GB2563207A

GB2563207A - Liquid transfer device

Info

Publication number: GB2563207A
Application number: GB1708834.5A
Authority: GB
Inventors: Lambden Peter
Original assignee: Stuart Turner Ltd
Current assignee: Stuart Turner Ltd
Priority date: 2017-06-02
Filing date: 2017-06-02
Publication date: 2018-12-12
Also published as: GB201708834D0

Abstract

A liquid transfer device is provided. The liquid transfer device comprises: a liquid conduit 51 with a liquid inlet at one end and a liquid outlet at an opposite end; and a gas chamber 57 adjacent to the liquid conduit 51 and separated therefrom by a flexible membrane 58. The gas chamber 57 allows a trapped volume of gas to be retained and to act as a volume expansion accommodator. A degree of volume expansion of the liquid within the system can be absorbed by movement of the flexible membrane 58 which allows an increase in volume of the liquid conduit 51 and a corresponding decrease in volume of the gas chamber 57. This performs the same function as a traditional accumulator, but is provided in line with the liquid flow path, with liquid flowing through it rather than being provided as a buffer that is T-connected to the flow path. The flexible membrane 58 thus forms atleast a part of the wall (or walls) of the liquid conduit 51 such that liquid flowing through the conduit flows past the flexible membrane 58 rather than simply pressing against it as is the case with traditional T-connected accumulators.

Description

Liquid Transfer Device

The application relates to pressurised fluid systems, in particular fluid delivery systems such as domestic and commercial water supply systems. Such systems may be vented (open to the atmosphere) or sealed (not able to vent to the atmosphere). The sealed system is typically separated from the vented supply by a non-return valve.

In a sealed system (i.e. one that is not vented to the atmosphere), the fluid within the system will undergo volumetric change due to variations in ambient temperature. This volumetric change causes pressure fluctuations within the system. In the absence of any pressure compensation means, the pressure fluctuations within the system can result in high pressures. For example pressures may typically exceed 20 bar which may cause damage to equipment within the system leading to leakage of fluid and potentially causing damage to the affected property.

To address this problem, sealed systems have to date typically incorporated a gas charged bladder accumulator. This accumulator is typically either fitted to a part of the fluid system or incorporated as part of a pump supplying the fluid pressure. A typical gas charged bladder accumulator has two chambers, one with a preset gas charge and a second chamber accessible to the system fluid. Between these two chambers there is a flexible membrane, typically made from rubber. As the fluid volume changes the membrane moves to accept the volume change, compressing the gas in the gas chamber slightly as a result. The compressibility of the gas allows the liquid volume change to be accommodated with a significantly reduced pressure change in the system. Thus the system does not experience such high pressures and is less at risk of damage.

Additionally, the application of accumulator technology within pumped systems and more specifically pump units, may be used to ensure the correct operation of switching systems, such as pressure transducers or pressure switches. Without an accumulator such pressure sensitive devices would be likely to operate incorrectly under the higher pressure fluctuations.

Commercially available accumulators are typically cylindrical with a fluid port at one end, and a gas charge valve at the other (allowing the gas pressure to be set to a desired level, and topped up as required over time). Such accumulators are usually bulky and difficult to incorporate into the design of an integrated pump.

As part of the installation of a pump assembly, flexible fluid connectors are typically fitted to the inlet and outlet ports of the pump to reduce the transmission of noise and vibration to the connected system and to ease the alignment of the connecting pipework during the installation.

The flexible fluid connector fitted to the system are typically an inner elastomer fluid tight tube with a woven outer to provide mechanical strength to the inner tube. Both inlet and outlet fluid connectors are normally of a similar design and size.

According to the invention there is provided a liquid transfer device comprising a liquid conduit with a liquid inlet at one end and a liquid outlet at an opposite end and a gas chamber adjacent to the liquid conduit and separated therefrom by a flexible membrane.

The gas chamber allows a trapped volume of gas (typically air) to be retained and to act as a volume expansion accommodator. A degree of volume expansion of the liquid within the system can be absorbed by movement of the flexible membrane which allows an increase in volume of the liquid conduit and a corresponding decrease in volume of the gas chamber (resulting in an increased gas pressure within the gas chamber). This performs the same function as a traditional accumulator, but is provided in line with the liquid flow path, with liquid flowing through it rather than being provided as a buffer that is T-connected to the flow path. The flexible membrane thus forms at least a part of the wall (or walls) of the liquid conduit such that liquid flowing through the conduit flows past the flexible membrane rather than simply pressing against it as is the case with traditional T-connected accumulators. As this pressure accommodator is provided in line it is more space efficient. Moreover, as conduit is always required to connect the various components of a liquid system, some lengths of that conduit can be replaced with the conduit of the invention so as to provide for volume expansion without significant (if any) increase in the space requirements of the system. In particular, a separate accumulator unit can be avoided or at least reduced significantly in size. This allows the system to be installed in a smaller space and/or provide less of an obstruction. This is a particular benefit in smaller domestic installations where the available installation space can be small.

The amount of volume expansion that can be accommodated will depend on a number of factors such as the volume of the gas chamber and the pressure therein. This will in turn be determined for example by the diameter of the conduit and the length of the conduit. Where more volume expansion needs to be accommodated, either a wider or longer conduit can be used or multiple smaller units can be connected in series, each accommodating a certain amount of volume expansion. Thus with the liquid transfer device of the invention, the amount of volume expansion can readily be tailored to each particular installation.

While the liquid transfer device may have a single gas chamber, in certain preferred embodiments the liquid transfer device comprises a plurality of gas chambers each adjacent to the liquid conduit and separated therefrom by a flexible membrane. The use of a plurality of gas chambers can allow better pressure distribution around the liquid transfer device. Where a plurality of gas chambers are used, each individual gas chamber may be smaller, resulting in a greater amount of structural material forming chamber walls and a greater overall strength (which may provide a greater maximum pressure). The increased pressure may be distributed along the length of the liquid transfer device, or circumferentially around the liquid transfer device.

To achieve this, the liquid transfer device may comprise a plurality of gas chambers separated lengthwise along the length of the liquid conduit. Additionally or alternatively the liquid transfer device may comprise a plurality of gas chambers separated circumferentially around the liquid conduit.

The gas chamber(s) preferably form at least part of a body of the liquid conduit.

The volumetric changes within the system are thus absorbed by the body of the liquid conduit itself.

Where more than one gas chamber is used, the same membrane may separate all gas chambers from the liquid conduit or a number of different membranes may be provided, each separating one or more gas chambers from the liquid conduit.

Where a plurality of gas chambers are used, the gas chambers may be completely separate, individual chambers. In such cases each chamber may be pressurised differently (e.g. by pressurizing each chamber via its own pressurization valve to its own internal chamber pressure). However in certain preferred embodiments the plurality of gas chambers are fluidly interconnected. With the gas chambers being fluidly interconnected, gas will flow between the chambers so as to equalise the pressure in all chambers and ensure the pressure is evenly distributed.

Additionally, with all gas chambers being fluidly interconnected, a single pressurization port can be used to pressurize all the chambers at once rather than requiring a separate port for each chamber.

The liquid conduit may take any suitable form and may be at least partially rigid (any parts other than the flexible membrane), e.g. for high pressure systems. The gas chamber may be formed internally (or partly internally) of the liquid conduit (i.e. with liquid flowing around the gas chamber). However, preferably the liquid conduit is a flexible tube at least partially surrounded by the or each gas chamber. The tube (or hose) being flexible is convenient as the conduit and gas chambers may all be moulded from flexible materials, e.g. elastomers such as rubber. The conduit and gas chambers and flexible membrane may in some embodiments be formed from the same material. In some embodiments the gas chamber(s) may be formed as a separate unit, insertable into the main body of the liquid transfer device. This arrangement may be particularly convenient with the use of foams discussed further below. In other embodiments the liquid conduit and the or each gas chamber may be integrally formed from the same material. Thus the liquid transfer device as a whole may be a flexible conduit or flexible hose such that it can easily make fluid connections to the system in which it is to be used, without requiring exact alignment of those connections and indeed allowing the liquid transfer device to take a non-straight path between them if required (e.g. by other constraints of the installation space).

The gas chambers and the liquid conduit may be designed to have any shape that is convenient for a particular installation or use. However, in preferred embodiments the or each gas chamber extends substantially the length of the liquid conduit. Such an arrangement is particularly convenient for manufacture as it allows the cross-sectional shape of the device to be constant along the length of the conduit. This makes moulding easier and allows the device to be produced by extrusion. As well as reducing the manufacturing costs, this allows the length of the conduit and gas chambers to be varied easily so as to produce different length products with different volume expansion capabilities.

In order to allow variation of the pressure within the gas chamber(s), or repressurization thereof, a gas inlet is preferably provided to permit pressurization of the or each gas chamber. As mentioned above, if a plurality of separate chambers are provided, a gas inlet can be provided for each. The gas inlet may comprise a non-return valve.

Depending on the pressures involved and the materials from which the liquid transfer device is made, there may be no need for any further reinforcement around the conduit and/or gas chamber(s). For example if the gas chamber is internal of the liquid conduit and the liquid conduit has a rigid exterior then no further reinforcement will be necessary. In other examples, if thick rubber walls are provided that can withstand deformation due to increased pressure then no further reinforcement is required. However, a rigid device is not always convenient and the use of thick walls increases the overall size of the device. Therefore in certain preferred embodiments a flexible sheath surrounds the liquid conduit and the or each gas chamber. The flexible sheath can be made from a stronger tensile material that resists expansion and therefore allows the walls of the liquid conduit and gas chamber(s) to be formed thinner, relying on the flexible sheath for some of their strength. The flexible sheath allows the liquid transfer device as a whole to be flexible, thus allowing it be deployed with a certain degree of freedom, e.g. placed along a suitable path within each particular installation. The sheath is preferably resistant to expansion of the liquid conduit and the or each gas chamber. In certain preferred embodiments the sheath is a braided sheath. The sheath may be made from a tensile material such as a fabric, or it may be made from a braided metal structure that has good tensile strength but also flexibility.

In some examples the gas chamber (or in the case of a plurality of such gas chambers, at least one of them, preferably all of them) is at least partly filled with foam. The foam is preferably a closed cell foam, with gas trapped in the cells providing the required compressibility in order to effect compensation for volume expansion and/or contraction. With a closed cell foam, each cell essentially forms a compressible gas chamber and the cell walls of the foam can provide the flexible membrane that separates the liquid in the liquid conduit from the gas in the foam cells (gas chambers). Thus in the case of a closed cell foam, no separate flexible membrane is required in addition to the foam. This is particularly beneficial as it simplifies the manufacture of the liquid transfer device. The foam structure can be pre-formed and simply inserted inside the liquid transfer device (e.g. inside a flexible rubber hose) without the need for another membrane between it and the liquid as the cells are closed. The closed cell foam also provides good resistance characteristics under compression, thus allowing good accommodation of pressure changes in the liquid. The closed cell foam also has good shape memory so it will return to its natural form and shape after being compressed.

Thus in some preferred embodiments the liquid transfer device comprises a plurality of gas chambers, and the plurality of gas chamber are formed as a closed cell foam. In preferred embodiments the closed cell foam comprises cell walls and the flexible membrane is formed from the cell walls.

The liquid transfer device may be used in any system or part of a system that experiences volumetric expansion. For example any part of a liquid system downstream of a non-return valve may suffer such volume changes, e.g. due to liquid expansion/contraction due to temperature changes. Non-return valves are frequently placed close to pumps so as to retain the increased pressure generated by the pump even when the pump is not in use. Pumps are often supplied as a unit or kit together with such non-return valves and connectors for connecting the pump into the other pipework of the system. For example, pumps used in domestic water supply systems (e.g. for pumped showers or for enhancing the system pressure in general) may be supplied with the relevant valves and connectors for fitting the pump to domestic pipework. Thus the pump may be designed to incorporate a liquid transfer device such as that described here for connection to its outlet, optionally with an intermediate non-return valve. The fluid transfer device can then accommodate volume changes in the system after pressurization by the pump, e.g. due to temperature changes.

Accordingly, if the liquid transfer device is to be supplied for use with a pump, it is preferred that the liquid transfer device has a connector adjacent the liquid inlet (of the liquid transfer device) specifically designed for connection to the output of a pump unit. The connector can then simply be fitted to the pump quickly and easily during installation. A connector may also be provided on the outlet of the liquid transfer device for connection to the downstream pipework in a standard fashion.

According to a further aspect, the invention provides a pressurised liquid delivery system comprising: a pump; a non-return valve downstream of the pump; an inlet connector upstream of the pump; an outlet connector downstream of the non-return valve; and a liquid transfer device as described above (optionally including any of the optional or preferred features also described above), wherein the inlet connector and the outlet connector have different connection designs; and wherein a liquid transfer device inlet connector is designed to be attachable to the outlet connector and not attachable to the inlet connector. The difference in connectors ensures that the correct equipment is fitted to the inlet and outlet. For example, for effective operation the liquid transfer device must be connected downstream of the pump (and the non-return valve). Upstream of the pump a liquid connector is also required to plumb in the pump, but it need not have the capability to accommodate volumetric changes (and indeed for cost reasons would not normally have such capabilities). The use of different connector types ensures that the connectors are attached to the pump in the correct manner so as to ensure correct operation of the system after installation is complete.

Certain preferred embodiments of the invention will now be described, byway of example only, and with reference to the accompanying drawings in which:

Fig. 1 shows a prior art system with an accumulator;

Fig. 2 shows a first embodiment of a system with an integrated hose accumulator; Fig. 3 shows an embodiment of a liquid transfer device.

Figs. 4a-d show examples of cross-sections of a liquid transfer device.

Fig. 5 shows a second embodiment of a system with an integrated hose accumulator;

Fig. 1 shows a typical domestic water system 10 with a pump assembly 20 used to boost the water pressure downstream of the pump assembly 20. The pump assembly 20 comprises a number of different components that may be supplied as a kit. The kit may either be supplied as separate components to be fitted together by the installer or it may be ready assembled or part assembled, e.g. with several of the components ready mounted to a backboard or other mounting device. The pump assembly 20 comprises a pump 21, a one way valve 22, pump controls 23 and an accumulator 24. As shown, when installed, the pump one way valve 22 is downstream of the pump 21 so as to maintain the fluid pressure downstream of the pump 21 when the pump 21 is not running. The accumulator 24 is downstream of the one way valve 22 so that it can accommodate volumetric changes in the pressurized part of the system downstream of the one way valve 22. The pump controls 23 such as pressure switches, flow switches and associated electronics may be located either upstream or downstream of the one way valve 22, depending on the particular controls and installation. These controls monitor system pressure and/or flow to allow the pump to maintain the required system pressure by selectively activating the pump. In this example they are shown downstream of the one way valve 22. It will be appreciated that the one way valve 22 may be incorporated into the body of the pump 21 or may be a separate device.

The pump assembly 20 has an inlet 25 and an outlet 26. The pump assembly 20 is connected to the local system (e.g. domestic water supply system) at an inlet connection 27 via an inlet flexible fluid connector 28 and the pump assembly 20 is connected to the local system at an outlet connection 29 via an outlet flexible fluid connector 30. The inlet and outlet flexible fluid connectors 28, 30 are of conventional design and are typically formed from a rubber hose conduit covered by a protective metallic braided sheath that protects against puncture damage as well as providing tensile strength that resists radial deformation of the tube, while still remaining flexible so as to allow ease of connection without requiring exact alignment of the various pipe/pump assembly connections.

Fig. 2 shows a pump assembly 40 which has no accumulator provided as part thereof. The pump assembly 40 otherwise has the same components as the pump assembly 20 of Fig. 1, namely a pump 21, a one way valve 22 and pump controls 23. Instead of having an accumulator as part of the pump assembly, Fig. 2 has a flexible fluid connector (liquid transfer device) 42 connected to the outlet 26 of the pump assembly 40. The flexible fluid connector 42 has its own built in mechanism to accommodate volumetric changes in the system and it thus takes the place of both the accumulator 24 and the outlet flexible fluid connector 30 of Fig. 1. The flexible fluid connector 42 will be further described below. In Fig. 2, no flexible fluid connector is shown on the inlet side of the pump assembly 40. Instead, a direct connection is made to the water supply 41 (e.g. mains supply or tank).

The fluid connector (e.g. hose) 42 therefore acts as an accumulator, and an additional accumulator such as the accumulator shown in Fig. 1 is therefore not required to compensate for the change in the system volume. This allows the pump assembly 40 to have a smaller physical size and a lower cost.

Fig. 3 shows a liquid transfer device in the form of a flexible fluid connector hose 42. The hose 42 is an elongate tube with a liquid conduit passage 51 through the centre. At either end of the hose 42 are connectors 52, 53 (typically formed from metal such as brass). At least one of these connectors 52, 53 may be different from the connectors used on a standard flexible hose and designed to match the outlet connector of the pump assembly 40 (Fig. 2 or Fig. 5) so as to ensure that the hose 42 is attached to the pump assembly outlet 26 rather than the pump assembly inlet 25 when assembled.

The connector 52 in Fig. 3 has a gas valve 54 for pressurising the gas chamber(s) inside the hose 42. The hose 42 is covered with a metallic braided sheath 55 (partially illustrated for clarity) surrounding the outer rubber wall 56 of the liquid conduit and gas chambers.

Figs. 4a, 4b, 4c and 4d show four possible arrangements of liquid conduit 51 and gas chambers 57. Fig. 4a shows a central liquid conduit 51 surrounded by four gas chambers 57, each of which is in partial contact with the liquid conduit 51 and able to deform (compress) so as to accommodate volumetric changes such as expansion or contraction of the liquid in the liquid conduit 51. A single wall 59 surrounding the liquid conduit 51 forms four membranes 58 each separating the liquid conduit 51 from one of the gas chambers 57. Fig. 4b shows a single gas chamber 57 separated from the liquid conduit 51 by a single membrane 58. Fig. 4c shows an arrangement in which the gas chamber 57 is a completely separate hose 60 that runs inside the liquid conduit 51. In the embodiments of Figs. 4a and 4b, the metallic braided sheath 55 is shown surrounding the outer rubber walls of the hose 42 to provide additional strength and support against expansion. In the embodiment of Fig. 4c, no metallic braided sheath 55 is shown to illustrate that this embodiment could have a rigid outer wall (although it could equally be flexible and have a metallic braided sheath as in the other embodiments). Fig. 4d shows a closed cell foam structure 61 inserted inside the outer rubber tube 56 and forming a large number of small gas chambers 57 as closed cells, each filled with gas. The foam structure 61 is here formed as a tube shape, forming the liquid conduit 51 on the inside of that tube. The inner cell walls that form the inner diameter of that tube make up the flexible membrane that is in contact with the liquid in use. Under pressure, the foam cells are compressed and when pressure is reduced they expand, thereby adjusting the volume of the liquid conduit 51. The foam 61 has a natural shape to which it will return naturally when not under other forces.

It will be appreciated that alternative support structures may be used other than the braided metallic sheath, including non-metallic braided sheaths and non-braided sheaths (metallic or otherwise).

Fig. 5 is similar to Fig. 2, but instead of the direct connection to the mains 41, an inlet fluid connector 28 is used as in Fig. 1. The inlet flexible fluid connector 28 is of conventional design as the body of the pump 21 is isolated from the system pressure by a one way valve 22 and is able to vent to atmosphere via the fluid supply.

As the two fluid connectors 28, 42 may potentially be very similar in appearance (similar length and external appearance), but very different in functionality (one accommodates volume expansion while the other does not), the pump assembly 40 has different connectors on the inlet 25 and outlet 26. These may be different sized connectors (different diameters), different thread pitches (e.g. a non-standard thread), or different types of connector such as a threaded connector, a bayonet connector, a connector with a keyed feature, or a press-fit connector. The two fluid connectors 28 and 50 have at least one connector that matches the pump assembly connector to which it is to be attached (but will not fit the other pump assembly connector). This ensures that the fluid connectors 28, 50 are correctly installed with the volume expansion on the downstream end of the pump assembly 40 where it is required to accommodate the volume changes in the downstream pipework.

It will be appreciated that the configurations described above can be used for either single ended pumps ortwin ended pumps. They can also be used in either positive head or negative head applications.

Claims

1. A liquid transfer device comprising a liquid conduit with a liquid inlet at one end and a liquid outlet at an opposite end and a gas chamber adjacent to the liquid conduit and separated therefrom by a flexible membrane.

2. A liquid transfer device as claimed in claim 1, comprising a plurality of gas chambers each adjacent to the liquid conduit and separated therefrom by a flexible membrane.

3. A liquid transfer device as claimed in claim 2, wherein the plurality of gas chambers are fluidly interconnected.

4. A liquid transfer device as claimed in claim 1, 2 or 3, wherein the liquid conduit is a flexible tube at least partially surrounded by the or each gas chamber.

5. A liquid transfer device as claimed in any preceding claim, wherein the or each gas chamber extends substantially the length of the liquid conduit.

6. A liquid transfer device as claimed in any preceding claim, wherein a gas inlet is provided to permit pressurization of the or each gas chamber.

7. A liquid transfer device as claimed in claim 1, comprising a plurality of gas chambers, and wherein the plurality of gas chamber are formed as a closed cell foam.

8. A liquid transfer device as claimed in claim 7, wherein the closed cell foam comprises cell walls and wherein the flexible membrane is formed from the cell walls.

9. A liquid transfer device as claimed in any preceding claim, wherein the liquid conduit and the or each gas chamber are integrally formed from the same material.

10. A liquid transfer device as claimed in any preceding claim, wherein a flexible sheath surrounds the liquid conduit and the or each gas chamber.

11. A liquid transfer device as claimed in claim 10, wherein the sheath is resistant to expansion of the liquid conduit and the or each gas chamber.

12. A liquid transfer device as claimed in claim 10 or 11, wherein the sheath is a braided sheath.

13. A liquid transfer device as claimed in any preceding claim, wherein the liquid transfer device has a connector adjacent the liquid inlet specifically designed for connection to the output of a pump unit.

14. A pressurised liquid delivery system comprising: a pump; a non-return valve downstream of the pump; an inlet connector upstream of the pump; an outlet connector downstream of the non-return valve; and a liquid transfer device as claimed in any preceding claim, wherein the inlet connector and the outlet connector have different connection designs; and wherein a liquid transfer device inlet connector is designed to be attachable to the outlet connector and not attachable to the inlet connector.