Electromagnetic mode change mechanism for power tool

Abstract

A mode change mechanism for a power tool includes an actuator with a permanent magnet. The actuator is moveable between a first position for a first mode of operation, and a second position for a second mode of operation. A first positioning member is adjacent the first position composed of a ferromagnetic material to attract the permanent magnet. A second positioning member is adjacent the second position and composed of a ferromagnetic material to attract the permanent magnet. An electromagnet may be energized to move the actuator between the first position and the second position. When the electromagnet is not energized and the actuator is in the first position. the actuator is retained in the first position. When the electromagnet is not energized and the actuator is in the second position, the actuator is retained in the second position. When the electromagnet is energized, the actuator moves between the first and second positions.

What is claimed is: 
     
         1 . A power tool comprising:
 a housing coupleble to a source of electric power;   a motor disposed in the housing;   an output shaft received at least partially in the housing;   a transmission in the housing and coupled to the motor and the output shaft for transmitting torque from the motor to the output shaft;   a mode change mechanism having an actuator, a positioning member, and an electromagnet, the actuator including a permanent magnet and being moveable between a first position for a first mode of operation of the power tool, and a second position a second, different mode of operation of the power tool, and the positioning member and the electromagnet configured to (i) retain the actuator in the first position when the electromagnet assembly is not energized and the actuator is in the first position, (ii) retain the actuator in the second position when the electromagnet assembly is not energized and the actuator is in the second position, and (iii) move the actuator from one of the first position and the second position to the other of the first position and the second position when the electromagnetic assembly is momentarily energized.   
     
     
         2 . The power tool of  claim 1 , wherein the positioning member comprises a second permanent magnet adjacent to the first position, and stationary relative to the actuator, wherein the actuator permanent magnet and the second permanent magnet are configured to attract when the actuator is in the first position and repel when the actuator is in the second position. 
     
     
         3 . The power tool of  claim 2 , wherein the actuator permanent magnet and the second permanent magnet each include an array of permanent magnets, with a portion of each array arranged to exert an attractive force between actuator permanent magnet and the second permanent magnet, and a remaining portion of each array of the permanent magnets arranged to exert a repulsive force between actuator permanent magnet and the second permanent magnet. 
     
     
         4 . The power tool of  claim 2 , wherein the electromagnet can be momentarily energized by current flowing in a first direction to move the actuator from the first position to the second position, and can be momentarily energized by current flowing in a second opposite direction to move the actuator from the second position to the first position. 
     
     
         5 . The power tool of  claim 1 , wherein the positioning member comprises a first positioning member adjacent the first position and composed of a ferromagnetic material to attract the permanent magnet when the actuator is in the first position, and a second positioning member adjacent the second position and composed of a ferromagnetic material to attract the permanent magnet when the actuator is in the second position. 
     
     
         6 . The power tool of  claim 5 , wherein the electromagnet comprises a first electromagnet adjacent to the first position and a second electromagnet adjacent to the second position, such that when one of the first electromagnet and the second electromagnet is energized, the actuator moves from the first position to the second position, and when the other of the first electromagnet and the second electromagnet is energized, the actuator moves from the second position to the first position. 
     
     
         7 . The power tool of  claim 6 , further comprising a control circuit configured to control energization of the first and second electromagnets in response to an input condition, the input condition comprising one of a user selection of a desired power tool operating condition and a sensed power tool operating condition. 
     
     
         8 . The power tool of  claim 1 , wherein the actuator, the positioning member, and the electromagnet comprise a portion of a clutch, the clutch having an input member coupled to the transmission, an output member coupled to the output shaft, and a coupling device movable between a driving position in which torque is transmitted from the input member to the output member and a clutching position in which torque transmission from the input member to the output member is interrupted, and wherein when the actuator is in the first position, the actuator retains the coupling member in the driving position, and when then actuator is in the second position, the actuator allows the coupling member to move to the clutching position. 
     
     
         9 . The power tool of  claim 8 , wherein the input member comprises an input sleeve defining a radial bores, the output member comprises an output cylinder received in the input sleeve defining a groove, the coupling member comprises a drive ball received in the bore, and the actuator comprises a actuation sleeve received over the input sleeve, wherein when the actuation sleeve is in the first position, the ball is retained in the groove to transmit torque from the input sleeve to the output cylinder, and when the actuation sleeve is in the second position, the ball is permitted to escape the groove to interrupt torque transmission from the input sleeve to the output cylinder. 
     
     
         10 . The power tool of  claim 8 , wherein the input member comprises a ring gear of the transmission having a recess, the output member comprises a portion of the output shaft, the actuator comprises a sleeve, and the coupling member comprises a leg extending from the sleeve, wherein when the sleeve is in the first position, the leg engages the recess to inhibit rotation of the ring gear, which enables torque transmission to the output member, and when the sleeve is in the second position, the leg does not engage the recess to allow rotation of the ring gear, which interrupts torque transmission to the output member. 
     
     
         11 . The power tool of  claim 1 , wherein the actuator, the positioning member and the electromagnet comprise a portion of a tool holder, the tool holder coupled to the output shaft for releasably retaining a power tool accessory, wherein when the actuator is in the first position, the accessory is retained by the tool holder, and when the actuator is in the second position the accessory is releasable from the tool holder. 
     
     
         12 . The power tool of  claim 11 , wherein the tool holder comprises a socket drive having a retractable retention pin and a linkage coupled to the retention pin for selectively retracting the retention pin, and wherein the actuator comprises a ring configured to move the linkage and the retention pin between a retention position and a release position when the actuator is in the first position and the second position, respectively. 
     
     
         13 . The power tool of  claim 1 , further comprising a stop to prevent contact between the actuator and the positioning member when the actuator is in the first position. 
     
     
         14 . A mode change mechanism for a power tool, the mode change mechanism comprising:
 an actuator including a permanent magnet and being moveable between a first position for a first mode of operation of the power tool, and a second position a second, different mode of operation of the power tool;   a first positioning member adjacent the first position and composed of a ferromagnetic material to attract the permanent magnet when the actuator is in the first position;   a second positioning member adjacent the second position and composed of a ferromagnetic material to attract the permanent magnet when the actuator is in the second position; and   an electromagnet configured to be energized to move the actuator between the first position and the second position, wherein (i) when the electromagnet is not energized and the actuator is in the first position. the actuator is retained in the first position, (ii) when the electromagnet is not energized and the actuator is in the second position, the actuator is retained in the second position, and (iii) when the electromagnet is energized, the actuator moves from one of the first and second positions to the other of the first and second positions.   
     
     
         15 . The mode change mechanism of  claim 13 , wherein the electromagnet comprises a first electromagnetic coil adjacent the first position, and a second electromagnetic coil adjacent the second position. 
     
     
         16 . The mode change mechanism of  claim 14 , wherein energizing the first electromagnetic coil creates a magnetic force to move the permanent magnet and the actuator away from the first positioning member to the second position, and energizing the second electromagnetic coil creates a magnetic force to move the permanent magnet and the actuator away from second positioning member ember and to the first position. 
     
     
         17 . The mode change mechanism of  claim 13 , wherein energizing the electromagnet by causing current to flow in a first direction creates a magnetic force to move the permanent magnet and the actuator away from the first positioning member and to the second position, and energizing the electromagnet by causing current to flow in a second opposite direction creates a magnetic force to move the permanent magnet and the actuator away from the second positioning member and to the first position. 
     
     
         18 . The mode change mechanism of  claim 13 , further comprising a first stop to prevent contact between the actuator and the first positioning member when in the first position, and a second stop to prevent contact between the actuator and the second positioning member when in the second position. 
     
     
         19 . A method of operating a mode change mechanism of a power tool, the method comprising:
 determining whether the power tool should be operating in a first mode of operation or a second mode of operation;   determining whether an actuator that includes a permanent magnet is in a first position that causes the power tool to operate in the first mode of operation or a second position that causes the power tool to operation in the second mode of operation;   energizing an electromagnet to cause the actuator and the permanent magnet to move between the first position and the second position if the actuator is in the first position and the power tool should be operating in the second mode of operation, or if the actuator is in the second position and the power tool should be operating in the first mode of operation;   retaining the actuator, without energizing the electromagnet, in the first position if the actuator is in the first position and the power tool should be operating in the first mode of operation, or in the second position if the actuator is in the second position and the power tool should be operating in the second mode of operation.   
     
     
         20 . The method of  claim 17 , wherein retaining the actuator comprises providing a first ferromagnetic positioning member adjacent the first position to attract the permanent magnet when the actuator is in the first position, and providing a second ferromagnetic positioning member adjacent the second position to attract the permanent magnet when the actuator is in the second position. 
     
     
         21 . The method of  claim 17 , wherein energizing the electromagnet comprises energizing a first electromagnetic coil adjacent the first position to create a magnetic force that moves the permanent magnet and the actuator away from the first position to the second position when the actuator is in the first position and should be in the second position, and energizing a second electromagnetic coil adjacent the second position to create a magnetic force that moves the permanent magnet and the actuator away from the second position to the first position when the actuator is in the second position and should be in the first position. 
     
     
         22 . The method of  claim 17 , wherein energizing the electromagnet comprises causing current to flow through the electromagnet in a first direction to create a magnetic force that moves the permanent magnet and the actuator away from the first position to the second position when the actuator is in the first position and should be in the second position, and causing current to flow through the electromagnet in a second opposite direction to create a magnetic force that moves the permanent magnet and the actuator away from the second position to the first position when the actuator is in the second position and should be in the first position.