Power transformer

A universal power transformer (101) is for connection to an AC power source and produces a regulated DC voltage at an output thereof. The power transformer includes a power transformer housing (102) with a recess (114). A universal power converter circuit (313) is positioned in the housing. Connector prongs (108, 110) are electrically coupled to the circuit and are movably carried on the housing at a position adjacent the recess. The prongs move between an outwardly extending position, projecting from the housing for connection to a first type of power supply connector, and a retracted position, extending into the recess for storage during transport of the power transformer and for connection to an adapter (103-106) positioned in the recess, to connect to a second type of power supply connector.

FIELD OF THE INVENTION 
The present invention pertains to power transformers, and more particularly 
to power transformers of the type used with power supplies found in 
different regions of the world. 
BACKGROUND OF THE INVENTION 
Power transformers are used to convert an AC power supply of the type 
available in homes, offices, hotels and the like, via an ordinary wall 
outlet, to a DC power supply compatible with electronic devices, such as 
radio telephones, telephones, answering machines, calculators, computers, 
radios, and the like. These power transformers are used to reduce 
dependence upon batteries, or to provide charging energy for rechargeable 
batteries from available AC power sources. To provide the regulated power 
supply, the transformer includes a power converting circuit within a 
housing having a male connector positioned thereon. The male connector is 
for connection to a female connector of a main power supply wall outlet. 
Because power transformers are often used with portable devices, they have 
been developed to facilitate transport with the portable devices. One 
known transformer includes pivoting prongs that move into the transformer 
housing for storage during travel and pivot to an outwardly projecting 
position for connection to a wall outlet. These connectors have improved 
compactness when folded, to minimize the storage space that they require, 
thereby facilitating packing by travelers or commuters. 
A difficulty encountered by travelers is powering their electronic 
equipment from the main power supplies found in different regions of the 
world. This difficulty arises because power supplies in different 
countries have different voltages, currents, and supply frequency 
characteristics. They also have different wall outlet female connector 
configurations. Although power converter circuits have been developed 
which produce a regulated DC voltage (e.g., five volts) from most main 
power supply signals found throughout the world, accommodating the 
different female connectors has been more difficult. 
Typically, transformers have a male connector with prongs for one type of 
wall outlet. Adapters are employed to connect these connector prongs to 
other types of wall outlet female connectors. Such adapters have a female 
connector for receipt of the male connector prongs on the power 
transformer housing and a male connector for connection to the wall outlet 
female connector. A difficulty with these adapters is that they space the 
transformer housing from the wall outlet by at least the length of the 
prongs of the male connector on the power transformer housing. Because of 
this spacing, a substantial torque is exerted through the adapter to the 
wall outlet if a force is exerted against the transformer housing. 
Accordingly, it is desirable to provide an improved universal power 
transformer system.

DETAILED DESCRIPTION OF THE DRAWINGS 
A universal power transformer is for connection to a main power supply and 
produces a regulated output voltage at an output thereof. The power 
transformer includes a universal power converter circuit positioned in a 
housing. The housing includes a recess. A prong is electrically coupled to 
the circuit and is movably carried on the housing at a position adjacent 
the recess. The prongs move between an outwardly extending position, 
projecting from the housing for connection to a first type of power supply 
wall outlet, and a retracted position, extending into the recess for 
storage during transport of the power transformer and for connection to an 
adapter received in the recess. The adapter is employed to connect the 
power transformer to a second type of power supply outlet. 
A power transformer system 100 (FIG. 1) includes a power transformer 101, 
and a plurality of adapters 103-106. The power transformer 101 includes a 
power transformer housing 102 having a front wall 112 with a recess, or 
channel, 114 therein. Connector prongs 108 and 110, which together provide 
a male connector, are mounted on the power transformer housing 102 
proximate recess 114. The connector prongs are movingly positioned in 
association with recess 114. When in an outwardly projecting position, 
extending orthogonally from wall 112 as shown in solid in FIG. 1, the 
prongs are positioned to be inserted into a first type of power outlet (a 
110 volt alternating current (AC) wall outlet of the type used in the 
United States of America). In a retracted, or collapsed, position, 
illustrated in solid in FIG. 2, connector prongs 108 and 110 extend into 
recess 114. In this position they are stored for transport or for 
connection to one of adapters 103-106 received in the recess, as described 
in greater detail hereinbelow. 
The power transformer housing 102 (FIG. 1) is generally rectangular, 
including a front wall 112, a right side wall 113, a bottom wall 115, and 
a top wall 119 (best shown in FIG. 2). A planar back wall 107, opposite 
front wall 112, and a left side wall 109, identical to right side wall 
113, are not shown. The power transformer housing 102 is manufactured of 
any suitable material, such as a dielectric material, and may for example 
be a molded polymer. The housing is preferably constructed in two shells 
117, 118 that define a hollow interior when interconnected. The shells are 
interconnected using an adhesive, snap connectors (not shown), threaded 
fasteners (not shown), or the like. The shells 117 and 118 define a 
cylindrical hollow 315 for receipt of an axle 316 which rotates therein. 
The recess 114 is formed in the front wall 112 and the top wall 119, as 
best shown in FIG. 2. The recess is preferably configured as a channel, 
having a wide lower volume defined by a recess front wall 216 extending in 
a plane substantially parallel to transformer front wall 112, side walls 
217 and 219 extending orthogonally from recess front wall 216 and 
terminating at projections 212 and 213. Projections 212 and 213 extend 
inwardly toward one another along front wall 112. The recess front wall 
216 includes a complementary latch mechanism 218. The latch mechanism 
includes an outer slide surface 222, an inner slide surface 224, and a 
catch 226 that extends between the outer slide and the inner slide 
surfaces. The channel 114 terminates at a recess stop wall 232. Axle 316 
is supported in the cylindrical hollow between stop wall 232 and an end 
wall 234. 
The power transformer housing 102 (FIG. 4) houses connector prongs 108 and 
110, a contact 409, a contact 411, and universal power converter circuit 
313. Connector prongs 108 and 110 include protrusions, or dimples, 417 and 
419 on the proximal, or axial, end 421. The distal end 423 of the prongs 
is for electrical connection with contacts of one type of wall outlet 
female connector. The connector prongs 108 and 110 are illustrated 
supported on an axle 316. The prongs are preferably fixedly secured to the 
axle such that the prongs and axle rotate together. The axle is 
manufactured of a suitable dielectric material, such as a molded polymer. 
The connector prongs 108 and 110 are manufactured of a suitable 
electrically conductive material, such as a beryllium-copper stamping. 
Contacts 409 (FIG. 4) and 411 are positioned in power transformer housing 
102 to contact protrusions 417 and 419 on connector prongs 108 and 110. 
Each of contacts 409 and 411 has a generally L shaped profile, including 
two orthogonal arms 501 (FIG. 4) and 503. The contacts are identical, 
accordingly only contact 409 is described in greater detail herein. Each 
arm 501 and 503 includes a respective detent 405 and 406 for indexed 
positioning of connector prong 108 (FIG. 3) when protrusion 417 is 
positioned in the detent. By engaging the detent, the protrusion 417 
releasable holds the connector prongs 108 and 110 in a predetermined 
orientation. This holding force helps the prong resist pivoting while the 
connector prong 108 is inserted into a female connector. Additionally, in 
the retracted position, the prong is held against pivoting out of the 
recess during travel. The contacts 409 and 411 are electrically connected 
to the connector prongs 108 and 110, respectively, in both the outwardly 
projecting position of FIG. I and the retracted position of FIG. 2. 
The contacts 409 (FIG. 4) and 411 are connected via two wire cable 321 to a 
universal power converter circuit 313. The power converter circuit may be 
implemented using any suitable conventional power transformer that 
produces a regulated output voltage (e.g., five volts DC) from a supply 
voltage input thereto. The supply voltage will typically be an AC voltage 
in the range between approximately 100 and 240 Volts AC. The universal 
power converter circuit 313 is thus of the type operable with many 
conventional main power supplies, including those available in most 
countries. The output of the universal power converter circuit 313, having 
the regulated voltage level thereon, is connected to a device 304 (FIG. 3) 
via cable 306. The device 304 may be a telephone, such as a cellular 
telephone, a cordless telephone, a radio, a calculator, a tape player, a 
portable computer, an answering machine, or the like. 
The contacts 409 and 411 are connected to cable 321 by any suitable means, 
such as weldmont 511 (FIG. 5), a connector (not shown), or the like. 
Adapter 104 (FIG. 1) is described herein. Adapter 104 includes base 121 and 
an upper body 151. The upper body 151 and base 121 are manufactured of a 
suitable material, such as integrally molded of a dielectric material. The 
adapter may be molded in two shells (not specifically shown) which are 
connected by suitable means (not shown) such as snap connectors, threaded 
fasteners, adhesive, or the like. The shells form two channels for receipt 
of the prongs 132 and 133, which extend through the body 151 into the base 
121. The prongs 132 and 133 are manufactured of a suitable conductive 
material, such as a metal alloy, and are electrically isolated from one 
another by the upper body. 
The base 121 is configured as a rail, which is keyed for receipt in recess 
114. The rails include a wide bottom for mating engagement with the lower 
portion 210 of recess 114. The base includes a wide bottom wall 161. The 
top 162 of the base is narrow to slide between the projections 212. 
Surfaces 163 and 164 are sloped to abut with projections 212 and 213. 
The base 121 includes an adapter latch 630 (FIG. 6) which is a resilient 
member projecting from adapter bottom wall 605. The latch includes a catch 
wall 636, a slide surface 638, and a recessed surface 640, on a lower 
surface thereof. As best illustrated in FIG. 6, a distal end 601 of the 
adapter latch 630 includes ribs which facilitate griping thereof. The 
latch 630 is sufficiently long that end 601 extends beyond top wall 119 
when end wall 161 abuts with stop wall 232. 
The base 121 forms a hollow shell that houses internal contacts 701 (FIG. 
7) and 703 positioned behind openings 130 and 131. These internal female 
contacts are mounted on the top surface of bottom wall 605 by suitable 
means (not shown). These contacts each include resilient arms 705 and 707 
to receive and electrically couple with connector prongs 108 and 110, 
respectively. The contacts each further includes resilient arms 709 and 
711 which receive and electrically couple to prongs 132 and 133. The 
contacts 701 and 703 are manufactured of any suitable electrically 
conductive material, such as a metal alloy. The electrical contacts are to 
electrically connect connector prongs 108 and 110 to prongs 132 and 133 
when the adapter is inserted into recess 114 while connector prongs 108 
and 110 are positioned in the recess, as described in greater detail 
hereinbelow. Thus, by connecting prongs 132 and 133 to a power source 
(wall outlet), power is supplied through the adapter 103 to connector 
prongs 108 and 110. 
It will be recognized by those skilled in the art that the adapters 103-106 
are similar in construction. Accordingly, adapters 103, 105, 106 will be 
described only briefly. The adapters 103, 105 and 106 (FIG. 1) include 
respective bases 120, 122, and 123 for mating engagement with recess 114. 
Each base is identical to base 121, such that it includes openings (not 
shown) identical to openings 130 and 131 and internal contacts identical 
to 701 and 703. The adapter 103 also includes adapter prongs 172 and 174 
on cylinder body 176 for insertion into a second type of power supply 
connector. Adapter 105 includes adapter prongs 178 and 180 for connection 
to a third type of power supply connector. Adapter 106 includes adapter 
prongs 182, 184, and 186 for connection to a fourth type of power supply 
connector. For each of these adapters, internal connectors include 
contacts for connecting the outwardly projecting connector prongs 108, 110 
when the respective bases 120-124 are inserted into the recess 114. 
Those skilled in the art will recognize that each of the adapters 103 (FIG. 
1) to 106 includes respective internal contacts 701 (FIG. 7) and 703 
positioned adjacent openings 130 and 131 connected to its respective 
prongs. Adapters 103, 104, 105 and 106 are adapted to be plugged into 
respective, different, types of conventional wall outlets (not shown). 
In operation, the user positions the connector prongs 108 and 110 in the 
outwardly projecting position of FIG. 1 to connect the power transformer 
housing 102 directly to a wall outlet 1100 (FIG. 11) which is compatible 
therewith. If the user need to move the prongs from recess 114, the user 
insert their finger into the recess 114 between the connector prongs 108 
and 110 to pull their finger out. The recess is sufficiently large to 
permit the user to provide a relatively high level of access to the 
prongs, and the force required to remove the prong protrusion form the 
index position created by protrusions 417, 419, and detents 405, 406, are 
sufficiently low, that the user does not need to have a firm grip on the 
prongs to move them. After use, the prongs can be folded back into the 
recess for storage or transport. Because the prongs are folded down, the 
transformer housing is relative rectangular in configuration, and the 
prongs are folded in such that they will not snag to help prevent damage 
to articles of clothing, the inside of a brief case, or other articles. 
If the wall outlet (not shown) to which the power transformer 101 (FIG. 1) 
is to be connected will not accommodate the connector prongs 108 and 110, 
the user selects an appropriate adapter 103-106 for this wall outlet. 
Although the insertion of the adapter will be described with respect to 
adapter 105, insertion of the other adapters is identical. When inserted 
into recess 114 (FIG. 8), the connector prongs 108 and 110 slide into, and 
make wiping electrical contact with, internal contacts 701 and 703 (FIG. 
7). Slide surface 538 (FIG. 2) of adapter latch 630 moves over outer slide 
surface 222 of complementary latch mechanism 218. When catch wall 636 is 
past catch 226, the tang moves into latched engagement shown in FIG. 7. In 
this position, the adapter is held firmly in position between the abutment 
of catch wall 636 and catch 226, and the abutment of wide bottom wall 161 
with stop wall 232. The stop walls prevent longitudinal axis sliding 
removal of the adapter. 
The end 601 extends beyond the top wall 119 sufficiently to allow the user 
to press the tang in direction A (FIG. 9) when the adapter 105 is fully 
inserted. To remove the adapter, the user presses adapter latch 630 in 
direction A, which moves catch wall 636 above catch 226. This allows the 
adapter to be slid longitudinally out of the recess 114. 
The bases 120-123 of adapters 103-106 fit snugly within the recess 114. 
This snug fit provides friction between the adapter and the power 
transformer housing 102, which helps hold the adapter in and prevents 
movement of the adapter in the recess. Internal contacts 701 and 703 
engaging connector prongs 108 and 110 provide additional frictional force 
against sliding removal of the adapter. The catch 226 and the 
complementary latching mechanism 218 lock adapters 103-106 in recess 114. 
When fully inserted, the adapter bases 120-123 are held against stop wall 
232, which positions the adapter at a predetermined location. The adapter 
is thus firmly held in the recess 114. 
With the adapter 105 inserted into the power transformer housing 102, the 
transformer housing and adapter are plugged into the wall outlet 1200 
(FIG. 12), compatible with this adapter. Because the adapter is inserted 
into the transformer housing, the adapter is positioned away from the 
wall, but is rather substantially flush to the wall. Surface 116 of front 
wall 112 is positioned against the wall outlet to provide stability 
against twisting when the connector prongs 108 and 110 are plugged into 
the wall outlet. 
Prior art adapters 1301 used with prior art power transformers 1303, such 
as that shown in FIG. 13, extend a significant distance from the wall. 
This spacing results from the adapter 1301 having to accommodate the full 
length of the prongs 1304 between the transformer housing 1312 and the 
wall outlet 1300. The immediate invention provides a more stable wall 
connection, which produces less torque in the internal contacts of the 
wall outlet if the transformer housing is bumped while it is connected to 
the wall outlet. 
Thus it can be seen that a power transform is disclosed which is readily 
transportable in a compact, easy to pack, configuration that protect the 
prongs of the male connector. The transformer includes one pair of 
contacts which may be folded out for connection to a compatible wall 
outlets without having to carry adapters therefor. The transformer 
receives adapters into a recess therein such that the distance between the 
transformer housing and the wall is minimal. This helps hold the power 
transformer in the wall and protects the wall outlet. 
The illustrated adapters 103 include a base received in the recess 114, 
such that the adapters are at least partially received in the recess. The 
adapters may be the same size as, or smaller than, the recess such that 
the entire adapter is received in the recess. This allows the power 
transformer and adapter to be spaced from the wall by a distance no 
greater than the power transformer without the adapter attached.