JPH05149242A - Plunger pump for liquid chromatograph - Google Patents

Abstract

(57) [Summary] [Purpose] A single pump can be used to mix two types of eluents and at the same time to deliver liquids at a constant flow rate, and to make the mixing ratio variable. [Structure] An inclined surface 14 is provided at the tip of the plunger 4, and the inside of the stroke of the inclined surface 14 is 2 within the pump head 2.
The two suction ports 16a and 16b are provided so as to face each other, and the discharge port 20 is provided at the back of the plunger 4 in the central axis direction. The plunger 4 is reciprocally movable by a support rotary table 26 and is supported so that the rotation angle around the shaft can be changed. The ratio of the eluent drawn from the two inlets is expressed as a function of the rotation angle of the plunger 4 around the axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plunger pump used as a liquid feed pump for feeding an eluent in a liquid chromatograph.

[0002]

2. Description of the Related Art In a liquid chromatograph, two kinds of eluents may be mixed and sent at an appropriate ratio. For example, in gradient analysis, two kinds of eluents are used, and the composition of the eluent is changed as the analysis progresses. The two types of eluents are mixed and flowed at an appropriate ratio, and two plunger pumps are used, the high-pressure side flow paths are connected to each other to mix the eluents with a mixer, and one pump is used. There is a system in which a three-way valve is provided on the low pressure side and the three-way valve is intermittently switched to mix at a constant ratio.

[0003]

In the method of mixing on the high-pressure side, two pumps are required, and these flow rates must be accurately controlled by the two pumps at the same time.
The device becomes complicated. In the method of mixing on the low pressure side, as in the case of mixing water and ethanol, for example, the saturated solubility of the gas after mixing becomes smaller than the saturated solubility of the gas of each eluent, and bubbles are generated. It may cause malfunction of the check valve at the pump inlet. The present invention provides a plunger pump which uses one pump and can mix two kinds of eluents at the same time, and at the same time, can send a liquid at a constant flow rate and can make the mixing ratio variable. It is intended.

[0004]

According to the present invention, a surface of the plunger reciprocating in the pump head is provided with a surface inclined with respect to the axis of the plunger, and the axial position of the inclined surface of the tip of the plunger is in the reciprocating direction. Two suction ports are provided facing each other on the wall surface inside the pump head within the range of movement to the discharge port, and a discharge port is provided inside the pump head. Also, the plunger is supported by a support rotary table, and the support rotary table supports the plunger by the guide member so that the plunger can slide in the axial direction and restricts rotation around the axis of the plunger. So that the rotation angle around the axis of the plunger can be changed.

[0005]

1 is a schematic sectional view showing an embodiment, and FIG. 2 is an exploded perspective view showing a support rotary base and a plunger of the embodiment. In order to reciprocate the plunger 4 with respect to the pump head 2, the eccentric cam 8 comes into contact with the crosshead 4 at the base end of the plunger 4, and the rotating shaft 10 of the cam 8 is rotated by the power source. 6 is provided with a return spring 12 for urging the plunger 4 in the suction direction (rightward in FIG. 1). In the range where the cam 8 rotates and the distance from the center 10 increases, the plunger 4 is pushed in the discharge direction (left direction in FIG. 1), and in the range where the distance from the center 10 decreases, the plunger 4 is pulled back by the return spring 12. Be done. In this way, the rotation of the cam 8 causes the plunger 4 to move to the pump head 2
Reciprocates inside.

A surface 14 inclined with respect to the axial direction of the plunger is formed at the tip of the plunger 4. In the pump head 2, the two suction ports 16a and 16b are provided at positions facing each other on the wall surface in the pump head 2 within a range (stroke) in which the axial position of the inclined surface 14 moves in the reciprocating direction. A discharge port 20 is provided at the back in the central axis direction. An inlet check valve 18a is provided at the suction port 16a.
Is provided, the inlet 16b is provided with an inlet check valve 18b, and the outlet 20 is provided with an outlet check valve 22.

In order to support the plunger 4 in a reciprocating manner and to restrict the rotation around the shaft, a vertical groove 24 along the axial direction is formed in the middle portion of the plunger 4, and the supporting rotary table 26 is provided. A guide member 28, which is fitted in the vertical groove 24 and guides the plunger 4 slidably in the axial direction, and which restricts the rotation of the plunger 4 around its axis, is provided inside. In order to change the rotation angle around the axis of the plunger 4, a gear 30 is circumferentially provided on the outer circumference of the support turntable 26.
A gear 32 rotated by a motor is meshed with the gear 30, and the support rotary table 26 is supported by a ball bearing 34 so as to be rotatable around the axis of the plunger 4. By rotating the gear 32, the plunger 4 can be set to a position of an arbitrary rotation angle around its axis via the support rotary table 26.

The stroke of the plunger 4 is shown in FIG.
As shown in Fig. 6, when the angle of the plunger 4 is set to 0 degree, the plunger 4 recedes most in the suction direction as shown by the solid line, and the wall surface of the tip end portion of the plunger 4 closes one suction port 16b and the broken line. As described above, the plunger 4 is most advanced in the discharge direction and the wall surface of the plunger 4 at the rearmost end of the inclined surface is between the position where the other suction port 16a is closed.

Next, the operation of this embodiment will be described with reference to FIG. (A) shows an example in which the tip end portion of the plunger 4 and the inside of the pump head are enlarged and the rotation angle around the axis of the plunger 4 is 90 degrees. Eluents sucked from the suction ports 16a and 16b are referred to as A and B, respectively. When the rotation angle around the axis of the plunger 4 is 0 degree, one of the inlets 16b is always blocked by the plunger 4 itself as shown in (B), so that the mixing ratio A: B of the two eluents is 1 : It becomes 0. When the rotation angle around the axis of the plunger 4 is 90 degrees, the two suction ports 16a and 16b are opened equally as shown in (C), so that the mixing ratio A: B is 1: 1. When the rotation angle around the axis of the plunger 4 is 180 degrees, (B)
On the contrary, the suction port 16a is always closed, and the mixing ratio A: B is 0: 1 at this time. In this way, since the tip of the plunger 4 is inclined at a constant angle, if the rotation angle around the axis of the plunger 4 is θ, the ratio of the eluents A and B sucked from the two inlets 16a and 16b. The mixing ratio A: B determined by is (1 + cos θ) :( 1-cos θ).

Since the stroke does not change even if the rotation angle of the plunger 4 is changed, the flow rate is kept constant. When changing the flow rate, the rotation speed of the cam 8 is changed without changing the stroke. Regarding the generation of bubbles, mixing is performed after passing through the check valves 18a and 18b of the suction port, and the bubbles do not stay in the check valves 18a and 18b of the suction port, and the liquid feeding operation may malfunction. There is no. Further, even if air bubbles are generated after mixing by suction, they are immediately compressed and dissolved by the plunger 4, so that they do not affect the liquid transfer. In the embodiment, the inclined surface at the tip of the plunger is a flat surface, but the rotation angle of the plunger 4 and the mixing ratio can be made proportional by changing the shape of the inclined surface at the tip.

[0011]

According to the present invention, the tip of the plunger is an inclined surface, and two suction ports are provided facing each other within the stroke range of the inclined surface, so that the rotation angle around the axis of the plunger can be changed. Two eluents can be mixed with one plunger pump, less bubbles are generated compared to the case of mixing with a three-way valve at low pressure, and stable liquid transfer can be performed. The mixing ratio can be changed by changing the rotation angle around the plunger axis.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment.

FIG. 2 is an exploded perspective view showing a support turntable and a plunger of the same embodiment.

3A and 3B are views for explaining the operation of the embodiment, FIG. 3A is a perspective view showing the inside of the pump head, and FIG. 3B is a view of the pump head when the rotation angle around the axis of the plunger is 0 degree. A sectional view, (C) shows the rotation angle about the axis of the plunger by 90 degrees.
It is sectional drawing of a pump head when it is set to degree.

[Explanation of symbols]

 2 Pump head 4 Plunger 8 Eccentric cam 12 Return spring 14 Plunger tip inclined surface 16a, 16b Suction port 20 Discharge port 24 Vertical groove 28 Guide member 26 Support rotary base 30, 32 Gear

Claims (1)

[Claims] 1. A front end of a plunger that reciprocates in a pump head is provided with a surface inclined with respect to the axis of the plunger, and the axial position of the inclined surface of the front end of the plunger is within a range of moving in the reciprocating direction. Two suction ports are provided opposite to each other on the wall surface inside the pump head, and a discharge port is provided inside the pump head. The guide member allows the plunger to slide in the axial direction and also around the shaft of the plunger. 2. A plunger pump, which is provided with a support rotary base that regulates and supports the rotation of the plunger and that can change the rotation angle around the axis of the plunger.