Contractile unit having a position sensor means

1. A contractile unit comprising a contractile hose extending between two spaced head pieces and adapted to perform a longitudinal contraction on being subjected to internal pressure, and a position sensor means responsive to the distance between the head pieces, which possesses a microwave generator arranged on one of the head pieces and adapted to emit microwaves into the interior space of the contractile unit, an evaluating means being provided responsive to the distance between the head pieces, by transit time measurement, by phase comparison of the emitted and reflected wave or by determination of the resonant frequency, the contractile hose comprising at least one of electrically conductive particles, electrically conductive strand elements, and wires.

2. The contractile unit as set forth in claim 1 , wherein the microwave generator is also adapted to function as a microwave receiver.

3. The contractile unit as set forth in claim 1 , wherein the evaluating means comprises means for phase comparison of the emitted microwave signal and the reflected microwave signal and for phase difference determination as a measure of the distance.

4. The contractile unit as set forth in claim 1 , wherein the evaluating means is provided with a frequency generator for variably setting the microwave frequency and in that a resonance detector is provided responsive to the resonant frequency.

5. The contractile unit as set forth in claim 4 , wherein the frequency generator is provided in the form of a ramp frequency generator and on detection of the resonant frequency by the resonance detector the present frequency is held as a measure for the distance.

6. The contractile unit as set forth in claim 5 , wherein a frequency reducer is provided for the evaluation of the resonant frequency in the evaluating means.

7. The contractile unit as set forth in claim 1 , wherein the microwave generator is designed in the form of at least one of a coupled probe and a detector diode transmitting and receiving microwaves.

8. The contractile unit as set forth in claim 1 , wherein the microwave generator is designed in the form of a cavity resonator with a resonance space open toward the opposite head piece.

9. The contractile unit as set forth in claim 2 , wherein the evaluating means comprises means for phase comparison of the emitted microwave signal and the reflected microwave signal and for phase difference determination as a measure of the distance.

10. The contractile unit as set forth in claim 2 , wherein the evaluating means is provided with a frequency generator for variably setting the microwave frequency and in that a resonance detector is provided responsive to the resonant frequency.