Patent Publication Number: US-9415488-B2

Title: Screwdriving tool having a driving tool with a removable contact trip assembly

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/982,711, filed Dec. 30, 2010, titled “Screwdriving Tool Having a Driving Tool with a Removable Contact Trip Assembly,” which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/293,122, filed Jan. 7, 2010. Each of the aforementioned applications is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to a screwdriving tool having a driving tool with a removable contact trip assembly. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     We have found that it is common in the building trades to assemble framework with cordless impact drivers and attach the drywall with corded screwguns. We envision a system that allows the user to get more versatility from an assembly tool, such as an impact driver. When the contact trip assembly is not attached to the driving tool, the driving tool performs in its typical manner. When the contact trip assembly is attached to the driving tool, the driving tool takes on the ability to drive drywall, sheathing and decking fasteners to an accurate and repeatable depth. 
     We have found that this approach provides a small and compact screwdriver. We have found that when the driving tool is an impact driver, the impact driver provides the desired speed for driving low torque screws fast and can also provide additional torque when needed. We have further found that the contact trip assembly, sensor, and on-board controller could eliminate the need for a mechanical clutch that is typical of systems that provide depth control. Eliminating the mechanical clutch could provide a much more compact system with minimal to no change in clutch performance due to wear or mechanical breakdown of mechanical clutch surfaces. 
     Another potential advantage associated with the elimination of a mechanical clutch concerns the capability to provide depth sensing without requiring the operator to exert and maintain a large axial force directed through the screwdriving tool onto the fastener. While each of the examples disclosed herein employs a biasing spring, we note that the spring is relatively light due to the fact that it is not associated with the mechanical operation of a clutch but rather the placement of a sensor or sensor target that is employed to electronically control the operation of the screwdriving tool. 
     Additionally, coupling such a contact trip assembly, sensor and controls with drill drivers and hammer drills could also provide accurate depth control when the contact trip assembly is attached to the driving tool and also not hinder or compromise the other functions or capabilities of such tools when the contact trip assembly is removed. We note, however, that we have also found that the contact trip assembly could be permanently mounted to the driving tool and that such assembly would be advantageous in some situations. 
     In one form, the present teachings provide a screwdriving tool that includes a driving tool, a contact trip assembly that is coupled to the driving tool, a sensor and a sensor target. The driving tool has a tool housing, a motor assembly and an output member that is driven by the motor assembly. The contact trip assembly has a nose element. One of the nose element and the output member is axially movable and biased by a spring into an extended position. One of the sensor and the sensor target is coupled to the tool housing, while the other one of the sensor and the sensor target is coupled to the one of the output member and the nose element for axial movement relative to the one of the sensor and the sensor target. The sensor provides a sensor signal that is based upon a distance between the sensor and the sensor target. The motor assembly is controllable in a first operational mode and at least one rotational direction based in part on the sensor signal. 
     In another form, the present teachings provide a screwdriving tool that includes a brushed DC motor, a motor direction switch and a direction sensing circuit. The motor direction switch is movable into first and second switch positions to alternate connection of the brushes of the DC motor to first and second terminals. The direction sensing circuit is configured to generate a first signal indicative the coupling of one of the brushes to the first terminal and a second signal indicative of the coupling of the one of the brushes to the second terminal. The first and second signals being generated when the brushed DC motor is operated for a time exceeding a predetermined amount of time. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is an exploded perspective view of a screwdriving tool constructed in accordance with the teachings of the present disclosure; 
         FIG. 2  is a perspective view of the screwdriving tool of  FIG. 1 ; 
         FIG. 2A  is an exploded perspective view of a portion of the screwdriving tool of  FIG. 1  illustrating the driving tool in more detail; 
         FIG. 2B  is a schematic illustration of a portion of the screwdriving tool of  FIG. 1  illustrating a portion of a motor control circuit; 
         FIG. 2C  is a schematic illustration of a portion of the screwdriving tool of  FIG. 1  illustrating a circuit for detecting the rotational direction of the motor assembly; 
         FIG. 3  is an exploded perspective view of a portion of the screwdriving tool of  FIG. 1 , illustrating the contact trip assembly in more detail; 
         FIGS. 4 and 5  are longitudinal section views of a portion of the screwdriving tool of  FIG. 1 ; 
         FIGS. 6 and 7  are lateral section views through the contact trip assembly illustrating the clip in its normal and deflected states; 
         FIG. 8  is an exploded perspective view of a second screwdriving tool constructed in accordance with the teachings of the present disclosure; 
         FIG. 9  is a perspective view of the screwdriving tool of  FIG. 8 ; 
         FIG. 10  is an exploded perspective view of a portion of the screwdriving tool of  FIG. 8  illustrating the contact trip assembly in more detail; 
         FIG. 11  is a perspective view of the contact trip assembly shown in  FIG. 10 ; 
         FIGS. 12 through 15  are perspective partly broken away or sectioned views of the contact trip assembly shown in  FIG. 10 ; 
         FIG. 16  is a longitudinal section view of a portion of the screwdriving tool of  FIG. 8 ; 
         FIG. 17  is a perspective view of a portion of the screwdriving tool of  FIG. 8 ; 
         FIGS. 18 and 19  are longitudinal section views of a third screwdriving tool constructed in accordance with the teachings of the present disclosure; 
         FIG. 20  depicts an alternate means for controlling a rotational direction of the motor of the screwdriving tool of any of the examples of the present disclosure; 
         FIG. 21  is a longitudinal section view of a portion of a fourth screwdriving tool constructed in accordance with the teachings of the present disclosure; 
         FIG. 22  is a view similar to that of  FIG. 21 , but illustrating the output member in a retracted position; 
         FIG. 23  is a longitudinal section view of a portion of a fifth screwdriving tool constructed in accordance with the teachings of the present disclosure; 
         FIG. 24  is a view similar to that of  FIG. 23 , but illustrating the output member in a retracted position; 
         FIG. 25  is a perspective view of a portion of a sixth screwdriving tool constructed in accordance with the teachings of the present disclosure; 
         FIG. 26  is a partially broken away perspective view of the screwdriving tool of  FIG. 25 ; 
         FIG. 27  is a perspective view of a portion of the screwdriving tool of  FIG. 25 , illustrating the driving tool in more detail; 
         FIG. 28  is an exploded perspective view of a portion of the screwdriving tool of  FIG. 25 , illustrating the contact trip assembly in more detail; 
         FIG. 29  is a longitudinal section view of a portion of the screwdriving tool of  FIG. 25 ; 
         FIG. 30  is a view similar to that of  FIG. 26 , but illustrating the sensor target in a rearward or retracted position; 
         FIG. 31  is a perspective view of a portion of a seventh screwdriving tool constructed in accordance with the teachings of the present disclosure; 
         FIG. 32  is a partially broken away perspective view of the screwdriving tool of  FIG. 31 ; 
         FIG. 33  is a perspective view of a portion of the screwdriving tool of  FIG. 31 , illustrating the driving tool in more detail; and 
         FIG. 34  is a longitudinal section view of a portion of the screwdriving tool of  FIG. 31 . 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1 and 2  of the drawings, an exemplary screwdriving tool constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral  10 . The screwdriving tool  10  can comprise a driving tool  12  and a contact trip assembly  14  that can be removably coupled to the driving tool  12 . 
     The driving tool  12  can be any type of power tool that is configured to provide a rotary output for driving a threaded fastener, such as a drill/driver, a hammer-drill/driver, an impact driver or a hybrid impact driver. Except as noted herein, the driving tool  12  may be conventionally constructed (e.g., where the driving tool  12  is a drill/driver, the driving tool  12  may be generally similar to the drill/drivers disclosed in U.S. Pat. No. 7,537,064, which is hereby incorporated by reference, and/or a model DCD920 drill/driver that is commercially available from the DeWalt Industrial Tool Company of Towson, Md.; where the driving tool  12  is a hammer-drill/driver, the driving tool may be generally similar to the hammer-drill/drivers disclosed in U.S. Pat. No. 7,314,097, which is hereby incorporated by reference, and/or a model DCD950 hammer-drill/driver that is commercially available from the DeWalt Industrial Tool Company of Towson, Md.; where the driving tool  12  is an impact driver, the driving tool  12  may be generally similar to a model DC826 impact driver that is commercially available from the DeWalt Industrial Tool Company of Towson, Md.; and where driving tool  12  is a hybrid impact driver, the driving tool may be generally similar to the driving tools disclosed in U.S. patent application Ser. No. 12/566,046, all of which are hereby incorporated by reference). 
     With reference to  FIG. 2A , the driving tool  12  in the particular example provided is generally similar to a model DC825KA impact driver, which is commercially available from the DeWalt Industrial Tool Company of Towson, Md., in that it includes a clam shell housing  20 , a motor assembly  22 , a transmission  24 , an impact mechanism  26 , an output spindle  28  and a chuck  30 . The motor assembly  22  can comprise any type of motor, such as an AC motor, a DC motor, or a pneumatic motor. In the particular example provided, the motor assembly  22  includes a brushed DC electric motor  32  that is selectively coupled to a battery pack  36  via a trigger assembly  38 . Additionally, the driving tool  12  comprises a gear case  40 , a sensor  42  and a controller  44 . 
     With reference to  FIGS. 1 and 2A , the gear case  40  can be unitarily formed from an appropriate material, such as aluminum, magnesium or a reinforced plastic, and can be coupled to the clam shell housing  20  so as to cover or shroud the transmission  24  and the impact mechanism  26 . The gear case  40  can be a container-like structure that can include front end  50  that defines a mounting stem  52 , a first attachment member  54  and a sensor mount  56 . The mounting stem  52  can comprise a hollow stem structure  58  through which the output spindle  28  can extend. In the example provided, the stem structure  58  includes a generally cylindrical portion, but it will be appreciated that the stem structure  58  could be formed with one or more portions having a non-circular cross-sectional shape that can aid in inhibiting rotation of the contact trip assembly  14  relative to the driving tool  12 . The first attachment member  54  can comprise any means for retaining the contact trip assembly  14  to the driving tool  12 , including without limitation a thread form or a locking tab. In the example provided, the first attachment member  54  comprises a portion of the stem structure  58  into which an annular, circumferentially extending groove  60  is formed. The sensor mount  56  can comprise a structure that can be assembled to or integrally formed with the gear case  40  that is configured to hold or secure the sensor  42 . While the sensor mount  56  can be configured to permit physical access to the sensor  42  through the gear case  40 , or could be configured to shroud the sensor  42  such that the sensor  42  is not accessible from the exterior of the driving tool  12 . The sensor mount  56  can be shaped or configured to cooperate with the contact trip assembly  14  to resist or inhibit rotation of the contact trip assembly  14  relative to the stem structure  58 . 
     The sensor  42  can be any type of sensor that can be employed to detect the physical presence of the contact trip assembly  14 . Suitable sensors include without limitation Hall effect sensors, eddy current sensors, magnetoresistive sensors, limit switches, proximity switches, and optical sensors. In the particular example provided, the sensor  42  comprises a Hall effect sensor that is configured to generate a sensor signal that is responsive to the sensing of a magnetic field of a predetermined field strength. 
     The controller  44  can be electrically coupled to (or integrated into) the trigger assembly  38  and can be configured to cooperate with the trigger assembly  38  to control the operation of the motor assembly  22  as will be described in more detail below. 
     With reference to  FIGS. 3 and 4 , the contact trip assembly  14  can comprise a contact trip housing  70 , a nose element  72 , a sensor structure  74 , a first biasing spring  76 , a spring retainer  78 , a retaining mechanism  80  and means  82  for adjusting a position of the nose element  72  relative to the sensor structure  74 . 
     The contact trip housing  70  can be defined by a wall member that can form a mount  90 , a barrel  92  and a shoulder  94  that is disposed between the mount  90  and the barrel  92 . The mount  90  can define a mount cavity  98  and can be configured to engage the front end of the gear case  40  in a desired manner. For example, the mount  90  can be configured to be received over and engage the mounting stem  52  ( FIG. 1 ) as well as the sensor mount  56  ( FIG. 1 ) such that the contact trip housing  70  is oriented to the driving tool  12  in a predetermined orientation. The barrel  92  can extend forwardly of the shoulder  94  and can define a barrel aperture  100  that can extend through the shoulder  94  and intersect the mount cavity  98 . 
     The nose element  72  can be a generally tubular structure having a plurality of first threads  110  formed on a proximal or first end, and an abutting face  112  formed on a distal or second end. One or more sight windows  114  formed through nose element  72  proximate the second end. The nose element  72  can be received into the barrel aperture  100  and can include a geometric feature, such as ribs or grooves (not specifically shown) that can matingly engage grooves or ribs (not specifically shown) that extend from the barrel  92  into the barrel aperture  100 . It will be appreciated from this disclosure that mating engagement of the geometric features (e.g., grooves —) in/on the nose element  72  with mating geometric features (e.g., ribs —) in/on the barrel  92  can inhibit rotation of the nose element  72  relative to the barrel  92 . 
     The sensor structure  74  can include a sensor body  120  and a sensor arm  122 . The sensor body  120  can comprise a first annular portion  130  and a second annular portion  132 . The first annular portion  130  can define a first abutting face  134  and can be received in the barrel aperture  100  such that it extends into or through the shoulder  94 . The second annular portion  132  can be somewhat larger in diameter than the first annular portion  130  and can be received in the mount cavity  98 . The second annular portion  132  can define a second abutting face  136  that can be disposed on a side of the sensor body  120  opposite the first abutting face  134 . The sensor arm  122  can comprise an arm member  140 , which can be fixedly coupled to the sensor body  120 , and a sensor target  142  that can be coupled to the arm member  140  on a side opposite the sensor body  120 . The sensor target  142  can be configured such that it may be sensed or operate the sensor  42  in the driving tool  12  (as will be explained in more detail, below), but in the example provided, the sensor target  142  comprises a magnet. 
     The first biasing spring  76  can be received in the mount cavity  98  and can be abut the second abutting face  136 . The spring retainer  78  can be a washer-like structure or a spring clip that can be received in the mount cavity  98  and coupled to the contact trip housing  70  so as to compress the first biasing spring  76  against the sensor body  120  such that the first biasing spring  76  biases the second annular portion  132  against the shoulder  94 . 
     With reference to  FIGS. 3, 4 and 6 , the retaining mechanism  80  can be configured to cooperate with the first attachment member  54  on the driving tool  12  to retain the contact trip assembly  14  to the driving tool  12 . In the example provided, the retaining mechanism  80  comprises a pair of retaining clips  150 , a second biasing spring  152  (shown in  FIG. 6 ), a first release button  154  and a second release button  156 . Each of the retaining clips  150  can have a semi-circular clip body  160 , which is configured to be received in the circumferentially extending groove  60  in the gear case  40 , and a pair of clip tabs  162  that are coupled to the opposite ends of the clip body  160 . The retaining clips  150  can be received through clip apertures  166  formed in the mount  90  of the contact trip housing  70  such that the clip bodies  160  are received within the mount cavity  98  and the clip tabs  162  extend outwardly from the clip apertures  166 . The second biasing spring  152  can be a spring, such as a compression spring, that can be received in a spring pocket  170  (shown in  FIG. 6 ) formed in contact trip housing  70  and compressed between the contact trip housing  70  and one of the clip bodies  160  to bias the clip body  160  toward the other clip body  160 . The first and second release buttons  154  and  156  can be coupled to opposite pairs of the clip tabs  162 . The first and second release buttons  154  and  156  can be configured with a generally V-shaped cam  180  (shown in detail only on the first release button  154  in  FIG. 6 ) that can abut follower surfaces  184  formed on the clip tabs  162 . Movement of the V-shaped cams  180  of the first and second release buttons  154  and  156  in a radially inwardly direction as shown in  FIG. 7  spreads the follower surfaces  184  apart from one another. It will be appreciated that the spreading of the follower surfaces  184  apart from one another causes a corresponding spreading apart of the clip bodies  160  such that the clip bodies  160  can be received over the stem structure  58  ( FIG. 4 ). When the first and second release buttons  154  and  156  are released, the second biasing spring  152  will urge the retaining clips  150  toward one another such that the clip bodies  160  can be at least partially received in the circumferentially extending groove  60  in the contact trip housing  70  as shown in  FIG. 6  to thereby retain the contact trip assembly  14  to the driving tool  12 . 
     Returning to  FIGS. 3 and 4 , the means  82  for adjusting the position of the nose element  72  relative to the sensor structure  74  can comprise a first rotary adjustment member  200 , a second rotary adjustment member  202 , a mounting block  204 , a retainer  206 , a detent spring  208 , an adjustment collar  210 , and a retaining clip  212  (shown in  FIG. 4 ). 
     The first rotary adjustment member  200  can be an annular structure having an end face  220 , a plurality of second threads  222  and a plurality of longitudinally extending teeth  224 . The end face  220  can be abutted against the first abutting face  134  of the sensor body  120 . The second threads  222  can be threadably engaged to the first threads  110  formed on the proximal end of the nose element  72 . While the first and second threads  110  and  222  are depicted in the example provided as being external and internal threads, respectively, it will be appreciated that in the alternative, the first threads  110  could be internal threads and the second threads  222  could be external threads. The longitudinally extending teeth  224  can be spaced about the circumference of the first rotary adjustment member  200  and can extend generally parallel to an axis  230  that is coincident with a longitudinal axis of the nose element  72  and a rotational axis of the output spindle  28  of the driving tool  12 . A portion of the longitudinally extending teeth  224  can be visible through an engagement aperture  232  formed through the barrel  92 . 
     The mounting block  204  can be co-formed with the contact trip housing  70  and can comprise a first annular support surface  250  that can be disposed in a plane (not specifically shown) that intersects the axis  230  at an acute included angle  252 . In the particular example provided, the acute included angle  252  has a magnitude of about 45 degrees, but it will be appreciated that the magnitude of the acute included angle  252  can be larger or smaller than that which is depicted here. 
     The second rotary adjustment member  202  can comprise an annular body having a rear abutting face  260 , a beveled side wall  262 , a plurality of internal teeth  264  and a plurality of external teeth  266 . The rear abutting face  260  can be configured to abut the first annular support surface  250  formed on the mounting block  204  such that the second rotary adjustment member  202  is disposed at the acute included angle  252 . The plurality of internal teeth  264  can be received into the engagement aperture  232  and can be meshingly engaged with the longitudinally extending teeth  224  of the first rotary adjustment member  200  in a manner that permits the first rotary adjustment member  200  to reciprocate along the axis  230  while maintaining meshing engagement between the internal teeth  264  and the longitudinally extending teeth  224 . The external teeth  266  can have a configuration that is similar to a bevel gear and can extend from the annular body on a side opposite the rear abutting face  260 . The crests of the external teeth  266  can cooperate to define a front abutting face  112 . 
     The retainer  206  can be a generally U-shaped component that can comprise a second annular support surface  270 , an annular interior surface  272  and an annular exterior surface  274 . The second annular support surface  270  can be configured to abut the crests of the external teeth  266  of the second rotary adjustment member  202 . The annular interior surface  272  can be configured to abut the exterior surface of the barrel  92 . The annular interior surface  272  and the barrel  92  can be configured so as to resist rotation of the retainer  206  relative to the contact trip housing  70 . In the particular example provided, the annular interior surface  272  defines a key member  280  that can be received in a recess (not specifically shown) in the exterior surface of the barrel  92  to inhibit rotation of the retainer  206  relative to the barrel  92 . 
     The adjustment collar  210  can be an annular shell-like structure that can be received over the mounting block  204 , the second rotary adjustment member  202  and a portion of the barrel  92  and can comprise a plurality of adjustment teeth  290 , a first annular wall member  292 , a second annular wall member  294  and a plurality of detent teeth  296 . The first annular wall member  292  can abut the exterior surface of the barrel  92  such that the barrel  92  can support the adjustment collar  210  for rotation about the axis  230 . The second annular wall member  294  can be disposed concentric with the first annular wall member  292  and can abut a portion of the beveled side wall  262  of the second rotary adjustment member  202 . The plurality of adjustment teeth  290  can be configured to meshingly engage a portion of the external teeth  266  formed on the second rotary adjustment member  202  at a location proximate a forward end of the mounting block  204 . Due to the sloped orientation of the second rotary adjustment member  202 , the location at which the adjustment teeth  290  meshingly engage the external teeth  266  is disposed approximately 180 degrees away from a location at which the internal teeth  264  of the second rotary adjustment member  202  meshingly engage the longitudinally extending teeth  224  of the first rotary adjustment member  200 . The annular exterior surface  274  of the retainer  206  can abut an interior circumferential surface of the adjustment collar  210  (e.g., the second annular wall member  294 ). The retaining clip  212  ( FIG. 4 ) can be received into a circumferentially extending groove  300  formed in the barrel  92  and can limit forward movement of the adjustment collar  210  on the barrel  92  to thereby couple the adjustment collar  210  to the contact trip housing  70  in a manner that permits relative rotation but inhibits relative axial movement therebetween. 
     The detent spring  208  can be a leaf spring that can comprise opposed detent tabs that can be engaged to the first rotary adjustment member  200  and the adjustment collar  210  to resist relative rotation therebetween. In the particular example provided, the detent spring  208  is generally V-shaped, having a center detent tab  310  and a pair of distal detent tabs  312 . The center detent tab  310  can be disposed at the vertex of the V-shaped leaf spring and can be configured to engage the adjustment teeth  290  on the adjustment collar  210 . The distal detent tabs  312  can be disposed at the opposite ends of the V-shaped leaf spring and can be received through a detent spring aperture  320  formed in the contact trip housing  70 . The distal detent tabs  312  can be configured to engage the longitudinally extending teeth  224  formed on the first rotary adjustment member  200 . Rotation of the adjustment collar  210  by a user (to adjust a depth setting of the contact trip assembly  14 ) can cause the adjustment teeth  290  to urge the center detent tab  310  in a radially inward direction, which can deflect the distal detent tabs  312  radially outwardly away from the first rotary adjustment member  200  so as to disengage the longitudinally extending teeth  224  and permit rotation of the first rotary adjustment member  200  relative to the contact trip housing  70 . Alignment of the center detent tab  310  to a valley (not specifically shown) between adjacent adjustment teeth  290  permits the distal detent tabs  312  to deflect radially inwardly toward the first rotary adjustment member  200  so as to engage the longitudinally extending teeth  224  and resist rotation of the first rotary adjustment member  200  relative to the contact trip housing  70 . 
     With reference to  FIGS. 1 and 2A , a driving bit  400 , such as a Phillips, Phillips ACR, Torx, Scrulox, Hex, Pozidriv, or Pozidriv ACR bit, can be coupled to the output spindle  28  of the driving tool  12 . In the particular example provided, the driving bit  400  is coupled to a magnetic bit holder  402  that is secured to the output spindle  28  via the chuck  30 . It will be appreciated, however, that the driving bit  400  could be configured with an extended length that permits the driving bit  400  to be directly coupled to the output spindle  28  without the use of a separate bit holder. 
     The contact trip assembly  14  can be received over the stem structure  58  such that the driving bit  400  is received through the contact trip housing  70  and into the nose element  72 . The contact trip housing  70  can be mounted to the mounting stem  52  as described in detail above. Briefly, the first and second release buttons  154  and  156  can be urged radially inwardly to move the retaining clips  150  ( FIG. 3 ) outwardly, the mount  90  of the contact trip housing  70  can be received over the stem structure  58  such that the retaining clips  150  ( FIG. 3 ) are aligned to the groove  60 , and the first and second release buttons  154  and  156  can be released to permit the second biasing spring  152  ( FIG. 6 ) to urge the retaining clips  150  ( FIG. 3 ) at least partly into the groove  60  to thereby fix the contact trip housing  70  to the gear case  40  in an axial direction. As also noted above, the mount  90  of the contact trip housing  70  can be configured to engage the gear case  40  such that the contact trip housing  70  is disposed and maintained relative to the gear case  40  in a predetermined orientation. 
     With reference to  FIG. 4 , the driving bit  400  can be engaged to the head (not shown) of a threaded fastener (not shown) that is to be installed (driven) into a desired surface (not shown) of a workpiece (not shown). The abutting face  112  of the nose element  72  can be (initially) spaced apart from the desired surface of the workpiece. The driving tool  12  can be operated (i.e., via the trigger assembly  38  ( FIG. 2A )) to rotate the driving bit  400  to turn the threaded fastener such that the threaded fastener is threaded into the workpiece. It will be appreciated that the abutting face  112  of the nose element  72  will approach and contact that the surface of the workpiece as the threaded fastener is threaded into the workpiece and that continued rotation of the driving bit  400  after contact is established between the abutting face  112  and the surface of the workpiece, the nose element  72  will be driven axially into the barrel  92  in the direction of arrows A in  FIG. 5 . Movement of the nose element  72  in this manner will cause corresponding axial movement of the first rotary adjustment member  200  toward the gear case  40 ; it will be appreciated, however, that the longitudinally extending teeth  224  on the first rotary adjustment member  200  will remain in meshing engagement with the internal teeth  264  ( FIG. 3 ) of the second rotary adjustment member  202  despite the axial movement of the first rotary adjustment member  200  relative to the second rotary adjustment member  202  as described above. Such movement of the first rotary adjustment member  200  will correspondingly cause rearward axial movement of the sensor structure  74  (against the bias of the first biasing spring  76 ) such that a distance D between the sensor target  142  and the sensor  42  decreases. When the distance between the sensor target  142  and the sensor  42  decreases to a predetermined point that causes the sensor  42  to generate the sensor signal (i.e., when the threaded fastener has been driven to a depth to which the contact trip assembly  14  has been preset), the controller  44  ( FIG. 2A ) is configured to interrupt the operation of the motor assembly  22  ( FIG. 2A ) to halt the rotation of the driving bit  400 . 
     It will be appreciated that in some instances, it may be beneficial to permit the driving tool  12  to be operated in one or more rotational directions despite the positioning of the sensor target  142  at a distance that is less than or equal to the predetermined distance that is employed to cause the sensor  42  to generate the sensor signal. Accordingly, the driving tool  12  could include a mode switch that can be employed by the operator of the screwdriving tool  10  to cause the driving tool  12  to rotate in one or more rotational directions regardless of the position of the sensor target  142  relative to the sensor  42 . 
     A relatively common situation may simply involve instances where the operator of the screwdriving tool  10  wishes to loosen a fastener that has been driven to the desired depth. In such situations, the driving tool  12  may be equipped with a direction sensor (not shown) that can be configured to sense a position of a motor direction switch  500  ( FIG. 2A ) and generate a direction signal in response thereto. The controller  44  ( FIG. 2A ) can receive the direction signal and can permit operation of the motor assembly  22  ( FIG. 2A ) in instances where the sensor signal is generated by the sensor  42  but the direction signal generated by the direction sensor is indicative of the placement of the direction switch  500  ( FIG. 2A ) in a predetermined position (e.g., a position that corresponds to operation of the motor assembly  22  ( FIG. 2A ) in a reverse direction). 
     It is relatively common for modern driving tools with brushed electric motors to control the operation of the motor through a pulse width modulated (PWM) signal that operates one or more field effect transistors as is shown in  FIG. 2B . In the example provided, the controller  44 , which may include a  555  timer or a microprocessor, for example, can provide the PWM signal to the field effect transistor(s)  510  that can be based entirely on a position of a trigger  512  ( FIG. 1 ) (i.e., the PWM signal can be determined independently and irrespective of the setting of the motor direction switch  500 ). In such tools, it is relatively common for the motor direction switch  500  to control the rotation of the motor  32  by controlling the electrical connection of the brushes M+ and M− of the motor  32 , a first terminal  520  that is associated with a positive supply voltage and a second terminal  522  that is coupled to the drain DR of the field effect transistor(s)  510 . Stated another way, the electrical coupling of the brush M+ to the first terminal  520  and the brush M− to the second terminal  522  will cause the motor  32  to rotate in a first rotational direction, while the electrical coupling of the brush M+ to the second terminal  522  and the brush M− to the first terminal  520  will cause the motor  32  to rotate in a second, opposite rotational direction. 
     In instances where it is desirable to know the direction in which the motor  32  is to be operated (e.g., where depth sensing is employed and/or where the diving tool includes an electronically-controlled torque clutch) so that the operation of the motor  32  may be inhibited in some situations (e.g., upon sensing that a fastener has been installed to a preset depth or to a desired torque when the motor  32  is rotating in the first rotational direction) but permitted in other situations (e.g., the sensing that a fastener has been installed to a preset depth or to a desired torque when the motor  32  is rotating in the second rotational direction), the controller  44  may include a circuit that senses the setting of the motor direction switch  500  by monitoring the voltage at one of the brushes (e.g., the brush M+), such as the exemplary circuit  550  that is depicted in  FIG. 2C . The circuit  550  can comprise a diode D 1 , a first resistor R 1 , a second resistor R 2 , a third resistor R 3 , a first capacitor C 1  and a second capacitor C 2 . The diode D 1  and the first resistor R 1  can be coupled in series between the brush M+ and a node A, with the first resistor R 1  being disposed between the diode D 1  and the node A. The second resistor R 2  can be coupled in series between the node A and control voltage source Vcc. The third resistor R 3  can be coupled in series between the node A and an output terminal  560  of the circuit  550 . The second capacitor C 2  can be coupled between the output terminal  560  of the circuit  550  (at a point between the third resistor R 3  and the output terminal  560 ) and an electric ground GND. The first capacitor C 1  can be coupled to the node A and the grounded side of the second capacitor C 2 . 
     When the motor direction switch  500  couples the brush M+ to a positive voltage (so that the motor  32  operates in the first direction), the diode D 1  does not conduct electricity between the brush M+ and the output terminal  560  and consequently, the voltage at the output terminal  560  corresponds to the voltage of the control voltage source Vcc. 
     With additional reference to  FIG. 2B , when the motor direction switch  500  couples the brush M+ to the drain D of the field effect transistor(s)  510 , the voltage at the brush M+ will depend upon the state of the field effect transistor(s)  510 , while the filtered voltage at the output terminal  560  will be near ground. When the field effect transistor(s) are “on”, the diode D 1  will conduct electricity (to thereby permit current to flow from the control voltage source Vcc to an electrical ground through the control FET) such that the voltage at node A will drop to a voltage that is approximately equal to Vf (assuming that the magnitude of the first resistor R 1  is much less than the magnitude of the second resistor R 2 ). When the field effect transistor(s) are “off”, the diode D 1  will cease conducting electricity, which causes the voltage at node A to raise to the voltage of the control voltage source Vcc. The first and second resistors R 1  and R 2  and the first capacitor C 1  can control the speed at which the voltage at the node A changes in this mode. Assuming the use of a PWM signal with a frequency of about 8 kHz (such that one PWM cycle has a duration of 125 us; with a 10% duty cycle, the length of time the cathode of diode D 1  will be pulled low is 12.5 us) and that the duty cycle of the PWM signal can be as low as 10%, the first capacitor C 1  can have a value of 100 nF (so as to discharge relatively quickly when the cathode of the diode D 1  is pulled to a low electrical state), the first resistor R 1  can have a value of 22 ohms (which provides a time constant of 2.2 us, which is much less than the 12.5 us that the diode D 1  is conducting so that the first capacitor C 1  will be permitted to discharge completely) and the second resistor R 2  can have a value of 100 k ohms (which provides a time constant of 10 ms, which is much longer than the 112 us that the field effect transistor(s)  510  will be off so that node A will never be permitted to recharge before the next PWM pulse discharges the first capacitor C 1 ). The third resistor R 3  and the second capacitor C 2  can form a secondary low-pass filter to further smooth-out the voltage at the output terminal  560 . 
     It will be appreciated that the voltage at the output terminal  560  can be employed to directly control a field effect transistor (not shown) or be read by a microprocessor or other type of controller to determine the state of the motor direction switch  500 . 
     We note that the field effect transistor(s)  510  must be “on” for a certain amount of time to be able to sense the setting or position of the motor direction switch  500 . In this regard, the setting cannot be sensed by the circuit  550  unless some current flows through the motor  32 . Also, since the third resistor R 3  and the first capacitor have a time constant (approximately 10 ms in the example provided), the voltage at the output terminal  560  may not accurately represent the state or position of the motor direction switch  500  for a predetermined length of time, such as approximately 20 ms. We suggest that immediately after the trigger  512  ( FIG. 1 ) is depressed to operate the motor  32 , the controller  44  be configured to output a low duty cycle signal to the motor  32  for a predetermined length of time (e.g., 20 ms) which is too low to cause the motor  32  to rotate but high enough to permit the circuit  550  to properly function. The predetermined length of time is relatively short and would not be perceived by the operator of the driving tool  12  ( FIG. 1 ). Moreover, the trigger assembly  38  ( FIG. 2A ) can be configured to prevent the switching of the motor direction switch  500  once the trigger  512  ( FIG. 1 ) has been depressed so that voltage at the output terminal  560  will remain valid and accurate until the trigger  512  ( FIG. 1 ) is released. 
     Another solution is depicted in  FIG. 20  wherein the direction switch  500  is configured to provide the controller  44 ′ with a digital signal indicative of the desired rotational direction of the motor  32 . Based on the digital signal received from the direction switch  500 , the controller  44 ′ can control the rotational direction of the motor  32  by switching the field effect transistors in an appropriate H-bridge configuration. 
     With reference to  FIGS. 8 and 9 , a second screwdriving tool constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral  10   a . The screwdriving tool  10   a  can comprise the driving tool  12  and a contact trip assembly  14   a  that can be removably coupled to the driving tool  12 . Except as detailed herein, the contact trip assembly  14   a  can be generally similar to the contact trip assembly  14  ( FIG. 1 ). 
     With reference to  FIGS. 8, 10 and 11 , the barrel  92   a  of the contact trip housing  70   a  is shown to be disposed about an axis  600  that is offset from a rotational axis  602  of the output spindle  28  ( FIG. 8 ) of the driving tool  12 , while the barrel aperture  100   a  is disposed about an axis (not specifically shown) that is coincident with the rotational axis  602  of the output spindle  28  ( FIG. 8 ). 
     With reference to  FIGS. 10 and 14 , the first rotary adjustment member  200   a  can be co-formed with the nose element  72   a . More specifically, the longitudinally extending teeth  224   a  can be formed on or non-rotatably coupled to the nose element  72   a  between the abutting face  112   a  and the plurality of first threads  110 . The second threads  222   a  can be formed in the sensor body  120   a  such that the nose element  72   a  is threadably engaged directly to the sensor structure  74   a . The first annular portion  130   a  of the sensor body  120   a  can extend through the barrel  92   a  and can include an aperture  620  through which a portion of the second rotary adjustment member  202   a  may be received. The second rotary adjustment member  202   a  can comprise a pinion  630  that can be mounted on an axle  632  that is offset from the rotational axis of the output spindle  28  ( FIG. 8 ). In the example provided, the axle  632  is mounted in an axle aperture  640  formed in the barrel  92   a  of the contact trip housing  70   a . The second rotary adjustment member  202   a  can include straight teeth  264   a  that can be meshingly engaged with the longitudinally extending teeth  224   a  associated with the first rotary adjustment member  200   a , as well as with the adjustment teeth  290   a  that are formed on the adjustment collar  210   a . It will be appreciated that rotation of the adjustment collar  210   a  can cause corresponding rotation of the pinion  630 , which can cause corresponding rotation of the first rotary adjustment member  200   a /nose element  72   a  to thread the nose element  72   a  further into or out of the sensor body  120   a . Stated another way, the adjustment teeth  290   a  can comprise a ring gear, the straight teeth  264   a  can comprise a planet gear, and the longitudinally extending teeth  224   a  can comprise a sun gear. It will also be appreciated that the sensor structure  74   a  can be non-rotatably but axially movably coupled to the contact trip housing  70   a  in any desired manner. In the particular example provided, longitudinally extending keyways  670 , which are illustrated in  FIGS. 12 and 13 , are formed into the first annular portion  130   a  of the sensor body  120   a  and key members (not specifically shown), which are integrally formed with the barrel  92   a  are received into the keyways  670  to permit the sensor body  120   a  to translate axially within the contact trip housing  70   a  while inhibiting rotation between the sensor body  120   a  and the contact trip housing  70   a.    
     With reference to  FIGS. 18 and 19 , a third screwdriving tool constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral  10   b . The screwdriving tool  10   b  can comprise a driving tool  12   b  and a contact trip assembly  14   b  that can be removably coupled to the driving tool  12   b . Except as detailed herein, the driving tool  12   b  and the contact trip assembly  14   b  can be generally similar to the driving tool  12  and the contact trip assembly  14  of  FIG. 1 . 
     The driving tool  12   b  differs from the driving tool  12  ( FIG. 1 ) in that the sensor  42   b  comprises a limit switch  700 , a lever  702  and a lever return spring  704 . The limit switch  700  can be any type of switch (e.g., a microswitch that may be toggled between a first state and a second state) and can be mounted to the gear case  40   b . The lever  702  can be pivotally coupled to the gear case  40   b . The lever return spring  704  can be received in a cavity  710  formed in the gear case  40   b  and can bias the lever  702  into engagement with the limit switch  700  such that the limit switch  700  is maintained in a first switch state. 
     The contact trip assembly  14   b  is identical to the contact trip assembly  14  ( FIG. 1 ), except that the sensor target  142   b  need not be magnetic. In this regard, the sensor target  142   b  comprises an end face of the sensor arm  122   b  and is configured to physically contact and pivot the lever  702  to permit the limit switch  700  to change from the first switch state to a second switch state (and generate the sensor signal). 
     Another screwdriving tool is generally indicated by reference numeral  10   c  in  FIG. 21 . In this example, portions of the contact trip assembly  14   c  are integrated into the driving tool  12   c . More specifically, the contact trip assembly  14   c  can include a sensor  1000 , a sensor target  1002 , and a nose element  72   c  that can be integrally formed with the gear case  40   c  of the driving tool  12   c . The sensor  1000  can be fixedly mounted to the gear case  40   c  and electrically coupled to the controller  44   c . The sensor  1000  can comprise any type of sensor, such as a microswitch or a non-contact switch, such as a Hall-effect switch or magnetoresistive switch. The sensor target  1002  can comprise a structure that is configured to cooperate with the sensor  1000  to generate an appropriate sensor signal as will be described in more detail, below. In the particular example provided, the sensor  1000  is a linear Hall-effect sensor and the sensor target  1002  is a magnet that is mounted to a mounting ring  1004  that is mounted coaxially about the output spindle  28   c . A spring  1006 , which can extend between a thrust washer  1008  adjacent to the gear case  40   c  the mounting ring  1004 , can bias the sensor target  1002  axially away from the sensor  1000 . A retaining ring  1010  can be employed to limit movement of the mounting ring  1004  relative to the output spindle  28   c.    
     The sensor  1000  can produce different signals depending on the location of the sensor target  1002 . In the particular example provided, the sensor  1000  acts as a toggle switch to toggle between two states (e.g., off and on) depending on the position of the sensor target  1002  (relative to the sensor  1000 ). For example, when the sensor target  1002  is spaced apart from the sensor  1000  by a distance that is greater than or equal to a predetermined distance, the sensor  1000  can produce a first signal, and when the sensor target  1002  is spaced apart from the sensor  1000  by a distance that is less than the predetermined distance, the sensor can produce a second signal. The controller  44   c  can receive the first and second signals and can operate the motor assembly  22   c  according to a desired schedule. In the example illustrated, the controller  44   c  permits operation of the motor assembly  22   c  in a forward or driving direction only when the second signal is produced, and inhibits operation of the motor assembly  22   c  in a forward direction when the first signal is produced. 
     To operate the screwdriving tool  10   c , a tool bit (not shown) can be coupled to the output spindle  28   c  in a conventional manner, a fastener (not shown) can be engaged to the tool bit. The user of the screwdriving tool  10   c  can exert a force can through the screwdriving tool  10   c , the tool bit, and the fastener onto a workpiece (not shown) such that the output spindle  28   c  is driven rearwardly as shown in  FIG. 22 . The force should be of sufficient magnitude to overcome the biasing force of the spring  1006  to thereby drive the sensor target  1002  rearwardly toward the sensor  1000  to cause the sensor  1000  to produce the second signal so that the motor assembly  22   c  will operate. Continued rotation of the fastener into the workpiece after contact has occurred between the workpiece and the abutting face  112   c  of the nose element  72   c  permits the spring  1006  to move the sensor target  1002  away from the sensor  1000 . When the sensor target  1002  is spaced apart from the sensor  1000  by a distance that is greater than or equal to the predetermined distance, the sensor  1000  can produce the first signal and the controller  44   c  can responsively halt the operation of the motor assembly  22   c  to thereby limit the depth to which the fastener is installed to the workpiece. While the sensor  1000  has been described as being fixedly coupled to the gear case  40   c , those of skill in the art will appreciate that the sensor  1000  can be adjustably coupled to the gear case  40   c  for axial movement over a predetermined range (e.g., via a screw or detent mechanism) to permit the user to adjust the point at which the sensor  1000  transitions from the second signal to the first signal. 
     Another screwdriving tool constructed in accordance with the teachings of the present disclosure is illustrated in  FIGS. 23 and 24  and is generally indicated by reference numeral  10   d . The screwdriving tool  10   d  is generally similar to the screwdriving tool  10   a  of  FIG. 21 , except that the output spindle  28   d  is axially movably coupled to an output member  1100  of the transmission  24   d , the spring  1006   d  is disposed between the output member  1100  and the output spindle  28   d , and the sensor target  1002   d  is fixedly mounted on the output spindle  28   d . It will be appreciated that a force applied by the user of the screwdriving tool  10   d  can urge the output spindle  28   d  rearwardly against the bias of the spring  1006   d  to position the sensor target  1002   d  at a location where the sensor  1000   d  can produce the second signal. Continued rotation of a fastener into the workpiece after contact has occurred between the workpiece and the abutting face  112   d  of the nose element  72   d  permits the spring  1006   d  to move the sensor target  1002   d  away from the sensor  1000   d . When the sensor target  1002   d  is spaced apart from the sensor  1000   d  by a distance that is greater than or equal to the predetermined distance, the sensor  1000   d  can produce the first signal and the controller  44   a  can responsively halt the operation of the motor assembly  22   a  to thereby limit the depth to which the fastener is installed to the workpiece. 
     While the retaining mechanism  80  and the first attachment member  54  have been depicted as including a pair of retaining clips  150  and a groove  60 , respectively, those of skill in the art will appreciate that various other coupling means can be employed in the alternative to releasably couple the contact trip assembly  14  to the driving tool  12 . For example, the screwdriving tool  10   e  can include a bayonet-style coupling means for releasably coupling the contact trip assembly  14   e  to the driving tool  12   e  as is depicted in  FIGS. 25 through 30 . 
     In this example, a first mount structure  1200  having a plurality of first lugs  1202  and a plurality of first grooves  1204  is coupled to the gear case  40   e , while a second mount structure  1210 , which is rotatably coupled to the contact trip housing  70   e , has have a plurality of second lugs  1212  and a plurality of second grooves  1214 . To install the contact trip assembly  14   e  to the driving tool  12   e , the second lugs  1212  and second grooves  1214  are aligned to the first grooves  1204  and the first lugs  1202 , respectively, the second mount structure  1210  of the contact trip assembly  14   e  is pushed axially over the first mount structure  1200  of the driving tool  12   e  to position the second mount structure  1210  in a void space VS between the gear case  40   e  and the first mount structure  1200 , and the second mount structure  1210  is rotated to position the second lugs  1212  axially in-line with the first lugs  1202  to prevent the contact trip assembly  14   e  from being axially withdrawn from the driving tool  12   e . It will be appreciated that the entire contact trip assembly  14   e  can be rotated relative to the driving tool  12   e  to secure the second mount structure  1210  to the first mount structure  1200 , but in the particular example provided, the second mount structure  1210  is fixedly and rotatably coupled to a securing collar  1220  that is rotatably mounted on the contact trip housing  70   e.    
     A detent mechanism  1230  can be employed to inhibit undesired rotation of the contact trip assembly  14   e  relative to the driving tool  12   e . In the example provided, the detent mechanism  1230  comprises a spring-biased detent pin  1232  that is axially slidably mounted in the contact trip housing  70   e , and first and second recesses  1234  and  1236 , respectively. Rotation of the second mount structure  1210  relative to the contact trip housing  70   e  can align the detent pin  1232  with the first recess  1234  or the second recess  1236 . Engagement of the detent pin  1232  to the first recess  1234  positions the second mount structure  1210  relative to the contact trip housing  70   e  so that the second lugs  1212  will be aligned to the first grooves  1204  when the contact trip assembly  14   e  is pushed onto the driving tool  12   e . Engagement of the detent pin  1232  to the second recess  1234  positions the second mount structure  1210  relative to the contact trip housing  70   e  such that the second lugs  1212  will be aligned axially to the first lugs  1202  to thereby inhibit axial withdrawal of the contact trip assembly  14   e  from the driving tool  12   e.    
     The contact trip housing  70   e  and driving tool  12   e  can be configured such that engagement of the contact trip housing  70   e  to the driving tool  12   e  inhibits rotation of the contact trip housing  70   e  relative to the driving tool  12   e . A bushing portion  1240  in the contact trip housing  70   e  can be threadably coupled to the nose element  72   e  to permit adjustment of the depth to which a fastener may be installed. The nose element  72   e  can be biased outwardly from the contact trip housing  70   e  via a spring  1006   e . The sensor target  1002   e  can be movably mounted on the contact trip housing  70   e  for axial movement with the nose element  72   e . More specifically, the sensor target  1002   e  can be mounted on an arm  1244  that can be coupled to the bushing portion  1240  such that the bushing portion  1240  can be rotated relative to the arm  1244  but axially translation of the bushing portion  1240  will cause corresponding translation of the arm  1244  (and therefore the sensor target  1002   b ). In the particular example provided, the arm  1244  includes an L-shaped tab  1250  ( FIG. 30 ) that is received into a groove  1252  ( FIG. 30 ) formed about the bushing portion  1240 . It will be appreciated that because the bushing portion  1240  is threaded to the nose element  72   e , and because the arm  1244  is axially fixed to the bushing portion  1240 , the spring  1006   e  that biases the nose element  72   e  outwardly away from the gear case  40   e  will also serve to bias the sensor target  1002   e  (which is coupled to an end of the arm  1244  opposite the tab  1250 ) away from the sensor  1000   e  that is mounted in the gear case  40   e . In contrast to the manner in which the previous example operates, the controller (not specifically shown) is configured to permit operation of the motor assembly (not specifically shown) when the sensor target  1002   e  is spaced apart from the sensor  1000   e  and to inhibit operation of the motor assembly when the sensor target  1002   e  is disposed within a predetermined distance from the sensor  1000   e . Accordingly, it will be appreciated that during the run-in of a fastener the abutting face  112   e  of the nose element  72   e  will contact the surface of a workpiece such that the continued run-in of the fastener will cause the nose element  72   e  to be driven rearwardly against the bias of the spring  1006   e  to thereby translate the sensor target  1002   e  rearwardly toward the sensor  1000   e.    
     In the example of  FIGS. 31 through 34 , another coupling means for releasably coupling the contact trip assembly  14   f  to the driving tool  12   f  is illustrated. In this example an annular retaining clip or hog ring  1300  is mounted to the contact trip housing  70   f  and can engage a groove  1302  formed in a mount structure  1304  that is coupled to the gear case  40   f . The remainder of the driving tool  12   f  and the remainder of the contact trip assembly  14   f  can be generally similar to that of the driving tool  12   f  and that of the contact trip assembly  14   f , respectively, that are described and illustrated in conjunction with the previous example. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.