Electricity: battery or capacitor charging or discharging – Cell or battery charger structure – For handheld device
Reexamination Certificate
1999-07-02
2001-02-20
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Cell or battery charger structure
For handheld device
C320S107000
Reexamination Certificate
active
06191554
ABSTRACT:
This application claims priority on Japanese Patent Application No. 10-187827, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present, invention relates to battery-charging systems for electrical equipment. More particularly, the present invention relates to a battery-charging system that includes an electric power tool operating on rechargeable internal batteries and a battery charger for charging the internal batteries of the electric power tool.
2. Description of the Related Art
One type of conventional rechargeable electric power tool incorporates a detachable battery pack mounted in the lower end of the handle thereof. When the battery pack needs to be recharged, it is detached from the handle of the tool and set on a separate charger. After the charging is completed, the battery pack is mounted back in the handle to resume operation. If an electric power tool operating on a detachable battery pack is used for extended periods of time, for example, on a production or assembly line of an automobile plant, an auxiliary battery pack is set in a charger for recharging. When the pack mounted in the tool is discharged, the operator replaces it with the one that has been recharged by the charger and sets the discharged battery pack on the charger for recharging.
Battery packs used for the above-described purpose are generally designed to maximize their capacity and thus the operating time of the tool per charge. This tends to increase the size and weight of the packs, which in turn places an excessive physical strain on the operator and reduces the operability of the tools and work efficiency. This tendency is particularly pronounced when such large and heavy battery packs are used on assembly lines for an extended period of time; the operability of the tools may be severely affected so as to significantly reduce the productivity of the plant. In addition, loss of time in the process of replacing discharged battery packs has been a significant factor that reduces work efficiency.
Moreover, chargers used for such battery packs continue to supply charging current, even after the battery packs are charged to the full, therefore placing the batteries or cells in the pack under heavy load and reducing the charge efficiency. In addition, this results in a waste of power.
In view of the aforementioned problems, the applicant has proposed a battery-charging system as shown in FIG.
8
. This battery-charging system includes a charger
1
and an electric power tool
2
which has a built-in batteries
6
. According to this system, the batteries
6
can be charged without their removal from the tool
2
. The electric power tool
2
additionally includes a controller
28
which in turn is provided with a central processing unit (CPU), a battery temperature sensor
8
, and a current detector
10
for detecting the amperage of the charging and discharging currents of the batteries
6
, which permit. monitoring of the remaining charge level based on the charging/discharging current. Also provided in the tool
2
are four terminals
13
a
,
14
a
,
15
a
, and
16
a
. The terminals
13
a
and
14
a
are provided for carrying current to charge the batteries
6
, the terminal
15
a
is provided for outputting to the charger
1
data on the temperature of the batteries
6
, and the terminal
16
a
is provided for outputting to the charger
1
the data on the charge/discharge level from the controller
28
. The charger
1
is provided with four corresponding terminals for connection with these terminals
13
a
,
14
a
,
15
a
, and
16
a
so as to control charging operation based on data on battery charge/discharge received from the controller
28
and on the temperature of the batteries, and to indicate the charge/discharge level of the batteries.
Furthermore, the charger
1
includes a charge/discharge circuit
29
, an indicator unit
4
for indicating the charge state and the remaining charge level of the batteries, and a cooling fan
5
. Also included are the aforementioned four terminals that are connected to the terminals
13
a
,
14
a
,
15
a
, and
16
a
of the electric power tool
2
when it is set on the charger
1
. These charger terminals comprise a pair of terminals
13
b
and
14
b
for passing charging current to the electric power tool
2
, a data receive terminal
16
b
for receiving data on the charge/discharge level of the rechargeable batteries
6
, and a temperature terminal
15
b
provided for receiving data on the temperature of the rechargeable batteries
6
.
As described above, since this system permits charging of batteries without their removal, charging operation itself becomes much less troublesome, and the rechargeable batteries can always be charged to the full when the tool is not in use. Therefore, the charge capacity of the batteries can be reduced so as to reduce the weight of the tool itself. According to the system, by monitoring the remaining charge level, the operator can maintain the torque produced by the tool within a preferred range, which makes the system particularly useful when used on assembly or production lines in plants.
The installed controller transmits information on the charge/discharge level and on the battery temperature to the charger, allowing the charger to indicate the charge state of the batteries and to vary the charging current to suit the charge state. This enables efficient use of the batteries and enhances work efficiency.
Rechargeable batteries, such as nickel-cadmium (NiCad) batteries, deteriorate or have the property of decreasing in capacity if left unused for prolong periods of time or subjected to repeated charge and discharge at less than their full capacities. Since rechargeable batteries are consumable articles, their charge capacities gradually decrease over time, even if care is taken. This results in production of insufficient torque by tools, even after a full charge, and/or in discrepancies between the data on the remaining battery level stored in the aforementioned controller and the actual battery level, thus reducing the reliability of the charge level information provided by the system.
SUMMARY OF THE INVENTION
In view of the above-identified problems, an important object of the present invention is to provide a battery-charging system that improves the work efficiency and the operability of the electric power tool included in the system.
Another object of the present invention is to provide a battery-charging system that reconditions or rejuvenates rechargeable batteries and prolongs battery service life.
Still another object of the present invention is to provide a battery-charging system that improves the reliability of the information on the battery charge level provided by the system.
The above objects and other related objects are realized by the invention, which provides a power tool charging system which includes an electric power tool including at least one rechargeable battery on which the electric power tool operates and a charger on which the electric power tool is set for charging the at least one battery, with the charger including a discharge means for forcibly discharging the at least one battery.
According to one aspect of the present invention, the discharge means includes a relay, a resistor, and a battery refreshing switch which are placed in a circuit, with the at least one battery. In this system, the relay is closed by operating the battery refreshing switch so as to forcibly discharge the batteries via the resistor.
According to another aspect of the present invention, the charger further includes a first controller which, when the discharge means is activated, performs at least one cycle of charging the at least one battery to the full and discharging the at least one battery to a predetermined level.
According to still another aspect of the present invention, the first controller performs two cycles of fully charging the at least one battery and discharging the at least one battery to a predetermined level.
According to ye
Horikawa Kazuyoshi
Matsunaga Yutaka
Muramatsu Tomoo
Nakane Shin-ichi
Foley Hoag & Eliot LLP
Luk Lawrence
Makita Corporation
Wong Peter S.
LandOfFree
Power tool charging system having battery reconditioning and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Power tool charging system having battery reconditioning and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power tool charging system having battery reconditioning and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2608705