Technical Field

The invention relates to pump apparatus and to the operation and control of the pump apparatus, and particularly but not exclusively to a pump control device and an air operated double diaphragm pump.

Background

Single diaphragm belt operated pumps can work at high pressures although they can be inefficient, large and can have difficulties conforming to current health and safety standards. If gas is present in the pumping media (for example as may occur with a leak or an insufficient seal) the pump can suffer vapour lock and can cease to operate.

Air pumps are well known but are not commonly available for high pressure applications. Air pumps can have a single or double diaphragm design but their operation means the pump has air consumption higher than necessary for performing the pumping task alone. This is clearly inefficient and represents wasted energy.

Some dosing -type pumps have been investigated as an alternative for high pressure operation but these are expensive, prone to issues with vapour lock and are not energy efficient.

It is desirable to produce a pump working at a low operating pressure and in an efficient manner and there is thus a need for an improved pump for high pressure operation.

Definitions

l A diaphragm pump is defined as a positive displacement pump, most commonly a fluid pump. The diaphragm refers to a flexible sheet portion that moves in a reciprocating manner to provide pump action. Pumping is provided by the combination of the reciprocating action of one or more diaphragms (made for example of rubber, thermoplastic or teflon) and suitable valves either side of the diaphragm to pump a fluid.

In the pump described here the one (or each) diaphragm is sealed with one side in the fluid to be pumped, and the other in air or hydraulic fluid. The diaphragm is flexed, causing the volume of the pump chamber to increase and decrease. A pair of non-return valves can be present to prevent and check any reverse flow of the fluid. In another arrangement the movement of the diaphragm can be effected by electromechanical means. Other diaphragm pumps can use unsealed diaphragms, which are flexed and therefore cause the volume to change.

When the volume of the chamber defined by the flexible portion (diaphragm) is increased (the diaphragm moving up or outwards), the pressure decreases, and fluid is drawn into the chamber through a valve. When the chamber pressure later increases from decreased volume (when the diaphragm moving down or inwards), the fluid previously drawn in is forced out. Finally, the diaphragm again moves up (or out) and draws fluid into the chamber, completing the pump cycle.

Summary of the invention

In accordance with the present invention, from a first aspect, there is provided a pump control device for an air controlled double diaphragm pump, the pump comprising a pump housing, a pumping chamber within the housing, at least two diaphragms and a diaphragm coupling shaft, the diaphragms arranged within the chamber and operatively connected to the diaphragm coupling shaft, the control device comprising at least one ring magnet mounted within the diaphragm coupling shaft and a sensor apparatus, the sensor apparatus located within the pump housing and being arranged to detect the proximity of the at least one ring magnet and the diaphragm coupling shaft to the sensor apparatus, further comprising a programmable controller arranged to receive and respond to information from the sensor apparatus so as to control the end stroke and reciprocation of the coupling shaft.

The pump control device operates in a double diaphragm pump using sensor apparatus to detect the position and proximity of a magnet mounted within the diaphragm coupling shaft. A programmable controller in the form of a Programmable Circuit Board (PCB) is responsive to the sensor apparatus and controls the direction of the diaphragms to switch them from one direction to the other and thus shuttle the diaphragm and cause the pump to operate. One advantage of this arrangement is that the method of sensing is indirect and is not pressure dependent. Air pressure is not required to switch the diaphragm from one position to another. Typically in the existing Air Operated Double Diaphragm (AODD) pumps the shuttling or switching of the diaphragms is switched with pressure applied to the back of the diaphragms to switch an integral air control valve and requires pressures of between 1 and 2 bar. Such high pressures are required to avoid pump stalling but are difficult to maintain and mean that the system is not energy efficient. In these existing AODD pumps it means that the air consumption of the pump is higher than necessary to perform the pumping task alone. This is clearly undesirable and results in unnecessary cost and energy usage. The pressure is derived from the motive pressure delivered to the back of the diaphragms, and the volume of air is substantial in size, for example in a 2" diameter pump from Tapflo the volume is 2.3 litres, therefore if the application calls for the pump to run at say 0.5 bar, but has to peak at 1 .5 bar to switch the air control valve, 2.3 normal litres of compressed air is wasted every stoke. As the pump can stroke 3 times a second this therefore constitutes a large amount of wasted energy. The issue is common to all pumps with a single air supply and the improved control device addresses the aforementioned disadvantages. In addition the dwell at the end of a pump stroke gives the pump a pulsed output which can be undesirable.

In an embodiment the control device comprises a pair of opposing ring magnets mounted within the diaphragm coupling shaft, and located in an arrangement having south terminals orientated facing the centre portion of the diaphragm coupling shaft. The south terminals facing the centre portion of the shaft can be aligned with detector apparatus within the pump housing and sensitive to the south terminals. An alternative detection with one or more magnets and north terminals is also envisaged, the terminal to be detected is preferably arranged innermost such that the detection of the terminal to be detected allows full shuttle and travel of the diaphragm coupling shaft and thus fullest extent of the diaphragm.

In the arrangement the pair of ring magnets are detected by the PCB and two south sensitive proximity switches are used. This provides some redundancy in the system and provides additional input for the sensor device.

In the embodiment described the sensor apparatus comprises at least one proximity sensor. The pump control of an embodiment could comprise a single proximity sensitive sensor, this would reduce the part count and the cost of the system. But may require a timing device for switching purposes. In a preferred embodiment however, the sensor apparatus comprises 2 south pole sensitive proximity sensors. This provides a resilient sensor for detecting and sensing the presence and passing movement of the ring magnets mounted within the diaphragm coupling shaft.

The controller in a preferred embodiment comprises a programmable circuit board (PCB) and programmable integrated controller (PIC) arranged to switch a solenoid operated air valve so as to control the direction of the diaphragms and coupling shaft. The controller is responsive to the sensor apparatus and thus the position of the diaphragm coupling shaft and the diaphragms connected to the shaft. The sensing is such that the position of the magnets in relation to the south pole sensitive proximity sensors is fed back to the PIC that in turns controls an external solenoid operated air valve. The solenoid valve in an embodiment is used directly to control airflow to the diaphragms so as to control the direction of the diaphragms in an embodiment. There may be more than one solenoid valve.

In an embodiment a solenoid valve is arranged to pilot an air valve, the pilot air valve is provided to control the direction of the diaphragms and coupling shaft. The sensing of the diaphragm position and the activation of the air valve is not pressure dependent as it is controlled by detection of a magnetic field. No air from the pump itself is used or tapped and this means that there is no spike in the air pressure within the pump at the end of a stroke of the diaphragm coupling shaft. This means smoother operation and less wear and tear on the equipment due to pump activation.

Preferably the controller is mounted within the pump housing and preferably the diaphragms are mounted directly to the pump body. A compact system is important for location within other equipment.

In an embodiment a single seal is provided on the coupling shaft. There are no tapings required or air take offs from the pump cylinder housing so a single seal is sufficient. A single shaft seal is advantageous for reducing friction and allowing the system to run and operate at low pressures in both hydraulic and pneumatic applications. The apparatus can also be used in high pressure applications up to 40bar. The minimum operating pressure has been found in experiment to be 0.1 bar, and operation in the working example has been found to be of almost pulse free flow throughout the operating pressure range and the air consumption of the system is greatly reduced over a conventional AODD pump proving an equivalent flow.

Preferably the movement of the shaft extends for up to 6 cm from the diaphragms. This allows for full movement of the diaphragm coupling shaft either side of the central location or rest position of the diaphragms and provides sufficient pump volume to be generated from the movement of the shaft and diaphragms. In accordance with the present invention, as seen from a second aspect there is provided a pump comprising a pumping chamber, a double diaphragm and a pump control device as set out above. In an embodiment the pump is an Air Operated Double Diaphragm Pump.

In a preferred embodiment the operation is driven in the absence of compressed air and from one of the range; electrically, hydraulically. This is an efficient driving method.

In accordance with the present invention, as seen from a third aspect, there is provided a method of operating and controlling an air double diaphragm pump comprising the steps of;

(i) receiving information on the starting position of a coupling shaft and diaphragm from a south pole magnet;

(ii) monitoring movement of the shaft and a diaphragm in a first direction on approach to a stationary proximity sensor device responsive to a magnetic field;

(iv) logging information on the furthest extent in a first direction of the coupling shaft;

(v) activating a solenoid valve to switch direction of the diaphragm from a first direction to a second direction;

(vi) monitoring movement of the shaft and a diaphragm in the second direction on approach to a stationary proximity sensor device responsive to a magnetic field;

(vii) logging information on the furthest extent in the second direction of the coupling shaft; and

(viii) de-activating a solenoid valve to switch direction of the diaphragm from the second direction to the first direction.

In an embodiment the operation is achieved with activation of one solenoid valve changing states from On' to Off. There is also envisaged that two solenoid valves could be used, (here an initial stage would be with one solenoid valve Off and one On') and in use the states of the first and second valves would be reversed. Here methods of controlling and changing the direction of the diaphragms and coupling shaft are intended to be covered in this application.

The pump control device can further comprise output means, which may comprise a display screen and/or a printer.

Brief description of the drawings

Figure 1 is a vertical cross sectional view through a diaphragm pump with a pump control device in accordance with an embodiment of the present invention as seen from the first aspect;

Figure 2 is a vertical cross sectional view of a portion of the diaphragm pump of Figure 1 ;

Figure 3 is a side view of the controller and PCB apparatus in accordance with an embodiment of the present invention as seen from a first aspect; and

Figure 4 is a flow diagram of a method for operating and controlling an AODD pump with a control device according to the present invention.

Detailed description

With reference to Figure 1 of the drawings, there is illustrated an air operated diaphragm pump 100 within an existing outer housing 1 .

The pump comprises a cylindrical housing 1 , a pumping chamber 2, a pump region 3 arranged to accommodate a volume of air, a diaphragm coupling shaft 4, and at least two diaphragms 5, 6. The diaphragms 5, 6, are operatively connected and mounted to the diaphragm coupling shaft 4 and are able to move under the action of the diaphragm coupling shaft 4. In the illustrated embodiment the diaphragms 5, 6 are mounted directly to the pump housing body. The shape of the diaphragms 5, 6, at rest, is such that they are parallel to each other. Input IN and output OUT ports are provided in the pump apparatus. The control device portion of the pump comprises ring magnets 10 and 12. The ring magnets in the illustrated embodiment are a pair of opposing ring magnets 10, 12 orientated with their south terminals facing the centre or innermost portion of the diaphragm coupling shaft 4. The ring magnets 10, 12 are located and mounted within the diaphragm coupling shaft 4 as illustrated in Figures 1 and 2. The sensor apparatus portion 14 of the control device is located in recess 16 within the pump housing 1 . The recess 16 accommodates the cables and wiring for the apparatus. The apparatus is connected to a power supply, solenoid switching valve, control and output devices (not shown). The sensor apparatus 14 comprises 2 south pole terminal sensitive proximity detectors. The control device further comprises is a controller (PCB) 18 and a Programmable Intergrated Controller (PIC) 20 operable to switch direction and operation of the diaphragm coupling shaft 4 and the diaphragms 5, 6.

Construction details and features such as wear rings 30 are provided around the diaphragm coupling shaft 4 for smooth operation and movement. A single seal 40 Is provided between the inner pump housing 1 and the diaphragm coupling shaft 4.

In use the sensor apparatus 14 housed and secured within the recess 16 picks up on and senses the position of the ring magnets. The scheme of operation is set out with reference to Figure 4 and steps 101 to 108. As ring magnets 10 and the 12 mounted on diaphragm shaft 4 move in a direction back and to the right hand side of the view shown in Figures 1 and 2 they in turn pass the first proximity sensor and the position of the shaft 4 is noted. Then as it moves and shuttles further back and to the right the second proximity sensor detects the ring magnets and acts by the functionality of the programmable controller to activate a solenoid valve to change the direction of movement of the shaft 4. hus the end stroke of the coupling shaft 4 is controlled and changed from a backwards direction to a forwards and to the left the side of the view shown in Figures 1 and 2. Thus the diaphragms 5 and 6 are flexed and moved with the diaphragm coupling shaft 4 in a reciprocating manner and the operation steps of Figure 4 are repeated. The use of the PCB and PIC enables a variety of functionality to be implemented and to be varied with the requirements of the system. In the illustrated embodiment the portion 14 features the back to back mounting of two south sensitive proximity switches as available commercially. The sensor switches act as set out above to detect the proximity of two opposing south facing ring magnets 10, 12 mounted within the diaphragm coupling shaft 4. The extent of the magnetic field in the example provided is around 25 to 30 mm, so the sensors are located within this range. The position of the magnets with in the pump and in relation to the sensors 14 is fed back to the PIC and the control program and firmware. The PIC in turn acts to operate an external solenoid operated air valve and to control the direction of the diaphragms. The PCB and PIC are held within a pocket and recess area within the pump housing 1 . Cables lead from the PCB to power supply and to the solenoid valve. The cable length can be up to 3 m. The dimensions of the PCB of the embodiment are 25 mm x 16 mm. the width of the proximity sensor region is 4 mm. The extent of the shuttle distance of the diaphragm coupling shaft is around 6cm.

As set out above the benefits of the arrangement are that the switching and direction change is not pressure dependent, once the diaphragms 5, 6 and the diaphragm coupling shaft 4 has moved sufficiently for the ring magnet 10 or 12 to be so-called visible and detectable to the proximity sensor 14 it acts to change its state and send it in the opposite direction to the existing direction of travel. There is no spike in pressure at the end of a stroke of the diaphragm coupling shaft 4. The method of direction change is indirect and remote and does not require pressure tapings from within the pump chamber 2 or structural changes to the pump housing 1 . A single seal is required and this in turn reduces movement pressure and friction within the system. The pump can run and operate at very low pressure, compared with existing pump systems, around 0.1 bar, this represents a very low starting pressure for the system. In addition the pump provides operation in a pulse free manner and thus without the need for a pulse damping device or retro fitted device to reduce pump discharge.

A single seal is compatible with a hydraulic design and use with a hydraulic power supply pack (not shown). In a tested example of the embodiment described above the pump has operated at pressures of up to 40 bar, flows up to 25 litres a minute and with a motor power rating as low as 90 watts.

The external air control valve described in the example above is a commercially available externally piloted 5/2 solenoid/spring valve. The valve in this embodiment has control pressure and pump pressure connections, this means that the valve can be piloted at a higher pressure than the pressure of the pump. The higher pressure circuit is minimised to requiring just a few millilitres (ml_). The high pressure circuit does not therefore add significantly to the pressure required by the system and reduces the energy required by the system to the minimum, with overall operating pressures of 0.1 to 40 bar. Positive suction pressures of up to 18.5 bar can be withstood by the system.

In the tested embodiment the output to the solenoid valve mentioned above is modulated to reduce further the energy consumption. With modulation details of 50% duty after an initial spike it was found electrical power consumption reduced by 75%. A totally electric diaphragm pump can thus be achieved.

The PCB and PIC firmware described has an output that can be utilised for further functionality, for example by a further control such as an external controller with additional components, for example a display or output screen.

Various modifications may be made to the described embodiments without departing from the scope of the present invention. There may be a different number of components or magnetic features or sensor apparatus, for example 1 sensor only. The pump and control may comprise any shape or orientation. There may be a plurality of sensors and sensor components valve and switching components. The location of the control device portion and the ring magnets could be in a different position to that shown and described above. The positions of the sensors could be altered to take account of different magnetic field strength of different ring magnet combinations. Other types of magnet or other types of sensing system could be used. A greater or lesser distant of travel of diaphragm shaft could be envisaged. Alternative types or combinations of solenoid valves may be used. A totally hydraulic system without compressed air is also envisaged.

The following paragraphs may assist in the understanding of the invention;

We were approached to develop a specialist high pressure double diaphragm pump to replace their existing single diaphragm motor driven, belt operated pump that was not working as they required. It was antiquated, large, unable to cope with gas in the media being pumped (normal operation) suffering vapour lock, inefficient (>1 Hp motor and of single diaphragm design), and had significant health and safety issues. On researching the market there appeared to be no other pump available for their duty.

We had also identified that there was a significant energy issue with existing air operated double diaphragm (AODD) pump technology. The majority of AODD pumps on the market use the pressure applied to the back of the diaphragms to switch the integral air control valve. This in turn means the air consumption of the pump is higher than necessary to perform the pumping task alone. The pressure has to increase at the end of stroke to give sufficient to switch the air valve, in most cases would be in the region of 1 -2 bar to switch properly, and reduce the risk of the pump stalling. As this pressure is derived from the motive pressure delivered to the back of the diaphragms, the chamber has to be charged to 1 -2 bar before the pump will switch. This volume is substantial in size, for example in a 2" Tapflo pump is 2.3 litres, therefore if the application calls for the pump to run at say 0.5 bar, but has to peak at 1 .5 bar to switch the air control valve, 2.3 normal litres of compressed air is wasted every stoke. As the pump can stroke 3 times a second constitutes a massive amount of wasted energy.

This dwell at the end of stroke also gives the pump a pulsed output as no flow occurs whilst the pressure builds to switch the valve.

We embarked on the LEAP project to design a product that would solve both of the above opportunities.

A new approach to the control of an Air Operated Double Diaphragm (AODD) Pump using proximity sensors to detect the position of the diaphragms by detecting opposing ring magnets mounted into the diaphragm coupling shaft. This enabled the use of a single shaft seal.

By utilising this control and seal reduces the minimum operating pressure to 0.1 bar, with practically pulse free flow throughout the pressure range.

By reducing the air pressure to the pump and removing the pulse, the compressed air consumption is greatly reduced against a conventional AODD pump with equivalent flow.

The single seal method allows for hydraulic operation, thus giving an electrically operated double diaphragm pump with all the qualities of an air operated pump without the use of compressed air.

There were no other high pressure coupled double diaphragm pumps on the market in the form similar to an AODD pump, that could offer pressures and flows required. There were a number of 'dosing' type pumps, but these were big, expensive, energy hungry, did not cope with vapour lock problem, and were single diaphragm design (although some had two heads 'duplex' these had the same issues as the singles in terms of vapour lock).

So in conclusion there did not appear to be any prior art of a hydraulically driven 'AODD' style pump offering the pressures and flow rates required.

With regard to air operated pumps (AODD) currently the lowest operating pressure we are aware of in the market place is from a company called TImmer-Pneumatik GmbH who publish a minimum pressure of 1 bar, but are selling pumps claiming a minimum pressure of 0.4 bar.

All manufacturers argue that their pump uses less energy than the others, but this is tantamount to impossible to get solid data upon with most figures simply stating that they are x% better than the rest. However all these pumps have only one air supply therefore have the same fundamental issue of requiring a minimum pressure to operate the air control valve. Therefore the LEAP technology stands alone in this area. There are a variety of complimentary electronic devices on the market that claim to reduce the air consumed by AODD pumps. These are typically installed in the air supply line to the pump and by monitoring the incoming air flow/pressure they either modulate the flow to minimise over shot, or try to predict the optimum switching point, however by virtue of the design of the majority of AODD pumps on the market a pressure of 1 -2 bar is required to switch the integral air control valve. Therefore these products do not offer a satisfactory solution to the fundamental problem. These products are added to an existing pump, and are therefore different to our solution.

We embarked on designing a new double diaphragm pump control method, combined with a single seal design.

We designed a custom PCB using a PIC (programmable integrated controller) with our own designed firmware. The PCB incorporates two south sensitive proximity switches (data sheets available) mounted back to back that detect the proximity of two opposing south facing ring magnets mounted within the diaphragm coupling shaft. The position of the magnets in relation to the sensors is fed back into the PIC firmware that in turn controls an external solenoid operated air valve that in turn control the direction of the diaphragms. See TPUK 00216 & 00217 below.

This method of sensing the diaphragms position is not pressure dependant, once the diaphragm has moved sufficiently for the magnet to be visible to the proximity sensor it changes its state and sends the diaphragm in the opposite direction towards the opposing sensor and so on. Therefore there is no spike in pressure at the end of stroke. As this method is indirect it does not require any pressure tapings from within the pump, therefore we only need one main seal, thus the friction is significantly reduced and the pump can run at very low pressure circa 0.1 bar, which is unique in the market.

The single seal was selected for both pneumatic and hydraulic applications, so the design was suitable for the high pressure application as the means of switching the control valve on a hydraulic power pack. This has been tested at pressures up to 40 bar, and flows of up to 25 l/min, at motor ratings as low as 90 watts. This also appears unique in the market. As the position sensing is indirect removing the end of stroke pulse the resultant flow from a diaphragm pump using the LEAP technology is practically pulse free. Pulses are common to all AODD pumps so there are a number of pulsation dampeners available on the market that are retro fitted to the discharge of AODD pumps to reduce the pulsing. The need for a complimentary dampener is eradicated using LEAP technology.

The external air control valve is an externally piloted 5/2 solenoid/spring valve (available from a variety of manufacturers). By having a control pressure and a pump pressure connection the valve can be piloted at a higher pressure than the pump. The higher pressure circuit is minimised to a few mL reducing the energy required to the bear minimum. Therefore the pump can be operated at any pressure from 0.1 to 40 bar.

The output to the solenoid valve is modulated to minimise energy consumption still further. Especially important on the hydraulically driven pumps as the control valve coil wattage is circa 30 watts. By modulating at 50% duty after an initial spike the electrical power consumption is reduced by a further 75%.

The PCB/firmware has an output that can be used by an external control system such as a PLC to offer additional control features. This would normally require an additional component, but is incorporated in the LEAP design.

We know that a LEAP technology AODD pump can be driven hydraulically, not requiring any compressed air. Therefore the next area of development to incorporate the hydraulic gear pump, control valve and tank into the centre section, this will give an electric double diaphragm pump that can run dry and self prime, it also offers higher pressures than air driven AODD pumps, and very low electrical power ratings as the hydraulic power pack is running at the bottom of its curve.

The use of a double diaphragm pump, with this control technique, and the single seal principle are as far as we know is unique to the market.

1 . The use of proximity sensors in conjunction with ring magnets mounted within the diaphragm coupling shaft to control the end of stoke and reciprocation of a double diaphragm pump.

2. The single seal principle. 3. The use of a hydraulic power pack to drive an 'AODD' pump with LEAP technology.

4. The combination of LEAP technology and all the components of a hydraulic power pack into a centre section of an AODD pump to give an electric diaphragm pump.

5. The design of the pump for high pressure applications

By reducing the energy required to switch a traditional shuttle valve within an Air diaphragm pump will reduce the energy required, traditionally the air diaphragm pump requires a minimum of 1 -2 bar to even start due to the air valve technology by using the single seal with the LEAP technology we are able to start the pumps and operate at 0.1 of a bar greatly reducing the energy required to switch the air valve

A double diaphragm pump utilising LEAP technology centre benefits :

• Can be used either pneumatically or hydraulically

• Hydraulic application does not require any compressed air.

• Very low energy consumption (air or electric/hydraulic).

• Ultra low friction giving practically 0 bar starting pressure.

• Pulse free flow (negating the need for a dampener)

• Able to withstand positive suction pressures of up to 18.5 bar, even using PTFE diaphragms (T50 with support plate).

• Improved suction.

• External air valve for pneumatic application.

• Pneumatic operation can be started/stopped by switching the 24vdc supply on/off OR turning the compressed air supply on/off.

• Hydraulic operation can be started/stopped by turning the power pack supply on/off.

• Impossible to stall.

• Capable of pressures up to 30 bar (proven) 50 bar theoretical when hydraulically driven. • Electronic output signal (24vdc) gives direct feedback into a PLC for stroke counting, etc'.

Could be driven with water, hydraulics or other media and gases