Patent Publication Number: US-11389940-B2

Title: Handheld power tool including a spindle locking device

Description:
CROSS REFERENCE 
     The present application claims the benefit under 35 U.S.C. § 119 of German Patent Application No. DE 102016224226.1 filed on Dec. 6, 2016, which is expressly incorporated herein by reference in its entirety. 
     BACKGROUND INFORMATION 
     The present invention relates to a handheld power tool including a tool housing, in which a drive motor for driving a drive spindle is situated, the drive spindle being assigned a tool holder for accommodating an insertion tool and the drive spindle being assigned a spindle locking device which is designed to prevent the drive spindle from twisting in relation to the tool housing during a spindle locking mode. 
     A handheld power tool of this type including a drive motor, situated in a tool housing, for driving a drive spindle is conventional. A fan wheel, which is made of plastic for weight reduction purposes, may be provided for cooling the drive motor. The drive spindle is assigned a tool holder for accommodating an insertion tool. A spindle locking device including a clamping ring and at least one blocking member is furthermore provided and the drive spindle is assigned at least one clamping surface. During a spindle locking mode of the spindle locking device the at least one blocking member is clamped between the at least one clamping surface and the clamping ring. In this way, the drive spindle is prevented from twisting in relation to the tool housing. 
     SUMMARY 
     The present invention provides a handheld power tool including a tool housing, in which a drive motor for driving a drive spindle is situated, the drive spindle being assigned a tool holder for accommodating an insertion tool and the drive spindle being assigned a spindle locking device which is designed to prevent the drive spindle from twisting in relation to the tool housing during a spindle locking mode. A fan wheel is provided which is intended at least for cooling the drive motor, at least 20 percent by volume of the fan wheel including a metal having a density of greater than or equal to 3.5 g/cm 3 . 
     The present invention thus makes it possible to provide a handheld power tool which includes a spindle locking device and a fan wheel and in which it is possible to achieve an increase in a corresponding inertia of the fan wheel by designing the fan wheel to be made at least 20 percent by volume of metal, thus achieving at least an improvement of a response behavior of the spindle locking device. In this way, a handheld power tool may be provided in which the spindle locking device may largely be prevented from responding when the drive motor is running and a comparatively reliable responding of the spindle locking device may be achieved when the drive motor is at a standstill. 
     The fan wheel preferably includes zinc, a zinc alloy, brass and/or steel. In this way, a cost-effective and robust fan wheel may be provided. 
     The fan wheel preferably includes a flange for forming a force-locked connection to a drive shaft which is assigned to the drive motor. As a result, the fan wheel may be driven safely and reliably. 
     According to one specific embodiment, the fan wheel includes a composite material which includes at least plastic or two different metals. The metal containing at least 20 percent by volume of the fan wheel may thus be designed in a simple manner. 
     A gear unit is preferably situated between the drive motor and the tool holder, the gear unit being designed in the manner of a planetary gear set and includes at least one planetary stage. A stable and robust gear unit may thus be provided in a simple way. 
     The at least one planetary stage preferably has at least one sun wheel and a ring gear, the sun wheel being movable in the radial direction of the gear unit at least 0.2 mm in relation to the ring gear. A suitable movability of the sun wheel in relation to the ring gear may thus be made possible in a simple and uncomplicated way. 
     The spindle locking device is preferably situated between the gear unit and the tool holder. A mechanical stress of the gear unit may thus be limited. 
     A torque clutch is preferably provided which is situated between the gear unit and the tool holder. It is thus possible to decouple the tool holder from the drive when a predefined torque is exceeded and an overload may thus be prevented at least for the most part. 
     According to one specific embodiment, the drive motor is situated in the area of a handle which is assigned to the tool housing. In this way, a gravity center of the handheld power tool may be formed at a distance from the tool holder. 
     The drive motor is preferably designed in the manner of an electronically commutated drive motor including a stator and a rotor which is provided with at least one permanent magnet. In this way, a safe and reliable drive motor may be provided. 
     According to one specific embodiment, the drive spindle is assigned at least one clamping surface which is assigned the spindle locking device including a clamping ring and at least one blocking member, the at least one blocking member being clampable between the at least one clamping surface and the clamping ring during the spindle locking mode of the spindle locking device in order to prevent the drive spindle from twisting in relation to the tool housing. 
     In this way, a robust and reliable spindle locking device may be provided. 
     The at least one blocking member preferably has a cylindrical design. In this way, a stable and robust blocking member may be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is explained in greater detail below with reference to the exemplary embodiments shown in the figures. 
         FIG. 1  shows a schematic view of a handheld power tool according to the present invention. 
         FIG. 2  shows a side view of the handheld power tool from  FIG. 1  including an opened tool housing. 
         FIG. 3  shows a perspective view of a drive motor which is assigned to the handheld power tool, of a fan wheel as well as of a spindle locking device. 
         FIG. 4  shows a sectional view of a cut-through  400  of the handheld power tool from  FIG. 1 . 
         FIG. 5  shows a sectional view of the drive motor and the fan wheel from  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
       FIG. 1  shows a handheld power tool  100  which preferably has a tool housing  105  including a handle  115 . At least one drive motor  180  is situated in tool housing  105  for driving a drive spindle  130  which is connected to a tool holder  140  and which is assigned a spindle locking device  190 . Moreover, an optional torque clutch  160  is provided preferably as demonstrated. 
     According to one specific embodiment, handheld power tool  100  is designed in the manner of a manually guided power tool and is connectable mechanically and electrically to a rechargeable battery pack  117  for a cordless power supply. In  FIG. 1 , handheld power tool  100  is designed as a cordless combi drill by way of example. It is pointed out, however, that the present invention is not limited to manually guided power tools and, in particular, to cordless combi drills, but may rather be used in different handheld power tools which include a drive spindle provided with a spindle locking device—irrespective of whether these handheld power tools are operated electrically, i.e. are battery- or mains-operated, or non-electrically. 
     In handheld power tool  100 , rechargeable battery pack  117  is used for the power supply to drive motor  180 , which is designed in the manner of an electric motor by way of example. Drive motor  180  is actuatable, i.e., may be switched on and off, via a manual switch  112 , for example, and is an electronically commutated motor. Drive motor  180  is preferably a DC motor including a stator ( 312  in  FIG. 3 ) and a rotor ( 314  in  FIG. 3 ) which is provided with at least one permanent magnet ( 512  in  FIG. 5 ). In this case, drive motor  180  is preferably situated in the area of handle  115 . Preferably, drive motor  180  is electronically controllable in such a way that a reverse operation as well as inputs with regard to a desired rotational speed are implementable. The mode of operation and the design of a suitable drive motor are conventional so that a detailed description thereof is dispensed with for the sake of a concise description. 
     Drive motor  180  is connected to drive spindle  130  via a gear unit  170  which is situated in tool housing  105 . Drive motor  180  is preferably situated in a motor housing  185  and gear unit  170  in a gear unit housing  175 , gear unit housing  175  and motor housing  185  being situated in tool housing  105  by way of example. Gear unit  170  is preferably situated between drive motor  180  and tool holder  140 . In this case, a drive shaft  182 , which is assigned to drive motor  180 , is preferably connected to gear unit  170 , gear unit  170  being connected to tool holder  140  via drive spindle  130 . 
     Gear unit  170  is designed to transfer a torque, which is generated by drive motor  180 , to drive spindle  130  and is, only by way of example, but not necessarily, a planetary gear set, which has different gear or planetary stages and which is rotatably driven by drive motor  180  during the operation of handheld power tool  100 . It is pointed out, however, that gear unit  170  may be also dispensed with depending on a selected design of drive motor  180 . 
     Drive spindle  130  is rotatably mounted with the aid of a bearing assembly in tool housing  105  and connected to tool holder  140  which is situated in the area of a front side  199  of tool housing  105  and includes a drill chuck  145  by way of example. According to one specific embodiment, the bearing assembly has at least two bearing points which are provided in tool housing  105  in an area downstream from gear unit  170 . Tool holder  140  is used for accommodating an insertion tool  150  and may be integrally connected to drive spindle  130  or may be connected to it in the form of an attachment. In  FIG. 1 , tool holder  140  is designed as a type of attachment by way of example and is fastened to drive spindle  130  via a fastening device  147  provided on same. 
     According to one specific embodiment, drive spindle  130  is assigned spindle locking device  190 , as described above, which is at least designed at least essentially to prevent drive spindle  130  from twisting in relation to tool housing  105  during the spindle locking mode. In this case, spindle locking device  190  may be triggered when drive spindle  130  twists in any arbitrary direction of rotation or only when it twists in a predefined direction of rotation. The spindle locking mode makes it possible to open or close tool holder  140  when drive motor  180  is at a standstill, for example. 
     Spindle locking device  190  is situated, by way of example, in the axial direction of drive spindle  130  between gear unit  170  and tool holder  140 , but may also be situated alternatively in a different suitable position, for example in gear unit  170  or between gear unit  170  and drive motor  180 . The mode of operation of spindle locking device  190  is conventional so that a detailed description of the mode of operation of spindle locking device  190  is dispensed with for the sake of a concise description. 
     At least one fan wheel  120  is preferably provided which is provided at least for cooling drive motor  180 . Preferably, at least 20 percent by volume of fan wheel  120  preferably [sic] includes a metal having a density greater than or equal to 3.5 g/cm 3 . Fan wheel  120  preferably includes zinc, a zinc alloy, brass and/or steel. Fan wheel  120  preferably includes a composite material which includes at least plastic or two different metals. In this case, fan wheel  120  preferably includes a flange ( 524  in  FIG. 5 ) for forming a force-locked connection to a drive shaft  182  which is assigned to drive motor  180 . 
     With the aid of above-described fan wheel  120 , a particular response behavior of spindle locking device  190  may be at least improved, a comparatively rapid and reliable response of spindle locking device  190  being enabled when drive motor  180  is at a standstill and a response being prevented at least essentially and preferably completely when drive motor  180  is running. Moreover, the response of spindle locking device  190  may be preferably improved in the case of torque fluctuations. Improving the response behavior of spindle locking device  190  makes it possible to at least reduce wear and tear of the individual components of spindle locking device  190 . In the context of the present description, a response is understood to mean that a rotational speed on the output side, for example a rotational speed of drive spindle  130 , of tool holder  140 , or of insertion tool  150 , is greater than a rotational speed on the drive side, for example of drive motor  180  or of a planet carrier ( 320  in  FIG. 3 ) assigned to gear unit  170 . 
     In the design in which at least 20 percent by volume of fan wheel  120  includes a metal having a density greater than or equal to 3.5 g/cm 3 , fan wheel  120  furthermore has a comparatively great inertia, thus making it possible to reduce vibrations and therefore increase a smooth running of handheld power tool  100 . Fan wheel  120  according to the present invention preferably increases a rotary inertia of drive motor  180  or of its rotor ( 314  in  FIG. 3 ) by preferably at least 5%, particularly preferably 10%, and ideally by more than 15% as compared to a fan wheel made of plastic. A lower reduction of a rotational speed of drive motor  180  may moreover be enabled in the case of short-term increase in load resistance. With the aid of above-described fan wheel  120 , the inertia of the drive train may also be increased. 
     Here, drive shaft  182  is preferably mounted in each case via a bearing element  122 ,  124  in tool housing  105  at an end  181  facing away from tool holder  140  and/or at an end  183  facing tool holder  140 . Drive shaft  182  is preferably rod-shaped. Drive shaft  182  is moreover preferably designed in the manner of a torsion shaft, a comparatively low load acting on a connection between fan wheel  120  and drive shaft  182 . Fan wheel  120  is preferably situated between the two bearing elements  122 ,  124 . Fan wheel  120  is, as demonstrated, situated between bearing element  122  and drive motor  180 . In this way, an improved device balance of handheld power tool  100  may preferably be facilitated, since the center of gravity of handheld power tool  100  is situated in handle area  115 . 
     However, fan wheel  120  may also be situated between drive motor  180  and optional gear unit  170 . Furthermore, several fan wheels  120  may be present, the fan wheels being potentially situated at different positions, for example between a bearing element  122  and drive motor  180  or between drive motor  180  and gear unit  170 . 
       FIG. 2  shows handheld power tool  100  from  FIG. 1  and illustrates the rotatable mounting of drive shaft  182  via bearing element  122  in tool housing  105 .  FIG. 2  furthermore illustrates a motor electronic system  215  assigned to drive motor  180  from  FIG. 1 . Motor electronic system  215  is situated between drive motor  180  and optional gear unit  170  by way of example, but it could also be situated at another arbitrary location, for example between fan wheel  120  and drive motor  180 .  FIG. 2  moreover shows an exemplary gear-shifting device  205  for changing a particular gear ratio of gear unit  170 . A main electronic system  299  of handheld power tool  100  is furthermore preferably situated in handle area  115  between switch  112  and rechargeable battery pack  117 . 
       FIG. 3  shows fan wheel  120 , drive motor  180 , spindle locking device  190  as well as drive spindle  130  from  FIG. 1  and  FIG. 2 . Here,  FIG. 3  illustrates drive motor  180  which is preferably designed as an electronically commutated drive motor and which includes a stator  312  and a rotor  314 . Motor electronic system  215  is preferably situated in the area of bearing element  124  [and] is, as demonstrated, screwed to the side surface of stator  312  facing bearing element  124 . 
       FIG. 3  moreover shows drive spindle  130  and spindle locking device  190 , spindle locking device  190  being, as demonstrated, situated between drive motor  180  and drive spindle  130 . At its axial end  361  on the drive side, i.e. at its end  361  facing drive motor  180 , drive spindle  130  has at least one, as demonstrated three, clamping surfaces  362  for interacting with spindle locking device  190 . It is pointed out that the design of clamping surfaces  362  at drive spindle  130  is only of exemplary nature and is not to be construed as a limitation to the present invention. Clamping surfaces  362  may also be designed as a separate component assigned to drive spindle  130 , for example, the separate component being coupleable to drive spindle  130 . 
     Spindle locking device  190  preferably includes at least one control element  321 , a clamping ring  340  as well as at least one, as demonstrated three, blocking members  350 . Control element  321  is, as demonstrated, designed in one piece with a planet carrier  320  assigned to gear unit  170  which is preferably designed as a planetary gear set. However, control element  321  may also be connected to gear unit  170  with the aid of any arbitrary connection, for example a clamping connection. In this case, control element  321  has, as demonstrated, three sections  322  as well as a recess  329 , a blocking member  350  being situatable between two sections  322 , which are adjacent in the circumferential direction of control element  321 , in each case. Recess  329  is preferably used to situate control element  321  on drive spindle  130 . 
     The demonstrated three blocking members  350  are preferably mounted in clamping ring  340 . Here, clamping ring  340  is preferably designed to prevent blocking members  350  from escaping from control element  321  in the radial direction of drive spindle  130 . Blocking members  350  are preferably clampable during the spindle locking mode of spindle locking device  190  between clamping ring  340  and a clamping surface  362  of drive spindle  130  which is assigned to particular blocking member  350 . Clamping surfaces  362  are preferably designed to prevent drive spindle  130  from twisting in relation to gear unit housing  175  and thus to tool housing  105  from  FIG. 1 . In this case, blocking members  350  preferably have a cylindrical design, but may also have any other shape, for example spherical. A spindle locking device  190  of this type is conventional so that a detailed description thereof is dispensed with for the sake of a concise description. The spindle locking mode of spindle locking device  190  preferably takes place when a torque, which is externally applied to tool holder  140  from  FIG. 1  and  FIG. 2 , is greater than a torque of planet carrier  320  on the drive side. An illustration of the gear unit assembly was also dispensed with for the sake of clarity. 
       FIG. 4  shows a cut-through  400  of handheld power tool  100  from  FIG. 1  in which an illustration of insertion tool  150  and tool holder  140  from  FIG. 1  was dispensed with for the sake of clarity and simplicity of the drawing. Cut-through  400  illustrates an exemplary embodiment of gear unit  170  designed as a planetary gear set, of spindle locking device  190  as well as of optional torque clutch  160  from  FIG. 1  and  FIG. 2 . 
     Planetary gear set  170  is preferably shiftable between a first and a second gear and has by way of example three gears or planetary stages: a front stage  470 , a central stage  471 , and a rear stage  472 . Central planetary stage  471  has by way of example a sun wheel  491  including at least one planet wheel  492 , a planet carrier  494  together with the sun wheel of next planetary stage  470 , as well as a ring gear  492 . Here, sun wheel  491  is preferably movable in the radial direction of gear unit  170  by at least 0.2 mm in relation to ring gear  492 . It is pointed out that the sun wheels of the two other planetary stages  470 ,  472  may also be radially movable. The torque of drive motor  180  is transferred to drive spindle  130  via planetary stages  472 ,  471 ,  470  with the aid of a rotary driving contour of planet carrier  320 . In this case, gear unit housing  175  has a bearing point  405  for supporting drive shaft  182  via bearing element  124 . Since the design of a planetary gear set is sufficiently known to those skilled in the art, a further description of planetary stages  470 ,  472  is dispensed with for the sake of a concise description. 
     Planetary stages  470 ,  471 ,  472  are situated by way of example in gear unit housing  175  which preferably has a two-part design and which is, as demonstrated, divided into a front section  410  (on the right-hand side in  FIG. 4 ) and a rear section  414  (on the left-hand side in  FIG. 4 ) which is fastened to the front section. In rear section  414 , planetary stages  471 ,  472  are situated as demonstrated. In the outer periphery of front section  410 , a male thread  482  is formed as demonstrated, at which a torque adjusting sleeve  495  which is assigned to optional torque clutch  160  and which is coupled to a circular limiting transfer element  479  on which spring pressure is applied by a plurality of helical compression springs  481  is rotatably mounted by way of example. Since the design of a torque clutch is sufficiently known to those skilled in the art, a further description is dispensed with for the sake of a concise description. 
       FIG. 4  furthermore illustrates spindle locking device  190  from  FIG. 3  in the spindle locking mode. Here, the demonstrated one blocking member  350  is situated at a clamping surface  362  of drive spindle  130 , clamping ring  340  preventing blocking member  350  from escaping from control element  321  in the radial direction of drive spindle  130 . In this case, clamping surface  362  prevents drive spindle  130  from twisting in relation to gear unit housing  175  and thus to tool housing  105  from  FIG. 1 . 
       FIG. 5  shows an exemplary arrangement of fan wheel  120  on drive shaft  182  of drive motor  180 . Fan wheel  120  has, as demonstrated, a two-part design including a flange  524  for forming a force-locked connection to drive shaft  182  and an air guide member  522 . Flange  524  and air guide member  522  are preferably connected to one another via any arbitrary connection  527 , for example a force-locked or a form-fit connection, such as a press-fit connection. Air guide member  522  is preferably a disk, a plurality of air guide vanes  532 ,  534  being preferably situated on a side  521  facing drive motor  180 . Two of the air guide vanes are characterized by a reference numeral  532  and  534 , respectively, by way of example. Here, flange  524  and air guide member  522  may preferably include different materials, for example a composite material which includes at least plastic or two different metals. In this case, at least 20 percent by volume of fan wheel  120  includes a metal having a density greater than or equal to 3.5 g/cm 3  as described above. Air guide member  522  preferably includes a zinc alloy and flange  524  is preferably designed as a steel bushing. 
     Moreover, fan wheel  120  may also be designed as a single piece. Fan wheel  120  is preferably designed as a hybrid fan which is preferably designed to take in air in the axial direction of fan wheel  120  or along an air flow direction  504  and to release it in the radial direction of fan wheel  120  or along an air flow direction  502  and/or in the axial direction of fan wheel  120  or along an air flow direction  506 . However, fan wheel  120  may also be designed as a radial fan or as a diagonal fan. 
     Moreover,  FIG. 5  illustrates drive motor  180  from  FIG. 1 , which is preferably designed as an electronically commutated drive motor, including rotor  314  which preferably has a laminated armature core preferably made of sheet steel and/or is provided with at least one permanent magnet  512 . The at least one permanent magnet  512  is preferably rod-shaped and/or preferably includes rare earth elements. Furthermore, a spacer element  514 ,  513 ,  515  is situated in each case by way of example for secure positioning on drive shaft  182  between bearing element  122  and fan wheel  120 , between fan wheel  120  and drive motor  180  as well as between drive motor  180  and bearing element  124 .