Patent Publication Number: US-10330307-B2

Title: Printing system and method for printing substrates

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit and priority of German Application No. 10 2015 205 122.6 filed 20 Mar. 2015. The entire disclosure of the above application is incorporated herein by reference. 
     FIELD 
     The invention relates to a screwdriver. 
     BACKGROUND 
     Screwdrivers are well-known. They function to tighten or loosen screws. The screws are typically provided with a head that includes an engagement contour that a bit or a screwdriver blade engages. Other screws without a head are also well-known that include an engagement contour at one end and are identified as set screws. These known screwdrivers are characterized in that the screws are tightened or also loosened by means of manual torque that is introduced through a handle of the screwdriver. What is possible, in particular, when tightening these screws is to apply the torque with considerable sensitivity. This is critical, in particular, for screws having a small diameter of ≤1.6 mm. It is thus easily possible to avoid unintentionally shearing off the screw. Electrically operated screwdrivers are also well-known. They function to facilitate tightening or loosening screws. Driven screwdrivers are frequently equipped with a torque limiter that serves to limit the torque applied to a screw to a desired value. It has been found that these screwdrivers cannot be adjusted with sufficient sensitivity. On the other hand, conventional screwdrivers that are employed manually are disadvantageous when used for a large number of screwed connections because the use thereof is tiring and time-consuming. 
     SUMMARY 
     The object of the invention is therefore to provide a screwdriver that both enables screws to be tightened and loosened quickly and without fatigue, but at the same time also allows for a very sensitive working procedure. 
     In order to achieve this object, a screwdriver is provided that comprises the features referenced in claim  1 . The screwdriver according to the invention includes a handle extending along the longitudinal axis thereof, which handle functions to securely hold the screwdriver and to introduce torque into the screwdriver. A bit holder is provided at one end of the handle, the bit holder extending in the direction of the longitudinal axis, or a screwdriver blade is provided extending in this longitudinal axis, whereby the term screwdriver blade mentioned here is a conventional blade of a screwdriver that engages a slot of a screw, for example. This term also comprises blades for Phillips screws, socket head screws, Torx screws, or the like—and finally also such screws that by means of a multi-sided edge grasp a corresponding complementarily shaped screw head or a nut so as to enable torque to be applied. The screwdriver is characterized in comprising a drive mechanism in the handle, by means of which the bit holder or screwdriver blade can be made to rotate relative to the handle, thereby enabling torque to be applied to a screw or, as explained above, to a nut, in order either to tighten or loosen these. The drive mechanism includes a motor that can generally be driven electrically, as well as a freewheel through which the motor can be coupled to the bit holder or the screwdriver blade. The freewheel is designed here to decouple the motor from the bit holder or the screwdriver blade whenever manual torque is applied to the bit holder or the screwdriver blade. Finally, the screwdriver is characterized in that the drive mechanism includes a torque limiter by which the output torque that is acting on the screw to be tightened or loosened can be limited to a desired value that is less than the shearing torque of the screw. Once the desired maximum torque has been reached, the motor stops without building up any further increased torque. The motor of the drive mechanism enables a screw to be tightened until the maximum torque is reached that has been set by the torque limiter. The screw in this phase is screwed tight quickly without any manual actuation, including grasping, and without fatiguing the user. The motor stops once the maximum torque is reached. The user can now continue to turn the screwdriver manually and very sensitively apply to the screw a torque that exceeds the torque set by the torque limiter. The bit holder or the screwdriver blade are decoupled from the motor by the freewheel when manual torque is applied, thereby preventing the motor from being negatively affected as the screwdriver continues to be operated. The screwdriver can be used especially preferably for screws, in particular, those having a thread of ≤2.5 mm, in particular, ≤1.6 mm. The final manual sensitive tightening of the screws prevents the screws from being sheared off. 
     A preferred embodiment of the screwdriver is characterized in that the freewheel has a double action whereby the above-described advantages can be utilized not only when a screw is tightened but also when it is loosened. In the event a screw or nut is stuck in place due to contamination or rust, the torque applied by the motor can be limited to a value below the shear-off torque, thereby allowing a user to apply loosening torque to the screw or nut manually with high sensitivity and to avoid any unintentional shearing off. 
     Another embodiment of the screwdriver is characterized in that the drive mechanism includes a gear unit that enables a screw being tightened or loosened to rotate faster than for manual tightening. 
     An embodiment of the screwdriver is preferably characterized by a switching ring of a switching device by which the motor of the drive mechanism of the screwdriver can be actuated, preferably with clockwise or counterclockwise rotation. 
    
    
     
       BEST DESCRIPTION OF THE DRAWINGS 
       The following discussion describes the invention in more detail based on the drawing. Here: 
         FIG. 1  is a side view of a screwdriver according to the invention; 
         FIG. 2  is a longitudinal section through the screwdriver in  FIG. 1 ; 
         FIG. 3  is a cross section through the screwdriver in  FIG. 1  along line III-III; 
         FIG. 4  is an exploded view of the screwdriver; and 
         FIG. 5  is a cross section through the screwdriver in  FIG. 1  along line V-V. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is side view of a screwdriver  1 . The screwdriver includes a handle  3  extending in the direction of a longitudinal axis  5 . Handle  5  of the embodiment shown here includes an essentially barrel-shaped convex force rotation zone  7  having a first outer diameter, as well as a so-called twirl zone  9  adjoining on the left and a smooth terminal section  11  to the right of force rotation zone  7 , which section easily slides within the hand of a user when pressure is applied, thereby avoiding an excessively high mechanical load on the inner surface of the hand. 
     A section comprising a bit holder  13 , this section being rotationally supported relative to handle  3 , adjoins twirl zone  9  of handle  3  on the left. It is possible here to provide also directly on handle  3  a section comprising a screwdriver blade of the type referenced above, which section is designed to rotate relative to the handle, the blade extending in the direction of longitudinal axis  5 . Bit holder  13  is disposed coaxially relative to longitudinal axis  5 . 
     A flat section  17  is provided in the outer surface  15  of handle  3  here in the left region of twirl zone  9 , this flat section acting as roll-off protection, that is, preventing screwdriver  1  from rolling on a slightly oblique surface and falling on the floor. 
     Either all or parts of outer surface of handle  3  can also be provided with especially slip-proof materials, thereby allowing the handle to rest especially well within the hand and enabling a relatively high torque to be transferred. In particular, commercially available handle  3  of screwdriver  1  can also be employed in connection with screwdriver  1  described here. Finally, handle  3  preferably has an overall ergonomic design so as to allow working with screwdriver  1  of the type described here in a way that is fatigue-free and reduces effort. 
     The outer contour described here of handle  3  is ultimately of no significance for the invention. The critical aspect here is that screwdriver  1  includes a more or less cylindrical handle  3  of longitudinal axis  5 , and a section disposed coaxially and offset therefrom that can rotate relative to handle  3 , that is, effect a relative rotation, wherein the rotational axis of the relative rotation coincides with longitudinal axis  5 . This rotational section includes bit holder  13  or is provided directly with a screwdriver blade. 
     Handle  3  is provided with a switching device  19 , by means of which a drive mechanism effecting the relative rotation of the left section of screwdriver  1  is actuated. In terms of a switching device, what is typically used in connection with motor-driven screwing devices are push-button switches, toggle switches, rocker switches, slide switches, or the like. Switching device  19  depicted here of screwdriver  1  preferably includes a switching ring  21 , where the term switching ring  21  also identifies a ring segment that extends only over a limited circumferential region of handle  3 . In order to provide ease of operation for switching device  19 , switching ring  21  preferably extends over a further circumferential region of handle  3 , thereby allowing the handle to be operated, in other words moved in a circumferential direction, by a user to as many rotational positions of screwdriver  1  as possible. The term circumferential direction here refers here to a direction that preferably runs essentially coaxially relative to longitudinal axis  5 . 
       FIG. 2  provides a longitudinal section of screwdriver  1  in  FIG. 1 , where the sectional plane is oriented such that longitudinal axis  5  lies within this plane. Identical or functionally equivalent elements are provided with the same reference characters, and with this in mind reference is made to the preceding description. 
     This illustration of screwdriver  1  reveals that a drive mechanism  23  is disposed inside handle  3 . This mechanism comprises a motor  25  that is preferably provided here in the form of an electric motor and is supplied with electrical power by an energy storage means  27 . A cord connection between motor  25  and an energy source is in principle also possible. However, the embodiment shown here is preferred, which is characterized by energy storage means  27  that is integrated in screwdriver  1 , preferably in handle  3 , the energy storage means being implemented, in particular, as a rechargeable battery. Obviously replaceable batteries can also be used instead. In addition, provision is made, in particular, whereby the battery can be replaced as necessary. 
     Motor  25  can be supplied selectively with power from energy storage means  27 . To this end a switching device is provided that supplies motor  25  with power as required and that is also preferably designed to provide clockwise or counterclockwise operation of the motor, and thus clockwise or counterclockwise operation of a bit inserted in bit holder  13 , or of a screwdriver blade. 
     Terminal section  11  of handle  3  is implemented in the form of a removable cap enabling energy storage means  27  to be replaced. Motor  25  acts here on bit holder  13  through gear unit  29  and, in particular, a freewheel  31 . Although freewheel  31  is absolutely required in screwdriver  1  described here, gear unit  29  can be eliminated—particularly in the event corresponding control means are provided for the rotational speed of motor  25 . 
     Gear unit  29  depicted here is preferably provided in the form of a two-stage planetary gear unit. This unit is characterized by an especially compact constructive design, one that is short as viewed in the direction of longitudinal axis  5 . It is furthermore possible to specify the gear ratio between the rotational speed of motor  25  and of bit holder  13  within a wide range. 
     Switching unit  19  includes additional components, as is evident in the sectional view. Seen here in particular is a component support unit provided as circuit board assembly  33  that is described below in more detail. 
     The sectional view of  FIG. 2  also reveals that bit holder  13  includes receptacle section  35  for a bit, which section runs in the direction of longitudinal axis  5  and is disposed coaxially relative to this axis, a collar  37  running radially relative to longitudinal axis  5 , as well as a stub shaft  39 . The stub shaft—as viewed in the direction of longitudinal axis  5 —is sufficiently short so as to engage only freewheel  31  and not gear unit  29 . This provides a very short and compact constructive design. 
     The sectional view of  FIG. 2  also shows that handle  3  includes a base body  41  that surrounds the interior space  43  of handle  3  in which drive mechanism  23  is accommodated, and that also accommodates switching ring  21  in an appropriate recess, here a circumferential groove  45 . Groove  45  running circumferentially is sufficiently long so as to accommodate switching ring  21 . If the ring is provided in the form of an annular segment, groove  45  can be correspondingly short—as viewed in the circumferential direction. Groove  45  must in any case be sufficiently long to enable the switching ring to mover therein. This allows a switching procedure to be effected. This is described in more detail below. 
     Bit holder  13  of screwdriver  1  is surrounded by a housing  47  so that bit holder  13  is held securely, an attractive external design for screwdriver  1  is provided, and furthermore bit holder  13  is covered. 
       FIG. 3  is a cross section through screwdriver  1  along line III-III depicted in  FIG. 1 . Identical or functionally equivalent elements are provided with the same reference characters, and with this in mind reference is made to the preceding description. 
     The sectional plane chosen in  FIG. 3  is oriented such that longitudinal axis  5  is perpendicular thereto. 
     Screwdriver  1  is shown in  FIG. 3 . Flat sections  17  can be seen on the top and bottom that prevent screwdriver  1  from rolling away.  FIG. 3  depicts stub shaft  39  of bit holder  13 , the stub shaft extending into freewheel  31 . The freewheel comprises a number rolling elements  49 , here preferably three such bodies also identified as clamping rollers, that interact with a number of clamping jaws  51 . Three clamping jaws  51  are provided here matching the number of rolling elements  49 . Rolling elements  49  and clamping jaws  51  are disposed inside a closed ring  53  of freewheel  31 . The inside dimensions of ring  53  are selected so that rolling elements  49  and clamping jaws  51  are disposed within an annular section between the inside surface of ring  53  and the outside of stub shaft  39 . Clamping jaws  51  are provided in the broadest sense as annular segments, for which the size as measured circumferentially is selected so that in each case a free space remains between clamping jaws  51 , which are disposed an equal distance apart as viewed circumferentially, in which space rolling elements  49  are disposed. Clamping jaws  51  are attached to an annular body, which is not visible here but is depicted in  FIG. 4 , which body is disposed coaxially relative to longitudinal axis  5  and is made to rotate by motor  25  when motor  25  has been supplied with power. When the annular body rotates, clamping jaws  51  revolve around a circular path about the longitudinal axis  5 . Three rolling elements  49  are disposed axially parallel to longitudinal axis  5  of screwdriver  1  and are driven by clamping jaws  51  so that they also revolve around a circular path about the longitudinal axis. Clamping jaws  51  interact with the outer surface of stub shaft  39  such that torque from motor  25  is transferred through clamping jaws  51  to stub shaft  39  when clamping jaws  51  rotate. The rotation of the annular body, which is effected by motor  25 , in other words acts through clamping jaws  51  causing stub shaft  39  and thus also bit holder  13  to rotate. The maximum predetermined torque can be achieved which may be applied by motor  25  to bit holder  13 , and thus also to the screw, both when tightening a screw and also loosening a stuck screw. Motor  25  in this case stops without applying increased torque to bit holder  13 . 
     In the event a screw must now be further tightened or loosened manually by screwdriver  1  after reaching the maximum torque to be applied by the motor, handle  3  is made to rotate very sensitively by the user and is acted upon by a manually applied torque. 
     When handle  3  turns, the lock ring  73  that is also connected in a rotationally fixed manner to the handle is also made to rotate. As a result, rolling element  49  is clamped into a tapered gap between the inner surface of lock ring  73  and the outer surface of stub shaft  39 , with the result that in this working phase manual torque acts on stub shaft  39  and thus on bit holder  13  so that a bit accommodated here causes a screw to rotate. When handle  3  is turned manually, lock ring  73 , but also gear unit  29 , which is supported in a rotationally fixed manner in handle  3 , is made to rotate by motor  25 . 
     In response to a rotation of motor  25  and a rotation of annular body  65 , which is effected by preferably provided gear unit  29 , clamping jaws  51  rotate and effect a rotation of stub shaft  39  of bit holder  13 . The design of freewheel  31  allows torque in this operating mode to be applied to the drive side, that is, bit holder  13  exclusively through motor  25 , gear unit  29 , annular body  65 , and clamping jaws  51 . 
     When motor  25  stops once the maximum specified torque has been reached at which a screw has not yet been sheared off, it is possible as described above to manually apply torque to bit holder  13  by continuing to manually turn handle  3  and thus also lock ring  73 . In this mode of freewheel  31 , torque is applied exclusively through handle  3 , lock ring  73 , and rolling elements  49  that are clamped between inner surface of lock ring  73  and outer surface of stub shaft  39 . The fact that clamping ring  73  in this operating mode is moved synchronously together with gear unit  29  and motor  25  creates torque relief, that is, the torque that is applied manually and introduced into handle  3  is not transferred back through freewheel  31  into gear unit  29 , and/or motor  25 . This torque relief during application of manual torque to bit holder  13  ensures that no portion of the manual torque is passed back into gear unit  29  and/or motor  25  during the application of manual torque to bit holder  13  when a screw is tightened or loosened manually. As a result, these two elements of screwdriver  1  are protected from being damaged. 
     Stub shaft  39  of bit holder  13  can thus ultimately be acted upon by torque applied by motor  25 , with the result that depending on the rotational direction of motor  25  bit holder  13  rotates about longitudinal axis  5  to the right to tighten a screw or to the left to loosen a screw. 
     When manual torque is applied by means of a rotational movement of handle  3 , the torque is transferred to stub shaft  39  of bit holder  13 , which then turns in the intended direction. 
     There are thus two ways—by motor and manually—that torques can act on stub shaft  39  and produce a rotation of the bit holder. Freewheel  31  ensures that no damage occurs in drive mechanism  23  when manual torque is introduced into handle  3  due to the torque relief for gear unit  29  and motor  25 . 
     Drive mechanism  23 , as explained above, is equipped with a torque limiter, with the result that rotation of clamping jaws  51  effected by motor  25  is stopped as soon as a predeterminable output torque is applied to stub shaft  39 . The limitation of torque is implemented by the design of drive mechanism  23 . The maximum output torque for the motor drive is selected so that a screw being tightened by screwdriver  1  cannot shear off. It should be noted that the maximum output torque is also selected so as to prevent a screw from shearing off when being unscrewed. 
     Freewheel  31  is ultimately selected so as to enable torque to be applied by screwdriver  1  manually through freewheel  31  to bit holder  13  or to a screwdriver blade provided here whenever rotation of rolling elements  49  and stub shaft  39  produced by motor  25  is stopped once the maximum predetermined output torque has been reached. Freewheel  31  in this operating mode provides torque relief so that torque applied manually to handle  3  of screwdriver  1  does not damage motor  25  and optionally provided gear unit  29 . A screw can be screwed in or loosened further with great sensitivity in this operating mode. 
     What is evident overall is that drive mechanism  23  makes it possible for a screw to be inserted quickly without being surroundingly gripped by screwdriver  1 , while allowing only a predetermined maximum output torque to act on the screw; this torque is less than the torque that would result in damage, in particular, a shear-off torque to the screw. Once the maximum set output torque has been reached, stub shaft  39  is not made to rotate further by motor  25 . Additional torque can, however, be transferred manually by means of handle  3  of screwdriver  1  through freewheel  31  to a screw, thereby enabling the screw to be inserted or loosened with great sensitivity. 
       FIG. 4  is an exploded view of the front—at the left in  FIGS. 1 and 2 —section of screwdriver  1 . Identical or functionally equivalent elements are provided with the same reference characters, and with this in mind reference is made to the preceding description. 
     The front-most end section of housing  77  is seen on the right-hand side of  FIG. 4 , which housing is disposed in a rotationally fixed manner in handle  3  of screwdriver  1 , not shown here, and surrounds gear unit  29 . A toothed gear structure  55  comprising teeth running parallel to longitudinal axis  5  is provided on the inside of housing  77 , these teeth being engaged by toothed gears of gear unit  29 , which toothed gears include an external toothing. 
     Screwdriver  1  depicted in  FIG. 4  thus relates to an embodiment that is provided with gear unit  29 . 
     The parts of gear unit  29 , here preferably designed as a two-stage planetary gear unit  57 , are seen in the exploded view to the left of twirl zone  9 . Planetary gear unit  57 —on the output side or the left in  FIG. 4 —includes three toothed gears  59  that are made to rotate by motor  25  provided in handle  3  and are moved along a circular path located coaxially relative to longitudinal axis  5 . Pins  63  engage a central opening  61  of toothed gears  59 .  FIG. 4  shows that gear unit  29  provided in the form of planetary gear unit  57  includes three toothed gears  59  that constitute the planet gears of the second stage of second stage of planetary gear unit  57 . Three toothed gears  59  are provided here, each of which includes a central opening  61 . Three pins  63  are correspondingly provided that engage these openings  61 . Pins  63  are attached to an annular body  65  that rotates about longitudinal axis  5  whenever pins  63  are made to rotate so as to rotate together with toothed gears  59  along a circular path running concentrically relative to longitudinal axis  5 . 
     Three clamping jaws  51  are installed on annular body  65  in a rotationally fixed manner on the side opposite pins  63 , which clamping jaws are disposed—as viewed circumferentially relative to center axis  5 —equidistant from each other, as are pins  63 , in other words here with an angular spacing of 120°. Annular body  65  and clamping jaws  51  can preferably also be provided as one integrated piece. 
     Respective rolling elements  49 , which are disposed so as to rotate freely in freewheel  31 , are disposed between clamping jaws  51 , while motor  25  causes bit holder  13  to rotate. Three rolling elements  49  and three clamping jaws  51  are provided in the embodiment shown here. 
     Rolling elements  49  and clamping jaws  51 , which are located on an imaginary circular path that is disposed concentrically relative to longitudinal axis  5 , describe a free space  71  that stub shaft  39  of bit holder  13  engages. 
     Annular body  65  rests against lock ring  73  that is supported in a rotationally fixed manner in handle  3  and includes at least one retaining arm  75 , here two opposing retaining arms  75  that run essentially radially relative to longitudinal axis  5 . These arms are fixed within screwdriver  1 . 
     A bearing device  81  is provided between the collar  37  of bit holder  13 , which collar runs radially relative to longitudinal axis  5 , and a contact surface  79  of lock ring  73 , this surface facing toward bit holder  13 , which bearing device enables bit holder  13  to rotate with low friction relative to lock ring  73  that is fixed within handle  3  and thus within screwdriver  1 . An annular bearing is provided here that comprises a ball cage  83  in which a number of bearing elements is provided—preferably equidistant as viewed in the circumferential direction of longitudinal axis  5 —these elements here being in the form of balls. 
     The housing  47  over bit holder  13  has in fact been omitted in  FIG. 4  so as to more easily reveal the elements shown here. 
       FIG. 5  provides a cross section through screwdriver  1  shown in  FIGS. 1 and 2  along line V-V in  FIG. 1 . The sectional plane is selected here such that longitudinal axis  5  is oriented perpendicular to this plane. Identical or functionally equivalent elements are provided with the same reference characters, and with this in mind reference is made to the preceding description. 
       FIG. 5  depicts switching device  19 , here including switching ring  21 , which device is disposed concentrically relative to longitudinal axis  5  seen in  FIGS. 1 and 2 , and is supported enabling it to rotate on handle  3  of screwdriver  1 . A partial section  87  of base body  41  of handle  3  is seen in  FIG. 5 , which section—as viewed in cross section—is essentially circular and includes an outer surface  89  with an outer diameter that is designed so that outer surface  89  contacts the inner surface  91  of switching ring  21  such that switching ring  21  is guided so as to slide along partial section  87  of base body  41 . 
     Partial section  87  includes two opposing projections  93  that engage an annular-segment-shaped cutout  95  in inner surface  91  of switching ring  21 . The illustration in  FIG. 5  reveals two opposing projections  93 . It is possible also to provide only one such projection or also more than two. One elastic element  97  each, in the form of helical springs in the embodiment depicted here, is provided in cutout  95  to the right and left of projection  93 , which element is supported on the essentially radial inside of cutout  95 . 
     Switching ring  21  can be rotated on partial section  87  clockwise or counterclockwise against the force of elastic elements  97  that are disposed under initial tension between the side walls of cutout  95  and the side walls of at least one projection  93 . When switching ring  21  is turned counterclockwise, the elastic elements turn the ring back to the initial position shown in  FIG. 5 , with the result that external torque is no longer applied to the ring. The same is true when the switching ring is turned in the opposite rotational direction. 
     Switching ring  21  includes a switching arm  99  that projects over an inner surface  91  of the ring in the direction of longitudinal axis  5 , which arm is rotationally fixed to switching ring  21  and is moved together with the ring whenever there is rotational motion thereof. Whenever switching ring  21  rotates counterclockwise in  FIG. 5 , switching arm  99  interacts with a first switching element  101 . Switching device  19  in the embodiment shown here is designed so that a second switching element  103  is actuated whenever switching ring  12  in  FIG. 5  rotates clockwise. Switching device  19  in the embodiment shown here is thus designed to actuate first switching element  101  or second switching element  102  depending on the rotational movement of switching ring  21 . This enables bit holder  13  to rotate in one direction, for example clockwise, or in the opposite direction, for example counterclockwise, depending on the rotational movement of switching ring  21 . A screw can thus be tightened or loosened by means of bit holder  13  depending on how switching ring  21  is actuated. In corresponding fashion, a screwdriver blade provided instead of bit holder  13  can be made to rotate clockwise or counterclockwise. 
     It is also possible in principle to design switching elements  101  and  103  to effect fast or slow rotation of the bit holder or of the screwdriver blade as a function of the relative position of switching arm  99  relative to switching elements  101 ,  103 . 
     Switching elements  101  and  103  are part of circuit board assembly  33  that was also referenced in connection with the explanatory comments relating to  FIG. 2 . Aside from switching elements  101  and  103 , this circuit board can also include other components, such as, for example, contacts  105  and  107  through which motor  25  can be connected to energy storage means  27 . 
     Energy storage means  27  is preferably designed as a battery. This can be replaceable and/or rechargeable. In the embodiment shown here, a contact unit  109  is provided on circuit board assembly  33 , preferably in the form of a USB connector, through which contact unit energy storage means  27  can be charged. 
     Provision is preferably made whereby switching ring  21  in this embodiment includes a cutout  111  that is covered by a protective cap  113 . The cap is held captively within switching ring  21  but can be removed to allow access to contact unit  109  for charging energy storage means  27 . 
     Circuit board assembly  33  can be equipped with a charge status display that can be seen through an inserted optical conductor, or through a translucent or clear viewing window that is provided there. In addition, a light source can be provided on circuit board assembly  33 , the light source illuminating the working space of screwdriver  1  through appropriate optical conductors. However, it is also possible to connect a light source to circuit board assembly  33 , the light source being disposed and oriented in housing  47 , for example, so as to illuminate the working space of screwdriver  1 .