Battery charging unit

A battery charging unit is disclosed for use in connection with a rechargeable, battery-powered device, such as a flashlight, of the type having a contact-foot that includes at least two contacts connected to the battery terminals and an asymmetrical end-profile. The battery charging unit has a receptacle that includes an asymmetrical aperture that corresponds to the end-profile of the contact-foot to ensure that proper electrical polarity is maintained between the charging unit and the contact-foot. The receptacle also includes a retractable barrier and retaining walls that are formed to ensure that the contact-foot is retained in the receptacle regardless of the orientation of the charging unit.

BACKGROUND OF THE INVENTION 
This invention relates to a battery charging unit for an electrical device 
having a rechargeable battery, and in particular, to such a battery 
charging unit having a novel receptacle for receiving a contact foot of 
the electrical device that maintains proper electrical polarity between 
the charging unit and the contact foot and that retains the contact foot 
in the charging unit regardless of the orientation of the charging unit. 
Portable electrical devices, such as flashlights and power tools, have come 
into great demand. Those devices often contain a rechargeable battery pack 
which is not readily removable from the device. Such a device usually has 
an external contact area which interfaces with a charging unit for 
charging or recharging the batteries in the device. In designing such 
devices and their corresponding charging units consideration must be given 
to assuring that the device is connected to the charging unit in a manner 
that assures proper electrical polarity between the contact area and the 
charging unit. Furthermore, since the designer cannot anticipate all of 
the different environments in which a charging unit may be installed, it 
is important that such a charging unit be able to retain the contact area 
of the device regardless of the orientation in which the charging unit may 
be mounted. Furthermore, in certain applications, such as those related to 
police and/or fire departments, the charging unit must be designed to 
withstand the rigors of such applications and yet be easy to use when time 
is of the essence. Heretofore, all of the foregoing design problems have 
not been adequately resolved in a single, known, charging unit. 
SUMMARY OF THE INVENTION 
The aforementioned problems associated with the known battery charging 
units are resolved to a large degree by the present invention which 
provides a battery charging unit for charging a rechargeable battery in a 
battery-powered device of the type having a contact-foot that includes at 
least two contacts connected to the battery terminals and an asymmetrical 
end-profile. In accordance: with one aspect of the present invention, the 
battery charging unit includes a receptacle for receiving the contact-foot 
of the battery-powered device such that the contact-foot is retained in 
the charging unit regardless of the orientation of the charging unit. To 
that end, the receptacle has first and second sidewalls and a retractable 
barrier which has a retracted position for permitting the contact-foot to 
slide into the receptacle and a protruding position for preventing the 
contact-foot from sliding out of the receptacle. 
In accordance with another aspect of the present invention, the first and 
second sidewalls form an asymmetrical aperture corresponding to the 
end-profile of the contact-foot to ensure that proper electrical polarity 
is maintained between the charging unit and the contact-foot.

DETAILED DESCRIPTION 
Referring now to the drawings and in particular to FIGS. 1 and 2, there is 
shown a preferred embodiment of a battery charger unit in accordance with 
the present invention. The recharger unit 10 has a pair of sidewalls 12a 
and 12b and a base 14 interconnecting the end-walls 12a and 12b at one end 
respectively thereof. The sidewalls 12a and 12b have respective angled 
portions 13a and 13b at the ends of sidewalls 12a and 12b distal from the 
base 14. The angle of deflection of angled portion 13a is greater than the 
angle of deflection of angled portion 13b thereby providing an 
asymmetrical or keyed channel. The end-walls 12a and 12b and base 14 are 
preferably formed of extruded metal, such as aluminum, in order to form a 
rigid, integral unit. It will be appreciated, however, that another 
suitable material, for example, a plastic or composite material, can also 
be used. 
An end-wall 16 is attached to one end of the battery charge unit 10 in 
order to close off the opening at that end. The end-wall 16 has a tapered 
shape that is congruent with the keyed channel defined by sidewalls 12a 
and 12b and base 14. 
The battery charger unit 10 also includes a support assembly 17 having a 
contact panel 18 and an end-panel 20 which are attached in perpendicular 
relation to each other at respective ends thereof. Angled finger portions 
21a and 21b extend from the end of end-panel 20 attached to contact panel 
18. Finger portion 21a has a deflection angle identical to that of angled 
portion 13a and finger portion 21b has a deflection angle identical to 
that of angled portion 13b. In this manner, the end panel 20 and the 
angled finger portions 21a and 21b define an aperture 24 that has the same 
asymmetry as the channel defined by sidewalls 12a and 12b. 
The contact panel 18, which is positioned between sidewalls 12a and 12b in 
spaced, parallel relation to base 14, has side edges 28a and 28b which are 
formed for sliding engagement with channels 30a and 30b formed in 
end-walls 12a and 12b, respectively, at a location adjacent the angled 
portions 13a and 13b. A tab 36 is formed in one end of contact panel 18 
and is dimensioned and positioned to fit in an opening 38 formed in 
end-wall 16. The contact panel 18 is dimensioned to fit snugly between 
sidewalls 12a and 12b when fully inserted in channels 30a and 30b. In this 
manner the support assembly 17 is securely mounted in the recharger unit 
10, rigidly spaces the sidewalls 12a and 12b, and thus adds to the 
rigidity of the unit. 
End-wall 16 and end-panel 20 are secured to the sidewalls 12a and 12b by 
fasteners such as screws 32 which are retained in the fastener receptacles 
34 formed in sidewalls 12a and 12b. As shown in FIG. 1, the contact panel 
18, sidewalls 12a and 12b, and end-wall 16 define a receptacle 35 having 
an asymmetrical or keyed aperture for receiving the contact foot of a 
rechargeable, battery-powered device. 
Referring now to FIGS. 3 and 4, a retractable stop 26 and retractable 
contacts 22a and 22b are mounted on contact panel 18. The retractable stop 
26 has a flat portion 40 adjacent the end panel 20, an inclined portion 42 
which inclines in a direction away from the aperture 24 toward end-wall 
16, and a stop-face 43 extending from the inclined portion 42 toward the 
contact panel 18. Stop-face 43 is preferably oriented perpendicularly to 
the plane of contact panel 18. Retractable stop 26 has a first or 
protruding position as shown in FIG. 4 and a second or retracted position 
where the inclined portion 42 and stop-face 43 are at or below the plane 
of the contact panel 18. In this manner, a contact foot can slide through 
the asymmetrical aperture 24 into the receptacle, but is prevented from 
sliding in the opposite direction, unless the retractable stop 26 is moved 
to its retracted position. The retractable stop 26 is maintained in the 
protruding position, its normal position, by a spring 44 mounted coaxially 
on a shaft 45. The shaft 45 and a spacer 48 which extend from the contact 
panel 18 also support a charging circuit board 46. 
The charging circuit board 46 includes a luminous indicating device such as 
light emitting diode (LED) 47 which indicates the status of the charging 
process during operation of the charging unit. In accordance with a 
preferred feature of the present invention, the LED 47 is located on 
circuit board 46 adjacent the end-panel 20 and directly below the 
retractable stop 26. Retractable stop 26 is preferably formed of 
transparent material such that the LED 47 can be seen through the 
retractable stop 26 as shown in FIG. 3, for example, It is contemplated 
that the charging unit in accordance with the present invention can be 
used with both fast-charge and slow-charge circuits. Such circuits are 
generally known in the art. When a fast-charge circuit is used, the 
circuit board 46 preferably includes a second LED to indicate when the 
fast charge mode is completed and the unit is in a charged or trickle 
charge mode. 
Retractable contacts 22a and 22b are disposed on contact panel 18 in spaced 
relation so as to coincide with the contacts in the contact-foot when the 
contact-foot is properly inserted in the receptacle 35. In the embodiment 
shown in FIG. 3, retractable contacts 22a and 22b are offset from the 
centerline A--A of contact panel 18 for that purpose. The asymmetry of the 
receptacle aperture 24 and the offset of the contacts assure correct 
polarity when the device to be recharged is inserted into the charging 
unit. The retractable contacts 22a and 22b are spring-loaded in contact 
sleeves 50a and 50b, respectively, which extend from contact panel 18 
toward the base 14. Retractable contacts 22a and 22b each have a first or 
protruding position in the absence of a contact foot in the receptacle and 
a second or retracted position when a contact foot is present in the 
receptacle. Preferably, the protruding portion of each contact has a 
rounded shape in order to facilitate sliding the contact foot thereover 
during insertion into and removal from the charging unit receptacle 35. 
As shown in FIG. 4, the contacts 22a and 22b have shafts 54a and 54b, 
respectively, which extend through the sleeves 50a and 50b, respectively. 
Retainer clips 52a and 52b are attached about the shafts 54a and 54b, 
respectively, to retain the contacts 22a and 22b in their respective 
sleeves. The retainer clips 52a and 52b are attached on the shafts 54a and 
54b to prevent the contacts 22a and 22b from protruding more than a 
preselected distance above the contact panel 18. The shafts 54a and 54b 
include terminal lugs 56a and 56b to which wire leads 57 and 58 are 
connected. For example, wire lead 57 connects contact 22b to the charging 
circuit board 46. Two wire leads 58 connect the charging circuit board 46 
and contact 22b to an external power source. 
Referring now to FIGS. 5 and 6, there is shown a preferred arrangement for 
connecting the wire leads 58 to an external power source. A jack 60 is 
mounted in an opening 62 in end-wall 16 adjacent the base 14. The jack 60 
is a two-conductor jack for mating with a two-conductor plug of the type 
connected to a conventional AC to DC transformer or connected directly to 
a DC voltage source. In an alternate embodiment as shown in FIG. 7, the 
wire leads 58 are connected directly to a cable 65 which passes through a 
wire gripping sleeve 64 mounted in end-wall 16. Cable 65 is hard-wired 
directly to an AC to DC transformer 66 of conventional design. 
Referring now to FIG. 8 of the drawings, there is shown the lower portion 
of a flashlight 86, having a flared contact foot 88 and a base 90, 
inserted in the receptacle 35 of the charging unit 10 according to the 
present invention. Because of the asymmetry of the end-profile of the 
contact foot 88 of flashlight 86, the contact foot 88 can be inserted 
properly through the asymmetrical aperture of the charger unit receptacle 
35 with only one orientation. Furthermore, the retractable stop 26 is in 
its protruding position which prevents the contact foot 88, and hence the 
flashlight 86, from sliding out of the receptacle 35 unless the 
retractable stop 26 is in its depressed position. It will be appreciated 
that, by virtue of the construction of battery charger unit 10, it can be 
mounted in virtually any orientation, vertically upright or inverted, or 
horizontally face-up or face-down, and the contact foot of flashlight 86 
is retained in the charging unit receptacle 35. 
In accordance with a further aspect of the present invention there is shown 
in FIGS. 9, 10 and 11 a preferred battery pack 70 for use in a 
battery-powered device, such as flashlight 86. As shown in FIG. 9, the 
battery pack 70 includes a base 72 and a battery support/holder 74 in 
which the batteries 76a and 76b are mounted. As shown in FIG. 10, the base 
72 of battery pack 70 has a pair of tabs 84 and 85. Tab 84 is narrower 
than tab 85, thereby providing a keyed arrangement for mounting the 
battery pack 70 in the flashlight base 90. The flashlight base 90 has 
notches 91a and 91b formed therein, notch 91a being positioned and 
dimensioned to receive tab 84 and notch 91b being positioned and 
dimensioned to receive tab 85. 
A pair of contacts 73a and 73b are preferably flush mounted on the base 72. 
As shown in FIG. 10, the contacts 73a and 73b are located along a 
centerline B--B of the base 72, but are offset from the centerline C--C of 
the flashlight base 90 because of the asymmetry of the contact foot 88. 
The base 72 of the battery pack 70 is retained in the flashlight 86 by 
means of retaining pins through tabs 84 and 85 and base 90. In a preferred 
arrangement as shown in FIG. 8, a retaining pin 92 is inserted through a 
borehole 94 formed in the base 90 on both sides of notch 91a. A borehole 
96 formed in tab 84 of base 72 aligns axially with the hole 94 to permit 
the pin 92 to pass through the base 90, through hole 94, and back into 
base 90. A similar arrangement is provided with respect to tab 85 of base 
72. 
In connection with a still further aspect of the present invention, there 
is shown in FIG. 11 a preferred circuit for the battery pack 70. A thermal 
fuse 80 is connected in series with a thermal contact 78 to the negative 
terminal of battery 76b. The positive terminal of battery 76b is connected 
to the negative terminal of battery 76a and a diode 82 is connected in 
series between the positive terminal of battery 76a and the positive 
polarity contact. A resistor 83 connected across the contacts 73a and 73b 
provides a load which can be sensed by the charging circuit in the 
recharger unit whereby the charging circuit determines the presence of the 
battery pack when it is inserted in the recharger receptacle to be 
recharged. The thermal contact 78 is used in a known manner to interrupt 
the charging current to the batteries when the temperature of the battery 
pack 70 exceeds a predetermined temperature limit. Thermal fuse 80 
performs a similar function should thermal contact 78 fail to operate 
properly. The diode 82 prevents inadvertent discharge of the batteries 76a 
and 76b through the contacts 73a and 73b of the battery pack 70. 
In view of the foregoing description and the accompanying drawings, some of 
the many novel features and advantages of the battery charging unit 
according to the present invention are now apparent. For example, a novel 
battery charging unit has been described which has a receptacle with an 
asymmetrical opening and a contact arrangement for assuring that a device 
to be recharged is connected to the charging unit with the proper 
polarity. The charging unit has retaining walls, which define the 
asymmetrical opening, and a retractable barrier to retain the contact foot 
of the rechargeable device, regardless of the orientation of the charging 
unit. The retractable barrier has an inclined portion that facilitates 
insertion of the contact foot into the charging unit receptacle, thereby 
permitting one-handed insertion of the rechargeable device. 
It will be recognized by those skilled in the art that changes or 
modifications may be made to the above-described without departing from 
the broad inventive concepts of the invention. It is understood, 
therefore, that the invention is not limited to the particular embodiments 
which are disclosed but is intended to cover all modifications and changes 
which are within the scope and spirit of the invention as defined in the 
appended claims.