Patent Publication Number: US-11393646-B2

Title: Hand held rotary power tool

Description:
BACKGROUND 
     Hand-held rotary power tools may include a motor having an output shaft to which tools and/or accessories may be attached. For example, a wide range of accessories may be interchangeably connected to the output shaft, including bits, grinding wheels, buffing pads, scrubbing pads, etc. The motor is powered by a power supply, and operation of the motor is controlled by an on/off switch disposed in an electrical circuit that connects the motor to the power supply. 
     Some small hand held rotary power tools have an on/off switch of the type that employs a sliding activation motion. In some circumstances, sliding on/off switches may be inadvertently actuated. For example, such an inadvertent actuation can occur as a result of the tool being accidentally dropped in such a way that the switch is impacted. In this situation, the power tool may be turned on while not being held by an operator. Moreover, if a shaping accessory such as a bit, grinding wheel, scrubbing pad, etc. is attached to the output shaft, the power tool may damage the environment if the power tool is turned on while not being held by an operator. For at least this reason, it is desirable to prevent inadvertent actuation of the on/off switch. 
     SUMMARY 
     In some aspects, a power tool includes a tool housing. The tool housing includes a wall portion, and the wall portion includes a switch opening that is defined by a wall edge that extends between an outer surface of the wall and an inner surface of the wall. The power tool includes a motor disposed in the tool housing, and a power supply that is connected to the motor via an electrical circuit. The electrical circuit is disposed in the tool housing. The power tool includes an electrical switch disposed in the electrical circuit. The electrical switch includes a switch body and a contact element that protrudes from the switch body. The contact element is movable relative to the switch body between a first switch position in which the electrical circuit is open and current is prevented from flowing from the power supply to the motor, and a second switch position in which the electrical circuit is closed and current flows from the power supply to the motor. The power tool also includes a switch actuator that is disposed in tool housing so as to be accessible to an operator of the tool via the switch opening. The switch actuator includes a guide plate that is disposed in the tool housing, and a resilient arm that extends from, and is integrally formed with, the guide plate. The switch actuator is moveable relative to the tool housing between a first actuator position and a second actuator position. When the switch actuator is in the first actuator position, the guide plate is disposed inward relative to an inner surface of the wall portion, a first edge portion of the guide plate is positioned at a first guide plate position relative to the tool housing, the resilient arm is offset relative to the guide plate a first distance so as to protrude into the switch opening, and a portion of an edge of the resilient arm is engaged with the wall edge. When the switch actuator is in the second actuator position, the guide plate is disposed inward relative to the inner surface of the wall portion, the first edge portion of the guide plate is positioned at a second guide plate position relative to the tool housing, the second guide plate position is longitudinally spaced apart from the first guide plate position, the resilient arm is offset relative to the guide plate a second distance, and the second distance is less than the first distance whereby the portion of an edge of the resilient arm is disengaged from the wall edge and is disposed inward relative to the inner surface of the wall portion. In addition, the switch actuator cooperates with the contact element in such a way that when the switch actuator is in the first actuator position, the contact element is in the first switch position, and when the switch actuator is in the second actuator position, the contact element is in second switch position. 
     In some embodiments, the switch actuator is actuated by applying a bi-directional manual force to the resilient arm. 
     In some embodiments, movement of the switch actuator between the first actuator position and the second actuator position requires a first movement in a first direction followed by a second movement in a second direction, and the second direction is perpendicular to the first direction. 
     In some embodiments, the guide plate comprises a central opening that is defined by an inner edge, and the resilient arm protrudes from the inner edge. 
     In some embodiments, the resilient arm includes a lever portion and a ramp portion that connects the lever portion to the inner edge, and the ramp portion is angled relative to an outward facing surface of the guide plate whereby the lever portion is offset relative to the guide plate. 
     In some embodiments, the switch actuator is a spring. 
     In some embodiments, the guide plate includes a toggle opening. In addition, when the switch actuator is in the first actuator position, a portion of the contact element extends into the offset opening whereby the electrical switch is positioned in the first switch position, and when the switch actuator is in the second actuator position, the portion of the contact element abuts an inward facing surface of the guide plate, whereby the electrical switch is positioned in the second switch position. 
     In some embodiments, when the switch actuator is in the first actuator position, the resilient arm is biased toward the wall edge such that the portion of an edge of the resilient arm engages the wall edge, thereby preventing movement of the switch actuator to the second actuator position. In addition, when the switch actuator is in the second actuator position, the portion of an edge of the resilient arm is displaced from the wall edge, thereby permitting movement of the switch actuator to the second actuator position. 
     In some embodiments, the tool housing includes a shelf that protrudes from the wall portion and at least partially underlies the switch opening, and the switch actuator is supported on, and is slideable relative to, the shelf. 
     In some embodiments, the shelf includes an opening, and the contact element protrudes through the opening. 
     In some embodiments, the tool housing includes a pair of locating ribs that protrude from the wall portion toward the switch actuator, the locating ribs extending in a direction that is perpendicular a movement direction of the switch actuator. The guide plate includes a second edge portion and a tab that protrudes from the second edge portion. When the switch actuator is in the first actuator position, the tab abuts a first rib of the pair of locating ribs, and the first rib of the pair of locating ribs is disposed between the tab and the second rib of the pair of locating ribs. In addition, when the switch actuator is in the second actuator position, the tab is disposed between the first rib of the pair of locating ribs and a second rib of the pair of locating ribs. 
     In some embodiments, the resilient arm comprises an outward-facing surface, and a platform that protrudes from the outward-facing surface. The platform is shaped and dimensioned to be received within the switch opening regardless of switch actuator position, and the platform includes surface features that enhance gripping of the platform by a user of the power tool. 
     A hand-held rotary power tool includes a motor and a power supply that are connected by a switch disposed in an electrical circuit. The switch controls the on/off state of the motor and is actuated by a switch actuator that serves as a spring element. The switch actuator includes a guide plate supported on the housing, and a resilient arm that protrudes from the guide plate into an opening in the tool housing. When the switch actuator is in a first actuator position relative to the housing, the resilient arm is biased toward an edge of the opening and engages the edge, thereby preventing inadvertent movement of the switch actuator to the second actuator position. When the switch actuator is actuated by applying a bi-directional manual force to the resilient arm, the resilient arm is displaced from the edge, thereby permitting movement of the switch actuator to the second actuator position. 
     The switch actuator is made out of molded plastic, and is designed to act as a spring. The switch actuator requires two movements from the user to be moved relative to the tool housing and actuate the switch that controls the on/off state of the motor. The first movement is inward, achieved by the user applying a radially directed force to the switch actuator, achieved by pressing the actuator switch inward using a tip of a finger. This movement detaches the actuator switch from engagement with the tool housing. The second movement is longitudinal, achieved by the user applying a longitudinally directed force to the switch actuator, achieved by moving the actuator longitudinally using a tip of a finger. The second movement can only be performed after the first movement. Although an impact load applied to the switch actuator, caused for example by dropping the power tool onto the switch actuator, may inadvertently achieve the first movement, it is unlikely that the subsequent second movement would result during the impact, whereby the switch actuator would prevent an inadvertent change in operating state of the power tool. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top perspective view of the hand-held rotary power tool including a switch actuator. 
         FIG. 2  is a perspective view of the power tool of  FIG. 1 , illustrated with a portion of the tool housing removed to permit visualization of the internal components of the power tool. 
         FIG. 3  is a schematic diagram illustrating the electrical circuit provided in the power tool of  FIG. 1 . 
         FIG. 4  is a top view of a portion of the power tool of  FIG. 1 . 
         FIG. 5  is a side view of a portion of the tool housing of the power tool of  FIG. 1 . 
         FIG. 6  is a perspective view of a portion of the power tool of  FIG. 1 , illustrated with a portion of the tool housing removed to permit visualization of the internal components of the power tool and showing the switch actuator in the first actuator position. 
         FIG. 7  is another perspective view of a portion of the power tool of  FIG. 1 , illustrated with a portion of the tool housing and some internal components removed to permit visualization of switch actuator and showing the switch actuator in the second actuator position. 
         FIG. 8  is a perspective view of the switch actuator, shown in a configuration corresponding to the first actuator position. 
         FIG. 9  is a side view of the switch actuator, shown in a configuration corresponding to the first actuator position. 
         FIG. 10  is a perspective view of the switch actuator, shown in a configuration corresponding to the second actuator position. 
         FIG. 11  is a side view of the switch actuator, shown in a configuration corresponding to the second actuator position. 
         FIG. 12  is a cross sectional view of the power tool of  FIG. 1 , as seen along line  12 - 12  of  FIG. 6 , illustrated with a portion of the tool housing and some internal components removed to permit visualization of switch actuator in the first actuator position. 
         FIG. 13  is a cross sectional view of the power tool of  FIG. 1 , as seen along line  13 - 13  of  FIG. 7 , illustrated with a portion of the tool housing and some internal components removed to permit visualization of switch actuator in the second actuator position. 
         FIG. 14  is another perspective view of the hand-held rotary power tool of  FIG. 1 . 
         FIG. 15  is a front view of the hand-held rotary power tool of  FIG. 1 . 
         FIG. 16  is a rear view of the hand-held rotary power tool of  FIG. 1 . 
         FIG. 17  is a left side view of the hand-held rotary power tool of  FIG. 1 . 
         FIG. 18  is a right side view of the hand-held rotary power tool of  FIG. 1 . 
         FIG. 19  is a top view of the hand-held rotary power tool of  FIG. 1 . 
         FIG. 20  is a bottom view of the hand-held rotary power tool of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-3 , a hand-held rotary power tool  1  includes an electric motor  22  disposed in a tool housing  2 . The tool housing  2  has a generally cylindrical shape that is ergonomically contoured to be grasped in the hand of a user, whereby the tool housing  2  serves as a handle of the power tool  1 . An output shaft  23  of the electric motor  22  extends in parallel to a longitudinal axis  21  of the tool housing  2 , and is connected in a gearless fashion to a threaded tool spindle  24 . The tool spindle  24  protrudes outward from a first end  3  of the tool housing  2 , and is configured to provide a mechanical connection to various accessories (not shown) for the purpose of processing a workpiece. The accessories may include, but are not limited to, an engraving cutter, a milling cutter, a grinding disk, a grindstone, a polishing tip, a polishing disk, a polishing brush, a cutter disk, a saw blade and a drill. The electric motor  22  is powered by a power supply  44  that is detachably connected to a second end  4  of the tool housing  2 . The power supply  44  is connected to the electric motor  22  via an electric circuit  26  that is disposed in the tool housing  2 . The power tool  1  includes an electrical switch  38  that is disposed in the electrical circuit and controls the on-off state of the electric motor  22 . The electrical switch  38  is entirely disposed within the tool housing  2 , and is actuated by an operator of the power tool  1  via a switch actuator  50 . The switch actuator  50  is disposed in tool housing  2  so as to be accessible to an operator of the power tool  1  via a switch opening  16  provided in the tool housing  2 . The switch actuator  50  cooperates with the electrical switch  38  in such a way that movement of the switch actuator  50  relative to the tool housing  2  results in a change in the on-off state of the electrical switch  38 . Thus, the switch actuator  50  is used by the operator of the power tool  1  to control the on-off state of the power tool  1 . The switch actuator  50  includes a guide plate  51  that is disposed in the tool housing  2 , and a resilient arm  66  that extends from, and is integrally formed with, the guide plate  51 . The resilient an  66  protrudes into the switch opening  16  so as to be accessible to the operator of the power tool  1 . The switch actuator  50  is configured to prevent inadvertent actuation of the electrical switch  38 , as will be described in detail below. 
     In the illustrated embodiment, the power supply  44  includes a rechargeable battery pack  45  that is detachably connected to the tool housing second end  4 . In other embodiments, the power supply  44  may consist of primary batteries that are housed within the tool housing  2 . In still other embodiments, the power supply  44  may be remote from the tool housing  2 , and connected to the tool housing  2  via a cord (not shown) that encloses an electrically conductive wire. 
     The electrical switch  38  includes a switch body  39  and a contact element  40  that protrudes from the switch body  39 . In the illustrated embodiment, the contact element  40  is an elongated lever arm that is used to toggle the electrical switch  38  between first and second positions via a change in angle of the contact element  40  relative to the switch body  39 . In particular, the contact element  40  is movable via the switch body  39  between a first switch position, represented in  FIG. 3  by broken line  38 ( 1 ), in which the electrical circuit is open and current is prevented from flowing from the power supply  44  to the motor  22 , and a second switch position. In the second switch position, represented in  FIG. 3  by broken line  38 ( 2 ), the electrical circuit is closed and current flows from the power supply  44  to the motor  22 . In the illustrated embodiment, the electrical switch  38  is supported within the tool housing  2  in an orientation in which the contact element  40  is movable in a plane that is parallel to the tool housing longitudinal axis  21 . 
     When the electrical switch  38  is in the second switch position, the electric motor  22  drives the tool spindle  24  at a rotational speed higher than 10 000 min-1. In some embodiments, the rotational speed of the electric motor  22  can be adjusted by an operator between 10 000 min-1 and 40 000 min-1 via a rotary speed control knob  42 . 
     The power tool  1  includes an output shaft lock mechanism  28  having a depressible control button  29  that caps a locking shaft  30 . The locking shaft  30 , when actuated by the control button  29 , is configured to engage an opening  31  in the output shaft  23  to prevent rotation of the output shaft  23  while an accessory is being attached thereto. The output shaft lock mechanism  28  also includes a spring  33  that biases the locking shaft  30  and control button  29  toward a disengaged configuration. 
     The tool housing  2  encloses the motor  22 , the electrical switch  38 , the switch actuator  50 , the output shaft lock mechanism  28 , the speed control knob  42 , output shaft support bearings  26 , a printed circuit board  34  that supports a controller  35  and other ancillary components and structures. The controller  35 , for example, may control a voltage supplied to the electric motor  22 . 
     In the illustrated embodiment, the tool housing longitudinal axis  21  extends between the opposed tool housing first and second ends  3 ,  4 , and is parallel to the motor output shaft  23 . In addition, the tool housing  2  is elongated along the longitudinal axis  21 . The tool housing  2  is a thin-walled structure that includes two wall portions, or “half shells,”  5 ,  6  that fit together to enclose the other components of the power tool  1 . The wall portions  5 ,  6  form left and right sides of the tool housing  2  that are joined along a seam  7  that extends longitudinally along the top and bottom of the power tool  1 , where the terms “top” and “bottom” are used with respect to the orientation illustrated in  FIG. 2 , and are not intended to be limiting. The wall portions  5 ,  6  are generally mirror images of each other. In  FIGS. 2 and 5-7 and 12-13 , only the wall portion  5  is shown, while the other wall portion  6  is omitted to permit visualization of the components that are located inside of the housing and/or the structure of the interior of the housing. 
     Referring also to  FIGS. 4-5 , the tool housing  2  includes a switch opening  16  that receives the switch actuator  50  and is disposed on the top of the tool housing  2  at a location coinciding with the seam  7 . The switch opening  16  is located between the tool housing first end  3  and a midpoint between the tool housing first and second ends  3 ,  4 . The switch opening  16  is defined by a wall edge  18  that extends between an outer surface  19  of the tool housing  2  and an inner surface  20  of the tool housing  2 . The switch opening  16  is rectangular in profile when the tool housing  2  is viewed facing the top, and is elongated in a direction parallel to the longitudinal axis  21 . The wall edge  18  includes a first end portion  18 ( 1 ) that extends perpendicular to the longitudinal axis  21 , and a second end portion  18 ( 2 ) that is opposed to the first end portion  18 ( 1 ). The first end portion  18 ( 1 ) is disposed between the second end portion  18 ( 2 ) and the tool housing first end  3 . In addition, the wall edge  18  includes a first side portion  18 ( 3 ) that extends between the first and second end portions  18 ( 1 ),  18 ( 2 ) and is defined in the first wall portion  5 , and a second side portion  18 ( 4 ) that is parallel to the first side portion  18 ( 3 ) and is defined in the second wall portion  6 . The first end portion  18 ( 1 ) of the wall edge  18  includes a recess  18 ( 5 ) at the intersection between the wall edge  18  and the tool housing inner surface  20 . The recess  18 ( 5 ) provides an abutment surface that cooperates with a portion of the switch actuator  50  when the switch actuator  50  is in a first actuator position, as discussed in more detail below. 
     The tool housing  2  includes a knob opening  43  that receives the rotary speed control knob  42 . The knob opening  43  is disposed on the top of the tool housing  2  at a location coinciding with the seam  7 . The knob opening  43  is located between the tool housing second end  4  and the switch opening  16 . 
     The tool housing  2  includes a control button opening  32  that receives the depressible control button  29  of the shaft lock mechanism  28 . The control button opening  32  is disposed on the top of the tool housing  2  at a location coinciding with the seam  7 . The control button opening  32  is located between the tool housing first end  3  and the switch opening  16 . 
     The tool housing  2  includes a shelf  8  that protrudes from opposed portions of the wall portions  5 ,  6  in such a way that the shelf  8  is parallel to, and underlies, the switch opening  16 . The shelf  8  is generally planar, and has a longitudinal dimension that is greater than the longitudinal dimension of the switch opening  16 , whereby the shelf first end  8 ( 1 ) is aligned with the control button opening  32 , and the shelf second end  8 ( 2 ), which is opposed to the shelf first end  8 ( 1 ), is disposed between the switch opening  16  and the knob opening  43 . A switch opening-facing surface  13  of the shelf  8  includes low profile, flat-topped ridges  11 . The ridges  11  extend in a direction perpendicular to the longitudinal axis  21 , and are spaced apart along the longitudinal axis  21 . In use, the switch actuator  50  is supported on the ridges, and when the switch actuator  50  is actuated, the switch actuator  50  slides longitudinally along the shelf  8 , whereby the ridges  11  serve to provide a reduced friction sliding surface and to wipe debris from the facing surface  55  of the switch actuator  50 , which is collected in the space between adjacent ridges  11 . 
     The shelf  8  includes an opening  12  that is shaped and dimensioned to allow the contact element  40  to pass therethrough. The opening  12  is longitudinally positioned closer to the shelf second end  8 ( 2 ) than the shelf first end  8 ( 1 ), whereby it is aligned with the second end portion  18 ( 2 ) of the wall edge  18  that defines the switch opening  16 . 
     The tool housing  2  includes a stop wall  9  and a leveling wall  10  that protrude inward and extend in a direction perpendicular to the shelf  8 . The stop wall  2  is connected to the shelf second end  8 ( 2 ), and limits the movement of the switch actuator  50  toward the tool housing second end  4 . The leveling wall  10  is disposed between the stop wall  9  and the switch opening  16 . The leveling wall  10  protrudes toward the shelf  8 , but is spaced apart from the shelf  8 . The gap between the leveling wall  10  and the shelf  8  is dimensioned to receive a portion of the switch actuator  50  with a clearance fit. By this configuration, the leveling wall  10  maintains the switch actuator  50  in a desired orientation relative to the tool housing  2 , for example by preventing tilting of the switch actuator  50  relative to the shelf  8 . 
     The tool housing  8  includes a pair of locating ribs  14 ,  15  that protrude from each of opposed portions of the wall portions  5 ,  6  toward the peripheral edge  56  of the switch actuator  50 . To this end, the locating ribs  14 ,  15  are disposed adjacent to the switch opening-facing surface  13  of the shelf  8 . The locating ribs  14 ,  15  are longitudinally spaced apart, and provide a corrugated structure that is configured to engage with a corresponding locating tab  64  that protrudes from the peripheral edge  56  of the switch actuator  50 , as discussed in more detail below. 
     Referring to  FIGS. 6 and 7 , the switch actuator  50  is disposed in tool housing  2  in such a way as to be supported on the shelf  8 , and to partially protrude into the switch opening  16 . The switch actuator  50  includes a planar guide plate  51  that rests on the shelf  8 , and a resilient arm  66  that is integrally formed with the guide plate  51 . A portion of the resilient arm  66  extends into the switch opening  16 . The switch actuator  50  will now be described in detail. 
     Referring also to  FIGS. 8-11 , the guide plate  51  includes an outward-facing surface  54  (e.g., a switch opening-facing surface), an inward-facing, surface  55  (e.g., a motor-facing surface) that is opposed to the outward-facing surface  54 , and a peripheral edge  56  that extends between the outward-facing surface  54  and the inward-facing surface  55 . The peripheral edge  56  includes a front end portion  56 ( 1 ) that faces the tool housing first end  3 , and a rear end portion  56 ( 2 ) that is opposed to the front end portion  56 ( 1 ) and faces the tool housing second end  4 . The peripheral edge  56  includes a first side portion  56 ( 3 ) that extends between the front and rear end portions  56 ( 1 ),  56 ( 2 ) on one side of the guide plate  51 , and a second side portion  56 ( 4 ) that extends between the front and rear end portions  56 ( 1 ),  56 ( 2 ) on the opposed side of the guide plate  51 . 
     The guide plate  51  includes a pair of guide rails  63  that protrude longitudinally from the front end portion  56 ( 1 ) of the peripheral edge  56 . The guide rails  63 ,  63  are spaced apart in a direction perpendicular to the longitudinal axis  21 . In the second actuator position, discussed further below, the guide rails  63  protrude into shaft lock mechanism  28  in such a way that a guide rail  63  is disposed on each of opposed sides of the control button  29  ( FIG. 7 ). 
     Referring to  FIGS. 12-13 , the guide plate  51  includes a locating tab  64  that protrudes outward from each of the first and second side portions  56 ( 3 ),  56 ( 4 ) of the peripheral edge  56 . The locating tabs  64  are disposed at a location along the peripheral edge first and second side portions  56 ( 3 ),  56 ( 4 ) that is closer to the rear end portion  56 ( 2 ) than the front end portion  56 ( 1 ). The locating tabs  64  have a rounded profile when viewed from above, and each locating tab  64  is configured to engage with a corresponding pair of locating ribs  14 ,  15 . To this end, a longitudinal dimension of each locating tab  64  is less than the spacing between the locating ribs  14 ,  15 . In particular, when the switch actuator  50  is in the first actuator position, the locating tab  64  is disposed between the first rib  14  and the second rib  15  of the respective pair of locating ribs  14 ,  15 , and when the switch actuator  50  is in the second actuator position, the locating tab  64  abuts a rearward-facing surface of the first rib  14  of the respective pair of locating ribs  14 ,  15 . 
     The interaction between a locating tab  64  and the respective pair of locating ribs  14 ,  15  provides a detenting or clicking action so that the user can easily feel movement that is being made by the switch actuator  50  during operation. The interaction between a locating tab  64  and the respective pair of locating ribs  14 ,  15  also holds the switch actuator  50  in its desired location. The detenting action provides a sufficient level of resistance to initial movement that the likelihood that the switch actuator  50  will move without a conscious force being applied to it is small. If the switch actuator  50  is being used in a hand-held rotary power tool such as a Dremel™ tool, normal vibration experienced during operation of the power tool  1  should not affect the position of the switch actuator  50 . 
     Referring again to  FIGS. 8-11 , the guide plate  51  includes a guiding tab  65  that protrudes outward from each of the peripheral edge first and second side portions  56 ( 3 ),  56 ( 4 ). The guiding tabs  64  are disposed at a location along the peripheral edge first and second side portions  56 ( 3 ).  56 ( 4 ) that is between the rear end portion  56 ( 2 ) and a respective locating tab  64 . The guiding tabs  65  have a greater longitudinal dimension than the locating tabs  64 , and each guiding tab  65  has a generally rectangular profile when viewed from above. 
     In addition, the guide plate  51  includes a central opening  60  that is spaced apart from, and surrounded by, the peripheral edge  56 . The central opening  60  is defined by an inner edge  61  that extends between the outward facing surface  54  and the inward facing surface  55 . The central opening  60  has a width dimension (e.g., a dimension perpendicular to the longitudinal axis  21 ) that greater than a width dimension of the switch opening  16 , and has a length dimension (e.g., a dimension parallel to the longitudinal axis  21 ) that is greater than a length dimension of the switch opening  16 . 
     The resilient arm  66  protrudes from a connection portion  62  of the inner edge  61 . The connection portion  62  is the portion of the inner edge  61  that is parallel to, and closest to, the rear end portion  56 ( 2 ) of the guide plate peripheral edge  56 . 
     The resilient arm  66  has a generally rectangular peripheral shape when the switch actuator  50  is viewed from above, and has dimensions that are slightly less than the corresponding dimensions of the central opening  60 . As a result, the lever portion  68  of the resilient arm  66  can be moved into the guide plate central opening  60  upon application of an external force thereto ( FIGS. 10-11 ). Upon release of an external force, the lever portion  68  elastically returns to the configuration in which it resides outside the central opening  60  and is offset from the guide plate  51  ( FIGS. 8-9 ). 
     The resilient arm  66  includes a lever portion  68  and a ramp portion  69  that connects the lever portion  68  to the connection portion  62  of the inner edge  61 . The lever portion  68  has a fixed end  82  that is contiguous with the ramp portion  69 , and a free end  83  that is opposed to the fixed end  82  and faces the tool housing first end  3 . 
     The ramp portion  69  is angled relative to the outward-facing surface  54  of the guide plate  51  and the lever portion  68 , whereby the lever portion  68  is offset relative to, and extends parallel to, the guide plate  51  when the switch actuator  50  is free of external loads ( FIGS. 8 and 9 ). In particular, the lever portion  68  is closer to the switch opening  16  than the guide plate  51  when the switch actuator  50  is free of external loads. 
     The lever portion  68  of the resilient arm  66  includes a platform  81  that protrudes outward (e.g., toward the switch opening  16 ) from an outward-facing surface  80  of the lever portion  68 . The platform  81  has a rectangular profile when the switch actuator  50  is viewed from above. The platform  81  has a width dimension (e.g., a dimension perpendicular to the longitudinal axis  21 ) that is slightly less than a width dimension of the switch opening  16 . For example, the platform  81  may have a width dimension that provides a clearance fit with respect to the facing portions  18 ( 3 ),  18 ( 4 ) of the wall edge  18 . The platform  81  has a length dimension that is less than a length dimension of the switch opening  16 . For example, the length of the platform  81  is set so that a gap g exists between an end of the platform  81  and the switch opening  16 , and a length of the gap g is at least a longitudinal travel distance of the switch actuator  50  when moving between the first actuator position and the second actuator position. When the switch actuator  50  is in the first actuator position, the gap g is disposed between a first end  81 ( 1 ) of the platform and the first end portion  18 ( 1 ) of the wall edge  18  ( FIG. 6 ). In addition, when the switch actuator  50  is in the second switch actuator position, the gap g is disposed between a second end  81 ( 2 ) of the platform and the second end portion  18 ( 2 ) of the wall edge  18  ( FIG. 7 ). By this configuration, the platform  81  resides in the switch opening  16  regardless of switch actuator position. 
     The outward-facing surface  84  of the platform  81  includes surface features that enhance gripping of the platform  81  by a fingertip of a user of the power tool  1 . In the illustrated embodiment, the surface features include a finger ridge  85  that extends in a width direction of the platform  81 . The finger ridge  85  is shaped and dimensioned to receive a fingertip so as to facilitate application of a longitudinal force by a user to the switch actuator  50 . To this end, the finger ridge  85  has concavely rounded surfaces  85 ( 1 ),  85 ( 2 ) that extend between a terminal edge  86  of the ridge and the outward-facing surface  84  of the platform  81 . More specifically, the finger ridge  85  has a first rounded surface  85 ( 1 ) that faces the wall edge first end portion  18 ( 1 ), and a second rounded surface  85 ( 2 ) that faces the wall edge second end portion  18 ( 2 ). The finger ridge  85  has a height dimension sufficient that a top edge of the finger ridge is flush with the tool housing outer surface  19  when the switch actuator is in the first actuator position. In addition to the finger ridge  85 , the outward-facing surface  84  of the platform  81  may also include surface features that increase surface friction of the platform outward facing surface  84 , such as a series of closely-spaced, shallow grooves or knurling (not shown). 
     The guide plate  51  includes a toggle opening  88  that is disposed along the connection portion  62  of the inner edge  61 , whereby the toggle opening  88  extends into both the guide plate  51  and the ramp portion  69 . The toggle opening  88  is shaped and dimensioned to receive a terminal end  41  of the contact element  40  in certain positions of the switch actuator  50 . In the illustrated embodiment, the toggle opening  88  has a rectangular profile when viewed from above, but is not limited to this shape. 
     In the illustrated embodiment, the switch actuator  50  is a monolithic structure that is formed of plastic in an injection molding process. 
     The switch actuator  50  is used by the operator of the power tool  1  to control the on-off state of the power tool  1  by moving the switch actuator  50  relative to the tool housing  2  between the first actuator position ( FIGS. 6, 8-9 and 12 ) and the second actuator position ( FIGS. 7, 10-11 and 13 ). During this movement, the switch actuator  50  translates both longitudinally and radially. As used herein, the terms “longitudinally” and “radially” refer to movement directions that are made relative to the longitudinal axis  21 . In particular, the term “longitudinally” refers to a movement that is parallel to the longitudinal axis  21 , and the term “radially” refers to a movement that is perpendicular to the longitudinal axis  21 . 
     Referring to  FIGS. 6, 8-9 and 12 , in the first actuator position, the switch actuator  50  is disposed in the tool housing as follows: The guide plate  51  rests on the shelf  8  such that the guide plate  51  is disposed radially inward relative to the inner surface  20  of the tool housing  2 , and the rear end portion  56 ( 2 ) of the guide plate  51  is positioned abutting the stop wall  9 . In addition, the front end portion  56 ( 1 ) of the guide plate  51  is disposed between the wall edge first end portion  18 ( 1 ) and the control button opening  32 , and guide rails  63  are longitudinally spaced apart from the shaft lock mechanism control button  29 . The resilient arm  66  is offset radially relative to the guide plate  51  a first distance d 1  ( FIG. 9 ) so that the platform  81  protrudes into the switch opening  16 . The free end  83  of the lever portion  68  of the resilient arm  66  is engaged with the wall edge recess  18 ( 5 ) in such a way that the switch actuator  50  is prevented from longitudinal motion toward the tool housing first end  3 . In other words, the switch actuator  50  is retained in the first actuator position the engagement between the lever portion free end  83  and the wall edge recess  18 ( 5 ). In addition, the locating tabs  64  abut a rearward-facing surface of the first rib  14  of the respective pair of locating ribs  14 ,  15 . 
     The switch actuator  50  cooperates with the contact element  40  in such a way that when the switch actuator  50  is in the first actuator position, the contact element  40  is in the first switch position. In particular, when the switch actuator  50  is in the first actuator position, the terminal end  41  of the contact element  40  extends into the toggle opening  88  ( FIGS. 6 and 12 ), whereby the contact element  40  is at a first angle relative to the switch body  39  and the electrical switch  38  is positioned in the first switch position, e.g., an open position wherein electrical current does not flow between the power supply  44  and the electric motor  22 . 
     Referring to  FIGS. 7, 10-11 and 13 , in the second actuator position, the switch actuator is displaced longitudinally toward the tool housing first end  3  relative to the first actuator position. The user moves the switch actuator  50  from the first actuator position to the second actuator position by placing a fingertip on the second rounded portion  85 ( 2 ) of the lever portion  68  of the resilient arm  66  and applying a radially inward force that results in a first, radial movement (represented by arrow A 1 ) followed by a longitudinally forward force that results in a second, longitudinal movement (represented by arrow A 2 ) ( FIG. 11 ). In the illustrated embodiment, the radial and longitudinal movements are perpendicular. As a result of the applied forces A 1 , A 2 , the lever portion  68  moves toward the guide plate  51 , and is partially received in the central opening  60 . In addition, the guide plate  51  is moved toward the tool housing first end  3 . 
     More particularly, in the second actuator position, the switch actuator  50  is disposed in the tool housing as follows: The guide plate  51  rests on the shelf  8  such that the guide plate  51  is disposed radially inward relative to the inner surface  20  of the tool housing  2 , and the rear end portion  56 ( 2 ) of the guide plate  51  is longitudinally spaced apart from the stop wall  9 . The front end portion  56 ( 1 ) of the guide plate  51  is disposed between the wall edge first end portion  18 ( 1 ) and the control button opening  32 , and closer to the control button opening than when in the first actuator position. As a result, the guide plate guide rails  63  protrude into the shaft lock mechanism  28  in such a way that a guide rail  63  is disposed on each of opposed lateral sides of the control button  29 , and a portion of the control button  29  is disposed between the guide rails  63 . The resilient arm  66  is radially offset relative to the guide plate  51  a second distance d 2  ( FIG. 11 ). The second distance d 2  is less than the first distance d 1 , whereby the free end  83  of the lever portion  68  is disengaged from the wall edge recess  18 ( 5 ). In particular, lever portion free end  83  is disposed inward relative to the inner surface  20  of the tool housing  2 , and is also disposed between the wall edge first end portion  18 ( 1 ) and the control button opening  32 . In addition, the locating tabs  64  are disposed between the first rib  14  and the second rib  15  of the respective pair of locating ribs  14 ,  15 . 
     The switch actuator  50  cooperates with the contact element  40  in such a way that when the switch actuator  50  is in the second actuator position, the contact element  40  is in second switch position. In particular, when the switch actuator  50  is in the second actuator position, the terminal end  41  of the contact element  40  abuts the inward-facing surface  55  of the guide plate  51  at a location that is between the toggle opening  88  and the guide plate rear end portion  56 ( 2 ), whereby the contact element  40  is at a second angle relative to the switch body  39 , and the electrical switch  38  is positioned in the second switch position, e.g., a closed switch position in which electrical current does not flow between the power supply  44  and the electric motor  22 . 
     Thus, the switch actuator  50  serves as a spring element, such that when the switch actuator  50  is in the first actuator position, the ramp portion  69  of the resilient arm  66  biases the lever portion  68  toward the wall edge  18  such that lever portion  68  engages the wall edge  18 , thereby preventing inadvertent movement of the switch actuator  50  to the second actuator position. In addition, when the switch actuator  50  is actuated by applying a bi-directional force to the platform  81 , the lever portion  68  is displaced from the wall edge  18 , thereby permitting movement of the switch actuator  50  to the second actuator position. 
     The user moves the switch actuator  50  from the second actuator position to the first actuator position by placing a fingertip on the first rounded portion  85 ( 1 ) of the lever portion  68  of the resilient arm  66  and applying a longitudinally rearward force (represented by arrow A 3 ). As a result of the applied longitudinally rearward force A 3 , the guide plate  51  is moved longitudinally toward the tool housing second end  4 . The longitudinal motion of the switch actuator  50  is limited by interaction between the guide plate rear end portion  56 ( 2 ) and the stop wall  9 , as well as interaction between the platform  81  and the second end portion  18 ( 2 ) of the wall edge  18  that defines the switch opening  16 . In addition, since the platform  81  is moved toward the tool housing second end  4 , the lever portion free end  83  is aligned with the switch opening  16 . In this position, the resilient properties of the switch actuator  50  return the lever portion  68  to its original radial offset position relative to the guide plate  51  in which the platform  81  protrudes into the switch opening  16  and the lever portion free end  83  is engaged with the wall edge recess  18 ( 5 ). 
     Selective illustrative embodiments of the power tool including the switch actuator are described above in some detail. It should be understood that only structures considered necessary for clarifying the power tool including the switch actuator have been described herein. Other conventional structures, and those of ancillary and auxiliary components of the power tool and the switch actuator, are assumed to be known and understood by those skilled in the art. Moreover, while a working example of the power tool including the switch actuator has been described above, the power tool and the switch actuator are not limited to the working example described above, but various design alterations may be carried out without departing from the power tool as set forth in the claims.