Patent Application
20060024575
1. Technical Field
This invention relates generally to rechargeable battery packs, and more specifically to a rechargeable battery pack that is sealed such that the cell within the pack is protected from external gasses liquids.
2. Background Art
Traditional rechargeable battery packs have included a cell, circuitry and a plastic housing. The housing generally comes in two halves, for example a top and a bottom. The cell and circuit are placed into one half of the housing, and the other half is then attached with snaps or screws. The assembled battery pack may then be attached to a portable electronic device like a cellular telephone.
The problem with these prior art designs is that they are not water tight. As such, if liquids like coffee or tea are spilled on the battery packs, the liquid may penetrate the battery housing and compromise the reliability of the rechargeable cell disposed therein. Additionally, some environments, like certain manufacturing plants, have combustible gasses permeating the air. These gasses can be corrosive and may compromise the reliability of the cell and circuitry if allowed to enter a battery pack.
One prior art solution to this “gas and liquid permeability” problem is ultrasonic welding. Essentially, designers attempt to make the seams between housing halves air and water tight by welding them together rather than snapping or gluing them together.
The problem with this prior art solution is that ultrasonic welding requires housings that have thick walls. Generally speaking, the walls of the housing must be at least 2 millimeters thick to be ultrasonically welded. This wall thickness is often too thick for today's miniaturized electronic device.
A second problem with welding involves the exterior contacts. Welding only joins the perimeter seams where the two halves of the housing meet. Since all battery packs have external contacts as well, there is an additional need to seal the space around the contacts. Consequently, another housing part is needed to ensure that liquids and gasses do not penetrate the pack. This additional part increases both materials and labor costs, thereby making the battery pack more expensive.
There is thus a need for an improved battery pack that prevents liquids and gasses from penetrating the housing and compromising the reliability of the rechargeable cell and circuitry.
A preferred embodiment of the invention is now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.”
A battery pack is provided herein that prevents both liquids and gasses from penetrating the pack housing, thereby improving both the reliability and cycle live of the pack. The battery pack has a five sided housing, where one of the sides is longer than the others. A cell, with a circuit board coupled thereto, is placed within the housing. The housing and cell assembly are then placed in a mold. Low-temperature plastic is then drawn through the housing, thereby sealing the cell and circuit board within the five sided housing. The insert molding process makes the overall battery pack virtually impervious to liquids and gasses.
Turning now to
One of the sides 102-105, or the end 101, may include at least one aperture 107 for accommodating electrical contacts. In the exemplary embodiment illustrated in
As noted above, when ultrasonic welding is used to close two halves of the cell, the wall thickness 109 must be at least 2 mm. With the present invention, experimental results have shown that the wall thickness 109 may be less than 1 mm. As such, a battery pack made in accordance with the invention can be smaller in overall size than prior art packs. Thus, in one preferred embodiment of the invention, the sides 102-105 and end 101 are less than 1 mm thick. It will be clear to those of ordinary skill in the art having the benefit of this disclosure that the walls can be made thicker as applications warrant. Additionally, curves 110 and contours, as well as mating protrusions and detentes 11 may be added to allow the battery pack to couple to a host electronic device.
Turning now to
Next, the printed circuit board 300 includes electrical contacts, like contact block 306. Note that contact block 306 is a surface mount contact block that may be coupled to the board by automated equipment using a reflow solder process. Contact block 306 provides an electrical interface for voltage, current and data between the electronic device and the battery pack. Other devices, like memory 307, may also be included for battery identification and battery monitoring.
Turning now to
In this preferred embodiment, the printed circuit board has been attached to the cell 701 such that the printed circuit board 300 is perpendicular to the end 705 of the cell 701. This perpendicular arrangement is so the printed circuit board 300 will be positioned so as to be parallel with one of the sides of the housing. In the exemplary embodiment shown in the figures, the printed circuit board 300 will be parallel with the bottom (element 102 of
Turning now to
Turning now to
Turning now to
While the preferred embodiments of the invention have been illustrated and described, it is clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the following claims.
