GB1596633A - Fluid pump control for liquid sampling - Google Patents

Description

(54) FLUID PUMP CONTROL FOR LIQUID SAMPLING (71) We, THE HORSTMANN GEAR COMPANY LIMITED, a British Com- pany, of Newbridge Works, Bath BA1 3EF, Avon, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the control of pumps used in the automatic analysis of the chemical constitution of substantially liquid samples.

Typically, such a system of automatic analysis comprises a Sampler which couples one after another small samples of fluids to be examined at the inlet of a pump, the characteristics of which pump is to maintain an approximately constant flow against often widely varying hydraulic impedances.

On passing through the pump the sample is mixed with a predetermined amount of chemcial reagent, which is also pumped: the resulting chemical interaction can be detected electronically and a voltage proportional to the degree of chemical interaction may be conveniently displayed on a recorder in such a manner that a given value or peak can be correctly assigned to its sample origin.

Typically, such systems work on a batch basis, in which a number of samples are presented sequentially by the sampler to the pump, and are analysed and recorded. This sequence is then followed by an idling period during which no samples pass through the system but during which reagent continues to flow. Continuous flow of reagent has been found necessary to ensure immediate availability of function, since hydraulic stalling of the reagent flow can cause settling out of chemical constituents and consequent blockage of the tubes used to conduct them.

The invention seeks to reduce the consumption of reagent consistent with satisfactory continuous operation and immediate availability of function on demand.

According to one aspect of the invention there is provided a method of feeding batches of liquid samples for analysis, comprising feeding the samples in succession from a batch of samples through an analyser, pumping a reagent into the sample feed flow prior to analysis and maintaining a flow of the reagent at a reduced rate during non sampling periods by intermittent pumping action during the period between the feed of samples from the said batch and the feed of samples from a subsequent batch.

According to a second aspect of the invention there is provided a liquid sampling apparatus, comprising means for feeding samples through an analyser, a pump for pumping a reagent into the sample feed upstream of the analyser and means for actuating the pump intermittently to maintain a flow of reagent at a reduced rate.

The means for feeding samples may be a pump and the or each pump may be a peristaltic pump.

In a preferred form the reagent pump is driven electrically. In this case the means for actuating the pump intermittently comprises a pulse producing circuit arranged to connect the electrical drive repetitively at intervals. This may comprise a pulse generator feeding a monostable trigger circuit and the repetition rate and/or the on period of the monostable trigger circuit may be selectively variable to adjust the reagent flow rate.

In order that the invention and its various other preferred features may be understood more easily, embodiments thereof will now be described, by way of example only, with reference to the drawings, in which: Figure 1 is a schematic illustration of an automatic analysis equipment incorporating the features of the present invention, Figure 2 is a graphical representation showing the function of pulse generator and monostable circuit of Figure 1; Figure 3 shows an alternative sampling arrangement usable with the arrangement of Figure 1.

In the drawing of Figure 1 a sampler 10 comprises a sample holder 11 in the form of a circular plate having a multiplicity of holes 12 arranged on a common pitch circle diameter. The sample holder 11 is mounted for rotation in steps by a motor 13. The holes 12 are provided for receiving tubular containers 14 containing samples of liquid to be analysed and the stepped rotation of the sample holder 11 presents each tube in turn at a sampling position 15. A dipping device 16 has an arm 17 which can be lowered and raised repetitively in synchronism with the stepped rotation of the holder 11 and is provided with a dip pipe 18 which is dipped into the liquid sample in each tube in turn.

The dip pipe 18 is coupled to a peristaltic pump 19.

A reservoir 21 containing a reagent for mixing with the liquid samples for analysis purposes is coupled with the pump 19 via a line 22. The reagent line and sample line run separately through the pump 19 and are combined at the outlet side of the pump by means of a "T" connector 23 and are mixed before passage through an analyser 24 which detects electronically the resultant chemical reaction and produces a voltage proportional to the degree of chemical interaction. The voltage produced can be displayed on a recorder or indicator in such a manner that a given value or peak can be correctly assigned to its sample origin or may be used to control a process from which a sample is derived.

During the analysis of the batch of samples in the holder 11 the pump is required to be driven continuously by a motor 25. This analysis is followed by an idling period during which a new batch of samples are provided in the carrier 11 and during which no samples pass through the analyser 24.

During the idling period it has been found necessary to maintain a flow of reagent to prevent settling out of chemical constituents and to ensure that the equipment is in a stand by condition in which it is immediately available for analysis of a new batch of samples. However, it is only necessary to maintain a much lower minimum flow rate consistent with continuous movement of the reagent. This can be effected by a pulsed operation of the pump whereby continuity of movement is effected by virtue of the inertia of the reagent flow.

A pulsed operation of the pump is effected by supplying pulses of electrical energy to the motor by means of a pulse or square wave generator 26 which feeds a monostable circuit 27 the output pulses of which effect operation of a switch 28, e.g. a Triac switch, to provide drive to a motor at spaced intervals in time. The output of the pulse generator is shown in Figure 2a and that of the monostable circuit in Figure 2b.

In the illustrated embodiment the pulse generator 26 provides a constant repetition rate of periodic time 5 seconds and the monostable circuit 27 has a pulse output period which is variable in length between for example 1/4 sec and 5 seconds. The pulse generator 26 and monostable circuit 27 may be provided by a single integrated circuit e.g. CD4093B wired in a conventional manner.

An alternative arrangement is to provide a monostable circuit which provides a fixed pulse length e.g. 1/4 second and to drive this by a pulse generator of variable repetition rate e.g. variable between 1/4 and 5 seconds.

The switch 28 is short circuited by a switch 29 when the motor is required to operate continuously during sampling of a batch or alternatively the pulse rate or width at the output of the monostable circuit 27 may be adjusted to provide a continuous switching voltage to the switch 28. The continuous operation may be effected by a manual switching function or by an automatic switching function when the sampler is in operation.

It will be appreciated that the quantity of reagent relative to the flow of the sample needs to be known and accurately controlled. The relative quantity of reagent is a function of the relative cross sectional dimensions of the pipes which feed them and accordingly to alter the percentage of reagent it is only necessary to alter the dimensions of its flow line.

An alternative sampler arrangement is shown in Figure 3 in which each sample container 14 is connected through a peristaltic pump 19 via a respective line 31 the multiple outlet being fed to a selector 32 which is arranged to route each line in turn to the "T" connector 23 for mixing with reagent before passage to the analyser 24.

Although the pump drive described herein is operated electrically it will be appreciated that an analogous function could be effected by a fluid drive arrangement and fluidic pulse generation.

WHAT WE CLAIM IS: 1. A method of feeding batches of liquid samples for analysis, comprising feeding the samples in succession from a batch of samples through an analyser, pumping a reagent into the sample feed flow prior to analysis and maintaining a flow of the reagent at a reduced rate during non sampling periods by intermittent pumping action during the period between the feed of samples from the said batch and the feed of samples from a subsequent batch.

2. A liquid sampling apparatus. com-

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (14)

**WARNING** start of CLMS field may overlap end of DESC **. monostable circuit of Figure 1; Figure 3 shows an alternative sampling arrangement usable with the arrangement of Figure 1. In the drawing of Figure 1 a sampler 10 comprises a sample holder 11 in the form of a circular plate having a multiplicity of holes 12 arranged on a common pitch circle diameter. The sample holder 11 is mounted for rotation in steps by a motor 13. The holes 12 are provided for receiving tubular containers 14 containing samples of liquid to be analysed and the stepped rotation of the sample holder 11 presents each tube in turn at a sampling position 15. A dipping device 16 has an arm 17 which can be lowered and raised repetitively in synchronism with the stepped rotation of the holder 11 and is provided with a dip pipe 18 which is dipped into the liquid sample in each tube in turn. The dip pipe 18 is coupled to a peristaltic pump 19. A reservoir 21 containing a reagent for mixing with the liquid samples for analysis purposes is coupled with the pump 19 via a line 22. The reagent line and sample line run separately through the pump 19 and are combined at the outlet side of the pump by means of a "T" connector 23 and are mixed before passage through an analyser 24 which detects electronically the resultant chemical reaction and produces a voltage proportional to the degree of chemical interaction. The voltage produced can be displayed on a recorder or indicator in such a manner that a given value or peak can be correctly assigned to its sample origin or may be used to control a process from which a sample is derived. During the analysis of the batch of samples in the holder 11 the pump is required to be driven continuously by a motor 25. This analysis is followed by an idling period during which a new batch of samples are provided in the carrier 11 and during which no samples pass through the analyser 24. During the idling period it has been found necessary to maintain a flow of reagent to prevent settling out of chemical constituents and to ensure that the equipment is in a stand by condition in which it is immediately available for analysis of a new batch of samples. However, it is only necessary to maintain a much lower minimum flow rate consistent with continuous movement of the reagent. This can be effected by a pulsed operation of the pump whereby continuity of movement is effected by virtue of the inertia of the reagent flow. A pulsed operation of the pump is effected by supplying pulses of electrical energy to the motor by means of a pulse or square wave generator 26 which feeds a monostable circuit 27 the output pulses of which effect operation of a switch 28, e.g. a Triac switch, to provide drive to a motor at spaced intervals in time. The output of the pulse generator is shown in Figure 2a and that of the monostable circuit in Figure 2b. In the illustrated embodiment the pulse generator 26 provides a constant repetition rate of periodic time 5 seconds and the monostable circuit 27 has a pulse output period which is variable in length between for example 1/4 sec and 5 seconds. The pulse generator 26 and monostable circuit 27 may be provided by a single integrated circuit e.g. CD4093B wired in a conventional manner. An alternative arrangement is to provide a monostable circuit which provides a fixed pulse length e.g. 1/4 second and to drive this by a pulse generator of variable repetition rate e.g. variable between 1/4 and 5 seconds. The switch 28 is short circuited by a switch 29 when the motor is required to operate continuously during sampling of a batch or alternatively the pulse rate or width at the output of the monostable circuit 27 may be adjusted to provide a continuous switching voltage to the switch 28. The continuous operation may be effected by a manual switching function or by an automatic switching function when the sampler is in operation. It will be appreciated that the quantity of reagent relative to the flow of the sample needs to be known and accurately controlled. The relative quantity of reagent is a function of the relative cross sectional dimensions of the pipes which feed them and accordingly to alter the percentage of reagent it is only necessary to alter the dimensions of its flow line. An alternative sampler arrangement is shown in Figure 3 in which each sample container 14 is connected through a peristaltic pump 19 via a respective line 31 the multiple outlet being fed to a selector 32 which is arranged to route each line in turn to the "T" connector 23 for mixing with reagent before passage to the analyser 24. Although the pump drive described herein is operated electrically it will be appreciated that an analogous function could be effected by a fluid drive arrangement and fluidic pulse generation. WHAT WE CLAIM IS:

1. A method of feeding batches of liquid samples for analysis, comprising feeding the samples in succession from a batch of samples through an analyser, pumping a reagent into the sample feed flow prior to analysis and maintaining a flow of the reagent at a reduced rate during non sampling periods by intermittent pumping action during the period between the feed of samples from the said batch and the feed of samples from a subsequent batch.

2. A liquid sampling apparatus. com-

prising means for feeding samples through an analyser, a pump for pumping a reagent into the sample feed upstream of the analyser and means for actuating the pump intermittently to maintain a flow of reagent at a reduced rate.

3. A liquid sampling apparatus as claimed in Claim 2 wherein the means for feeding samples comprises a pump.

4. A liquid sampling apparatus as claimed in Claim 2 or 3, wherein the pump(s) is/are peristaltic pump(s).

5. A liquid sampling apparatus as claimed in any one of Claims 2 to 4, wherein the reagent pump is driven electrically.

6. A liquid sampling apparatus as claimed in Claim 5, wherein the means for actuating the pump intermittently comprises a pulse producing circuit arranged to connect the electrical drive repetitively at intervals.

7. A liquid sampling apparatus as claimed in Claim 6, wherein the pulse producing circuit comprises a pulse gener ator feeding monostable trigger circuit.

8. A liquid sampling apparatus as claimed in Claim 7, wherein the repetition rate of the pulse generator is selectively variable.

9. A liquid sampling apparatus as claimed in Claim 7 or 8, wherein the on time period of the monostable circuit is selective ly variable.

10. A liquid sampling apparatus as claimed in any one of claims 2 to 9 including a sampler for feeding sequentially samples from a batch of liquid samples to the analyser.

11. A liquid sampling apparatus as claimed in Claim 10, wherein the sampler comprises a holder for a multiplicity of separate sample containers, a dip pipe for insertion into the sample containers and means for effecting insertion and retraction of the dip pipe into each sample container in turn to enable feed of the sample to the analyser.

12. A liquid sampling apparatus as claimed in Claim 10, wherein the sampler comprises a holder for a multiplicity of separate sample containers, a pipe for each sample container communicating between the container and a pump arranged to feed each sample separately and a selection means arranged to select each feed in sequence for connection to the analyser.

13. A method of feeding liquid samples for analysis substantially as described herein with reference to the drawings.

14. A liquid sampling apparatus substantially as described herein with reference to, or as illustrated in, the drawings.