Electrostatic transducer with nonplanar configured diaphragm

• US 6,201,874 B1
• Filed: 12/07/1998
• Issued: 03/13/2001
• Est. Priority Date: 12/07/1998
• Status: Expired due to Fees

• Current Assignee: LRAD Corporation
• Original Assignee: American Technology Incorporated (Emerson Electric Company)
• Inventors: Croft, James J. III, Norris, Elwood G.
• Primary Examiner(s): Kuntz, Curtis A.
• Assistant Examiner(s): Harvey, Dionne
• Application Number:
  US09/207,314
• Time in Patent Office: 827 Days
• Field of Search: 381/113, 381/116, 381/341, 381/342, 381/191, 381/398, 381/399, 381/423, 381/174, 381/173, 381/190, 367/170, 367/181
• US Class Current: 381/191
• CPC Class Codes: H04R 19/02 Loudspeakers H04R19/01 takes precedence
• CPC Class Codes: H04R 7/14 corrugated, pleated or ribbed

Abstract

An electrostatic transducer having respective first and second stators, each having an interior surface, which are displaced and juxtaposed, and including a flexible diaphragm leaving a conductive layer and being operable as an electrostatic emitter. The diaphragm includes an emitter portion which is interposed between the respective interior surfaces of the first and second stators and is configured as a nonplanar film characterized by a continuous array of peaks and valleys. The emitter portion of the diaphragm is positioned adjacent, but substantially unattached to the respective interior surfaces of the first and second stators. The peaks of the emitter portion of the diaphragm may contact the interior surfaces, or may be displaced therefrom. Also disclosed is a method for generating audio output from an electrostatic transducer utilizing a nonplanar emitter portion of a flexible, film diaphragm.

Claims

1. An electrostatic transducer, comprising:

a first rigid stator having an interior surface;

a second rigid stator having an interior surface displaced and juxtaposed from the interior surface of the first stator; and

at least one flexible diaphragm having a conductive layer and having an emitter portion operable as an electrostatic emitter, said emitter portion being interposed between the respective interior surfaces of the first and second stators, said diaphragm being configured as a nonplanar film characterized by a continuous array of peaks and valleys as viewed from each respective side of the diaphragm, said emitter portion of the diaphragm being positioned adjacent but substantially unattached to the respective interior surfaces of the first and second stators; and

means for applying voltages to the respective first and second stators and diaphragm to drive the diaphragm with an applied audio signal as a speaker device.

2. An electrostatic transducer as defined in claim 1, wherein the continuous array of peaks and valleys in the nonplanar film is represented in cross-section by a generally sinusoidal shape with alternating peaks and valleys of an adjacent side of the diaphragm with respect to one of the interior surfaces of the first and second stators.

3. An electrostatic transducer as defined in claim 2, wherein the movable diaphragm comprises opposing first and second nonconductive layers applied to opposing first and second sides of the conductive layer, the peaks of the first layer of the diaphragm being disposed for contact at the interior surface of the first stator in response to changing charge distribution on the first and second stators;

the peaks of the second side of the diaphragm being disposed in alternating manner with respect to the peaks of the first side for contact at the interior surface of the second stator in response to the changing charge distribution on the first and second stators;

the respective first and second stators including openings positioned adjacent the respective alternating valleys of the first and second sides of the diaphragm to enable propagation of sound through the stator to a surrounding environment.

4. An electrostatic transducer as defined in claim 3, wherein the respective interior surfaces of the first and second stators include a thin cushion layer of material to provide a soft landing area of contact for the peaks of the respective first and second sides of the diaphragm.

5. An electrostatic transducer as defined in claim 4, wherein the cushion layer is selected from the group of materials consisting of polyester, cotton, polyurethane, nylon, rayon, silk, and conductive materials of polyester, cotton, polyurethane, nylon, rayon, and silk.

6. An electrostatic transducer as defined in claim 4, wherein the cushion layer is nonconductive and has a thickness of less than 2 millimeters nonconductive.

7. An electrostatic transducer as defined in claim 2, wherein the movable diaphragm comprises at least two conductive layers of film, at least two of the conductive layer of film having respective first and second nonconductive layers applied to opposing first and second sides which are most adjacent to the interior surfaces of the respective first and second stators, the peaks of the first nonconductive layer of the diaphragm being disposed for contact at the interior surface of the first stator in response to changing charge distribution on the first and second stators;

the peaks of the second nonconductive side of the diaphragm being disposed in alternating manner with respect to the peaks of the first side for contact at the interior surface of the second stator in response to the changing charge distribution on the first and second stators;

the respective first and second stators including openings positioned adjacent the respective alternating valleys of the first and second sides of the diaphragm to enable propagation of sound through the stator to a surrounding environment.

8. An electrostatic transducer as defined in claim 7, wherein the respective interior surfaces of the first and second stators include a thin cushioning layer of material to provide a soft landing area of contact for the peaks of the respective first and second sides of the diaphragm.

9. An electrostatic transducer as defined in claim 4, wherein the cushion layer is continuous across the interior surface of at least one of the stators.

10. An electrostatic transducer as defined in claim 4, wherein the cushion layer is segmented in noncontinuous manner, said segments of the cushion layer being positioned for contact with contiguous peaks extending across the interior surface of at least one off the stators.

11. An electrostatic transducer as defined in claim 4, wherein the cushion layer is conductive, said diaphragm having a nonconductive contacting side juxtaposed to the conductive cushion layer.

12. An electrostatic transducer as defined in claim 1, wherein the interior surfaces of the first and second stators are geometrically configured to generally conform to the general geometric configuration of the peaks and valleys of the diaphragm to enable close positioning of the respective interior surfaces of the first and second stators adjacent to the diaphragm.

13. An electrostatic transducer as defined in claim 12, wherein the interior surfaces of the first and second stators are segmented as separate surface areas which are geometrically configured to generally conform to individual geometric configurations of adjacent peaks of the diaphragm to enable close positioning of the respective segmented interior surfaces of the first and second stators adjacent to the diaphragm.

14. An electrostatic transducer as defined in claim 13, wherein the segmented surface areas are geometrically configured as concave surfaces to generally conform to individual sinusoidal convex surfaces of adjacent peaks of the diaphragm to enable close positioning of the respective segmented interior surfaces of the first and second stators adjacent to the diaphragm.

15. An electrostatic transducer as defined in claim 13, wherein the segmented surface areas are geometrically configured as convex surfaces to generally conform to individual sinusoidal concave surfaces of adjacent valleys of the diaphragm to enable close positioning of the respective segmented interior surfaces of the first and second stators adjacent to the diaphragm.

16. An electrostatic transducer as defined in claim 12, wherein the interior surfaces of the first and second stators are segmented as separate surface areas which are geometrically configured to generally conform to individual geometric configurations of adjacent valleys of the diaphragm to enable close positioning of the respective segmented interior surfaces of the first and second stators adjacent to the diaphragm.

17. An electrostatic transducer as defined in claim 13, wherein the segmented surface areas of the respective first and second stators include alternating (i) surface areas adjacent a diaphragm valley and (ii) surface areas adjacent a diaphragm peak, said respective surface areas adjacent the diaphragm peaks being separately powered with voltage as compared with voltage applied to surface areas adjacent the diaphragm valleys.

18. An electrostatic transducer as defined in claim 17, further comprising voltage control circuitry coupled to the respective stators wherein (i) a zero voltage is applied to the surface areas adjacent to the diaphragm peaks when (ii) an attracting voltage is applied to surface areas adjacent diaphragm valleys to minimize attractive forces at contacting peaks with the interior surface area of the respective stators, while maintaining strong attractive forces with respect to diaphragm valleys.

19. An electrostatic transducer as defined in claim 1, wherein the diaphragm is configured with a sinusoidal curvature and the interior surfaces of the first and second stators are geometrically configured to generally conform to the sinusoidal curvature of the diaphragm.

20. An electrostatic transducer as defined in claim 1, wherein the diaphragm is configured with a saw tooth configuration and the interior surfaces of the first and second stators are geometrically configured to generally conform to the configuration of the diaphragm.

21. An electrostatic transducer as defined in claim 1, wherein the diaphragm is configured with a rectified sine wave curvature and the interior surfaces of the first and second stators are geometrically configured to generally conform to the curvature of the diaphragm.

22. An electrostatic transducer as defined in claim 1, wherein the diaphragm interposed between the first and second stators is generally unattached to either of the first or second stators except at peripheral points of attachment, enabling the diaphragm to respond to driving forces of the stators as a single speaker membrane with enhanced low frequency response.

23. An electrostatic transducer as defined in claim 1, wherein the peaks of each side of the diaphragm are unattached to the respective interior surfaces of the first and second stators except for anchoring points at a periphery of the diaphragm.

24. An electrostatic transducer as defined in claim 1, wherein the respective first and second stators are configured respectively with concave and convex geometries in nesting relationship to provide an audio speaker having a convex emitting surface.

25. An electrostatic transducer as defined in claim 1, wherein the respective first and second stators are configured respectively with concentric, enclosing geometries to provide an audio speaker having a substantially full surround emitting surface.

26. An electrostatic transducer as defined in claim 25, wherein the respective first and second stators are configured with cylindrical geometries.

27. An electrostatic transducer as defined in claim 1, wherein the respective first and second stators are in nonparallel relati onship, said diaphragm extending with one surface of peaks and valleys adjacent the interior surface of the first stator, and a second surface of peaks and valleys adjacent the interior surface of the second stator.

28. An electrostatic transducer as defined in claim 27, wherein the respective first and second stators form an angular relationship wherein the interior surfaces of the first and second stators are at an acute angle and wherein the audio output of the transducer corresponds more closely to a push-pull system than a single sided system.

29. An electrostatic transducer as defined in claim 27, wherein the respective first and second stators form an angular relationship wherein the interior surfaces of the first and second stators are at an approximate right angle and wherein the audio output of the transducer corresponds more closely to a push-pull system than a single sided system.

30. An electrostatic transducer as defined in claim 27, wherein the respective first and second stators form an angular relationship wherein the interior surfaces of the first and second stators are at an oblique angle, and wherein the audio output of the transducer corresponds more closely to a push-pull system than a single sided system.

31. An electrostatic transducer as defined in claim 1, wherein the second stator is displaced off center of alignment with the first stator, said diaphragm extending along and between the respective interior surfaces of the first and second stators for a length such that a first side of the diaphragm covers the interior surface of the first stator and an opposing second side of the diaphragm covers the interior surface of the second stator, the total surface area of one side of the diaphragm being greater than the interior surface area of either of the first or second stators, said first side of the diaphragm being nonconductive with respect to the first stator and the second side of the diaphragm being nonconductive with respect to the second stator, and wherein the audio output of the transducer corresponds more closely to a push-pull system than a single sided system.

32. An electrostatic transducer as defined in claim 1, wherein the continuous array of peaks and valleys as viewed from each respective side of the diaphragm are configured to vary resonance response of the diaphragm across the interior surfaces of the stators.

33. An electrostatic transducer as defined in claim 32, wherein a portion of the diaphragm is configured with peaks and valleys of relative greater dimension for enhancement of low frequency resonance, compared with peaks and valleys of other portions of the diaphragm which are of lesser dimension for enhancement of higher resonant frequencies.

34. An electrostatic transducer as defined in claim 33, wherein the diaphragm is configured with peaks and valleys of relative greater thickness for enhancement of low frequency resonance, compared with peaks and valleys of other portions of the diaphragm which are of lesser thickness for enhancement of higher resonant frequencies.

35. An electrostatic transducer, comprising:

a first rigid stator having an interior surface;

a second rigid stator having an interior surface displaced and juxtaposed from the interior surface of the first stator; and

at least one flexible diaphragm having a conductive layer and being operable as an electrostatic emitter, of said diaphragm having an emitter portion interposed between the respective interior surfaces of the first and second stators and including a nonplanar surface configuration comprising an array of peaks and valleys on opposing sides of the diaphragm forming multiple contact points of the diaphragm with respective interior surface areas of the stators, said contact points being separated from adjacent contact points by noncontacting regions of the diaphragm displaced from the interior surface areas;

said emitter portion being substantially unattached to the respective stators except at a periphery for positioning the diaphragm in a stable location between the stators.

36. A method for generating audio output from an electrostatic transducer, comprising the steps of:

a) selecting a first rigid stator having an interior surface;

b) selecting a second rigid stator having an interior surface;

c) configuring at least one flexible, electrostatic diaphragm as a nonplanar film having an emitter portion characterized by a continuous array of peaks and valleys as viewed from each respective side of the diaphragm,

d) positioning the emitter portion between the respective interior surfaces of the first and second stators with said peaks of each side of the emitter portion being positioned adjacent but substantially unattached to the respective interior surfaces of the first and second stators to enable the peaks to displace orthogonally with respect the interior surfaces of the stators during operation; and

e) applying voltages to the respective first and second stators and diaphragm to drive the diaphragm with an applied audio signal as a speaker device.