Composite sheets constituting electromechanical transducers and transducers equipped with such sheets

Abstract

.[.The invention relates to a flexible composite sheet designed to constitute an undersheet behaving as an electromechanical transducer in order to detect the apnea of subjects lying on it. This sheet comprises, in addition to a foil sensitive to pressure in the sense of electromechanical transduction (an electret or polarized piezoelectric foil), two film electrodes and two protective foils. Spacing shims are glued to the two foils against which they are juxtaposed. When the sensitive foil is an electret, the shims are directly interposed between the sensitive foil and one of the two electrodes. When the sensitive foil is a polarized piezo-electric foil, the shims are directly interposed between one of the electrodes and the corresponding external protective foil..]. .Iadd.An apnea monitor/alarm consists of an electronic monitor circuit to actuate an alarm responsive to the output of a sheet-like electromechanical transducer. The transducer consists of an electret or polarized piezoelectric foil responsive to pressure to generate corresponding electrical signals, two film electrodes, and two protective foils. Shims are glued to two of the foils for spacing. If an electret sensor foil is used, the shims are directly interposed between the sensitive foil and one of the electrodes. If the sensitive foil is a polarized piezoelectric foil, the shims are directly interposed between one of the electrodes and the corresponding external protective foil. .Iaddend.

We claim: 
     
       1. Relatively flexible and extended composite sheet, constituting an electromechanical transducer and comprising a foil sensitive to pressure in the sense of electromechanical transduction, said pressure sensitive foil being interposed between two conductive foils or electrodes themselves covered exeternally with protective foils, said composite sheet also comprising, between the pressure sensitive foil and one of the protective foils, spacing shims of which the two opposite surfaces are glued respectively to the two opposite adjacent areas. 
     
     
       2. Sheet according to claim 1, wherein the sensitive foil is permanently electrically charged and creates an external electrical field, and the shims are directly interposed between said sensitive foil and one of the two electrodes. 
     
     
       3. Sheet according to claim 1, wherein the sensitive foil comprises a piezo-electric foil permanently electrically polarized and interposed contiguously between the two electrodes, the shims are directly interposed between one of these electrodes and the corresponding external protective foil. 
     
     
       4. Sheet according to claim 1, wherein the shims re self-adhesive on the said surfaces. 
     
     
       5. Sheet according to claim 1, wherein the areas on which the shims are glued are treated previously so as to facilitate this gluing. 
     
     
       6. Sheet according to claim 5, wherein said previous treatment is by electrical discharge. 
     
     
       7. Sheet according to claim 5, wherein said previous treatment comprises deposition of a thin layer of a suitable substance for enhancing said gluing. 
     
     
       8. Sheet according to claim 1, wherein the shims have a thickness comprised between 0.1 and 1 mm, a width comprised between 1 and 10 mm and a mutual spacing comprised between 5 and 100 mm. 
     
     
       9. Rectangular mattress construction incorporating a composite sheet according to claim 1, whose sides are comprised respectively between 10 and 30 cm and between 20 and 50 cm. 
     
     
       10. Sheet according to claim 1, wherein the various layers are constituted of transparent materials. 
     
     
       11. Electromechanical transducer comprising a composite sheet according to claim 1, and output means connected electrically to the two electrodes of said sheet. 
     
     
       12. Electrochemical transducer according to claim 11, including alarm means connected to said output means so as to activated thereby. .Iadd. 
     
     
       13.  An Apnea monitor comprising: a composite sheet of sufficient area to underlie a baby comprising:   a piezoelectric foil;   electrodes covering opposite surfaces of said piezoelectric foil;   cover layers overlying each of said electrodes; and   spacing means, located between one of said cover layers and the corresponding electrode and affixed to said one cover layer and said corresponding electrode at a plurality of locations, for providing a plurality of compartments between said one cover layer and said corresponding electrode such that portions of the piezoelectric foil which lie adjacent these compartments will be reversibly lengthened when a pressure force is applied to the composite sheet at the corresponding compartments, said compartments being distributed substantially uniformly over the area of said piezoelectric foil; and   a monitor means, connected to said electrodes, for monitoring electrical signals produced in response to changes in the piezoelectric foil, whereby rhythmic movements of a baby will rhythmically lengthen and relax said portions of said piezoelectric foil so as to produce an electrical signal in response to said rhythmic movements which is monitored by said monitor means. .Iaddend. .Iadd.14. An Apnea monitor as claimed in claim 13, wherein said monitor means includes alarm means for producing an alarm output when the electrical signal monitored by said monitor means is interrupted for a period longer than a predetermined threshold period.   
     
     
        .Iaddend. .Iadd.15.  An Apnea monitor comprising: a sheet of piezoelectric foil of sufficient area to underlie a baby;   electrodes covering opposite surfaces of said foil;   means providing a spaced shim support for portions of said foil while leaving other portions unsupported, and shim support being adhesively secured to one of the electrodes;   the unsupported portions being distributed substantially uniformly over the area of said foil;   a monitor;   and leads connecting said electrodes to said monitor;   whereby the biological functions of a baby will rhythmically lengthen and relax said unsupported portions of said foil to produce a signal, corresponding to said biological functions, on said electrodes which is transmitted to said monitor. .Iaddend. .Iadd.16. A monitor for monitoring biological movements of a living being, said monitor comprising:   (a) a composite sheet comprising: a relatively flexible piezoelectric foil:   a pair of electrode members located on opposite sides of said piezoelectric foil;   a cover member overlying at least one of said electrode members; and   spacing means, located between the piezoelectric foil and one of said members, for providing a plurality of spaces between said piezoelectric foil and said one member such that a portion of the piezoelectric foil which lies adjacent a said space will be reversibly lengthened and thinned when a pressure force is applied to said composite sheet at the corresponding space; and     (b) a monitor means, connected to said electrodes, for monitoring electrical signals produced in response to changes in the piezoelectric foil whereby biological movements of the living being will lengthen and relax at least some of said portions of said piezoelectric foil so as to produce an electrical signal in response to said movements which is monitored by said monitor means. .Iaddend. .Iadd.17. A monitor as claimed in claim 16 wherein at least one surface of said spacing means is secured to the surface adjacent thereto. .Iaddend. .Iadd.18. A monitor as claimed in claim 16 wherein said electrode members comprise metallic foils secured to opposite surfaces of said piezoelectric foil and said cover member comprises a protective foil, said spacing means being secured to one of said electrode foils and to said protective foil. .Iaddend. .Iadd.19. A monitor as claimed in claim 16 wherein said spaces comprises chambers distributed substantially uniformly over the area of said piezoelectric foil. .Iaddend. .Iadd.20. A monitor as claimed in claim 16, wherein said monitor means includes alarm means for producing an alarm output when the electrical signal monitored by said monitor means is interrupted for a   
     
     
        period longer than a predetermined threshold period. .Iaddend. .Iadd.21. A monitor for monitoring the movements of a living being, said monitor comprising: (a) an electromechanical transducer comprising:   a relatively flexible piezoelectric foil;   a pair of electrode members located on opposite sides of said piezoelectric foil; and   space defining means for defining a plurality of spaces adjacent portions of said piezoelectric foil such that a said portion of the piezoelectric foil will be reversibly depressed and lengthened when a pressure force is applied to the transducer at the corresponding space; and   (b) a monitor means, connected to said electrodes, for monitoring electrical signals produced in response to changes in the piezoelectric foil whereby movements of the living being will reversibly lengthen said portions of said piezoelectric sheet so as to produce an electrical signal in response to said movements for monitoring by said monitor means. .Iaddend. .Iadd.22. A monitor as claimed in claim 21 wherein said transducer comprises a composite sheet and said space defining means comprise spacing shim means for spacing said piezoelectric foil from one component of said composite sheet so as to define said spaces therebetween. .Iaddend. .Iadd.23. A monitor as claimed in claim 22, wherein said one component comprises a cover sheet which overlies one of said electrodes. .Iaddend. .Iadd.24. In a monitor for monitoring the biological movements of a living being, a transducer comprising:   a piezoelectric foil;   an electrode on each side of said foil, and   means for creating reversible depressions in said foil at selected positions distributed around the area of said foil in response to biological stimuli produced by a living being in contact with said film.   
     
     
        .Iaddend. .Iadd.25.  A transducer according to claim 24 in which said depression creating means comprises: shim means underlying said piezoelectric foil, said shim means creating a chamber at each of said selected locations under the piezoelectric foil into which a portion of said foil can be depressed in response to stimuli produced by a living being in contact with said transducer on the side of said transducer remote from said shim means. .Iaddend. .Iadd.26. A transducer according to claim 25 further comprising:   a protective sheet surrounding a composite formed by said foil, said electrodes and said shim means;   and means for affixing said shim means to at least one of said elements of said composite and to said protective sheet. .Iaddend. .Iadd.27. A method of monitoring biological functions of a living body comprising the steps of:   placing against a portion of the living body a transducer comprising a piezoelectric foil having electrodes on each surface thereof and having shim means distributed over the surface of said foil for creating a plurality of locations at which portions of said foil can be reversibly lengthened and thinned;   and utilizing the voltage generated between said electrodes responsive to the reversibly thinning of said foil at least one of said locations so as   
     
     
        to monitor biological functions of the living body. .Iaddend. .Iadd.28.  A monitor for monitoring the movements of a living being, said monitor comprising: (a) a relatively flexible transducer composite comprising:   an electret foil;   electrodes located on opposite sides of said electret foil;   a protective cover overlying at least one said electrodes; and   spacing means, affixed to the components of said composite lying adjacent thereto at a plurality of locations, for providing a plurality of compartments within said composite such that when a pressure force is applied to the composite at the corresponding compartments, the portions of the electret foil which lie adjacent these compartments produce an electrical output; and   (b) monitor means, connected to said electrodes, for monitoring electrical signals produced by said electret foil, whereby movements of a living being will cause pressure forces to be applied to said portions of said electret foil so as to produce a resultant electrical output signal in response to said movements which is monitored by said monitor means. .Iaddend.