US2776413A

US2776413A - Core for choke coil or resistor

Info

Publication number: US2776413A
Application number: US224550A
Authority: US
Inventors: Edgar J Knouse
Original assignee: Quality Components Inc
Current assignee: Quality Components Inc
Priority date: 1951-05-04
Filing date: 1951-05-04
Publication date: 1957-01-01
Anticipated expiration: 1974-01-01

Description

r Jan.

E. J. KNOUSE CORE FOR CHOKE COIL OR RESISTOR Filed May 4, 1951 INVENTOR. Co/yar Maase.

CORE FOR CHOKE COIL R RESISTOR Edgar J. Knonse, St. Marys, Pa., assigner to Quality Coinponents, Incorporated, St. Marys, Pa., a corporation of Pennsylvania Application May 4, 1951, Serial No. 224,550

1 Claim. (Cl. 336-492) This invention relates generally to cores or forms for coils such as resistor or chokecoils and the like and more particularly to the construction of the core itself.

The core of this invention is an improvement over the core or forms as disclosed in the Hugh N. Veley Patent No. 2,355,611.

The principal object of this invention is the provision of a core or form for choke or resistance coils. These cores are ordinarily constructed from plastic insulating material such as glass, porcelain or thermoplastic or thermosetting resins and have leads with their ends secured therein and extending from the core at positions adjacent which the coil ends or connections pass.

The problem of locking the coil ends or connections to the core to prevent the coil from accidentally unwinding or shifting in position with a resulting change in impedance has long been recognized. When the core ends are molded with notched ends as disclosed and claimed by Voley, the coil end which is used as a connection is bent over the axial edge of the notch and passes straight to the lead around which it is wound and subsequently soldered. This notch extends almost to the lead and the tendency is to wrap the coil end to the lead at a distance from the end of the core as actually shown in Veley. ln production these coil ends are caused by the notch to be wound on the lead at a considerable distance from the end of the core. Such spacing will break the coil ends or coil connections when the leads are exed to apply them to a circuit and thus ruin the coil. if the coil is covered the break in the coil is not readily detected unless its circuit is checked.

To avoid this difficulty one is required to wind the coil ends or connections closely adjacent the end of the form so that no amount of flexing of the leads will cause the coil ends to break. This is accomplished by providing a slot in the end of the core, the bottom of which is spaced from the lead. A slot of this character provides longitudinal and not axially extending edges and only the cross sectional end of the slot is formed in the end of the core. The coil cannot be properly locked or anchored with this slot unless the wire is drawn over the bottom of the slot end and then wound on the lead closely adjacent the end of the core.

If a coil end is wound on the lead in spaced relation to the end of the core, the coil will not be anchored and will unwind and can be readily caught by visual inspection before the coils are coated or covered. Thus the actual position of this simple slot in the core prevents distruction of the coils by the mere flexing of their leads.

Again the slot extending longitudinally of the core may serve two other purposes. First, the reception of a plastic that holds the turns of the coil in place and interlocks the coil with the core. Secondly, the slot or a covered passage longitudinally of the core may be employed to receive a wire or other type of electrical core member means which is effective in changing the impedance of the coil. This electrical core member may extend part way nited States Patent Patented Jan. 1, 1957 ICC in or all the way through the coil and may be varied in size or metallic content to change the coil characteristics.

Other objects and advantages appear hereinafter n the following description and claim.

The accompanying drawings show, for the purpose of exemplication without limiting the invention or claim thereto, certain practical embodiments of this invention wherein:

Fig. l is an enlarged isometric view of a core having two leads and one slot comprising this invention.

Fig. 2 is an enlarged isometric view of a core having four leads and two slots.

Fig. 3 is a sectional view of an enlarged core with coil wound thereon and having two electrical core members therein.

Fig. 4 is an enlarged isometric View of a core having two end leads, two center leads and an outwardly open slot. f

Referring to Fig. l of the drawing the core 1 has the ends of the leads 2 and 3 embedded therein. ln this instance the leads are substantially axially of the core 1. The leads are usually constructed of tinned copper wire that may be flexed. Other kind of wire may be employed.

When the coil is to be wound thereon it must Withstand high temperatures. The core 1 is preferably made of a molded plastic material such as glass, porcelain or other ceramic material having insulating properties. Highly iluxing agents can be employed to mold and bake these ceramics without injury to the leads and in some instances the leads may be inserted after the core is baked.

Thermoplastic or thermosetting resins having insulating properties may be molded into these core forms if they are not to be subjected to high temperatures. This type of core is the most popular for high frequency circuits not involving high temperatures.

ln Fig. 1 the core 1 is provided with the slots 4 and 5 which are rectangular in cross section and preferably a little larger than the wire to be wound into coil form on the core, but the bottom of the slot should be spaced from the leads as shown. The cross section of the slot 5 is shown in the end 6 of the core and the edge of the bottom of the slot is spaced from the lead 3. These slots do not have to be perfect cross sections of squares, rectangulars or trapezoids but their edges adjacent the end face 6 should be well delined and preferably square.

ln the structure of Fig. 2 the core 10 has four independent leads insulated from each other. The leads 11-12 and 13-14 are held in substantial alignment with each other. Each lead has a slot 15, 16, 17 and 18, each slot with its bottom edge spaced from the lead with which it is to be employed.

ln the structure of Fig. 3 the core 20 has an upwardly open slot 21 extending all the way along the core. T he leads 22 and 23 are disposed in the center of the core with their heads 24 embedded in the molded plastic of the core. The bottom edges of the slot 21 at both ends of the core require the Wire 25 forming the coil to be kinked or bent thereover as shown and the coil ends or

connections

26 and 27 are closely adjacent the end faces of the core end are Wound around their

respective leads

22 and 23. Any amount of iiexing of these leads will not break these coil ends.

The slot 21 has the metal core member 28 forced into the bottom thereof. If wedged in tightly it will stay in place, but the Whole coil is dipped into a plastic such as varnish and baked to form a coating. This coating also lls the slots 21 and hardens between the adjacent turns of the coil and tightly adheres to the surface of the core in the slot and thus functions as a key or winding form for each wire as indicated at 30 to securely lock the coil on the form.

If the single short metallic electric core member 2S does not have suliicient choke effect, one or more passages 31 extending through the core may be provided and of suicient size to receive with a press t, the electric core member 32. The advantage of this core member is that it is spaced from the coil by the core material and may be shoved into the passage 31 at any deserved distance to give the proper choke eect after the coil has been coated or even when in use.

1n Fig. 4 the core 33 has four leads, two end leads 22-23 and two of which are intermediate 34 and 35 for taking off taps of a coil or the ends of two tandem coaxial coils. This core has the outwardly open slot 21 and the passage 31. The intermediate ends of taps connecting to the leads 34 and 35 do not need winding locking slots.

While, for clarity of explanation, certain embodiments of this invention have been shown and described, it is to be understood that this invention is capable of many modilcations and many changes inthe construction and arrangement of patrs may be made therein and certain parts may be employed Without the conjoint use of other parts and without departing from the spirit and scope of this invention.

I claim:

A coil comprising a small molded core of plastic material having terminals embedded therein and extending outwardly therefrom, a coil having its turns wound on said molded core, a passage in the form of an upwardly open slot in the surface of said molded core and extending longitudinally of the axis of the coil, said coil being wound over said slot with its ends connected to the respective terminals, a wire snugly fitting in said slot and spaced from said coil turns to effect the impedance of the same, and a plastic coating applied in a ilowa'ole state and when hardened to lock said wire in said slot and interlock the under side of the turns of the coil winding.

References Cited in the tile of this patent