GB2277624A - Pump operation detector system - Google Patents

Abstract

The system comprises a pressure sensor (26) on the output side of the pump (12) which generates a signal which is fed to a control unit (20), the control unit being arranged to generate an alarm signal if it does not receive a pressure signal a predetermined time after receiving a product demand signal. A demand signal from an industrial washing machine will cause the relevant pump to pump detergent or other chemical product. This signal is also fed to the control unit of the system of the invention. A predetermined time after receiving the demand signal the control unit "looks" for a pressure signal and, if this is present, no alarm is generated. If, on the other hand, the pressure signal is absent this indicates that the pump is not working or not working properly and an alarm signal is generated. <IMAGE>

Description

PUMP OPERATION DETECTOR This invention relates to a pump operation detector in particular for use with the supply of detergents for industrial washing machines.

Industrial washing machines often have quite complex wash cycles requiring the addition of different quantities of detergents/surfactants/conditioners at different times in the cycle. Mechanised systems for supplying the various chemicals at the correct times are available and usually comprise a bank of pumps each associated with a container or reservoir of the requisite chemical product. Many of the systems incorporate a low level indicator so that an alarm signal is generated when the level of chemical drops below a predetermined figure. However, such a detector will not detect other relatively common faults in association with these pumps such as a split hose or cracked casing, which can lead to a particular product not being supplied, and the wash therefore being faulty.

The invention seeks to provide a pump operation detector improved in the above respects.

According to the present invention there is provided a pump operation detector system which comprises a pressure sensor on the output side of the pump which generates a signal which is fed to a control unit, the control unit being arranged to generate an alarm signal if it does not receive a pressure signal a predetermined time after receiving a product demand signal.

In current systems of detergent supply to industrial washing machines a demand signal from the machine will cause the relevant pump to pump detergent or other chemical product.

This signal is also fed to the control unit of the system of the invention. A predetermined time after receiving the demand signal the control unit "looks" for a pressure signal and, if this is present, no alarm is generated. If, on the other hand, the pressure signal is absent this indicates that the pump is not working or not working properly and an alarm signal is generated. In a preferred form of the invention the alarm signal actuates an audible or visible alarm at the end of the pump demand cycle.

Since the pump may take a little time to operate, or build up full pressure, after the initiation of the pump demand signal, a delay is allowed before the pressure signal is sensed after the start of the pump demand signal. In a preferred embodiment, the pressure signal is monitored all the time the pump demand signal is present and the pressure signal must be present for a set period of time, which may be a relatively short period (usually considerably less than the full period for which the pump operates) when the pump demand signal is asserted, to obtain a valid result. It does not matter if this happens to be at the beginning of a pump demand period or towards the end. This allows for different rates of pressure rise from the pump and different lengths of pump run.

The apparatus of the invention can be built into a new pump control system or can be fitted retrospectively to an existing system.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a pump operation detector system in accordance with the invention; Figure 2 is a block diagram of the control system of the system of Figure 1; and Figure 3 is a graphical representation of a typical operating sequence.

Referring to the drawings, a system in accordance with the invention generally designated 10 is illustrated for use with a pump 12 for pumping detergent to an industrial washing machine. Typically several pumps, for example six, will be employed and each will have its associated control system in accordance with the invention. The pump 12 has an inlet pipe 14 connected to a supply of the relevant product, such as a detergent, conditioner, or the like. The pump outlet pipe 16 goes to the washing machine. The pump is controlled via a timer 18 from signals received from the washing machine control unit 20.

In accordance with the invention, a connection 22 is made to the outlet pipe 16 and leads via an optional liquid trap 24 to a pressure sensor 26. The sensor 26 is chosen so that it can detect the pressure difference between ambient and the raised pressure in the delivery pipe 16 associated with the normal operation of the pump 12. The sensor 26 sends a signal PS to a control unit 28 which in turn receives a pump demand signal PD from the washing machine control 20 via the pump timer 18. The control unit 28 is capable of generating an alarm signal which may be fed to an external alarm 30 or may be applied in some other way to bring the operators attention to an alarm condition.

In operation a demand signal PD is generated by the washing machine control 20 and fed to the pump timer 18. The latter actuates the pump for a predetermined period of time for the product to be delivered from its container to the washing machine. The pump timer may be incorporated in the washing machine control 20. In this case the timer 18 is disabled and set to follow the timer in control 20. The signal is also fed to the control unit 28 which, after a predetermined time to allow the pump to reach pressure, "looks" for the pressure signal PS from the pressure sensor 26. If the pressure signal is detected for a continuous period (which may be a few seconds) while the control unit is also receiving the pump demand signal, no alarm signal will be generated.If the pressure signal does not meet these conditions or is not generated at all then an alarm signal will be generated and sent to the alarm 30 when the pump demand signal stops. This enables an operative to check the system and put right any fault before the next demand cycle.

As can be seen in figure 2 the control box 28 may contain the circuitry shown. The pressure sensor signal PS, after passing through a signal conditioning unit, is fed to a pressure register 32. Similarly the pump demand signal PD, after passing through a signal conditioning unit, is also passed to the register 32. The latter signal may also be used to set and, optionally, inhibit an alarm register 34. The pressure register 32 also feeds the alarm register 34 with an alarm signal if it does not detect the pressure sensor signal PS a predetermined time after it receives the pump demand signal PD.

In this case an output signal is sent to a pump alarm indicator 36 for that pump and, optionally, to a group alarm indicator 38 which may receive signals from other units of the invention.

The alarm register 34 may be cleared on power-up, manually over-ridden and reset by the provision of suitable facilities which may also be common to a number of other units of the invention connected to other pumps in the same group.

Turning now to figure 3, there is graphically illustrated a time diagram for a typical cycle. The upper line illustrates the turning on and off of the pump demand signal while the second line indicates the running of the pump. The third line shows the signal from the pressure sensor and it will be seen that after a small delay from when the pump actually starts running the pressure builds up to the "on" level and in order to prevent an alarm signal being generated the pressure must be at this level for a set period of time before the pump demand is removed. It will be seen from the diagram that this period is very much shorter than the full typical pump run time. If the pressure signal does not reach the "on" level, for example because of low level of product, a split tube, or a cracked casing, the control unit will activate an alarm, alerting the operative to the problem.

The system of the invention provides a simple and effective means of detecting the operation of a pump. It will be appreciated that, while the invention has been described in relation to the supply of detergent and the like to an industrial washing machine, it is not so-limited and will be broadly applicable wherever pumps are required to provide liquid intermittently.

Claims (8)

1. A pump operation detector system which comprises a pressure sensor on the output side of the pump which generates a signal which is fed to a control unit, the control unit being arranged to generate an alarm signal if it does not receive a pressure signal a predetermined time after receiving a product demand signal.

2. A system as claimed in claim 1 in which a demand signal causes a pump to pump detergent or other chemical product, this signal is also fed to the control unit and a predetermined time after receiving the demand signal the control unit "looks" for a pressure signal and, if this is present, no alarm is generated but if the pressure signal is absent an alarm signal is generated.

3. A system as claimed in either of claims 1 or 2 in which the alarm signal actuates an audible or visible alarm at the end of the pump demand cycle.

4. A system as claimed in any of claims 1 to 3 in which a delay is allowed before the pressure signal is sensed after the start of the pump demand signal.

5. A system as claimed in any of claims 1 to 4 in which the pressure signal is monitored all the time the pump demand signal is present and the pressure signal must be present for a set period of time when the pump demand signal is active to obtain a valid result.

6. A system as claimed in claim 5 in which the set period is a relatively short period, considerably less than the full period for which the pump operates.

7. A system as claimed in any of claims 1 to 6 in which a connection is made from the outlet of the pump to a pressure sensor which detects the differnce between ambient pressure and the raised pressure i the delivery pipe associated with normal operation of the pump.

8. A system according to claim 1 and substantially as hereinbefore described with reference and as illustrated in the accompanying drawings.