Abstract: A system of cordless power tools includes a cordless power tool adapted to removably receive a rechargeable battery pack. In each embodiment, the battery pack and the power tool have complementary rails and grooves that aid in aligning the positive and negative blade terminals of the battery pack to the positive and negative tool terminals, respectively, of the power tool. In one embodiment, a keying feature cooperates with a mating keying feature to further align the terminals of the battery pack to the terminals of the power tool. In a second embodiment, the battery pack includes two sets of blade terminals, with each set including a positive blade terminal and a negative blade terminal.

Abstract: A system of cordless power tools includes a cordless power tool adapted to removably receive a rechargeable battery pack. In each embodiment, the battery pack and the power tool have complementary rails and grooves that aid in aligning the positive and negative blade terminals of the battery pack to the positive and negative tool terminals, respectively, of the power tool. In one embodiment, a keying feature cooperates with a mating keying feature to further align the terminals of the battery pack to the terminals of the power tool. In a second embodiment, the battery pack includes two sets of blade terminals, with each set including a positive blade terminal and a negative blade terminal.

Abstract: A system of cordless power tools includes a cordless power tool adapted to removably receive a rechargeable battery pack. The system further includes a battery pack charger and a converter for converting AC electricity to DC electricity. A battery pack interface block is captured between clam shell halves of a battery pack housing and includes a plurality of male blade terminals. The male blade terminals are received within recessed female terminals of a tool terminal block and similarly received by recessed female terminals of the charger. The tool terminal block further includes a pair of male terminals which engage recessed female terminals of the converter.

Abstract: A system of cordless power tools includes a cordless power tool adapted to removably receive a rechargeable battery pack. The system further includes a battery pack charger and a converter for converting AC electricity to DC electricity. A battery pack interface block is captured between clam shell halves of a battery pack housing and includes a plurality of male blade terminals. The male blade terminals are received within recessed female terminals of a tool terminal block and similarly received by recessed female terminals of the charger. The tool terminal block further includes a pair of male terminals which engage recessed female terminals of the converter.

Abstract: A system of cordless power tools includes a cordless power tool adapted to removably receive a rechargeable battery pack. The system further includes a battery pack charger and a converter for converting AC electricity to DC electricity. A battery pack interface block is captured between clam shell halves of a battery pack housing and includes a plurality of male blade terminals. The male blade terminals are received within recessed female terminals of a tool terminal block and similarly received by recessed female terminals of the charger. The tool terminal block further includes a pair of male terminals which engage recessed female terminals of the converter.

Abstract: A system of cordless power tools includes a cordless power tool adapted to removably receive a rechargeable battery pack. The system further includes a battery pack charger and a converter for converting AC electricity to DC electricity. A battery pack interface block is captured between clam shell halves of a battery pack housing and includes a plurality of male blade terminals. The male blade terminals are received within recessed female terminals of a tool terminal block and similarly received by recessed female terminals of the charger. The tool terminal block further includes a pair of male terminals which engage recessed female terminals of the converter.

Abstract: A system of cordless power tools includes a cordless power tool adapted to removably receive a rechargeable battery pack. The system further includes a battery pack charger and a converter for converting AC electricity to DC electricity. A battery pack interface block is captured between clam shell halves of a battery pack housing and includes a plurality of male blade terminals. The male blade terminals are received within recessed female terminals of a tool terminal block and similarly received by recessed female terminals of the charger. The tool terminal block further includes a pair of male terminals which engage recessed female terminals of the converter.

Abstract: A dual-mode system for inexpensively operating electrically powered double-insulated devices (12), such as hand-held power tools and appliances. The system includes a cordless battery power module (14) that supplies the power and current demands of the device (12) in a cordless mode or a chopper module (21) that supplies the necessary power and current demands in a physical envelope commensurate in size and interchangeable with that of the battery power module (14). The chopper module (21) is provided with a non-filtered high efficiency converter circuit that allows the chopper module (21) to generate the power and current required by the driven device (12). The inductance of the motor (11) for the driven device (12) is used to filter the output of the chopper module (21). Eliminating the output filter from the chopper module (16) significantly reduces the cost and size of the module (16).

Abstract: A thermal control circuit (49) for inexpensively protecting the power interface of cordless and dual-mode powered devices (12), such as hand-held power tools and appliances. The powered device includes a motor (11) that is operable in a preselected voltage range. A switch assembly (110) controls the flow of electrical energy to the motor (11). A power module (14, 16) is configured to supply electric power and to mate with the low-voltage DC power tool (12). The power module (14, 16) is adapted to provide a DC voltage in the preselected voltage range suitable for powering the low-voltage DC power tool (12). A case (91) for the power tool (12) has a pre-defined envelope for electrically and mechanically mating with the power module (14, 16). A power interface that includes at least two terminals, electrically couples the power module (14, 16) to the motor (11). The thermal control circuit (49) protects the power interface from damage caused by an overtemperature level.

Abstract: A system of cordless power tools includes a cordless power tool adapted to removably receive a rechargeable battery pack. The system further includes a battery pack charger and a converter for converting AC electricity to DC electricity. A battery pack interface block is captured between clam shell halves of a battery pack housing and includes a plurality of male blade terminals. The male blade terminals are received within recessed female terminals of a tool terminal block and similarly received by recessed female terminals of the charger. The tool terminal block further includes a pair of male terminals which engage recessed female terminals of the converter.

Abstract: A braking circuit for braking an electric motor having an armature and run and brake windings, which includes a switching circuit disposed between a source of electrical power and the run winding, this circuit being operable to disconnect the run winding from the source of electrical power. The braking circuit further includes a switching mechanism operable to connect the brake winding in order to brake the electric motor. The switching mechanism preferably connects the brake winding after a predetermined period of time has elapsed from the disconnection of the run winding. This braking circuit can be used in a saw for braking the saw's blade.

Abstract: A cordless electric mower having an energy management system that allows a user to operate the cutting blade motor of the mower at a wide range of user selected speeds. The mower is provided with a user adjustable throttle control which, when in the wide-open position allows the cutting blade motor to be rotated at a maximum, predetermined speed. When the throttle is set to some lesser speed, the system automatically implements a speed foldback routine whenever the mower encounters heavy loading which would result in an undesirably high current draw on the battery. When the speed foldback routine is implemented, the system limits the maximum amount of current that can be drawn by the motor until the excessive loading condition has been removed. Once the excessive loading condition has been removed, the speed foldback routine automatically increases the speed of the blade motor back up to almost the originally selected speed.

Abstract: A battery charger 10 includes a capacitor 20 which establishes a level of current sufficient to fast charge in one-hour a battery 18 having from one to twenty cells. An SCR 16 is controlled by a timer 42 to initially delay the supply of current while determining whether the battery 18 is hot or cool. If battery 18 is cool, charger 10 proceeds to fast charge the battery. After battery 18 is fully charged, the battery heats to a temperature where a NTC thermistor 58 responds to trigger a second timer 52 which controls SCR 16 to stop the fast charging operation. Charger 10 is then controlled to prevent the charger from thereafter re-entering a fast charge mode.If battery 18 is initially hot, charger 10 is controlled to further delay the initiation of a fast charge operation until the battery cools to or below the charge-start temperature.

Abstract: The motor speed control circuit senses average back EMF as a measure of motor speed. The back EMF charges a capacitor circuit which accumulates charge and develops a voltage indicative of the motor speed. A sample and hold circuit may be used to sample the back EMF when the motor is switched off during each cycle. This voltage is compared with a reference voltage indicative of the desired motor speed. An error signal is generated by comparing the desired speed with the actual speed and this error signal is used to generate a variable duty cycle pulse train which gates the power controlling transistor on and off to control motor speed. A logic gated or SCR gated voltage boosting circuit operates in synchronism with the gating pulse train to drive the power transistor hard into saturation. This lowers the resistance of the power transistor, causing less energy dissipation as waste heat.