HU198568B - Charging pump for delivering liquid in particular for flowing liquid in liquid chromatographs - Google Patents

Abstract

SUMMARY OF THE INVENTION The present invention relates to a dispensing pump for the delivery of liquid, in particular liquid fluid in liquid chromatographs, comprising pump heads (7) and damping pump heads (9) of interconnecting fluid and piston (3, 4) in pump heads (7, 9), which The invention relates to the fact that the axes of the pistons (3, -1) have an angle of between 0 ° and 180 ° to each other, the pistons (3, 4, diameters). di, dü, 15 ratio of the arc section, the coordinate system of the origin determined by the axis of rotation of the drive disc (1) [0 °; 180 ° + · χ], the Arc and [180 ° + 7; 360 °] arc segments (Ri, Rz); where the [0 °; 180 ° + ϊ] arc segment (Ri) is the Ri (f 1 = s · - + Ro, 180 + cells at the angle of 180 ° + u; 360 °) ivszaka (R2) is the di> 360 d2 γ180-és, and 20 is the casing surface case of the cam drive disc (1) to have circumferences of two. Function describes where p pistons (3, 4, stroke length, Ro is the distance from the origin of the point of 0 ° of the angle of the drive disc (1) (Fig. 2). 25 EN 198568 BA description: 6 pages, 2 drawings, Fig. 2 - 1-

Description

BACKGROUND OF THE INVENTION The present invention relates to a dosing pump for transporting liquid, in particular liquid flow through liquid chromatographs. The metering pump of the present invention is a microprocessor-controlled, stepper motor driven pump that automatically compensates for a pulsatile fluid flow by compensating for changes in dead volume due to fluid compressibility. The metering pump according to the invention is also capable of performing so-called gradient elution of three or more fluids with time varying composition by means of three or more solenoid valves. As a result, it is advantageously used in liquid chromatographs to transfer the eluate.

It is known that liquid chromatographs must be provided with a pulsatile, continuous and reproducible flow with a relatively high pressure drop (ΙΟ ⁶ -4.10 ¹ Pa). Piston or hydraulically operated diaphragm pumps are usually used to solve this problem.

Accurate and pulsatile fluid flow can only be assured by considering dead volume changes due to the compression of the fluids. The problem is exacerbated by the fact that the addition of liquids with different compressibility coefficients has to be solved at relatively wide intervals at varying speeds, pressures and temperatures.

The compressibility factor as a material characteristic itself depends on pressure and temperature.

To overcome this problem, Beckman 35 has developed a Model 112 pump, where the piston moves at a constant speed below the stroke rate, and at a very high speed below the suction stroke (pre-compression).

The disadvantage of this solution is that since fluid delivery is interrupted during the suction stroke, a pulsating fluid flow cannot be provided. It is also disadvantageous that high speed suction can lead to cavitation which can cause damage to the pump head elements. Because of the variable time pre-compression, it is difficult to ensure that the flow rate is independent of the pressure drop. During operation, the pressure 50 in the cylinder must also be measured.

Hitachi, U.S. Patent No. 4,233,156, discloses a solution where two pump heads operated at 180 ° phase displacement are provided to ensure that the flow is not pulsated. The essence of operation is that one pump head suction stroke coincides with the other pump head suction stroke. Again, the pre-compression is done at high speed. 60

The disadvantage of this solution is that, in principle, perfect pulsatility is not achieved due to the fluid wind interruption during pre-compression. A further disadvantage is that since the size of the pre-compression is a function of pressure, temperature and material quality, it is also difficult to maintain a constant throughput rate.

It is an object of the present invention to provide a dosing pump, particularly for use in liquid chromatography, to provide a fluid flow rate which is automatically compensated for the dead volume change due to the compressibility of the liquids.

The invention is based on the discovery that by using two pump heads, the pump heads are arranged in a certain relative position and the pistons are actuated asymmetrically, the error due to compressibility can be eliminated and a pulsating flow can be ensured.

To accomplish this object, a metering pump is provided which has a fluid delivery nozzle and a damping pump head, which are interconnected through a pipeline, and the piston guides in the pump heads are preferably connected by means of rollers,

- the axes of the pistons are at an angle of between 0 ° and 180 ° (180 ° - ϊ),

- ratio of piston diameters:

dt J 360 dz V 180-χ, and a

- the camshaft peripheral surface (its working surfaces are formed with two segments perpendicular to the coordinate system of origin defined by the axis of rotation of the camshaft [0 °; 180 ° + -) j] and [180 ° + ϊ; 360 °) formed by angular segments (R1, R2) where [0 °; 180 ° +}?] Of the segment

Ri (-f) = s

180 + ΐ + Ro, and the [180 ° + 360 °] segment of the iv section

Rz (f) = s · 360. ° —-. + _Ro 180 ° - ΐ function.

Preferably, the cam actuator having a circumferential surface formed in accordance with the present invention is provided with optical position sensors which are connected to an electronic control unit and a pressure sensor which controls a two-position rotary switch is connected to the pressure side of the fluid piston.

The piston of the liquid delivery pump head of the metering pump of the present invention carries the liquid, and the piston of the damping pump head provides no pulsation of the flow. The camshaft spindle has the desired flow rate3

EN 198568 rotation of the stepper motor, The pulsation and compressibility error is eliminated preferably by a microprocessor control unit that employs the pressure sensing side of the fluid positioning piston based on the optical position sensors associated with the camshaft shaft.

Due to the asymmetric arrangement and operation of the pump heads and pistons according to the invention, there is a period of operation after the pre-compression where the flow rate would increase many times the nominal speed if the drive pulley were rotated at a constant speed. Since the pressure drop in the chromatographs is proportional to the flow rate, the increase in velocity is accompanied by an increase in pressure. By exploiting this, the electronic control unit can also eliminate the pulsation of the flow while eliminating the error due to compressibility. The position of the rising edge of the speed jump depends on the pressure and the compression factor, while the angle of the falling edge is constant. The microprocessor control unit controlling the metering pump of the present invention forms a sliding average of the measured pressure values, and when the pressure value exceeds a predetermined limit, the stepping motor decreases the speed by exactly one times the flow rate at constant speed. At the signal of the optical position sensors indicating the downstream edge of the speed jump, the electronic control unit returns the stepping motor to its original speed. In this way, the flow rate remains constant,

The advantageous effect of the invention is that it provides, in accordance with the object, a pulsating fluid flow and also eliminates the error due to compressibility. Its advantageous effect is that the precise liquid dosing is not disturbed by gas bubbles, so it can even be used for soda water. A further advantage is that, by simple construction, the pistons are moved by a single drive element, the cam drive pulley, and a single pair of valves is sufficient.

The invention will now be described with reference to the drawing. In the drawing:

Figure 1 is a schematic diagram of an exemplary metering pump of the present invention,

Figure 2 shows the mutual arrangement of the cam drive discs, pumps and pistons of the metering pump according to the invention.

As shown in Figure 1, the metering pump according to the invention has a drive disk 1 which moves the first piston 3 and the second piston 4 through rollers 5. The first piston 3 is guided in the pump head 7 and the second pump 4 in the pump head 9. The pistons 3 and 4 are supported by helical springs 6 which ensure that the rollers 5 are on the peripheral surface of the drive pulley 1. The pump heads 7 and 9 are connected by piping 10.

The drive shaft 1 is driven by a stepper motor 2. In addition, optical position sensors 11 and 12 are connected to the drive shaft 1.

Valves 8 are provided in the pump head 7 to provide unidirectional flow of liquid. (Figure 2).

A pressure sensor 16 is connected to the pressure side of the piston 3.

Figure 1 shows the liquid containers 13 containing the liquids to be conveyed and provided with a filter 15. Gradient-forming solenoid valves 14 are provided in the pipe section between the fluid reservoirs and the pump head 7.

The metering pump according to the invention has a microprocessor control unit 17, with signal inputs for outputs of optical position sensors 11 and 12, pressure sensor 16 and solenoid valves. The control output of the microprocessor control unit 17 is connected to the control input of the stepper motor 2. The microprocessor control unit 17 is provided with controls 18 and a display 19.

In the above arrangement, the first plunger 3 provides fluid delivery and the second plunger 4 provides pulsation-free flow.

As shown in Fig. 2, the peripheral surface (working surface) of the drive disk 1 is formed so that its circumference is formed by two arc sections Rj and Ra. The rollers 5 are rolled by hand in an eccentric rotation of the drive pulley 1 on a peripheral surface defined by this outer circumference, thereby creating an alternate movement of the plungers 3 and 5. The direction of rotation of the drive pulley 1 and the corresponding flow direction of the liquid through the valves 8 of the pump head 7, the pipe 10 and the pump head 9 are indicated by arrows in the figure.

As shown in Fig. 2, the pump heads 7 and 9 are arranged such that the axes of the pistons 3 and 4 are at an angle (180 ° -) to each other.

With respect to the planar coordinate system perpendicular to the axis of the drive pulley, the origin of which is determined by the axis of rotation of the drive pulley 1, ° within this range. The iv sections of R1 and R2, and thus the circumference of the peripheral surface of the drive disk 1, are defined in the respective angles by: ⁺ Fo, 0 ° <γ £ 180 ° + χ

HU 198568 Β and _D 360 ° -? 180 ° - κ + Ro, 180 ° + γ £ f <360 ° where:

• f is the distance from the origin of the independent variable and the peripheral point of Ro a -f = 0 °.

The position of the plugs 3 and 4 is determined by the angular position of the drive pulley 1. Since the functions Ri (-f) and R2 (~ f) are linear functions of angle 1 * (independent variable), the instantaneous velocity of the pistons 3 and 4 depends solely on the instantaneous rotational speed of the drive pulley 1. Thus, if the drive wheel 1 is rotated evenly at a constant speed, the linear speeds of the pistons 3 and 4 will also be constant. The pistons 3 and 4 thus perform alternating motion of constant speed between two dead centers.

The velocity of the fluid flow created by the movement of the pistons 3 and 4 is proportional to the velocity and cross-section of the pistons.

The metering pump according to the invention operates as follows:

While the drive pulley 1 is rotated from = 0 ° to = angle, the rollers 5 of both the first and second pistons 4 roll over the arc portion R1 of the circumference of the drive pulley 1. Thus, the pistons 3 and 4 move fluid at the same linear velocity. As soon as the drive pulley 1 is in the angled position 2i, the second piston 4 begins to aspirate, while the first piston 3 continues to transport fluid. The flow rate provided by the metering pump will be the difference between the flow rates created by the pistons 3 and 4. When the drive pulley 1 reaches the 180 ° + position, the FORWARD piston 3 changes direction and then sucks at a constant speed, while the second piston 4 simultaneously transports fluid. At the end of the cycle, at the angle position 'f = = 360 ° (0 °), the above cycle begins again.

If the diameters of the pistons 3 and 4 are correctly selected then a

The flow velocity is constant in the angle range $ 2 ^ f ^ 360 °, while a

In the angle range 0 ° £ -f £ 2γ, this (1 +

360 °.

180 ° - ° 'times.

In determining the diameters of the 3-piston pistons, the constant flow rate is assumed. To simplify the expressions, our coordinate system is rotated by 180 ° + γ so that the position -f = 0 ° is aligned with the axis of the second piston 4.

The volume velocity Vi in the angular range 0 f f S between 180 ° and γ is given by:

_and dRi d? Π ^Vl = dt ~ 'T' where dz is the diameter of the 4 pistons.

Deriving the relationship f = wt (w is the speed of the drive wheel 1, t is the time) gives the relation dt = 1- d-f. Location:

Vi where:

Vi = ω dRi dz ² Π df 4 ′ d ² n

180 ° +2 4

The resulting flow rate of 25 Va in the 180 ° + $ <-f <360 ° angle is the a'gebra sum of the volumetric velocities generated by the piston 3 and 4:

dRi di ² Π. dR2 dz ² Π ^v · = "price · - '" d— ~ · whence

- Ri (-f) and Rz (-f) functions replaced by: -:

s di ² Π. . ⁸ d2 ² Π ^{Ve ω} '180' + γ 180 - / 4 where di is the diameter of the first 3 pistons.

The flow rate must be constant, so from the Vi = Ve condition:

^s ..... d2 ² Π.

180 + u 4 di ² n.

180 + 1 4 ⁸ dz ² n 180-1 '-

Simplifying the above expression d2 ² di ² d2 ² —— = —— -,

180 + ΐ 180 + γ 180 - γ 55 from which after rearrangement. _J J 360 ^Λ - ^d! '1Í8Ö-T;

⁶⁰ results.

If the ratio of diameters d1 and d2 of pistons 3 and 4 is chosen as described above, the fluid flow rate is

Remains constant over an angle range of 2v <-f <360 °.

HU 198568 Β

In the angular range 0 S {2 1, since here the rollers 5 of both the first piston 3 and the second piston 4 roll over the arc section R1 of the circumference of the drive disk 1, the Vu flow rate can be written as follows: 5 dRi di ² fl, dRi d? Π dt '~ 4 dt 4'

Diameters d1 and d2 replaced

Vm _ dRi dt

Ó2 between ²

360 '180 4 relationships

be10 dRi dz ² Π 15 dt 4

Claims (1)

PATENT CLAIMS Dosing pump for transporting liquid, in particular liquid flow through liquid chromatographs having a fluid transport pump head and damping pump head connected to each other, and in the pump heads guided by pistons which are connected with rollers, - the axes of the pistons (3, 4) are at an angle of 0 ° to 180 ° to each other, - ratio of diameters (di, άϊ) of the pistons (3, 4) from which: - ^dR i dt dz ² Π f 360 \ 4 'V 180 - γ) dl, Ι 360 20 - = 1 / -. and dz »180 - γ The flowrate Vi in the angular range 2γ £ -f £ 360 °: _v . _ dRi. dz ^z Π. dt 4 Thus, the cam surface of the camshaft (1) is formed such that its circumference is represented by two intersections of angles of [0 °: 180 ° + y] and [180 ° + j; 360 °] is formed by angular arc sections (R1, R2) where [0 °; 180 ° + 3] angular section (R1) of We can still state that 0 J-f < In the angular range £ 2ϊ, the flow velocity Vk is a constant of the flow velocity Vi 35 in the angular range ü £ £ 360 °, provided that the drive pulley 1 rotates at a constant rotational speed u. ? = 20 °, for example Vk = 3.25 · Vi. If the stepping motor 2 is controlled by the microprocessor control unit 17 so that the angular velocity w of the drive pulley 1 is always reduced to 3.25 in the 0 ° angle range, the fluid flow rate remains constant throughout the cycle. 45 Rií-f) = ΐ ' 180 + + Ro, the [180 ° + arc section Rz (-f) = s11; 360 °] and (R2) 360 Ϊ80 ~ -γ + Ro, where s is the stroke length of the pistons (3, 4), Ro is the distance from the origin of the circumference of the drive pulley (1) / = = 0 °. Dosing pump according to claim 1, characterized in that optical cam sensors (11, 12) are connected to the cam drive disk (1), which are connected to a microprocessor control unit (17) and a pressure sensor (16) is connected to the discharge side of the fluid piston (3). which is connected to a control signal connection by a two-position speed switch.