GB2098399A - Fluid-flow sensitive switches - Google Patents

Abstract

A fluid flow sensitive switch comprises a fluid flow body 1 containing a member 6 movable in dependence upon the rate of fluid flow in the body 1, and an actuating member 16 which transmits movement from the movable member 6 to actuate a switch 19 located outside the body 1. A sealing membrane 17, which is illustrated as a flexible sac enveloping the actuating member 16, prevents contacts between the latter and the fluid within the body 1. The device is designed for use in the control of equipment such as domestic shower installations. <IMAGE>

Description

SPECIFICATION Fluid flow sensitive switches This invention relates to fluid flow sensitive switches. It is a requirement in, for example, domestic shower installations, that heating of the water in the installation shall not take place unless a minimum flow rate is established, and flow sensitive switches may be used to effect this control function.

According to the present invention, a fluid flow sensitive switch comprises a fluid flow body, a first member located within the body and movable in response to fluid flow through the body, a switch mechanism located outside the body, a switch actuating member operatively related to both the float and the switch mechanism, and a fluid-tight seal between the actuating member and the body which in use isolates the actuating member from the fluid within the body but permits it to move in response to movement of the first member thereby to actuate the switch mechanism.

Conveniently the actuating member comprises an elongated fulcrumed in an aperture in a closure member secured in an opening in the fluid flow body. The fluid-tight seal may then comprise a flexible sac fitting snugly around that part of the lever which projects into the fluid flow body to engage the first member. Preferably the sac is formed with a flange around its open end, which flange is secured between the closure member and the fluid flow body to provide a fluid-tight seal against the latter. Conveniently the lever is formed with shoulders which abut the closure member and form a positive stop to locate the lever correctly.

In one embodiment the first member is a float formed with a recess having a conical wall co-axial with its direction of movement under fluid flow, and the lever engages the conical wall for pivoting movement towards an axially aligned position as the float moves. In this embodiment the lever includes a tapering portion which engages the conical wall.

In another embodiment the lever is aligned approximately normally to the line of movement of the first member and engages a corresponding recess in the latter.

Where necessary resilient biasing means may be included to bias the first member towards the position it occupies under conditions of zero fluid flow.

The invention will now be explained in greater detail with reference to the accompanying drawings, of which: Figure 1 is a longitudinal section through a first embodiment of the invention, Figure 2 is a section taken on the line II--II of Figure 1, Figure 3 is a longitudinal section through a second embodiment of the invention, and Figure 4 is a section taken on the line IV--IV of Figure 3.

The first embodiment of the invention consists of an angle pattern body 1 having an inlet port 2, an outlet port 3 and a control port 4. The body is waisted at 5 adjacent the outlet port 3, and a float member 6 shouldered at 6a is located in the waisted portion with a slack fit. A gland 7 is secured over the control port 4 of a gland nut 8, sealing between the gland and the body being effected by an O-ring 9. A spring 10 acts between the underside of the gland and the shouldered end of the float to seat the shoulder against the rim formed by the waisted portion 5 of the body 1.

The generally cylindrical float 6 is formed with a co-axial recess 11 extending from its shouldered end, the blind end 1 a of the recess being of frusto-conical form.

The aperture through the gland 7 is closed by means of a plate 12 retained by a circlip 13 which seats in a groove 14 in the gland. The centre of the plate is formed with a rectangular perforation 1 5 accommodating a switch actuating lever 1 6. The lever is shouldered at 1 6a, the shoulders abutting the underside of the plate 12, so that the lever is fulcrummed on the plate, and can pivot about the line of the shoulders. A fluid-tight seal in the form of a sac 1 7 with a flange 1 7a around its open end serves to seal the body 1. The main body of the sac 1 7 closely surrounds the lever 1 6 where it projects through the plate 1 2 into the body 1, and the flange 1 7a is trapped between the plate 12 and the gland 7.A mounting bracket 18 secured on the gland serves to carry a microswitch 1 9 whose actuator 1 9a is actuable by the lever 1 6 as it pivots towards a position which is in alignment with the axis of the float 6. This pivoting movement of the lever 1 6 is effected in use by upward movement of the float (as seen in the drawing) caused by flow of fluid from the inlet port 2 to the outlet port 3. As the float rises with increasing flow, the conical surface of the bore 1 a in the float acts as a wedge to impart lateral movement to the lever. It will be noted that the inner end of the lever 1 6 is tapered so that it can engage fully home in the recess.If adjustment of the point at which the microswitch 1 9 trips is desired, then it is a simple matter either to provide a screw adjuster on the end of the lever 1 6, or to provide for adjustment of the position of the microswitch on its mounting bracket 1 8. These arrangements are only given by way of example, and are not specifically illustrated in the drawings.

The arrangement of the plate 12 and the sealing sac 1 7 has been found particularly advantageous in this embodiment of the invention since, apart from the very small clearance around the lever 16 in the perforation 1 5, the sac is fully supported against deformation by the static pressure of water in the body of the device, while the relatively small angular deflection of the lever 1 6 in use does not impose any undue distortion on the sac itself.

In use, the fluid flow body 1 may be connected in the supply pipework of a watered device, such as a domestic shower installation. The normallyopen contacts of the microswitch 1 9 are connected in series with the electrical heating circuits of the shower installation, so that with zero water flow through the installation it is impossible to energise the heating circuits. In this way protection against overheating is provided. As water begins to flow through the fluid flow body, the float 6 is moved against its spring and the wedge action of the conical recess begins to pivot the lever 16.Eventually, when the flow of water reaches a sufficient rate, the lever 1 6 will cause tripping of the switch, and the heating circuits will be energised, remaining so until the flow falls below the critical value, and the float is returned by the spring. This enables the heating to be stopped immediately, rather than continuing for a finite time as in the case of thermostatic safety devices which do not operate until a predetermined degree of over-heating has occurred.

In the embodiment illustrated in Figure 3 and Figure 4, the arrangement is that of a straightthrough fluid flow path, rather than the angle pattern of the first embodiment, although a similar fluid flow body 1' is used, having inlet, outlet and control ports 2', 3' and 4' respectively. The arrangement at the control port 4' is substantially identical with that of Figures 1 and 2, and identical references are to be found in Figures 3 and 4. No further description of this part of the second embodiment will be given here. The member 6' of the second embodiment, which corresponds to the float 6 referred to above, is in the form of a hollow cup, slotted to receive the free end of the lever 1 6, which will be seen to be of parallel-sided rather than tapered shape.The plan view of the slot in the member 6' is shown in the insert Figure 4, and it will be seen that the end of the lever is positively engaged in the slot The open end of the slot serves to permit fluid flow to the outlet port 3'. In this embodiment, the return bias on the member 6' is provided by the biasing arrangements of the microswitch itself. The operation of the second embodiment of the invention is analogous to that of the first, and will not be described further.

It will be appreciated from the foregoing description that if both types of device are to be manufactured, a single pattern of lever 1 6 could be used, if it were parallel sided with its free corners chamfered to fit the base of the conical recess in the first embodiment Further it is possible to actuate more than one microswitch, either two multiply the current-switching capacity of the device, in the case of simultaneous actuation, orto provide multi-stage control in the case of sequential actuation.

The sensitivity of the illustrated devices is such that they will switch at a water flow rate of 0.45 I/minute or less, the fluid flow body being a standard 15mum. fitting. It is to be stressed that the force which moves the members 6 and 6' in the embodiments is not that resulting from absolute static pressure, since leakage around the float would tend to equalise pressures, but in fact arises from the pressure differential created by the flow of fluid through the device.

Claims (10)

1. A fluid flow sensitive switch comprising a fluid flow body, a first member located within the body and movable in response to fluid flow through the body, a switch mechanism located outside the body, a switch actuating member operatively related to both the float and the switch mechanism, and a fluid-tight seal between the actuating member and the body which isolates the actuating member from the fluid within the body but permits it to move in response to movement of the first member thereby to actuate the switch mechanism.

2. A switch as claimed in Claim 1 in which the actuating member comprises an elongated lever which is fulcrummed in an aperture in a closure member secured in an opening in the fluid flow body.

3.A A switch as claimed in Claim 2 in which the fluid-tight seal comprises a flexible sac fitting snugly around that part of the lever which projects into the fluid flow body to engage the first member.

4. A switch as claimed in Claim 3 in which the sac is formed with a flange around its open end, which flange is secured between the closure member and the fluid flow body to provide a seal against the latter.

5. A switch as claimed in any one of Claims 2 to 4 in which the lever is formed with shoulders which abut the closure member and form a positive stop for correct location of the lever.

6. A switch as claimed in any one of Claims 1 to 5 in which the first member is formed with a conical wall portion co-axial with the direction of movement of the float under the influence of fluid flow, and the switch actuating member engages the conical wall portion for movement by the wedge-like action of the latter.

7. A switch as claimed in Claim 6 in which the conical wall portion is provided by a conical recess in the first member.

8. A switch as claimed in Claim 7 in which movement of the first member with increasing fluid flow through the body pivots the actuating member towards an axially aligned position

9. A switch as claimed in Claim 8 in which that end of the actuating member which engages the conical recess is tapered.

10. A switch as claimed in any one of Claims 1 to 5 in which the lever is aligned approximately normally to the line of movement of the first member and engages in a corresponding recess in the latter.