Piezoelectric generator operated by fluid flow

• US 4,005,319 A
• Filed: 10/01/1975
• Issued: 01/25/1977
• Est. Priority Date: 04/23/1973
• Status: Expired due to Term

• Current Assignee: Mipro AB
• Original Assignee: Saab-Scania Aktiebolag
• Inventors: Nilsson, Jan, Swanson, Rune
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US05/618,422
• Time in Patent Office: 482 Days
• Field of Search: 310/8.2, 310/8.3, 310/8.5, 310/8.6, 310/8.8, 310/9.1, 310/9.4, 102/81, 102/70.2 G, 73/194 B, 73/194 C, 84/DIG. 24
• US Class Current: 310/339
• CPC Class Codes: H02N 2/185 using fluid streams
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

An electrical generator for projectiles and the like comprises a piezoelectric element housed in a cavity through which air is forced by missile movement. A reed-like tongue in the cavity has one end captive, its other end near a ram air inlet that terminates in a nozzle outlet which is aligned with the tongue and is so configured as to enable the ram air to impart vigorous vibration to the tongue. The piezoelectric element has a vibration transmitting connection with the tongue, near the captive end of the latter.

Claims

1. An electrical generator that can serve as a power source for electrical apparatus carried in a body in which the generator is also carried, and which generator can produce electrical energy as a result of relative motion between said body and a fluid in contact therewith, said generator being of the type comprising a piezoelectric element mounted in a cavity in the body and duct means in the body by which said cavity is communicated with the exterior of the body and by which a stream of fluid is caused to flow in consequence of relative movement between the body and said fluid in contact therewith, said generator being characterized by:

A. a flexible elongated tongue in said cavity having one of its ends in substantially fixed relation to the body but being otherwise spaced from the walls of the cavity to be free for vibratory flexing, said tongue

1. having a major width dimension and a minor width dimension so as to tend to flex in the directions of its minor width dimension and

2. having a longitudinal centerlines which, with the tongue unflexed, is substantially straight along a substantial part of the length of the tongue from its other end;

B. said duct means defining

3. The electrical generator of claim 1 wherein said means providing a motion transmitting connection comprises:

means bonding the piezoelectric element to the tongue in surface-to-surface engagement therewith along a portion of the tongue near said one end thereof, so that the piezoelectric element partakes of vibration of the tongue.

4. The electrical generator of claim 1 wherein the piezoelectric element is elongated and extends generally parallel to the tongue, one end of the piezoelectric element being secured to the body is spaced relation to said one end of the tongue, further characterized by said motion transmitting connection comprising:

an arm extending transversely to the tongue and the piezoelectric element between the other end of the piezoelectric element and a portion of the tongue near to but spaced from the first mentioned end of the tongue.

2. an inlet portion which opens to the exterior of the body at a front portion thereof,an elongated nozzle portion which is communicated with said inlet portion to receive incoming fluid therefrom and is communicated with said cavity to direct such fluid thereinto in a stream, said nozzle portion

a. having a major width at least substantially as large as the major width of the tongue and oriented in correspondence therewith,

b. having a minor width substantially equal to the minor width of the tongue,

c. having its longitudinal centerline coinciding with that of the unflexed tongue, and

d. opening to the cavity near said other end of the tongue;

and

3. outlet duct means communicated with the exterior of the body rearwardly of said inlet section and communicated with said cavity at a zone spaced lengthwise along the tongue from said other end thereof; and

C. means providing a motion transmitting connection between the piezoelectric element and the tongue by which vibration of the tongue is caused to impose oscillatory stresses upon the piezoelectric element, said connection being near the first mentioned end of the tongue so that the leverage of the tongue serves to match the mechanical impedance of the piezoelectric element to the acoustical impedance of the fluid.

5. An electrical generator that can serve as a power source for electrical apparatus and which is of the type comprising a piezoelectric element and excitation means for imposing oscillatory mechanical stresses upon said element in consequence of a fluid stream, to transfer energy from said stream to said element, said electrical generator being characterized by said excitation means comprising:

A. duct means communicated at one end with a source of fluid at one pressure and defining at its other end an outlet nozzle from which said fluid is caused to flow in a stream into a zone of lower pressure, said outlet nozzle being substantially elongated and straight in the direction of fluid flow and having

6. a major width dimension anda minor width dimension transverse to said major width dimension;

B. an elongated resiliently flexible tongue in said zone of lower pressure having one end near said nozzle, said tongue extending lengthwise away from said nozzle and having its other end in substantially fixed relation to the duct means, said tongue

1. having a major width dimension no larger than the major width dimension of the outlet nozzle and oriented in correspondence with the same,

2. having a minor width dimension extending in directions transverse to its major width dimension so as to tend to flex in said directions, said minor width dimension being substantially equal to the minor width dimension of the outlet nozzle, and

3. said tongue, when relaxed, having its longitudinally extending centerline aligned with that of said nozzle;

C. and means providing a force transmitting connection between said piezoelectric element and said tongue, near said other end of the latter, by which oscillatory flexing of the tongue in said directions imposes oscillatory mechanical stresses upon the piezoelectric element.

7. An electrical generator that can serve as a power source for electrical apparatus and which is of the type comprising a piezoelectric element and excitation means for imposing oscillatory mechanical stresses upon the piezoelectric element to transfer energy to it from fluid under pressure at a source thereof such as an inlet for ambient fluid in a moving body that carries said element, said excitation means comprising:

A. an elongated, resiliently flexible tongue that has one end which is substantially fixed and has its other end free, said tongue

1. having a major width dimension and a smaller minor width dimension extending in directions transverse to its width dimension so that its free end is capable of flexing oscillation in said directions, and

2. when relaxed, being straight along a substantial portion of its length from its free end;

B. nozzle means communicating with said source of fluid under pressure and having an outlet from which fluid from said source can flow in a stream, said nozzle means

8. having its outlet near the free end of said tongue and its inlet remote from the tongue,having its outlet end portion straight and smooth so that the stream of fluid issuing therefrom towards the free end of the tongue tends to be steady, andhaving its outlet axis lengthwise aligned with the central plane of said minor width of the tongue when the tongue is relaxed so that such stream, in flowing along the tongue, imparts vigorous oscillation to the tongue in said directions;

and

C. means providing a force transmitting connection between said peizoelectric element and said tongue, near said one end of the tongue, by which oscillatory flexing of the tongue in said directions imposes oscillatory mechanical stresses upon the piezoelectric element.