Patent Publication Number: US-10328565-B2

Title: Portable power tool

Description:
This application claims the priority of International Application No. PCT/EP2014/068566, filed Sep. 2, 2014, and European Patent Document No. 13182607.5, filed Sep. 2, 2013, the disclosures of which are expressly incorporated by reference herein. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to a portable power tool, e.g., an electric screwdriver, a hammer drill, which is equipped with a manually switchable gear unit. 
     The portable power tool has a tool holder for receiving a tool, a motor, at least one switchable gear stage, and a slider. The gear stage couples the motor in a driving manner to the tool holder. The gear stage has a gear element, which is movable in a switching direction, with a toothing, which in a first gear position is engaged with a corresponding toothing, and which in a second gear position is disengaged from the corresponding toothing. The slider can be displaced by a user between at least a first switch position and a second switch position in the switching direction, wherein the first switch position is assigned to the first gear position and the second switch position is assigned to the second gear position. The slider has a finger. A coupling device has a carriage that is movable in the switching direction and a catch for the carriage to a housing. The carriage is connected to the movable gear element. The catch latches in the first gear position and the second gear position, and the catch is not latched in positions between the first gear position and the second gear position. The first and second gear positions are directly adjoining so to speak. The carriage is moved on the path between the two gear positions, but is not meant to come to a stop on it. A spring element has a springy first section and a springy second section, wherein both sections each have an end attached to the carriage and an end that is movable relative to the carriage. The finger is arranged along the switching axis between the sections. 
     The coupling device conveys the actuation of the slider to the gear element. The coupling device advantageously prevents the gear element from stopping on the path between two gear positions, even if the user pushes the slider in a position between two gear positions. In addition, the coupling device prevents damaging the gear element, since the user cannot forcibly push it out of or in engagement with a toothing in the event of blocking. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1, 2  depict an electric screwdriver; 
         FIG. 3  depicts a switching device during a change of a gear position; 
         FIG. 4  depicts a coupling part of the switching device after the change has occurred; 
         FIG. 5  depicts a switching device during a change of a gear position; and 
         FIG. 6  depicts a coupling part of the switching device after the change has occurred. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Identical elements or those having similar functions are indicated in the drawings by means of identical reference signs, unless stated otherwise. 
       FIGS. 1 and 2  schematically depict an electrical screwdriver  1  as an example of a portable power tool. The electric screwdriver has a tool holder  2 , into which a tool  3 , e.g., a screwdriver bit, a drill bit  3 , can be inserted. An electrical motor  4  drives the tool holder  2  about its work axis  5 . The electrical power supply of electric motor  4  may come from a battery  6 , which is removably attached to a housing  7  of electrical screwdriver  1 . The user can operate the portable power tool with a system button  8  and control it during operation by means of a handgrip  9 . 
     Electric screwdriver  1  is provided with a switchable gear stage  10 . Model gear stage  10  allows users to select between two different gear reductions. Model gear stage  10  has a drive-side sun gear  11 , which is coupled to drive shaft  12  of motor  4 . Planetary gears  14  arranged on planetary carrier  13  mesh with sun gear  11 . A gear ring  15  also engages with planetary gears  14 . Gear ring  15  can be displaced along working axis  5  between two provided gear positions. Gear ring  15  is coupled in a first gear position, for example purposes, in a rotationally rigid manner with housing  7  ( FIG. 1 ) and in a second gear position in a freely rotating manner relative to the housing ( FIG. 2 ). For example, housing  7  has a radial toothing  16 , which engages in a corresponding toothing  17  of gear ring  15 . In the second gear position, gear ring  15  can be rotated relative to housing  7  about working axis  5 . Toothing  16 ,  17  is detached. 
     A slider  18  is provided externally on housing  7 . Slider  18  is connected via a coupling device  19  to gear ring  15 . The user can displace slider  18  along a switching axis  20  between a first switch position and a second switch position, which are each assigned to one of the gear positions of gear ring  15 . Coupling device  19  ensures that gear ring  15  only occupies the provided gear positions and cannot remain on the path between gear positions. In addition, coupling device  19  enables one to uncouple the switch position of slider  18  and the gear position of gear ring  15  on an intermittent basis. For example, slider  18  can already be actuated when the current angle setting of gear ring  15  inhibits its toothing  16  to be pushed on toothing  17  of housing  7 . 
     Slider  18  and coupling device  19  are depicted in  FIG. 3  as an isometric section, in which slider  18  is in a changed switch position and gear ring  15  with the gear position has not yet ensued.  FIG. 4  depicts coupling device  19  in a matched switch position and gear position. 
     Coupling device  19  has a carriage  21 , which can be moved parallel to slider  18 . Carriage  21  is preferably rigidly connected to the gear element to be moved, in this case gear ring  15 . The alignment of slider  18  and carriage  21  is thus preferably oriented to switching axis  20  of the gear element. 
     Carriage  21  is equipped with two pins  22 ,  23 . First pin  22  is offset relative to second pin  23  transversely to switching axis  20 . On first pin  22 , there is fitted a coil spring  24  with two protruding arms  25 ,  26 . Arms  25 ,  26  thus each have an end  27 ,  28  attached to first pin  22  and a free end  29 ,  30 . Arms  25 ,  26  are permanently affixed with one of their ends  27 ,  28  to first pin  22 . The two arms  25 ,  26  extend from first pin  22  to second pin  23 . The free ends  29 ,  30  of arms  25 ,  26  contact second pin  23  in such a manner that pin  23  is arranged along switching axis  20  between the two arms  25 ,  26 . The one arm  25  contacts one side of pin  23 , which points in one switching direction  31 , and the other arm  26  contacts a side of pin  23 , which points opposite switching direction  31 . Arms  25 ,  26  may be pressed on to second pin  22  in a preloaded manner. 
     Slider  18  has a finger  32 , which engages between both arms  25 ,  26 . Finger  32  thus lies in switching direction  31  in front of one arm  25  and after the other arm  26 . Arms  25 ,  26  contact opposing sides  33 ,  34  of finger  32 . Finger  32  and the two pins  22 ,  23  lie in one line when gear position of slider  18  matches the switch position of gear ring  15 . In the depicted embodiment, finger  32  is arranged between first pin  22  and second pin  23 . If slider  18  is deflected out of a switch position into switching direction  31 , an offset of finger  32 , relative to second pin  22 , results parallel to switching axis  20 . Finger  32  deflects one of the two arms  25  in switching direction  31 , while the other arm  26 , impeded by the second pin  23 , does not follow the deflection of the one arm  25 . Both arms  25 ,  26  are consequently pressed apart against their spring force. On carriage  21 , a switching force exerted by coil spring  24  acts in switching direction  31 . Carriage  21  follows the movement of slider  18 , by which pins  22 ,  23  come back in line with finger  32  and the spring force is minimized. 
     The construction with coil spring  24  is simple to execute, among other things because coil spring  24  can be obtained as a common standard product and installation of coil spring  24  is simple to accomplish. Second pin  23  is advantageous because it prevents a swiveling of the entire coil spring  24  about first pin  22 . Coil spring  24  can thereby be seated rotatably on first pin  22 . Alternatively, coil spring  24  is secured against swiveling or turning about first pin  22 , and second pin  23  can be omitted. 
     Carriage  21  has a catch  35  with housing  7 . Catch  35  engages each time when carriage  21  or the gear element has reached the intended gear position. Catch  35  requires that a pushing force acting on carriage  21  along switching axis  20  must exceed a threshold value so that carriage  21  is moved out of a gear position. Model catch  35  contains multiple recesses  36 , depending on the number of gear positions, which are formed one after the other along switching axis  20  in housing  7 . The spacing of the recesses  36  corresponds to the spacing of the gear positions. Carriage  21  has a projection  37 , protruding transversely to switching axis  20 , which engages in one of the recesses  36 . Recesses  36  and projection  37  have sides preferably inclined to switching axis  20 . Due to the sides, projection  37  is pressed out of recess  36  given a sufficient pushing force along switching axis  20 . Projection  37  can be arranged on a spring  38 , against whose spring force projection  37  can be deflected out of recess  36 . Spring  38  can be executed for example by a slit  39 , adjoining projection  37  in the deflection direction, in carriage  21 . 
     The switching force exerted by coil spring  24  must overcome the threshold value specified by catch  35  before carriage  21  can follow the movement of slider  18 . The threshold value is preferably selected in such a manner that carriage  21  first moves when the switching force drives carriage  21  to the next catching position, i.e., gear position. The threshold value lies between 50% and 100% of a switching force, e.g., between 75% and 90%, which coil spring  24  produces given an offset between slider  18  and carriage  21  equal to distance  40  between gear positions, e.g., recesses  36 . The distances between the gear positions of slider  18  are preferably equal to distances  40  between the gear positions. A user can preferably push slider  18  somewhat, e.g., 10% to 40% of distance  40 , out over a switch position to activate a switch process. Carriage  21  jumps into the next gear position and catches in it. As soon as the user releases slide  18 , the remaining switching force ensures the return of slider  18 . The threshold value can be adjusted by the spring force of spring  38  and the shape of the sides of projection  37  or recesses  36 . 
     Slider  18  and a different coupling device  41  are depicted in  FIG. 5  as an isometric section, in which slider  18  is in a changed switch position and gear ring  15  with the gear position has not yet ensued.  FIG. 4  depicts coupling device  41  when the switch position and gear position match. 
     Slider  18  and catch  35  of carriage  21  to housing  7  are identical to the design described relating to  FIGS. 3 and 4 , which is why these are referred to. 
     Carriage  21  has a spring element  42  with two springy sections  43 ,  44  folded along switching axis  20 . The two folded sections  43 ,  44  are arranged one after the other parallel to switching axis  20 . Each of the sections  43 ,  44  has an end  45 ,  46 , which is attached to carriage  21 . The respective other end  47 ,  48  of the folded sections  43 ,  44  is free relative to carriage  21 . The two free ends  47 ,  48  lie along switching axis  20  between the two attached ends  45 ,  46  preferably in the center. The two free ends  47 ,  48  are connected to each other. A runner  49  can be mounted on the two free ends  47 ,  48  in a manner that connects these. Runner  49  is movable relative to carriage  21  along switching axis  20 . Carriage  21  and spring element  42  are preferably designed in one piece. Consequently, carriage  21  and spring element  42  are continuously out of the same material and without connecting joints. 
     Slider  18  is connected to the center of spring element  42 , e.g., runner  49 . Slider  18  can have a rider  50 , which encompasses runner  49  in a form-fitting manner. Runner  49  and rider  50  form a two-part counter-piece to finger  32  of the preceding embodiment. Carriage  21  can be preassembled; slider  18  is placed with rider  50  on runner  49 . When displacing slider  18  in switching direction  31 , spring element  42  is preloaded, front section  44  is under load in switching direction  31 , and rear section  43  is compressed in switching direction  31 . The resulting spring force serves as the switching force for carriage  21 . 
     Carriage  21  may have stops  51 , which limit a relative offset of runner  49  in relation to its rest position on carriage  21 . Carriage  21  preferably comes into contact with one of the stops  51  when the offset is greater than 150% of distance  40  of the gear positions. This offset results from a pushing of slider  18  by more than 150% out of one of the switch positions in whose associated gear position carriage  21  remains. For example, toothing  17  may be blocked. To prevent damage to the folded sections  43 ,  44 , these are uncoupled from runner  49  by stop  51 .