US3577110A

US3577110A - Transformer having a wound core around linear conductors

Info

Publication number: US3577110A
Application number: US823326A
Authority: US
Inventors: Robert L Arntz; John R Marker Jr
Original assignee: Dominion Electric Corp
Current assignee: Dominion Electric Corp
Priority date: 1969-05-09
Filing date: 1969-05-09
Publication date: 1971-05-04
Anticipated expiration: 1988-05-04

Abstract

A transformer having a pair of insulated wires disposed generally adjacent and parallel to each other, one wire being the primary and the other wire being the secondary of the transformer, said insulated wires being wrapped by a film of insulating material. The wrapped wires have a ferrous foil, coated with an insulating film, wrapped in several layers tightly therearound. The assembly of wrapped wires with foil therearound is bound together by a binder. The inner margin of the foil is adhered to the outer margin of the film of insulating material to anchor it and the outer margin of the foil is adhered to the binder. The binder is turned inward at the axially spaced ends of the transformer to protect the foil at those ends. A method of making the transformer is disclosed, including the steps of disposing the insulated wires as stated, wrapping the insulation material therearound, wrapping the foil therearound, and binding the wrapped foil in place.

Description

United States Patent [72] Inventors Robert L. Arntz;

John R. Marker, J r., Mansfield, Ohio [21] Appl. No. 823,326

[22] Filed May 9, 1969 [45] Patented May 4, 1971 [73] Assignee Dominion Electric Corporation Mansfield, Ohio [54] TRANSFORMER HAVING A WOUND CORE AROUND LINEAR CONDUCTORS 4 Claims, 2 Drawing Figs.

[52] U.S. Cl 336/175, 336/213, 336/219 [51] Int.Cl 1101f 17/06 [50] Field ofSearch 336/173, 174, 175,219,213; 178/45; 174/102, 107, 105, 36, 1 17.1

[56] References Cited UNlTED STATES PATENTS 476,816 6/1892 Pfannkuche 336/175X 1,763,150 6/1930 Hebrew 336/175 2,519,495 8/1950 Nesbitt et a1 336/219X Primary ExaminerThomas J. Kozma Attorney-Woodling, Krost, Granger and Rust ABSTRACT: A transformer having a pair of insulated wires disposed generally adjacent and parallel to each other, one wire being the primary and the other wire being the secondary of the transformer, said insulated wires being wrapped by a film of insulating material. The wrapped wires have a ferrous foil, coated with an insulating film, wrapped in several layers tightly therearound. The assembly of wrapped wires with foil therearound is bound together by a binder. The inner margin of the foil is adhered to the outer margin of the film of insulating material to anchor it and the outer margin of the foil is adhered to the binder. The binder is turned inward at the axially spaced ends of the transformer to protect the foil at those ends. A method of making the transformer is disclosed, including the steps of disposing the insulated wires as stated, wrapping the insulation material therearound, wrapping the foil therearound, and binding the wrapped foil in place.

PATENI'EUMAY 4197: 3,577,110

INVENTORS. P05 E RT L .A KN Tl JOHN E. MAEKEE JE.

. l TRANSFORMER HAVING A WOUND CORE AROUND 1 LINEAR CONDUCTORS An object of our invention is to provide an improved transformer particularly adapted for isolating two circuits in an electric appliance.

-Another object is the provision for an economically built transformer providing means for both isolating electric circuits and for transfonning the electrical energy from one circuit to the other.

Another object is the provision of an improved method for building an electric transformer that is both efficient and economical.

Another object is the provision of an electric transformer having a relatively long length and relatively small diameter or transverse dimension so as to adapt itself to limited space in an appliance such as along the adjoining walls of an electric toaster.

Other objects and a fuller understanding of this invention maybe had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a longitudinal view, partially in section, of our improved transformer in the preferred form thereof; and

FIG. 2 is an enlarged cross-sectional line 2-2 of FIG. 1.

Our transformer has two electric wires 11 and 12 disposed substantially parallel to each other. Each of these wires is of the usual multistrand type, as depicted for example in FIG. 2. In the embodiment illustrated, wire 11 is denoted as the primary wire 'of the transformer and wire 12 as the secondary wire of the transfonner. It is understood, of course, that this could be in the reverse order depending upon the transform ing characteristics desired in the ultimate structure.

Wire 11 has the usual insulation 13 of rubberlike material extending fully therearound, the outermost surface of the insulation 13 having a fabric outer layer molded therewith in the usual manner. Also disposed entirely around the wire 12 is an insulation 14 of rubberlike material. The outermost surface of the insulation 14 is covered by a fabric coating 16 molded therewith.- The wires 11 and 12 and the insulations, made up ofl3 ad15 aroundwire 11 and made up of 14 and 16 around wire 12, are constructed in the usual and well-known manner. Wrapped around both of the insulated wires is a sheet of pliable electrical insulating plastic material 17. A suitable plastic material for this purposeis known under the trademark Mylar". Mylar" is the registered trademark of E. 1. DuPont de Nemours & Company for its polyester film. It is relatively thin pliable film having good electrical insulating characteristics. Preferably, the innermost marginal edge of the plastic sheet 17 is adhered by a suitable adhesive to the outer surface of one of the insulated wires; for example, the innermost marginal edge portion of sheet 17 is shown adhered to the fabric coating 16 around the insulation 14 of wire 12. At least there is one complete turn around both of the insulated wires and the sheet 17 overlaps itself to provide for a complete covering around the two wires.

Next wound around the assembly of the insulated wires and the sheet 17 wrapped therearound is a plurality of layers of a ferrous foil 18. Preferably, the foil 18 is of a suitable steel appropriate for a transformer and preferably has a thickness of on the order of about 0.002 inch to about 0.004 inch. The foil should be thin and flexible enough to be rolled tightly in concentric adjacent layers around the assembly of insulated wires.

Before being so wrapped around the assembly, the steel foil is coated on both sides with an epoxy phenolic or other suitable electric insulating material which is thin and flexible enough to maintain its insulating characteristics while being bent in conformity with the foil as it is tightly wrapped around in the form shown.

' Preferably, we anchor the inner marginal edge portion of the foil l8 to the outer marginal edge portion of the sheet 17.

' By having the several layers of material adhered to each other as suggested a tight wrap is obtained whereby the several view taken through the layers are closely adjacent to each other and in interengagement, except for the coating thereon, as shown in the enlarged view of FIG. 2.

To provide for the required flexibility of the foil 18 to accommodate itself to the structure shown, the steel foil may be annealed or otherwise treated prior to being coated with the epoxy phenolic.

The tightly wrapped layers of foil 18 are held in such tightly wrapped position by a binder 19. The inner marginal edge portion of binder 19 is preferably adhered to the outer marginal edge portion of the foil 18 so as to provide an anchor for the inner edge portion of binder, 19. Binder 19 is preferably a sheet of resin impregnated fabric material which is flexible and strong enough to provide the binding function of holding the entire assembly together in the position shown in FIGS. 1 and 2. The outer binder 19 preferably extends along the length of the layers of foil 18 and somewhat beyond the ends thereof. The opposite extending ends of the binder 19 are then crimped radially inward as shown in FIG. 1 .to substantially seal and enclose the interior of the transformer against moisture. Also the binder 19 provides electrical insulation around the assembly of ferrous foil 18 about the two insulated wires. Our invention includes the method'herein described as well as the resulting transformer. A very economically fabricated transformer is thus built and which transformer is particularly adaptable for such purposes as isolation of two circuits or for providing electrical transformation of energy in an economical and simple manner. The transformer is also particularly adaptable to fit into confined spaces requiring a relatively long transformer with a relatively minimum transverse dimension. For example, the diameter or transverse dimension of the transformer illustrated in the drawings is seen as being but a relatively small fraction of the overall length of the transformer. A particular advantage of our transformer is found in its use as an isolating transformer in an electric bread toaster wherein it is desired to minimize the opportunity for electric shock to the user by having a one circuit isolated from another circuit.

Although this invention has been described in its preferred form and preferred practice with a certain degree of particularity, it is understood that the present disclosure of the preferred form and preferred practice has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts and steps may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

The present disclosure includes that contained in the appended claims, as well as that of the foregoing description.

We claim:

1. An isolating transformer comprising the combination of a first length of wire providing the primary element of the transformer, a second length of wire providing the secondary element of the transformer, first insulating means insulating said primary element and secondary element from each other, second insulating means wound around both said primary element and secondary element along the length thereof, a sheet of ferrous foil outwardly of said second insulating means wound tightly in a plurality of overlying layers around said assembly of primary and secondary elements and said first and second insulating means, said wound foil requiring binding to maintain it in tightly wound position, and a flexible binder wrapped tightly around said wound sheet of ferrous foil to constrain and bind the same wound tightly around said assembly, said first insulating means comprising insulation completely around each of said first and second lengths of wire whereby the insulation between the two wire lengths includes the insulation on both said wire lengths, and in which second insulating means comprises a sheet of thin plastic film wound in a plurality of overlying layers around the insulated first and second wire lengths, said sheet of thin plastic film along its outer terminal margin being adhered to the inner terminal margin of said ferrous foil to anchor the same wound around the said assembly.

2. An isolating transformer as claimed in claim 1, and in which-said binder is a 'sheet of resin impregnated glass fiber fabric having its inner terminal margin adhered to the outer terminal margin of said sheet of ferrous foil, the binder tightly holding the ferrous foil wound around said assembly.

3. An isolating transformer as claimed in claim 2, and in which said ferrous foil is coated on both sides with an insulating film having the characteristics of an epoxy phenolic.

4. A transformer comprising a longitudinally extending primary wire, a longitudinally extending secondary wire disposed generally adjacent and parallel to said primary wire, each of said wires being covered by insulation, said wires being insulated from each other by the insulation on both the wires, a sheet of plastic film having good electrical insulating characbeing adhered to each other to anchor the inner margin of the ferrous foil, and the said binder and ferrous foil being adhered to each other to anchor the outer margin of the ferrous foil.

Claims

2. An isolating transformer as claimed in claim 1, and in which said binder is a sheet of resin impregnated glass fiber fabric having its inner terminal margin adhered to the outer terminal margin of said sheet of ferrous foil, the binder tightly holding the ferrous foil wound around said assembly.

4. A transformer comprising a longitudinally extending primary wire, a longitudinally extending secondary wire disposed generally adjacent and parallel to said primary wire, each of said wires being covered by insulation, said wires being insulated from each other by the insulation on both the wires, a sheet of plastic film having good electrical insulating characteristics wrapped around both said primary wire and secondary wire as a unit, a sheet of ferrous foil wrapped tightly around the assembly of primary wire and secondary wire wrapped with said plastic film, said wound foil requiring binding to maintain it in tightly wrapped position, and a flexible binder wrapped around the foil-wrapped assembly to hold the same together in tightly wound position, the ends of said wires protruding from opposite ends of the assembly to provide leads for the transformer, said plastic film and ferrous foil being adhered to each other to anchor the inner margin of the ferrous foil, and the said binder and ferrous foil being adhered to each other to anchor the outer margin of the ferrous foil.