US2423037A

US2423037A - Electrodynamic loud-speaker

Info

Publication number: US2423037A
Application number: US561776A
Authority: US
Inventors: John F Marquis; Carleton T Weibler
Original assignee: OPERADIO Manufacturing CO
Current assignee: OPERADIO Manufacturing CO
Priority date: 1944-11-03
Filing date: 1944-11-03
Publication date: 1947-06-24
Anticipated expiration: 1964-06-24
Also published as: GB604159A

Description

June 24, 1947.

J. F. MARQUIS ET AL ELECTRODYNAMIG LOUD-SPEAKER Filed Nm). s, 1944 Patented June 24, 1947 UNITED STATES PATENT OFFICE Charles, Ill.,A assignors ing Co., St. Charles, Iii

to Operadio Manufactura corporation of Illinois application November 3, 1944, serial' No. 561,776 4 Claims. (C1. 17a-1155) This invention relates to an acoustic transducer,l 'commonly termed a loud speaker, and employed as an element of a radio receiver or of a public address system.

n object of the invention is to provide new and improved acoustic transducer, together with an expeditious method of assembling the same,

Another object of the invention is to reduce the overall depth, as compared 4with that of the conventional acoustic transducer in which the magnetic motor is mounted behind the diaphragm.-

Itis also an object ofthe invention to provide a transducer having its magnetic motor assembly disposed in front of the diaphragm without requiring any supporting braces or Webs for said motor at the forward side of the diaphragm;

A further object of the invention is the reduc tion of manufacturing cost by the elimination of .the conventional 'arms and other parts usually required for supporting the magneticY motor in front of the diaphragm.

More specifically, the invention provides a suhst'antial frame or housing disposed behind the diaphragms'together with means for rigidly sup` porting the permanent magnet or electromagneticmotor from the central portion of this house ing, the diaphragm being provided with a central aperture through which a supporting connection extends to carry the motor at a position in front of the diaphragm.

Other objects and advantages of the invention will appear from thefollowing description taken in connection with the drawings in which,

Fig. 1 is a substantially axial-sectional View of a transducer or loud speaker embodying; this in vention and provided type O'f motor-l Fig. 2 is av sectional; view similar to Fig. l., but with portions broken` away; showing an electromagnetic motor mounted in accordance with the principles of the invention.

Fig. 3 is aV front view or elevation o'f the vstructure shown in Fig; 1.

Fig. 4 is an axial sectional view showing step in the assembly process. for centering the opening'in the diaphragm and positioning thev voice coil in accordance with a definite standard.

Fig. 5 is a fragmentary axial section taken substantially at the same plane as Figs. 1v and 2, showing a modified securing means for the magnet ic motor- 4 Fig;..6 is a fragmentary sectional view similar to Fig, 5, showing another modification 'of the se curing means.

with a permanent magnet Fig. 7 is also a fragmentary sectionalview similar to Fig. 5, showing a further modification.

While the invention is susceptible of various modifications and alternative constructions, the embodiments shown in the drawing and described hereinafter are by way of illustration only, and it is not intended that the invention be limited thereto or thereby, but .that all modifications and alternative constructions falling within the scope of the invention be included herein as defined by the claims.

In Fig. 1, the supporting housing is shown at I, being of frusto-conical form and terminating in an outer flange 2 to which the periphery of the conical diaphragm 3 is adhesively attached. The central portion of the housing l is a flat circular wall Il reinforced by a disk 5 which may be of somewhat heavier stock than the remainder of the housing I to add rigidity to the back wall 4, and which is secured theretov by any conventional method such as welding or riveting.

The diaphragm 3 is formed with a central opening surrounded by a short integral collar or ilange 3a, and a centering member in the form of a crimped or corrugated flexible diaphragm, is adhesively secured to this collar 3a, the peripheral portion 5a of the centering member being secured to a shoulder Ia of the housing I. Said housing I may be, and frequently is, made with substantial cut-out areas, giving it the nature of a spider rather than an enclosing housing, and when thus constructed is sometimes termed basket; but, if preferred, the conical wall of the part I may be continuous, and for the purpose of this invention it is immaterial which design is employed for this part.

In the central opening of the diaphragm 3 there is secured a tubular support 'l which may be of paper or other non-magnetic material having its upper end adhesively fastened to the inner surface of the collar 3a of the diaphragm and carrying at its lower end the voice coil 8 which acts as the armature of the magnetic motor by which the diaphragm 3 is vibrated. Terminals or lead wires for the coil 8 are not shown in thefdravving, but it will be understood that such wires extend from theV c'oil to the radio receiver orl telephone system into which the speaker or transducer is connected.

Fig. 11 shows a permanentA magnet I0 which is preferably of the alloy typecomposed of the material known as A-lnico V or other suitable magnetic material and' a central polepiece II extends coeaxially from the magnet IIJ, being secured theretonby a screw I2. Thescrew also holds in place the back plate I3 which carries the cylindrical member I4 of the magnetic motor, said member acting as the opposite pole of the magnet and providing an annular air gap I5 in which the voice coil 8 is supported with operating clearance. The magnet Il and the part I4 are rigidly secured to the reinforced

back wall

4, 5 of the housing I by means of a clamping bolt or screw I6 extending through the central opening in said back wall and through an annular spacer member I1 of nonmagnetic material which is interposed between the back wall and the center pole II. Prefei ably, the end of the part II is reduced in diamn eter to t accurately within a recess in the mating end of the spacer I1, while said spacer is tted into a central opening in the back wall 4 which does not extend through the reinforcing member 5, but thus provides a centering recess in which the spacer I1 may be fitted and clamped by means of the screw I6. Preferably, the screw is provided with a locking washer I8 disposed between its head and the part 5.

The structure shown in Fig. 2 is substantially identical with that shown in Fig. 1 except that instead of the permanent magnet Ii), the motor includes an electromagnet having an inductor coil 20, and the central pole 2I extends throughout the depth of this coil and is shown with a reduced portion 22 which is riveted over the end plate I3 by which the outer pole I4 is carried. The remaining parts being similar to those shown in Fig. l, they are designated by corresponding reference numerals.

As indicated in Figs. 1 and 3, the flange 2 of the supporting housing terminates in an annular flange portion 2a which serves to center and confine the edge of the diaphragm 3 and a mounting gasket or cushion ring 23 which is adhesively fastened to this marginal part of the diaphragm in position to contact the face of a baille or panel on which the speaker may be mounted by bolts or screws passing through the parts 2, 3 and 23. In previous devices of this character in which the magnetic motor was mounted in front of the diaphragm adjacent its concave side, the motor was supported by radially extending arms or webs attached to the outer flange 2 of the housing and usually to secure a smooth and finished appearance it was necessary to notch or interrupt the gasket 23 to accommodate the ends of these arms. With the present structure, such supporting arms are eliminated and the additional work on the gasket 23, together with the labor of securing the supporting arms in position, is avoided.

To simplify the assembly and to insure not only that the magnetic motor will be properly centered and fitted within the voice coil, but also that it will be interchangeable with a re placement motor, if required, the special jig, shown in Fig. 4, may be employed in tting the diaphragm and voice coil into the housing. The voice coil 8 and its supporting cylinder 'I are fitted onto a plug 3B and the diaphragm and centering member 6 are then glued to the part 1 in their correct relative positions. The plug 3U includes a reduced portion 3I which fits into the central recess bf the' back wall 4, while a reduced threaded portion 32 extends through the central opening in the part 5 so that a wing nut 33 may be applied to clamp the plug 3i) in position during the period required for drying the glue which holds the parts 3, 6 and 1 together. As soon as the plug 30 has been inserted in the back wall the peripheral portion 6a of the centering member 6 may be glued in position on the shoulder I8L and the outer edge of the diaphragm 3 may be adhesively secured, if desired, in the cupped flange 2 of the housing, and may be clamped therein with the gasket 23 in position. At the end of the drying period the plug 30 is removed, thus leaving the central opening in the diaphragm 3 accurately positioned with respect to the central openings in the

back wall

4, 5 so that when a magnetic motor is installed it will be properly centered with respect to the diaphragm and the voice coil 8.

Fig. 5 shows a modified construction in which a spacer 40 is substituted for the spacer I1 and is formed with a conically tapered portion 4I ntting into a conical recess 42 in the plate 5x attached to the back wall 4. The bolt 43 thus draws the spacer 40 and the attached center pole 2| (or II) snugly into position, the end of the tapered portion 4I being made slightly underflush with respect to the outer surface of the plate 5X to insure that it will be drawn tightly into the conical socket 42 by the screw 43. Preferably, a relatively large clamp washer 44 is disposed under the head of the screw 43 to distribute the clamping pressure, and the lock washer 45 is included to hold the parts in adjusted position.

In the arrangement shown in Fig. 6 the nonmagnetic scaper 50 is fitted to the end of the center pole 2| (or l I) in the same manner as heretofore described, but the outer end of the spacer is threaded at 5I to engage corresponding threads in the plate 5y secured to the back wall 4. A lock nut 52 is then screwed onto the protruding threads 5I of the spacer. The screw 53 acts independently of these parts to perform the single function of securing the spacer 50 to the center pole 2|, and a lock washer 54 is provided to prevent loosening of this connection in operation.

Fig. 7 shows a further modication in which the non-magnetic spacer 60 on the pole 2| (or I I) includes a reduced portion 6I which ts snugly in a central opening in the plate 5 secured to the back 4. This reduced partion 6I is slightly underflush with respect to the outer face of the plate 5c to insure being drawn snugly into position by the clamp screw 62 which operates against a clamping washer 63 and is provided with a lock washer 64 directly under its head.

It will be seen that with any of the structures herein described, or with modications involving the same principles, the magnetic motor will be firmly and rigidly supported at the front side of the diaphragm so as to occupy space within the cavity of the diaphragm, thus providing a very compact structure as compared with transducers in which the motor is mounted behind the diaphragm; but that this arrangement does not require the use of supporting arms extending radially from the magnetic motor to the rim of the housing and thus projecting in front of the diaphragm and more or less impairing the propagation of sound therefrom. It will also be evident that with the standardized positioning of the cen-v tral opening in the diaphragm and in the voice coil which is rendered possible by use of the assembly plug herein described, any properly constructed motor may be fitted accurately into place so as to function efficiently with this assembly, and if repair or replacement of the motor should become necessary it can be readily removed and remounted or replaced with equal accuracy and with a minimum of time and skill.

It will be understood that if the supporting housing is made of magnetic material, such as steel, the spacer Il, (or 40, 50 or 6D) will be preferably formed of non-magnetic material, such as brass oraluminum, and in that case the screw l1 (or 43, 53 or 62) should also be of non-magnetic material. If the housing itself is non-magnetic, the other parts may be madeof steel, although it will still be preferable to have ythem of non-magnetic metal so that the polar flux will tend to be concentrated in the vicinity of the voice coil.

We claim as our invention:

1. A loud speaker comprising a rigid unitary supporting housing having the general outline of the frustum of a cone, said housing having a wall at the small end and having accurately finished supporting means at said wall, a sub-assembly comprising a voice coil support, speaker diaphragm and cylindrical Voice coil, said speaker diaphragm being of the conical type with the small end joined to said voice coil, means for securing the large end of said speaker diaphragm to the large end of said housing, means for securing said Voice coil support to the housing in an accurate position with respect to the finished supporting means of said housing Wall to accurately pre-position said voice coil, a two-piece field structure comprising an axial pole piece and annular pole piece, said two pole pieces having accurately nished surfaces dening an annular air gap adjacent one end of said aXial pole piece, means for rigidly supporting said annular pole piece solely from said axial pole piece at the other end of said axial pole piece, said axial pole piece having the one end thereof accurately nished to cooperate with the finished supporting means at said housing wall and means for rigidly supporting said axial pole piece at said one end only from said housing Wall, said field structure being adapted to be symmetrically disposed within the space enclosed by said housing with the accurately finished housing part and axial pole end cooperating to provide an, inverted dynamic speaker assembled in preadjusted centered relation.

2. The structure of claim 1 wherein said means for maintaining said field structure against said housing comprises readily removable locking means accessible from the outside of the small end of the housing.

3. The structure of claim 1 wherein said housing is shaped to provide an annular ange adjacent to and symmetrical with said wall and wherein said Voice coil support is secured to said flange.

4. The structure of claim 1 wherein said housing is shaped to provide an annular flange adjacent to and symmetrical with said wall and wherein said voice coil support is a solid annular member having the outer end secured to said flange with said housing forming an enclosed air chamber between said voice coil support and housing end wall.

JOHN F. MARQUIS. CARLETON T. WEIBLER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,808,297 Dempster June 2, 1932 1,820,585 Tolerton Aug. 25, 1931 1,886,816 Jensen Nov. 8, 1932 2,186,576 Cornwell Jan. 9, 1940 1,941,476 Jensen Jan. 2, 1934 1,941,477 Jensen Jan. 2, 1934 1,952,357 Blumlein et al Mar. 27, 1934 1,970,038 Bowier et al Aug. 14, 1934