GB2098703A - Improvements in or relating to fluid flow control valve assemblies and devices incorporating such assemblies - Google Patents

Abstract

A fluid-flow control valve assembly comprises a valve head (7), Figure 1, that co-operates with a valve seating (5) to control fluid flow from a maximum down to a predetermined minimum. The valve head (7) has a number of axial passageways that permit fluid flow at the predetermined minimum value when the valve head (7) is seated upon the seating (5). Fluid flow through the passageways is controlled by a second valve (9). The second valve (9) may be mounted upon a control member (11) separated from that (6) on which the first valve head (7) is mounted, or it may be mounted upon the same control member (as in Figure 4). The control valve may form part of a gas flow control assembly for a gas- fired, water heater. <IMAGE>

Description

SPECIFICATION Improvements in or relating to fluid flow control valve assemblies and devices incorporating such assemblies This invention relates to fluid flow control valve assemblies and particularly to valve assemblies for controlling the flow of gases and liquids. The invention has especial but not exclusive reference to control valve assemblies for use with gas-fired equipment for example gas-fired water heaters.

It is frequently required to be able to adjust the flow of gaseous fuel along a conduit from a maximum to zero either in a controlled continuous manner or in a controlled step-wise fashion. Such a form of control has previously been excercised by means of a valve with a valve head so contoured that as the head moves towards and away from a valve seat the required control is provided. The head may have a continuously-variable movement or it may be movable in predetermined steps to give the stepwise control. However, it is found that as the valve head approaches the seat control over gaseous fuel flow becomes erratic and imprecise.

It is an object of the present invention to provide a fluid flow control valve assembly less prone to such disadvantages.

According to the present invention, a fluid flow control valve assembly comprises an inlet and an outlet, a valve seat positioned between the inlet and the outlet, a first valve head adapted to coach with the valve seat to control the fluid flow to said outlet, one or more passageways through said first valve head to permit fluid flow from the inlet to the outlet when said first valve head is closed on said seat, and a further valve head movable relatively to said first valve head to control fluid flow through the passageway or passageways.

One particularform of assembly embodying the invention comprises an inlet and an outlet a valve seat positioned between the inlet and the outlet, a first valve head adapted to co-operate with said seat to control fluid flow to said outlet, a valve head operating member on which said first valve head is mounted in such manner as to be movable relatively to said member, one or more passageways through said first valve head permitting flow from the inlet to the outlet when said first valve head is closed on said valve seat, a further valve head also mounted upon said operating member and movable thereby towards and away from said first valve head to control fluid flow through the passageway or passageways.

The further valve head may be movable relatively to said operating member, movement of the latter being transmitted to the further valve head via resilient means operatively connected to said further valve head and to said operating member.

By way of example only, embodiments of the invention will now be described in greater detail with reference to the accompanying drawings of which: Figure 1 is a schematic view of a first embodiment, Figure 2 is a rear elevation of a component of the first embodiment, Figures 3A and 3B are explanatory graphs, Figure 4 is a schematic view of a second embodiment, and Figure 5 is a schematic view of a gas/water control section embodying the invention and suitable for use with a gas-fired water heater.

Figure 1 illustrates an embodiment of the invention for controlling gaseous fuel blow from an inlet conduit 1 to an outlet conduit 2 via an interconnecting chamber 3 containing a flow control valve 4.

The flow control valve co-operates with a valve seat 5 and comprises a control rod 6 to one end of which is secured a first valve head 7 of generally disc-like form. The upstream (in the direction of gas glow) face of head 7 is contoured to form a seating surface that cooperates with the seat 5. The downstream face of the valve has a central recess within a peripheral wall 8 which forms a seat for a second valve head 9 also of generally disc-like form. Valve head 7 has a plurality of axial passageways 10 through it aligned with the longitudinal axis of the head.

Valve head 9 is secured to one end of a control member in the form of a tube 11 within which rod 6 is positioned. A seal 12 secured to the upstream face of valve head 9 co-operates with wall 8 in a manner to be described below.

Rod 6 and tube 11 are operatively connected to a control (now shown) by means of which they are movable axially independently of one another of a controlled predetermined manner. For example, the ends of the rod 6 and tube 11 remote from the respective valve heads 7 and 9 may be in contact with cam surfaces movement of which effects the desired axial movement of the rod 6 and tube 11.

In use, movement of valve head 7 towards seating 5 effects a progressive reduction in the flow rate from inlet conduit 1 to outlet conduit 2 until the valve head 7 contacts the seat 5 when the flow rate is determined by the total cross-sectional area of the passageways 10.

To effect a further reduction in flow rate, valve head 9 is advanced towards valve head 7 until a point is reached at which seal 12 contacts peripheral wall 8 and flow from inlet 1 to outlet 2 ceases.

It will be appreciated that variation in the flow rate will, for a particular configuration of valve head, be determined by the contours of the cam surfaces responsible for the movement of the rod 6 and tube 11. In general, at the point in the travel of valve head 7 atwhich control overflow would otherwise become imprecise, the valve head contacts seat 5 and flow is determined by the total cross-sectional area of the passageways 10. Flow control is then exercised by the second valve head 9. At the moment that valve head 7 contacts seat 5, the second head 9 is some distance from head 7 and a more precise control by valve head 9 of the now lower gas flow rate is possible.

This is illustrated by Figures 3A and 3B. Figure 3A shows the relationship between flow and valve head movement towards a seat in the case where a single contoured valve head is used. As can be seen, there is a rapid reduction in flow for a very small movement of the valve head as the latter approaches its seat and this gives rise to the imprecision referred to above.

On the other hand, as illustrated in Figure 3B, a flow control valve embodying the invention, and in which the passageways 10 are sized to permit 50% of maximum gas flow when the first valve head 7 contacts seat 5, a more accurate control of gas flow is possible at flow rates below the 50% rate.

It may be necessary, in the embodiment shown in Figure 1 to locate a spring between the valve heads 7 and 9 to ensure the separation of these components until movement of head 9 is required. Such a spring is shown in Figure 1 and referenced 13.

It will be appreciated that valve head 9 could be formed with passageways similar passageways 10 but sized to permit say 15% of maximum flow rate, and a further valve head fitted to control flow through the passageways in head 9. Afurther member to impart movement to the further valve head would also be needed.

It is not essential to employ separate operating members, i.e. rods and tubes to impart movement to the valve heads, a common operating member carrying the valve heads could be used and Figure 4 illustrates an emblodimentwith a single operating rod.

Figure 4 shows a configuration generally similar to that shown in Figure 2. An inlet conduit 1 communicates via chamber 3 with an outlet conduit 2, flow being controlled by a valve assembly comprising an operating rod 14 at one end of which is mounted a first valve head 15 of generally disc-like shape and whose upstream face is contoured to form a peripheral ledge 16 on which a sealing washer 17 is mounted. Washer 17 coacts with a valve seat 5.

Valve head 15 is free to move relatively to rod 14 away from the adjacent end thereof which has a stop either integral with the rod or provided by a circlip or similar component.

The first valve head 15 has a peripheral wall 18 on its downstream face which forms a seating surface for a washer 19 positioned on a ledge 20 formed on the upstream face of a second valve head 21 mounted upon the rod 14. Valve head 15 also has a series of axial passageways 10.

The valve heads 15 and 20 are maintained in the positions shown in Figure 4 by means of a helical spring 22 disposed between the heads and which urges valve head 15 into contact with the stop at the adjacent end of the rod 14.

The rod 14 and the valve heads 15 and 20 carried thereby is movable axially by some suitable mechanism for example a cam surface (not shown).

In use, axial movement of rod 14 to the right as seen in Figure 4 brings valve head 15 incrasingly closer to seat 5 so reducing flow through inlet conduit 2. In due course, washer 17 contacts seat 5 and then flow through conduit 2 is determined by the total cross-sectional area of the passageways 10.

If now, movement to the right of rod 14 is continued, the rod 14 moves relatively to the first valve head 15 compressing the spring 22 and bringing the second valve head 21 increasingly closer to the first valve head 15. This latter movement gradually reduces flow through the passageways 10 until washer 19 engages wall 18 when flow ceases.

The flow/rod movement relationship of the construction shown in Figure 4 is similar to that shown in Figure 3B.

It will be appreciated that the central bosses on the upstream faces of the valve heads 15 and 20 left as a result of the formation of the peripheral ledges 16 and 20 respectively assist in locating valve head 15 with respect to the seating 5 and valve head 21 with respect to the wall 18 in the downstream face of valve head 15.

In some circumstances, the rod 14 may be required to operate other componenets and greater axial movement than is permitted by the construction described in the preceding paragraph is needed.

In such a case, the second valve head 21 may also be capable of movement relatively to rod 14 being urged into the Figure 4 position by a second helical spring 23 located between head 21 and a stop 24 fixed to the rod 14. Thus, rod 14 can continue movement to the right even after washer 19 seats on wall 18.

Figure 5 shows an embodiment of the invention in which use is made of the movement of rod 14to operate the electromagnetic valve of a flame failure device in the gas/water control section of a gas-fired water heater.

In Figure 5, the flow of gaseous fuel from an inlet 25 to outlet 26 joined to a main fuel burner (not shown) is controlled first by an electromagneticallyoperated valve 27 of a flame failure device incorporating a thermocouple junction 28 exposed to the heat of the flame of a pilot burner 29. Control over that fuel flow continues with valve 30 whose construction is similar to that of the valve assembly shown in Figure 4 and with a further valve 31 operable by a flexible diaphragm 32 via a link rod 33.

Diaphragm 32 is flexed to the left (as seen in Figure 5) as water flows through the heater in response to the pressure difference set up between the mouth and throat of a venturi 34 in the water flow path between inlet 35 and outlet 36 leading to the heat exchanger of the water heater.

The venturi 34 is in parallel with a by-pass passage 37 flow through which is controlled by a water flow valve 38.

Figure 5 also shows a piezo-electric igniter shown diagrammatically at 39 and whose spark electrode 40 is located adjacent the orifice of the pilot burner 29.

A user operated control knob 41 movable both axially and rotationally in a mounting 42 operates igniter 39, gas valve assembly 30 and water flow valve 38 in the following manner.

Initiaily, the movable parts are in the positions shown in Figure 5. Valves 27 and 31 are shut as is water flow control valve 38.

To bring the heater into use, knob 41 is first moved axially in the direction indicated by arrowhead 43 against spring biassing means (not shown). That movement excites the piezo-electric igniter and moves rod 14 axially thereby shutting valve assembly 30 and lifting valve 27 off its seating so permitting gas to flow to the pilot burner (but not the main burner) where it is ignited by sparks struck between electrode 40 and the pilot burner 29. The knob 41 is held for a few seconds in the position just described to allow the themocouple to develop sufficient voltage to allow the valve 27 to be retained in its open position by the associated electromagnet. The knob 41 can thus be released allowing valve 30 to open to an extent determined by rotary movement of knob 41, axial movement then being imparted to the rod 14 by a cam surface 44 on knob 41.

A second cam surface 45 on the knob 41 determines the degree of opening of valve 38.

Water flow through the heater now results, in the well known manner, in the opening of valve 31, the flow of gaseous fuel to the main burner, where the fuel is ignited by the adjacent pilot burner flame and the heating of the water.

By rotation of the control knob 41 the user is able to control the flow of gas by means of valve assembly 30 and the flow of water through the heater by means of valve 38.

A main gas flow control valve (not shown) is provided to shut down the heater completely when required. Closure of the main valve terminates gas flow to the pilot burner 29 after which deenergisation of the electromagnet allows valve 27 to shut.

Claims (8)

1. Afluid control valve assembly comprising an inlet and an outlet, a valve seat positioned between the inlet and the outlet, a first valve head adapted to coact with the valve seat to control fluid flow to said outlet, one or more passageways through said first valve head to permit fluid flow from the inlet to the outlet when said first valve head is closed on said seat, and a further valve head movable relatively to said first valve head to control fluid flow through the passageway or passageways.

2. Afluid flow control valve assembly comprising an inlet and an outlet a valve seat positioned between the inlet and the outlet, a first valve head adapted to co-operate with said seat to control fluid flow to said outlet, a valve head operating member on which said first valve head is mounted in such manner as to be movable relatively to said member, one or more passageways through said first valve head permitting flow from the inlet to the outlet when said first valve head is closed on said valve seat, a further valve head also mounted upon said operating member and movabletherebytowards and away from said first valve head to control fluid flow through the passageway or passageways.

3. Afluid flow control valve assembly as claimed in claim 2 in which the further valve head is movable relatively to said operating member, movement of the latter being transmitted to the further valve head via resilient means operatively connected to said further valve head and to said operating member.

4. A fluid flow control valve assembly as claimed in claim 1 in which said first and further valve heads are mounted upon separate valve head operating members.

5. Afluid flow control valve assembly as claimed in any one of claims 1-4 and further comprising resilient means located between the heads to bias them apart.

6. A fluid flow control valve assembly as claimed in any one of the preceding claims in which there is a plurality of passageways in said first valve head arranged concentrically with respect to the longitudinal axis of said first valve head.

7. A fluid flow control valve assembly as claimed in claim 6 in which said first valve head is of disc-like form having a face with a peripheral wall adapted to form a seating surface for a coacting surface on said further valve head.

8. A gas-fired water heater substantially as herein described with reference to and as illustrated by Figure 5 ofthe accompanying drawings.

8. A fluid flow control valve assembly as claimed in claim 7 in which said first valve head has a face with a peripheral ledge and a seating washer located on the ledge.

9. A fluid flow control valve assembly as claimed in claim 8 in which the further valve head has a peripheral ledge and a seating washer located on the ledge, said latter seating washer forming said coacting surface.

10. A gas-fired appliance incorporating a flow control valve assembly as claimed in any one of the preceding claims for controlling flow of gaseous fuel to a burner of the appliance.

11. A flame failure device incorporating a flow control valve assembly as claimed in claim 2 or claim 3 and any one of claims 5-9, a pilot burner connected to said inlet upstream of said seating, an electromagnetically-operaable valve also located upstream of said seating and of said pilot burner connection and energised by a thermocouple unit responsive to the presence of a flame at said pilot burner, and in which movement of said operating member beyond a position in which flow through said passageway or passageways is prevented by said further valve head opens said electromatically-operable valve to permit flow of gaseous flel to said pilot burner only.

12. A gas/water control unit for a gas-fired water heater comprising a flow control valve assembly as claimed in any one of the claims 1-10 and further comprising control means for actuating said first and second valve heads and a flow control valve for controlling the flow of water through the heater.

13. A control unit as claimed in claim 12 and further comprising a flame failure device as claimed in claim 11 in which said actuating means controls movement of said operating member.

14. Afluid flow control valve assembly substantially as herein described with reference to and as illustrated by Figures 1 and 3 or Figures 2 and 3 of the accompanying drawings.

15. Aflame failure device substantially as herein described with reference to and as illustrated by Figure 5 of the accompanying drawings.

16. A gas/water control unit for a gas-fired water heater substantially as herein described with reference to and as illustrated by Figure 5 of the accompanying drawings.

New claims or amendments to claims filed on 8 July 1982 Superseded claims 1-16 New or amended claims:

1. A fluid flow control valve assembly comprising a fluid flow conduit having an inlet and an outlet, a first valve seat in the conduit and a first valve head co-operable with the first seat to control fluid flow towards the outlet, a second valve seat in the conduit downstream of the first seat, a second valve head co-operable with the second seat, an operating member on which the second valve head is mounted in such manner as to be movable by the member towards and away from the second seat, one or more passageways through the second valve head permitting fluid flow towards the outlet when the second valve head is closed on the second valve seat, a third valve head also mounted upon the operating member and movable thereby towards and away from the second valve head to control fluid flow through the passageway or passageways and in which the arrangement is such that movement of the operating member in a first direction moves the second valve head towards and then into contact with the second valve seat and then the third valve head towards and then into contact with the second head to close the passageway or passageways, continued movement of the operating member in the same direction then moving the first valve head in a direction away from the first seat, subsequent movement of the operating member in the opposite direction producing a reversal of the operating sequence of the first, second and third valves.

2. A gas-fired appliance including an assembly as claimed in claim 1 for controlling the flow of gaseous fuel to a gas burner connected to the outlet.

3. A gas-fired appliance as claimed in claim 2 and further comprising a pilot burner for said gas burner, a gas flow conduit connected to the pilot burner and to the fluid flow conduit at a point between the first and second seats, and means responsive to the presence of a flame at the pilot burner to hold the first valve head away from the first seat against resilient bias means biassing the first valve towards the first seat.

4. A gas-fired appliance as claimed in claim 3 in which the responsive means comprises an electromagnet energised by a thermocouple unit positioned so as to respond to the presence of the pilot burner flame.

5. A gas-fired appliance as claimed in claim 3 or 4 for heating water and including a flow control valve for adjusting the flow of water through the appliance, the operating member being linked to the valve to adjust the flow.

6. A fluid flow control valve assembly substantially as herein described with reference to Figures 2, 3B and 4.

7. A gas-fired appliance including a fluid flow control valve assembly as claimed in any one of claims 1-4 and 6.