An electric power tool includes: a brushless motor having a plurality of stator windings and configured to rotate in accordance with voltages applied to the plurality of stator windings, an induced voltage being generated in accordance with a rotation of the brushless motor; a rectifier circuit configured to rectify an AC voltage; a smoothing capacitor configured to smooth the AC voltage rectified by the rectifier circuit to a pulsation voltage having a maximum value larger than the induced voltage and a minimum value smaller than the induced voltage; and an inverter circuit configured to perform switching operations to output the pulsation voltage to the plurality of stator windings by rotation.

Electric power tool

A control module advantageously reduces cost and enhances reliability, design flexibility, ease of assembly, and performance of a flywheel operated hand tool. The control module includes a thin film printed circuit with non-contact speed sensing of a flywheel to more accurately set the target speed and control transfer kinetic energy thereof to a fastener, achieving a desired depth regardless of variations in component performance and battery voltage. The printed circuit also includes long service life thin film switches for responding to trigger and safety inputs. Furthermore, the control module responds to a user speed selection and to preset speed selection ranges to reconfigure the controls as appropriate to constraints of a fastener drive assembly and to user preferences.

Control module for flywheel operated hand tool

There is disclosed a technique for tightening threaded fasteners in which values of offset torque, initial tension rate relative to angle, final tension rate relative to angle and other joint related factors are empirically determined by instrumenting a plurality of fasteners of the type ultimately to be tightened. In one embodiment, torque and angle are monitored during tightening. Calculations are conducted, while tightening, to determine the tension prevailing in the bolt at a particular angle of advance. By using the calculated tension value and the particular angle of advance, an instantaneous position of threading advance on the tension-angle curve of the fastener is established. From this instantaneous position, it is determined how much greater angle of advance or how much torque is required to tighten the fasteners to a final desired tension value. The same technique may also be used merely to monitor tightening which is terminated by a different tightening strategy. A number of quality control procedures are conducted to determine if the fastener and the tightening tool are performing normally. In another embodiment, analog devices are utilized to convert sensed values of torque and the rate of threading advance into parameters which control tool shut off.

Tension control of fasteners

A system and method for compensating for torque overshoot in a rotary power tool wherein the tool is shut off at an adjusted set point value of torque which is below the target value of torque by the amount of torque overshoot. While the tool is operated to perform a fastening job, the relationship between the torque rate in the fastening job to overshoot in the tool is determined, the torque rate in the job is monitored while the tool is setting the job, and the torque set point is adjusted while the tool is setting the job to compensate for the torque overshoot determined from the foregoing relationship. The relationship between torque rate in the fastening job and overshoot in the tool follows the expression Y=K/X where Y is the overshoot, X is the deceleration time required to tighten the fastener and K is a constant determined by using the measured deceleration time and torque overshoot during a previous high torque rate job in the foregoing expression, the deceleration time being measured between the same selected fractional values of the target torque. During a subsequent fastening job, the deceleration time is measured between the same selected fractional values of target torque, the overshoot is calculated from the foregoing mathematical expression using the previous value of K, and the torque set point is adjusted to compensate for the calculated value of overshoot. The foregoing is performed job-to-job developing a running average of the constant K. While the use of torque-time rates is preferred for simplicity and economy, the use of torque-angle rates also is contemplated.

Power tool compensator for torque overshoot

A torque tool and an associated method are provided which apply operator-defined levels of torque to a threaded fastener. In one aspect, a portable, battery powered torque tool controls the motor to slow further advancement of the threaded fastener once the torque that has been applied to the threaded fastener has reached a predefined threshold. In another aspect, a torque tool monitors a measure of torque applied to a threaded fastener more frequently once the torque applied to the threaded fastener has reached a predefined threshold. A method of defining a mathematical relationship between a first measure provided by a torque transducer of torque applied to a threaded fastener and a second measure provided by a torque measurement reference device of torque applied to the threaded fastener is also provided such that the measure of torque provided by the torque transducer can be calibrated.

Tool and associated methods for controllably applying torque to a fastener

There is disclosed an air powered tool for applying torque to threaded fasteners and the like. The tool comprises a motor, a gear reducer and a driver whereby the motor turns at a higher rate than the driver. In order to provide better resolution of angle sensings, an angle sensor is arranged to determine rotation of the motor rather than of the driver. Because the fastener, driver, gear reducer and motor tend to torque up thereby producing an exaggerated reading for the angle of advance of the fastener, means are provided to compensate for the rotation sensing as a function of applied torque.

Angle sensing tool for applying torque

A portable fastening tool of the type incorporating torque and angle sensors is connected to a data processor which analyzes the torque and angle sensings and generates a shut off signal to terminate tightening. The tool is powered and includes a fluid motor typically energized from a remote source of high pressure air. The data processor is energized by either a battery or an AC source. Termination of tool operation is effected by energizing a solenoid in response to a shut off signal generated by the data processor. In a battery operated embodiment, tool operation is initiated by manual depression of an operating lever while tool termination is effected automatically in response to the shut off signal. This mode of operation reduces the number of required batteries, prolongs battery life and reduces the number and size of electrical components in the tool.

Hall George D

Papers

Angle sensing tool for applying torque

Portable fastening tool with manual turn on and automatic shut off

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