US3336552A

US3336552A - Encapsulated electrical coil

Info

Publication number: US3336552A
Application number: US493731A
Authority: US
Inventors: Dhu Aine J Davis
Original assignee: Hermetic Coil Co Inc
Current assignee: Hermetic Coil Co Inc
Priority date: 1962-03-01
Filing date: 1965-10-07
Publication date: 1967-08-15
Anticipated expiration: 1984-08-15

Description

Original Filed March 1 1962 1%? D. A. J. DAVIS 3,336,552

ENCAPSULATED ELECTRI CAL COIL 2 Sheets-Sheet l ugy rm ar w I ma dfizsmga 15, 1%? D. A.J. DAVIS 3,336,552

ENCAPSULATED ELECTRICAL COIL Original Filed March 1, i962 2 Sheets-Sheet 2 United States Patent Ofiice 3,336,552 Patented Aug. 15, 1967 ENCAlPSlULATED ELECTRICAL COIL Dhu Aine ll. Davis, Wheaten, lll., assignor to Hermetic Coil Co., Inc, a corporation of Connecticut Griginal application Mar. 1, 1962, Ser. No. 176,579, now Patent No. 3,238,286, dated Mar. 1, 1966. Divided and this application Uct. 7, 1965, Ser. No. 493,731

3 Claims. (Cl. 336-96) ABSTRACT OF THE DISCLOSURE An encapsulated electrical coil including a coil form having a bobbin configuration With a coil receiving central portion and a pair of end discs defining a coil receiving channel within which a coil is wound with end wires of the winding extending therefrom. Terminal leads for the coil are supported by a unitary terminal mounting member including a base portion within the bobbin channel and provided With an arcuate inner surface in intimate engagement with the surface of the coil and a boss portion having a pair of recesses for receiving the terminal leads with a pair of holes through which the ends of the terminal leads pass for connection with the Winding end wires. An outer casing encloses the coil and terminal mounting member With the casing being sealed with the end discs of the bobbin form and With the terminal leads.

Ba'ckgronnd of the invention This application is a division of my application, Ser. No. 176,579, filed Mar. 1, 1962, now Patent No. 3,238,286 for Method for Manufacturing an Electrical Coil.

In some situations it is necessary that an electrical coil be sealed against moisture, and such a seal is often desirable even though it is not absolutely required. A coil which is sealed is not affected by variations in the humidity of its environment, has a longer life and has more stable electrical operating characteristics than an unsealed coil. Present coils are usually sealed by impregnating the coil with a sealing compound, as an epoxy resin. Impregnation procedures are often expensive and time consuming, particularly where it is necessary to carry the impregnation out in an evacuated atmosphere to insure that the impregnant fills all the spaces within the coil.

An object of this invention is the provision of an improved sealed or encapsulated coil having a terminal mounting member for receiving insulated terminal leads of the coil and a casing surrounding and sealing the coil and the mounting member.

One feature of the invention is the provision of an encapsulated electrical coil construction having a coil Wound on a form and engageable with a terminal mounting member, an outer casing sealing the coil and the mounting member. A further feature is that the outer casing has a frictional seal With generally planar exposed surfaces of the coil form.

Still another feature is that the coil construction includes a form having a bobbin-like configuration with a coil receiving central hub and a pair of end discs, a coil wound on the hub between the end discs, with the end discs having annular portions extending outwardly beyond the coil surface, and an outer casing for the coil having a body section between the end discs of the bobbin and in intimate contact with the coil and having locking portions overlying and sealed only with the annular portions of the bobbin end discs.

Yet a further feature is that the coil has insulated terminal leads affixed to a terminal mounting member carried by the coil and the outer casing encloses both the coil and the terminal mounting member.

Yet another further feature is that the mounting member carried by the coil has an arcuate surface in engagement with the coil windings, and an apertured bo-ss with recesses for receiving the insulated ends of the terminal leads, the inner conductor portions thereof passing through holes in the boss to the coil Winding.

Further features and advantages of the invention will readily be apparent from the following specification and from the'drawings, in which:

FIGURE 1 is an elevation of an encapsulated coil embodying the invention;

FIGURE 2 is a plan view thereof;

FIGURE 3 is an enlarged sectional view taken generally along the line 3-3 of FIGURE 2;

FIGURE 4 is a broken section taken generally along line 44 of FIGURE 3;

FIGURE 5 is a section through a mold apparatus embodying the invention;

FIGURE 6 is a transverse section taken generally along the line 6-6 of FIGURE 5; and

FIGURE 7 is an enlarged fragmentary view of a portion of the mold structure.

Electrical coils are often operated in an environment where they are subject to external conditions, as moisture, which may penetrate the windings of the coil and change the coils electrical characteristics or completely ruin it. With the novel coil construction of this invention, a coil may easily and inexpensively be sealed against external effects, and may even be operated under water.

Turning now to the drawings and more particularly to FIGURES 1 through 4, an illustrative embodiment of an encapsulated coil incorporating the invention is shown. A bobbin-like coil form 10 includes a coil receiving central portion or hub 11 having a bore 12 therethrough. A pair of disc-shaped end portions 13 and 14 extend outwardly from the portion 11 at either end thereof. The coil itself comprises a plurality of turns 15 of a suitable wire wound about the coil receiving central portion 11 and between the flange-like disc portions 13 and 14, with the outer layer of the windings being spaced an appreciable distance, as of the order of %g inc-hes in a coil 1%. inch in diameter inside the edges 16 and 17 of the discs.

The coil form is preferably of a molded plastic material, as nylon.

A pair of terminal leads 2,0 and 21, each having a suitable insulating covering 20a and 21a are connected with Wires 15a and 15b at the ends of winding 15. The terminal leads 20 and 21 are carried by and affixed to a terminal mounting member or yoke 23 which has a base portion 24 with an arcuate inner surface 25 that fits against the outer surface of winding 15. An enlarged or thickened boss portion 26 of the mounting member has a pair of recesses 27 therein to receive the end of the insulating coverings 20a and 21a of the terminal leads and is provided with holes 28 through which the inner conductors of the terminal leads pass.

The outer covering or jacket 30 for the coil is preferably formed, as by an injection molding operation to be described below, of a suitable insulating material. For example, the covering may be of the same nylon material as the coil form. The outer covering 30 has a main body portion 31 lying between the peripheral extensions of the bobbin end members 13 and 14. Annular cover portions 32 and 33 overlap the edges of the bobbin end members and interlock therewith, forming a tight mechanical seal.

lock between the encapsulant body and the coil form is adequate. However, where necessary, a physical bond may be provided by utilizing the proper temperature conditions during the molding operation, softening the coil form material so that the cover bonds with it.

Referring now to FIGURES 5, 6 and 7, a suitable mold for encapsulating the coil of FIGURES 1 through 4 is shown. The mold includes an outer mold member or block 35 shown resting on a surface 36. The mold is in two parts, 35a and 3517 which mate along a separation line 350. Extending through the mold is a centrally located bore 37 in which two further mold members 33 and 39 are slidably received. Mold member 38 comprises a cylindrical portion 38a filling the lower portion of bore 37 and having a centrally located upstanding rod portion 40. Mold member 39 is generally cylindrical in cross section and fills the upper portion of bore 37, having a central passage 39a in which rod portion 40 is received.

A coil to be encapsulated is inserted into the cavity of the mold, between the upper face 38b of the cylindrical portion 38a of mold member 38 and the lower face 3% of mold member 39. The terminal leads 20 and 21 of the coil extend outwardly through grooves formed in the mating faces of mold parts 35a and 3511 as best seen in FIGURE 5.

The coil to be encapsulated, i.e., the coil form and winding, is positioned in the mold cavity defined by the bore 37 through mold parts 35a and 35b, the upper face of portion 38a of mold part 38 and the lower face of mold part 39. The upper surface of portion 38a of mold part 38 sealingly engages the lower face of bobbin end member 14, while the lower face of mold part 39 sealingly engages the upper surface of bobbin end member 13. The respective upper and lower faces 38b and 39b terminate inside the peripheral edge of the bobbin end members, the mold parts forming annular channels 43 and 44, one associated with the bottom of the coil and the other with the top, within which the annular cover portions 33 and 32 are formed.

Encapsulating material is introduced into the mold cavity through a passage 46 which enters the mold cavity at a point substantially on a diameter of the coil passing through the point of juncture between the coil and the terminal leads therefor. The fluid encapsulating material flows around the coil in each direction and forms a solid body filling the mold cavity. The diametric relation between the inlet port and the coil terminals allows the material to flow evenly about each side of the coil, without obstruction of one path more than the other by the terminal leads and the terminal mounting structure. Where the encapsulating material may have a tendency to lift the ends of the terminal mounting yoke 23, the inlet passage is preferably located immediately adjacent the terminal lead structure, as shown in broken lines at 46.

The encapsulating material, which may be a suitable thermosetting plastic material, as nylon, is introduced into the mold from a heating chamber (not shown) through a connector 47. The heating chamber and material feeding apparatus maybe of any suitable construction.

In accordance with the invention, the winding is placed on the coil form in the usual manner by a suitable winding machine. The terminal leads and 21 are mounted in yoke of insulating material 23 which is then secured to the surface of winding 15, as with a doublefaced adhesive tape, or other suitable adhesive material. The ends 15a and 15b of the winding are then mechanically and electrically connected with the conductors of the terminal leads 20 and 21. The coil is placed in the mold cavity and the mold parts assembled as shown in FIGURE 5. Liquid encapsulating material is then intro duced into the mold under suitable conditions of temperature and pressure, to form the jacket 30 around the coil. As thermosetting plastic materials have a ten- 3 to ink slightly upon setting, a firm mechanical bond is achieved between the jacket casing, the coil support and the winding itself. If a physical bond between the encapsulating material and the coil form is desired, the temperature condition within the mold should be such that the coil form is softened upon the introduction of the liquid encapsulating material. Where necessary, the mold itself may be heated as by an electric element 50 carried in one of the mold parts.

It is important that a good mechanical seal be maintained between the mold parts and the 'coil support during the encapsulating operation, to prevent excessive flashing of the encapsulating material.

Where nylon is used as the encapsulating material, and it is desired to achieve a physical bond between the encapsulating coating and the coil support, the temperature of the mold should be of the order of Fahrenheit during injection. The injected molten nylon may have a temperature of the order of 500 Fahrenheit, the heat of the mold and of the molten nylon softening the bobbin, allowing the bobbin and covering to bond together. After the mold cavity is filled, it is allowed to cool, completing the bond between the covering and the coil form and causing the coating to shrink tightly about the winding 15.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. In an encapsulated coil having a bobbin with a coil receiving central portion and a pair of end discs, one at either end of the central portion, defining a coil receiving channel, a coil wound on the central portion of said form within said channel and having winding end wires extending therefrom and terminal leads for said coil with insulating coverings and inner conductors, the improvement comprising: a completely encapsulated unitary terminal mounting member of insulating material carried by said coil between said end discs, having a pair of recesses in which the ends of the insulating coverings of the terminal leads are received and from which the inner conductors of the terminal leads pass to points of connection with the end wires of the winding.

2. The encapsulated electrical coil construction of claim 1 wherein said unitary terminal mounting member comprises a base portion within said channel and provided with an arcuate inner surface in intimate engagement with the surface of said coil; a boss having a pair of recesses for receiving the ends of the insulating coverings of said terminal leads; and a pair of holes through which the inner conductors of said terminal leads pass for holding the leads for connection with said winding end wires.

3. The encapsulated coil construction of claim 2 wherein said boss is disposed on top of said base portion as the base portion engages said coil surface, said recesses being located on the outer periphery of said boss such that the terminal leads extend outwardly from the boss and away from said coil, and said holes extending from said recesses to a point at the side of said boss above said base portion for connection with the end wires of the winding.

References Cited UNITED STATES PATENTS 1,841,447 1/1932 Leslie. 2,471,869 5/ 1949 Gebel 336-206 X 2,479,400 8/1949 Pecoroni 336-206 X 2,775,742 12/1956 Bogue 33696 2,956,312 10/1960 Naimer 2642'72 3,121,192 2/1964 Tuzinski 174-52 X LEWIS H. MYERS, Primary Examiner.

E. GOLDBERG, Assistant Examiner.