US2740959A

US2740959A - Electromagnetic sound producing device

Info

Publication number: US2740959A
Application number: US469385A
Authority: US
Inventors: White Joe
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1954-11-17
Filing date: 1954-11-17
Publication date: 1956-04-03
Anticipated expiration: 1973-04-03

Description

April 3, 1956 J, w TE 2,740,959

ELECTROMAGNETIC SOUND PRODUCING DEVICE Filed Nov. 17, 1954 2 Sheets-Sheet l O X x 22 INVENTOR.

Joe White His Attorney April 3, 1956 J. WHITE ELECTROMAGNETIC SOUND PRODUCING DEVICE Filed Nov. 17, 1954 2 Sheets-Sheex 2 Mun 3 3g 56 Wm so 44 H 1?. 58 28 Fig. 3

f E 54 @v- V 70 INSULATION INSULATION Fig. 4

INVENTOR. Joe 65 BY His Affomey United States Patent ELECTROMAGNETIC SOUND PRODUCING DEVICE Joe White, Anderson, Ind, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application November 17, 1954, Serial No. 462,385

2 Claims. (Cl. 340-388) This invention relates to sound signals and more particularly to an improved electromagnetic assembly for use in a horn.

It is an object of the present invention to reduce contact arcing as caused by induced currents in the electromagnet of a horn.

It is a further object to reduce the rate of fiux change in an electromagnet of a horn so that the effect of the electromagnet on the armature will continue after the current to the windings of the electromagnet is interrupted.

It is another object of the present invention to eliminate the conventional arc suppressing resistances in a direct current horn assembly so as to provide a lower cost horn assembly that will operate with higher voltages.

In carrying out the above objects it is another object of the present invention to include a metallic disc between a portion of the coil windings and magnetic core of the electromagnet for a horn assembly.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Figure l is a side view of a horn embodying the present invention.

Figure 2 is a top view of the horn shown in Figure 1 with the horn cover removed.

Figure 3 is a view, partly in section, of the horn taken along line 3--3 in Figure 1.

Figure 4 is an exploded view in perspective showing the parts of the magnet assembly for a horn according to the present invention.

In the drawings the numeral designates an improved horn assembly which may be assembled of the parts and method described in Patent 2,677,875, filed March 11, 1949, and assigned to the assignee of the present invention. The horn shown in the drawings is formed with a projector shell 22 and a backshell 24 which provides an enclosure for the power plant of the horn. The power plant for the horn which vibrates the diaphragm 26, which is suitably secured between the projector 22 and the base plate 28, is mounted on the base plate 28 and includes an electromagnet assembly 30 which moves an armature assembly 32 in response to the opening and closing of an electric circuit as controlied by the contact assembly 34.

The armature assembly 32, shown in Figure 3, comprises a rod 36 and an armature 38. The rod 36 extends through a bore 40 in the laminated pole assembly 42 of the electromagnet assembly 30. The armature 38 is secured to one end of the rod 36 and overlays the central portion 44 of the electromagnet assembly 30 wherein bore 4%} is located. The end 46 of the rod 36 which extends through the bore 40 is suitably secured to the diaphragm 26 so as to vibrate the diaphragm 26 when the armature 38 and the rod 36 are moved by the electromagnet assembly 30. The end 48 of rod 36 has a threaded nut adjustably located to engage and move the movable contact 50 which is normally in engagement with the stationary contact 52 of the circuit breaker assembly 34 which is fully described in the previously referred to patent to interrupt the flow of current to the electromagnet assembly 30.

The

contact points

50 and 52 are normally closed and connected in series with the coil windings 54 of the electromagnet assembly 30 and are opened mechanically as the armature 38 moves toward the pole 42 in response to the current flowing through the coil winding 54. When the current through the coil winding 54 is interrupted by the opening of

contacts

50 and 52, the armature returns to its original position due to the spring-back action of the diaphragm 26. This return movement permits the

points

50 and 52 to close and again complete the electric circuit. This action is repeated many times per second which results in a rapid vibration of the diaphragm.

The present invention is directly to an improvement in the electromagnet assembly 30 which is clearly shown in Figure 4 and comprises a laminated pole assembly 42, a coil winding 54, a pair of formed insulating members 56, an insulating disc 58 and a metallic disc 60, which will hereinafter be described.

The laminated pole assembly 42 comprises a plurality of E-shaped laminations of magnetic iron 62 and steel plates 63 which are suitably secured to and form the outer layers for the laminated iron plates 62. The E-shape of the pole assembly 42 defines a pair of spaced arms 64 which are integrally connected to the center portion 44. The plates 63 are also provided with arms 65 whereby the assembly is secured to the base plate 28. In the assembly of the electromagnet 30, the insulating members 56, suitably formed as shown, are placed between the arms 64 of the E-shaped laminated magnetic pole so that the center portion 44 is embraced by a double thickness of portions 69 of the insulating paper and the U-shaped portions 70 are received between the arms 64 and center portion 44. Before the insulating members 56 are in position, the metallic disc 60 is placed in position between the insulating members 56 and the pole assembly 42. The disc 6-0 is formed of a conductive metal such as aluminum so as to fit between anns 64 and preferably has a shape which corresponds to the coil windings 54 and has a central aperture 66 which surrounds the central portion 44 of the magnetic pole. The disc 60 is separated from the coil windings 54 by the insulating members 56 and an insulating disc 50, which has a similar configuration to the disc 60. When the coil winding 54 is in position in the pole assembly 39 it is securely held when flaps 68 of the insulating members 56 are bent over the outer surface of the coil winding 54 and when tangs 70, formed on the outer plates 63, are downwardly bent over the insulating members 56 as clearly seen in Figure 3.

The conventional type of horn for 6 and 12 volts normally utilizes a resistor in parallel with contacts to limit the arcing. it has been discovered that the shorting washer around the flux path will reduce the arcing of the contacts almost as effectively as the resistor and at less expense. For voltages higher than 12 volts, the resistor across the contacts is not sufficient, and is normally augmented with a condenser in parallel with the resistor across the contacts. The present invention also utilizes a condenser across the contacts in combination with a shorting washer around the flux path for horns designed to operate at voltages above 12 volts. The effect of the shorted turn is accomplished by the metal disc 60 in the electro-magnet assembly 3%.

The current flowing through coil winding 54 induces a field of magnetic flux in the pole assembly 42. This flux attracts and causes the armature 30 to move so Fat-elated Apr. 3, 1956 that the engagement between contacts 54. and 52 is broken. The breaking of the engagement between the

contacts

50 and 52 causes the current flow through the coil winding 54 to be temporarily halted. When the flow of current through the coil winding 54 ceases, field of flux around the pole assembly instantly begins to change or decay. This decay of flux induces a potential in the coil windings 54- which causes the contact arcing. The decay of flux also induces a current in the disc 6% so that it acts like a shorted turn and opposes the flux change. This opposition to the flux ch ge tends to sustain the flux held against its normal d y. This result is particularly desirable in a horn electromagnet. This reduced rate of flux change at the moment the coil winding 54 circuit is opened, permits the magnetic effect of the pole assembly 42 on the armature to continue for a short period after the contacts 5@ and 52 are opened and thus allows the electromagnet 39 to exert a pull while the armature assembly 32 is coasting toward the end of its travel. flux decay as accomplished by the shorted turn by sustaining the flux field also reduces the arcing at the contacts 5t) and 52 so a to make the requirement for the conventional resistance unnecessary. The above described device is particularly uselul when horns are operated at voltages higher than the conventional 12 volts and in combination with a condenser across the contact points, has been successfully utilized with horns of the type described which operate at 36 or more volts. The utilization of a shorted turn in a horn also requires less space than the conventional resistance so that the overall size of the horn may be reduced if desired without sacrifice of qualities.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In an electromagnetic sound producing apparatus adapted to be energized by a direct current, the combination comprising; a magnetic core having an integral base portion, a coil winding juxtaposed adjacent the base The lower rate of and surrounding said core and adapted to induce a magnetic flux therein when said winding is energized, a pair of separable contacts adapted to interrupt the energization of said windings, an armature adapted to be moved by the flux of said core, a diaphragm operatively connected with said armature adapted to be vibrated in response to the movements of said armature, and a metallic disc disposed at right angles to said core and adjacent the base of said core and in electrical contact therewith and insulated from said winding adapted to retard the rate of flux decay in said core and reduce the arcing between said contacts when the contacts separate.

2. In an electromagnetic sound producing device adapted to be energized by a direct current, the combination comprising; a U-shaped magnetic core having a raised central portion extending from the base of and disposed between the arms of said U, a coil winding positioned between and insulated from the arms of said core and embracing said central portion adapted to induce a magnetic flux in said core when said winding is energized, a pair of separable contacts adapted to interrupt the energization of said windings, a movable arrnature adapted to be moved by the flux of said core, a diaphragm operatively connected with said armature adapted to be vibrated in response to the movements of said armature, and a metallic disc disposed between the windings and the base of said core and having a central aperture adapted to embrace and contact the central portion of said core, and insulated from said winding and adapted to retard the rate of flux decay in said core and reduce the arcing between said contacts when the contacts separate.

References Cited in the file of this patent UNITED STATES PATENTS 2,022,367 Carbonaro Nov. 26, 1935 2,165,582 Scofield July 11, 1939 2,677,875 White et a1. May 11, 1952