GB1595787A - Apparatus for controlling the flow of a fluid - Google Patents

Description

(54) IMPROVEMENTS IN AND RELATING TO APPARATUS FOR CONTROLLING THE FLOW OF A FLUID (71) We, LOVELY & ORCHARD SER VICES LIMITED, a British Company, of Africa House, Kingsway, London, WC23 6AH, de hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be described in and by the following statement : This invention relates to apparatus for controlling the flow of a fluid and has particular, but not exclusive application to use in a district heating system or a combined heat and power system in which hot water from a central source is distributed to a plurality of houses, flats or like dwellings.

The present invention employs a positive displacement device for connection in a fluid supply duct, and by the term "positive displacement device " we mean a device including an inlet and an outlet for connection to fluid inlet and outlet ducts respectively, and a member to be moved by an amount dependent upon the volume of fluid that passes through the device from the inlet to the outlet, the device being so arranged that upon the member being held stationary, substantially no fluid flows from the inlet to the outlet.

According to the present invention there is provided apparatus for controlling the flow of a fluid in a district heating system or combined heat and power system, comprising a positive displacement device, as hereinbefore defined, having its inlet and outlet arranged for connection to inlet and outlet ducts in the district heating or combined heat and power system so that at least a proportion of fluid flowing in the system flows through the device, the apparatus including means to control the rate of movement of the movable member of the device and so to control the fluid flow through the device when the device is connected in the system.

There is also provided according to the present invention apparatus for controlling the flow of a fluid including first and second positive displacement devices as hereinbefore defined, the two devices being arranged in series so that in use, at least a proportion of fluid flowing through the first device flows also through the second device, means being provided to control the rate of movement of the movable member of at least one of the devices. to control the passage of fluid through the apparatus, one of the devices being arranged to act, in use, as a pump and to raise the pressure of fluid flowing through it and the other device being arranged to act, in use, as a motor driven by, and so reducing the pressure of, fluid Rowing through it.

There is also provided according to the present invention apparatus for controlling the flow of fluid, including two positive displacement devices, the apparatus having a high pressure side arranged to be connected, in use, to two high fluid pressures at the inlet to the first device and the outlet from the second drive, and a low pressure side arranged to deliver two lower fluid pressures at the outlet to the first device and the inlet to the second device.

There is also provided according to the present invention a district heating system above connected between the supply and return lines of a district heating or combined heat and power system.

There is also provided according to the present invention a distinct heating system or a combined heat and power system including apparatus as specified above.

In one particular form of apparatus in accordance with the invention two positive displacement devices are provided having their movable members connected together, one of the devices being for connection in a supply duct and the other device being for connection to a lower pressure return duct that receives fluid through a load from the supply duct. Such an arrangement is responsive to the differential pressure between the supply and return ducts and in the event of a leak in the ducts between the devices, the maximum flow rate through the leak will be determined by the differential pressure between the supply and return ducts rather than the absolute pressure in the ducts.

In order that the invention may be more fully understood and readily carried into effect several embodiments thereof will now be described by way of example with re ference to the accompanying drawings in which Figure 1 is a schematic block diagram of an apparatus in accordance with the inven tion which incorporates a positive displace ment device, Figure 2 is a perspective view in partial section of one exemplary form of a positive displacement device for use in the apparatus shown in Figure 1, Figure 3 is a schematic block diagram of another form of apparatus in accordance with the invention, Figure 4 is a schematic block diagram of another from of apparatus in accordance with the invention, arranged to control the flow in both supply and return ducts of a district heating system, Figure 5 illustrates another form of apparatus for use in the same situation as the valve of Figure 4, Figure 6 illustrates a modification of the arrangement shown in Figure 4, and Figure 7 illustrates a further modification of the arrangement shown in Figure 4.

The apparatuses described hereinafter have particular application to use in a district heating system in which hot water is circulated between a central boiler house and a plurality of houses, flats, shops and like dwellings. The apparatuses have particular application to providing a record of the volume of hot water flowing through particular dwellings, and also to limiting the maximum flow rate to each dwelling to a predetermined value. The control valves are also provided with a facility to shut off the supply of hot water in the event of a burst pipe in the dwelling, by shutting off the supply in response to the flow rate exceeding the predetermined maximum value.

Referring firstly to Figure 1, there is shown apparatus which is arranged to control and measure the flow of water in an inlet duct 1 to an outlet duct 2. The valve includes a register, or so-called meter, 3 to provide a record of the volume of water that flows from the inlet duct 1 to the outlet duct 2. The apparatus further includes a governor 4 to limit the maximum water flow rate from the inlet to the outlet duct, and an overspeed trip 5 to prevent flow of water to the outlet if the flow rate exceeds the maximum value set by the governor.

The meter 3, the governor 4 and the overspeed trip 5 are driven by a rotary positive displacement device 6 connected to the inlet and outlet ducts 1 and 2 as is shown in Figure 1. The positive displace ment device includes a generally cylindrical casing 7 having therein a water inlet orifice 8 to receive water from the duct 1 and a water outlet orifice 9 to transmit water to the outlet duct 2. The circular ends of the casing 7 are closed in a water tight manner by end caps 10, only one of which is shown in Figure 2. Received within the casing 7 is an eccentric rotary paddle wheel 11 having resiliently deformable radially extending paddle blades 11A which seal- ingly and slidingly engage the inner cylindrical surface of the casing.

Thus, water flowing from the inlet duct 1 to outlet duct 2 will cause the paddle wheel 11 to rotate by an amount dependent upon the volume of water flowing, and at a rate that is proportional to the water flow rate. Also, it will be seen that if the paddle wheel is locked so that it cannot rotate, water is unable to flow from the inlet duct 1 to the outlet duct 2.

Rotation of the paddle wheel 11 is transmitted to the meter 3, the governor 4 and the trip 5 by means of a shaft 12.

The meter 3 can be of any suitable form and can be a mechanical or an electrical device which is responsive to rotation of the shaft 12.

The mechanical speed governor 3 also can be of any suitable type and is arranged to limit the rotational speed of the shaft 12 to a preset maximum value so as to limit the maximum rotational speed of the paddle wheel 11 and hence limit the maximum water flow rate from the inlet duct 1 to the outlet duct 2. The governor can be of any of the conventional mechanical types such as a conical pendulum governor, a Porter, Pröll's, Pickering, or Farcot's governor, as shown in Figure 1. Alternatively, the governor could be electrically operated.

Clearly, the governor can include means for permitting selective adjustment of the maximum speed whereby to permit selective alteration of the maximum water flow rate.

The overspeed trip S is arranged to lock stationary the shaft 12 and hence the paddle wheel 11 in the event that the rotational speed of the shaft 12 exceeds the maximum value set by the governor 4. Thus in the event of a burst pipe in the dwelling which would cause a very high water flow rate to develop, the trip 5 causes the paddle wheel 11 to be locked stationary and thereby prevents water from being discharged at the high rate into the outlet duct 2 and into the dwelling. The particular form of trip 5 used will probably depend upon the kind of governor 4 utilised, but as will be apparent to those skilled in the art, numerous different mechanical and electrical trips could be used.

Another form of the apparatus is shown in Figure 3. in which like parts to those shown in Figure 1 are marked with like reference numerals. In the arrangement of Figure 3, the flow rate of water into the outlet duct 2 is controlled in response to the rotational speed of the shaft 12, but by means of an electrical servo mechanism which drives an electrically operated valve 13 connected in the outlet duct 2.

The shaft 12 is arranged to drive a rotational speed transducer 14 which pro vides an output voltage which has a magnitude proportional to the speed of the shaft 12. The output voltage is compared in a diflerential amplifier 15 with a reference voltage set by variable resistor VR1 to determine selectively the desired maximum permitted rotational speed of the shaft 12.

The output voltage from the amplifier 15 is fed through an OR gate 16 to operate the valve 13, and in this way, the valve 13 tends to prevent the flow rate in the outlet duct 2 exceeding a predetermined maximum value.

The output of the amplifier 15 is also connected to a threshold circuit 17 con nected to a bistable 18. Usually, the bistable is switched off, but in the event of the amplifier output voltage exceeding the threshold set by circuit 18, the bistable is triggered on, to apply a continuous signal to the valve 13, through the OR gate 16, to hold the valve shut. Thus in the event of a pipe burst, the rotational speed of shaft 12 will be such that the output voltage of the transducer will exceed the reference voltage such that the threshold 17 is triggered by the output voltage of amplifier 15, the valve 13 thereby being held shut to prevent water discharging from the burst pipe.

The apparatus shown in Figure 4 is connected in both the supply and return lines of a district heating system. A supply line 18 supplies hot water to the dwelling where it passes througha load comprising radiators and like heat exchangers illus trated schematically by a throttle 19. Cooled water emanating from the throttle 19 is fed back to the central boiler house through a return line 20. Water pumped into the supply line is usually at a high static pressure equivalent for example to a head of 400 feet of water. Some but not all of this pressure is dropped across the throttle 19, and thus the return line is also at a high pressure, equivalent for example to a head of 250 feet of water.It will be appreciated that in such a district heating system, if a pipe burst of leak occurs in the dwelling, an extremely high flow rate of water can occur into the dwelling due to the high pressure in both the supply and return lines to the boiler house. The apparatus of Figure 4 reduces substantially the likelihood of such high flow rate leakage occurring in the dwelling, and referring now to Figure 4 in detail, positive displacement devices, typically of- the kind described with reference to Figure 2, and which are referenced 6A .and 6B in Figure 4, are included in the supply and return lines 18, 19 respectively. The shafts 12A and 12B of the positive displacement devices are ganged together by means of a gear chain including gears 21 and 22 such that each device 6 tends to be driven in a reverse direction by the other thereof.Connected to the shaft 12A is a meter 3, a speed governor 4 and an overspeed trip 5 which operate in a similar way to those described with reference to Figure 1. At least one of the positive displacement devices 6, and preferably the device 6A in the return line, is provided with a very low flow rate bypass bleed path, illustrated schematically by a line 23 and a throttle 24, to prevent a hydraulic lock being formed by water between the devices 6.

In normal operation of the arrangement shown in Figure 4, hot water flows from the supply line 18 to the return line 20 through the positive displacement devices 6, the maximum flow rate being limited by means of the speed governor 4. Thus the governor 4 will control the maximum differential pressure established across the throttle 19.

However, in the event of a pipe burst in the dwelling, the positive displacement devices 6 ensure that the maximum flow rate to the leak is determined by the difference in pressure between the supply and the return lines 18 and 20, and the interconnection of the devices 6 is such that back flow of water to the leak from the return line is prevented by the positive displacement device 6A (any flow through the bypass 23 being negligible). Thus in the event of a pipe leak or burst, the devices 6 are driven towards the maximum rate determined by governor 4. If the leak or burst is large enough the devices 6 will drive the shaft even faster thereby operating the trip 5 so as to lock both of the devices stationary and consequently preventing water under pressure in both of the lines 18 and 20 flowing to the leak or burst.

Clearly, the modifications to the com- ponents 3, 4 and 5 which are describd with reference to Figures 2 and 3, can be included in the arrangement of Figure 4 as described.

Also, the arrangement of the positive displacement devices can be modified for example as shown in Figure 5, so that they are arranged on a common shaft 12 thereby eliminating the gears 21 and 22. To this end, the supply water from line 18 and the water flowing from the throttle 19 is arranged to flow in the same direction through respective ones of the devices 6A, 6B. The meter 3, the speed governor 4 and thi overspeed trips are artanged between the devices 6A, 6B and are connected thereto by the shaft 12. However, the coupling between the device 3, 4 and 5 and the devices 6A, 6B could be magnetic thereby permitting the paddle wheels 11 to be housed within a casing without the need for a seal to be provided in the casing around the shaft 12.

The arrangement of Figure 4 permits not only the diffetential pressure across the throttle 19 to be controlled, but also permits the absolute pressure pertaining in a line section il8a downstream of the positive displacement device 6B to be lower than the supply pressure in the line 18 upstream of the device 6B. Similarly, the pressure in the return line section 20a between the throttle 19 and the device 6A can be less than the pressure in the return line 20 downstream of the device 6A and thus, the arrangement can be such that the device 6B acts as a throttle to reduce the pressure of water entering a dwelling by virtue of a braking force applied to the rotary paddle wheel of the device 6B by the device 6A.

Similarly, the device 6A is driven by the device 6B to pump water leaving the dwelling to the higher pressure of the return line 20 upstream of the device 6A. Thus, the control valve permits the pressure in the supply and return lines in a dwelling to be reduced substantially below the supply and return pressures to the central boiler house, which provides for an intrinsically safer plumbing system in the dwelling than if the full supply pressure were to be applied to the domestic radiators and hot water cylinder that typically constitute the throttle 19.

In practice, however, there will be a small leakage of water past the rotary paddle wheels of the positive displacement devices which will not cause rotation of the paddle wheels, and this leakage will tend to degrade any pressure difference established between the inlets and outlets of the devices.

A modification is shown in Figure 6 in which the effects of such leakage is overcome by the use of an auxiliary positive displacement pump 25 connected in parallel with the positive displacement device 6A in the return line. Operation of the pump 25 is controlled in response to a pressure sensor 26 connected in the low pressure return line section 20a, and thus the pump will operate to tend to maintain the pressure in the line section 20a at a constant level thereby overcoming the effects of any leakage through the positive displacement devices. The pump could be electrically driven or could be driven by a spring wound by rotation of the shafts 12 of the positive displacement devices 6.

Another modification for overcoming the effects of leakage through the positive displacement devices of Figure 4, is shown in Figure 7. In this arrangement, the device 6A is arranged to be of a larger capacity than the device 6B, so that the device 6A pumps water back into the return line 20 at a higher rate than the rate at which the device 6B delivers water to the throttle 19.

In order to maintain the absolute pressure in the line section 20n substantially constant, a needle valve 27 is connected in parallel with the device 6B and is operated in response to the pressure in the line section 20a so as to allow water to by-pass the device 6B if the pumping action of the device 6A produces too great a pressure reduction in the line 6A. A suitable specific construction of the needle valve 27 will be readily apparent to those skilled in the art and could for example comprise a needle biassed to a closed position by a spring and urged to open by the action of a diaphragm, air pressure acting on one side of the diaphragm and the pressure of water in the line section 20a acting on the other side thereof.

The modifications described with reference to Figures 6 and 7 preclude the possibility of a hydraulic lock occurring between the positive displacement devices and also accommodate the change in water density which will occur as a result of cooling across the throttle 19.

Many further modifications to the above described embodiments of the invention will be readily apparent to those skilled in the art, and thus whilst one form of positive displacement has been described in detail herein, other embodiments thereof will be readily apparent. For example, a Wankel rotor, or a Rootes blower rotor or a rotary positive displacement gas meter type or a rotary piston pump could be used.

It will also be appreciated that if required, the meter 3 can be modified to provide a log of the quantity of heat carried by the water through the apparatus. To this end, a temperature transducer is attached to the inlet and outlet ducts, and means are provided to integrate the volume measurement produced by the meter with respect to the sensed temperature.

WHAT WE CLAIM IS: 1. Apparatus for controlling the flow of a fluid in a district heating system or a combined heat and power system, the apparatus comprising a positive displacement device, as hereinbefore defined, having its inlet and outlet arranged for connection to ducts in the district heating or combined heat and power system so that at least a proportion of fluid flowing in the system flows through the device, the apparatus including means to control the rate of movement of the movable member of the device and so to control the

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

Claims (35)

**WARNING** start of CLMS field may overlap end of DESC **. the devices 6A, 6B and are connected thereto by the shaft 12. However, the coupling between the device 3, 4 and 5 and the devices 6A, 6B could be magnetic thereby permitting the paddle wheels 11 to be housed within a casing without the need for a seal to be provided in the casing around the shaft 12. The arrangement of Figure 4 permits not only the diffetential pressure across the throttle 19 to be controlled, but also permits the absolute pressure pertaining in a line section il8a downstream of the positive displacement device 6B to be lower than the supply pressure in the line 18 upstream of the device 6B. Similarly, the pressure in the return line section 20a between the throttle 19 and the device 6A can be less than the pressure in the return line 20 downstream of the device 6A and thus, the arrangement can be such that the device 6B acts as a throttle to reduce the pressure of water entering a dwelling by virtue of a braking force applied to the rotary paddle wheel of the device 6B by the device 6A. Similarly, the device 6A is driven by the device 6B to pump water leaving the dwelling to the higher pressure of the return line 20 upstream of the device 6A. Thus, the control valve permits the pressure in the supply and return lines in a dwelling to be reduced substantially below the supply and return pressures to the central boiler house, which provides for an intrinsically safer plumbing system in the dwelling than if the full supply pressure were to be applied to the domestic radiators and hot water cylinder that typically constitute the throttle 19. In practice, however, there will be a small leakage of water past the rotary paddle wheels of the positive displacement devices which will not cause rotation of the paddle wheels, and this leakage will tend to degrade any pressure difference established between the inlets and outlets of the devices. A modification is shown in Figure 6 in which the effects of such leakage is overcome by the use of an auxiliary positive displacement pump 25 connected in parallel with the positive displacement device 6A in the return line. Operation of the pump 25 is controlled in response to a pressure sensor 26 connected in the low pressure return line section 20a, and thus the pump will operate to tend to maintain the pressure in the line section 20a at a constant level thereby overcoming the effects of any leakage through the positive displacement devices. The pump could be electrically driven or could be driven by a spring wound by rotation of the shafts 12 of the positive displacement devices 6. Another modification for overcoming the effects of leakage through the positive displacement devices of Figure 4, is shown in Figure 7. In this arrangement, the device 6A is arranged to be of a larger capacity than the device 6B, so that the device 6A pumps water back into the return line 20 at a higher rate than the rate at which the device 6B delivers water to the throttle 19. In order to maintain the absolute pressure in the line section 20n substantially constant, a needle valve 27 is connected in parallel with the device 6B and is operated in response to the pressure in the line section 20a so as to allow water to by-pass the device 6B if the pumping action of the device 6A produces too great a pressure reduction in the line 6A. A suitable specific construction of the needle valve 27 will be readily apparent to those skilled in the art and could for example comprise a needle biassed to a closed position by a spring and urged to open by the action of a diaphragm, air pressure acting on one side of the diaphragm and the pressure of water in the line section 20a acting on the other side thereof. The modifications described with reference to Figures 6 and 7 preclude the possibility of a hydraulic lock occurring between the positive displacement devices and also accommodate the change in water density which will occur as a result of cooling across the throttle 19. Many further modifications to the above described embodiments of the invention will be readily apparent to those skilled in the art, and thus whilst one form of positive displacement has been described in detail herein, other embodiments thereof will be readily apparent. For example, a Wankel rotor, or a Rootes blower rotor or a rotary positive displacement gas meter type or a rotary piston pump could be used. It will also be appreciated that if required, the meter 3 can be modified to provide a log of the quantity of heat carried by the water through the apparatus. To this end, a temperature transducer is attached to the inlet and outlet ducts, and means are provided to integrate the volume measurement produced by the meter with respect to the sensed temperature. WHAT WE CLAIM IS:

1. Apparatus for controlling the flow of a fluid in a district heating system or a combined heat and power system, the apparatus comprising a positive displacement device, as hereinbefore defined, having its inlet and outlet arranged for connection to ducts in the district heating or combined heat and power system so that at least a proportion of fluid flowing in the system flows through the device, the apparatus including means to control the rate of movement of the movable member of the device and so to control the

fluid flow through the device when the device is connected in the system.

2. Apparatus as claimed in claim 1 including an electrically operable valve connected to the outlet of the device, means arranged to generate a first electrical signal indicative of the rate of movement of the movable member of the device, means for establishing a second, predetermined, electrical signal indicative of a desired maximum fluid flow rate through the device, and means arranged to compare the first and second signals and to control the opening of the valve in dependence upon the result of the comparison.

3. Apparatus as claimed in claim 1 or 2 including a second positive displacement device, as hereinbefore defined, arranged in series with the first positive displacement device so that in use at least a proportion of fluid flowing through the first device flows through the second device.

4. Apparatus as claimed in claim 3 wherein one of the devices is arranged to act, in use, as a pump and to raise the pressure of fluid flowing through it and the other device is arranged to act, in use, as a motor driven by, and so reducing the pressure of, fluid flowing through it.

5. Apparatus for controlling the flow of a fluid including first and second positive displacement devices as hereinbefore defined, the two devices being arranged in series so that, in use, at least a proportion of fluid flowing through the first device flows also through the second device, means being provided to control the rate of movement of the movable member of at least one of the devices to control the passage of fluid through the apparatus, one of the devices being arranged to act, in use, as a pump and to raise the pressure of fluid flowing through it and the other device being arranged to act, in use, as a motor driven by, and so reducing the pressure of, fluid flowing through it.

6. Apparatus for controlling the flow of a fluid including two positive displacement devices, the apparatus having a high pressure side arranged to be connected in use to two high fluid pressures at the inlet to the first device and the outlet from the second device, and a low pressure side arranged to deliver two lower fluid pressures at the outlet to the first device and the inlet to the second device.

7. Apparatus as claimed in claim 6, the apparatus being arranged to convert a first, high, average pressure at the high pressure side to a desired, second, low, average pressure at the low pressure side.

8. Apparatus as claimed in claim 6 or 7, the apparatus being arranged to convert a first differential pressure at the high pressure side to a desired, second, differential pressure at the low pressure side.

9. Apparatus as claimed in any one of claims 3 to 8, means being provided to control the rate of movement of the movable members of both of the devices to control the passage of fluid through the apparatus.

10. Apparatus as claimed in any one of claims 3 to 9 including means connected to the two devices and arranged such that the rate of movement of the movable member of one of the devices influences the rate of movement of the movable member of the other device.

11. Apparatus as claimed in claim 10, wherein the movable members of the two devices are linked together mechanically.

12. Apparatus as claimed in claim 10 or 11, wherein the two devices are connected together in such a way that, in use, one device, acting as a motor, drives the other device, acting as a pump.

13. Apparatus as claimed in claim 11 or 12 wherein the two devices are mounted upon a single shaft.

14. Apparatus as claimed in claim 11 or 12 wherein the two devices are mounted upon different shafts connected together by gearing.

15. Apparatus as claimed in any one of claims 3 to 14 wherein, in use, fluid entering the apparatus flows first to one of the devices arranged to act as a motor and then to one of the devices arranged to act as a pump.

16. Apparatus as claimed in any preceding claim including means for measuring the amount Qf movement performed by the movable member of the device, or of at least one of the devices, and so measuring the amount of fluid flowing through the apparatus.

17. Apparatus as claimed in any preceding claim including means for measuring the temperature of the fluid entering and leaving the apparatus.

18. Apparatus as claimed in any preceding claim including means for locking the movable member of the device, or of at least one of the devices, stationary if the flow rate of the fluid should rise above a predetermined value.

19. Apparatus as claimed in any preceding claim including means arranged to prevent the movable member of the device, or of at least one of the devices, from moving, in use, at a speed above a predetermined speed.

20. Apparatus as claimed in any preceding claim and including a bypass passageway connected between the inlet and the outlet of the device, or of at least one of the devices, the bypass passageway being so arranged that in use the rate of flow of fluid through the bypass passageway is sub stantially less than that through the bypassed device.

21. Apparatus as claimed in any preceding claim and including a bypass passageway connected between the inlet and the outlet of the device, or of at least one of the devices, and a positive displacement pump arranged to pump fluid, in use, through the bypass passageway.

22. Apparatus as claimed in any one of claims 3 to 6 or as claimed in any one of claims 7 to 21 when dependent directly or indirectly upon any one of claims 3 to 6, wherein one of the devices has a greater flow capacity than the other, the device of less flow capacity having connected between its inlet and outlet a bypass passageway.

23. Apparatus as claimed in claim 20, 21 or 22 including means for varying selectively the flow of fluid through the bypass passageway.

24. Apparatus as claimed in any one of claims 3 to 6 or any one of claims 7 to 23 when dependent directly or indirectly upon any one of claims 3 to 6, wherein one of the devices is connected to a fluid supply line and the other device is connected to a fluid return line, a throttle being connected in circuit between the two devices.

25. Apparatus as claimed in any preceding claim wherein the device, or at least one of the devices, comprises a casing and a rotary paddle wheel located eccentrically within the casing and having resiliently deformable paddle blades which, in use, engage the casing.

26. Apparatus as claimed in any one of claims 5 to 25 for controlling the flow of a fluid in a district heating system or a combined heat and power system.

27. Apparatus as claimed in any preceding claim connected between the supply and return lines of a district heating system or a combined heat and power system.

28. A district heating or combined heat and power system including apparatus as claimed in any preceding claim.

29. Apparatus for controlling the flow of a fluid substantially as herein described with reference to Figure 1 of the accompanying drawings.

30. Apparatus for controlilng the flow of a fluid substantially as herein described with reference to Figure 2 of the accompanying drawings.

31. Apparatus for controlling the flow of a fluid substantially as herein described with reference to Figure 3 of the accompanying drawings.

32. Apparatus for controlling the flow of a fluid substantially as herein described with reference to Figure 4 of the accompanying drawings.

33. Apparatus for controlilng the flow of a fluid substantially as herein described with reference to Figure 5 of the accompanying drawings.

34. Apparatus for controlilng the flow of a fluid substantially as herein described with reference to Figure 6 of the accompanying drawings.

35. Apparatus for controlling the flow of a fluid substantially as herein described with reference to Figure 7 of the accompanying drawings.