GB2139793A

GB2139793A - Automatic bilge pump monitor

Info

Publication number: GB2139793A
Application number: GB08411766A
Authority: GB
Inventors: Kevin Martin Ross
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-05-13
Filing date: 1984-05-09
Publication date: 1984-11-14
Also published as: NL8401540A; IT8420882A1; FR2545780A1; GB8411766D0; IT8420882A0; IT1196106B; AU2786884A

Abstract

The present invention relates to an automatic bilge pump apparatus comprising an automatic means for energising and de-energising the pump in response to sensed water level and an alarm means arranged to give a warning when the bilge pump has been continuously operating for more than a predetermined period. A triggerable monostable timer circuit for use with the bilge pump monitor is also disclosed.

Description

SPECIFICATION Alarm means The present invention relates to an audible alarm means. Boats typically comprise an automatic bilge pump which is designed to pump water out of the bilge of the boat as required. Under normal operating conditions the bilge pump should reduce the water level in the bilge to an acceptable level within a relatively short time, such as less than one minute.

However, under certain circumstances the bilge pump may not be able to reduce the water level in the bilge to an acceptable level in a relatively short space of time, such as 15 to 30 seconds. This may happen if, for example, the boat is damaged in some way so that the amount of water flowing into the bilge is much greater than normal and greater than the capacity of the bilge pump. Alternatively, the bilge pump may be jammed or partially jammed so that it is not operating at all or is operating at a reduced rate. In some circumstances, the automatic control for the bilge pump may malfunction and the bilge pump may continue running for long periods of time leading to accelerated wear and tear on the bilge pump and causing the battery of the boat to become discharged.

It is known to provide a lamp which may become lit when the blige pump is operating so that people on the boat have an indication of the operation of the bilge pump. However, under practical conditions of operating a boat, this visual signal may not be noticed at all or may be noticed and disregarded because no one is aware that it is has been on for more than say 1 minute.

If the bilge becomes flooded the boat can sink which is especially dangerous at sea. If the pump is operating needlessly it will wear out more quickly so prematurely necessitating expensive replacement.

In accordance with one aspect of the present invention there is provided an automatic bilge pump apparatus comprising an automatic means for energising and de-energising the pump in response to sensed water level, and an alarm means arranged to give a warning when the bilge pump has been continuously operating for more than a predeter mined period.In accordance with a further aspect of the present invention there is provided a triggerable monostable timer circuit for use with a bilge pump comprising a first RC network rated at a relatively high value, a second network rated at a relatively low value, an integrated circuit, a connection between the first RC network and a threshold pin of the integrated circuit, a connection between the second RC network and a trigger pin of the integrated circuit, a connection between an output pin of the integrated circuit and an alarm means and a connection between a further pin of the integrated circuit and - the source of power, the second RC network being arranged to set the integrated circuit when the power is supplied to the triggerable monostable timer circuit, the first RC network being arranged to be monitored by the integrated circuit such that when the sensed voltage at the threshold pin reaches a predetermined proportion of the supply voltage of the source of power, the connection from the output pin to the alarm means suppplies power to the alarm means.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a general view of an activating circuit for an automatic bilge pump including an audible alarm means; and Figure 2 is a detailed drawing of one embodiment of a circuit which may be used to provide an audible alarm for the circuit of Figure 1.

In Figure 1, there is shown an activating circuit 9 for an automatic bilge pump 10. The circuit comprises a float switch 12 in electrical communication with a fuse 13 and a source of power 14, such as a battery, and the bilge pump 10. The float switch 12 is also in electrical communication with a lamp 16 which provides a visual indication of when float 12 contacts are closed and the fuse 13 is intact. The lamp 16 may be located on a console 18.

The float switch 12 is arranged to close its contact when, in use, water level in the bilge rises above a predetermined level. Closing of the contacts of the floats switch 12 simultaneously causes energisation ofthe bilge pump 10, the lamp 16 and a delay circuit, described hereinafter, subject to the operation of the fuse 13.

An audible alarm 22, such as a peizo-electric horn or the like, is, in accordance with the present invention, connected substantially in parallel with the lamp 16. However, to prevent the audible alarm being triggered needlessly a delay circuit 24 is arranged to delay the energisation of the audible alarm 22 once the float switch 12 contacts have closed. The delay circuit 24 is a triggerable monostable timer circuit.

The activating circuit of Figure 1 may further comprise a switch 26. The switch 26 may be used to switch the activating circuit 9 between three modes of operation. A switch component 26a may be selected by the switch 26 to operate the activating circuit in an automatic mode. In the automatic mode the audible alarm 22 may sound if the float switch 12 contacts are closed for longer than a predetermined time, such as say 1 minute. Also, in the automatic mode the lamp 16 may become lit whenever the float switch 12 contacts are closed.

A switch component 26b may be selected by the switch 26 to operate the activating circuit 9 in a manual mode. In the manual mode the bilge pump 10 and the lamp 16may operate irrespective of the float switch 12. The delay circuit 24 may the provide an audible indication in the manual mode, when the bilge pump 10 has been operating for more than the predetermined time. The lamp 16 may become lit whenever the float switch 12 contacts are closed.

A switch component 26c may be selected by the switch 26 to operate the activating circuit 9 in a test mode. In the test mode the fuse 13 and the audible alarm 22 are both tested. If both the fuse 13 and audible alarm 22 are capable of operating a current will flow through these two components. Specifically, the current flows from the source of power 14 through the fuse 13, from switch component 26a to switch component 26c, through the audible alarm 22 to a ground potential 28 and back to the source of power 14.

It is envisaged that when the switch 26 is switched to the test mode the lamp 16 may also be tested.

It is preferred that no switch component exist to interrupt the supply of power from the source of power 14 to the remainder of the activation circuit 9 of the present invention. Thus, the activating circuit 9 of the present invention may not be accidentally disabled.

An auxiliary float switch 30 may be arranged to close its contacts, when, in use, water level at a location which may be substantially higher than the bilge, rises above a predetermined level. If the predetermined level is exceeded, the audible alarm 22 may sound immediately.

The auxiliary float switch 30 may, when its contacts are closed, communicate a current from the source of power 14, through the fuse 13, to switch component 26c and directly to the audible alarm 22.

The higher location would be at a level in the boat hull where liquid, such as bilge water, would not usually be found. Thus, if the float switch 12 malfunctions the auxiliary float switch 30 may operate in a back up capacity.

In Figure 2, one embodiment of a delay circuit 24 is shown in detail.

The delay circuit 24 comprises a timer IC NE555.

The timer IC NE555 is arranged in a monostable mode of operation. The timer IC NE555 provides a time delay in supplying power to the audible alarm 22.

When power is on, i.e. when the contacts of the float switch 12 are closed, current is supplied to the delay circuit 24 via a diode D1. In this situation a capacitor C3 which may be rated at 25of, charges rapidly whilst a capacitor C2 which may be rated at 0.1 FF, charges slowly because the current must first pass through a filter pass through a resistor R2 which may be rated at 82K ohms, to reach the capacitor C2.

It follows that, during the time that capacitor C2 is charging via resistor R2, a trigger pin 2 of the timer IC NE555 is held at a low potential. For the trigger pin 2 of the timer IC NE555, a low potenetial is any positive potential less than 1/3 of a supply voltage present at a supply pin 8 of the timer IC NE555.

When power is applied to the delay circuit 24 and the trigger pin 2, of the timer IC NE555, is at the low potential, the timer IC NE555 is set. That is, an output pin 3 is set to a high potential. The output pin 3 remains high whilst the trigger pin 2 is in the low potential range below 1/3 of the supply voltage.

Also, when power is applied to the delay circuit 24 a capacitor C1 will commence to charge. To reach capacitor C1 the current must pass through a resistor R1. The combination ofthe resistor R1 and the capacitor C1 determines the amount of delay imparted by the circuit 24, with resistor R1 rated at approximately 560 K ohm and capacitor C1 rated at l00F as shown, the time delay is about 70 seconds.

Preferably, the time delay is in the range from 30 to 300 seconds, more preferably from 35 to 150 seconds, most preferably from 55 to 85 seconds.

The timing IC NE555 monitors the voltage across the capacitor C1, as the capacitor C1 charges and compares the voltage with the supply voltage. When the voltage across the capacitor C1 reaches 2/3 of the supply voltage, the alarm 22 is turned on via the output pin 3 and a discharge pin 7 removes the charge stored in capacitor C3. As long as current continues to be supplied to the delay circuit 24 the audible alarm 22 may sound.

The output pin 3 of the timer IC NE555 may be connected to the alarm 22 by a resistor R3 which may be rated at 1 K ohm and a transistor T1.

The resistor R3 and the transistor T1 may provide a power output, to the audible alarm 22, that is greater than the power provided by the output pin 3.

Thus, a louder audible alarm 22 may be used than if the output pin 3 controlled the audible alarm 22 directly.

When the water level is reduced by the operation of the bilge pump 10, the contacts of the float switch 12 may become disconnected, positive supply is then disconnected and positive current supply is removed from the diode D1. In cases where the float switch 12 contacts are operating frequently it is important to ensure that all the electrical charge stored in the timing capacitor C1 is removed each time the float switch 12 contacts open. Otherwise, due to frequent operation of the float switch 12 contacts, electrical charge could build up in capacitor C1 and erroneously set the audible alarm 22 operating.

Means is provided to remove the charge stored in capacitor C1, if the audible alarm 22 has not begun to sound. The means comprises the charged capacitor C3, which commences to discharge the circuit immediately positive current supply is removed from the diode Do. as capacitor C3 discharges, capacitor C1 will continue to charge up. When the voltage across the capacitor C1 is 2/3 of the decreasing viltage supplied by capacitor C3 the timing IC NE555 is triggered on, output pin 3 drives the transistor TI on and the audible alarm may operate momemtarily.

Simultaneously, the discharge pin 7 removes the electrical charge stored in capacitor C1. Therefore the delay circuit 24 is reset to its original condition.

The circuit 24 is connected to the same lead as the bilge pump 10 and the lamp 16. Thus, the capacitor C3 could discharge via the pump 10 and lamp 16 but the diode D1 prevents this happening. Also, if by any chance the power supply leads were reversed during installation, the presence of diode D1 would protect the circuit 24.

The capacitor C3 prevents the circuit triggering immediately in the power on situation and supplies power to the circuit in the power off situation long enough forthe timing IC NE555 to be resetto its original condition. The value of C3 has to be high enough forthere to be enough residual energy stored to ensure that the circuit is reset reliably every time power is removed from the circuit but low enough to prevent the timing IC NE555 from false triggering evey time the power is supplied to the circuit.

In the absence of the capacitor C3 it has been found that the float switch 12 can false trigger the alarm 22 immediately in the power on situation. A capacitor C3 rated lower than 25F remedies this problem but in the power off situation where the pump had been operating for only a short time, a lower value capacitor has insufficient residual energuy to reset the timing IC NE555 to itsorignal condition. It was found that the compromise value of 251of enabled the capacitor C3 to fulfil both functions satisfactorily. The values ofthe resistor capacitor network R1 - C1 can be varied to give different time delays as required.A value of 70 seconds is generally satisfactory, since a bilge pump may usually reduce the bilge water to an acceptable level within about 15 to 10 seconds.

The resistor capacitor network R2 - C2 is designed to hold the pin 2 low in the power on situation to set the timing IC NE555. It is found that this combination overcomes problems which might otherwise be encountered with erratic starting of the circuit. The selected values ensure that the timing IC NE555 was set reliably with operation of the float switch 12.

A capacitor C4which may be rated at 0.01 of, is connected to a control voltage pin 5 to provide an A.C. earth so as to reduce external interference with operation of the circuit. Thus, a noise voltage that may be produced at control voltage pin 5, by external interference, may be substantially suppressed by capacitor C4.

The circuit described is designed for 12 volt operation only. Many boats have 24 volt electric systems which may damage the 12 volt circuit described. To operate the 12 volt cicruit, described herein, a 12 volt series regulator (not shown) may be used to reduce the 24 volts, supplied by the source of the power, to 12 volts required by the 12 volt circuit.

Modifications and variations such as would be apparent to a skilled addressee are deemed within the scope of the present invention. For example, any othertriggerable monostable timer could be used in place of the delay circuit 24, provided the triggerable monostable timer could provide an output and a delay similar to that of delay circuit 24. Also, the alarm means could comprise either an audible and/or a visual alarm.

Claims

1. An automatic bilge pump having an automatic means for energising and de-energising the pump in response to sensed water level characterised in that it comprises an alarm means arranged to give a warning when the bilge pump has been continuously operating for more than a predetermined period.

2. A pump apparatus, according to claim 1, characterised in that alarm means is an audible alarm arranged to sound an audible warning.

3. A pump apparatus according to claim 1 or 2 characterised in that float means is provided for selectively connecting the bilge pump to a source of power in dependence of the level of water in a bilge.

4. A pump apparatus according to claim 3, characterised in that there is further provided a triggerable monostable timer circuit arranged to be connected to the source of power when the float means is closed and to activate the audible alarm if the float means remains closed for more than a predetermined period.

5. A pump apparatus according to claim 4, characterised in that the triggerable monostable timer circuit includes a first RC network rated at a relatively high value, a second RC network rated at a relatively low value, an integrated circuit, a connection between the first RC network and a threshold pin of the integrated circuit, a connection between the second RC network and a trigger pin of the integrated circuit, a connection between an output pin of the integrated circuit and the audible alarm means and a connection between a further pin of the integrated circuit and the source of power, the second RC network being arranged to set the integrated circuit when power is supplied to the triggerable monostable timer circuit, the first RC network being arranged to be monitored by the integrated circuit such that when the sensed voltage at the threshold pin reaches a predetermined proportion of the supply voltage of the source of power, the connection from the output pin to the audible alarm means supplies power to the audible alarm means.

6. A pump apparatus according to claim 4 or 5, characterised in that the triggerable monostable timer circuit also comprises a further capacitor of lower rating than the capacitor of the first RC network so that on disconnection of the source of power prior to energisation of the audible alarm means, the further capacitor provides power to the triggerable monostable timer circuit for a time sufficient to enable the first RC network to be reset.

7. A pump apparatus according to any one of the preceding claims, characterised in that the audible alarm means is arranged to be activated when the bilge pump has been continuously in operation for a predtermined period in the range from 30 - 300 seconds.

8. A pump apparatus according to claim 7, characterised in that the predetermined period is in the range from 35 - 100 seconds.

9. A pump apparatus according to claim 8, characterised in that the predetermined period is in the range from 55 to 85 seconds.

10. Atriggerable monostable timer circuit for use with a bilge pump characterised in that it comprises a first RC network rated at a relatively high value, a second RC network rated at a relatively low value, an integrated circuit, a connection between the first RC network and a threshold pin of the integrated circuit, a connection between the second RC network and a trigger pin of the integrated circuit, a connection between an output pin of the integrated circuit and the audible alarm means and a connection between a further pin of the integrated circuit and the source of power, the second RC network being arranged to set the integrated circuit when power is supplied to the triggerable monostable timer circuit, the first RC network being arranged to be monitored bythe integrated circuit such that when the sensed voltage at the threshold pin reaches a predetermined proportion of the supply voltage of the source of power, the connection from the output pin to the audible alarm means supplies power to the audible alarm means.

11. A triggerable monostable timer circuit according to claim 10, characterised in that it also comprises a further capacitor of lower rating than the capacitor of the first RC network so that on discrimination of the source of power prior to energisation of the audible alarm system means, the further capacitor provides power to the triggerable monostable timer circuit for a time sufficient to enable the first RC network to be reset.

12. Atriggerable monostabletimercircuit according to claim 10 or 11, characterised in that the predetermined period is in the range from 30 - 300 seconds.

13. Atriggerable monostable timer circuit according to claim 12, characterised in that the predetermined period is in the range from 35 - 150 seconds.

14. Atriggerable monostable timer circuit according to claim 13, characterised in that the predetermined period is in the range from 55 - 85 seconds.

15. Atriggerable monostabletiming circuitfora bilge pump, substantially as described herein with reference to the drawings.