US20140064996A1

US20140064996A1 - Plunger pump

Info

Publication number: US20140064996A1
Application number: US13/949,351
Authority: US
Inventors: Yoshinori Arima
Original assignee: Shimadzu Corp
Current assignee: Shimadzu Corp
Priority date: 2012-08-30
Filing date: 2013-07-24
Publication date: 2014-03-06
Also published as: CN103671076A; JP2014047664A

Abstract

A plunger pump includes a pump body, a pump head attached to a tip end portion of the pump body, the pump head including a pump chamber, an inlet path and an outlet path, a plunger that slides in an axial direction along the inner wall of the pump chamber, and a ring-shaped plunger seal for preventing fluid leakage from the pump chamber to the pump body. The plunger seal is arranged between the pump chamber and the pump body with a front surface facing the pump chamber and a back surface facing the pump body, includes a penetration hole from the front surface to the back surface, and holds the plunger in a slidable manner with the inner wall of the penetration hole. The plunger seal includes a ring-shaped hollow portion surrounding the penetration hole, the hollow portion communicating with a back surface side of the plunger seal and not communicating with a front surface side of the plunger seal. An elastic member for expanding the hollow portion in a radial direction of the plunger by an elastic force is provided inside the hollow portion.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a plunger pump which is a type of delivery pump used for delivering a mobile phase of a liquid chromatograph, for example, and which performs delivery by sliding a plunger inside a pump chamber provided in a pump head.
2. Description of the Related Art
A general plunger pump (see Japanese Patent Laid-open Publication No. 2001-254686) will be described using FIG. 3.
A pump head 38 is attached at a tip end of a pump body 30 across a cleaning chamber 44 for cleaning a plunger 33. A crosshead 34 that reciprocates in one direction by a cam mechanism (not shown) and a spring 36 is accommodated within the pump body 30, and a plunger 33 is attached at the tip end of the crosshead 34. A tip end portion of the plunger 33 is inserted into a pump chamber 38 a provided inside the pump head 38, and slides inside the pump chamber 38 a along the inner wall of the pump chamber 38 a.
An inlet path 38 b and an outlet path 38 c communicating with the pump chamber 38 a are provided to the pump head 38. Check valves 39 a and 39 b that open or close according to the pressure inside the pump chamber 38 a are provided to the inlet path 38 b and the outlet path 38 c. When the plunger 33 is moved to the suction side (the right side in the drawing), the check valve 39 a opens and fluid is drawn into the pump chamber 38 a from the inlet path 38 b, and when the plunger 33 moves to the discharge side (the left side in the drawing), the check valve 39 b opens and the fluid inside the pump chamber 39 a is discharged from the outlet path 38 c.
A concave portion 40 communicating with the pump chamber 38 a is provided on a surface of the pump head 38, on the side of the pump body 30. A plunger seal 42 which the plunger 33 penetrates and which holds the plunger 33 in a slidable manner is embedded in the concave portion 40, and a backup ring 43 is inserted on the back surface side of the plunger seal 42 (on the side of the surface on the pump body 30 side). The plunger seal 42 is for preventing the fluid from the pump chamber 38 a from leaking to the side of the pump body 30. A cleaning seal 46 for preventing leakage of cleaning fluid is attached to the cleaning chamber 44.
The plunger seal 42 has a ring-shaped concave portion 42 a provided on the front surface facing the pump chamber 38 a, and is structured to expand the concave portion 42 a when the delivery pressure is high by storing the fluid which has leaked from the pump chamber 38 a and to improve the sealing performance of the plunger seal 42. Moreover, a ring-shaped metal spring 50 is inserted into the concave portion 42 a, and the sealing performance of the plunger seal 42 is further improved by the elastic force of the metal spring 50.
As described above, the fluid which has leaked from the pump chamber 38 a is stored in the concave portion 42 a on the front surface of the plunger seal 42, and thus, in the cases which the fluid to be delivered is highly corrosive to metal, the metal spring 50 inserted into the concave portion 42 a is corroded. Accordingly, under a condition where the delivery pressure is high, delivery of fluid highly corrosive to metal could not be performed. Also, in the case of using the plunger pump to deliver a mobile phase in a liquid chromatograph, even if the mobile phase is not fluid which is highly corrosive to metal, metal ions may dissolve in the mobile phase by the metal spring 50 coming into contact with the mobile phase, and a chemical reaction with a functional group or an analytical sample in a separation column may occur, possibly negatively affecting the analysis result.

SUMMARY OF THE INVENTION

The present invention aims to provide a plunger pump capable of delivering even fluid that is corrosive to metal at a high pressure.
A plunger pump, which is the target of the present invention, includes a pump body, a pump head attached to a tip end portion of the pump body, the pump head including a pump chamber, and an inlet path and an outlet path communicating with the pump chamber, a plunger whose base end is held inside the pump body and whose tip end is inserted into the pump chamber, the plunger being adapted to slide in an axial direction along an inner wall of the pump chamber, and a ring-shaped plunger seal arranged between the pump chamber and the pump body with a front surface facing the pump chamber and a back surface facing the pump body, the plunger seal including a penetration hole from the front surface to the back surface, and holding the plunger in a slidable manner with an inner wall of the penetration hole and preventing fluid leakage from the pump chamber to the pump body.
In the present invention, according to such a plunger pump, the plunger seal includes a ring-shaped hollow portion surrounding the penetration hole, an elastic member for expanding the hollow portion in a radial direction of the plunger by an elastic force is provided inside the hollow portion, the hollow portion communicates with a back surface side of the plunger seal and does not communicate with a front surface side, and a metal elastic member is not provided at a position that comes into contact, at the front surface side of the plunger seal, with fluid that is delivered.
According to the plunger pump of the present invention, since a metal elastic member is not attached to the front surface side of the plunger seal, the metal elastic member is not corroded by the fluid from the pump chamber, or metal ions are not dissolved due to the fluid from the pump chamber coming into contact with the metal elastic member. Moreover, the plunger seal includes the ring-shaped hollow portion surrounding the penetration hole, an elastic member for expanding the hollow portion in a radial direction of the plunger by an elastic force is provided inside the hollow portion, and the hollow portion communicates with the back surface side of the plunger seal and does not communicate with the front surface side, and thus, the sealing performance of the plunger seal may be improved by the elastic force of the elastic member, and the pressure resistance may be increased. Since the hollow portion provided with the elastic member is not communicated with the front surface side, even if the elastic member is made of metal, it does not come into contact with the fluid from the pump chamber, and fluid which is corrosive to metal may be delivered at a high pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional diagram showing a pump body and a pump head according to an example embodiment of a plunger pump.

FIG. 1B is a cross-sectional diagram of the pump head.

FIG. 2 is a cross-sectional diagram of a pump head according to another example embodiment of the plunger pump.

FIG. 3A is a cross-sectional diagram showing a pump body and a pump head of a conventional plunger pump.

FIG. 3B is a cross-sectional diagram showing the pump head.

DETAILED DESCRIPTION OF THE INVENTION

In another embodiment of the plunger pump, the elastic member is ring-shaped surrounding the penetration hole along the ring shape of the hollow portion. An example of the elastic member is a coil spring that is curved into a ring shape.
In another embodiment of the plunger pump, a ring-shaped pressure space is preferably provided, the pressure space communicating with the front surface side of the plunger seal and being adapted to press, in the radial direction of the plunger, the plunger seal by the pressure caused by the entering of fluid which has been delivered. Then, the sealing performance of the plunger seal may be improved at the front surface side of the plunger seal, using fluid from the pump chamber, and the pressure resistance of the plunger seal may be further increased.
The pressure space is provided inside the plunger seal, and preferably expands in the radial direction of the plunger with the increase in the internal pressure and presses the plunger seal against the plunger and the inner wall surface of the pump head. Then, the sealing between the plunger seal and the plunger, and the sealing between the plunger seal and the inner wall surface of the pump head may be improved using the fluid from the pump chamber.
Moreover, the pressure space may also be a gap provided between the outer surface of the plunger seal and the inner wall surface of the pump head. Also in this case, the sealing between the plunger seal and the plunger may be improved using the fluid from the pump chamber.
An example embodiment of a plunger pump will be described using FIG. 1.
A plunger pump includes a pump body 2, and a pump head 8 attached at a tip end of the pump body 2. A cleaning chamber 14 is provided between the pump body 2 and the pump head 8. A crosshead 4 is accommodated inside the pump body 2 in a movable manner. The crosshead 4 is biased in a direction away from the pump head 8 (in the right direction in the drawing) by an elastic body 6 such as a spring, and the crosshead 4 reciprocates along one direction (the left and right direction in the drawing) inside the pump body 2 by a cam mechanism (not shown) provided on a base end portion side of the crosshead 4 and the elastic force of the elastic body 6.
A base end portion of the plunger 3 is attached at a tip end of the crosshead 4. A tip end portion of the plunger 3 penetrates the cleaning chamber 14, and is inserted into a pump chamber 8 a provided inside the pump head 8. With the crosshead 4 being driven, the plunger 3 reciprocates along the axial direction thereof, and the tip end portion of the plunger 3 slides along the wall surface of the pump chamber 8 a. The pump head 8 includes an inlet path 8 b for drawing fluid into the pump chamber 8 a, and an outlet path 8 c for discharging the fluid from the pump chamber 8 a. Check valves 9 a and 9 b are provided on the inlet path 8 b and the outlet path 8 c, respectively, so as to prevent reverse flow.
A plunger seal attaching portion 10 is provided on a surface of the pump head 8, on the side of the pump body 2. The plunger seal attaching portion 10 is a concave portion that is coaxial with the pump chamber 8 a and has an inner diameter greater than the inner diameter of the pump chamber 8 a, and its bottom surface communicates with the pump chamber 8 a. A plunger seal 12 is inserted into the plunger seal attaching portion 10, and a backup ring 13 is inserted on the back surface side of the plunger seal 12. The plunger seal 12 has a penetration hole where the plunger 3 is to penetrate, and holds the plunger 3 in a slidable manner and prevents the fluid from the pump chamber 8 a from leaking to the side of the pump body 2. The backup ring 13 is supported by a surface, on the side of the pump head 3, of the cleaning chamber 14, and serves the role of pressing the plunger seal 12 to the side of the pump chamber 8 a.
The cleaning chamber 14 includes a path through which cleaning fluid flows, and a space where the outer circumferential surface of the penetrating plunger 3 is cleaned by the cleaning fluid. A cleaning seal 16 is provided at a portion in the internal space of the cleaning chamber 14 where the plunger 3 is to be inserted, the cleaning seal 16 holding the outer circumferential surface of the plunger 3 in a slidable manner so as to prevent leakage of the cleaning fluid. The back surface of the cleaning seal 16 is supported by a wall surface of the pump body 2.
With this delivery pump, when the plunger 3 is driven in the direction away from the pump chamber 8 a (in the right direction in the drawing), the pressure inside the pump chamber 8 a is reduced, the check valve 9 b is closed, the check valve 9 a is opened, and the fluid is drawn into the pump chamber 8 a from the inlet path 8 b. On the other hand, when the plunger 3 is driven in the direction of insertion into the pump chamber 8 a (in the left direction in the drawing), the inside of the pump chamber 8 a is pressurized, the check valve 9 a is closed, the check valve 9 b is opened, and the fluid is discharged from the pump chamber 8 a into the outlet path 8 c. Fluid is delivered with this operation being performed repeatedly.
The plunger seal 12 is made of an elastic material such as polyethylene resin. A hollow portion 12 a is provided on the back surface side of the plunger seal 12. The hollow portion 12 a is a ring-shaped hollow space which is open on the back side and is coaxial with the plunger 3. A ring-shaped metal spring (an elastic member) 18 is inserted from the back side into the hollow portion 12 a. The metal spring 18 is for applying an elastic force in the direction of pressing a part 12 c of the plunger seal 12 existing between the metal spring 18 and the plunger 3 toward the plunger 3. An example of the metal spring 18 is ring-shaped surrounding the penetration hole of the plunger seal 12, along the ring shape of the hollow portion 12 a. A concrete example of such a metal spring 18 is a coil spring that is curved into a ring shape.
According to this structure, the sealing between the inner circumferential surface of the plunger seal 12 and the outer circumferential surface of the plunger 3 is increased by the elastic force of the metal spring 18, and the fluid which has leaked from the pump chamber 8 a may be prevented from reaching the back surface side of the plunger seal 12. Since the opening of the hollow portion 12 a is on the back side, the fluid which has leaked from the pump chamber 8 a does not enter the hollow portion 12 a, and the metal spring 18 which is inserted into the hollow portion 12 a does not come into contact with the fluid which has leaked from the pump chamber 8 a. Thus, the metal spring 18 which improves the sealing performance of the plunger seal 12 is not corroded, and metal ions do not dissolve from the metal spring 18 into the fluid which is to be delivered. Accordingly, even if the fluid to be delivered is fluid which is corrosive to metal, it may be delivered under a condition of high pressure where the fluid may leak from the pump chamber 8 a to the front surface of the plunger seal 12.
Furthermore, a pressure space 12 b is provided on the front surface of the plunger seal 12, the pressure space 12 b being a concave portion which is coaxial with the plunger 3. The pressure space 12 b is formed into a ring shape surrounding the plunger 3. The pressure space 12 b expands using the increase in the pressure due to the entering of the fluid from the pump chamber 8 a, and improves the sealing between the inner circumferential surface of the plunger seal 12 and the plunger 3, and the sealing between the plunger seal 12 and the inner circumferential surface of the plunger seal attaching portion 10. Accordingly, the fluid which has leaked from the pump chamber 8 a may be even more prevented from reaching the back surface side of the plunger seal 12.
Additionally, the pressure space 12 b does not necessarily have to be provided to the plunger seal 12. For example, in the example embodiment in FIG. 2, a gap to be a pressure space is provided between the outer surface of a tip end portion of a plunger seal 22 and the inner wall surface of a plunger seal attaching portion 20 provided to the pump head 8, the pressure inside the gap is increased by the entering of fluid into the gap from the pump chamber 8 a, and the tip end portion of the plunger seal 22 is pressed toward the plunger 3. A hollow portion 22 a is provided on the back surface side of the plunger seal 22, as in the case of the plunger seal 12, and a metal spring 24, which is an elastic member, is inserted into a hollow portion 22 a from the back side. The metal spring 24 is the same as the metal spring 18 in the example embodiment in FIG. 1B. A part 22 c of the plunger seal 22 existing between the metal spring 24 and the plunger 3 is pressed toward the plunger 3 by the elastic force of the metal spring 24, and the sealing performance of the plunger seal 22 is improved. Thus, the fluid which has leaked from the pump chamber 8 a is prevented from reaching the back surface side of the plunger seal 22, and the metal spring 24 may be prevented from coming into contact with the fluid to be delivered.

Claims

The invention claimed is:

1. A plunger pump comprising:

a pump body;

a pump head attached to a tip end portion of the pump body, the pump head including a pump chamber, and an inlet path and an outlet path communicating with the pump chamber;

a plunger whose base end is held inside the pump body and whose tip end is inserted into the pump chamber, the plunger being adapted to slide in an axial direction along an inner wall of the pump chamber; and

a ring-shaped plunger seal arranged between the pump chamber and the pump body with a front surface facing the pump chamber and a back surface facing the pump body, the plunger seal including a penetration hole from the front surface to the back surface, and holding the plunger in a slidable manner with an inner wall of the penetration hole and preventing fluid leakage from the pump chamber to the pump body,

wherein the plunger seal includes a ring-shaped hollow portion surrounding the penetration hole, the hollow portion communicating with a back surface side of the plunger seal and not communicating with a front surface side of the plunger seal, and an elastic member for expanding the hollow portion in a radial direction of the plunger by an elastic force is provided inside the hollow portion, and

wherein a metal member is not provided at a position that comes into contact, at the front surface side of the plunger seal, with fluid that is delivered.

2. The plunger pump according to claim 1, wherein the elastic member has a ring shape surrounding the penetration hole along a ring shape of the hollow portion.

3. The plunger pump according to claim 2, wherein the elastic member is a coil spring that is curved into a ring shape.

4. The plunger pump according to claim 1, further comprising:

a ring-shaped pressure space communicating with the front surface side of the plunger seal, the pressure space being adapted to press the plunger seal in the radial direction of the plunger by a pressure caused by entering of the fluid which has been delivered.

5. The plunger pump according to claim 4, wherein the pressure space is provided inside the plunger seal, and is adapted to expand in the radial direction of the plunger with an increase in an internal pressure of the pressure space and to press the plunger seal against the plunger and an inner wall surface of the pump head.

6. The plunger pump according to claim 4, wherein the pressure space is a gap provided between an outer surface of the plunger seal and an inner wall surface of the pump head.