GB2198883A - Flow-sensitive switch - Google Patents

Abstract

A flow-sensitive switch comprises a body 1 defining a flow chamber 2, a spout 11 mounted within the chamber 2 to leave a free space 12 around the spout 11, and a control member 14 arranged and guided for longitudinal movement within the chamber 2. Associated with the control member is a magnet 18 or other operating means to operate a proximity switch, preferably a magnetic reed switch. The control member 14 has a cup-shaped portion 16 fitting over the downstream end of the spout 11 and extending into the free space 12, to obturate the spout 11 under no-flow conditions, and arranged to move clear of the spout 11 at a given flow rate to move the magnet 18 by a distance defined by the overlapping lengths of the portion 16 and the spout 11 and operate the proximity switch. The magnet 18 is located at least partially in an axial extension of the cup-shaped portion 16 protruding into the spout 11 in the no-flow condition. The control member 14 has axially extending fins 15 to guide the control member in its axial movement and allow comparatively free flow past the control member 14. <IMAGE>

Description

FLOW-SENSITIVE SWITCH This invention relates to flow-sensitive switches.

Flow-sensitive switches are used in a number of applications, such as in shower installations, to switch in a pump, when flow is established, to boost the normally low domestic water pressure available. Another use is in the dispensing of carbonated beverages, where it is preferred to establish flow to prime a pump before switching it on to avoid excessive foaming. Other uses are to be found in the monitoring and control of process equipment.

A number of constructions of such switches exist in which a flow -sensitive control member moves in the flow stream in response to flow. This control member carries a permanent magnet which operates a magnetic reed switch as it moves between a "flow" and a "no-flow" position. In one such type of such switch, the flow is longitudinally through a chamber in which the control member itself moves longitudinally. The movement is such that the control member moves until a restricted flow path is opened to a maximum extent, so that the actual movement of the control member, which determines the operation of the reed switch, is closely defined. The reed switch may be located across the flow path or alongside it.

In such arrangements, it has been the normal construction for the chamber to have a zone of reduced width co-operable with a portion of the control member, which is moved longitudinally to clear the said portion from the said zone when sufficient flow is present and returns to the flow-restricting position as the flow ceases.

It has now been found that improved sensitivity, with a consequent lower pressure requirement, and predictability of movement, can be achieved with the control member comprising a cup-shaped element fitting over and co-operating with a spout.

Accordingly, the present invention consists in a flow-sensitive switch comprising a body defining a flow chamber, a spout mounted within the chamber to leave a free space around the spout, and a control member arranged and guided for longitudinal movement within the chamber, and having associated therewith means to operate a proximity switch, in which the control member has a cup-shaped portion fitting over the downstream end of the spout and extending into the said free space, to obturate the spout under no-flow conditions, and arranged to move clear of the spout at a given flow rate to operate the switch.

It is preferred that the operating means be a permanent magnet, and the proximity switch may then be a suitable form of magnetically operable proximity switch, in particular a magnetic reed switch. As an alternative to a magnet, the proximity switch may be operable by a source of heat, light or other radiation.

The magnet or other operating means may be located at least partially in an axial extension of the cup-shaped portion protruding into the spout in the no-flow condition. By this means, the required overall length of the control member is kept down.

The control member is conveniently provided with axially extending fins to co-operate with the wall of the chamber to guide the control member in its axial movement and allow comparatively free flow past the control member.

The outlet from the flow chamber may be at the end thereof remote from the spout, which acts as an inlet, or it may be in a wall of the chamber in the region of the spout, so that the flow, once established, does not need to pass the control member.

The reed or other proximity switch may be clamped to the outside of the body, or it may preferably be located in an integral lateral extension of the body.

The invention will be further described with reference to the accompanying drawings, in which: Figure 1 is an axial section of a form of switch in accordance with the invention; Figure 2 is a plan view of a control member; Figure 3 is a bottom plan view of a body for a somewhat modified form of switch; Figure 4 is a side view of the body of figure 3; Figure 5 is a partial section on the line V-V of figure 4; Figure 6 is a partial section on the line VI-VI of figure 4; and Figure 7 is a view similar to Figure 1 and showing a modification.

Turning first to figure 1, this shows a switch body 1 moulded in plastics material or a suitable metal and defining a flow chamber 2 between an inlet end 3 and an outlet end 4. The inlet is internally threaded at 5, and externally is of hexagonal form for application of a suitable spanner. The outlet end 4 is externally threaded at 7, so that the body may be inserted in pipework, eg between a low pressure water source and a shower head, or between a keg and a tap. Adjacent the enlarged inlet end, there is provided a locating shoulder 8 for a collar 9 on a separately moulded spout 11 which projects in a downstream direction to define a generally annular space 12 between itself and the adjacent wall of the body 1. Adjacent the outlet end 4, there is provided an inturned rim 13 forming a stop surface.

A cup-shaped moulded control member 14 (see also figure 2) is guided within the chamber 2 by means of integral fins 15, and at rest in a "no-flow" condition adopts the position of figure 1, in which it obturates the spout 11, with a skirt 16 (or body of the cup) extending into the annular space 12 until a base 17 of the inverted cup abuts the open end of the spout 11. The fins 15 extend axially beyond the base 17 of the cup.

In an axial zone, the control member 14 is formed with an internal cavity, which extends axially into the cup, is used to house a permanent magnet 18, and is closed by a plug 19. The magnet 18 co-operates with a magnetic proximity switch, such as a reed switch, mounted in or on the body 1, so that the state of the proximity switch is changed in dependence on the axial position of the magnet 18. The proximity switch may be mounted inside or outside the flow chamber 2, and a preferred location is in an integral lateral extension of the body 1, as will be described in more detail hereinafter with reference to figures 3 to 6.

In operation, the switch is installed in a flow line, and under "no-flow" conditions the spout is obturated as shown in figure 1, with the skirt 16 entering deeply into the annular space 12. As flow is initiated, normally by opening of a tap downstream of the switch 1, a small head of liquid will cause the control member to lift from the spout 11 to allow flow down the inside of the skirt 16 within the annular space and thence comparatively freely up the outside of the skirt 16 between the fins 15 and to the outlet end 4.

The restriction to flow presented by this serpentine path, and the light weight of the control member 14, mean that the latter will continue to rise with only a small head of liquid, until the liquid debouching from the spout can pass freely beneath the skirt 16 into the free space between the fins 15. This position is reached when the distal end of the skirt 16 rises to a level slightly above that of the endof the spout 11. This lifts the magnet 18 to a predetermined position in which its field will operate the proximity switch. Depending on the application, this will switch on a boost pump or perform such other function as may be desired in response to a detection of flow. Where a boost pump is used-, it will normally be located between the flow source (storage tank or keg) and the switch, and will have a bypass relief line.

On closing the tap, the flow will cease, and the control member 14 will revert to the figure 1 position. If necessary, the output from the boost pump may be bypassed until the pump is switched off.

Turning now to figures 3 to 6, these show an integrally moulded extension 21 of the body 1, to house the reed or other proximity switch. This extension 21 has a cavity 22 to locate the proximity switch close to the wall of the body, channels 23 for leads and locations 24 for terminals. Further channels 25 provide locations for external leads to emerge from the extension via a channel 26. Once the proximity switch is installed, the cavity and channels may be closed by a cap (not shown) secured using a screw hole 27.

It will be seen that by choice of the overlapping lengths of the spout 11 and the skirt 16, the movement of the control member 14 between "flow" and "no-fl ow" conditions can be closely controlled, enabling the switch to be readily adapted for various configurations, thus obviating the need for tuning by re -positioning the proximity switch after installation. As the spout 11 is a separately manufactured component, it may be made available in a range of lengths, as may the control member, to suit different applications.

Turning now to figure 7, this shows a structure very similar to figure 1, except that the outlet 4a has been moved from the end of the chamber 2 remote from the spout 11 to a position in a side wall of the chamber 2 in the region of the spout 11 and the control member 14, where it is associated with an externally threaded union 7a. It will be appreciated that with this arrangement, the flow from the spout 11 flows more directly to the outlet 4a, thus reducing pressure drop, particularly once the flow has been established and the control member 14 has moved to the "flow" position. The final stop position for the control member 14 is then formed by the closed end 13 of the chamber 2 acting as an abutment for the ends of the fins 15.In this arrangement, the union 7a may be arranged with its axis generally radial as illustrated in figure 7, or it may be inclined and/or tangential.

In order to prevent air from being trapped within the inlet switch 3 of the flow chamber 2, which may prevent the control member 14 from returning to the "non-flow" condition, a small bleed hole may be provided in the control member 14, preferably through the base 17 of the cup.

Various other modifications may be made within the scope of the invention, as defined in the appended claims.

Thus, the components may be cast, moulded, fabricated or otherwise formed in a wide variety of materials, depending on the final application, eg for use in a corrosive liquid or under hygienic food-processing conditions.

Also, the reed switch may be replaced by other forms of proximity switch operable by suitable operating means in the control member 14. For example, the magnet may be replaced by a source of radiation, such as heat or light, and the proximity switch would be sensitive to an increase, or decrease, in the incidence of such radiation. Other forms of magnetically operable proximity switch could also be used.

Claims (10)

1. A flow-sensitive switch comprising a body defining a flow chamber, a spout mounted within the chamber to leave a free space around the spout, and a control member arranged and guided for longitudinal movement within the chamber, and having associated therewith means to operate a proximity switch, in which the control member has a cup-shaped portion fitting over the downstream end of the spout and extending into the said free space, to obturate the spout under no-flow conditions, and arranged to move clear of the spout at a given flow rate to operate the switch in which the operating means is located at least partially in an axial extension of the cup-shaped portion protruding into the spout in the no-flow condition.

2. A flow-sensitive switch as claimed in claim 1, in which the operating means is a permanent magnet, and in which the proximity switch is magnetically operable.

3. A flow-sensitive switch as claimed in claim 2, in which the proximity switch is a magnetic reed switch.

4. A flow-sensitive switch as claimed in claim 1, in which the proximity switch is operable by a source of heat, light or other radiation.

5. A flow-sensitive switch as claimed in any of the preceding claims, in which the control member is provided with axially extending fins to co-operate with the wall of the chamber to guide the control member in its axial movement and allow comparatively free flow past the control member.

6. A flow-sensitive switch as claimed in any of the preceding claims, in which the outlet from the flow chamber is at the end thereof remote from the spout, which acts as an inlet.

7. A flow-sensitive switch as claimed in any of claims 1 to 5, in which the outlet from the flow chamber is in a wall of the chamber in the region of the spout, so that the flow, once established, does not need to pass the control member.

8. A flow-sensitive switch as claimed in any of the preceding claims, in which the proximity switch is clamped to the outside of the body.

9. A flow-sensitive switch as claimed in any of claims 1 to 7, in which the proximity switch is located in an integral lateral extension of the body.

10. A flow-sensitive switch substantially as hereinbefore described with reference to the accompanying drawings.