WO2001013385A1

WO2001013385A1 - Encapsulated transformer

Info

Publication number: WO2001013385A1
Application number: PCT/ZA2000/000140
Authority: WO
Inventors: Branimir Jakovlejvic
Original assignee: Branimir Jakovlejvic
Priority date: 1999-08-19
Filing date: 2000-08-18
Publication date: 2001-02-22
Also published as: CN1269149C; HK1051437A1; CN1379907A; EP1256119B1; ATE429021T1; CA2420312A1; DE60042033D1; EP1256119A1; AU6805400A

Abstract

An encapsulated transformer assembly (20) comprises a transformer (30) enclosed by a transparent electricity insulating skin (32, 34). The transparent skin facilitates heat exchange resulting in more effective operation in use.

Description

ENCAPSULATED TRANSFORMER

TECHNICAL FIELD

THIS invention relates to transformers and other apparatus comprising

transformers, such as power supplies.

BACKGROUND ART

It is known electrically to insulate a transformer by centralizing the

transformer in an opaque plastic cap having a substantially rectilinear shape

and an open bottom and to fill the region between the transformer and

inside walls of the cap with an opaque insulating material. The material

normally forms a concave bottom wall in a region between the transformer

and a bottom of the cap. In use, heat is generated by the transformer and

since neither the cap nor the intermediate insulating material transmits heat

effectively, that heat is not dissipated effectively. This may cause damage

to the transformer or may at least give rise to higher electrical losses . This

problem is also encountered in other apparatus comprising transformers,

such as power supplies.

Furthermore, the aforementioned transformer assembly is normally mounted

on a printed circuit board by a plurality of legs extending from electrical

terminals on the transformer to a region beyond the aforementioned bottom of the cap. The cap is normally mounted on the board to abut against the

board and as a consequence, a cavity is formed between the board and the

aforementioned bottom wall. In use and as a result of variations in

temperature in the cavity, air-entraining moisture moves into and is trapped

in the cavity. Over a period of time, this moisture causes damage to the

printed circuit board.

OBJECTIVE OF THE INVENTION

Accordingly, it is an object of the present invention to provide apparatus

and a method of producing same with which the applicant believes the

aforementioned disadvantages may at least be alleviated.

SUMMARY OF THE INVENTION

According to the invention there is provided an electric assembly

comprising a transformer and a translucent electricity insulting cover

therefor.

The cover is preferably transparent. The transformer may also comprise a

transparent bobbin on which a core for the transformer and transformer

windings are provided. In one embodiment the cover may be in the form of a skin.

The skin may comprise a transparent outer shell of a rigid material and a

layer of a transparent filling material provided between the shell and the

transformer. The shell may comprise first and second body halves fitted

together to form the shell.

The skin may comprise outwardly extending protrusions, to provide a

clearance between the skin and a surface on which the assembly is

mounted in use.

In another embodiment, the cover may be in the form of a box and may

comprise a plurality of pins for mating with and making electrical contract

with a conventional socket arrangement.

The transformer may form part of power supply circuitry and the power

supply circuitry may comprise a first output which is accessible through the

cover. The power supply circuitry may further comprise a second output

which is in parallel with the first output and which is also accessible

through the cover. The circuitry may comprise a fuse, and the fuse is preferably provided in a

recess in the cover.

The cover may comprise a lid for opening and closing the recess.

Also included within the scope of the invention is a method of forming an

electric assembly, the method comprising the steps of:

providing a transformer; and

permanently enclosing the transformer in a translucent electricity

insulating cover.

The transformer may be enclosed by locating the transformer in a rigid

transparent shell.

The transformer may be located by providing a rigid transparent shell having

a shape substantially the same as a general shape of the transformer;

mounting the transformer in the shell so that a small clearance is defined

between substantially a whole of an outer surface of the transformer and

the shell; and filling the clearance with a transparent electricity insulating

material. BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS

The invention will now further be described, by way of example only, with

reference to the accompanying diagrams wherein:

figure 1 is a diagrammatic perspective view of a prior art transformer

assembly;

figure 2 is a diagrammatic exploded perspective view of a transformer

assembly according to the invention;

figure 3 is a diagrammatic perspective view of the assembly in figure 2,

in assembled form;

figure 4 is a diagrammatic perspective view from above of a power

supply assembly according to the invention;

figure 5 is a diagrammatic perspective view form below of the power

supply assembly; and

figure 6 is a basic block diagram of the power supply in figure 4.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

A prior art transformer assembly is generally designated by the reference

numeral 1 0 in figure 1 . The assembly comprises a transformer (not shown)

mounted in an opaque cap 1 2 defining an open bottom 14. A body of an

opaque thermosetting epoxy resin 1 6 is provided in the cap to embed the transformer, thereby to insulate it electrically and to mount it permanently

in the cap.

Four conductive legs 1 8 connected to terminals (not shown) of the

transformer extend beyond a concave bottom wall 1 7 formed by the resin

and also beyond the open bottom 1 4 of the cap and are used to connect

the transformer to external circuitry (also not shown) .

The disadvantages of this assembly are referred to in the introduction of

this specification.

A transformer assembly according to the invention is generally designated

by the reference numeral 20 in figure 2. The assembly comprises a

transformer 30 comprising a transparent bobbin 22 made of a suitable

plastics material. A stack 23 of magnetic material laminates extend

through and around the bobbin, to form the magnetic core of the

transformer. The primary winding 24 and the secondary winding 26 of the

transformer are provided on the bobbin in known manner. However, no

insulating tape is provided about the windings, as is the case in some

known transformers, and transformer assemblies. Conductive legs 28 are

connected to input and output terminals (not shown) of the transformer 30. The assembly further comprises first and second body halves 32, 34 of a

translucent, preferably transparent permanent shell 31 (shown in figure 3)

of a suitable rigid plastics material. The two body halves collectively form

the shell having a shape and configuration substantially similar to the

general external shape of the transformer 30. When assembled, there is

defined a small clearance between the shell 31 and the transformer 30

enclosed thereby. Second body half 34 defines an opening 36 in a center

region thereof.

When making the assembly and after the shell 31 has been formed by

clipping body halves 32 and 34 together, a transparent thermosetting

material is introduced into the shell via opening 36 to fill the clearance, to

form a thin layer between the transformer and shell and to displace air

inside the shell. The material may be introduced by means of a suction

mechanism and process. The material is then allowed to cure.

The assembly thus comprises a thin transparent skin 38 (shown in figure 3)

for the transformer constituted by the transparent layer 37 and the

transparent shell 31 . On body half 34, a plurality of externally extending protrusions or feet 33

are provided. When the assembly is mounted on a surface (not shown) the

feet ensures that there is a permanent clearance (also not shown) between

the shell 31 and the surface. This clearance improves heat exchange

between the assembly and the environment.

The legs 28 extend beyond the body half 34, so that the assembly 20 may

be mounted on printed circuit boards (not shown) in well known manner.

The feet 33 ensures that a permanent clearance is provided between the

assembly and the printed circuit board, to facilitate circulation of air

between the transformer and the board and which improves the dissipation

of heat generated by the transformer.

It is believed that with the transparent bobbin 22, no insulation type about

the windings (24, 26) and the thin transparent skin 38, heat generated by

the transformer is transmitted outwardly more effectively than is the case

with the aforementioned prior art transformers.

The assembly may define holes 40 in ear regions 42, 44, of the bobbin 22

and body half 34 respectively. These holes, which are easily accessible

from a region in line with the centre axes of the holes, could be used to mount the transponder on a chassis 46 by means of screws 48 or bolts and

nuts, for example.

Accordingly, the compact assembly according to the invention is suitable

for both so-called printed circuit board and chassis mount.

In figures 4 and 5, there is shown a power supply assembly 50 according

to the invention. The power supply assembly 50 comprises a transparent

or translucent cover in the form of a box 52 for power supply circuitry 54,

comprising a transformer 56. The cover 52 facilitates the transmission of

heat generated by the circuitry.

The cover comprises a plurality of pins 58 (two or three) for cooperating

with a conventional socket arrangement (not shown) of a mains power

supply network. In a base 52.1 of the cover, there is provided a cavity 60

for a replaceable fuse 62 connected in either a primary or secondary circuit

of the transformer. The cavity is openable and closeable by a removable lid

64.

The cover defines a first opening providing access to a first pair of DC

output terminals 66 from the power supply. A second pair of output terminals 68 connected in parallel with the first pair is also accessible

through the cover.

A block diagram of the power supply is shown in figure 6. The

aforementioned pins are designated 58 and are connected to protective

circuitry 70 comprising lightning protection circuitry and the primary

winding 72 of the transformer. A secondary winding 74 of the transformer

is connected to a voltage regulating circuit 76 and the regulating circuit is

connected to the output terminals 66 and 68. The fuse 62 may be

connected in the primary and/or the secondary circuit of the transformer.

It will be appreciated that there are many variations in detail on the

apparatus and method according to the invention without departing from

the scope and spirit of the appended claims.

Claims

1 . An electric assembly comprising a transformer and a translucent

electricity insulting permanent cover therefor.

2. An assembly as claimed in claim 1 wherein the cover is transparent.

3. An assembly as claimed in any one of the preceding claims wherein

the transformer comprises a transparent bobbin on which a core for

the transformer and transformer windings are provided.

4. An assembly as claimed in any one of the preceding claims wherein

the cover is in the form of a skin.

5. An assembly as claimed in claim 4 wherein the skin comprises a

transparent outer shell of a rigid material and a layer of a transparent

filling material provided between the shell and the transformer.

6. An assembly as claimed in claim 5 wherein the shell comprises first

and second body halves fitted together to form the shell.

7. An assembly as claimed in any one of claims 4 to 6 wherein the skin

comprises outwardly extending protrusions, to provide a clearance

between the skin and a surface on which the assembly is mounted in

use.

8. An assembly as claimed in any one of claims 1 to 3 wherein the

cover comprises a plurality of pins for mating with and making

electrical contract with a conventional socket arrangement.

9. An assembly as claimed in claim 8 wherein the transformer forms

part of power supply circuitry, the power supply circuitry comprising

a first output which is accessible through the cover.

1 0. An assembly as claimed in claim 9 wherein the power supply

circuitry comprises a second output which is in parallel with the first

output and also accessible through the cover.

1 1 . An assembly as claimed in any one of claims 9 and 1 0 wherein the

circuitry comprises a fuse and the fuse is provided in a recess in the

cover.

1 2. An assembly as claimed in claim 1 1 wherein the cover comprises a

lid for opening and closing the recess.

1 3. A method of forming an electric assembly, the method comprising

the steps of:

providing a transformer; and

permanently enclosing the transformer in a translucent

electricity insulating cover.

14. A method as claimed in claim 1 3 wherein the transformer is enclosed

by locating the transformer in a rigid transparent shell.

1 5. A method as claimed in claim 14 wherein the transformer is located

by providing a rigid transparent shell having a shape substantially the

same as a general shape of the transformer; mounting the

transformer in the shell so that a small clearance is defined between

substantially a whole of an outer surface of the transformer and the

shell; and filling the clearance with a transparent electricity insulating

material.

1 6. An electric assembly substantially as herein described with reference

to the accompanying diagrams.

17. An transformer assembly substantially as herein described with

reference to the accompanying diagrams.

1 8. A power supply assembly substantially as herein described with

reference to the accompanying diagrams.

1 9. A method of forming an electric assembly substantially as herein

described with reference to the accompanying diagrams.