CA1185656A - Piezoelectric device for generating and storing electrical energy - Google Patents

Abstract

Abstract:
An electric current generator comprises a mechanical energy source (F), a mechano-electric converter (1) including a piezoelectric crystal (2) and a load circuit connected to the electrodes of this converter. The load circuit comprises in series a condenser (3), a rectifier (4) and a point spark gap (5), a consumer circuit (7) being connected to the terminals of the condenser. The circuit permits the charging of a condenser of relatively large capacity to voltages sufficient for supplying, for example, a relatively complex electronic circuit, or for triggering a detonator.

Description

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The present invention relates to an el~ctric current generator energised by mechanical energy, and including a mechano-electxic converter using a piezoelectric crystal and an electric load circuit connected to the electrodes of th~s converter. According to the present invention, the load circuit comprises in series a condenser, a rectifier and a needle or point spark gap, a consumer circuit being con-nected to the terminals of the condenser.

An object of the invention is to provide a current generator which is independent of a battery or other external electrical energy source, and which consequently avoids the disadvantages connected with the usual supply arrangements. More particularly, in the case of generators that are required to operate after a relatively long period of storage or inactivity or in the case of arrangements in which the effective life, the cost, the weight or the bulkiness of a battery represent a serious inconvenience, the present invention provides an extremely useful solution. Thus, the invention may especially be applied to an arrangement for triggering the primer of an explosive device, to the supply for an electronic circuit, such as a logic circuit, or to the supply for a portable electron.ic apparatus which is subject to isolated or repeated mechanical actions, such as shock, acceleration or decelerati.on, according to the case of application.

The invention will be better understood in the light of the following description, illustrated by the accompanying drawing, in which one embodiment of an electric current generator according to the invention is illustrated by way

- 2 of example.

The single figure of the drawing shows diagrammatically a piezoelectric crystal 2 contained in a capsule 1 which is capable of being subjected to the force F of a mechanical energy source. Connected in series with the piezoelectric crystal are a condenser 3, a diode 4 and a point spark gap 5. Another diode 6 is connected in parallel with the piezo-electric crystal 2 and ~he spark gap 5. A consumer circuit 7 is connected in parallel with the condenser 3.

10The piezoelectric crystal may be of a conventional type, such as described, for example, in the book "Piezoelectric ceramics" t edited by J. van Randeraat et al., N.V. Philips' Gloeilampenfabrieken, Eindhoven, 2nd edition lg74, for an ignition device (chapter 3, pages 23 to 39).

15According to the invention, the series connection of the point spa:rk gap 5 and the condenser 3, in combination with the diodes 4 and 6, permits a voltage of a few volts up to several tens of volts to be obtained at the condenser 3 according to the capacity. In certain constructional examples, capacities of 20 ~F were used for obtaining a voltage of 10 V, or capacities of 0.1 ,uF for obtaining a voltage of 140 V; in other words, a quantity of energy of about lmJ was accumulated.

The spark gap ~ plays an essential part in this arrangement, because it is not possible, star-ting with a piezoelectric crystal, directly to char~e a condenser of relatively large capacity to voltages sufficient for the supply, *or example, of a relatively complex electronic circuit.

The diodes 4 and 6 permit the condenser to be charged

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by positive and nega-tive current impulses.

The consumer circuit 7 may, for example, be a high-impedance electronic circuit or, in one particular case, the primer of a detonation device or any other appropriate circuit.

The excitation of the piezoelectric crystal 2 may, for example, result from an isolated shock for trigerring a detonator or result from an accelerated or decelerated movement of a mobile carrier of the generator. For example, the generator may be mounted on a projectile and control a safety device, or it may be carried by a person or be mounted on a vehicle.

In all the cases where it is used, the electrical energy source has an indefinite effective life and presents a very high degree of safety in operation.

Claims (2)

Claims:

1. An electric current generator comprising a mechano-electric converter including a piezoelectric crystal, and, connected to the electrodes of the converter, a load circuit which comprises the series connection of a storage condenser, a rectifier and a point spark gap, one terminal of said spark gap being connected to one of said electrodes of said converter, and the terminals of the condenser being the output terminals of the generator for connection of a consumer circuit.

2. An electric current generator according to claim 1, including a two-phase rectifying arrangement.