Speech transmitter

Abstract: A speech transmitter (10) for use in gas masks and the like comprises a body member (12) having a central, circular recess (14) in one end thereof and a marginal rim (16) surrounding the recess (14), and a cover member (22) having a complementary central, circular recess (24) in one end thereof and a marginal rim (26) surrounding the recess. The cover member (22) marginal rim (26) is lockingly engageable with the body member marginal rim (16) so as to form a unitary assembly in which the body recess (14) and the cover recess (24) are in coaxially aligned, face-to-face relation and define a membrane chamber (30). The marginal rims (16, 26) have mating surfaces (46, 80) adapted to secure and radially tension a membrane (32) between them. The membrane (32) has a marginal edge (34) interposed between the mating surfaces (46, 80) and a main body portion (36) disposed within the membrane chamber (30).

Description: Armed forces personnel may be required to perform their respective duties with equipment, including facial gas masks, issued for personal protection in contaminated land, sea, or air environments. Rapid and effective verbal exchange of information is essential for the conduct of operations. All mask designs currently in use for this purpose incorporate one or more voice transmitter assemblies in the form of sealed diaphragms. Other common design characteristics include a nosecup/mouth seal extending from the bridge of the nose, around the mouth and to a chincup. Voice transmission may be directly affected by changes in the design of the nosecup/mouth seal. Speech transmitters currently fitted into protective masks employ a metal casing which houses a mylar membrane and a specially constructed rubber tension ring to apply a frictional force to the membrane. The tension ring is secured in place by crimping of the entire assembly. Observations have shown that the tensional forces applied to the mylar membrane are not maintained over time resulting in progressive degradation of the quality of speech transmission. In addition to crimping the assembly, other designs apply tension to the mylar membrane by pulling the edges of the membrane around a radius. Rubber gaskets were introduced to prevent leakage and protect the mylar membrane. A construction of this type is shown in US-A-2586851. Current designs require a silicone rubber tension ring for each size of speech transmitter. Silicone requires a post curing operation and is relatively expensive. It has been found that mass production of these items has not been possible and, accordingly, costly manual assembly has been required. The present invention seeks to provide a speech transmitter which is easily manufactured and assembled and which provides reliability of tension application and sealing effectiveness. In accordance with the present invention, a speech transmitter comprises a disc shaped body member having a concentric, central circular recess in one end thereof and an outer, axially extending marginal rim surrounding said recess; a disc shaped cover member having a concentric, central, circular recess in one end thereof and an outer, axially extending marginal rim being lockingly engageable with said body member marginal rim in axial relation thereto, said body recess and said cover recess being in coaxially aligned face-to-face relation and defining a membrane chamber; and a thin, circular, membrane having a main body portion disposed in said membrane chamber and a marginal edge portion secured between said outer marginal rims of said body member and said cover member and is characterized in that said marginal rims have mating surfaces comprising an annular projection and a corresponding recess for receiving said annular projection, said annular projection and mating recess having inclined surfaces arranged such that when the marginal edge portion of said membrane is placed therebetween and said members are assembled by being telescoped into axial interengagement with one another, said inclined surface cooperate during said assembly to securely grip said marginal edge and radially outwardly pull said membrane to subject said membrane to uniform radial tension. The body and cover members are thus formed with interlocking means which engage when the two members are axially pressed together into a unitary or integral assembly. This considerably facilitates assembly of the device. In addition, the members are formed with interlocking surfaces which cooperate during assembly to securely grip the marginal edge of the mylar membrane and subject the membrane to a uniform radial tension. This arrangement avoids the need for a tension ring, seals and/or gaskets and, therefore, considerably facilitates both manufacturing and assembling and reduces costs. The speech transmitter may be used in gas masks and the like. These and other features of the invention will become apparent from the following description in which reference is made to the appended drawings, wherein: FIGURE 1 is a right side elevational view illustrating an apertured body member of a speech transmitter according to a preferred embodiment of the present invention; FIGURE 2 is a left side elevational view illustrating an apertured protective cover secured to the cover of a speech transmitter according to a preferred embodiment of the present invention; FIGURE 3 is a longitudinal cross-sectional view taken along line 3-3 of FIGURE 2; and FIGURE 4 is an enlarged, partially broken cross-sectional view similar to FIGURE 3 but illustrating the membrane securing and tensioning mechanism in greater detail. With reference to the drawings, the speech transmitter 10, according to a preferred embodiment of the invention, is comprised of a body member 12 having a central, circular recess 14 in one end thereof and a marginal rim 16 of circumferentially uniform cross-sectional shape surrounding the recess, a cover member 22 having a central, circular recess 24 in one end thereof and a marginal rim 26 of circumferentially uniform cross-sectional shape surrounding the recess. Cover member marginal rim 26 is lockingly engageable with body member marginal rim 16 so as to form, when assembled, a unitary or integral assembly with the body recess and the cover recess being in coaxially aligned, face-to-face relation defining a membrane chamber 30. As explained in greater detail below, the marginal rims are formed with mating surfaces adapted to both secure and tension a circular mylar membrane 32 therebetween. As best shown in FIGURE 3, the marginal portion 34 of the membrane is interposed between the rims of the body and cover members while a main body portion 36 thereof is disposed in membrane chamber 30. With reference to FIGURES 3 and 4, the main body portion 40 of body member 12 is thin and planar and formed with a plurality of apertures or holes 42, as best shown in FIGURE 1, to allow acoustical pressure waves access to membrane chamber 30. Marginal rim 16 of body member 12 includes an outer edge 44 in which there is formed a circumferentially, outwardly facing semi-circular recess 46 and which tapers inwardly to facilitate telescopic insertion of rim 16 into a flange in the cover member as described later. The inner face of rim 16 is formed with a pair of planar radial surfaces 48 and 50 which are axially spaced from one another and between which there is formed a generally triangular, annular recess 52. Recess 52 includes a cylindrical surface 54 which extends axially inwardly from the inner edge 56 of outer planar surface 48 and a conical surface 58 which extends from the end of surface 54 remote from surface 48 to the outer edge 60 of inner planar surface 50. The main body portion 70 of cover member 22 is thin and planar and formed with a plurality of apertures or holes 72, as best shown in dotted lines in FIGURE 2, to allow acoustical pressure waves access to membrane chamber 30. Marginal rim 26 of cover member 22 includes an outer edge 74 in which there is formed a tubular flange 76 having an inner cylindrical surface 78 which terminates in a circumferential, inwardly extending, semi-cylindrical bead or detent 80. Detent 80 is adapted to be received in recess 46 of the body member. The inner face of rim 26 is formed with a pair of planar radial surfaces 82 and 84 which are axially spaced from one another and between which there is formed a generally triangular, annular projection 86. Projection 86 includes a cylindrical surface 88 which extends axially outwardly from the inner edge of inner planar surface 82 and a conical surface 90 which extends from the end of surface 88 remote from surface 82 to the outer edge of outer planar surface 84. A disc shaped protector 100 (FIGURES 2 and 3) is secured to the cover member 22 on the side thereof remote from body member 12. The protector is formed with four equally angularly spaced notches 102 adapted to receive mating tabs or projections 104 extending from the cover member. In addition, the protector is formed with a plurality of axial holes or apertures 106, as best shown in FIGURE 2, for communicating acoustical pressure waves into and out of the membrane chamber. Body member 12, cover member 22 and protector 100 are formed of a thermoplastic material so that they can be readily and easily moulded into the shapes described hereinabove using conventional manufacturing techniques and thereby considerably facilitate assembly of the speech transmitter. Thus, in order to assemble the speech transmitter, the outer edge of the circular mylar membrane is placed between rims 16 and 26 of the body and cover members and then the two members are pressed axially against one another. As this occurs, the outer flange 76 of the cover member will flex radially outwardly as the bead slides onto and along the tapered outer edge of the cover member until bead 80 seats within its mating recess 46 in the cover. This inter-engagement securely holds the two members as a unitary assembly. In the meantime, the planar surfaces, annular projection 86 and mating recess 52 grasp the membrane and, as the body and cover members continue to move towards one another, the conical surfaces apply a uniform radially outward pull to the membrane, placing it under a suitable tension. Thus, it will be seen that the present invention is cost effective in that it can be readily constructed using conventional moulding and production techniques and allows for faster and easier assembly with lower incidence of rejects. In addition, no gasket or silicone tensioner is required to seal or aid in the tensioning of the mylar.

Claims: A speech transmitter, comprising: a disc shaped body member (12) having a concentric, central circular recess (14) in one end thereof and an outer, axially extending marginal rim (16) surrounding said recess; a disc shaped cover member (22) having a concentric, central, circular recess (24) in one end thereof and an outer, axially extending marginal rim (26) being lockingly engageable with said body member marginal rim (16) in axial relation thereto, said body recess (14) and said cover recess (24) being in coaxially aligned face-to-face relation and defining a membrane chamber (30); and a thin, circular, membrane (32) having a main body portion (36) disposed in said membrane chamber and a marginal edge portion (34) secured between said outer marginal rims (16, 26) of said body member and said cover member characterized in that said marginal rims have mating surfaces comprising an annular projection (86) and a corresponding recess (52) for receiving said annular projection (86), said annular projection (86) and mating recess (52) having inclined surfaces (90, 58) arranged such that when the marginal edge portion (34) of said membrane (32) is placed therebetween and said members (12, 22) are assembled by being telescoped into axial interengagement with one another, said inclined surface (90, 58) cooperate during said assembly to securely grip said marginal edge and radially outwardly pull said membrane to subject said membrane to uniform radial tension. A speech transmitter as defined in Claim 1, one of said marginal rims (26) having a circumferential annular locking bead (80) and the other of said marginal rims (16) having an circumferential annular locking recess (46) interlockingly engageable with said locking bead (80) for preventing axial separation of said body and cover members. A speech transmitter as defined in Claim 2, said one of said members having a longitudinally extending, tubular flange (76) extending from the marginal rim (26) thereof and adapted to telescopically receive the outer periphery of the other of said members, said bead (80) extending radially inwardly of an inner surface of said flange and said annular recess (46) being formed in said outer periphery of the other of said members. A speech transmitter as defined in any of claims 1 to 3, said mating surfaces including, on said body (12) and cover (22) members, complementary inner (50, 84) and outer (48, 82) axially displaced planar radial surfaces, a cylindrical surface (54, 88) extending axially from the inner edge of said outer surface (48, 82), and a conical surface (58, 90) extending inwardly from the end of said cylindrical surface (54, 88) remote from said outer surface (48, 82) to the outer edge of said inner surface (50, 84). A speech transmitter as defined in Claim 4, said cylindrical (88) and conical (90) surfaces of one of said members defining a membrane locking projection (86) and the cylindrical (56) and conical (58) surfaces of the other of said members defining a membrane locking recess (52) adapted to receive said membrane locking projection (86). A speech transmitter as defined in any of the preceding claims, each said body (12) and cover (22) members having apertures (42,72) for communicating acoustical pressure waves to enter and egress from said acoustical chamber. A speech transmitter as defined in any of the preceding claims, said body (12) and cover (22) members being formed of thermoplastic material. A speech transmitter according to any of the preceding claims, wherein said body (12) and cover (22) members are moulded from thermoplastic material.

Inventors: DAVIS RONALD E, DAVIS, RONALD E.
Applicants: CANADA MINISTER DEFENCE, THE MINISTER OF NATIONAL DEFENCE OF HER MAJESTY'S CANADIAN GOVERNMENT
Application year: 1989
Main classification: A62B18
IPC codes: G10K13, A62B18