DC power source unit

• US 6,495,932 B1
• Filed: 01/07/2000
• Issued: 12/17/2002
• Est. Priority Date: 09/26/1997
• Status: Expired due to Term

• Current Assignee: Koki Holdings Co., Ltd.
• Original Assignee: Hitachi KOKI Company Limited (Koki Holdings Co., Ltd.)
• Inventors: Orikasa, Hiroaki, Nakagawa, Atsushi, Nakayama, Eiji, Funabashi, Kazuhiko, Yoshimizu, Chikai, Shinohara, Shigeru, Shimada, Takahiko
• Primary Examiner(s): FLEMING, FRITZ M
• Application Number:
  US09/478,798
• Time in Patent Office: 1,075 Days
• Field of Search: 307/150, 307/154, 307/151, 307/134, 307/116, 307/125, 307/126, 307/130, 307/131, 340/310.08
• US Class Current: 307/150
• CPC Class Codes: G01R 31/3004 Current or voltage test

Abstract

A DC power source unit includes a main unit that generates DC voltage, and an output cable. The output cable is connected, either integrally or detachably, at one end to the output of the main unit and another end to an adapter plug. The adapter plug is electrically connected to an electrically powered tool, such as an electrical drill. An output voltage switching unit switches the level of voltage supplied by the main unit to the electrically powered tool, to a level that matches the rated voltage of the electrically powered tool that corresponds to the fitting portion of the adapter plug.

Claims

1. A DC power source unit for supplying DC voltage to an electrically powered tool, the DC power source unit comprising:

a main unit that has an output and produces DC voltage from the output;

an adapter plug that is electrically coupled to the electrically powered tool in use;

a connector that is electrically connected to the output of said main unit;

an output cable having one end attached to said adapter plug and another end attached to said connector;

output voltage setting means, provided in said adapter plug, for setting a level of voltage to be supplied to the electrically powered tool, the level of voltage set by said output voltage setting means corresponding to a rated voltage of the electrically powered tool;

load current detection means for detecting an instant load current flowing in the electrically powered tool and outputting a detection signal indicative of the load current;

output voltage changeover means for changing over the level of voltage to be supplied to the electrically powered tool in response to the level of voltage set by said output voltage setting means; and

control means for controllably transmitting the level of the voltage set by said output voltage setting means to said output voltage changeover means, based on whether the detection signal output from said load current detection means indicates that the instant load current is equal to or less than a predetermined load current.

2. The DC power source unit as claimed in claim 1, wherein the adapter plug is detachably connected to the one end of the output cable.

3. The DC power source unit as claimed in claim 2, wherein said output voltage setting means comprises a resistor.

4. The DC power source unit as claimed in claim 1, wherein the predetermined load current is zero.

5. The DC power source unit as claimed in claim 1, wherein the predetermined load current is in a range of 2 Amp to 5 Amp.

6. A DC power source unit for supplying DC voltage to a cordless electrically powered tool, the electrically powered tool having a battery insertion port adapted to electrically couple with a fitting portion of a battery pack, the DC power source unit comprising:

a main unit that has an output and that supplies DC voltage from the output;

an adapter plug having a fitting portion adapted for electrically coupling with the battery insertion port of the electrically powered tool, the adapter plug housing therein a voltage setting means for setting a rated voltage of the electrically powered tool;

an output cable having one end attached to said main unit and another end engaged with the adapter plug;

output voltage switching means for switching a level of voltage supplied by the main unit to the electrically powered tool, to a level that matches rated voltage of the electrically powered tool that the fitting portion of the adapter plug is adapted to electrically couple with, the output voltage switching means including a plurality of resistors connected in parallel,

wherein at least one of the plurality of resistors is selected upon connection of the adapter plug to the main unit through the output cable and in response to the voltage setting means, a selected resistor determining the level of voltage supplied by the main unit.

7. A DC power source unit as claimed in claim 6, further comprising:

a plurality of adapter plugs provided in a one-to-one correspondence with a plurality of electrically powered tools, each adapter plug being shaped to enable coupling with a corresponding electrically powered tool that has a corresponding rated voltage, and being shaped to prevent coupling with all non-corresponding electrically powered tools that have a non-corresponding rated voltage; and

a connector for detachably connecting the cable to each adapter plug, the connector being adapted to connect to all adapter plugs regardless of the rated voltage of the corresponding electrically powered tool.