Abstract: A system for controlling the energy output of a combustion-powered, fastener-driving tool in which a fan is arranged to produce turbulence in a combustion chamber when the fan is driven, in which a direct current motor is arranged to drive the fan when a driving voltage is applied across the motor, and in which a battery provides a battery voltage not less than the driving voltage. A voltage divider includes a settable resistance, either a potentiometer or two parallel, fixed resistances that can be alternatively selected, and is used to provide a setpoint voltage. A comparator, an inverter, and a transistor switch are arranged to sample a voltage proportional to the rotational speed of the fan, to compare the sampled voltage to the setpoint voltage, to apply the driving voltage across the motor if the sampled voltage is less than the setpoint voltage, and to remove the driving voltage from across the motor if the sampled voltage is not less than the setpoint voltage.

Abstract: For a combustion-powered, fastener-driving tool, a combined ignition and fuel system comprises a battery, two normally opened switches connected to the battery, namely a head switch and a trigger switch, a fuel injector including a solenoid and an associated circuit controlling the fuel injector to enable the fuel injector to inject a combustible fuel for a first time interval, a circuit for producing ignition, and a circuit for monitoring the head and trigger switches, for disabling the injector-controlling circuit if the trigger switch is closed while the head switch is opened or if both switches are opened, for enabling the solenoid if the trigger switch is closed while the head switch is closed, for enabling the ignition-producing circuit after a second time interval succeeding the first time interval, and for disabling the ignition-producing circuit when the injector-controlling circuit is disabled as mentioned.

Abstract: For use in a combustion-powered, fastener-driving tool having a combustion chamber, a source of a combustible fuel, and a switch that must be closed to enable the tool, a fuel system comprises a fuel injector, which includes a normally closed, solenoid-energized valve between the fuel source and the combustion chamber, and an electronic circuit responsive to the switch for energizing the solenoid to open the valve when the switch is closed and for deenergizing the solenoid after a time interval. A resistive-capacitive network defining the time interval includes a first resistor, a second resistor arranged to be selectively connected in parallel therewith, a thermistor connected in parallel therewith, and a variable resistor connected to the parallel resistors. Another network effects a time delay between closure of the switch and energization of the solenoid. Optionally, another network varies the time interval in response to ambient pressure.

Abstract: For a combustion-powered tool, an ignition system is powered by a battery and is arranged so that a sudden discharge of a capacitor, as charged via an oscillator, produces a spark at a spark gap of a spark plug, so that the oscillator is enabled if a trigger switch is closed while a head switch is closed, but not if the trigger switch is closed while the head switch is opened, and if a battery voltage, as monitored, is not less than a reference voltage, and so that a silicon-controlled rectifier, which is arranged to produce a sudden discharge of the capacitor, is switched to a conductive state if the capacitor voltage, as monitored, and is not less than a reference voltage. The head and trigger switches, which are photoelectric, are polled intermittently to determine whether they are closed. Predominantly, solid-state components are used.