U.S. Philips Corporation

Other

Kees Dijkstra

Jan Huizinga

Bernard P Videc

Andreas J Garenfeld

A mechanical spring with negative spring stiffness adapted for use in an electroacoustic transducer unit for reducing the transducer resonant frequency. The mechanical spring with negative spring stiffness comprises two blade springs having both ends coupled to each other and which, under the influence of a compressive force F which acts in a direction along an imaginary line through both ends of the mechanical spring, are each bent in one of two opposite directions.

Mechanical spring having negative spring stiffness useful in an

A heat pump, in which there is arranged in a circuit between an absorber (7) and a generator (1) a liquid pump (9) comprising a piston (35) which is displaceable in a cylinder (33) and forms the separation between a gas chamber (37) and a liquid chamber (39) in which simultaneously prevails a pressure of comparatively low level during the suction stroke and a pressure of comparatively high level during the delivery stroke. A guide member (47) secured to the cylinder (33) encloses with the piston (35) an auxiliary chamber (51) of variable volume in which liquid of comparatively low pressure at least during the delivery stroke is constantly present. The gas chamber (37) is connected to alternately a lead of low and high gas pressure (69 and 71, respectively) in the heat pump, while the liquid chamber (39) is connected synchronously therewith alternately to a lead of low and high pressure (11a and 11b, respectively) in the heat pump. The heat pump provides an attractive solution especially for domestic heating for pumping liquid solution between the generator and the absorber because of the low-noise and low-energy liquid pump driven by means of pressure differences in the heat pump itself.

Heat pump comprising a thermally driven liquid pump and liquid pump for

An electroacoustic transducer unit comprises an electroacoustic transducer with a diaphragm (1), a magnet system (2) with an air gap (3), and a voice-coil former (4) with a voice coil (5) arranged in the air gap (3) of the magnet system. The transducer unit comprises means for reducing the transducer resonant frequency including mechanical springs with negative spring stiffness each coupled between a stationary part of the transducer unit and a movable part, for example the voice-coil former or the diaphragm of the transducer (FIG. 1b). The transducer unit further comprises a control device (42) which generates a control signal for correcting the position of the diaphragm. The mechanical spring with negative spring stiffness comprises two blade springs with both ends coupled to each other and which, under the influence of a compressive force F which acts in a direction along an imaginary line through both ends of the mechanical spring, are each bent in one of two opposite directions.

Electroacoustic transducer unit with reduced resonant frequency and

A thermodynamic oscillator having a displacer (5) and a piston (3) (further displacer) movable due to pressure fluctuations at the resonance frequency of the oscillator. The displacer (5) and the piston (3) are located in a working space (11, 15) which is filled with working medium and can be connected through a release valve (51, 125, 167) and a supply valve (53, 129, 169), respectively, to simple reservoir (55) filled upon working medium with an increase and a decrease, respectively, of the ambient temperature with respect to a nominal temperature. The valves (51, 53, 125, 129, 167, 169) have an opening pressure which is a function of the ambient temperature. The average pressure and the resonance frequency of the oscillator can thus be stabilized at a variable ambient temperature. The oscillator can be operated as a cold-gas engine, a hot-gas engine (motor), a heat pump or a current generator.

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Eindhoven, Netherlands

Kees Dijkstra