JP3119380U - Feed pump - Google Patents

Abstract

Provided is a liquid feed pump capable of preventing particulate matter such as wear powder from flowing into a check valve in a plunger pump and thus capable of liquid feeding with high accuracy even in a low flow rate region.
A pressure sensor for detecting a pressure of a fluid in a pump chamber and a pressure monitoring means for monitoring a pressure in the pump chamber based on an output signal thereof are provided. Is provided. With this configuration, particulate matter such as wear powder is prevented from flowing into the outlet check valve 6, and the pressure in the pump chamber 4 is monitored for maintenance of the filter 33. The clogging status of the filter 33 can be checked.
[Selection] Figure 1

Description

  The present invention relates to a liquid delivery pump suitable for use in liquid chromatography for liquid phase.

  Since a liquid feed pump in liquid chromatography is required to send a liquid at a high pressure and an accurate flow rate, a plunger pump is mainly used. The basic configuration of the plunger pump includes a plunger that is driven by a motor via a cam and reciprocates in the pump chamber, and check valves provided respectively at the inlet and outlet of the pump chamber. FIG. 3 shows the basic configuration of such a conventional liquid chromatograph feed pump.

Hereinafter, the structure and operation of a conventional liquid feed pump will be described with reference to FIG.
In the figure, 1 is a pump head, 2 is a plunger, 3 is a plunger seal that allows the plunger 2 to slide while preventing liquid leakage, 4 is a pump chamber formed in the pump head 1, and 5 and 6 are respectively An inlet check valve and an outlet check valve provided at the inlet and outlet of the liquid to be fed. 7 is a pump body, 9 is a spring, 10 is a crosshead, 11 is a cam that is rotationally driven by a motor 20, and 12 is a cam follower that rolls along the periphery of the cam 11.

  The plunger 2 has a distal end side (right side in FIG. 3) inserted into the pump chamber 4 through the plunger seal 3 and a proximal end side (left side in FIG. 3) connected to the cross head 10. The cross head 10 has a cylindrical shape due to a forward force (rightward in FIG. 3) applied from the rotating cam 11 via the cam follower 12 and a backward force (leftward in FIG. 3) applied by the spring 9. The reciprocating motion is performed in the pump body 7. In conjunction with this movement, the plunger 2 reciprocates in the pump chamber 4, and by this movement, pressurization and depressurization are alternately repeated in the pump chamber 4. The flow of the liquid from the inlet to the outlet is generated by the action of the outlet check valve 6), and the liquid is fed.

  In order to increase the flow rate accuracy at high pressure with such a plunger pump, it is necessary to correct the volume decrease due to the compression of the liquid. In the compression rate correction, the pressure sensor 8 provided in the external flow path on the outlet side detects the liquid feeding pressure, the flow rate correction value is obtained from the pressure by the compression rate correction unit 22, and this is fed back to drive the cam 11. This is done by controlling the number of rotations of the motor 20 via the motor control unit 21 (see, for example, Non-Patent Document 1). The compression rate correction unit 22 is configured by software in a pump control computer (not shown).

Asai, et al. “Single Small Plunger Pump for High Performance Liquid Chromatographs” Shimadzu review, Shimadzu, December 1979, P75-81

In the plunger pump configured as described above, the abrasion powder of the plunger seal generated by friction between the plunger and the plunger seal may flow into the outlet check valve and hinder the valve function. That is, the wear powder is caught and the valve is not completely closed, so that a backflow (leakage) of the liquid occurs, resulting in a decrease in liquid feeding accuracy. In particular, in a minute flow rate liquid pump that has been increasing in demand in recent years, even if a slight leak occurs, the liquid feed accuracy is greatly reduced, and thus prevention of leak in the check valve is an important issue.
The present invention has been made in view of such circumstances, and prevents particulate matter such as wear powder from flowing into the check valve in the plunger pump, so that highly accurate liquid feeding can be performed even in a low flow rate region. An object is to provide a possible liquid pump.

  In order to solve the above-mentioned problem, the present invention provides a pressure sensor for detecting the pressure of fluid in the pump chamber and a pressure for monitoring the pressure in the pump chamber based on the output signal while providing a filter at the valve inlet of the outlet check valve. Monitor means are provided. With this configuration, particulate matter such as abrasion powder is prevented from flowing into the outlet check valve, and the filter is clogged by monitoring the pressure in the pump chamber for maintenance of the filter. You can check the situation.

Since the present invention is configured as described above, the backflow (leakage) of the liquid in the outlet check valve can be suppressed, and the liquid feeding accuracy is improved particularly in the low flow rate range, and the condition of clogging of the filter can be reduced. Since it can be checked, proper maintenance of the filter becomes possible.
In addition, since the compressibility correction works effectively against a change in the liquid supply pressure due to a change in the clogged state of the filter, high liquid supply accuracy is maintained.

The liquid feed pump provided by the present invention has the following characteristics. That is, the first feature is that a filter is provided at the valve inlet of the outlet check valve, and the second feature is that the device is provided with means for monitoring the pressure in the pump chamber.
Therefore, the basic configuration of the best mode is a liquid feed pump having the above two cases.

FIG. 1 shows an embodiment of the present invention. In the figure, the same functional elements as those in FIG. 3 are omitted in FIG. 1 because components other than the pressure sensor 8 are not directly related to the present invention.
The characteristic configuration of this embodiment is that a filter 33 is provided at the inlet of the outlet check valve 6 and that a pressure sensor 8 for detecting the liquid feeding pressure is directly connected to the pump head 1 and further its output signal. Pressure monitoring means 23 for monitoring the above is provided. As the filter 33, a collection of fine particles and fibers such as metal (stainless steel), resin (fluororesin, PEEK), glass, etc. is used. Prevent leakage at the stop valve 6. The filter 33 is configured to be replaceable when clogged.

FIG. 2 shows an enlarged cross-sectional view of the outlet check valve 6.
This example is a ball check valve having a ball 31 and a ball seat 32 as main components, and its action as a check valve is well known. A screw 34 provided on the outer periphery of the cylindrical valve body 30 is screwed into the pump head 1, and a filter 33 is fitted to the fluid inlet (lower side in FIG. 2). When the filter 33 is clogged, the screw 34 can be loosened to remove the outlet check valve 6 from the pump head 1 and the filter 33 can be replaced.

  The pressure sensor 8 is used to know the replacement time of the filter 33. As described above, the pressure sensor 8 is provided for the purpose of correcting the compression ratio. In the present embodiment, the pressure sensor 8 is also used for monitoring the clogging state of the filter 33. That is, when the filter 33 is clogged, the resistance increases, so that a higher pressure is required to send liquid at the same flow rate, and the pressure in the pump chamber 4 increases. Therefore, by monitoring the output signal of the pressure sensor 8 for detecting the pressure in the pump chamber 4 with the pressure monitor means 23, information for knowing the replacement time of the filter 33 can be obtained.

  In the simplest case, the pressure monitor means 23 may simply display the output signal of the pressure sensor 8 on an appropriate display device. A skilled operator can determine the replacement time by checking this at any time. The pressure monitoring means 23 may be configured to automate this operation using a judgment function of the computer and to send an alarm for filter replacement when the output signal of the pressure sensor 8 exceeds a set limit value. Good. In any case, such means itself can be easily designed and manufactured within the scope of the current technical knowledge, and can be realized by software in a computer in the same manner as the above-described compression rate correction.

  Although the pressure sensor 8 is also used for correcting the compression ratio, in the present invention, the pressure in the pump chamber 4 corresponding to the upstream side of the filter 33 is detected and corrected, so that the pressure change due to clogging of the filter 33 is detected. Also, the compression rate correction works effectively, and the flow rate of the liquid feeding does not change depending on the degree of clogging of the filter 33. That is, the liquid feeding accuracy is not lowered by providing the filter 33.

  The above embodiment is an example of a single plunger pump that feeds liquid by only one pump, but also for a known double plunger pump that uses two pumps connected in series or in parallel to suppress pulsating flow. Similarly, the present invention can be applied.

  In addition, although the said Example is an example which used the ball | bowl check valve as a check valve, you may use check valves of other systems, such as a diaphragm valve and a reed valve. The pressure sensor 8 is not limited to the one directly connected to the pump head 1, and can be provided at an arbitrary position where the internal pressure of the pump chamber 4 can be detected.

  The present invention can be used for liquid chromatography.

It is a figure which shows one Example of this invention. It is the elements on larger scale of one Example of this invention. It is a figure which shows the conventional basic composition.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump head 2 Plunger 3 Plunger seal 4 Pump chamber 5 Inlet check valve 6 Outlet check valve 7 Pump body 8 Pressure sensor 9 Spring 10 Cross head 11 Cam 12 Cam follower 20 Motor 21 Motor control part 22 Compression rate correction part 23 Pressure monitor Means 30 Valve body 31 Ball 32 Ball seat 33 Filter 34 Screw

Claims (1)

In the liquid feed pump configured to cause a fluid flow from the inlet toward the outlet by reciprocating a plunger in a pump chamber having an inlet check valve and an outlet check valve at the inlet and the outlet, respectively, A filter is provided at the inlet of the outlet check valve, and is disposed at a position communicating with the pump chamber to detect the pressure of the fluid in the pump chamber, and the pump chamber pressure is monitored based on an output signal of the pressure sensor. A liquid feed pump comprising pressure monitoring means.

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