Note: Descriptions are shown in the official language in which they were submitted.
1 CORDLESS TOOL BATTERY HOUSING AND CHARGING SYSTEM
Background of the Invention
The invention concerns the housing and recharging of
batteries for battery powered devices such as portable power
tools and certain kitchen and domestic appliances, and more
particularly a system in which a contained group of power
cells, commonly known as a battery pack, may be in-
serted into a device as a power source, and removed from the
device and inserted into a charger assembly for recharging.
The several advantages of cordless power for tools and
appliances have led to the development of a wide range of
sizes of power- or battery-pack. Zow powered units of two
or three cells have long been known. Much larger sizes are
becoming more common and there is already a potential demand
for units up to say twenty cells. Preferably one charger
should handle all sizes of battery pack.
It has been conventional to use chargers based on a step
down transformer. The inherent isolation of charger output
terminals and of batteries under charge from high charger in-
put voltages is an advantage. But transformer chargers are
essentially voltage sources and transformer size must be
closely related to the number of cells to be charged. With
some electronic circuitry the range of a given transformer
charger can be extended somewhat, but this is not generally
cost effective and a "universal" transformer charger, for
covering a wide range of battery pack sizes, is not feasible.
The capacitive charger, essentially a current source,
is not "cell dependent" in the way that a transformer charger
is. Hence it has been a potential alternative or replacement
for the transformer charger, but high capacitor cost has
hindered its introduction. However, recent developments in
capacitor design, notably the introduction of the metalized
film capacitor, makes its use in charger design cost effect-
ive. But to realize the potential contribution of the capaci-
for to the design of a more truly universal charger, charger
receptacle and terminal assembly design must preferably be
made compatible with battery packs not only varying in power
1
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1 size but also in physical size and configuration. At the
same time it must be recognized that the capacitor charger
is inherently non-isolated so that the charger and battery
pack terminals, and the cell terminals when under charge, are
at high voltage.
Hence, it has continued to be common practice to provide
a specific charger for each tool resulting in wasteful
duplication. In U.S. Patent No. 4,173,733, Sugalski suggests
a combination in which one charger design accepts at least
two configurations of holder) holding cells for charging.
But Sugalski does not deal with battery packs per se and in
his design, integrity or stability of the connection between
the cell holder and charger depend entirely on the button and
socket-type terminals connecting them, and at least before
connection, the terminals on both cell holder and charger are
exposed.
To adapt his charger to different battery packs,
Busch, in German Patent DE 2702129, accepts the inconvenience
of additional parts, providing a specific adapter for fitting
each of two styles of battery pack to the charger receptacle.
The charger terminals remain exposed at the bottom of the
charger receptacle.
Important elements in the control of a charging process
are, typically a device for sensing battery temperature
(often a thermistor is used), and an associated charging
indicator light. Normally the temperature sensor is closely
associated with one or more of the cells of the battery pack
and the entire charger/tool system is burdened with the
cost of providing a temperature sensor and possibility
indicator light for each battery pack, as in Sugalski.
In another example, Hashimoto, in German Patent DE 3144858
(Fig. 2), discloses a thermistor within the battery pack.
His configuration reguires an additional terminal on the
battery pack and on the charger to electrically connect the
thermistor with the charging circuit. Hernandez in U.S.
Patent 4,616,171 discloses a thermistor (Fig. 4a) project-
ing through an opening 120 in charger casing 121. Thermal
contact with batteries 206 of the battery pack 200 is made
~344~~~
1 through opening 212 (Fig. 6). This arrangement avoids the
duplication of control elements in the battery packs but
has the disadvantage of requiring potentially troublesome
openings in the charger and battery pack housings.
It is well known to provide the openings of electrical
power outlets with shutters or shields which impede acci-
dental contact with their live terminals. See for example
U.S. Patents 2,579,538 Bierce and 4,493,517 Hillary, both of
which disclose safety shutter arrangements in an outlet,
normally responsive only to the insertion of a conventional
mating plug. But similar provisions in charger/battery pack
combinations are not known.
Summary of the Invention
Accordingly it is a general object of the invention to
provide a battery pack and charger system for a line of power
tools and appliances which, compared with existing systems,
is simpler) safer and more convenient to operate and poten-
tially lower in manufacturing cost.
Another object of the invention is to provide a system
of cooperating charger receptacle and battery pack configura-
tions commensurate with the capacity of a single charge to
service battery packs of a wide range of power size.
A further object is to provide battery and charger
terminals which permit easy engagement, one with another,
but which are designed to minimize risks of inadvertent
shorting of either set of terminals, and of shock hazard
to personnel.
Another object is to improve system cost and convenience
by accommodating all charging control circuitry and control
elements in the charger assembly so as to avoid duplication
of such parts in the battery packs.
Another object of the invention is to provide a charger
design which includes a low cost, simple and efficient
assembly feature for maintaining alignment or registration
between related portions of the terminal assembly of the
charger.
These objects may be achieved in a preferred embodiment
in which a single charger assembly may accommodate either of
3
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1 at least two different configurations of battery pack, and a
range of power capacity or number of cells in each configura-
tion. To assist in meeting the objects of the invention,
the charger may be of a non-isolated type such as capacitive.
The charger assembly may have a two level receptacle for
receiving a battery pack. A larger, primary chamber guides
the connecting "nose" of the battery pack to a second smaller
chamber in its floor. A pedestal may extend upwardly from
the floor of the second chamber and a pair of output termi-
nals of the charger be recessed in the pedestal with their
contacts normally biased away from apertures in the upper
portion of the pedestal. Risk of dangerous contact through
inadvertent insertion of an object through the apertures is
thus minimized.
All battery packs may have identical or) as far as the
charger assembly is concerned, interchangeable terminal
blocks at the base of their nose portions for engagement
with the charger terminals. Each terminal block includes a
pair of terminals spaced apart and separated by an insulating
member somewhat longer than the terminals, virtually isolat-
ing the terminals one from the other. A shrouding wall
surrounds the terminals and divider wall so that chances of
accidental short circuiting contact across the terminals is
much reduced.
z5 Risk of accidental damaging contact with terminals is
also minimized when connecting the battery pack to the
charger. The walls of the charger receptacle guide the nose
of the battery pack so that its terminal block registers with
the charger terminal assembly. In the act of connecting, the
insulating wall of the battery pack terminal block actuates
the terminals of the charger assembly to bring them into
receiving and electrically conducting position relative to
the battery pack terminals. The depth of the primary chamber
of the charger assembly receptacle is such that before any
electrical contact is made between charger and battery pack
both terminal assemblies are made remote from external access
by the presence of the nose of the battery pack in the
receptacle. After connection, the shrouding wall of the
4
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1 battery pack terminal block surrounds the charger terminal
assembly pedestal in the lower chamber of the receptacle, and
the walls of the primary chamber provide support to maintain
the battery pack erect.
It is a feature of the invention that all battery packs
have a nose portion shape which mates with at least a portion
of the main chamber of the charger assembly receptacle in
such a way as to guide its terminal block into unique
registration, and also to accept support from the walls of
the receptacle for maintaining the battery pack erect and
ensuring the integrity of the connection between battery pack
and charger.
It is also a feature of the battery packs that in their
nose or base portions all battery cells are oriented axially
with respect to the receptacle. The nose portion may com
prise a single cell so that the nose portion occupies only
one side of the charger receptacle. An asymmetrical charger
terminal disposition facilitates this. Or, the nose portion
of the battery pack may comprise two or more side-by-side
cells, occupying more of or completely occupying the
receptacle. In either case, the battery pack terminal block
may abut a cell end, greatly facilitating the assembly opera-
tion of making electrical connection between cell and battery
pack terminal.
Battery cells in portions of the battery pack outside
the receptacle may be oriented to suit such requirements as
compatibility of the battery pack configuration with tool
shape or with a compactness requirement. For low powered
tools, placing two, three or four cells end-to-end in an
elongated generally cylindrical housing (a "stick pack") may
be convenient. For bigger tools and packs) holding say up to
20 cells, the cells beyond those in the receptacle may be
disposed transversely of the nose cells and stacked for a
compact configuration - one which facilitates manufacturing,
particularly with respect to electrical connection between
the various cells. Preferably the battery pack housing is
of rigid plastic with a specific housing for each power size
conforming quite closely to its particular cell subassembly
5
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1 configuration. Structural integrity of the cell subassembly
before insertion in its housing and insulation of the cell
subassembly within the housing may be enhanced by encasing
the cell subassembly in a tight fitting boot of a flexible
material.
In another aspect of the preferred embodiment a'
battery temperature sensor forming part of the charging
control circuit, is housed in the charger assembly in a
location apparently remote from the batteries. But the
sensor is carried by an electrically insulated metallic
portion of the charger terminal assembly and is in reliable
thermal contact with the batteries in the battery pack,
principally through the thermal conductivity of the re-
spective charger and battery pack terminal members. A visual
charging indicator associated with the charging control
circuit may also be housed in the charger assembly so that
costly duplication of charger control elements in the battery
packs is avoided.
In keeping with the invention, a desirable precision
in registration between terminal apertures (in an upper
portion of the charger housing) and the charger terminal
assembly (carried by a printed circuit board floatingly
supported by a lower portion of the charger housing) is
achieved. As the housing portions are brought together,
z5 the locating or positioning effect of a tapered pin in one of
the related elements, engaging a hole in the other brings the
printed circuit board and hence the terminal assembly into
precise alignment with the terminal apertures in the upper
portion of the housing.
Brief Description of the Drawings
Fig. 1 is a side view of a battery charger embodying
part of the invention.
Figs. 2 and 3 are respectively side views of first and
second embodiments of battery packs rechargeable by the
charger of Fig. 1.
Fig. 4 is a somewhat enlarged overhead view of the
charger of Fig. 1.
Fig. 5 is an enlarged cross section taken approximately
on line 5-5 of Fig. 4 showing details of the battery pack
0 receiving receptacle of the charger.
6
1~4~ti~2
Fig. 6 is a much enlarged partial cross section of
the charger taken approximately on line 6-6 of Fig. 4,
showing details of the charger terminal assembly and also
a portion of the terminal block of a battery pack in posi-
tion for connection with the charger.
Fig. 7 is an enlarged cross section of the charger
taken approximately on line 7-7 of Fig. 4 with a battery
pack connected and in a charging relationship.
Fig. 8 is an end view of the battery pack of Fig. 2.
Fig. g is a perspective view of the battery pack of
Fig. 2 as viewed from below.
Figs. 10 and 11 are bottom views showing the terminal
block arrangement of the battery packs of Figs. 2 and 3
respectively. In Figure 11 the relative position of the
charger receptacle walls is shown in phantom outline.
Fig. 12 includes bottom views of the terminal block
assemblies of battery packs of the first embodiment in two,
three and eight cell sizes (12a through c respectively) and
of the second embodiment in two and three cell sizes (12d,
12e) to show a sample of the key lockout pattern used to
limit the battery packs to connection only with compatible
tools.
Fig. 13 is a side view similar to Fig. 3 of a third
embodiment of battery pack.
Fig. 14 is an enlarged pictorial view of the terminal
block of the battery pack of Fig. 2.
Fig. 15 is an enlarged pictorial view of the thermistor
mounting clip of the charger assembly in contact with a
terminal pin of a battery pack.
Fig. 16 is an enlarged end view similar to Fig. 8
of the battery pack of Fig. 2) but cut away to show details
of the battery cell subassembly.
Fig. 17 is an enlarged view taken approximately on line
17-17 of Fig. 16 showing further details of the battery cell
subassembly.
Fig. 18 is a view similar to Fig. 17 but taken from the
opposite side of the battery pack) approximately on line
18-18 of Fig. 16.
Fig. 19 is a cut away view similar to Fig. 18 of the
0 stick pack battery pack of Fig. 3. It indicates the cell
connection arrangement for a pack of two or more cells.
7
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Description of the Preferred Embodiment
The invention is embodied in the battery pack and
charger combination 10 shown partially in Fig. 7 which in-
cludes the charger and battery pack assemblies 12 and 14
shown in Figs. 1 and 2 respectively. Second and third
embodiments (16,18) of battery pack are shown in Figs.
3 and 13 respectively. The receptacle 20 of charger
assembly 12 is designed to receive several different
configurations of battery pack, including a range of power
sizes in each of those configurations. The terminal block 22
shown in Fig. 14 may be used, with minor internal variations,
in all battery packs.
The charger assembly 12 is of a non-isolated type,
preferably capacitive. Its principal components include a
printed circuit board 26, enclosed in a housing split at
approximately the level of the printed circuit board into
upper and lower housing portions 28 and 30 respectively. The
charger assembly 12 may be used in a horizontal position as
shown in the drawings or in a variety of other positions)
including for example mounted with the base or lower housing
against a vertical surface. For convenience, however, in
discussion it will be assumed that the charger is on a
horizontal surface as shown so that terms such as upper and
lower, top and bottom, may be understandably applied.
25 Similar terms will be used for the battery pack assemblies,
as if they were in position for charging, received into the
receptacle 20 of the charger assembly 12.
Looking now at the charger assembly 12 in some detail
and referring to Figs. 1 and 4 through 7 - a principal
30 feature of the upper housing portion 28 is the battery pack
receiving receptacle 20, which extends deeply into the
charger assembly from a battery pack supporting platform
32 which substantially surrounds it. The upper and primary
chamber 34 of the receptacle is of generally oval cross-
section (as seen best in Fig. 4). Its upright side walls
36 terminate in a generally horizontal floor 38. A pair of
vertically extending battery pack locating ribs 40 extend
8
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1 from the floor to about two thirds the height of the side
walls 36 and help to define a terminal end portion 41 of
the receptacle 20. The floor 38 opens downwards into a
secondary chamber 42, the generally rectangular form of which
is seen best in Fig. 4. Its generally upright side walls
44 descend to a generally horizontal floor 46.
A terminal assembly pedestal 50 dominates the secondary
chamber 42 and extends upwards from the floor 46 some-
what into the primary chamber 34~ Its generally rectangular
shape in plan and its asymmetrical disposition in the lower
chamber 42 are also best seen in Fig. 4. The space of the
lower chamber 42 remaining between the pedestal 50 and the
side walls 44 of the chamber is moat-like in form and at
its widest point 52 the floor 46 meets the side wall 44
at a generously radiused corner 54 (Fig. 7). The top wall 56
of the pedestal is penetrated by three apertures, symmetri-
trically placed, and including a longer, central, insulator
aperture 58, flanked by terminal apertures 60 and 62 (see
Fig. 6). Descending partway within the pedestal 50 from its
top wall 56 are a pair of shielding walls 64, which also
define the lateral sides of the insulator aperture 58. At
its lower end, each wall 64 is recessed or rebated outwards
to define a pair of shield extending lips 66.
Internal features of the housing upper portion 28,
best seen in Fig. 7, include a vertically descending,
generally conical, tapered pin 68 extending downwards from
the secondary chamber floor 46 below the moat space 52.
A retaining or stop leg 70 alongside the pin 68 descends
only about half the length of the pin.
A pair of optic light poles or lenses 72, 73 extend
downwards alongside the receptacle 20 and each is suspended
from sloping wall portion 74 of the upper housing 28 by a
"snap-latch" retaining arrangement 76. Their lens like ends
78, 7g are approximately flush with the surface of the
sloping wall 74. (Figs. 4 and 7)
The printed circuit board 26 carries much of the
electrical circuitry of the charger system and external
9
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1 power is brought to it through the power cord 80. However,
only components concerned with the present invention will
be discussed. The board itself 82 is supported in the
housing lower portion 30 by support surfaces such as ledges
or seats 84 shown in Fig. 7. On initial assembly into the
housing lower portion, the board is free to float or be
adjusted in a horizontal plane relative to the housing.
In assembly, a locating hole 86 in the board 82 registers
with and is penetrated by the tapered pin 68 of the housing
upper portion 28. This feature of the assembly will be
discussed in more detail below.
A charger terminal assembly 88 carried by the board 82
extends upwards into the center of the terminal pedestal 50.
(See Fig. 6). It includes a pair of leaf-like terminal
blades 90 each associated with a spring terminal support
92 and both cantilevered from the board 82 and biased to-
ward each other into the center disconnected position
shown in Fig. 6. Bias is augmented by "helper" leaf springs
93~ Towards their upper or outer ends the spring terminal
supports 92 bear a series of cam lobes 94 spaced so that when
the supports g2 meet the cam lobes g4 interleave on the
common center line of terminal block 22 (especially insulat-
ing member 166) and charger terminal assembly 88, as shown in
Fig. 6. The upper ends 96 of the supports g2 are shaped so
as to define an upwardly opening curved V or cam entry g8.
Operative contact between the leaf-like terminals 90 and
their supports 92 is only at a fulcrum 100 raised on the face
of the support 92. The supports 92 are recessed above this
point to provide clearance for the somewhat hook-like upper
ends 102 of the terminals 90. Symmetrically straddling the
terminal assembly 88 is a pair of deflector ramps 104,
each having an upper tip 106 adjacent and somewhat below
the upper ends 102 of the terminals g0 and a lower portion
108, extending outwards in assembly) close to the level of
the floor 46 of the secondary chamber 42 of the receptacle.
Adjacent one of the terminals 90, an upright recess
110 in the terminal assembly 88 supports a thermistor clip
112, so that it stands erect approximately parallel to the
~0
1340~6~
1 terminal g0, as seen best in Figs. 7 and 15. An upper
contact portion 114 of the thermistor clip 112 is approxi-
mately horizontally opposite the upper hook-like contact
portion 102 of the terminal. Closely below the contact
portion 114 of the thermistor clip) a resilient cradle 116
supports a thermistor 118. The board 82 also carries a pair
of light emitting diodes 120, 121 (121 not shown) disposed
on the upper side of the board so that in assembly they re-
gister with the lower ends of the optic posts 72, 73. Diode
120 is green, 121 is red.
Turning now to exemplary battery packs for uae with the
charger assembly 12 just described - clearly they must
be compatible both structurally and electrically with the
charger assembly 12, but details of the electrical circuitry
of the packs and the electrical characteristics of the
battery cells need not be discussed in any detail here. In
the battery pack embodiments disclosed, all battery cells are
cylindrical in form and may be, for example, nickel cadmium
cells of the sub C or 4/5ths sub C size.
The three embodiments disclosed (Figs. 2, 3 and 13)
represent two basic configurations of battery pack - the
so-called "standard" and "stick" packs.
In the "standard" battery pack 14 of Figs. 2 and also 8,
g, 10 and 16-18, the cells 124 are contained in a relatively
thin walled housing 126, preferably of a suitable substan-
tially rigid plastic material. The shape of the housing is
determined primarily by the arrange-ment of the cells, but
other functions such as support of the pack in the charger
assembly 12 and providing stability and support for the cells
inside the housing as well as esthetics may influence the
shape. The cell arrangement in the standard pack is
characterized in having a pair of upright side-by-side cells
124a in the lower or nose portion of the pack) with the base
128 of terminal block 22 below them, and additional cells
124b stacked transversely in pairs above them. Only the
eight cell size of standard pack is shown here. Advantages
of this cell arrangement configuration are compactness and
its suitability for a range of battery pack sizes, (say from
11
i34o~~z
1 four cells to 20 cells) and facilitating the manufacture of
an electrically connected sub assembly of cells in
preparation for its insertion into the pack housing
126. (This cell subassembly is discussed in more detail be-
low). A particular form of the "standard" pack (not shown in
the drawings) may include only the two lower upright cells
124a.
In the typical "standard" battery pack, such as the
eight cell size shown here, the housing 126 has three main
sections. The lower or nose portion 130~is of connected
double cylindrical form in cross section (see Figs 9 and 10),
conforming quite closely to the "envelope" of the two lower
cells 124a. This portion may carry a raised external latch
or pawl 131 for retaining the pack in the receptacle of a
power tool or appliance. A middle portion 132~of the housing
126 is somewhat wider, in part to begin the accommodation of
the transverse cells 124b and also to provide a horizontal
ledge 134, which contributes to the support of the pack in
the charger assembly. A further enlarged upper portion 136
of the housing accommodates the bulk of the transverse cells
124b. An offcenter opening 138 in the housing base 140 is
protected by a downwardly extending shroud 142 consisting of
a straight wall 144 on three of its sides and a thickened
lobe 146 on the fourth. The presence of this lobe 146
reinforces the housing at this potentially vulnerable point;
may accommodate a fastener for "locking" the housing if it is
made in two halves, split on a vertical plane (such as that
indicated at 148 in Figs. 8 and 9); and its radiused corner
150 may assist in guiding the battery pack into final seating
in the receptacle 20 of the charger assembly 12.
The terminal block assembly 22 consists of a plastic
base or frame 128, into which are molded (best seen in
Figs. 6, 7 and 14) metal terminals 154, 156, the terminal
pins of which 158, 160 extend downwards but remain within the
shroud 142. Each terminal 154, 156 includes a connecting tab
162, 164 respectively, for making the electrical connection
with the respective lower cells 124a. The terminal block
assembly 22 and the cells 124 of the pack thus form a sub-
12
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1 assembly (to be described in more detail below) when
electrically connected for insertion as a unit into the
housing 126 of the standard battery pack 14. Integral with
the terminal block base or frame 128 is an insulating wall
166, extending downwards and centrally placed between the
terminal pins 158, 160. The height of this wall 166 exceeds
the length of the terminal pins. Its width substantially
fills the transverse width of the shrouded terminal block
opening 138, so that the terminal pins 158, 160 are
effectively screened, one from the other. Extending upwards
from the terminal block base 128 are a pair of V-guides 168
which help to locate the lower cells 124a relative to the
terminal block 22. The offset location of the terminal
block 22 results in the guides 168 being almost in line with
the terminal pin 158.
The "stick pack" configuration of battery pack (Figs.
3, 11 and 13) is advantageous for packs of a smaller total
number of cells and for tool environments) for example, where
the simple elongated cylindrical form of Fig. 3 is desirable;
or where the more compact but essentially flat form of Fig.
13 is appropriate. Pack size of two to four cells is the
most useful range for the stick pack.
In the "stick" battery pack 16 of Fig. 3 the housing 170
is of modified circular cross section as best seen in Fig.
11, and accommodates three cells, 124c arranged end to end.
This pack preferably uses a terminal block assembly 22a
outwardly the same as the standard pack terminal assembly,
and shielded in a similar way with a shroud 172. This is
identical with the shroud 142 of the standard pack except
that the thickened lobe portion 146 is absent) so that a wall
144' of uniform thickness extends on all four sides. As seen
best in Fig. 11 the modification of the cylindrical form of
the housing 170 consists of extending it to coincide with the
outer face 174, of the shroud 172 and completing the form
with tangential surfaces 176.
In the Z-shaped stick pack 18 of Fig. 13, the three
cells 124c lie with their longitudinal axes in a common
plane. The lower portion 180 of the housing ~1~82' is identical
13
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1 with that of the straight stick pack of Fig. 3, including the
disposition of the terminal block assembly 22a) with respect
to the immediately adjacent lower of the cells 124c, and the
shroud 184.
Figs. 12a through 12e show a sampling of the "key
lockout" system used to standardize the shrouded terminal
arrangement of the battery packs according to number of
cells, whether in standard or stick pack configuration - so
as to avoid mismatch between battery pack and tool. The
determining feature is a ridge or land 188, 189, 190, 191,
192 extending vertically in a predetermined location on the
outside of the shroud walls 144, 144'~ Figures 12a-c
show) respectively, the disposition of lands 188, 189 190 for
standard packs of two, three and eight cell sizes. Figures
12d and a show respectively the disposition of lands 191 and
192 for the two and three cell stick pack.
Details of a standard pack battery cell subassembly 210,
for an eight cell pack of cells 124 are seen best in Figs.
16-18. This assembly begins with a preliminary subassembly
2p 212 consisting of the two battery pack nose portion cells
124a, the terminal block 22 and connecting straps 214, 216.
The cells 124 (124a, 124b) are preferably nickel-cadmium
cells of conventional construction having a central positive
electrode 218, a cylindrical casing 220 and a negative
z5 electrode 222 at the opposite end. Each cell 124 in the
subassembly 210 is fitted with an insulating cap 224, as
protection from inadvertent short circuiting between
the positive electrode 218 and an edge of the casing 220.
The caps 224 of neighboring cells also act as insulating
3p spacers to keep cells parallel and maintain separation
between cell casings 220 as may be seen in Figs. 16-18.
In the subassembly 212 of the nose cells 124a,
the terminal block base member 128 abuts the ends of the
cells (see Fig. 17 for example) and the terminal tabs
35 162, 164 are connected directly to the cell electrodes
218, 222 by a suitable method such as electrical re-
sistance welding. This virtual integration of the
p
1~
13~O~i~2
1 terminal block 22 with the cell subassembly has structural
advantages and eliminates the need for wiring and simpli-
fies assembly. The stick pack configuration of battery
pack (Figs. 3 and 13) benefits from a similar close juxta-
position of terminal block (22a) and cell end. Preparatory to
making up the complete subassembly 210 the ends of connecting
straps 214, 216 are bent up at right angles to form connect-
ing tabs 226) 228 for connecting with the two lower cells
124a. The remaining four upper cells 124b are "stacked"
above these so that the juxtaposed cell ends of opposite
polarity are coplanar, as seen best in Fig. 16. An
insulating board 229 separates the casings 220 of the upper
cells 124b from the ends of the lower cells 124a. Series
connection of the cells is made by connecting straps 230)
seen best in Figs. 17 and 18. Permanent connection of
connecting straps 230 and tabs 226, 228 to the cell
electrodes is made by some suitable process such as electric
resistance welding. As seen in the figures, all electrical
connections of upper cells 124b of the standard pack
configuration are made in a pair of spaced apart parallel
planes. Such "uniformity" simplifies such operations as
setting the connecting straps 230 in position and connecting
them (as by resistance welding), and facilitates automation
of the assembly of cell subassembly 210.
z5 Before being encased in the battery pack housing 126,
the cell subassembly 210 is enshrouded in a tight fitting
"boot" 232. Preferably the boot 232 is of natural rubber,
or as an alternative, a flexible plastic applied by a heat-
shrink process may be used. In both cases the boot must
be tight enough and tough enough to assist materially
in maintaining the structural integrity of the cell sub-
assembly 210, and in supplementing the insulation of the
cells afforded by the housing 126. With the boot 232 in
place, inadvertent puncturing or rupturing of the housing
126 would not expose "live" portions of the cell sub-
assembly to outside contact. As indicated in Figs. 16 to
18) the mouth 234 of boot 232 should reach preferably
at least halfway down the lower cells 124a. The cells
of the battery pack are at high voltage only when the
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1 battery pack is inserted in the charger and charging and
in that condition substantially the entire nose portion
130 of the battery pack housing 126 is shielded by the
walls of the charger receptacle 20.
The cell subassembly 210 is stabilized within the
battery pack housing 126 by its relatively snug fit in the
nose portion 130 and, in the upper housing portion 136, by
its engagement with bosses 236 and spacer element 238, in-
tegral with the housing portion 136.
An eight cell battery pack has been used as an example
of the "standard pack" configuration but the design is
suitable for a wide range of sizes, twenty cells being an
example of a larger size. In this) the "upper" portion
would include 18 cells 124b. The range of sizes may also
include an odd number of cells such as eleven. In the
odd sizes, a centrally placed single cell occupies the
uppermost layer of the stack of cells 124b (not shown in
the drawings).
A stick pack battery pack 16 is shown in more detail in
Fig. 1g. The drawing shows the arrangement for a pack of
two or more cells. The lower or nose portion"242 of the
housing 170, including the terminal shroud 172, includes an
internal shoulder 244 for positioning and retaining the
terminal block assembly 22a in the housing. This portion
of the housing, including the shroud 172 and shoulder 244,
may be referred to generally as the terminal end 246 of the
housing.
The structure of the terminal block assembly 22a is
very similar to that of the standard pack assembly (22)
described above. Positive and negative terminals 248, 250
respectively, are molded into an insulator block or
support member 252. Negative terminal connecting tab 254
connects directly (for example by electrical resistance
welding) with the negative end 222 of the first cell 124c.
Positive terminal connecting tab 256, perpendicular to the
support member 252, extends up alongside the cell casing
220. The insulator wall 166' separating the terminals
248, 250 is integral with the terminal block base 252.
16
~~~oo~~
1 Intermediate series connection of the cells 124c is made
by a folded connector strap 258 rigidly connected to the
cell ends (for example as by resistance welding) with an
insulator p ad 260 ensuring a desired separation between the
ends of neighboring cell casings. Electrical series
connection of the cells is completed by a wire lead assembly
262 connected by a slide-on connector 264 at positive
terminal tab 256 and a permanently wired connection 266 at
the positive electrode 218 of the top end cell of the pack.
This connection is also protected by an insulator p ad 260
and the complete subassembly 267 of connected cells with
terminal block assembly 22a is enshrouded in a boot 268
extending from its closed end 270 at the top of the pack to
an open mouth 272 encircling the bottom cell 124c, close to
its end 222. As seen in Fig. 11 the cross section of housing
170 is not completely round. This departure from a purely
cylindrical form in part provides space for a pair of upright
spaced apart guide members 274 which help to determine and
maintain the rotational position of the cell and terminal
block subassembly 267 within the housing 170.
Comparison of Figs. 7 or 18 and 19 shows the essential
similarity between battery packs of the standard and stick
type with regard to the juxtaposition of terminal block
assemblies and a first cell of the battery pack, and also
of the direct connection of the negative terminal - a compact
and efficient design with the potential for savings in
manufacturing cost and good reliability in service.
In the assembly of the charger 12, precise alignment or
register between the terminal apertures 60) 62 and the in-
sulator wall aperture 58 of the pedestal 50 with terminal
assembly 88 is obtained through the interaction of the
tapered pin 68 of the housing upper portion 28 and the
dowel or locating hole 86 in the printed circuit board 82.
As can be seen in Fig. 7, space 196 is provided at the
supports or seats 84 of the printed circuit board base
82, so that as the assembly of the two halves 28, 30
of the charger housing is made, the housing halves fit
!+0
17
~340b62
1 snugly at joint 198 and the final position of the printed
circuit board base 82 is determined by the progressively
limiting entry of the pin 68 into the hole 86. In the
manufacture of the housing upper portion 28 the horizontal
disposition of the apertures 58, 60, 62 is gauged entirely
with reference to the locating pin 68. In the sub assembly
of the printed circuit board 26, disposition of the charger
terminal assembly 88 is made entirely with reference to the
gauge or locating hole 86, thus ensuring the desired
precision of register or alignment of aperture with terminal.
A battery pack and charger assembly system according
to the invention is particularly useful when the charger
is of a non-isolated type such as capacitive. In such a
system the cells and the battery and charger terminals are at
a high voltage during charging so that in operating the
system there is the potential for electric shock, as well as
shorting of the terminals of either battery pack or charger
assembly when they are potentially exposed before or after
connection and charging.
z0 The combination of the battery pack terminal block assembly
(22) 22a) and the shroud (142, 172, 184) with its walls (144,
144') cooperating with the transverse terminal block
insulating wall (166, 160'), so isolates and shields the
respective battery terminal pins (158, 160) in their
5 respective "cells" (202, 204, seen best in Fig. 10), that the
possibility of inadvertent short circuiting contact between
them is almost eliminated. And) as indicated above) the
walls of the battery pack housing 126 and the boot 232 give
the internal cell subassembly 210 two layers of protection.
30 Inadvertent contact with the charger assembly terminals
90 is also very well guarded against. First of all) the
charger terminal assembly 88 is protected by being at the
bottom of the relatively deep receptacle 20. There, in the
secondary chamber 42 of the receptacle, the terminal assembly
35 88 is recessed within its protective housing pedestal 50.
To enhance this protection, the apertures 58) 60 ,62 in the
pedestal top 56 are kept small. Hence the importance of the
18
13~o~s2
1 precise alignment between these apertures and the terminal
assembly 88 referred to above.
In the "open" condition of the charger and particularly
the charger terminal assembly 88 as shown in Fig. 6, the
terminals g0 are retracted away from the vertical line of
the terminal apertures 60, 62 under the resilient action of
the terminals 90 (helped by leaf springs 93) and their
supports g2. The combination of this retracted position of
the terminal g0 and the limited access provided by the small
apertures 60, 62 severely limits the possibility of contact
with a terminal 90, in case of inadvertent entry of a
metallic object or probe through one of the apertures. In
case of entry of a metallic "probe" of sufficient length and
small cross section through one of the apertures 60, 62, the
shielding walls 64 would initially divert the probe from the
terminals 90 and on further entry the probe would encounter
one of the ramps 104 and tend to be diverted away from the
terminal 90. Only a small window 206 is left between the
lips 66 of wall 64 and the tip 106 of the ramp 104, and
z0 terminal contact portion 102 is well shielded within.
In preparation for charging operation the terminals 90
must be erected into the near vertical operating position
shown in Fig. 7. This is accomplished by the advance entry
of the insulating wall 166 in its second role as a terminal
assembly actuator through the aperture 58, to encounter the
cam entry 98, and progressively separate the cantilevered
spring terminal supports g2 in a circumferential direction,
so that the terminals g0 are moved into operating position,
in readiness for electrical contact with the battery pack
terminal pins 158, 160. The contact pressure of each contact
portion 102 is augmented by the "leverage" of its fulcrum
100.
Operation of the battery charging circuit in charger 12
is controlled in part by the thermistor 118. The control
variable is battery temperature. Mounted on its clip 112,
the thermistor 118 is in a good thermally conductive relation-
ship with the battery cells 124 of the battery pack. The
chain of this conductivity is from the thermistor through its
clip 112, and particularly the contact or terminal portion
19
134066
114 of the clip, to the battery pack terminal 160 and through
to the battery cells 124 of the battery pack. The thermistor
clip 112 is held in its retaining recess 110, in such a way
that it is biased for good contact against the pin 160. (See
Figs. 7 and 15.) The heat insulating effect of the deep
receptacle 20 helps in heat transfer from battery to thermis-
tor. Advantages of this simple low cost thermistor mounting
include ease of assembly and isolation of the thermistor
from the charger terminals when no battery pack is present.
The use and function of thermistors in battery charger
circuits is well known although, conventionally) the
thermistor is mounted in the battery pack in close
association with one or more of the battery cells. Although
in an unconventional location the thermistor here functions
in a similar way. Electrical resistance of the thermistor
varies with its temperature. The system is designed so that
when, for example, the thermistor senses a temperature
corresponding to a fully charged condition of the batteries,
it signals a control circuit to interrupt charging. In the
2~ present invention, the condition of the charging system is
visually indicated through the medium of the light emitting
diodes (ZED) 120, 121 (121 not shown) carried by the printed
circuit board base 82. Emission of red light (ZED 121, not
shown) indicates that the system is charging and light from
the ZED is transmitted by the optic light pole 73 for an
external visual indication at lens 7g. Similarly, a green
light, at lens 78, from ZED 120, indicates that charging is
complete. (See Figs. 4 and 7)
As has already been indicated, the system of the
present invention comprises a common charger assembly
12, which will accept a variety of battery pack configura-
tions and of sizes or powers within those configurations.
Within the context of a potentially extensive line of
portable power tools or devices, the charger assembly becomes
universal. A basis of this universality is the innovative
design of the receptacle 20. It is based on a unit of two
battery cells erect and side by side. The asymmetrical
~0 20
l~~oss~
1 disposition of the terminal assembly towards one end of the
receptacle floor defines one end of the receptacle as the
terminal end (41) and hence, in the battery pack a
corresponding terminal-adjacent cell. This relationship is
maintained in all battery pack configurations and sizes
acceptable to the charger.
The contribution of the depth of the receptacle 20
to electrical safety has been referred to above. The depth
and shape of the receptacle also keeps each battery pack
securely erect when installed in the charger assembly. This
stability is enhanced by the engagement of the ledge 134 in
the housing 126 of the standard pack configuration of battery
packs with the charger housing platform 32 surrounding the
top of the receptacle 20. Dimensions are such that this
engagement limits the entry of the battery pack into the
receptacle so that it does not bottom out and so that its
weight is supported by the substantial platform 32 and
the ledge 134 rather than elements at the bottom of the
receptacle.
The stick pack configurations of Figs. 3 and 13 are
limited in size as described above and hence are lighter
and no special provision is made for vertical supportof their
weight. However, they are guided into and held erect in the
charger receptacle terminal end 41 by the internal vertical
z5 ribs 40 of the receptacle. (Juxtaposition shown in phantom
outline in Fig. 11).
In this disclosure of the invention only one charger
embodiment and a limited number of battery pack embodiments
have been included, but clearly the invention has wider
application, both in terms of variations within the spirit
of the invention and also in terms of the large number of
tools and other devices represented in the field of the
invention. These tools may include for example, electric
drills) screwdrivers, circular saws, jigsaws, flashlights,
string trimmers and many others from the general power tool
as well as the lawn and garden tool fields and the field of
small domestic appliances.
21
L340~b2
1 An important aspect of the invention, the cost effective
and convenient universality of the charger assembly, derives
in part from "keying" the connection of the charger and
battery pack to the unit of a single cylindrical cell, on end
in the charger receptacle and with a terminal block substan-
tially coaxial with the cell. The charger receptacle is
elongated to accommodate at least one more cell alongside the
first, and is made deep enough to provide at least auxiliary
support for the portion of the battery pack housing contained
in the receptacle. In the charger assembly disclosed, the
receptacle will accommodate battery packs with a maximum of
two side-by-side cells in the charger engaging "nose" of the
pack. Clearly) in keeping with the invention, a receptacle
may be extended to accept a battery pack housing three or
more side-by-side cells in its nose. In such an extended
version, the "prime" cell associated with the terminal block
of the battery pack could still be at one end, or alter-
natively, the terminal block could be associated with one of
the intermediate cells. In the latter case upright ribs on
the receptacle walls similar to ribs 40 in Figures 5 and
11 could be provided to offer auxiliary support for the
battery packs needing it) such as the stick pack type
having only one upright cell in the receptacle area. In all
cases, the present charger/battery pack system concept
combines providing substantial support for the battery pack
in the charger (by virtue of the potential engagement of a
portion of the battery pack housing with the walls of the
receptacle and upper support platform, when applicable) with
a minimum limitation on the configuration of the battery pack
outside the receptacle. It will be realized that the concept
of charger receptacle configuration must be compatible with
tool receptacles also, and that it is in association with the
tool that freedom in battery pack configuration design is
especially valuable.
All of these possible embodiments of interfacing
between charger and battery pack according to the in-
vention, would enjoy the related advantages of convenience
economy and safety. Confined to the charger assembly, the
22
...,...~._..~..-...~.~.....~..~ ~....~..~..~..... W«. ~.._.~...M~._.~.~~ ~ ...
..
~~~os6~
1 charging control circuitry is potentially more reliable and
the cost of duplicating it (especially the means for
sensing battery temperature changes)in every battery pack is
avoided. The particular shielding given the terminals of the
charger assembly and the terminals and cells of the battery
pack inherently reduces the risk of electric shock or
inadvertent short circuiting and is effective when charger
and battery pack are connected for charging as well as when
they are separated. The reliability of these safety features
is enhanced by the means provided to achieve accurate
register in assembly between the charger terminals and their
access apertures.
20
z5
35
l+0
z3
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