GB2341660A

GB2341660A - Flow control device

Info

Publication number: GB2341660A
Application number: GB9820364A
Authority: GB
Inventors: Robert Meadows; Neil James Baxter; Nicholas John Beck
Original assignee: Kohler Mira Ltd
Current assignee: Kohler Mira Ltd
Priority date: 1998-09-19
Filing date: 1998-09-19
Publication date: 2000-03-22
Anticipated expiration: 2018-09-19
Also published as: GB2341660B; GB9820364D0

Abstract

A flow control device for adjustable selection of flow rate comprises two regulators (figure 1. 1,1') of the type in which a core member 5,5' has a profiled or fluted outer surface co-operable with a surrounding ring member 4,4' to define orifices for fluid flow with the core members 5,5' being axially movable relative to the ring members 4,4' to vary the number or size of the orifices for controlling the flow rate. At a given flow setting, the ring members 4,4' are elastically deformable to adjust the size of the orifices to compensate for variations in fluid pressure so as to maintain the selected flow rate substantially constant. One of the ring members 4 is made of softer elastomeric material than the other ring member 4' resulting in the regulators (figure 1. 1,1') being operable over different pressure ranges to maintain a constant flow rate. The device is preferably for use with an instantaneous water heater. The ring members may be circular, D-shaped or trapezoidal and more than two regulators may be included in one device.

Description

2341660 FLOW CONTROL DEVICE This invention concerns improvements in or

relating to flow control devices for controlling the flow rate of a fluid and in particular to flow control devices for maintainin, a substantially constant flow rate over a range of g fluid pressures.

Such flow control devices are commonly used in instantaneous water heaters of the type in which water is heated as it flows through a heat exchanger to I provide a source of hot water on demand for washing or showering.

In such instantaneous water heaters, the user adjusts the flow rate to control the water temperature for a given heat energy input to the heat exchanger and the flow control device maintains a selected water temperature substantially constant by automatically compensating for pressure changes in the water supply to keep the flow rate for the selected water temperature constant.

Water supply pressures can vary widely and this can cause problems for accurate control of water temperature in instantaneous water heaters if the supply pressure varies outside the operating range of the flow control device.

It is an object of the present invention to provide a flow control device for maintainino, constant a selected flow rate over a wide range of fluid t) pressures which is of simple construction and reliable in use.

According to the present invention we provide a flow control device comprising a first flow regulator operable to maintain constant a selected flow rate over a lower part of a range of fluid pressures and a second flow 2 regulator operable to maintain constant the selected flow rate over a higher part of the range of fluid pressures.

By providincy two regulators operable over different ranges of fluid I= I a) pressures, the flow control device may be operable over a wider range of fluid pressures.

Advantageously, the first regulator responds to variations in the fluid pressure below a pre-determined pressure and the second regulator responds to variations in the fluid pressure above the pre-determined pressure.

Preferably, each regulator comprises an elastic ring member surrounding a I core member having a plurality of longitudinally extending grooves co I operable with the ring member to define orifices for fluid flow with relative axial movement of the ring member and core member adjusting the flow rate.

Advantageously, the ring member of the regulator operable over the lower part of the range of fluid pressures is made of softer elastomeric material than the ring member of the regulator operable over the higher part of the range of fluid pressures.

Preferably, the ring member of softer material is radially deformable to vary the size of the orifices defined with the grooves of the associated core member to maintain the selected flow rate substantially constant over the lower part of the range of fluid pressures and the ring member of harder material is radially deformable to vary the size of the orifices defined with the grooves of the associated core member to maintain the selected flow rate substantially constant over the higher part of the range of fluid pressures.

Features, benefits and advantages of the invention will now be described in more detail, by way of example only, with reference to the accompanying drawing wherein:- Figure I is a part section through a flow control device embodying the invention, and Fi gures 2,3 and 4 are sections showing the regulators of the control device depicted in Figure I at low, medium and high pressures. 10 The flow- control device shown in the drawings has two regulators 1, P for controlling flow from an inlet chamber 2 -to an outlet chamber 3.

Each regulator [J' comprises a ring member 4,4' of circular section such as 15 an 0-ring surrounding a cylindrical core member 5,5' having longitudinal 1P grooves 6,6' in the outer surface which define with the ring member 4,4' a plurality of orifices 7,7' for fluid flow.

In this embodiment, there are nine grooves 6 in the core member 5 and eighteen grooves 6' in the core member 5'. It will be understood, however, that the number and shape of the grooves 6,6' in each core member 5,5' may be varied from that shown.

The core members 5,5' are provided by a piston 8 which threadably engages a sleeve 9 having a spindle 10 for mounting a control knob (not shown) by means of which the sleeve 9 can be rotated to reciprocate the piston 8 and move the core members 5,5' axially relative to the associated ring member 4A.

4 The grooves 6,6' in each core member 5,5' are of different lenorth and of C. I uniform cross-section throughout the length so that axial movement of the core members 5,5' varies the number of orifices 7,7' that are open and hence adjusts the flow rate. 5 In an alternative arrangement (not shown), the grooves 6,6' in each core 1 ing cross-se 1 members 5,5' are of the same length and of increas' S. ct'on from one end so that axial movement of the core members 5,5' varies the size of the orifices 7,7' that are open and hence adjusts the flow rate.

The drive connection between the piston 8 and sleeve 9 is a multi-start thread I I with one thread blanked so that it can be assembled in one place only to ensure correct assembly.

The ring members 4,4' are made of elastomeric material of different hardness selected so that the regulators 1, V are operable at different supply pressures to maintain a selected flow rate substantially constant.

In this embodiment, the regulator I with the ring member 4 of softer material is operable at supply pressures in the range 0.5 to 1.5 bar and the regulator V with the ring member 4' of harder material is operable at supply pressures above 1.5 bar.

The effect of the supply pressure on the ring members 4,4' -is shown in Figures 2,31 and 4. More particularly, at supply pressures in the range 0. 5 to 1.5 bar, the ring member 4' of harder material is not significantly affected by changes in the supply pressure, and the ring member 4 of softer material is radially deformable to vary the cross-section of the orifices 7 defined with the grooves 6 of the core member 5 to compensate for pressure changes and maintain the selected flow rate substantially constant.

At supply pressures above 1.5 bar, the ring member 4 of softer material i z:' I is deformed to close completely the grooves 6 of the core member 5 preventing flow, and the ring member 4' of harder material is radially deformable to vary the cross-section of the orifices 7' defined with the grooves 6' of the core member 5' to compensate for pressure changes and maintain the selected flow rate substantially constant.

Downstream of the ring members 4,4', divergent flow passages 12,12' are provided to reduce the cavitation and hence the noise as the water flows through the orifices 7,7'.

As will be appreciated, the invented flow control device having two regulators operable at different pressures can maintain a selected flow rate substantially constant over a wide range of supply pressures. This is of particular benefit for application of the invented flow control device to instantaneous electric or gas water heaters in which water is heated as it flows through a heat exchanger, for example to provide a source of hot water for washing or showering. For a given input of heat energy to the heat exchanger, the water temperature is controlled by adjusting the flow rate and the invented flow control device is operable to maintain a selected water temperature substantially constant by compensating for changes in the water supply pressure to keep the flow rate for the selected water temperature constant. Other applications of the invented flow control device where it is desirable to maintain a constant flow rate will be apparent to those skilled in the art.

It will be understood that the invention is not limited to the embodiment above-de scribed. For example, two or more regulators may be combined to operate over any desired range of supply pressures.

6 The ring 0:1 g members may be made of any suitable elastomeric material havin, a hardness tailored to maintain constant a selected flow rate over any desired range of supply pressures as required for a particular application. The ring members may be of circular or other suitable section, for example a Dsection or a trapezoidal section may be employed.

i

Claims

7 CLAIMS

1 A flow control device comprising a first flow regulator operable to maintain constant a selected flow rate over a lower part of a range of fluid pressures and a second flow regulator operable to maintain constant the selected flow rate over a higher part of the range of fluid pressures.

2. A flow control device according to claim I wherein the first regulator responds to variations in the fluid pressure below a pre- determined pressure and the second regulator responds to variations in the fluid pressure above the pre-determined pressure.

3. A flow control device according to claim 1 or claim 2 wherein each regulator comprises a core member having an outer surface profile cooperable with a surrounding ring member to define orifices for fluid flow.

4. A flow control device according to claim 3 wherein the core member of each regulator is axially movable relative to the associated ring member for adjusting the flow rate.

5. A flow control device according to claim 4 wherein the core members are arranged for simultaneous axial movement relative to the associated ring member.

6. A flow control device according to claim 5 wherein the core members are connected to a common drive member.

7. A flow control device according to any one of claims 3 to 6 wherein relative axial movement of each core member and associated ring 8 member varies the number of orifices that are open to adjust the flow rate.

8. A flow control device according to any one of claims 3 to 6 wherein relative axial movement of each core member and associated ring member varies the size of the orifices that are open to adjust the flow rate.

9. A flow control device according to any one of claims 3 to 8 wherein the ring member of the regulator operable over the lower part of the range of fluid pressures is made of softer elastomeric material than the ring member of the regulator operable over the higher part of the range of fluid pressures.

10. A flow control device according to- claim 9 wherein the ring member of softer material is radially deformable to vary the size of the orifices defined with the associated core member to maintain the selected flow rate substantially constant over the lower part of the range of fluid pressures, and the ring member of harder material is radially deformable to vary the size of the orifices defined with the associated core member to maintain the selected flow rate substantially constant over the higher part of the range of fluid pressures.

11. A flow control device according to claim 10 wherein the ring member of softer elastomeric material is radially deformable to close completely the orifices defined with the associated core member over the higher part of the range of fluid pressures.

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12. A flow control device according to claim 10 wherein the ring member of harder material is unaffected by changes in fluid pressure over the lower part of the range of fluid pressures.

13. A flow control device according to any one of claims 3 to 12 wherein each core member has axially extending formations in the outer surface which co-operate with the associated ring member to define the orifices for fluid flow.

14. A flow control device according to claim 13 wherein the formations comprise grooves.

15. A flow control device according to any one of claims 3 to 14 wherein each ring member comprises an 0-ring.

16. A flow control device according to any one of claims 3 to 15 wherein each ring member is of circular, D- or trapezoidal section.

17. A flow control device according to any one of the preceding claims wherein the first flow regulator is operable at fluid pressures in the range 0.5 to 1.5 bar and the second flow regulator is operable at fluid pressures above 1.5 bar.

18. A flow control device according to any one of the preceding claims wherein a divergent flow passage is provided downstream of each ring member.

19. A flow control device substantially as hereinbefore described with reference to the accompanying drawings.

20. An instantaneous water heater provided with a flow control device according to any one of the preceding claims.