Power tool having early braking functionality

Abstract

A power tool including a motor; a fastener gripping portion operatively coupled to the motor for causing movement of the fastener gripping portion between a home position and a retracted position to set a fastener; and a controller for controlling the motor wherein during a reset stage of operation, in which the fastener gripping portion is moved towards the home position, the controller is configured to decelerate the motor before the fastener gripping portion reaches the home position.

What is claimed is: 
     
         1 . A power tool comprising:
 a motor;   a fastener gripping portion operatively coupled to the motor for causing movement of the fastener gripping portion between a home position and a retracted position to set a fastener; and   a controller for controlling the motor wherein during a reset stage of operation, in which the fastener gripping portion is moved towards the home position, the controller is configured to decelerate the motor before the fastener gripping portion reaches the home position.   
     
     
         2 . The power tool of  claim 1 , wherein during the reset stage of operation the controller is configured to drive the motor at a first target speed during a first portion of the reset stage of operation and to decelerate the motor upon determination by the controller that the fastener gripping portion is within a threshold distance from the home position. 
     
     
         3 . The power tool of  claim 2 , wherein the magnitude of the threshold distance is at least 75% of the total distance travelled by the fastener gripping portion between the home position and the retracted position. 
     
     
         4 . The power tool of  claim 2 , wherein the first target speed is the maximum driving speed of the motor. 
     
     
         5 . The power tool of  claim 2 , wherein the motor is decelerated to a second predetermined speed which is maintained until the controller subsequently determines that the fastener gripping portion is at the home position wherein in response the controller decelerates the motor to a stop. 
     
     
         6 . The power tool of  claim 5 , wherein the second predetermined speed ranges between 50% to 80% of the first target speed. 
     
     
         7 . The power tool of  claim 2 , wherein the controller is configured to determine the number of motor turns during movement of the fastener gripping portion from the home position to the retracted position and the number of motor turns during the reset stage of operation whereby the controller can determine when the fastener gripping portion is within the threshold distance from the home position when the number of motor turns determined during the reset stage of operation is within a threshold number of the number of motor turns determined during movement of the fastener gripping portion to the retracted position. 
     
     
         8 . The power tool of  claim 7 , wherein the controller determines the fastener gripping portion is at the threshold distance from the home position when the number of motor turns determined to have occurred during the reset stage of operation is at least 75% of the number of motor turns determined to have occurred during movement of the fastener gripping portion to the retracted position. 
     
     
         9 . The power tool of  claim 1 , further comprising a sensor which generates an output indicative that the fastener gripping portion has reached the home position during the reset stage of operation. 
     
     
         10 . The power tool of  claim 9 , wherein the controller is configured to stop reverse movement of the motor based on the signal received from the sensor. 
     
     
         11 . The power tool of  claim 9 , wherein the sensor is a Hall sensor mounted in a fixed position within the tool which is configured to detect a magnet which is axially fixed relative to the fastener gripping portion. 
     
     
         12 . The power tool of  claim 11 , wherein the magnet is mounted on an axially moveable feature of a mechanism which causes axial movement of the fastener gripping portion during driving of the motor in use. 
     
     
         13 . The power tool of  claim 1 , wherein the controller is configured to control the motor to move the fastener gripping portion to the home position if in response to receiving a tool actuation signal the controller determines that the fastener gripping portion is not at the home position. 
     
     
         14 . The power tool of  claim 1 , wherein the fastener gripping portion is a jaw assembly. 
     
     
         15 . The power tool of  claim 1 , wherein the power tool is a blind rivet setting tool.