Measuring and testing – Fluid pressure gauge – Diaphragm
Patent
1991-01-11
1992-08-04
Woodiel, Donald O.
Measuring and testing
Fluid pressure gauge
Diaphragm
92 90, 200 83B, G01L 708
Patent
active
051348896
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a mechanical transducer which responds to a force which is applied to it in one direction to exert a force of a different magnitude in another direction.
It is a common requirement to control a large force by means of a small force, for example a motor car is brought to rest using a relatively light force applied to a foot brake pedal. It is also a common requirement to take a weak signal and generate sufficient force to operate signalling devices, for example a vane in an air duct can sense very slight air movements yet because of its size it can exert a sufficient force to operate a control switch e.g. in boilers and air conditioning apparatus. However, the necessary control in these examples requires amplifying systems of considerable size and complexity or, in the case of the air valve, lead to possible disturbances from vibration, overshoot or undershoot or time delay if significantly damped. If pistons and similar devices are used as buffers, dampers or actuators, the force-to-thrust ratio is determined by the bore size of the device: in order to contain or to generate large forces the area, and hence the diameter, has to be increased unless unacceptably high pressures are used. However, the increase in bore size, which increases the sensitivity to lower pressures, also results in a considerable increase in the inertia of the axially displaceable piston or cylinder, and this can impair the response and reaction of the apparatus to external shock and vibration forces. For example, a pressure switch (which comprises an electric switch operated by a pressure-sensitive actuator) may use a large circular diaphragm to generate a sufficient force from a low pressure on its surface to overcome the trip force on the switch (which may be a microswitch). This device has the disadvantage that the plane in which the diaphragm lies is perpendicular to the axis of displacement needed to operate the switch and therefore the volume required for the device is large. Also the mass of the diaphragm and other moving parts makes the device vulnerable to axial vibration and therefore to spurious operation.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a mechanical transducer which is able to overcome the problems noted above.
In accordance with this invention, there is provided a mechanical transducer, comprising a converter which comprises a plurality of elongate flexible elements joined together at their opposite ends and spaced at intervals around a longitudinal axis of the transducer, the opposite ends of the converter being displaceable towards and away from each other along said axis, which displacement is accompanied by a bowing or straightening of said elements, so that an axial force applied to said converter is converted to a radial force exerted by said elements, or a radial force applied to said elements is converted to an axial force.
It will be appreciated that the converter takes the general form of a rib cage. An axial force applied between the ends of the rib cage may be a pushing force or a pulling force, to cause the elements or ribs to bow radially outwards or radially inwards, or to straighten. The change in the volume enclosed by the rib cage is substantially greater than the volume displaced by the axially moving ends of the rib cage. A force applied to the ribs radially inwardly or outwardly, produces a substantially amplified axial force at the ends of the rib cage. This force amplification is particularly large as the ribs are deflected towards or away from their straight positions.
Preferably the converter or rib cage is provided at its ends with means for applying or delivering an axial or torsional force. The opposite ends of the rib cage may be linked, in order to apply or deliver the axial or torsional force, either around the outside of the rib cage or through the rib cage or both.
A resilient element may be disposed around the outside or within the rib cage or integrally therewith, and may serve to apply or ab
REFERENCES:
patent: 3479081 (1969-11-01), Schaaf
patent: 4123640 (1978-10-01), Ballantyne
Schindler Edwin D.
Woodiel Donald O.
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