US3354541A

US3354541A - Loudspeaker magnet structure and method of assembling same

Info

Publication number: US3354541A
Application number: US461285A
Authority: US
Inventors: John W Gosma
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1965-06-04
Filing date: 1965-06-04
Publication date: 1967-11-28
Anticipated expiration: 1984-11-28

Description

NOVL 28, 1967 w, os 7 3,354,541

LOUDSPEAKER MAGNET STRUCTURE AND METHOD OF ASSEMBLING SAME Filed June 4, 1965 J I N VEN TOR.

BY john 41/ 6051220 A TTORNEY v Patented Nov. 28, 1967 3,354,541 LQUDSPEAKER MAGNET STRUCTURE AND METHOD OF ASSEMBLING SAME John W. Gosma, Kokomo, Ind, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed June 4, 1965, Ser. No. 461,285 2 Claims. (Cl. 29607) This invention relates to loudspeaker magnet structure and the method of assembling the same.

The majority of current loudspeaker assemblies utilize permanent magnet structures to provide the field in which the voice coil is suspended and in which it moves to drive the diaphragm connected thereto to create and reproduce sound. Since stereo and multiple speaker outlets from a given receiver are now more common loudspeaker production is high and cost is an important factor. One further impetus to speaker production is due to the introduction on the market of stereo systems for automotive use that require four speakers.

It is an object in making this invention to provide a unitary magnet and casing assembly that is low in cost and simple to assemble with the frame for the speaker.

It is a further object in making this invention to provide a novel method of forming a magnet and casing for a loudspeaker through the application of a strong magnetic field causing the casing to wrap around the magnet and form a compact unitary assembly.

With these and other objects in view which will 'become apparent as the specification proceeds, my invention will be best understood by reference to the following specification and claims and the illustrations in the accompanying drawings, in which:

FIGURE 1 is a side elevational view of a loudspeaker assembly embodying the invention, parts being broken away and shown in section; and,

FIG. 2 is an exploded view showing the parts of the magnet assembly in spaced relation.

The basic drive unit in this instance is formed of a ceramic magnet 2 having a top pole plate 4 and a bottom pole plate 6. These magnets may be made of hard ferrites and are rather brittle requiring care in applying the housing or they might be cracked. The magnet 2 is of annular form having a central opening 8 therein. It is proposed to encase this basic assembly of the magnet with its top and bottom pole plates in a casing or housing of aluminum and then applying a strong magnetic field to cause the casing to wrap tightly around the subassembly to form a complete unitary member. Such a casing 10 is shown in the form of a cup having cylindrical side walls and a bottom surface but an open top. If it were attempted to assemble the magnet within the casing by folding over the upper edge either mechanically or by applying a strong magnetic field through the use of such a device as a Magneformer the ceramic magnet might be cracked. It is, therefore, necessary to apply some lining shock absorbent material to protect the same.

It has been found that a polyvinylchloride material works well in this instance and a layer of such material 12 is shown in the bottom of the cup or casing 10 in FIG. 2. The amount of polyvinylchloride material used should be sufficient to surround the magnet on the sides and extend a short distance out over the top edge in the final assembly. The casing 10 is, therefore, first filled to the desired point with the polyvinylchloride material or some similar material which is electrically insulating and will provide shock proofing. The lower plate 6, the magnet 2 and the upper plate 4 are then placed in the casing in sequence and properly located one upon the other. By slight pressure from the top the polyvinylchloride material will be forced up around the edges of the magnet parts and out over the top corner for a short distance to insulate and mount the magnet and poles. This subassembly is then placed in an oven at an elevated temperature and cured at, for example, 375, the temperature being determined by the material being used. This sets the polyvinylchloride so that it becomes rubbery and holds the magnet assembly in place.

This assembly is now placed in a Magneformer which is a well known commercial device capable of applying a strong magnetic field to deform material through discharge of a condenser. Upon actuation of the device the top edge of the casing 10 is folded in tightly over the magnet, as shown at 26 in FIG. 1, in a quick and single action to make a permanent magnet unit for a loudspeaker.

As shown on the drawing, the lower plate 6 has a central opening 14 which may be internally threaded and into which may 'be screwed a short stud 16 integral with a central core member 18. This is inserted into the central aperture to form a gap with the upper plate and an aperture into which the voice coil 20 of the speaker may project and in which it is supported. The top plate 4 of the speaker is also provided with a series of regularly spaced rivets 22 which when brought into juxtaposition with the frame 24 of the speaker are adapted to project into mating openings therein and then peened over to secure the magnet unit to the speaker frame. These could, of course, be drilled out and threaded and screws could be used for securing the unit as well as the riveted members.

It will be obvious that this is a very simple, fast and inexpensive manner in which to quickly form magnet assemblies for loudspeakers and to assemble the same to loudspeaker frames.

What is claimed is:

1. A method of making a permanent magnet assembly including the steps of taking a hollow deformable casing, filling it partly with an uncured insulating plastic, placing the parts forming the magnet and poles in sequence in the casing, pressing the parts down to displace the insulating plastic causing it to flow up around and slightly over the peripheral edge of the top of the same, applying heat to the assembly to cure the plastic material allowing the same to cool, applying an intense magnetic field to distort the case and fold it in on the magnet subassembly, the cured plastic protecting the magnet in the process.

2. The method as claimed in claim 1 in which the magnet is a ceramic magnet that is brittle and the uncured insulating plastic is polyvinylchloride.

References Cited UNITED STATES PATENTS 2,943,359 7/1960 Sussman 17452.6 X 3,214,511 10/1965 Franklin 29-421 X 3,251,015 5/1966 Denham 17452.6 X

JOHN F. CAMPBELL, Primary Examiner. C. E. HALL, Assistant Examiner.

Claims

1. A METHOD OF MAKING A PERMANENT MAGNET ASSEMBLY INCLUDING THE STEPS OF TAKING A HOLLOW DEFORMABLE CASING, FILLING IT PARTLY WITH AN UNCURED INSULATING PLASTIC, PLACING THE PARTS FORMING THE MAGNET AND POLES IN SEQUENCE IN THE CASING, PRESSING THE PARTS DOWN TO DISPLACE THE INSULATING PLASTIC CAUSING IT TO FLOW UP AROUND AND SLIGHTLY OVER THE PERIPHERAL EDGE OF THE TOP OF THE SAME, APPLYING HEAT TO THE ASSEMBLY TO CURE THE PLASTIC MATERIAL ALLOWING THE SAME TO COOL, APPLYING AN INTENSE