Ferroelectric transducers

• US 5,925,969 A
• Filed: 10/17/1996
• Issued: 07/20/1999
• Est. Priority Date: 10/17/1995
• Status: Expired due to Term

• Current Assignee: Cormac G O'Neill
• Original Assignee: Cormac G O'Neill
• Inventors: O'Neill, Cormac G.
• Primary Examiner(s): LaBalle, Clayton E.
• Application Number:
  US08/733,156
• Time in Patent Office: 1,006 Days
• Field of Search: 310/323, 310/328, 310/366, 310/317
• US Class Current: 310/328
• CPC Class Codes: H02N 2/043 Mechanical transmission means, e.g. for stroke amplification

Abstract

Ferroelectric transducers each including two cooperating, identically polarized ferroelectric stacks which are excited in opposite polarity. Each transducer includes a yoke assembly for sensing the respective expansions and contractions of the two ferroelectric stacks, mechanically adding these respective expansions and contractions, and applying the sum thereof to a pair of elongated T-levers, which T-levers serve to displace the output element of the transducer.

Claims

1. A ferroelectric transducer, comprising:

a rigid frame having a base plate, a roof plate, and a plurality of side walls;

supporting plate means immovably affixed to opposite ones of said side walls and located above and spaced from said base plate;

a first ferroelectric stack the lower end of which bears upon said supporting plate means;

a second ferroelectric stack the lower end of which bears upon said supporting plate means;

a yoke plate overlying said ferroelectric stacks and provided on its lower face with first and second elongated, parallel indentations, each of which indentations overlies one of said ferroelectric stacks;

a first roller disposed between said yoke plate and the upper end of said first ferroelectric stack and engaged with one of said indentations;

a second roller disposed between said yoke plate and the upper end of said second ferroelectric stack and engaged with the other one of said indentations;

depressor means for exerting downward force on the top of said yoke plate and thus pressing said rollers against the respective upper ends of said ferroelectric stacks;

anchor plate means immovably affixed to opposite ones of said side walls and juxtaposed to said yoke plate in a predetermined juxtaposition when said first and second ferroelectric stacks are unexcited; and

flexure plate means affixed adjacent its opposite ends to said yoke plate and to said anchor plate means respectively, whereby to prevent transverse motion of said yoke plate with respect to said ferroelectric stacks, and at the same time to permit tilting or rocking motion of said yoke plate.

2. A ferroelectric transducer as claimed in claim 1, further comprising:

first and second displacement multiplication levers affixed respectively to opposed ends of said yoke plate, embracing the mutually confronting portions of said ferroelectric stacks and extending below the lower face of said supporting plate means; and

cross-brace means interconnecting the portions of said displacement multiplication levers located below said supporting plate means.

3. A ferroelectric transducer as claimed in claim 2 wherein said downward force on said yoke plate is provided by an elongated loop of metallic tape which is clamped to said depressor means at its upper end, anchored to said supporting plate means at its lower end and passes between said confronting faces of said ferroelectric stacks.

4. A ferroelectric transducer as claimed in claim 2, further comprising:

a tool beam;

first and second vertically disposed tool beam support plates affixed to said base plate and located adjacent to and spaced from said cross-brace means;

first and second thin, flexible H-plates, each H-plate being comprised of a frame portion and two finger portions projecting inwardly from said frame portion and thus defining an H-shaped central aperture adapted to receive one end of said tool beam;

each of said frame portions being fixedly mounted on adjacent ends of said first and second tool beam support plates; and

the ends of said tool beam being mounted, respectively, on the finger portions of one of said H-plates.

5. A ferroelectric transducer as claimed in claim 4 in which said tool beam is coupled to said cross-brace means by at least one strut and thus the motion of said cross-brace means is imparted to said tool beam.

6. A tool tractor, comprising:

a rigid frame having a base plate, a roof plate, and a plurality of side walls;

supporting plate means immovably affixed to opposed ones of said side walls and located above and spaced from said base plate;

a first ferroelectric stack the lower end of which bears upon said supporting plate means;

a second ferroelectric stack the lower end of which bears upon said supporting plate means;

a yoke plate overlying said ferroelectric stacks and provided on its lower face with first and second elongated, parallel indentations, each of which indentations overlies one of said ferroelectric stacks;

a first roller disposed between said yoke plate and the upper end of said first ferroelectric stack and engaged with one of said indentations;

a second roller disposed between said yoke plate and the upper end of said second ferroelectric stack and engaged with the other one of said indentations;

depressor means for exerting downward force on the top of said yoke plate and thus pressing said rollers against the respective upper ends of said ferroelectric stacks;

anchor plate means immovably affixed to opposite ones of said side walls of said rigid frame and thus juxtaposed to said yoke plate in a predetermined juxtaposition when said first and second ferroelectric stacks are unexcited;

flexure plate means affixed adjacent its opposite ends to said yoke plate and to said anchor means respectively, whereby to prevent transverse motion of said yoke plate with respect to said ferroelectric stacks, and at the same time to permit tilting or rocking motion of said yoke plate;

tool displacement signal producing means for producing an electrical displacement signal which represents the momentary displacement of said tool beam from its position of rest; and

a feedback control system which compares said electrical displacement signal with an output command signal and produces a correction signal by means of which to hold the actual tool displacement in precise correspondence with the momentary magnitude of a stored electrical signal representing predetermined momentary tool displacement.

7. A tool tractor as claimed in claim 6, further comprising stack exciting means comprised of two oppositely polarized direct current power supplies the predetermined output voltages of which are substantially equal, and a driver amplifier the output voltage of which varies between the positive values of said predetermined output voltages, the instantaneous value of said driver amplifier output voltage being determined by the value of a stored modulating signal representing a predetermined momentary tool displacement pattern.

8. A tool tractor as claimed in claim 7, further comprising a shaft position encoder which is coupled to a workpiece chuck.