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Automatic Screwdriver With Dual Torque Capability

IP.com Disclosure Number: IPCOM000039707D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Atkins, AW: AUTHOR [+2]

Abstract

An electric screwdriver with a variable mechanical clutch limiting the maximum torque available can also provide a lower, variable torque, controlled electrically, for applying an initial pre-torque to a screw. A commercially available electric screwdriver (1) has a mechanical clutch which limits the maximum torque available at the screwdriver tip. This torque limit may be adjusted mechanically as required. The clutch has a sensor attached which signals when it has "tripped", i.e., when maximum torque has been reached. Additionally, the motor has the ability to produce a lower maximum torque controlled electrically. This lower torque is used as a pre- torque on a number of screws prior to each receiving the maximum (clutch-controlled) torque.

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Automatic Screwdriver With Dual Torque Capability

An electric screwdriver with a variable mechanical clutch limiting the maximum torque available can also provide a lower, variable torque, controlled electrically, for applying an initial pre-torque to a screw. A commercially available electric screwdriver (1) has a mechanical clutch which limits the maximum torque available at the screwdriver tip. This torque limit may be adjusted mechanically as required. The clutch has a sensor attached which signals when it has "tripped", i.e., when maximum torque has been reached. Additionally, the motor has the ability to produce a lower maximum torque controlled electrically. This lower torque is used as a pre- torque on a number of screws prior to each receiving the maximum (clutch-controlled) torque. This can be advantageous when the action of applying full torque to a first screw to hold two components together prior to the insertion and pre-torque of additional screws can result in unacceptable relative movement between the two components. In operation, the "low torque" input (2) is activated in order to set the flip-flop (3); this closes a switch (4) which permits the screwdriver motor to draw a current up to the preset current limit. This current limit (5) consists of a set of selectable series resistors. The screw is rotated by the motor until the torque required to advance it further is greater than that available when it stalls. This is detected by the motor stop d...