at an outlet of the pump housing with the piston; transferring fluid to and from the inlet via a passageway formed in the pump housing and extending between the inlet and the cavity, the cavity being formed in the pump housing and disposed above an upper end of the liner; Including, The pump housing central bore has a sidewall, and the passage includes a conduit formed within the sidewall.

18. 2. The liquid pump of claim 1, wherein the pump piston extends beyond the seal assembly and the cavity is disposed above the liner upper end.

19. a pump housing having sidewalls forming a housing interior, the pump housing defining a central longitudinal bore with side bores communicating with the central bore for conveying liquid through the pump housing, the pump housing having an inlet port and an outlet port; a liner disposed within the housing and having openings communicating with the inlet port and the outlet port, the liner having an axially extending central bore; a pump piston axially and rotatably slidable within the central bore of the liner to pump the liquid between the inlet port and the outlet port through the side bore; Including, a cavity defined between the pump piston, the pump housing, and an upper end of the liner, the pump housing including a passage in a sidewall of the pump housing, the passage extending along a length of the sidewall and in fluid communication with the cavity and the inlet port disposed above the upper end of the liner.

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