DE2931017C2 - High pressure pumping device, in particular for liquid chromatographs - Google Patents

Description

a) it is a low-pressure pump device (12) for delivering an adjustable amount of liquid intended;

b) there is an intermediate store (106) for receiving the liquid conveyed by the low-pressure pump device (12), with the outlet of which the suction side of the high-pressure pump (158) is connected;

c) the electronic control device (242) is connected on the input side to detector devices (140) for detecting the amount of liquid in the intermediate store (106) ; and

d) the electronic control device (242) is designed in such a way that the delivery rate of the high-pressure pump (158) is adapted to the delivery rate of the low-pressure pump device (12).

2. High-pressure pump device according to claim 1, characterized in that the intermediate store (106) has a liquid chamber with an inlet (115) and an outlet (116) which is partially delimited by a flexible membrane (132).

3. High-pressure pump device according to claim 2, characterized in that the detector devices (140) have devices for detecting the position of the flexible membrane (132) .

4. High-pressure pump device according to claim 3, characterized in that the means for detecting the position of the flexible membrane (132) have converter means for converting the detected position of the flexible membrane (132) into the quantity signal.

5. High-pressure pump device according to claim 4, characterized in that the devices for detecting the position of the flexible membrane (132) have an electrically conductive element (142) which is movable together with the flexible membrane (132) and a capacitance electrode (148 ), which is at a predetermined distance from the electrically conductive element (142) for a predetermined amount of liquid in the intermediate store (106) and that measuring devices are provided with the aid of which the capacitance between the conductive element (132) and the capacitance diode (148 ) can be measured and a corresponding quantity signal can be generated.

The invention relates to a high pressure pump device device for liquids, especially for pumping liquids in liquid chroniatographs, with a High-pressure pump, the delivery rate of which can be regulated with an associated electronic control device.

Such a high pressure pump device is described in DE-OS 27 59 056. In the known high-pressure pumping device, a high-pressure pump is controlled in such a way that the duration for filling the pump cylinder and for generating the working pressure therein is reduced to a minimum, while at the same time a maximum of time for squeezing out liquid at a high back pressure is obtained, whereby the pulsation of the pumped liquid flow is reduced to a minimum.
In the known high pressure pumping device is

to it is essential that a high-pressure metering pump that works very precisely must be used in conjunction with high-precision control equipment in order to depend a large number of correction variables on the behavior of the liquid being pumped at high pressures to consider. This leads to the fact that the known high pressure pumping device, although it is distinct Improvements over comparable, previously used high-pressure pumping devices with them brings, but overall it is relatively expensive and to a certain extent also prone to failure, which in terms of the double function the pump itself can be fed back, which on the one hand should generate a high pressure and on the other hand ai: ch is used to dose the liquid to be pumped.

Based on this prior art, the invention is based on the object of avoiding the influence of the operating parameters on the high pressure side of the pump on the regulation.
This object is achieved in the high-pressure pump device of the type specified according to the invention by the following features:
A low-pressure pumping device is provided for conveying an adjustable amount of liquid, an intermediate storage device is provided for receiving the liquid conveyed by the low-pressure pumping device, with the outlet of which the .suction side of the high-pressure pump is connected,

the electronic control device is input-connected with detector devices for detecting the amount of liquid connected in the cache, and

the electrical control device is designed in such a way that that the delivery rate of the high pressure pump is adapted to the delivery rate of the low pressure pumping device will.

In the novel concept on which the invention is based is, so it works with a low-pressure pumping device, which with very precise metering Conveys liquid at low pressure, which at least eliminates the problems that occur with high-pressure metering pumps largely avoided. The low-pressure pumping device can be a single low-pressure pump include or multiple low-pressure pumps, which in this case the same or promote several different solvents.

The amount of liquid conveyed by the low-pressure pumping device is fed to an intermediate storage device, whose liquid container is partially formed by a flexible membrane. With such a cache then leads to the increase in the amount of liquid in the liquid container that the membrane in is deflected in one direction, while a decrease the liquid leads to a deflection of the membrane in the opposite direction. These Membrane movements can be controlled with the help of suitable de-

ti5 tcktoreinrichtungcn are detected, which consequential deviations determine the amount of liquid in the intermediate storage of a given amount of liquid, where the volume, the density, the pressure and

the like can be taken into account. The detector devices are part of the electronic control system, through which the delivery rate the high pressure pump is adapted to the delivery rate of the low pressure pumping device.

In a preferred embodiment of the high pressure pump device According to the invention, the detector devices have an electrically conductive element on, which is movable together with the flexible membrane of the intermediate storage and a Capacitance electrode, which is in a predetermined amount of liquid in the intermediate storage in a predetermined distance from the electrically conductive element, the capacitance or the change in capacitance detected between the conductive element and the capacitance electrode by means of measuring devices and is converted into a corresponding quantity signal, which controls the delivery rate accordingly the high pressure pump causes.

The invention is explained in more detail below with reference to drawings. It shows

Fig. 1 is a plan view of a low pressure pumping device a high pressure pumping device according to the invention;

F i g. Figure 2 is a cross-section along line 2-2 in Figure 2. 1; F i g. 3 is a cross-section along the line 3-3 in Pi g. 1:

4 shows a cross section through an intermediate store a high pressure pumping device according to the invention;

ste pump 46 and a second pump 48 on. From Fig. 1 it is clear that the second cam 38 of the Control of the pumps 46 and 48 is used. Fig. 2 shows Einzeihe th of the second pump 48, whose structure with that of the first pump 46 is identical. As mentioned, the cam scanner 32 is assigned to the two pump 48. Form a washer 52 and a plate 54, the abutment of a helical spring 5C, which serves to keep the cam follower 32 in contact with the cam 28 to keep. The plate 54 forms one end of a housing 58 of the liquid delivery part 60 of the pump 48. The washer 52 is in turn supported by a ring 50. The cam scanner 32 is in Contact with a piston 62 which is movable to and fro in a piston chamber 64. The cam scanner 32 is guided by guide devices 66 with bearings 68 and 70. From Fig. 2 it is also clear that the piston passes through a bushing 72 which is fixed by the plate 54 with respect to the housing 58. Of the

Piston 62 is supported and guided by bearing devices 74 independently of cam scanner 32. the Lagcreinrichlungen 74 can be formed as a carbon bushing within the bushing 72, such that the Piston 72 lubricated by the bearing devices

will. Sealing devices 76 with a cup-shaped sealing element 78 serve to prevent leakage of the To prevent piston chamber 64 effectively. The conveying part 60 has an inlet 80 and an outlet 82, to which no check valves are assigned, such as

FJ g. 5 shows a plan view of the intermediate storage device, this normally occurs in the case of liquid chromatography

systems is the case. The housing 58 is by means of fasteners (Screws 88) connected to the plate 54 in such a way that the bushing 72 and the sealing devices 76. Regarding the J5 first pump 46 it should also be noted that this one Outlet conduit 90 and an inlet conduit (not shown).

Valve devices 92, which include a first valve 94 and a second valve 96, are actuated by the shaft 22 via the second cam disk 38. The above-mentioned cam scanners 40 and 42 are assigned to these valves. F i g. 3 shows details of the second valve 96, which is identical to the first valve 94. Valves 94 and% are available as double two

according to Fig. 4;

F i g. 6 shows a longitudinal section through a high-pressure pump of a high-pressure pump device according to FIG Invention;

F i g. 7 shows a cross section through the high pressure pump according to FIG. 6 along line 7-7 in this figure;

F i g. 8 is an enlarged illustration of the right-hand part of the cross-sectional illustration according to FIG. 6; F i g. 9 is a cross-section along line 9-9 in FIG. 8th;

10 shows an overall representation of a device according to the invention High pressure pumping device in the form of a Ulock diagram and

Fig. II is a block diagram of the control device of High pressure pump device according to FIG. 10.

The high pressure pumping device is shown in the drawing 45 gate valve. For example, works ntron inspo ^ mt with horn Rpyi. ^ yoirhpn in Kn / ni ^ h. the second valve% so that ultimately from the pump 48

pumped liquid from a liquid supply

Connections designated as a whole by the reference numeral 10 (Fig. 10) and comprises a Nicder pressure pump device 12 (Fig. 1), which serves to convey a metered amount of solvent. The low-pressure pumping device 12 has an electric motor 14 which drives a transmission 16, the drive shaft 18 of which is driven at a predetermined speed. A coupling 20 connects the shaft 18 with a shaft 22, which rotates at the same speed as the shaft 18

from a

(not shown) enters an inlet line 98 to which the directional arrow 100 is assigned in FIG. The cam scanner 42 actuates the valve 96 in such a way that the liquid passes the valve housing 102 to the inlet line 84 of the liquid delivery part 60. At this point the liquid flows through inlet 80 into chamber 64 where piston 62 exits it through outlet 82

turns. A bearing 24 with a flange 26 enables the 55 to push. Since the slide arrangement of the valve 96 per se w__i _ ■ __ «LH. "", .._ " . ., is known, the function of the valve should not be specified here

explained. The am Outlet 82 of the liquid conveying part 60 exiting liquid wedge through an outlet line 86 and through the

Extension of the shaft 22 up to a cam disk 28. As in FIG. 1 shows, the cam 28 is in Koniakt with cam scanners 30 and 32. The shaft 22 also passes through a bearing 34 with a flange 36.

A cam disk 38 on an extension of the WeIbo valve housing 102 through to an outlet line 104 Ie 22 behind the bearing 34 is used to actuate two conveyed (directional arrow 108) that lead to an intermediate curve 40 and 42 106 (Fig. 4) leads. The backward stroke of the KoI-faced finds shaft 22 ultimately in a bearing
44 stored. The function of the curve blazers 30, 32 of the
first cam disk 28 and the camnabtaMcr 40
and 42 of the / wide cam 38 is further unien

explained in more detail.

The low-pressure pumping device 12 has a portion 62 of the pump 48 coinciding with the flow of liquid through the inlet line 98 of the valve% and the inlet line 84 of the liquid conveyor 60. In a corresponding manner, the liquid flow falls through the outlet line 104 of the valve% and the outlet line 86 of the liquid conveying element 60 with the pre-

wärtstub the piston 62 together, in which the piston chamber 64 is emptied.

If one now looks again at Fig. 1, it becomes clear that that the cam scanners 42 and 44 actuate the slide mechanism 110 and 112 of the valves 94 and%, respectively. Coil springs 114 and 116 attached to abutments 118 and 120 are used to support the cam scanner 40 or 42 to keep in contact with the second cam 38. It should also be noted that the cam 38, the valves 94 and 96 are actuated in such a way that the intermediate store 106 flows through the valve 94 is supplied, while liquid is sucked in from the liquid supply via the valve 96 and vice versa. In this way, the intermediate storage unit 106 is provided with a steady flow of liquid at a relatively low level Pressure, but with very precise metering from the low-pressure pumping device 12 is supplied.

The in F i g. The buffer store 106 shown in FIG. 4 receives the data from the low-pressure pumping device 12 Liquid delivered via the valve means 92 at an inlet opening 115 which is connected to the outlet line 104 and a further outlet line (not shown) of the valves 96 and 94, respectively. The cache 106 has a housing 117. A channel 119 connects the inlet opening 115 with a chamber 121, to which liquid from the valve means 92 is thus supplied can be. A magnetic stirrer blade 122 mixes using a dipole stirrer 124 carefully remove the liquid from the low pressure pumping device 12 and another low pressure pumping device 139, which will be discussed below. The liquid from inlet port 115 also passes into part of a chamber 121 connected to and shown in FIG. 4 above this chamber 126. The Chamber 126 is divided into a system fluid area 128 and a capacity area by means of a membrane 132 130 divided. The liquid conveyed by the low-pressure pumping device 12 hits the membrane 132 before it reaches an outlet channel 134 and an outlet opening 136. The agitator blade 122 can consist of an inert plastic material.

F i g. 10 shows schematically a modified low-pressure pumping device 139, with the help of which an inlet opening 138 of the intermediate store 106 is another Liquid flow can be supplied. The low-pressure pumping device 139 can be constructed similarly to the low pressure pumping device 12.

The desired solvent composition or the gradient is determined by the ratio of the amounts of liquid from the low-pressure pump devices! 2 and! 39. The intermediate storage device 106 can thus accommodate a plurality of liquid flows from a plurality of low-pressure pumping devices. The mixing in the mixing chamber 121 enables the liquids, which can be different solvents, to be mixed. F i g. 4 also shows detector devices 140 for determining the amount of liquid in the intermediate storage 106. As the drawing shows, the membrane 132 has a conductive element 142 which is electrically grounded. The membrane 132 is fixed between the housing 117 and an element 144 by means of fastening devices (screws 146). The detector devices 140 have a capacitance electrode 148. which is attached to the underside of a printed circuit 150. According to FIG. 5, components 150 and 154 and a connection terminal 156 are provided on the top of the printed circuit 150. Details of the electrical circuitry of system 10 are described in greater detail below. At this point, however, it should be pointed out that the impingement of the system liquid on the flexible membrane 132 leads to a variable capacitance between the conductive element 142 and the capacitance electrode 148. Changes in the amount of liquid in the intermediate store 106 can therefore be detected by the detector devices 140. In the preferred embodiment, the amount of liquid is converted into a corresponding capacity value; so there is a capacitive converter. It should be noted, however, that the same purpose could also be achieved with optical or mechanical devices.
As the F i g. 6 to 9 show, the liquids passing through the intermediate store 106 enter a high pressure pump 158, in the exemplary embodiment a piston diaphragm pump. However, other high-pressure pumps can also be used, for example magnet armature diaphragm pumps, double piston pumps and the like, in order to increase the pressure of the liquid that is fed from the intermediate storage device 106. For example, the liquid pressure can be increased from a low positive absolute value to values of over 700 bar. The high pressure pump 158 has a housing 160 which has a jacket 162 which delimits a chamber 164. The chamber 164 contains a liquid lubricant which is shown in FIG. 6 is shown as an oil bath 166. A conventional variable speed motor M-10 (FIG. 12) drives a shaft 168 at a speed set by regulators 242. The shaft 168 is mounted in the interior of the jacket 162 in a bearing 170 and extends through an opening 172 in the jacket. A seal 174

prevents oil from escaping from the chamber 164 when the shaft 168 is running. With the aid of fastening devices 178, a cam disk 176 is connected to the shaft 168 in a rotationally fixed manner. A cam scanner 180 rests with a rotatable element 181 on the cam disk 176. The element 181 is fastened to a scanning plunger 182 with the aid of fastening devices 184. The scanning plunger 182 is mounted in a bearing 186 through which it extends and is in contact with a piston 188. According to FIG. 7, the jacket 162 has a guide surface 189 on its inside on which a guide roller 192 runs. The guide roller 192 prevents the scanning ram 182 from rotating about its axis.
The high pressure pump 158 has a liquid delivery part 190 which is connected to the jacket 162 with the aid of fastening devices (screws 194). Like F i g. 8 shows, a filler screw 196 with a ventilation screen 198 is provided at a filler opening 200. In this way, the level of the oil bath 166 can be easily maintained. The piston 188 can be moved back and forth in a guide element 202. An opening 204 ensures that a piston chamber 206 always contains oil. The piston 188 works in such a way that it extends beyond the opening 204 on its forward or working stroke and closes it (shown in dashed lines), while on its reverse stroke it closes the opening 204 The guide element 202 is held in its position by a plate 208, which is part of the jacket 162. The plate 208 also has a surface 210 which serves as an abutment for spring elements 212 and 214. One spring element 212 ensures that the cam scanner 180 in Contact with the cam 176 remains. To this

For this purpose, a fixed collar 216 for supporting the spring 212 is provided on the sampling ram 182. The spring 212 thus pushes the scanning plunger 182 away from the surface 210 of the plate 208. In a corresponding manner, a collar 218 is fastened to the piston 188 by means of a ring 220. Accordingly, the spring 214 constantly presses the piston 188 against the piston-side end 222 of the scanning plunger 182. The piston chamber 206 is closed at one end with a relatively rigid element 224, which is permeable to the oil pumped by the piston 188 due to its porosity. Adjacent to the porous element 224 is a relatively flexible membrane 226 which is impermeable to the oil being pumped. The flexible membrane 226 forms one side of a liquid chamber 228 of the liquid delivery part 190. The membrane 226 is shown in FIG. 9 is acted upon by a compression spring 230 in the chamber 228. The liquid conveying part 190 has an inlet opening 232 and an outlet opening 234. The inlet opening 232 is supplied with liquid from the outlet opening 136 of the intermediate storage unit 106. The inlet opening 232 and the outlet opening 234 are provided in a manner known per se with check valves which ensure that the liquid wedge only flows in the direction shown in FIG. 8 arrows shown can flow. The liquid entering at the inlet port 232 flows into the chamber 228 via a channel 236. When movement of the diaphragm 226 due to the pumping action of the piston 188 results in a reduction in the volume of the chamber 228, the liquid therein is forced into a channel 238 which communicates with the outlet port 234 , which in turn is connected to the desired port. In a liquid chromatograph, the liquid exiting outlet port 234 enters a tightly packed column 240, as shown in FIG. 10 is indicated schematically. If a check valve fails, the membrane 226 can be supported on the porous element 224 so that it is not destroyed.

Fig. 10 shows the high pressure pump device 10 schematically. It can be seen that the low-pressure pumping device 12 with the two pumps 46 and 48 and the valves 94 and 96 and / or similarly constructed low-pressure pumping devices 139 deliver liquid to the intermediate store 106, where a quantity of liquid is accumulated. The liquid flow from the intermediate store 106 is fed to the high pressure pump 158 and then to the column 240. The detector devices 140 detect the amount of liquid in the intermediate store 106 and generate a signal corresponding to the detected amount of liquid, which is fed to the control device 242. The regulating device 242 compares the quantity signal with a reference signal and generates an error signal which regulates the delivery quantity of the high-pressure pump 158. The aim of this regulation is to keep the amount of liquid in the intermediate store 106 at a predetermined value. When considered embodiment, the delivery rate is the high pressure pump 158 governed by the voltage level for which the shaft 168 driving motor conveyed by the high pressure pump 158 liquid quantity is therefore equal to that of the low-pressure pump devices 12 and / or another low pressure Pumping devices delivered amount of liquid. A monitoring device 268 can determine the composition and / or the gradient of the solvents supplied by any number of low-pressure pump devices. In addition, sample injection devices 270 are provided with the aid of which the sample to be analyzed can be added to the solvent flow on the outlet side of the high pressure pump 158.

F i g. 11 shows a block diagram of a preferred embodiment of the regulating device 242. As described above, the regulating device 242 is supplied with a quantity signal by the detector devices 140 and converted into a signal which regulates the delivery quantity on the outlet side of the high-pressure pump 158. In detail, the control device 242 comprises an oscillator 244 which supplies a signal 252, the frequency of which is inversely proportional to the capacitance between the capacitance electrode 148 and the conductive element 142 of the membrane 132. The frequency signal 252 is converted with the aid of a frequency / voltage converter 246 into a voltage signal 253, which is fed to a summing amplifier 248. A reference voltage generator 250 supplies a further voltage signal 256 for the summing amplifier 248, which signal corresponds to a predetermined amount of liquid in the collector 106. The summing amplifier 248 then generates a voltage signal 258 which determines the speed or rotational speed of the motor for the high pressure pump. It should be noted that the motor can be a simple, well-known DC motor. It is clear from the above that an increase in the delivery rate of the low-pressure pump device 12 leads to an increase in the amount of liquid in the intermediate store 106 . Such an increase is detected by the detector 140 and signaled to the control device 242, which thereupon increases the delivery rate of the high-pressure pump 158 . The increase in the delivery rate of the pump 158 tends to reduce the amount of liquid in the intermediate storage unit 106. The zero edge loop of the control device 242 described above thus regulates the high-pressure pump 158 as an auxiliary unit as a function of the operating conditions of the low-pressure pumping device 12 and / or other low-pressure pumping devices as the main unit or main units.

An actuator 266 (FIG. 1) determines a selected speed of the motor 14 and thus one selected delivery rate of the low-pressure pumping device 12. The actuating device 266 (FIG. 1) can comprise a drive module with an associated pulse generator. The drive module and the pulse generator can do this for your part with a simple

so variable resistor or potentiometer can be set, which has a setting range of 500 kOhm In this way there is the possibility that the user can reduce the speed of the Stepper motor 14 adjusts on a potentiometer. The setting of the engine speed can also be done automatically take place according to a predetermined program.

When working with the high-pressure pumping device, the user first sets the desired speed of the stepping motor via the setting device 266

bo 14 a. In this way, the delivery speed for the low-pressure pump device 12 is preselected, which can correspond to a pressure value which is required in order to force liquid through the column 240 . The motor 14 now drives the shaft 18, which in turn drives the pumps 46 and 48 and the valves 94 and% in such a way that a carefully metered amount of liquid is conveyed to the intermediate store 106 at low pressure. This liquid happens to

Intermediate storage 106 and enters high pressure pump 158. In this case, the buffer 106 forms the
Node for a feedback system that regulates the speed of the motor M-IO that controls the pump
drives. The detector 140 and the control device 242 form a zero control loop with their
Help the correct flow rate for the high pressure pump 158 is maintained. The one from pumps 158
Pumped liquid is then passed through column 240
of a liquid chromatograph. 10

In addition 5 sheets of drawings

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Claims (1)

Patent claims: 1. High pressure pumping device for liquids, especially for pumping liquids in liquid chromatographs, with a high pressure pump, the delivery rate of which with an associated electronic Control device is controllable, characterized by the following features: