Valves and valve actuation – Fluid actuated or retarded – Pilot or servo type motor
Patent
1995-02-13
1998-02-10
Lee, Kevin
Valves and valve actuation
Fluid actuated or retarded
Pilot or servo type motor
251 38, 251 45, F16K 3104
Patent
active
057160384
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method and system for dispensing fluids, and to a sensor, transducer and proportional valve for use in such a system or with such a method.
To avoid the need to transport and store water, it is becoming common to dispense beverages, for example, by mixing a concentrate with water at the point of sale. However, the resultant beverages dispensed by the systems which are currently available are generally variable in quality. For example, if water and concentrate are dispensed from individual pipes, but at more than one location, the resultant pressure drops and viscosity variations change the water to concentrate volumetric ratio of the beverage being dispensed. In this respect, currently available mechanical means for controlling the flow of a liquid during a dispense cannot be made to react to changes in the pressure drop, viscosity or flow rate of the liquids.
It is an object of the present invention to provide a method and system for reliably dispensing fluids, which method and system reduces the disadvantages of the known systems. The invention also seeks to provide component parts for such a system.
According to a first aspect of the present invention, there is provided a piezoelectric sensor for a sonic transducer, the sensor comprising a housing defining an opening, a piezoelectric element comprising a piezoelectric film mounted to extend across the opening, electrically conductive regions contacting opposed surfaces of the piezoelectric film and overlying to define one area of the piezoelectric film at which the opposed conductive regions coincide, and means for making electrical connections to said conductive regions, wherein the means for making electrical connections comprises an electrically conductive post extending within the housing, an end surface of the post contacting one surface of the piezoelectric film at the one area thereof.
When electrical signals for example, electrical pulses are applied to the electrically conductive regions, it is only at the one area of the piezoelectric film that the pulse is applied across the thickness of the piezoelectric film. Accordingly, it is only at the one area that mechanical deformation takes place. A sensor of the invention is thereby able to output a sound wave from the one area only. Preferably, the sensor of the invention is arranged to output an ultrasonic waveform.
The electrically conductive post which is arranged to contact the one surface of the piezoelectric film acts to maximise the ultrasonic waves emitted.
The electrically conductive regions may be defined, for example, by electrically conductive films provided on opposing surfaces of the piezoelectric film. In this case, the end surface of the electrically conductive post contacts the electrically conductive film provided on the one surface of the piezoelectric film.
However, it is presently preferred that the end surface of the post directly contacts the one surface of the piezoelectric film and thus defines one of the electrically conductive regions. In this case, it is also presently preferred that the other electrically conductive region is defined by an electrically conductive film provided on the other surface of the piezoelectric film.
Any suitable piezoelectric film may be utilized.
In a preferred embodiment of the invention, it is preferred that the piezoelectric film be a film of polvinylidene fluoride (PVDF).
In a preferred embodiment the electrically conductive film is preferably a film of gold. Not only is gold conductive, it is also inert, and this latter property is clearly important if the sensor is to be used, for example, in a transducer to measure the properties of a beverage.
In an embodiment, the electrically conductive film is applied to the or each surface of the piezoelectric film by vapour deposition.
If electrically conductive film is applied to both surfaces of the piezoelectric film, one surface of the piezoelectric film may be entirely covered with the electrically conductive film except for a si
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Aztec Developments Limited
Lee Kevin
LandOfFree
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