GB2114714A - Flow regulator - Google Patents

Abstract

A constant flow valve particularly suitable for use with instantaneous electric water heaters has a fluted core (11) mounted on a spindle (10) which is axially moveable relative to a seating surface. An elastically deformable ring (13) surrounds the core. An annular member (19) is mounted and retained on the spindle at the end of the core adjacent the fluid inlet (23), the outer diameter of said member being such that with the core positioned relative to the elastically deformable ring so as to provide the minimum flow setting of the valve, the annular member controls the actual minimum flow, so that an accurately constructed core is unnecessary. <IMAGE>

Description

SPECIFICATION Fluid flow rate control device This invention relates to a fluid flow rate control device. It is particularly applicable to such devices used for the control of the flow rate of water entering an instantaneous electric water heater.

British Patent Specification No. 1 350 846 describes a fluid flow rate control device which permits a constant fluid flow rate irrespective of the fluid inlet pressure, the control being effected by the urging of an elastically deformable ring into grooves around a core, said grooves defining a passageway for the fluid flow. The contents of British Patent Specification No. 1 350 846 are hereby incorporated by reference. Such devices have been used to control the water flow rate in instantaneous electric water heaters, the core portion being made in the form of a plastics moulding with grooves in the form of fluting.In order to provide varying flow rates, the fluting on the core portion extends radialiy outwardly towards the inlet end of the device and the core is axially moveable relative to the seating surface so as to position the deformable ring at different locations along the length of the fluting.

The minimum flow rate through the device is determined by adjusting the axial movement of the core portion such that the elastically deformable ring is in contact with the fluted portion of the core at the inlet end of the core which has the largest diameter.

The Applicant has found that there are difficulties in achieving a predictable minimum flow rate in such devices. A predictable minimum flow rate is extremtly desirable in the case of the use of these devices in conjunction with instantaneous electric water heaters which have a fixed thermal input, since the temperature of the water at minimum flow rate can vary considerably from one heater to another if such minimum flow rate is not accurately determined.

The problem appears to arise in the manufacture of the fluted cores which are typically made of plastics material by an injection moulding process.

As well as there being difficulty in obtaining precisely accurately moulded fluting, it appears that there is also difficulty in making a core which has a bore for fitting onto a spindle which is completely concentric with the outer diameter of the flutings. Thus, if a device is intended to provide a minimum flow rate of one litre per minute, we have found that it is possible that individual devices may vary considerably in their minimum flow rate, and the flows may in fact be in excess of two litres per minutes. Such devices incorporated in instantaneous electric water heaters mean that at minimum flow, the anticipated maximum water temperature may be considerably reduced to an extent whereby the water provided is at an unsatisfactorily low temperature.

According to the present invention we provide a fluid flow rate control device as claimed in Claim 1 of British Patent Specification No. 1 350 846, in which the core portion has a profiled surface comprising fluting extending to, and increasing in overall diameter towards the end of the core adjacent the inlet means, said core being mounted on a spindle which is axially moveable relative to the seating surface, and wherein an annular member is mounted and retained on said spindle at the end of the core adjacent the inlet means, the inner diameter of said annular member providing a close fit with the surface of the spindle, and the outer diameter being such that with the core being positioned relative to the elastically deformable ring so as to provide the minimum flow setting of the device, the member controls the actual minimum flow.Typically this means that the outer diameter of the member is such that it extends to cover at least part of the troughs of the fluting of a perfectly circular crosssection core mounted symmetrically on the spindle.

Said annular member is preferably in the form of a plate and may be made of a plastics material such as Kematal or a metal such as brass or bronze. The member is preferably retained on the spindle by means of a nut, such as a hexagon stiff-nut, located on a threaded portion of the spindle. The spindle is typically made of brass and has an accurately machined or drawn circular surface such that the inner surface of the annular member fits closely around it.

One embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing, which shows a detail, partly in cross-section, of a fluid flow control device according to the invention in a substantially minimum flow position.

A brass spindle 10, of circular cross-section, loosely carries an annular moulded plastics core 11 located against a shoulder 12 on an extension of spindle 10. An elastically deformable ring 13 is shown in contact with the outer diameter of core 11, and an annular plastics moulding 14 provides a seating surface determining the position of the ring 1 3 relative to the position of core 1 The annular plastics moulding 14 is retained between a first portion 1 5 of a housing and a second portion 1 6 of the housing which in use are held together by conventional means (not shown) and a sealing ring 1 7 is fitted between the annular plastics moulding and the second portion 1 6 of the housing to provide a fluid-tight seal.

The core 11 is fluted along its axially extending outer surface, and the bottom of a pair of grooves is shown in dashed outline 1 8. The outer diameter of the core 11 increases towards its end distant from shoulder 12. An annular plate 19 is fitted closely over spindle 10 at the end of core 11 of large diameter and the plate 1 9 (and the core 11) is retained on the spindle by a stiff-nut 20.

The outer diameter of the plate 1 9 is such that it covers at least partly the grooves in a symmetrically mounted perfectly formed core 11.

In the minimum flow position of the device as illustrated, fluid can thus pass through the device only between the deformable ring 13 and the perimeter of annular plate 19.

The first portion 15 of the housing has outlets (not shown) to permit fluid to leave the grooves 18 as shown by arrow 21, and the second portion of the housing has an inlet 22 to permit fluid to reach the grooves 18 as shown by arrow 23.

The axial position of the core 11 relative to the deformable ring 13 can be altered by axial movement of the spindle to provide different flow rates through the device, and at all positions except that shown, the flow rate will be dependant on the passageway provided between the deformable ring 13 and the grooves 18 in core 11. As the movement between the deformable ring 1 3 and the core 11 reaches the position shown in the drawing it will be seen that the flow rate at the minimum flow position is determined by the passageway between the deformable ring 1 3 and the perimeter of annular plate 1 9. Thus, irrespective of the dimensional accuracy of the plastics core 11 and the depth of the grooves 18 at the larger diameter end of the core 11, and even if the core is slightly eccentric relative to the spindle 10, the minimum flow rate can be determined with accuracy by ensuring that the plate 1 9 accurately fits the spindle 10 and has the correct outer diameter. Because the plate is of simple shape such dimensional control is relatively easily established in its manufacture eg by machining or cutting or moulding.

Claims (6)

Claims

1. A fluid flow rate control device as claimed in Claim 1 of British Patent Specification No. 1 350 846, in which the core portion has a profiled surface comprising fluting extending to, and increasing in overall diameter towards the end of the core adjacent the inlet means, said core being mounted on a spindle which is axially moveable relative to the seating surface, and wherein an annular member is mounted and retained on said spindle at the end of the core adjacent the inlet means, the inner diameter of said annular member providing a close fit with the surface of the spindle, and the outer diameter being such that with the core being positioned relative to the elastically deformable ring so as to provide the minimum flow setting of the device, the member controls the actual minimum flow.

2. A fluid flow rate control device as claimed in Claim 1 in which the outer diameter of the member is such that the member extends to cover at least part of the troughs of the fluting of a perfectly circular cross-section core mounted symmetrically on the spindle.

3. A fluid flow rate control device as claimed in Claim 1 or Claim 2, wherein the annular member is in the form of a plate.

4. A fluid flow rate control device as claimed in any preceding claim wherein the member is retained on the spindle by means of a nut located on a threaded portion of the spindle.

5. A fluid flow rate control device as claimed in any preceding claim wherein the spindle has an accurately machined or drawn circular surface and the annular member fits closely around it.

6. A fluid flow rate control device as hereinbefore described with reference to and as shown in the accompanying drawing.