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Title:
METHOD OF AND ARRANGEMENT FOR MANUFACTURING A PLASTIC DIAPHRAGM FOR AN ELECTROACOUSTIC TRANSDUCER
Document Type and Number:
WIPO Patent Application WO/2000/058073
Kind Code:
A1
Abstract:
An arrangement (1) for and a method of manufacturing a plastic diaphragm (2) use a deep-drawing station (20) which has a deep-drawing die (33) of a sintered material, air present between the front surface (34) of the deep-drawing die (33) and the basic foil (10) which faces this front surface (34) is extracted through the deep-drawing die (33) via the particle-free interstices formed in the sintered material between the particles (60) coalesced by sintering.

Inventors:
Frasl, Ewald (Prof. Holstlaan 6 AA Eindhoven, NL-5656, NL)
Application Number:
PCT/EP2000/001869
Publication Date:
October 05, 2000
Filing Date:
March 06, 2000
Export Citation:
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Assignee:
KONINKLIJKE PHILIPS ELECTRONICS N.V. (Groenewoudseweg 1 BA Eindhoven, NL-5621, NL)
International Classes:
B29C51/26; B29C51/36; H04R31/00; B29C35/08; B29C51/00; B29C51/10; B29C65/48; B29L31/38; (IPC1-7): B29C51/36; H04R31/00
Foreign References:
EP0299168A2
EP0363594A2
DE19517458C1
GB2094701A
US3527854A
US5061427A
Attorney, Agent or Firm:
Weber, Helmut (Internationaal Octrooibureau B.V. Prof. Holstlaan 6 AA Eindhoven, NL-5656, NL)
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Claims:
CLAIMS:
1. A method of manufacturing a diaphragm (2) for an electroacoustic transducer, which diaphragm consists of a plastic and has a given crosssectional shape, which method comprises the process steps defined hereinafter, namely: transferring a length of foil (10) which consists of a plastic and is substantially flat to a deep drawing station (20) in which deepdrawing in a given deepdrawing direction (21) can be effected and which includes a deepdrawing die (33) which has a front surface (34) whose crosssectional shape corresponds to the given crosssectional shape of the diaphragm (2) and which has a rear surface (35) situated at a distance from the front surface (34) in the deep drawing direction (21), and holding the length of foil (10) in a position facing the front surface (34) of the deepdrawing die (33), and activating a vacuum generating device (36) for generating a partial vacuum and by means of the activated vacuum generating device (36) subjecting the deepdrawing die (33) to suction in the area of the rear surface (35) of the deepdrawing die and by means of the activated vacuum generating device (36) extracting the air present between the front surface (34) of the deep drawing die (33) and the length of foil (10) facing the front surface (34) from the front surface (34) through the deepdrawing die (33) to the rear surface (35) of the deepdrawing die (33), and activating a pressurizing device (39) for generating a higher pressure and by means of the activated pressurizing device (39) exerting pressure on the length of foil (10) facing the front surface (34) of the deepdrawing die (33) and by means of the activated pressurizing device (39) pressing the length of foil (10) facing the front surface (34) of the deepdrawing die (33) onto the front surface (34) of the deepdrawing die (33), in order to provide the length of foil (10) with a crosssectional shape corresponding to that of the front surface (34) of the deep drawing die (33), and moving the length of foil (42) provided with the given crosssectional shape away from the deepdrawing station (20), and separating the residual portion (54) of the length of foil (42) from the useful portion (46) of the length of foil (42), which useful portion forms the diaphragm (2) and exhibits the given cross sectional shape, characterized in that the length of substantially flat foil (10) is transferred to a deepdrawing station (20) having a deepdrawing die (33) of a sintered material, and air present between the front surface (34) of the deepdrawing die (33) and the length of foil (10) which faces this front surface (34) is extracted through the deepdrawing die (33) via the particlefree interstices formed in the sintered material between the particles (60) coalesced by sintering.
2. A method as claimed in Claim 1, characterized in that, after the length of foil (42) provided with the given crosssectional shape has been moved away from the deepdrawing station (20), the useful portion (46) of the length of foil (42), which useful portion forms the diaphragm (2) and exhibits the given crosssectional shape, is joined to a metal ring (45) which surrounds the useful portion (46) of the length of foil (42), and separating the residual portion (54) of the length of foil (42) from the useful portion (46) of the length of foil (42) is effected along a separating zone which extends in radial directions outside the metal ring (45).
3. A method as claimed in Claim 1, characterized in that, before the substantially flat length of foil (10) is transferred to the deepdrawing station (20), the length of foil (10) is transferred to a heating station (14) and is heated to a temperature in a given temperature range.
4. A method as claimed in Claim 1, characterized in that the pressure exerted on the length of foil (10) facing the front surface (34) of the deepdrawing die (33) by means of the activated pressurizing device (39) is exerted on the foil surface which corresponds to the diaphragm rear surface of the diaphragm (2) to be manufactured.
5. An arrangement (1) for manufacturing a diaphragm (2) for an electroacoustic transducer, which diaphragm consists of a plastic and has a given crosssectional shape, which arrangement (1) comprises the means defined hereinafter as parts, namely: a deepdrawing station (20) in which deepdrawing in a given deepdrawing direction (21) can be effected and which includes a deepdrawing die (33) which has a front surface (34) whose crosssectional shape corresponds to the given crosssectional shape of the diaphragm (2) and which has a rear surface (35) situated at a distance from the front surface (34) in the deep drawing direction (21), and positioning means (9) for transferring a length of foil (10) which consists of a plastic and is substantially flat to the deepdrawing station (20), and holding means (23,27,24) for holding a length of foil (10) thus transferred in a position facing the front surface (34) of the deepdrawing die (33), and a vacuum generating device (36) by means of which a partial vacuum can be generated and by means of which the deepdrawing die (33) can be subjected to suction in the area of the rear surface (35) of the deepdrawing die (33) and the air present between the front surface (34) of the deepdrawing die (33) and a length of foil (10) facing the front surface (34) can be extracted from the front surface (34) of the deepdrawing die (33) to the rear surface (35) of the deepdrawing die (33) through the deepdrawing die (33), and a pressurizing device (39) by means of which a higher pressure can be generated and by means of which pressure can be exerted on a length of foil (10) facing the front surface (34) of the deepdrawing die (33) and a length of foil (10) facing the front surface (34) of the deep drawing die (33) can be pressed onto the front surface (34) of the deepdrawing die (33), in order to provide this length of foil (10) with a crosssectional shape corresponding to that of the front surface (34) of the deepdrawing die (33), and positioning means (9) with the aid of which a length of foil (42) provided with the given cross sectional shape can be moved away from the deepdrawing station (20), and separating means (53) with the aid of which the residual portion (54) of a length of foil (42) can be separated from the useful portion (46) of this length of foil (42), which useful portion forms the diaphragm (2) and exhibits the given crosssectional shape, characterized in that the deepdrawing station (20) has a deepdrawing die (33) of a sintered material, and the deepdrawing die (33) has particlefree interstices formed in the sintered material between the particles (60) coalesced by sintering, via which interstices air present between the front surface (34) of the deepdrawing die (33) and a length of foil (10) which faces this front surface (34) can extracted through the deepdrawing die (33).
6. An arrangement (1) as claimed in Claim 5, characterized in that, joining means (44) have been provided to which a length of foil (42) provided with the given crosssectional shape can be transferred after it has been moved away from the deepdrawing station (20) and to which, in addition, a metal ring (45) can be transferred, by which joining means the useful portion (46) of the length of foil (42), which useful portion forms the diaphragm (2) and exhibits the given crosssectional shape, can be joined to the metal ring (45) in such a manner that the metal ring (45) surrounds the useful portion (46) of the length of foil (42), and the separating means (53) are arranged and adapted to separate the residual portion (54) of the length of foil (42) from the useful portion (46) of the length of foil (42) along a separating zone which extends in radial directions outside the metal ring (45).
7. An arrangement (1) as claimed in Claim 5, characterized in that a heating station (14) has been provided to which a substantially flat length of foil (10) can be transferred and by means of which this length of foil (10) can be heated to a temperature in a given temperature range.
8. An arrangement (1) as claimed in Claim 5, characterized in that the deepdrawing station (20) has a deepdrawing die (33) of a sintered material, which deep drawing die (33) has a front surface (34) whose crosssectional shape corresponds to the cross sectional shape of the diaphragm (2) at the location of the diaphragm front surface.
9. A diaphragm (2) for an electroacoustic transducer, which diaphragm (2) consists of a plastic and has a given crosssectional shape and has been manufactured by means of a deepdrawing process, characterized in that the diaphragm (2) is formed to be completely free from protrusions on at least one diaphragm surface, which protrusions are convex with respect to a diaphragm surface.
Description:
Method of and arrangement for manufacturing a plastic diaphragm for an electroacoustic transducer.

The invention relates to a method of manufacturing a diaphragm as defined in the opening part of Claim 1.

The invention further relates to an arrangement as defined in the opening part of Claim 5.

The invention further relates to a diaphragm as defined in the opening part of Claim 9.

Such a method, such an arrangement and such a diaphragm have already been available at the Applicant's for several years and are well-known at least among experts. The known method and the known arrangement use a deep-drawing die which consists of brass and which has air ducts between the front of the deep-drawing die and the rear of the deep- drawing die, which ducts extend substantially in the deep-drawing direction and are formed by holes having a diameter of, for example, approximately 0.15 mm. The air ducts have been provided to allow the air present between the length of foil and the front of the deep-drawing die during a deep-drawing process to escape as rapidly as possible from this area, namely through the deep-drawing die via the air ducts. In this construction the air is discharged in a point by point fashion because the air can escape only through the air ducts in a point by point fashion, which leads to a comparatively inhomogeneous contact of the length of foil on the deep-drawing die at the location of the front of this die. Another problem is that during a deep- drawing process the thin air ducts may already be covered by the length of foil in an early stage, after which the residual air can no longer escape unimpededly. The known construction further requires a comparatively high pressure in order to press the foil onto the front of the deep-drawing die in a reliable manner. Moreover, comparatively long cycle times are needed.

Furthermore, it is to be noted that in spite of their small diameter the air ducts give rise to irregularities in a manufactured diaphragm in the diaphragm surface which cooperates with the front of the deep-drawing die, which irregularities take the form of convex protrusions on this diaphragm surface of the diaphragm, which are caused by the fact that during the manufacture of the diaphragm the length of foil is drawn partly into the air ducts, which leads to permanent deformations.

It is an object of the present invention to preclude the afore-mentioned problems and to provide an improved method and an improved arrangement for manufacturing a diaphragm as well as an improved diaphragm.

In order to achieve this object in a method as defined in the opening part of Claim 1, the characteristic features defined in the characterizing part of Claim 1 have been provided in accordance with the invention.

In order to achieve this object in an arrangement as defined in the opening part of Claim 5, the characteristic features defined in the characterizing part of Claim 5 have been provided in accordance with the invention.

In order to achieve this object in a diaphragm as defined in the opening part of Claim 9, the characteristic features defined in the characterizing part of Claim 9 have been provided in accordance with the invention.

By the provision of the characteristic features in accordance with the invention it is achieved by simple means and in a simple manner that during the manufacture of a plastic diaphragm both a comparatively rapid as well as a particularly steady escape through the deep- drawing die is guaranteed for air present between a length of foil and the front of the deep- drawing die, as a result of which a length of foil is always pressed very homogeneously onto the front of the deep-drawing die and air ducts in the deep-drawing die can never be occluded in a point-by-point fashion. The use of such a deep-drawing die of a sintered material furthermore enables a comparatively low pressure to be used and allows shorter cycle times in comparison with the measures known until now. In addition, as a result of the provision of a deep-drawing die of a sintered material it is achieved that no convex irregularities are formed on any of the diaphragm surfaces of a manufactured diaphragm because such a deep-drawing die of a sintered material has a perfectly uniform cross-sectional shape without any entrances to air ducts. A further advantage of such a deep-drawing die of a sintered material is that the manufacturing costs for the manufacture of such a deep-drawing die are substantially lower than for the manufacture of a known brass deep-drawing die provided with thin air ducts.

In a method in accordance with the invention and in an arrangement in accordance with the invention it has proved to be advantageous when, in addition, the characteristic features defined in Claim 2 and in Claim 6, respectively, are provided.

Connecting the useful portion of a length of foil, which portion forms the finished diaphragm, to a metal ring before this useful portion is separated from the residual portion of the relevant length of foil has the very important advantage that the finished diaphragm can be handled in a

safe manner protected from damage and that the finished diaphragm can simply be built into and retained in an electroacoustic transducer with the aid of the metal ring.

In a method in accordance with the invention and in an arrangement in accordance with the invention it has proved to be advantageous when, in addition, the characteristic features defined in Claim 3 and in Claim 7, respectively, are provided. Such a heating of a length of foil to be subjected to a deep-drawing process guarantees a particularly uniform deep-drawing of the length of foil, which is very favorable for a high diaphragm quality.

A diaphragm in accordance with the invention does not exhibit any irregularities, such as convex protrusions, on its diaphragm surfaces, as a result of which it has a particularly uniform shape in the direction of its thickness, which is particularly favorable for a high acoustic performance.

The above-mentioned as well as further aspects of the invention will become apparent from the example of an embodiment described hereinafter and will be elucidated with reference to this example.

The invention will now be described in more detail with reference to the drawings, which shows an embodiment given by way of example but to which the invention is not limited.

Figure 1 shows an arrangement embodying the invention in a highly diagrammatic manner, which arrangement is adapted to manufacture a plastic diaphragm for an electroacoustic transducer by means of a method in accordance with the invention and includes a deep-drawing station.

Figure 2 shows a part of the deep-drawing station of the arrangement shown in Figure 1 to an enlarged scale in comparison with Figure 1, the part shown including a deep- drawing die of the deep-drawing station.

Figure 3 shows a diaphragm manufactured by means of the arrangement shown in Figure 1.

Figure 1 diagrammatically shows an arrangement 1 for manufacturing a plastic diaphragm 2 having a given cross-sectional shape for an electroacoustic transducer, not shown.

Such a diaphragm 2 is shown in Figure 3. The diaphragm 2 has a curved central portion 4, which is rotationally symmetrical with respect to a diaphragm axis 3, a substantially <BR> <BR> <BR> flat annular intermediate portion 5, a curved peripheral portion 6, a hollow cylindrical spacer portion 7, which extends parallel to the diaphragm axis 3, and a mounting portion 8, which extends perpendicularly to the diaphragm axis 3. The intermediate portion 5 serves for connection to a moving coil, not shown. The mounting portion 8 serves for mounting the diaphragm 2 in an electroacoustic transducer.

The device 1 comprises a multitude of parts, of which parts the means mentioned and described hereinafter are shown in Figure 1.

The arrangement 1 has positioning means 9 which serve for positioning a length of foil 10, which consists of a plastic and is essentially flat. In a version of a device 1 realized in practice the position means 9 have been realized with the aid of a so-called rotary table. The positioning means 9 include a first positioning ring 11 and a second positioning ring 12. In a manner not shown the two positioning rings 11 and 12 are held together to be coaxial with the diaphragm axis 3 in a manner not shown, the length of flat foil 10 being held between them, as is illustrated for the position of the positioning means 9 indicated by the reference symbol PI in Figure 1. The positioning means 9 are movable into the position bearing the reference symbol PI in a direction indicated by an arrow 13.

In the present case the positioning means 9 form feed-in means which are movable to a deep-drawing station of the arrangement 1 in order to feed in the length of substantially flat plastic foil 10, as will be described in greater detail hereinafter.

The arrangement 1 further includes a heating station 14. The length of substantially flat foil 10 can be fed to the heating station 14 with the aid of the positioning means 9 in a direction indicated by an arrow 15. The heating station 9 has infrared radiators 16 which are carried by a fixture 17 for the infrared radiators 16. The heating station 14 further has a power supply source 18 for the infrared radiators 16, which power supply source is connected to the infrared radiators 16 via an electrically conductive connection 19. By means of the heating station 14, i. e. by means of the infrared radiators 16 of the heating station 14, the flat foil section 10 can be heated to a temperature in a given temperature range. This heating of the foil section 10 results in a slight plastic deformation of the length of foil 10, thereby causing the length of foil 10 to sag, as is shown at the position bearing the reference symbol P2 in Figure 1.

The arrangement 1 further includes a deep-drawing station 20 in which deep- drawing in a given deep-drawing direction 21 can be effected. The deep-drawing station 20

has a die box 22 comprising a lower section 23 and an upper section 24. In the end surface 26 of the lower section 23, which faces the end surface 25 of the upper section 24, the lower section has been provided with a seal 27 in the form of a so-called 0-ring. The lower section 23 has a low-pressure chamber 28. The upper section 24 has a high-pressure chamber 29. The lower section 23 can be moved in the direction indicated by an arrow 30 into the operating position shown in Figure 1. The upper section 24 can be moved in the direction indicated by an arrow 31 into the operating position shown in Figure 1. When the lower section 23 and the upper section 24 are in their respective operating positions, the intermediate area between the two end surfaces 25 and 26 is sealed by means of the seal 27.

When the lower section 23 and the upper section 24 have been moved into their respective rest positions in directions opposite to those indicated by the two arrows 30 and 31, the length of foil 10 can be brought to the deep-drawing station 20 in the direction indicated by an arrow 32 with the aid of the feed-in means formed by the positioning means 9, the positioning means 9 together with the length of foil 10 then assuming the position bearing the reference symbol P3 in Figure 1.

The deep-drawing station 20 has a deep-drawing die 33 mounted in the lower section 23. The deep-drawing die 33 has a front surface 34 with a cross-sectional shape corresponding to the cross-sectional shape of the diaphragm 2 and a rear surface 35 spaced from the deep-drawing direction 21. With the aid of retaining means, which in the present case are formed by means the lower section 23, the seal 27 provided in the lower section and the upper section 24, the length of foil 10, which has been fed to the deep-drawing station 20 with the aid of the positioning means 9, can be held in a position opposite to the front surface 34 of the deep-drawing die 33.

The arrangement 1, i. e. its deep-drawing station 20, includes a vacuum generating device 36 by means of a which a partial vacuum can be generated. The vacuum generating device 36 is connected to a coupling portion 38 of the lower section 23 via a flexible tube 37, the vacuum generating device 36 thus being connected to the low-pressure chamber 28. By means of the vacuum generating device 36 it is possible to subject the deep- drawing die 33 to suction in the area of the rear surface 35 of the deep-drawing die 33 and to extract the air present between the front surface 34 of the deep-drawing die 3 and the length of foil 10 facing the front surface 34 from the front surface 34 of the deep-drawing die 33, through the deep-drawing die 33, to the rear surface 35 of the deep-drawing die 33.

The arrangement 1, i. e. its deep-drawing station 20, further includes a pressurizing device 39. By means of the pressurizing device 39 a higher pressure can be

produced. The pressurizing device 39 is connected to a coupling portion 41 of the upper section 24 via a flexible tube 40, the pressurizing device 39 thus being connected to the high- pressure chamber 29. By means of the pressurizing device 39 it is possible to exert pressure on the length of foil 10 which faces the front surface 34 of the deep-drawing die 33 and to press the length of foil 10 which faces the front surface 34 onto the front surface 34 of the deep- drawing die 33. By thus pressing the length of foil 10 onto the front surface 34 of the deep- drawing die 33 this length of foil 10 can be given a cross-sectional shape corresponding to that of the front surface 34 of the deep-drawing die 33. At position P3 in Figure 1 a length of foil 42 is shown which has already been given the cross-sectional shape corresponding to that of the front surface 34 of the deep-drawing die 33.

The arrangement 1 has feed-out means for feeding the length of foil 42 provided with the given cross-sectional shape away from the deep-drawing station 20 and to further means of the arrangement 1, said feed-out means enabling the length of foil 42 provided with the given cross-sectional shape away from the deep-drawing station 20. In the present case the feed-out means, just as the feed-in means, are formed by the positioning means 9. Feeding-out with the aid of the positioning means can be effected in the direction indicated by an arrow 43.

The arrangement 1 further includes joining means 44 adapted to receive a length of foil 42 provided with the given cross-sectional shape can be conveyed after it has been moved away from the deep-drawing station 20 in the direction indicated by the arrow 43 and, in addition, adapted to receive a metal ring 45, which joining means enable the useful portion 46 of the length of foil 42, which portion has the given cross-sectional shape and subsequently forms the diaphragm 2, to be joined to the metal ring 45 in such a manner that the metal ring 45 surrounds the useful portion 46 of the length of foil 42. The joining means 44 include supporting means 47, which are movable in the direction indicated by an arrow 48 from a rest position into an operating position shown in Figure 1, in which operating position a length of foil 42 which is in the position referenced P4 can be supported by the supporting means 47. The joining means 44 further include substantially pot-shaped holding means 49 which are annular in their area 50 which faces the supporting means 47 and which are movable in the direction indicated by an arrow 51 from a rest position into the operating position shown in Figure 1. The holding means 49 can hold the metal ring 45 in such a manner that upon a movement of the holding means 49 in the direction indicated by the arrow 51 the metal ring 45 can be brought into contact with the length of foil 42. It is to be noted that before the metal ring 45 is brought to the length of foil 42 an adhesive is applied to the length of foil

42 in the area where the metal ring 45 is positioned, thereby enabling an adhesive joint to be made between the length of foil 42 and the metal ring 45 after the metal ring 45 has been placed.

After the joint has been made between the metal ring 45 and the length of foil 42 the supporting means 47 and the holding means 49 are moved into their rest positions in directions opposite to those indicated by the arrows 48 and 51, after which the length of foil 42 together with the metal ring 45 are moved in a direction indicated by an arrow 52 with the aid of the positioning means 9, namely into the position bearing the reference symbol P5 in Figure 1.

The arrangement 1 includes separating means 53 at a location corresponding to the position P5. The separating means 53 serve for separating the residual portion 54 of the length of foil 42 from the useful portion 46 of the length of foil 42 along a circular separating zone which extends in radial directions outside the metal ring. The separating means are arranged and constructed accordingly. The separating means 53 include a laser beam source 55 which is arranged on a rotationally drivable support 55H for the laser beam source 55 and which is capable of generating a laser beam 56 represented diagrammatically in Figure 1. The laser beam 56 is aimed at the length of foil 42 and enables the residual portion 54 of the length of foil 42 and the useful portion 46 of the length of foil 42 to be separated in a simple and exact manner. During separation with the aid of the separating means 53 the metal ring 45 together with the length of foil 42 attached to it can be held by further pot-shaped holding means 57, as is illustrated in Figure 1. The further holding means 57 are movable in a direction indicated by an arrow 58 from a rest position not shown into the operating position shown in Figure 1.

After separation with the aid of the separating means 53 the further holding means 57 are movable in a direction indicated by an arrow 59, namely into a position indicated by the reference symbol P6 in Figure 1. The metal ring 45 together with the diaphragm 2 attached to it by an adhesive joint and formed by the useful portion 46 of the length of foil 42 is held in this position P6. From the position P6 shown in Figure 1 the finished diaphragm 2, together with the metal ring 45 joined to it for the purpose of holding and handling the diaphragm 2, can be moved in a direction indicated by an arrow 62 into a further position, not shown, for example in order to be packaged with the aid of a packaging device.

In the arrangement 1 shown in Figure 1 the deep-drawing station 20 advantageously has a deep-drawing die 33 of a sintered material. For the deep-drawing die 33 of a sintered material reference is made to Figure 2 which shows the deep-drawing die 33 of a

sintered material by way of illustration. As is apparent from Figure 2, the deep-drawing die 33 has particle-free interstices between the particles 60 coalesced by sintering, as is known per se of a sintered material. Via the particle free interstices between the particles 60 coalesced by sintering air present between the front surface 34 of the deep-drawing die 33 and a length of foil 10, which faces this front surface and which is shown in a position in which it has already been urged towards the front surface 34 of the deep-drawing die 33, can be extracted through the deep-drawing die 33, namely in a direction indicated by an arrow 61 in Figure 2. This extraction is effected with the aid of the vacuum generating device 36, which is not shown in Figure 2.

As can be seen in Figure 2, the deep-drawing station 20 has a deep-drawing die 33 which consists of a sintered material and which has a cross-sectional shape which corresponds to the cross-sectional shape of the diaphragm 2 at the location of the front of the diaphragm. Such a construction has proved to be particularly advantageous in practice.

The deep-drawing die of a sintered material consists of non-corrodible steel particles and is produced by sintering of a steel granulate. However, alternatively the deep- drawing die may consist of other metal particles, for example brass particles, coalesced by sintering.

The arrangement 1 in accordance with the invention shown in Figure 1 is capable of carrying out a method in accordance with the invention of manufacturing a plastic diaphragm 2 having a given cross-sectional shape for an electroacoustic transducer. Such a method in accordance with the invention has the process steps described hereinafter.

A length of substantially flat plastic foil 10 is transferred to the heating station 14, where the length of foil 10 is heated to a temperature in a desired given temperature range so as to promote plastic deformation of the length of foil 10.

Subsequently, the length of foil 10 is transferred to the deep-drawing station 20, in which deep-drawing of the length of foil 10 is effected so as to obtain a length of foil 42 having a given cross-sectional shape. In order to carry out this deep-drawing the vacuum generating device 36 is activated so as to extract the air present between the still virtually non- deformed length of foil 10 and the front surface 34 of the deep-drawing die 33 via the particle- free interstices formed in the sintered material between the particles 60 of the sintered material which have been coalesced by sintering. Furthermore, the pressurizing device 39 is activated to generate a pressure in the high-pressure chamber 29 which is sufficiently high to press the length of foil 10 to be subjected to plastic deformation onto the front surface 34 of the deep- drawing die 33. It is to be noted that during such a deep-drawing process the deep-drawing die

is heated to a given temperature by heating means not shown, namely to a temperature in a range between 110°C and 145eC. The pressure in the high-pressure chamber 29 is then in a range between 10 bar and 25 bar.

After deep-drawing of the length of originally flat foil 10 and shaping of the length of foil 42 having the given cross-sectional shape the length of foil 42 is transferred to the joining means 44 with the aid of the length of foil 42 is joined to the metal ring 45. After the joint between the metal ring 45 and the length of foil 42 has been formed the assembly is transferred to the separating means 53, with the aid of which the residual portion 54 of the length of foil 42 is separated from the useful portion 46 of the length of foil 42, after which the useful portion 46 of the length of foil 42, i. e. the diaphragm 2, which is attached to the metal ring 45, is subjected to further operations or processes.

The arrangement 1 in accordance with the invention and the method in accordance with the invention guarantee that during the manufacture of a plastic diaphragm 2 the air present between a length of foil 10 and the front surface 34 of the deep-drawing die 33 is extracted comparatively rapidly and, above all, in a particularly steady manner through the deep-drawing die 33, as a result of which a length of foil 42 is always pressed very homogeneously onto the front surface 34 of the deep-drawing die 33. Moreover, this is achieved at a comparatively low pressure and with comparatively short cycle times, as a result of which a high output per unit of time is guaranteed.

A diaphragm in accordance with the invention as shown in Figure 3 has the particularly important advantage that no irregularities are produced on any diaphragm surface of the manufactured diaphragm 2 because this diaphragm 2 has been manufactured by means of a deep-drawing die 33 of the deep-drawing station 20 of the arrangement 1 in accordance with the invention, which deep-drawing die consists of a sintered material and does not have any ducts for extracting the air, as a result of which no irregularities caused by such ducts can be produced during the manufacture of the diaphragm 2.