Snap action mechanical-electrical piezoelectric transducer

• US 3,976,899 A
• Filed: 12/23/1974
• Issued: 08/24/1976
• Est. Priority Date: 01/04/1973
• Status: Expired due to Term

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Fanshawe, David Geoffrey James
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US05/535,995
• Time in Patent Office: 610 Days
• Field of Search: 310/8.3, 310/8.5, 310/8.6, 310/8.7, 310/9.1, 310/9.4, 340/365 E, 200/67 A, 200/67 D, 200/67 DA, 200/67 DB, 200/181
• US Class Current: 310/339
• CPC Class Codes: H01H 13/702 with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
• CPC Class Codes: H01H 2201/02 Piezo element
• CPC Class Codes: H01H 2215/034 Separate snap action
• CPC Class Codes: H01H 2223/036 forming chamfered apertures for keys
• CPC Class Codes: H01H 2227/028 Key stroke
• CPC Class Codes: H01H 2227/032 Operating force
• CPC Class Codes: H03K 17/964 Piezoelectric touch switches
• CPC Class Codes: H03K 17/967 having a plurality of control members, e.g. keyboard H03K17/969, H03K17/972, H03K17/98 take precedence
• CPC Class Codes: H03K 2217/96027 Piezoelectric snap spring
• CPC Class Codes: H10N 30/30 with mechanical input and electrical output, e.g. functioning as generators or sensors

Abstract

A mechanical-electrical transducer producing an electric signal upon depression of a spring, such as a pushbutton. A piezoelectric element is held in contact with a snap-action spring, and bends when the spring snaps thus producing an electric signal.

Claims

1. A mechanical-electrical transducer comprising a monostable snap action spring formed from a sheet of material of the type which snaps from a first shape to a second shape along one dimension upon application of at least a given force to the spring, and a piezoelectric element;

in the absence of force applied to the spring, a portion of the spring extending transverse to said one dimension being bowed transverse to said dimension, said bow being substantially constant upon application of force less than said given force to the spring;

upon said spring snapping along said one dimension, said bow changing to a transverse bow in an opposite direction; and

piezoelectric means for sensing change of said direction of said transverse bow only, said means comprising said piezoelectric element and means for holding said piezoelectric element in contact with said transverse portion of said spring.

2. A transducer as claimed in claim 1, wherein said first dimension extends longitudinally of said sheet of material, said spring being symmetrical about a longitudinal plane, and adapted to snap upon application of said given force along a direction lying in said plane, said transverse portion being substantially perpendicular to said plane.

3. A transducer as claimed in claim 2, wherein said piezoelectric element is elongated in said transverse direction.

4. A transducer as claimed in claim 1, wherein said means for holding comprises a material bonding said element to said spring.

5. A transducer as claimed in claim 1, wherein said means for holding comprises a resilient clamping member extending transverse to said dimension.

6. A mechanical electrical transducer comprising a blade spring adapted for flexure along one dimension from a first position to a second position, said blade spring having a snap action at a point intermediate said two positions and having a portion bowed transversely to said dimension, the direction of said transverse bow reversing upon said snap action, a piezoelectric element, and means for holding said piezoelectric element in contact with said bowed portion, said piezoelectric element being responsive solely to reversal of the bow direction for generation of an output voltage.