AU2001270757A1 - Thermostatic mixing valve - Google Patents

Claims

1. A thermostatic mixing valve for operation over a range of fluid flow rates,

comprising housing parts and operating parts accommodated within an operating space defined by the housing parts, said operating parts including:

a valve member movable within the operating space so as to define first and second

valve ports respectively, said first valve port tending to open while the second valve

port is closing and vice versa, depending on the direction of movement of said valve

member; - inlet ducting for delivering first and second fluids at different temperatures to said

first and second valve ports respectively;

a mixing space within said operating space arranged to receive said fluids from the

valve ports and permit mixing thereof;

a temperature-sensitive actuator, at least a sensing part of the actuator being located

within a sensing space within said operating space, said sensing space being in

communication with both of said first and second valve ports thereby to receive the

mixture of fluids, said actuator being arranged to cause movement of the valve

member so as to counteract temperature changes of said fluid mixture; and

a discharge space downstream of said sensing space, wherein further valve means are provided responsive to demand for fluid at said discharge

space, so as to force the mixed fluid to flow via said sensing space in close proximity to said

sensing part of the actuator at times of low demand, while permitting a portion of said mixture to bypass said sensing space under conditions of high demand, thereby to permit an increased flow rate.

2. A thermostatic mixing valve as claimed in claim 1 wherein the further valve means is a pressure-responsive valve means, responsive to an increased pressure difference

between points upstream and downstream of the sensing space to open a conduit between

said points.

3. A thermostatic mixing valve as claimed in claim 1 or 2 wherein the further valve

means closes below a pressure drop and, therefore, flow rate for which fluid mixing within

the mixing space would be unable to take place efficiently.

4. A thermostatic mixing valve as claimed in any of claims 1 to 3 wherein the sensing

space and mixing space may be distinct, or is formed substantially as one space within the

housing.

5. A thermostatic mixing valve as claimed in any preceding claim wherein said operating space and operating parts are generally cylindrical and have rotational symmetry

about an axis of the valve.

6. A thermostatic mixing valve wherein the temperature-sensitive actuator is arranged

centrally, extending along said axis.

7. A thermostatic mixing valve as claimed in claim 6 or 7 wherein the valve member is

a cylindrical slide valve moving axially between first and second annular valves seats,

thereby to define said first and second valve ports as annular ports.

8. A thermostatic mixing valve as claimed in any of claims 5 to 7 wherein the inlet

ducting comprises an entry to one side of the valve axis, feeding into an annular gallery

space surrounding said valve ports.

9. A thermostatic mixing valve as claimed in any preceding claim wherein the valves

are spring loaded check valves which open completely once a certain pressure has been

reached

10. A thermostatic mixing valve as claimed in claims 1 to 9 wherein the valves are of a type which open gradually in response to a rise in pressure.

11. A thermostatic mixing valve as claimed in any preceding claim wherein the valves

are configured to be responsive to different pressure values such that they react in sequence

to changes in pressure.