US 4,288,793 AGranted

Apparatus containing a cylinder with a displaceable piston therein and a measuring transducer arranged essentially within the cylinder

AssigneeRotovolumetric AG

InventorBernhard Lotscher

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Abstract

An apparatus containing a cylinder with a piston displaceably guided therein and positionally adjustable by a hydraulic fluid medium. A capacitive measuring transducer is arranged in the cylinder. The measuring transducer comprises a tube attached at the piston and arranged in a longitudinal opening thereof. The tube is electrically conductively connected with the cylinder. Apart from the tube, the measuring transducer further comprises a rod protruding into the tube and insulatingly secured at the cylinder. This rod is connected by means of an electrical bushing or lead with the input of an electronic unit attached externally at the cylinder. The electronic unit comprises an oscillator having a connection electrically coupled with the cylinder and a connection coupled with the non-inverting input of a capacitive feedback differential amplifier. The inverting input of the differential amplifier is electrically connected with the rod which is secured so as to be electrically insulated at the cylinder.

Claims9

Dependent claims

The combination of:

a cylinder;
a piston displaceably guided therein and positionally adjustable by the action of a hydraulic fluid medium;
said piston being provided with a longitudinal opening;
a capacitive measuring transducer arrranged essentially in said cylinder;
said measuring transducer having two parts;
one of said parts of the measuring transducer being secured at said cylinder and extending into the longitudinal opening of said piston;
the other of said parts of said measuring transducer being secured to the piston;
said cylinder and said piston each having metallic parts;
one of the parts of the measuring transducer comprises a metallic, electrically conductive member and an insulating sheath which is adjacent to the other part of said measuring transducer and forms therewith a sliding seat extending over substantially the total length over which said two parts overlap each other;
the other part of said measuring transducer being provided with an electrical connection leading out of the cylinder and being electrically insulated with respect to the cylinder and the piston;
the part of the measuring transducer secured to the cylinder is provided with said connection which is electrically insulated with respect to the cylinder and the piston;
the part of the measuring transducer secured to the cylinder comprises an electrically conductive rod having an insulating sheath;
an electrically conductive tube arranged in the longitudinal opening of the piston and electrically conductively connected at the piston;
said rod protrudes into said tube;
said tube has an outer surface;
said longitudinal opening of the piston having an inner surface;
a free intermediate space being present between the outer surface of the tube and the inner surface of the longitudinal opening of the piston at least at that longitudinal section of the tube into which the rod protrudes;
and
said tube consists of resiliently flexible material so that it is automatically centered by the rod.

16 more elements

The combination of:

a cylinder;
a piston displaceably guided therein and positionally adjustable by the action of a hydraulic fluid medium;
said piston being provided with a longitudinal opening;
a capacitive measuring transducer arranged essentially in said cylinder;
said measuring transducer having two parts;
one of said parts of the measuring transducer being secured at said cylinder and extending into the longitudinal opening of said piston;
the other of said parts of said measuring transducer being secured to the piston;
said cylinder and said piston each having metallic parts;
one of the parts of the measuring transducer comprises a metallic, electrically conductive member and an insulating sheath which is adjacent to the other part of said measuring transducer and forms therewith a sliding seat extending over substantially the total length over which said two parts overlap each other;
the other part of said measuring transducer being provided with an electrical connection leading out of the cylinder and being electrically insulated with respect to the cylinder and the piston;
an electronic unit arranged externally of the cylinder;
said electronic unit comprising:
an oscillator for producing an alternating current voltage;
a capacitive feedback differential amplifier having an inverting input and a non-inverting input;
said inverting input being connected with the part of the measuring transducer which is electrically insulated with respect to said cylinder;
said oscillator having an output;
said non-inverting input of said differential amplifier being connected with the output of said oscillator;
and
said oscillator having a connection which is electrically connected by parts of the cylinder and piston with the part of the measuring transducer which is conductively connected with the cylinder.

16 more elements

An apparatus containing a cylinder, a displaceable piston provided with a longitudinal opening and being displaceable in the cylinder by means of a flow medium, a capacitive measuring transducer arranged essentially in the cylinder, which measuring transducer contains two mutually displaceable electrically conductive parts, of which the first is secured at the cylinder and extends into the longitudinal opening of the piston and the second part is connected with the piston and from which the second part protrudes into the lengthwise opening of the first, wherein the first measuring transducer part is electrically conductively connected with metallic parts of the cylinder and piston and the second measuring transducer part is electrically insulated in relation to the cylinder and the piston as well as guided, by means of an electrical connection out of the cylinder, wherein said second measuring transducer part is provided at its surface confronting the first measuring transducer part with an electrically insulating sleeve, which, together with said first measuring transducer part forms a sliding seat, and the lengthwise opening of said first measuring transducer part into which said second measuring transducer parts protrudes, is connected by at least one through passage, thus allowing pressure equalization with the inner space of the cylinder.

Dependencies are inferred from the claim text.