GB2214271A - Fluid flow control means - Google Patents

Abstract

A fluid flow control means comprises a rigid housing 10 traversed by a flexible tube 12. Cam means include at least one rotatable cam member (16) which has a periphery which is circular over an arc of substantially 180 DEG and is formed with a channel (24) to engage the tube, the channel changing from a semi-circular to a flat section so as variably to compress the tube. There may be two meshing opposed members (16), and they may incorporate an elongated dimple (Figs 7 and 8) to reduce edge pinching of the tube. <IMAGE>

Description

Title Improvements in Fluid Flow Control Taps Field of the invention This invention relates to a fluid flow control tap.

Background to the invention Currently, fluid flow control taps operable between fully on and fully off positions principally fall into two categories, namely the gate valve and the non-return jumper or poppet valve. Each type has specific applications and advantages. Disadvantageously, however, both types of tap require a multiplicity of parts made of relatively costly materials. These parts are subject to wear and are often difficult or tedious to replace. In addition, these known types of tap are subject to corrosion and leakage through drying out of glands.

It is an object of this invention to provide an improved fluid flow control tap which avoids or minimises the disadvantages of the known types of tap in many fields of application.

The invention A fluid flow control tap in accordance with the invention comprises a rigid housing traversed by a flexible pipe for carrying the fluid flow, and an operable cam means mounted within the housing and which is rotatable variably to compress the flexible pipe from an open condition to a closed condition, wherein the cam means comprises at least one cam member having a periphery which is circular over an arc of substantially 180 degrees or more, the or each cam member being rotatable about the axis of its circularly formed peripheral arc, and the peripheral face of the or each cam member around said circular arc is formed with a channel which is generally of semi-circular cross-section at one end of the arc gradually reducing in depth to become effectively flat at the other end, the said peripheral face or faces of the cam or cam members bearing on the flexible tube so that said tube has a fully open cross-section for fluid flow at one end of the range of rotational operation of the cam or cam members and is gradually compressed to a fully closed cross-section at the other end of said range of operation.

The tap may include one or two cam members as aforesaid.

In the former case, the flexible pipe is compressed against the wall of the housing; in the latter case it is compressed between the two cam members. In both cases, it is a feature of the tap that, at the one end of the operational range, the flexible tube assumes its natural cross-section, thus enabling full fluid flow in the fully open condition of the tap.

When two cam members are employed, the circularly arcuate peripheral portions may be formed, on a rim on at least one side of the aforesaid channel, with meshing teeth, so that a drive applied to one cam member also results in matching rotation of the other cam members.

In general, a single operating cam member is to be preferred for flexible pipes of relatively small diameter, say less than 15 mm, whilst two cam members may be preferred for flexible pipes of relatively large diameter, say 10 mm or more up to 50 mm. The circular arc of the channel of the or each cam member may extend substantially up to 360 degrees where finer control of intermediate flows is required. In all instances, the gradation in shape of the channel is preferably matched to the naturally assumed shape of the flexible pipe at the differing degrees of compression. This is readily achieved, since the cam member may be moulded of suitable hard plastics material, conveniently integrally with a spindle by which the cam member is mounted for rotation in the rigid housing.The said housing may also be moulded of plastics material, and a flexible plastics material may also be used for the flexible pipe. Examples are, for the housing, a rigid plastics material such as polystyrene; for the flexible pipe, a flexible plastics material such as nylon; and for the cam unit, a material such as PVC coated with Teflon (Trade Mark).

If necessary, friction between the cam member(s) and the flexible pipe can be reduced by indenting the interior of the peripheral channel of the cam(s) with an elongate dimple of increasing size.

Operation of the cam member(s) may be by means of a simple hand lever, which may be detachable. However, it is also practicable for the tap to be motor driven, possibly through suitable gearing, and/or be controlled by a temperature sensor such as a bimetallic strip, for example to control fluid flow in a central heating system. A tap in accordance with the invention, controlled via a bimetallic strip, can also be useful as a radiator valve.

Yet again, two single cam devices may be mounted to operate 180 degrees out of phase on two separate parallel flexible pipes sandwiched between 180 degrees opposite regions of the cooperating surfaces of the respective cam members and the housing, thus providing for mixing of two fluids, e.g. hot water and cold water for a shower or mixer outlets.

Connection of the tap housing to the fluid supply can be by means of conventional compression joints. The flexible pipe traversing the housing will be internally connected to connectors which protrude through the housing wall. Because the flexible pipe is fully open to fluid flow when the tap is fully opened, it will sometimes be possible to use bore feeds of smaller diameter than is usual, for example 6 mm copper feed pipe instead of the 10 mm pipe which is necesssary because of restricted flow, even in the fully opened condition, of the conventional taps hitherto referred to.

Description of embodiments A fluid flow control tap in accordance with the invention will now be described by way of example with reference to the accompanying drawings, in which: Figures 1 to 4 are perspective external views of three possible embodiments of the tap; Figure 5 is a side view of the embodiment of Figure 4, showing the interior of the tap; Figure 6 shows a cam member; and Figures 7 and 8 diagrammatically show possible modifications in a double cam device and in a single cam device, respectively.

Referring to the drawings, Figure 1 shows a single cam action stopcock when open; Figure 2 shows a single cam action bibcock, when half open; Figure 3 shows the single cam action bibcock, when closed; and Figure 4 shows a double cam action bibcock, when half open.

All the above-mentioned embodiments of tap operate on the same principle, which is for convenience exemplified in Figure 5 with reference to the double cam action bibcock of Figure 4.

The tap shown in Figure 5 comprises an outer housing 10 of rigid plastics material such as polystyrene, traversed by a flexible pipe 12 of flexible plastics material such as nylon. The pipe 12 extends internally between connectors 14 on opposite sides of the housing, which connectors also provide for the external connection of bore feeds by means of conventional compression joints.

Two inter-engaging cam units are also mounted within the housing, each comprising a cam member 16 integrally moulded, for example of PVC coated with PTFE, with a spindle 18. One such spindle detachably receives a hand lever 20 for manual operation of the tap. The first driven cam member 16 in turn drives the other by virtue of intermeshing teeth 22 formed around the peripheries of the respective cam members, as will be clear from the enlarged view of one such cam member shown in Figure 6.

Between rims on which the teeth 22 are formed, each cam member 16 is formed on its peripheral face, over a circular arc of about 180 degrees, with a channel 24 which has a semi-circular cross-section 26 at one end diminishing to a substantial flat shallow depression 28 at the other end, passing through an increasing half-oval cross sectional shape between the two ends of the arc.

Figure 5 shows the manner in which the two cam members 16 are mounted within the housing. In the fully opened condition of the tap shown in Figure 5, the two semicircular end regions 26 of the channels form a circular passage through which the flexible pipe 12 passes without compression, so that its entire natural cross-section is open for fluid flow.

It will be appreciated, however, that when the lever 20 is operated, the cam members 16 are rotated in opposite senses gradually to reduce the size of the cross-sectional passage between them, increasingly compressing the flexible pipe 12, until at the other end of the operating range the regions 28 of the cam members are brought together and compress the flexible pipe into a completely closed condition, thereby fully to shut off the flow of fluid.

The single action stopcocks or bibcocks of Figures 1, 2 and 3 operate in analogous manner, but only one cam member is incorporated because the flexible pipe is compressed between the cam member and the outer housing. It will also be understood that, with a single cam action, the cam member does not require peripheral teeth.

It will be noted that, in the illustrated embodiments, the driven spindle turns in a slot 30 rather than a circular bearing. Therefore as the cam member(s) rotates, the spindle, and thus the attached driving handle, are able to travel along said slot 30 in order to reduce strain at the upstream compression joint between the pipe 12 and the incoming bore feed.

Figure 7 shows a modification of a double cam device wherein the peripheral channel of one cam member has an elongate round dimple of increasing size in order to reduce edge pinching of the flexible pipe in the closed position. A full turn action is preferred for pipe diameters greater than 18 mm.

Figure 8 shows a modification of a single cam device, in which the cam channel is analogously dimpled to reduce lateral wear, especially for flexible pipes in the range 12 to 25 mm diameter.

Various modifications of the above-described and illustrated embodiments are possible within the scope of the invention.

Claims (18)

CLAIMS:

1. A fluid flow control tap comprising a rigid housing traversed by a flexible tube or pipe for carrying the fluid flow, and an operable cam means mounted within the housing and which is rotatable to compress the flexible pipe variably from an open condition to a closed condition, wherein the cam means comprises at least one cam member having a periphery which is circular over an arc of substantially 180 degrees, the cam member being rotatable about the axis of its circular peripheral arc, and said periphery being formed with a channel which is generally of semi-circular cross-section at one end and gradually reducing in depth to become effectively flat at the other end, said periphery bearing on the flexible tube so that said tube has a fully open cross-section for fluid flow at one end of the range of rotational operation of the cam means and is gradually compressed to a fully closed cross-section at the other end of said range of operation.

2. A tap as claimed in claim 1 in which said cam means comprises a single cam member, and the housing has a wall against which the flexible pipe is compressible by the cam member.

3. A tap as claimed in claim 1 in which said cam means comprises two cam members between which said pipe is compressible.

4. A tap as claimed in claim 3 in which each said circular periphery is formed on at least one side of said channel with meshing teeth, so that a drive applied to one cam member also results in matching rotation of the other cam member.

5. A tap as claimed in any one preceding claim in which the circular arc of said channel of the cam member extends substantially up to 360 degrees to enable fine control of intermediate flows.

6. A tap as claimed in any one preceding claim in which the gradation in shape of the channel is matched to the naturally assumed shape of said flexible tube at the differing degrees of compression.

7. A tap as claimed in any one preceding claim in which said channel has a bottom profile incorporating an elongate dimple, in order to reduce edge pinching of said flexible tube in its fully closed cross-section.

8. A tap as claimed in any one preceding claim further comprising a spindle by which the cam member is mounted for rotation in said rigid housing.

9. A tap as claimed in claim 8 in which said spindle is integral with said cam member.

10. A tap as claimed in claim 9 in which said spindle and cam member are formed of a hard plastics material such as PVC coated with PTFE.

11. A tap as claimed in any previous claim in which the housing is made of a rigid plastics material such as polystyrene.

12. A tap as claimed in any previous claim in which the flexible tube is made of nylon.

13. A tap as claimed in any previous claim in which the cam member is operated by a hand lever which is detachable.

14. A tap as claimed in any one of claims 1 to 12 in which the cam member is driven by a motor controlled by a temperature sensor.

15. A tap as claimed in any one preceding claim, and further comprising two single cam devices mounted to operate 180 degrees out of phase on two separate parallel flexible tubes sandwiched between 180 degrees opposite regions of the cooperating surfaces of the respective cam members and the cam housing, thus to provide for mixing of two fluids.

16. A tap as claimed in any one preceding claim in which said housing is connected to the fluid supply by means of compression joints.

17. A tap as claimed in any one preceding claim in which the flexible tube traversing said housing is internally connected to connectors which protrude through the housing wall.

18. A tap as substantially herein described with reference to, and as shown in, the accompanying drawings.