AUTOMATIC LIOUID VALVEThe invention relates to automatic liquid valves.
The invention relates more particularly to thermally sensitive automatic valves particularly for use in various appliances. It is known to have valves controlled by metal or other materials elements that change generally in response to temperature. Normally, automatic valves that rely directly on changes relating temperature open and close relatively slowly and valves that use, say, a tripping mechanism will only open or only close automatically as the case may be. Further, as the temperature sensing is normally dependent on liquid adjacent the valve, the sensing can be inhibited by local air-locks in the appliance.
It is an object of the invention to overcome or at least reduce these problems.
According to the invention, there is provided an automatic thermally responsive in-line liquid valve comprising a hollow housing through which liquid can flow, a movable buoyant closure member arranged to be lifted by the liquid in one direction to close off the valve, and an activator comprising a coiled shaped memory alloy element mounted in the housing arranged to move the closure member in an opposite direction and to open the valve when the temperature of the liquid rises above a predetermined magnitude.
A valve seating for the closure member may be provided at a down-stream end of the housing and the housing is arranged to fill with liquid before it is completely lifted up to close the valve.
The valve seating may comprise an 0being held in the housing.
The closure member may comprise a cylindrical boss provided with a nose that forms a sealing element for the valve.
The closure member may have a shaft extending through the housing from the boss to an apertured base.
The activator may be supported at one end by the apertured base.
The closure member may be arranged to be lifted up beyond its closed position to open the valve in the event of an excessive pressure occurring up-stream of the valve.
The closure member may include a nose and an O-ring may be mounted to the housing to cooperate with the nose to normally close off the valve, the arrangement being such that the excessive pressure forces the nose through and beyond the O-ring to open the valve.
An automatic thermally sensitive in-line water valve for a coffee making machine according to the invention will now be described by way of example with reference to the accompanying drawings in which :Figure 1 is a schematic diagram of part of the coffee making machine incorporating the valveFigures 2 to 5 show cross-sectional views of the valve in different operative positions.
Referring to the drawings, in Figure 1 a water heater 10 comprising a water channel surrounded by concealed electrical heating elements is used to heat water from a reservoir (not shown) which passes through a one way valve 11 to the heater 10. Heated water is supplied in use to the automatic thermally sensitive valve 12 and beyond to be flowed or dripped over a coffee granules in a container (not shown) in a normal fashion in a coffee making machine. Various rubber connections 13 and hoses 14 are shown in the Figure 1.
For normal use in making coffee, it is desirable to prevent cold water reaching the coffee granule container, as would occur if water is allowed to be "pumped" by the heater 10 as soon as the heater is first turned on.
Clearly, what then happens is that the water beyond the heater and water first heated reaches the container at a relatively low temperature because either the water has not been heated at all or the water has given up its heat on its way to the container. The described thermally sensitive valve therefore serves, in a manner as described below, in effect to delay the first supply of water to the container to allow and ensure that the first water delivered to the container is at a satisfactory high temperature.
In Figures 2 to 5, the valve comprises a hollow housing 15 through which the water can flow. A movable water-buoyant member 16 is mounted to slide in an apertured base 17 between relative remote positions shown in Figures 2 and 4. The base 17 fits within the housing 15 and is relatively movable thereto. A valve activator 18 consists of a coiled shape memory alloy element that fits on the base 17 and extends to an O-ring 19 mounted in a downstream end of the housing 15.
The member 16 has a cylindrical boss 20 at one end with supporting a nose 21. The nose forms a valve seating to cooperate with the O-ring 19 to close off the valve. The activator 18 is responsive to changes in temperature and in this example is shown in its position fully compressed at 850C or below in Figures 2 and 3. The activator 18 is fully extended at 950C or above as shown in Figure 4.
Generally stated and in normal use, the valve will therefore remain fully closed until the temperature of activator 18 rises to above 850C and be quickly and fully opened shortly thereafter to allow full flow of hot water to the coffee granule container from the heater 10.
In Figure 2, the valve is shown in an operative position when the activator 18 is at a temperature below 850C and when there is no water up-stream of the valve. The member 16 is supported by the base 17 with the nose 21 well clear of the O-ring 19 so that the valve is fully open.
In Figure 3, the valve is closed, the member 16 has been lifted by water up-stream of the valve and now filling the housing 15. Any air up-stream of the valve ahead of the water has been expelled through the valve so that the housing 15 could fill with water. The valve will remain fully closed until the temperature of the activator 18 rises above 850C.
Figure 4 shows an operative position of the valve at temperatures above 850C where the activator 18 has expanded to press the base 17 down so that the nose 21 is pulled down, that is in an opposite direction to the buoyancy force on the member 16, away from the O-ring 19 so that the valve is open.
Figure 5 shows an operative position of the valve where the water pressure up-stream of the valve has reached an excessive high value and the member 16 has been forced upwards by the excessive pressure. The forces developed by the excessive pressure is sufficient to press the nose 21 completely through and beyond the O-ring 19 so that the valve opens to release the excessive pressure and possibly prevent an explosion or water burst elsewhere in the coffee making machine.
The described valve may be used for other applications, including automatic control of flow of a coolant or lubricant in a cooling or lubricating system respectively.