JP2004060513A - Liquid delivery pump for liquid chromatograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid delivery pump capable of preventing salts etc. from being produced or precipitated at/to the plunger surfaces and also its seal from wearing or damaging resulting therefrom even in case a working fluid delivered contains solids such as a buffer solution etc. <P>SOLUTION: A core 21 surface of a coat plunger 9C is coated with a coating film 20, for example DLC, of different material from the core 21, for example sapphire. This allows preventing salts etc. from being produced or precipitated at/to the surfaces of the plunger 9C and also the seal from wearing or damaging resulting therefrom even in case the working fluid delivered contains solids such as a buffer solution etc., and it is possible to establish a stable operation for a long time and improve the man-hours for maintenance operations. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid chromatography pump for a liquid chromatograph, which has a built-in plunger and reciprocates the plunger to feed liquid.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a pump mechanism of a liquid chromatograph liquid transfer pump, a plunger type pump has been mainly used in many cases. Characteristics required for the material of the plunger, which is a main component of the plunger pump, include chemical resistance and the ability to produce a smooth plunger surface to suppress wear of a seal sliding with the plunger. Sapphire and zirconia ceramics are often used as materials satisfying this property.
[0003]
Hereinafter, the structure of a conventional plunger pump (hereinafter, sometimes referred to as a pump) will be described with reference to FIGS. 2A and 2B. The rotation shaft of the motor 14, the camshaft 7, and the cam 12 shown in FIG. 2B rotate. A cam follower 13 shown in FIG. 2A circumscribes the cam 12, and the rotation of the cam 12 causes the cam follower 13 to rotate. Since the cam follower 13 and the follower shaft 3 that slides are fixed to the cylindrical crosshead 6, the rotation of the cam 12 is converted into a linear reciprocating motion of the crosshead 6 that slides on the pump head 4. Since the crosshead 6 is always urged rightward in the figure by the spring 5, the cam 12 and the cam follower 13 always maintain engagement. A cylindrical plunger 9 extends on the axis of the crosshead 6, and the volume of the working fluid chamber V periodically increases and decreases due to the reciprocating motion of the plunger 9. The check valve 1 and the check valve 8 are inserted in order to limit the flow direction of the working fluid (not shown) to be fed from below to above in FIG. Leakage of the working fluid in the direction of the crosshead 6 is prevented by the annular seal 11 surrounding the plunger 9.
[0004]
During a period in which the volume of the working fluid chamber V surrounded by the pump head 4, the seal 11, and the plunger 9 increases due to the rightward movement of the plunger 9, the working fluid is sucked into the working fluid chamber V from below in the figure. During this period, the suction of the working fluid from above in the drawing is prevented by the check valve 1. Since the check valve 8 prevents the outflow of the working fluid downward in the figure during the period in which the volume is reduced, the working fluid is discharged from the pump through the check valve 1 above the figure.
[0005]
When the working fluid is a solution in which a solid such as a buffer solution is dissolved, the salt or the like precipitates on the surface of the plunger 9 during use for a certain period of time and hinders smooth sliding with the seal 11. In step 2, it is necessary to periodically flow a washing solution such as distilled water for dissolving salts or the like, or to enclose a washing solution to remove salts and the like to recover or maintain smooth sliding. The leakage of the cleaning liquid to the outside is prevented by the seals 10 and 11.
[0006]
[Problems to be solved by the invention]
The conventional liquid chromatograph pump is as described above, but sapphire used as a main material of the conventional plunger 9 is superior in smoothness to zirconia ceramics, and generally has a seal 11. Has a longer life than zirconia ceramics. However, when the working fluid is a solution in which a solid such as a buffer solution is dissolved, the life of the seal 11 is shorter when sapphire is used as the material of the plunger 9 than when zirconia ceramics is used. The solid salt or the like strongly precipitates on the sapphire, and even if the washing liquid is repeatedly injected into the washing flow path 2 to wash the salt or the like, the supply of the washing liquid is insufficient. Solids and the like are deposited on the surface of the seal 11 and the friction between the plunger 9 and the seal 11 gradually increases, causing wear and damage of the seal 11 and shortening its life. The generation of salts and the like cannot be avoided in zirconia ceramics, though it is less than in sapphire.
[0007]
An object of the present invention is to provide a liquid chromatography pump for solving such a problem.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the liquid pump for liquid chromatography of the present invention covers the surface of the core of the plunger with a coating film made of a material different from that of the core. With this coating, the plunger can ensure chemical stability while maintaining smoothness.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The liquid pump for liquid chromatography of the present invention will be described with reference to FIGS. 1 (a) and 1 (b). Rotational movement of the cam 12 rotating around the cam shaft 7 causes linear reciprocating movement of the coat plunger 9C fixed to the crosshead 6 through rotation of the cam follower 13 and linear reciprocating movement of the crosshead 6. The volume of V is periodically increased or decreased. Since the direction of the flow of the working fluid through the working fluid chamber V is performed only from the bottom to the top of the drawing by the check valve 8 and the check valve 1, the working fluid is reversed during the period in which the volume of the working fluid chamber V increases. After passing through the stop valve 8, it is introduced into the working fluid chamber V from below, and is discharged upward through the check valve 1 during a period in which the volume of the working fluid chamber V decreases.
[0010]
As shown in FIG. 1B, the plunger pump of the present invention incorporates a coat plunger 9C in which the surface of the core 21 of the coat plunger 9C is covered with a coating film 20 made of a material different from that of the core 21. For example, sapphire is used as the core material 21 and its surface is polished smoothly, and then the coating film 20 is coated with DLC (DiamondLike Carbon, diamond-like carbon). DLC is chemically more stable than sapphire, and has a much lower tendency to be attacked by the working fluid, to react with substances contained in the working fluid, and to precipitate salts and the like in the working fluid. In FIG. 1, components denoted by the same reference numerals or symbols as those in FIG. 2 are the same as those in FIG.
[0011]
The plunger pump of the present invention is not limited to the above embodiment, and various modified embodiments can be cited. For example, the core material 21 of the coat plunger 9C is made of a cemented carbide, the coating film 20 is made of a zirconia ceramic thin film instead of the DLC film, and the zirconia ceramic thin film is made by PVD (Physical Vapor Deposition) method, or a combination thereof. For example, various core materials 21 and coating films 20 can be used. In other words, zirconia ceramics alone have poor surface smoothness as compared to sapphire, but when used as a coating film 20, a coat plunger whose smoothness depends on sapphire and whose chemical stability depends on zirconia ceramics. 9C can be realized. In the present invention, the core material 21 of the coat plunger 9C may be different from the material of the coating film 20, and the material of the core material 21, the material of the coating film 20, and the method of forming the coating film 20 are not limited. In the embodiment of FIG. 1, the end face of the coat plunger 9C is not covered, but may be covered with the covering film 20 including the end face. The present invention includes all of these.
[0012]
【The invention's effect】
Since the present invention has been described in detail above, by incorporating a plunger in which the surface of the core is covered with a coating film different from the core of the plunger, a chemically stable plunger surface is maintained while maintaining the smoothness of the core. To prevent the generation and precipitation of salts and the like on the surface of the plunger and the abrasion and damage of the seal due to it even when the working fluid contains solids such as buffer solution, thus ensuring long-term stable operation and maintenance man-hours. It is possible to realize a liquid chromatography pump for liquid chromatography that has improved the above.
[Brief description of the drawings]
FIG. 1A is a sectional view showing a structure of a plunger pump of the present invention, and FIG. 1B is a sectional view showing a structure of a plunger portion.
FIG. 2A is a sectional view showing a structure of a conventional plunger pump, and FIG. 2B is a perspective view showing a connection between a cam and a motor.
[Explanation of symbols]
6 Crosshead 9 Plunger 10 Seal 11 Seal 9C Coat plunger 20 Coating film 21 Core material V Working fluid chamber

Claims (3)

A liquid pump for liquid chromatography, comprising a built-in plunger in which the surface of a core material of a plunger is coated with a coating film made of a material different from that of the core material. 2. The liquid pump according to claim 1, wherein the core material of the plunger is made of a single crystal. The liquid pump for liquid chromatography according to claim 1, wherein the core material of the plunger is made of a cemented carbide.

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