Note: Descriptions are shown in the official language in which they were submitted.
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TERMINAL COVER FOR A BATTERY PACK
BACKGROUND OF THE INVENTION
This invention concerns the provision of covers or
shields for terminals of battery packs, as used in cordless
power tools and the like, for reducing the possibility of
;unintentional contact, particularly electrically conductive
contact, between a terminal and other materials or between two
terminals, when the pack is not housed in the tool.
The desirability of avoiding unintentional discharge of
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any charge present in the cells of the battery pack when
~- handling or disposing of the pack is well understood.
It is also known to create "throw away" power packs or
cartridges in which the battery pack cells are enclosed in a
housing which includes an end cap or caps of varying degrees
; 15 of elaboration so that the terminals of the power pack
:(typically at one end or at opposite ends of the pack) are, at
least to some degree, protected. But many such cartridges are
expensive to manufacture and use because of their complex
structure. Further, and typically, they are not space
efficient in that their outside dimensions or overall size may
,be substantially greater than that required for the cells of
the battery pack alone. Also, the cartridge housing may add
undesirable weight to the tool or appliance. See for example
U.S. Patents 4,091,187 Kaye and 3,956,019 Mabuchi.
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It is also known to encase the cells of a battery pack in
a thin plastic material as for example by the shrink wrap
process, at least partly so as to minimize the bulk of the
battery pack. See for example U.S. Patents 1,277,147 Armande,
and 4,166,53Z Tsuchida and German patent 2,735,293 Schroder.
But these disclosures do not suggest provision for maintaining
a cover or shielding~for the terminals of the pack once it has
been prepared for service andtor is about to be discarded.
;It is also known to provide simple inexpensive terminal
10 covers, perhaps of cardboard, to shield the terminals of a
battery pack when it is shipped or in storage before use. See
;for example U.S. Patents 1,176,467 Xoretzky and 1,779,767
Gillingham. But these covers are removed and discarded when
the battery pack is prepared for service and hence are not
15 available and in position when it is being handled or when it
is discarded.
An incomplete or partial solution to the problem of
terminal shielding or covering is offered in the disclosure of
British Patent 2,021,849 Ciliberti. The cylindrical side
20 walls of the female terminal of a conventional single 9 volt
cell are insulated by a plastic cover using~the shrink wrap
process.
SUMMARY OF THE INyENTION
;Accordingly it is an object of the present invention to
25 provide a terminal cover arrangement for a battery pack which
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: effectively shields the terminals of the pack from random
contact and which may remain in place permanently, from a time
. when the battery pack is first assembled through a time when
it may be discarded.
5This object may be achieved in the combination of the
cell or cells of the battery pack with at least one end cap
for the pack, the cap having at least one integral terminal
' cover, and an element, preferably pliable, for surrounding the
i~ cells of the pack and holding the end cap in place.
10 In a preferred embodimcnt the end cap may be in the form
` of a skirted cap, thermo-formed or vacuum formed of a thin
material, sized to slip over the end of the battery pack cell
assembly and including at least one integral, stiff, terminal
r~r: cover for enshrouding a terminal so that it is substantially
r,15 entirely shielded from random contact with other material.
,~Preferably the terminal cover has a specific shape to be
;compatible with the configuration of the terminal it covers so
as to help minimize any increase of volume of the pack over
the volume occupied by the unenclosed cells. The terminal
cover may be configured so that initially a given terminal is
entirely enclosed but the cover may also include a defined tip
or other feature which is readily removable or severable to
create an access opening of predetermined shape and size so as
to facilitate making an electrical connection to the terminal
even while the terminal still remains substantially enehrovded
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and unexposed.
In the preferred embodiment the at least one end cap may
be held or retained on the battery pack by a pliable wall
member wrapped around and gripping the cell or cells and
; 5 overlapping the end cap so as to hold it firmly in position.
The wall member may, in the preferred embodiment, comprise a
length of self-adhesive tape, circumferentially embracing both
the end cap and the walls of the cell or cells of the battery
pack and, especially in multi-cell packs, contributing to the
10 structural integrity of the pack as well as performing its
primary function of retaining the terminal shielding end caps.
It is an advantage of a terminal shielding system
according to the invention that the terminal covers may be of
sufficient stiffness to protect the covered terminal from
15 mechanical displacement as well as unintentional contact.
A particular advantage of the system of the invention is
that the normal "in service" condition of the battery pack and
a preferred condition for disposal are the same so that no
additional instructions concerning the shielding or covering
20 of terminals need be given with regard to an acceptable
disposal procedure.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side elevation of a battery pack according to
the invention with terminal covers in place.
Fig. 2 is an end elevation of the battery pack of Fig. 1
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taken approximately on line 2-2 of Fig. 1.
Fig. 3 is a side elevation of the right hand end cap of
; the battery pack of Fig. 1.
Fig. 4 is a partial enlarged cross sectional view taken
approximately on line 4-4 of Fig. 1 and showing a terminal
enclosed in a sealed terminal cover.
Fig. 5 is a view similar to Fig. 4 but with the tip of
the terminal cover removed to permit connection of an external
wire lead to the terminal.
Fig. 6 is an exploded view of an alternative embodiment
of the invention in which a plate-like end cap is retained
against the end of the twin cells of a battery pack by a
shrink wrap enc]osure.
Fig. 7 is an exploded simplified view of a second
15 alternative embodiment in which, in assembly, opposite end
caps telescopingly overlap and are bonded at the overlap.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The exemplary embodiment of the invention illustrated in
Figs. 1-5 is a disposable battery pack 10 for a cordless two
20 speed drill. Except for its enclosure 12 the battery pack is
generally conventional and consists of four cells 14 connected
in series in abutting pairs by a pair of connections 16 tone
shown in Fig. 1) and an end strap 18. External connection is
by battery pack terminals 20, 22 and 24. For hiyh speed
25 operation a drill motor (not shown) is connected in series
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with the four cells 14 by electrical connection to the
- terminals 20, 24. For low speed operation the motor is
- connected to terminals 20, 22.
The cells and terminals of the battery pack are
completely enclosed by an enclosure 12 which includes a pair
of end caps 26, 28 and a centrally disposed adhesive tape
sleeve 30 for holding the end caps 26, 28 on the cells 14.
End cap 26 has a pair of terminal covers 32, 34 while end cap
28 has a single terminal cover 36 but otherwise they are
lO similar in construction and function and only one need be
described.
End cap 28 is shown in some detail in Figs. 3-5 and its
cross sectional profile is shown in Fig. 2 where it is
apparent that the profiled side wall 38 of the end cap
15 conforms closely to the double cylindrical form of the side-
by-side cells 14 of the battery pack. The side wall 38 ends
in a short flared skirt 40. The terminal cover 36 is integral
with a flat end wall 42 which, in assembly, overlays the ends
of the cells 14. The terminal cover 36 is generally prismatic
20 in shape and is defined by a pair of opposite triangular side
walls 44, an upright end wall 46, and an inclined top wall 48.
End wall 46 and top wall 48 converge and their outer edges are
contiguous with a short hollow tip 50 which extends the full
width of the cover 36.
End caps 26, 28 are preferably made from a thin somewhat
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resilient material. The thinness and resilience minimizes the
bulk of the enclosed battery pack and makes feasible the use
of battery packs so enclosed in existing battery pack
housings, designed for the unenclosed pack. End caps 26, 2~
may be made for example from thin sheet material by a thermo
forming or vacuum forming process. Material thickness is
preferably less than 1 mm. Good results have been obtained
with end caps 26, 28 thermo-formed from clear polyvinyl
chloride sheet, 1/4 mm thick before forming. An advantageous
result of using this process is that, although there is some
thinning of material in the walls of the cap, substantially
the full original thickness is retained in the area of the
terminal cover 36 where structural strength is desirable.
Completion of the forming process is facilitated by the
"stepped" taper or draft of the side wall 38 and skirt 40 (The
slight outward taper of side wall 38 is not shown).
A variety of self-adhesive tape materials may suitably be
used to create the end cap retaining sleeve 30. Again thin
material is preferred to minimize the bulk of the battery
pack. An exemplary material is white polyvinyl chloride
adhesive tape of suitable width and 1/4 mm thick. The surface
; of the tape may usefully carry such information as battery
pack identification and suggestions for disposal and
recycling. '
For final assem~ly of the disposable battery pack lO the
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end caps 26, 28 are slipped over the ends of the cells 14 into
the positions shown in Fig. l. The preformed end caps are
sized to fit snugly against the walls of the cells but the
draft or taper of the skirts and side walls of the end caps
(such as skirt fio and side wall 38 of end cap 28~ which is
also required for manufacturing helps in guiding the end caps
onto the cells. ~ suitable adhesive tape is wrapped tightly
around the pack to form a sleeve 30, overlapping the side
walls of the end caps (such as side wall 38 of end cap 28) so
lO as to hold the end caps 26, 28 in position. Preferably two
layers of tape are wrapped around the cells and the tape
sleeve 30 so created also contributes to the structural
integrity of the battery pack 10.
If desired, the tape on one side of the battery pack may
15 be cut centrally and longitudinally and the cut ends pressed
down onto the battery cells and both caps to define a
"wireway" as indicated at 52 in Fig. 2 to accommodate, for
example, a lead from the drill power switch to terminal 22.
(See lead 54, shown only in Figure 5). As an alternative to
20 slitting the tape, and if tape of suitable material is used,
the tape may be deformed and stretched down into the bight
between the cells to create the wireway.
As now assembled all terminals of the battery pack and
~` particularly terminals 20, 22 and 24 are electrically and
25 mechanically insulated from all outside contact. The terminal
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covers 32, 34 and 36 compactly and quite closely confine the
terminals and, even though thin walled (as described above),
their box-like structure is rigid and strong enough to
withstand an acceptable level of physical abuse, as may be
established in appropriate tests such as drop testing.
; In the exemplary embodiment of Figs. 1-5 the prismatic
shape of the terminal covers 32, 34, 36 derives from the
particular configuration of the terminals 20, 22, 24 of this
battery pack. Without departing from the spirit of the
lO invention other shapes of terminal covers may of course be
used, to suit other configurations of terminal. But,
preferably, the form of the terminal cover should always make
feasible the provision of a removable or severable tip or
other feature, such as the hollow tip 50 of the present
15 embodiment, to establish an opening for providing external
access to the shielded terminal for making an electrical
connection.
In preparation for putting the battery pack 10 into
service the tips of the terminal covers, such as tip 50 of
20 terminal cover 36, are severed by a suitable shearing means so
as to create a rectangular opening 56 at the conjunction of
walls 46, 48 of the terminal cover and as seen best in Fig. 5.
In keeping with the invention, even after the tip 50 of the
terminal cover 36 is removed, the terminal 22 remains
" 25 substantially entirely covered by the terminal cover 36 and
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even the tip 58 of the terminal 22 remains within the walls of
the terminal cover and well away from the opening 56. To
complete electrical connection female terminal 60 on lead 54
is inserted through the opening 56 into telescoping engagement
with the male terminal 22. In other embodiments the
arrangement may of course bé reversed with the fixed terminal
being the female.
Fig. 6 illustrates, in an exploded view, an example of a
second embodiment of the invention. A two cell battery pack
lO 70 comprises a pair of cells 72 each with a generally upright
terminal 74. A terminal cover end cap 76 is configured and
sized to be placed against the top of the cells 72 so that
terminals 74 extend into the open ended terminal covers 78 of
the end cap. An enclosure for the battery pack is created by
15 shrink wrapping a thin plastic housing 80 onto the battery
pack so that a flange 82 of the shrink wrap housing engages
and holds the plate portion 84 of the end plate 76. The open
ended terminal covers 78 are significantly deeper than the
terminals 74 of the battery pack so that, in assembly, the
20 terminals 74 remain recessed in the covers 78 so as to
minimize the possibility of random outside contact of the
terminals.
The four cell battery pack illustrated, in exploded view,
in Fig. 7 exemplifies a third embodiment of the invention.
25 The four cell pack 90 comprises four cells 92 the upper two of
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which carry a pair of terminals 94. The enclosure for the
battery pack comprises upper and lower thermo-formed or molded
sleeves or end caps 96, 98 the upper of which includes a pair
of terminal covers 100. In assembly the close fitting sleeves
96, 98 are slipped over the battery pack 90 so that they
telescopingly overlap and their ends 102, 104 may be bonded
together, ultrasonically for example, at the overlap, to
create a permanent enclosure. This bonded joining of ends
102, 104, in effect, completes a sleeve, overlapping the
10 respective end caps 96, 98 so as to retain them on the cells
!92. In assembly the terminal covers 100 of the upper cap 96
register with the terminals 94 of the cells and effectively
shield the~ from random outside contact. As shown in Fig. 7,
the walls of the caps 96, 98, on at least one of their sides,
15 may partially conform to the cylindrical shape of the cells 92
so as to create a groove 106, usable as a wireway for an
electrical lead.
Battery pack enclosures according to the invention, and
as in the exemplary combinations described above,
J,'l 20 substantially entirely enclose the battery pack and,
iparticularly, potentially exposed terminals of the pack during
the life cycle of the pack including its disposal phase. The
extent of coverage is such that the possibility of inadvertent
contact between a terminal and an outside body is much
25 reduced. The configuration of the battery pack for use in
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operation is also a suitable one for disposal of the battery
pack so that no additional instructions need be given or
action taken with regard to shielding of terminals when the
pack is ready to be disposed of.
A limited number of embodiments has been described but
clearly the invention is adaptable to many configurations of
cell arrangement, cell number (including a single cell pack)
and terminal configuration.
In all embodiments materials used in covering the
10 terminals and retaining those covers on the cells of the
battery pack is of such thinness that enclosing the battery
pack according to the invention need not substantially
increase its bulk. And the simplicity of the enclosures make
them very inexpensive to manufacture. Thus enclosures
15 according to the invention may be used without incurring a
cost penalty or inconvenience from increasing the bulk of the
tool or appliance in which they are used. In many cases
existing battery packs may be enclosed in a manner according
to the invention and housed in their host tool or appliance
20 without modification of existing housings or receptacles in
the tool or appliance. The use of thin and pliable or
somewhat resilient materials for the enclosures enhances the
potential compatibility of "retrofitted" enclosures to battery
packs for use in existing housings or receptacles.
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