US3792526A

US3792526A - Method of sound transducer construction

Info

Publication number: US3792526A
Application number: US00135886A
Authority: US
Inventors: G Bremseth
Original assignee: LTV LING ALTEC Inc
Current assignee: LTV LING ALTEC Inc
Priority date: 1971-04-21
Filing date: 1971-04-21
Publication date: 1974-02-19
Anticipated expiration: 1991-02-19

Abstract

A method of constructing a sound transducer which obviates the need for certain centering and fixture practices relative to assembly of the diaphragm element and voice coil within the air gap defined by a magnet structure. The method consists of forming a rearward or forward oriented frame assembly with selected concentric configurations matingly adapted to receive similarly shaped diaphragm elements and the outer concentric edge of the magnet such that it must then follow that the voice coil is properly positioned within the air gap in non-interfering disposition.

Description

United States Patent 1191 1111 3,792,526

Bremseth 1 Feb. 19, 1974 [54] METHOD OF SOUND TRANSDUCER 3,230,319 l/l966 Kliewar 179 1155 R CONSTRUCTION 3,586,792 6/1971 Gayford.... 29/594 X 1,964,606 6/1934 Thuras l79/ll5.5 R 1 lnvemori Gerald Bremseth, Oklahoma 3,617,654 11 1971 Heidrich 179 1155 R City, Okla. [73] Assignee: LTV Ling Altec, lnc., Oklahoma Primary Examiner Charles W. Lanham City, Okla. Assistant Examiner-Carl E. Hall [22] Filed: Apr. 21 1971 211 Appl. No.: 135,886 [57] ABSTRACT A method of constructing a sound transducer which obviates the need for certain centering and fixture [52] Cl practices relative to assembly of the diaphragm cle- 1 Int Cl no 13/00 ment and voice coil within the air gap defined by a Fieid 4 602 magnet structure. The method consists of forming a I [79/1155 PC 1155 R 181 R rearward or forvvard oriented frame assembly with se I lected concentric configurations matingly adapted to receive similarly shaped diaphragm elements and the [56] References Cited outer concentric edge of the magnet such that it must UNITED STATES PATENTS then follow that the voice coil is properly positioned 2,371,820 3/1945 Gustafson 29/594 X within the air gap in non-interfering disposition. 3,079,472 2/1963 Sariti 4 3,430,007 2/1969 Thielen 179/115.5 R 4 Claims, 6 Drawing Figures i 5? g2 5- 2'4 54 26- 8a m as BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates generally to acoustic energy transducers and, more particularly, but not by way of limitation, it relates to improved construction and assembly methods for acoustic pressure transducers.

2. Description of the Prior Art 7 The prior art has relied upon various methods for aligning the elements during assembly of loudspeakers and the like. In assembly, it is mandatory that both the magnet structure and the diaphragm with an attached voice coil must be precisely centered in an associated frame structure which provides operative support for the interactive elements. In addition to the centering, the diaphragm must be held in place in such a manner as to allow a portion of the diaphragm to move or vibrate along the axis of the loudspeaker. In many previous methods it was usual to clamp the diaphragm between two surfaces around a particular circumference referred to as the clamp circumference. It was necessary to key the diaphragm element for use with a matched magnet and frame structure in order that accurate positioning of the voice coil with the air gap would be assured. In other cases, it was necessary to employ tediousfixturing in the assembly process to insure proper insertion of the voice coil in the air gap, and such procedures were subject to many forms of assemblers error, carelessness and such; and this often resulted in a high percentage of failures in production.

:SUMMARY OF THE INVENTION The present invention contemplates an improvement in a method of assembly of acoustic energy transducers of the type utilizing an electro-magnetically driven diaphragm element. In a more limited aspect, the invention consists of a method of forming a diaphragm element with a series of concentric, conformative configurations which are identical with concentric, seating configurations and transverse frame element; which transverse frame element serves to effect proper positioning of both the diaphragm element and the associated voice coil and magnetic element of the assembly. All elements of critical tolerance as to concentricity and alignment are maintained in proper relationship to enable easy and precise assembly without the necessity for matching of elements or components.

Therefore, it is an object of the present invention to provide a novel sound transducer wherein the diaphragm is formed with a step structure for the purpose of centering and clamping. the diaphragm in an associated frame structure.

It is also an object of the invention to provide a method for construction of a loudspeaker diaphragm which may be centered and clamped in an associated frame structure by simple hand assembly without the use of fixturing, cements or secondary operations.

It is still further an object of the invention to provide a method of transducer assembly which results in considerable cost savings in manufacture and assembly with a resulting increased functional performance.

Finally, it is an object of the present invention to providea method of sound transducer assembly which insures proper interactive positioning of the several component elements of the transducer, and which enables a more reliable assembly procedure with reduction of assembly failures.

Other objects and advantages of the invention will be evident from the following detailed description when read in. conjunction with the accompanying drawing which illustrates the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a sound transducer in partial section as constructed in accordance with the present invention;

FIG. 2 is a front elevation of a transverse frame element constructed in accordance with the present invention;

FIG. 3 is a front elevation of a diaphragm element constructed in accordance with the present invention;

FIG. 4 is an exploded side view in vertical section showing a magnet assembly, diaphragm and transverse frame element; I

FIG. 5 is a side elevation of a reverse oriented sound transducer in partial section which constitutes an alternative form of the invention; and

FIG. 6 is an exploded view in vertical section of still another form of the invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, an energy transfer portion of a sound transducer 10 e.g. a horn loudspeaker assembly, is shown as consisting of a horn element 12 formed integrally as by molding with a main frame 14, and having the anterior or rear p'a'rt closed over by a rear frame 16, shown in dash-lines. A folded sound energy director element 17 is connected to the main frame center along the axis thereof. The rear frame 16 may define a chamber or space 18 of predetermined volume wherein weather proof connection terminals, control relays or such may be located.

The transducer 10 includes'driving structure consisting of a magnet assembly 20 secured in coactive relationship with a diaphragm elernent22 supporting the voice coil 24, and a transverse frame 26 provides seating and centering support as it is assembled in contact with both the diaphragm element 22 and magnet structure 20. See also FIGS. 2, 3 and 4 which show the essential elements of the driver in greater detail. The opposite side of frame 26 is formed to receive main frame 14 and director element 17 in-operative engagement.

The magnet assembly 20 is of a conventional formation wherein pole elements are formed by a rear ring 28, forward ring 30 and center ring 32 assembled as shown for coaction with a ring-shaped magnet 34, e.g. a ceramic magnet composition or the like. The forward ring 30 is secured in concentric relationship with respect to the center ring 32 to define an air gap 36 extending axially of magnet assembly 20. A central bore 38 is formed through the center of the center pole piece 32 and front pole piece 28 to allow passage of vibratory energy in alternative structures, as will be further described. I

The diaphragm element 22 is formed as a unitary transverse structure 40 as formed from conventional substances such as phenolic compositions, impregnated linens and the like, and a coil former 42 carrying voice coil 24 is secured as by cementing to the rearward part of the diaphragm element 22, as will be further described below. A pair of energizing leads 44 and 46 may be lead through respective holes 48 and 50 in element 22 for conductive connection to the voice coil 24.

Actually, the voice coil 24 may be wound on coil former 42 with allowance of additional conductor material to be lead out as energizing

leads

44 and 46.

The element 22 is formed with an outer annular ring 52 which serves as a clamping surface in the assembled structure. The outer annular ring 52 then extends into forwardly extending cylindrical portion 54 which extends axially of the loudspeaker assembly into further formation of a second annular ring 56. In like manner, the inner edge of second annular portion 56 extends into a second cylindrical portion 58 proceeding forwardly along the axis of the loudspeaker l0, and the center portion of element 22 is filled out as the vibratile or sound-moving portion 60. A stiffening ring 62 is formed on vibratile portion 60 at about the inner diameter of center pole piece 32 to damp out adverse vibrations. The coil former 42 is then secured as by cementing around the inner surface of the second cylindrical portion 58 of diaphragm element 40, this rendering the voice coil 24 at a precise concentric positioning relative to the second cylindrical portion 58, and the first cylindrical portion 48, as well as the precisely formed

annular portions

56 and 52 and the outer perimeter of diaphragm element 22.

Referring now more particularly to the transverse frame 26, the various mating and centering facilities of this element are formed to be of precise nature relative to the similar concentric configurations of diaphragm element 22. Thus, the transverse frame 26 is unitarily formed but including various step portions for enabling mating and centering functions. The transverse frame 26 is molded or otherwise formed to include a series of concentrically arranged bores which define a plurality of annular shoulder portions and cylindrical inner walls of critical dimension. An outer flange 64 is formed to include a pair of

guide holes

66 and 68 which may be utilized in the initial lining up as well as for fastening in the assembly process. The inner edge of outer flange portion 64 is then formed to define a cylindrical wall 70 which terminates in an annular shoulder 72 which, in turn, is formed to define a cylindrical wall 74 terminating in an annular shoulder portion 76. The annular portion 76 again forms a cylindrical wall 78 which tenninates in a base portion 80 to complete the transverse frame 26. The base portion 80 includes axially open portions 82 to allow passage of air. A pair of oppositely disposed

holes

84 and 86 are formed to receive the

energizing leads

44 and 46 therethrough, and channel formations 88 are formed to allow interference free lead out of the energizing leads.

The method of the present invention enables a selfcentering feature due to the fact that the diaphragm element 22 is formed with steps or

cylindrical portions

54 and 58 formed as an integral part thereof, and being precisely formed so that the proper mating within the bores or

cylindrical side walls

74 and 78 will assure proper centering of the diaphragm element 22 without the necessity of using fixtures, cement or other securing agents. The outer annular portion 52 of diaphragm element 22 seats against the shelter or annular surface 72 of transverse frame 26 and, upon'proper assembly, the forward ring 30 of magnet assembly fits securely within cylindrical wall 70 of transverse frame 26 such hat it serves to clamp the diaphragm annular portion 40 securely about its outer periphery, as well as to provide proper alignment as between air gap 36 and coil former 42 and voice coil 24. Proper keeping of tolerances in forming of parts, as between the inner and outer diameters or edges of forward ring 30 and the mating portions of diaphragm element 22 and transverse frame 26, will always assure that voice coil 24 rides within air gap 36 in non-interfering relationship to provide dependable operation at maximum efficiency.

It is also contemplated that the diaphragm may be constructed to provide a reliable, accurate clamp circumference which provides the clearance necessary for movement or electrical connections without the use of gaskets or shaped clamping structure. Such alteration would be a design consideration and well available within normal skill.

The self-centering diaphragm element 22 offers sev eral advantages over conventional methods. Thus, it not only enables centering of the voice coil 24 in the air gap 36, but it assures non-interfering freedom of movement therein. This non-interfering insertion is accomplished with a minimum of air gap which results in a net gain in efficiency of the loudspeaker.

The structure of FIG. 5 illustrates an alternative form of sound transducer wherein the sound producing assembly is oriented opposite from that of the FIG. 1 structure Thus, a transducer 90 consists of a horn portion 92 defining sound throat 94 and including integrally formed front frame portion 96 for coaction with a transverse frame 98. The transverse frame 98 is precisely formed with mating configurations as will be further described, to secure a diaphragm 100 and associated voice coil 102 in proper mating interaction with magnet assembly 104 which defines an air gap 106.

In this alternative form, the transverse frame 98 includes a plurality of concentric,

cylindrical bores

108 and 109 spaced by annular portion 110 which coact with precise, form-fitting configurations on diaphragm 100 to ensure proper centering of voice coil 102 within air gap 106. The transverse frame 98 is essentially the same as transverse frame 26 of FIGS. 1, 2 and 4 except that it is formed for opposite orientation relative to the sound producing and directing assemblies. Thus, transverse frame 98 includes a raised central portion 112 which forms a concave and centrally aligned structure relative to the diaphragm element 100.

The diaphragm element 100 is also precisely formed for mating engagement within transverse frame 98 thereby to assure proper alignment of voice coil 102. The diaphragm element 100 includes an outer annular portion 114 formed integrally with a firstv cylindrical portion 116 and second annular portion 118 for mating engagement within the counterpart portions of transverse frame 98. A second or inner cylindrical portion 120 recieves coil former 122 therewithin in what is a properly fixtured position relative to the functional interaction of components of the sound transducer 90.

The magnet assembly 104 is essentially the same as the magnet assembly 20 of the FIG. 1 embodiment except that it functions in a different manner to receive acoustic pressure or sound energy through its axial center for progression out through the throat 94 of horn 92. The transverse frame 98 is also formed to have an annular portion 124 connecting inner cylindrical bore 109 and the center portion 112, the annular portion 124 being aligned at a rearward angle slightly displaced from the transverse axis such that the central portion 112 forms an air space 126 in between diaphragm element 100 and transverse frame 98 thereby to allow space for vibratile movement of the diaphragm element.

FIG. 6 illustrates still another embodiment wherein a magnet-diaphragm assembly is formed for precise, mating engagement. Thus, a magnet-diaphragm assembly 130 consists of a magnet assembly 132, which is formed essentially as the aforementioned magnet assemblies and 104. Magnet assembly 132 includes an annular groove 134 formed concentrically within the rear face 136 of a pole element ring 138. A diaphragm element 140 is then precisely formed to include an annular shoulder or ring portion 142 formed integrally about front face of an outer annular portion 144 of diaphragm element 140. The ring portion 142 is formed in precise manner to mesh with the annular groove 134 in mating engagement, and when such engagement is effected a voice coil 136 is assured of proper noninterfering-fit within air gap 148 of magnet assembly 132. The diaphragm element 140 further includes a concentric cylindrical poriton 150 which defines a surface for receiving coil former 152 in properly aligned relationship, and the central part of the diaphragm element 140 is then completed as a dome portion 154 which provides the actual air moving medium. A clamping ring 156 of conventional type may then be utilized to secure the diaphragm element 140 in properly positioned manner against the rear side of magnet assembly 132, ring portion 142 being matingly received within groove 134.

' The previous discussion describes those cases where both the diaphragm and themagnet assembly are centered in a separate transverse frameyhowever, the novelty advanced herein will also apply in those cases where the diaphragm element is centered by utilizing the magnet structure itself. An example of such diaphragm centering is that which must be effected relative to dome radiator loudspeaker assemblies of recently evolved type. Such loudspeakers are extremely simple in concept and design but proper centering of the diaphragm element is very difficult to achieve. The fixturing of such dome elements is extremely difficult such that many manufacturers resort to blind assembly, or assembly by feel, and this results in a very high reject rates. Requisite provisions of large air gap necessitated by assembly technique tends to decrease efficiency. These problems are overcomeutilizing the key-formed diaphragm and frame structures as described herein, at the same time effecting minimum air gap and maximum efficiency, i.e. efficiency varies inversely with the volume of the air gap.

The present invention would apply to all transducers using a diaphragm in conjunction with an electrical voice coil operating in an air gap; viz., cone loudspeakers, horn driving units, dome or diaphragm loudspeakers, diaphragm microphones, under water loudspeakers or transducers, etc. The method of construction offers a solution to some major problems in construction of such units and it is considered to be distinct improvement in transducer fabrication and assembly. The selfcentering diaphragm eliminates any fixturing operations, and all critical dimensions are part of the molding or forming tool itself which can be precisely maintained for all components of a plurality of assemblies Without need for component matching. Thus, the self-centering diaphragm is not only a separate concept but it also provides a more accurate method of assembly.

Changes may be made in the combination and arrangement of steps and/or elements as heretofore set forth in the specification and shown in the drawing; it being understood that changes may be made in the embodiments disclosed without departing from the spirit and scope of the invention as defined in the following claims.

What is claimed is:

i 1. A method of constructing a sound transducer of the type which includes a transverse frame element securing a permanent magnet assembly defining an air gap, a diaphragm element and a voice coil in proper operative position, such construction comprising the steps of:

forming said diaphragm element unitarily to include at least one concentric surface around an outer portion of said diaphragm element, which concentric surface extends parallel to the axis of movement of the diaphragm element, said diaphragm element further supporting a concentric voice coil in secure affixure;

forming said magnet assembly to define an air gap for non-interfering coaction with said voice coil when assembled, said magnet assembly being formed to have a selected diameter of that portion adjacent the diaphragm when assembled;

forming said transverse frame element to include a first cylindrical bore having said pre-selected diameter, and a second cylindrical bore therein which is concentric but having a reduced diameter such that the second cylindrical bore wall will receive said diaphragm element concentric surface securely therein; and

assembling the diaphragm element, magnet assembly and transverse frame element to form the sound transducer wherein the cylindrical surface, cylindrical bores and magnet assembly of pre-selected diameter cooperate to orient and position the diaphragm element and voice coil, the transverse frame, and the magnet and air gap in proper operative position. Y

2. A method of constructing a sound transducer as set forth in claim 1 wherein said step of forming said diaphragm element further comprises:

forming a first annular portion having concentric inner and'outer edges to extend outward from and adjacent to the forward edge of said at least one concentric surface, and a second annular portion having concentric inner and outer edges to extend inward from and adjacent to the rear edge of said at least one concentric surface to further form a

Claims

1. A method of constructing a sound transducer of the type which includes a transverse frame element securing a permanent magnet assembly defining an air gap, a diaphragm element and a voice coil in proper operative position, such construction comprising the steps of: forming said diaphragm element unitarily to include at least one concentric surface around an outer portion of said diaphragm element, which concentric surface extends parallel to the axis of movement of the diaphragm element, said diaphragm element further supporting a concentric voice coil in secure affixure; forming said magnet assembly to define an air gap for noninterfering coaction with said voice coil when assembled, said magnet assembly being formed to have a selected diameter of that portion adjacent the diaphragm when assembled; forming said transverse frame element to include a first cylindrical bore having said pre-selected diameter, and a second cylindrical bore therein which is concentric but having a reduced diameter such that the second cylindrical bore wall will receive said diaphragm element concentric surface securely therein; and assembling the diaphragm element, magnet assembly and transverse frame element to form the sound transducer wherein the cylindrical surface, cylindrical bores and magnet assembly of pre-selected diameter cooperate to orient and position the diaphragm element and voice coil, the transverse framE, and the magnet and air gap in proper operative position.

2. A method of constructing a sound transducer as set forth in claim 1 wherein said step of forming said diaphragm element further comprises: forming a first annular portion having concentric inner and outer edges to extend outward from and adjacent to the forward edge of said at least one concentric surface, and a second annular portion having concentric inner and outer edges to extend inward from and adjacent to the rear edge of said at least one concentric surface to further form a central vibratable portion.

3. A method as set forth in claim 2 wherein said central vibratable portion is formed to include a second concentric, cylindrical surface equispaced within said first concentric surface to receive the voice coil securely in axial alignment therewith.

4. A method as set forth in claim 3 wherein said step of forming said frame element comprises: further forming said frame element to include similar mating shapes to receive each of said diaphragm element first and second annular portions and first and second concentric surfaces in secure juxtaposition.