GB2541194A

GB2541194A - Self priming pump system

Info

Publication number: GB2541194A
Application number: GB1514090.8A
Authority: GB
Inventors: Jenkins Oliver; John Lusher Neil; Screen Mark; Delaney Phil
Original assignee: SPP Pumps Ltd
Current assignee: SPP Pumps Ltd
Priority date: 2015-08-10
Filing date: 2015-08-10
Publication date: 2017-02-15
Also published as: WO2017025748A1; GB201514090D0

Abstract

A self priming pump system comprises a pump having a pump chamber 110, a pump drive 116 and a vacuum generator 118,120. An inlet of the vacuum generator is connected to an enclosed volume or priming chamber 16 of the pump system via a conduit or priming duct 134. The enclosed volume is coupled to the pump chamber. The conduit comprises a valve 122 for interrupting a vacuum generated by the vacuum generator. The pump drive is selectively engageable, for example by a clutch 128, with the vacuum generator for driving the vacuum generator. The vacuum generator may comprise a venturi pump 120 and a compressor 118. The valve may be a breather valve which has a selectively openable vent to the atmosphere. A fluid probe may be used for measuring a fluid level within the enclosed volume. The valve may be operable and/or the pump drive may be selectively disengageable from the vacuum generator in response to the fluid probe measuring a predetermined fluid level. A control system may be provided to control the breather valve and the engagement of the pump drive with the vacuum generator.

Description

SELF PRIMING PUMP SYSTEM

The present invention relates to pumps and pump systems, and particularly but not exclusively to self-priming pumps and pump systems.

BACKGROUND OF THE INVENTION

Pumps and pump systems have been in use for many years. It is well known that operating an impeller pump with an insufficient amount, or complete absence of its designed fluid in the pumping chamber can cause damage to the pump or result in inefficient operation.

To combat this problem, self-priming pumps were developed, in which a vacuum generator is applied to a pumping or priming chamber in order to maintain a preferable level of the pumping fluid within the pump.

Control systems have been developed, which control the operation of the vacuum generator to the priming chamber but to date none have been entirely successful and efficient at preventing the introduction of the pumping fluid into potentially undesirable locations, such as the atmosphere or the vacuum pump, whilst providing the desirable level of control over the fluid level within the pump.

It is clear, then, that improvements in self-priming pumps are necessary to alleviate issues with existing systems.

STATEMENT OF INVENTION

In a first aspect, the present invention provides a self-priming pump system comprising: a pump comprising a pump chamber, a pump drive, a vacuum generator, an inlet of the vacuum generator being connected to an enclosed volume of the pump system via a conduit, and the enclosed volume being coupled to the pump chamber, characterised in that the conduit comprises a valve for interrupting a vacuum generated by the vacuum generator, and the pump drive is selectively engageable with the vacuum generator for driving the vacuum generator.

When the pump drive causes the pump to start the pump drive can be engaged with, and therefore drive, the vacuum generator to reduce the pressure in the enclosed volume of the pump. As the enclosed volume is coupled to the inlet of the pump at least some of a liquid, which is intended to be pumped, can be drawn into the enclosed volume to prime the pump. At least a part of the enclosed volume is higher than a priming level of the pump so that the vacuum generator can suck liquid into the enclosed volume until the level in the enclosed volume meets or exceeds the priming level of the pump and thereby prime the pump. Preferably, the priming level may be higher than an upper extremity of the pump chamber. Alternatively, the priming level may be lower than an upper extremity of the pump chamber.

The conduit is preferably coupled to the enclosed volume in a top portion of the enclosed volume, for example the top half, top third, top quarter or top 10%. The conduit may be coupled to the enclosed volume at a highest point of the enclosed volume.

The pump inlet may be coupled to the enclosed volume at a lower portion of the enclosed volume, for example the lower half, lower third, lower quarter or lower 10%.

The pump chamber is a chamber of the pump into which fluid is drawn in order to be pumped. The pump chamber may be a volute, comprise a volute or be comprised within a volute. A non-return valve may be provided within the pump chamber or volute.

The self-priming pump of the present invention provides numerous advantages over existing systems. The valve provides that the vacuum applied to the enclosed volume of the pump can be interrupted without stopping the vacuum generator, thereby preventing pumping fluid from being drawn into the conduit and the vacuum generator and providing quicker control of the vacuum. Interrupting the vacuum can comprise fully or partially blocking the conduit, or opening a port to another source from which the vacuum generator can partially, fully or preferentially draw fluid.

Furthermore, the valve can also be used to prevent pumping fluid from being vented to the atmosphere, for example through the vacuum generator. This is particularly advantageous when dirty or contaminated fluid is being pumped. The valve may take the form of any known valve for preventing fluid flow, such as a spool valve, a flapper valve or a poppet. The valve should be arranged such that it can interrupt a vacuum generated by the vacuum generator in the conduit.

At this point, when the specification refers to applying a vacuum, it should be understood that ‘vacuum’ does not require a perfect vacuum, but merely a reduction below ambient pressure. As such, it will be understood that the terms vacuum generator and vacuum pump refer to any apparatus which can generate a low pressure sink (i.e. lower than ambient pressure). To this end, the term ‘suction’ can be considered as interchangeable with the term vacuum in the context of this application. For example, it may be considered that the vacuum generator generates a suction or is a suction generator.

The selective engagement of the pump drive with the vacuum generator allows that the same drive can be used to operate the pump itself and the vacuum generator. This can reduce the size and complexity of the pump system and increase efficiency. In particular, the vacuum generator can be disengaged from the pump drive when not in use to reduce the required power from the pump drive.

Both the valve and selective engagement of the pump drive could be used to interrupt the vacuum supply to the enclosed volume, but both have disadvantages in either efficiency or speed of operation. Therefore, by providing both a valve and selective disengagement with the pump drive, the vacuum applied to the internal volume can be rapidly interrupted, but the vacuum generator can also be powered down when not required.

The enclosed volume of the pump can be the main pump chamber, a separate priming chamber, the volute of the pump, or any other internal volume of the pump system in which the fluid level is indicative of the priming of the pump.

Preferably, the pump drive is selectively engageable with the vacuum generator via a clutch. The clutch may be any type of know clutch, including friction, mechanical, electromagnetic, hysteresis, viscous, or hydraulic clutches.

Also preferably, the vacuum generator comprises a venturi pump and a compressor. A venturi pump provides an advantage in that the vacuum drawn in is then expelled to the atmosphere. Therefore, any pumping fluid which is drawn into the vacuum generator is expelled rather than entering the vacuum generator itself, which can cause catastrophic failure of, for example, a traditional vane pump based vacuum generator, or at the very least reduce the effectiveness of the vacuum generator.

Furthermore, a venturi pump is a less complex arrangement with fewer moving parts and therefore the maintenance of the system is reduced. The compressor or pump used to operate the venturi pump, having no risk of being contaminated by the pumping fluid can be chosen from a greater range of available compressors to suit the application of the main pump to provide a suitable vacuum pressure from the venturi pump.

Alternatively, the vacuum generator may comprise a traditional vacuum pump, such as a vane pump, a lobe pump, piston pump or diaphragm pump. These forms of pumps do not necessarily require an additional compressor, so in some instances the system may be less complex than the equivalent venturi pump.

Preferably, the valve is a valve having a selectively openable vent to the atmosphere. Therefore, when the valve interrupts the vacuum in the conduit, the vacuum will not be predominantly acting against the valve, and rather will simply draw in air from the atmosphere to avoid excessive force upon the valve. The valve may take the form of a sliding spool valve, or a rotatable flapper valve which can selectively block the conduit or the vent open to atmosphere, or could take the form of two valves, one for blocking the conduit and one for blocking the vent to atmosphere which are each selectively operable.

Preferably, the pump system further comprises a fluid probe for measuring a fluid level within the enclosed volume. Therefore, the fluid level can be used as a metric to assess whether the pump is suitably primed. If the probe senses an adequate level of fluid within the enclosed volume, then no further priming is required, and the vacuum applied to the volume can be interrupted. Conversely, if an inadequate fluid level is measured by the pump, then a vacuum can be applied to the volume to thereby draw pumping fluid into the pump to ensure that it is adequately primed.

The fluid probe may comprise one or more of a sight measure, a float gauge, a vibratory probe, a thermal probe, an RF transmitter, an ultrasonic, laser or radar sensor, a hydrostatic probe, a load cell, a magnetic level gauge, a capacitance transmitter, a magnetostrictive level transmitter, any other suitable probe or combination thereof.

Further preferably, the pump system comprises a control system for controlling the valve, and the selective engagement of the pump drive with the vacuum generator in response to measurements from the fluid probe. Although it may be possible for this pump to be operated manually by manually engaging or disengaging the pump drive with the vacuum generator and manually operating the valve, a control system can apply a control regime to ensure that the pump is sufficiently primed at all times during operation without human intervention. The control system can actuate the valve and selective engagement of the pump drive and the vacuum generator in response to measurements from the fluid probe. In this way, the control system can be designed to maximise the efficiency of the pump system by disengaging the vacuum generator when not required, while ensuring that the pump is not caused to run in an unprimed state for longer than necessary, and that pumping fluid from the internal volume is never drawn into the vacuum generator.

Advantageously, the valve can be operable and/or the pump drive selectively disengageable from the vacuum generator in response to the fluid probe measuring a pre-determined fluid level in the internal volume. Therefore, when the pre-determined fluid level is detected, the vacuum can be interrupted in two ways, either by operating the valve, or the removal of power to the vacuum generator. This provides a failsafe in the event that either the valve or the selective disengagement fails to operate.

Furthermore, the use of both the valve and the selective disengagement of the pump drive allow that, once the pre-determined fluid level is measured, the vacuum applied to the internal volume can be rapidly interrupted by the valve operation. If the valve has a selectively operable vent to atmosphere, then the valve may allow the vacuum to draw from the atmosphere instead of the internal volume. This fast response to the measurement of the pre-determined fluid level means that the pumping fluid should not be drawn into the conduit and the vacuum generator. Furthermore, the vacuum generator can then be disengaged from the pump drive to increase the efficiency of the system. However, if the valve were not present, then the disengagement of the pump drive would not give the rapid interruption of the vacuum, because the vacuum generator may take some time to entirely cease operating even once disconnected from power from the pump drive.

The pre-determined fluid level may be a specific predetermined fluid level within the enclosed volume, or may be a range of levels bounded by an upper level and lower level. The valve may be opened and the pump drive engaged when the fluid level measured falls below the predetermined level, or the lower level. The valve may be operated and the pump drive disengaged when the fluid level is measured exceeds the pre-determined level or the upper level.

Preferably, the valve is electronically actuable. Electronic actuation is typically the fastest form of actuation, and so the valve can be operated rapidly when the vacuum to the enclosed volume must be interrupted. Preferably, the valve is solenoid operated. Alternatively, the valve may be mechanically or hydraulically operated.

Further preferably, the pump drive is a driven shaft. The pump drive is selectively engageable with the vacuum generator. The means for selective engagement includes the clutch, but may also include a linkage comprising one or more of a belt, gear, chain, or direct drive. Preferably, the pump drive rotates an impeller of the pump. A filter may be provided at an inlet from the internal volume to the conduit. In this way, in the event that pumping fluid is drawn into the conduit and further into the vacuum generator, any potentially destructive particulate matter suspended in the pumping fluid can be removed before it is vented to atmosphere or into the vacuum generator.

In a second aspect, the present invention provides a method for priming a pump system comprising: engaging a pump drive with a vacuum generator to generate a vacuum, applying the vacuum to an enclosed volume of the pump via a conduit, characterised by interrupting the vacuum applied to the pump by operating a valve for interrupting the vacuum disposed in the conduit, and interrupting the power to the vacuum generator by disengaging the pump drive from the vacuum generator.

The presently described method provides advantages as hereinbefore described in relation to the first aspect of the invention.

The method presently described may conveniently be a method for operating the apparatus of the first aspect of the invention. It should be understood that preferable and advantageous features of the apparatus and method are interchangeable.

Preferably, disengaging the pump drive from the vacuum generator comprises selectively disengaging a clutch.

Further preferably, the vacuum generator comprises a venturi pump and a compressor.

Preferably, the method further comprises measuring a fluid level within the enclosed volume. Measuring the fluid level can be performed constantly, or intermittently. Measuring the fluid level can be performed with the fluid probe as mentioned in relation to the first aspect of the invention.

Preferably, the steps of interrupting the vacuum and interrupting the power to the vacuum generator are performed in response to measuring a pre-determined fluid level within the enclosed volume. Alternatively, the predetermined level may be the upper level of the predetermined fluid level range as herein before described.

Further preferably, the step of interrupting the vacuum is performed prior to the step of interrupting the power to the vacuum generator.

Preferably, the method further comprises filtering a fluid entering the conduit from the enclosed volume.

Advantageously, the engaging and applying steps may be performed in response to measuring a fluid level below the pre-determined fluid level or the lower level of the predetermined fluid level range as herein before described.

It will be understood by the skilled person that these preferable and advantageous features may be combined with one another and that any resulting embodiments will also be embodiments of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENT A better understanding of the present invention will be obtained from the following detailed description. The description is given by way of example only and makes reference to the accompanying drawings, in which:

Figure 1 is a part cross-sectional view of a seif-priming pump system according to the present invention in an arbitrary unprimed condition; and

Figure 2 is a part cross-sectional view of a self-priming pump system according to the present invention in an arbitrary primed condition.

Figures 1 and 2 shows a self priming pump system 10 in an unprimed and primed condition respectively. The invention will now be described in relation to Figures 1 and 2.

The system 10 is designed to ensure that a centrifugal pump 12 is sufficiently primed during its operation. A centrifugal pump is primed when sufficient liquid is present within the pump to allow the pump to operate effectively in pumping the liquid.

The system 10 comprises a centrifugal pump 12. The pump 12 comprises an inlet 14, an enclosed volume or priming chamber 16, and an impeller 18 located in pump chamber 110, the pump chamber 110 in the present example being a volute 114 including a non-return valve 115.

During pumping operation when the pump 12 is primed (as shown in Figure 2), a liquid 112 enters the pump via the inlet 14, passes through the priming chamber 16 and is drawn towards the impeller 18, which is rotating at speed. The impeller 18 ejects fluid from the immediate vicinity of the impeller 18 around the volute 114 and through the non-return valve 115 to a pump outlet where the liquid is ejected (not shown). While the pump is in operation (i.e. while the pump is primed and the impeller is rotating), liquid 112 is constantly drawn in through the inlet 14, transits though the pump 12 and ejected from the outlet. The non-return valve 115 prevents backwards flow through the pump 12, and will close when a fluid is drawn backwards through the volute 114, thereby sealing off the volute 114. The non-return valve 115 is shown in a closed position in Figure 1 and in an open position in Figure 2. The skilled person will be familiar with the operation of such centrifugal pumps. It should also be understood that the invention is not limited to the centrifugal pump shown and will also be applicable to other pump types which require priming.

The priming chamber 16 is a voluminous hollow chamber within the body of the pump 12. The priming chamber 16 extends above the height of the volute 114, such that when the volute 114 is filled with liquid 112, the priming chamber 16 is only partially filled as shown in Figure 2. The priming chamber comprises an outlet 16a on its uppermost inner surface 16c, whereby fluid within the priming chamber 16 can exit. The outlet 16a is obscured by a filter block 16b, which is substantially permeable to gases, liquids, and small particulate solids but impermeable to larger solids (including large particulates suspended in fluid). Therefore, any fluid exiting the priming chamber 16 via the outlet 16a is filtered by the filter block 16b. The priming chamber 16 is coupled or connected to the volute 114, such that fluid 112 entering the pump via the inlet can flow through the priming chamber 16 in order to be pumped out of the volute 114 by the impeller 18.

The pump system 10 also comprises a pump drive or drive means 116 connected to the impeller 18 for spinning the impeller. The drive means 116 comprises an output drive shaft from an engine or motor (not shown). The drive means 116 is permanently connected to the impeller such that the impeller 18 is always driven when the engine is in operation. Alternatively, the drive means 116 can be directly connected to the impeller 18, or may be connected via a gearbox or linkage system, which may include a clutch, in order that the impeller 18 can be selectively driven independent of the operation of the engine. When the drive means 116 is driving the impeller 18, the impeller spins within the volute 114 and, if the pump is sufficiently primed, then the pump operates as mentioned above and liquid is drawn in the inlet 14 and expelled from the outlet. As the impeller 18 spins at all times when the engine is in operation, the impeller 18 may be rotating in air when the pump is unprimed. Therefore, the impeller 18 is designed such that it can rotate in air without damage to the system.

The pump system also comprises a vacuum generator. In the illustrated embodiment, the vacuum generator comprises a compressor 118 and a venturi vacuum pump 120. The compressor 118 intakes ambient air and compresses the air to provide a high pressure air output into a duct 132.

The compressor 118 is powered by the drive means 116 of the pump 12 via clutch 128, in this case a magnetic clutch, which selectively couples the compressor 118 to the pump drive means 116. Using this clutch 128, the drive means is selectively engageable with the compressor 118 and vacuum pump 120. A belt drive 130 is connected to the drive means 116, which rotates an input rotor 128a of the clutch 128. An output rotor 128b of the clutch is connected to the compressor 118. Therefore, when the clutch 128 is engaged, the compressor 118 is driven by the drive means 116 via the clutch 128. When the clutch 128 is disengaged, the compressor is 118 is not driven, regardless of whether the drive means 116 is in operation.

The duct 132 is connected to the inlet 120a of the venturi pump 120. The venturi pump 120 comprises a tapered profile 120a,b,c. The profile comprises a narrowing tapered inlet 120a, a neck 120b, and an increasing tapered outlet 120c. High-pressure air from the compressor 118 enters the inlet 120a via the duct 132 and accelerates through the inlet 120a while its pressure decreases according to Bernoulli’s principle. The high velocity air then passes though the neck 120b, and into the outlet 120c, where the air is decelerated and its pressure increases, again following Bernoulli’s principle. Therefore, the internal pressure in the venturi pump 120 is at a minimum at the neck 120b. A vacuum inlet 120d is provided at the neck 120b, such that the inlet 120d provides a low-pressure sink.

The pump system 10 further comprises a conduit or priming duct 134. The priming duct 134 is connected at its inlet 136 to an outlet 16a of the priming chamber 16. The outlet 16a is located at the highest point of the priming chamber 16. The priming duct 134 is connected at its outlet 138 to the vacuum inlet 120d of the venturi pump 120. Therefore, when the venturi pump 120 is in operation, a vacuum can be applied to the priming chamber 16 via the priming duct 134.

The priming duct 134 further comprises a valve 122 which can interrupt the vacuum. In this embodiment, the valve 122 is a valve with a selectively openable vent to atmosphere, also known as a breather valve. The breather valve 122 is arranged in series in the duct 134. The breather valve 122 comprises an internal passage 122a, an atmospheric branch 122b, and a valve 122c, which is typically a spool valve. The internal passage 122a is connected to the inlet 136 of the duct, and is therefore in fluid communication with the priming chamber 16. The atmospheric branch 122c is connected to the open atmosphere, and is thus in fluid communication with the atmosphere.

The spool valve 122c is arranged such that it can selectively block and inhibit flow through either the internal passage 122a or the branch 122b, but not both simultaneously. Therefore, when a vacuum is applied to the priming duct 134 via vacuum inlet 120d, the spool valve 122c can selectively apply the vacuum to the internal passage 122a (and thus air will be drawn into the duct 134 from the priming chamber 16) or to the atmospheric branch 122b (and thus air will be drawn into the duct 134 from the atmosphere).

In Figurel, it can be seen that the spool valve 122c is blocking the atmospheric branch 122c and leaving the internal passage 122a open. In this position, the breather valve will be referred to as ‘closed’. When the internal passage 122a is blocked and the atmospheric valve 122b is open (see Figure 2), the breather valve 122 will be referred to as ‘open’.

The system 10 further comprises a fluid sensor probe 126 and a control box 124. The fluid sensor probe 126 is an elongate probe which protrudes vertically into the priming chamber 16 from the upper inner surface 16c of the priming chamber. The probe 126 comprises two probe portions, an upper probe portion 126a, and a lower probe portion 126b. Alternatively, the upper and lower probe portions may be provided as two separate probes having different lengths.

The probe sections 126a,b are liquid contact sensors, in particular capacitance based sensors, such that they can detect both conducting and non-conducting fluids. Therefore, the sections provide an indication when liquid 112 is in contact with their outer surface. The skilled person will be aware of many different types of suitable sensors, such as thermal or vibratory probes.

Lower probe portion 126b is connected to and arranged below the lower extremity 126d of the upper probe portion 126a and therefore protrudes into the priming chamber 16 by a greater distance than the upper probe portion 126a. The probe 126 is arranged within the priming chamber such that the lower extremity 126 of the probe is arranged at a predetermined height in the chamber 16. The predetermined height is the lowest height at which the surface of the liquid 112 will be when the pump is primed. Therefore, when sufficient liquid 112 is present within the chamber for the pump to be primed, at least the extremity 126c of the probe 126 should be in contact with the liquid 112 (as shown in Figure 2). When the pump is not primed, the liquid 112 will not be in contact with the lower probe section 126b (as shown in Figure 1).

The lower extremity 126d of the upper portion 126a of the probe is located at a second predetermined height in the priming chamber 16. The second predetermined height is the height at which the pump is over primed. If the surface of the liquid 112 is above this second predetermined height, then there is a risk that the liquid will be drawn into the outlet 16a of the priming chamber 16. Therefore, once the pump is over primed, the extremity 126d of the upper section 126a should be in contact with the liquid 112 (not shown).

The control box 124 comprises a control system. The control box 124 controls the breather valve 122, the fluid sensor probe 126, and the clutch 128 via lines 124a, 124b, and 124c respectively, such that the control box 124 can send and receive signals to and from these three components. The control box 124 may be electronic or mechanical, but in this embodiment is electronic. The control box 124 is in electronic communication with a solenoid (not shown) associated with the breather valve 122 which actuates the breather valve 122.

The operation of the self priming pump system will now be described in relation to the aforementioned components.

Typically, the pump system will be in an unprimed condition at start-up. For example, the pump system may have been transported to a required location, where an inlet hose (not shown) is attached to the inlet 14, and the inlet hose is submerged in a liquid 112 source that requires pumping. Once the inlet hose is fully submerged in the liquid 112, a seal is formed, such that liquid can be drawn up the inlet hose into the pump 12 using low pressure within the priming chamber 16.

The operation of the pump system 10 will be described starting from Figure 1, which shows the pump system in an unprimed condition, whereby an inlet hose is fully submerged in the liquid 112 as mentioned in the previous paragraph.

Drive means 116 is driven such that the impeller 18 is rotating within the volute 114. The probe 126 senses that no liquid 112 is contact with either of the upper or lower sections 126a,b of the probe, meaning that the pump is not primed (as can be seen in Figure 1). The control box 124 receives from the probe 126 an indication that no liquid 112 is sensed. The control regime of the control box, sensing that the pump is not primed, transmits a signal via line 124c to engage the clutch 128 such that the compressor 118 is powered up, and also transmits a signal to the breather valve 112 to move the spool valve 122c such that the internal passage 122a is open, and the atmospheric branch 122b is blocked. The compressor 118 supplies air to the inlet 120a of the venturi pump 120.

Therefore, the low pressure sink from the venturi pump inlet 120d begins to draw air in from the priming chamber 16 via the duct 134 and expel it to atmosphere. This negative pressure differential causes the non-return valve 115 to close, such that air can only be drawn into the duct 134 from the pump inlet 14. As the inlet hose is sealed by liquid 112, the liquid 112 is drawn up the inlet hose, through the inlet 14 into the priming chamber 16. As more air is drawn out of the priming chamber 16, the height of liquid 112 rises until the surface liquid 114 reaches the height of the lower portion 126b of the probe 126, as shown in Figure 2. At this point, the pump 12 is sufficiently primed to operate and will be drawing liquid 112 into the pump 12 by its own operation and expelling it via the volute 114, which will re-open the non-return valve 115. In the present embodiment, the impeller 18 is spinning throughout the priming operation, but in an alternative embodiment, the drive means 116 may be selectively engageable with the impeller 18 such that the impeller is only spun up once the pump is fully primed.

In the present embodiment, once the pump is primed (as shown in Figure 2), the probe 126 senses the presence of liquid 112 in contact with the lower portion 126b, and this information is transmitted to the control box 124. As the pump 12 is now sufficiently primed, the control box 124 transmits a signal to the breather valve 122 to move the spool valve 122c such that the atmospheric branch is open and the internal passage 122a is blocked. Therefore, the low pressure applied to the priming chamber 16 via the duct 134 is immediately terminated and air is instead drawn into the venturi pump inlet 120d from the atmosphere.

Following the operation of the breather valve 122, if the probe 126 continues to sense that the liquid 112 is in contact with the lower section 126b for a predetermined period of time (indicating that the pump 12 is operating sufficiently to prime itself), then the control box 124 then sends a signal to the clutch 128 to disengage. The clutch 128 then disengages, thereby removing power from the compressor 118 and interrupting the operation of the venturi pump 120. The pump 12, having reached a steady state of priming, can then pump fluid as required.

The control box 124 will not command the clutch 128 to disengage until it has sensed that liquid 112 has been in contact with the probe 126 continuously for the predetermined period of time. If the probe, following opening of the breather valve 122, senses that liquid 112 has not been in contact with the probe 126 for a predetermined period of time (and therefore that the pump is no longer primed), then the breather valve 122 will be closed, such that the low pressure is reapplied to the priming chamber 16 to re-prime the pump 12.

If, following disengagement of the clutch 128 and during ongoing the pumping operation, the probe 126 senses that the liquid 112 in the priming chamber 16 is no longer in contact with the probe (and therefore that the pump is no longer fully primed), then this information is transmitted to the control box 124. Control box 124 then transmits signals to both the breather valve 122 to thereby open the internal passage 122a, and to the clutch 128 to thereby power up the venturi pump 120. The low pressure is then reapplied to the priming chamber 16 until the probe 126 detects that the pump is sufficiently primed. Once a steady level of priming has been re-achieved, then the above procedure of opening the breather valve 122 and disengaging the clutch 128.

In an alternative control regime, the priming operation may be as follows. The probe 126 detects that the liquid 112 is not in contact with the lower probe portion 126b, then the clutch 128 is engaged and the breather valve is closed to thereby prime the pump 12. However, in contrast to the previous method, the breather valve is not re-opened until liquid 112 is detected by the upper portion 126a. Therefore, the pump is ‘over1 primed such that the level is above that which is required, but the priming tank 16 is not so full that liquid 112 is drawn into the outlet 16a. The remainder of the operation of the priming operation is performed as described previously.

It will be understood that the pump system described herein is for exemplary purposes only, and that there are many types of pump system compatible with the present invention.

The present invention is not limited to the specific embodiments described herein. Alternative arrangements and suitable materials will be apparent to a reader skilled in the art.

Claims

1. A self priming pump system comprising: a pump comprising a pump chamber; a pump drive; a vacuum generator, an inlet of the vacuum generator being connected to an enclosed volume of the pump system via a conduit, and the enclosed volume being coupled to the pump chamber; characterised in that the conduit comprises a valve for interrupting a vacuum generated by the vacuum generator; and the pump drive is selectively engageable with the vacuum generator for driving the vacuum generator.

2. A self priming pump system as claimed in claim 1, wherein the pump drive is selectively engageable with the vacuum generator via a clutch.

3. A self priming pump system as claimed in any one of claims 1 or 2, wherein the vacuum generator comprises a venturi pump and a compressor.

4. A self priming pump as claimed in any one of the preceding claims, wherein the valve is a valve having a selectively openable vent to the atmosphere.

5. A self priming pump system as claimed in any one of the preceding claims, wherein the pump system further comprises a fluid probe for measuring a fluid level within the enclosed volume.

6. A self priming pump system as claimed in any one of the preceding claims, wherein the pump system further comprises a control system for controlling the breather valve, and the selective engagement of the pump drive with the vacuum generator in response to measurements from the fluid probe.

7. A self priming pump system as claimed in any one of claims 5 or 6, wherein the breather valve is openable in response to the fluid probe measuring a pre-determined fluid level in the internal volume.

8. A self priming pump system as claimed in any one of claims 5 to 7, wherein the pump drive is selectively disengageable from the vacuum generator in response to the fluid probe measuring a pre-determined fluid level in the internal volume.

9. A self priming pump system as claimed in any one of the preceding claims, wherein the breather valve is electronically actuable (preferably solenoid).

10. A self priming pump system as claimed in any one of the preceding claims, wherein the pump drive is a driven shaft.

11. A method for priming a pump system comprising: engaging a pump drive with a vacuum generator to generate a vacuum, applying the vacuum to an enclosed volume of the pump via a conduit, characterised by interrupting the vacuum applied to the pump by operating a valve disposed in the conduit, and interrupting the power to the vacuum generator by disengaging the pump drive from the vacuum generator.

12. A method for priming a pump system as claimed in claim 11, wherein disengaging the pump drive from the vacuum generator comprises selectively disengaging a clutch.

13. A method for priming a pump system as claimed in any one of claims 11 or 12, wherein the vacuum generator comprises a venturi pump and a compressor.

14. A method for priming a pump system as claimed in any one of claims 11 or 13, wherein the method further comprises measuring a fluid level within the enclosed volume.

15. A method for priming a pump system as claimed in claim 14, wherein the steps of interrupting the vacuum and interrupting the power to the vacuum generator are performed in response to measuring a pre-determined fluid level within the enclosed volume.

16. A method for priming a pump system as claimed in any one of claims 11 to 15, wherein the step of interrupting the vacuum is performed prior to the step of interrupting the power to the vacuum generator.

17. A method for priming a pump system as claimed in any one of claims 11 to 16, further comprising filtering a fluid entering the conduit from the enclosed volume.

18. A method for priming a pump system as claimed in any one of claims 14 to 17, wherein the engaging and applying steps are performed in response to measuring a fluid level below the pre-determined fluid level.

19. A self priming pump system substantially as hereinbefore described with reference to the accompanying drawings.

20. A method for priming a pump system substantially as hereinbefore described with reference to the accompanying drawings.