Abstract:
A drywall screwdriver includes a housing, an element delimiting the depth of engagement, a drive unit, an outlet spindle, and a planetary gear that comprises at least one hollow wheel. The drywall screwdriver further comprises at least one support element that is different from a housing element and that at least partially surrounds the ring gear of the planetary gear.

Description:
This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2012/060331, filed on Jun. 1, 2012, which claims the benefit of priority to Serial No. DE 10 2011 078 385.7, filed on Jun. 30, 2011 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     Drywall screwdrivers comprising a housing, comprising a screw-in depth limiting element, comprising a drive unit, comprising an output spindle and comprising a planetary gear unit, which latter has at least one ring gear, are already known. 
     SUMMARY 
     The disclosure is based on a drywall screwdriver comprising a housing, comprising a screw-in depth limiting element, comprising a drive unit, comprising an output spindle and comprising a planetary gearing, which latter has at least one ring gear. 
     It is proposed that the drywall screwdriver has at least one support element, which differs from a housing element and which at least partially embraces the ring gear of the planetary gearing. By a “drywall screwdriver” should in this context be understood, in particular, a portable machine tool which is designed to machine materials, such as, for example, plasterboard, and preferably to screw screws into materials such as, for example, plasterboard. By “designed” should be understood, in particular, specially configured, arranged and/or equipped. By a “screw-in depth limiting element” should in this context be understood, in particular, an element which is at least substantially designed to limit a screw-in depth of the drywall screwdriver. In a particularly preferred embodiment, the screw-in depth limiting element has a depth stop. Preferably, a screw-in depth of the screw-in depth limiting element can be made adjustable. Other limit parameters which appear sensible to a person skilled in the art, such as, for example, a rotation speed or a torque, are also, however, conceivable. The screw-in depth limiting element can be of electronic, magnetic, optical or other configuration which appears sensible to a person skilled in the art. In a particularly preferred illustrative embodiment, the screw-in depth limiting element is of mechanical configuration. Furthermore, by a “drive unit” should be understood, in particular, an electrical and/or mechanical motor unit, which is designed, during operation, advantageously to generate a rotary motion. By this should advantageously be understood, in particular, an electric motor. By a “planetary gearing” should be understood, in particular, a unit which is designed to transform an incoming torque into an outgoing differing torque and/or an input rotation speed into a differing output rotation speed. The planetary gearing preferably comprises at least two, preferably three planet gears, as well as at least one sun gear or pinion. Moreover, the planetary gearing preferably comprises a planet carrier element on which at least two, preferably three planet gears are rotatably arranged. Preferably, the planet gears are arranged by means of bolts on the planet carrier element. Furthermore, the planetary gearing preferably has at least one ring gear. By a “support element” should be understood, in particular, an element constructed separate from the housing, which element is designed to absorb and/or divert forces from at least one direction. Preferably, the support element is designed to support axial forces. 
     As a result of the disclosed configuration, forces can advantageously be transmitted and/or diverted without, by additional support forces, restricting the ring gear in its motional play. In addition, a small loading and long working life of the planetary gearing can thereby be achieved. 
     It is further proposed that the support element accommodates the ring gear of the planetary gearing with a radial and/or axial play. Hence an automatic centering of the planetary gearing can advantageously be achieved. Furthermore, a simple assembly can be realized. 
     In addition, it is proposed that the ring gear of the planetary gearing has in an axial direction at least one projection. The projection can have various cross sections which appear sensible to the person skilled in the art, though, particularly advantageously, the projection has at least one rectangular cross-sectional area. In addition, it would also be conceivable for the ring gear of the planetary gearing to have in a radial direction at least one projection. A shape of the ring gear which forms at least one reference element to enable simple assembly can hence be configured in a constructively simple manner. In addition, a form closure, at least in the radial and in the peripheral direction, can advantageously be realized with another element. 
     It is further proposed that the support element has a collar extending at least partially radially inward and having at least one recess. Hence an axially large surface area of the support element can particularly advantageously be provided, whereby an advantageous supporting of a component against the support element is enabled. 
     It is further proposed that the at least one projection of the ring gear reaches through the at least one recess of the collar of the support element, into a recess of the housing. Hence a skewing of the ring gear and a skewing of the support element relative to the housing can reliably be prevented. Furthermore, a simple assembly of the components can be realized. 
     In addition, it is proposed that the planetary gearing has at least one bearing unit, which is at least partially axially supported against the collar of the support element. By a “bearing unit” should be understood, in particular, a unit which at least in one direction can absorb supporting forces and, moreover, enables a relative motion between two components with low friction losses. By this should advantageously be understood, in particular, a slide bearing and/or, particularly advantageously, a roller bearing. Other bearing units which appear sensible to the person skilled in the art are also, however, conceivable. The slide bearing here advantageously has a material pairing on a sliding surface, which material pairing, at least on the sliding surface, has a friction coefficient which is less than a friction coefficient obtained with a material pairing between a material of the planet carrier element and a material of the housing. Hence axial forces of the output spindle and of the planetary gearing can advantageously be transmitted to the support element. 
     It is further proposed that the housing comprises at least one gear casing and at least one motor casing. A simple two-part assembly can thereby be realized particularly advantageously. Moreover, the individual housing parts can be tailored to their particular requirements. 
     In addition, it is proposed that the support element is accommodated at its outer diameter in a play-free manner in the at least one gear casing and the at least one motor casing. A simple installation of the support element can hence advantageously be realized. In addition, a connection between the gearing and the motor casing can advantageously be realized, whereby forces can be conducted to the motor casing. 
     It is further proposed that the drywall screwdriver has at least one cover plate, which is disposed in the motor casing and against which the ring gear and the support element are at least partially axially supported. An axial force transmission from the ring gear and the support element to the motor casing can hence be realized particularly advantageously. In addition, an end closure for the gearing can be formed in a constructively simple manner by the cover plate. 
     It is further proposed that the support element connects the gear casing and the motor casing in the manner of a socket. By “connects in the manner of a socket” should in this context be understood, in particular, a connection between two preferably tube-like components by means of an element that bears against at least one outer and/or inner face of both components. Preferably the element has an outer and/or inner diameter corresponding to the inner and/or outer diameters of the components. Particularly preferably, the element is disposed in a connecting region of the components and is designed to align the axes of the components with respect to each other. Hence an accurate and reliable mutual alignment of the gear casing and motor casing can advantageously be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages derive from the following drawing description. In the drawings, illustrative embodiments of the disclosure are represented. The drawings, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also view the features individually and combine them into sensible further combinations. 
         FIG. 1  shows a partial detail of a drywall screwdriver according to the disclosure in a side view, 
         FIG. 2  shows a planet carrier element of the drywall screwdriver according to the disclosure in a schematic representation, and 
         FIG. 3  shows a gear casing, a support element, a ring gear and a cover plate of the drywall screwdriver according to the disclosure in a schematic exploded representation. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a partial detail of a drywall screwdriver according to the disclosure is represented in a side view. The drywall screwdriver has a housing  10 . The housing  10  comprises a gear casing  56  and a motor casing  58 . The gear casing  56  is produced in pot construction. The motor casing  58  is produced in shell construction. The drywall screwdriver additionally has a screw-in depth limiting element  12 , a gear unit  14 , an output spindle  16 , a drive unit  18  and a clutch unit  20 . The drive unit  18  is configured as a direct-current motor. 
     At one end of the gear casing  56 , which end, viewed in an axial direction  62  of the gear casing  56 , is facing away from the motor casing  58 , is disposed the screw-in depth limiting element  12 . The screw-in depth limiting element  12  is connected by means of a plug connection detachably to the housing  10  of the drywall screwdriver. The screw-in depth limiting element  12  comprises an adjusting sleeve  66 . The screw-in depth limiting element  12  also comprises a depth stop  68 . The depth stop  68  is designed to limit a screw-in depth of a screw in a screw-in operation. The adjusting sleeve  66  is designed to adjust the screw-in depth. The screw-in depth is here adjusted manually by means of the adjusting sleeve  66 . To this end, an operator turns the adjusting sleeve  66  about an axis corresponding to an axis  38  of the output spindle  16 . When the adjusting sleeve  66  is turned by the operator, the depth stop  68  is moved along the axial direction  62 . 
     The adjusting sleeve  66  has an internal thread  70 . The internal thread  70  extends over a section of an inner face of the adjusting sleeve  66 . The depth stop  68  has an external thread  72 . The external thread  72  extends over a section of an outer face of the depth stop  68 . In an assembled state of the screw-in depth limiting element  12 , the external thread  72  of the depth stop  68  and the internal thread  70  of the adjusting sleeve  66  engage in each other. In the radial direction  74 , viewed from outside to inside, a spring element  76  is disposed in front of the depth stop  68 . The spring element  76  presses the depth stop  68  inward in the radial direction  74 . The spring element  76  is disposed in a radially inner depression  78  of the adjusting sleeve  66 . The radially inner depression  78  is disposed at one end of the adjusting sleeve  66 , which end, in the axial direction  62 , is facing toward the depth stop  68 . The radially inner depression  78  secures the spring element  76  in the axial direction  62 . The spring element  76  presses flanks of the external thread  72  of the depth stop  68  in the radial direction  74  against flanks of the internal thread  70  of the adjusting sleeve  66  in a region which lies opposite the spring element  76  in the radial direction  74 . A friction is thereby generated between the flanks of the internal thread  70  and of the external thread  72 . As a result of this friction, an automatic adjustment of the depth stop  68  can be reliably prevented. Moreover, the screw-in depth limiting element  12  has latching elements (not represented), which are designed to divide the rotation of the adjusting sleeve  66  into individual latching steps. As a result of the latching elements, an automatic adjustment of the depth stop  68  can further be reliably prevented. 
     The adjusting sleeve  66  has a grip region  80 , which is disposed on an outer side of the adjusting sleeve  66 . The grip region  80  has lamellar elevations  82 . The grip region  80  is designed to increase the grip of the outer side of the adjusting sleeve  66  and thereby make it easier for the operator to turn the adjusting sleeve  66 . 
     The depth stop  68  has a stop face  84 , which, once that screw-in depth of the screw which has been set by the operator is reached, bears upon a surface of a machined workpiece. The stop face  84  has an annular cross section. 
     The drywall screwdriver has to a tool receiving fixture  86 . The tool receiving fixture  86  is formed by a bit holder. The tool receiving fixture  86  has a magnetic element  88  for holding an insert tool (not represented) captively in the tool receiving fixture. 
     The tool receiving fixture  86  has a receiving region  90 . The receiving region  90  is designed to receive the insert tool. The receiving region  90  has a hexagon socket contour (not represented in detail). In an inserted state, the insert tool is held in a rotationally secure manner in the receiving region  90  of the tool receiving fixture  86 . 
     The output spindle  16  is connected in a rotationally secure manner to the tool receiving fixture  86 . The tool receiving fixture  86  is connected in a rotationally secure manner to the insert tool inserted therein and transmits the kinetic energy to the insert tool. 
     Via the gear unit  14  and the clutch unit  20 , a kinetic energy of the drive unit  18  is transmitted in a screw-in operation to the output spindle  16  and thus to the tool receiving fixture  86 . The clutch unit  20  is designed to couple and/or decouple a torque transmission of the gear unit  14  to the output spindle  16 . A gear element  22  of the gear unit  14  is fixedly connected to a coupling element  24  of the clutch unit  20 . The gear element  22  of the gear unit  14  is configured in one piece with the coupling element  24  of the clutch unit  20 . The gear unit  14  comprises a planetary gearing  26 . The planetary gearing  26  of the gear unit  14  is of single-step configuration. The gear unit  14  has a transmission ratio between 3 and 10. 
     The coupling element  24  comprises three driving elements  30 ,  32 ,  34 . The driving elements  30 ,  32 ,  34  are configured in one piece with the planet carrier element  28  of the planetary gearing  26 . 
     The drive unit  18  comprises a motor spindle  92 . In an operating state, the drive unit  18  generates a rotary motion of the motor spindle  92 . On the motor spindle  92  is disposed a gearwheel. The gearwheel forms a sun gear  94  of the planetary gearing  26  of the gear unit  14 . In an operating state, the sun gear  94  of the planetary gearing  26  meshes with planet gears  96  of the planetary gearing  26 . In an operating state, the planet gears  96  rotate respectively about a rotational axis  98  of the planet gears  96 . Moreover, the planet gears  96  rotate about a rotational axis of the sun gear  94 , which rotational axis corresponds to an axis  42  of the gear unit  14 . The axis  42  of the gear unit  14  corresponds to an axis  40  of the drive unit  18 . The axis  38  of the output spindle  16  corresponds to the axis  40  of the drive unit  18 . The rotational axis of the motor spindle  92  corresponds to the axis  40  of the drive unit  18 . 
     The planetary gearing  26  has a ring gear  46 . In an operating state, the planet gears  96  mesh with the ring gear  46  of the planetary gearing  26 . The ring gear  46  of the planetary gearing  26  is disposed, in a rotationally secure manner relative to the housing  10  of the drywall screwdriver, in the gear casing  56  of the drywall screwdriver. The drywall screwdriver has a support element  44  which differs from a housing element and which embraces the ring gear  46  of the planetary gearing  26 . The support element  44  is disposed between the ring gear  46  and the housing  10 . The support element  44  is accommodated at its outer diameter in a play-free manner in the gear casing  56  and the motor casing  58 . The support element  44  connects the gear casing  56  and the motor casing  58  in the manner of a socket. The support element  44  is formed by a connecting sleeve. The connecting sleeve is formed by a sheet metal bush. The support element  44  embraces the ring gear  46  of the planetary gearing  26  with a radial and axial play. The ring gear  46  of the planetary gearing  26  has in the axial direction  62  at least one projection  48 . The projections  48  are formed-on on a side of the ring gear  46  that is facing toward the screw-in depth limiting element  12 . The support element has a collar  50  extending at least partially radially inward and having at least one recess  52 . The collar  50  extends inward on a plane running orthogonally to the axial direction. In addition, the collar  50  has eight recesses  52 . The projections  48  of the ring gear  46  reach through the recesses  52  of the collar  50  of the support element  44  into eight recesses  54  of the gear casing  56 , whereby the ring gear  46  is fixed in the peripheral direction (see  FIG. 3 ). 
     The planet carrier element  28  is supported directly in the housing by means of a bearing unit  36 . The bearing unit  36  is press-fitted on a radial outer face of the planet carrier element  28 . The bearing unit  36  is formed by a roller bearing  102 . The bearing unit  36  is supported with its outer periphery directly against an inner face of the gear casing  56 . The bearing unit  36  has an axial motional play in relation to the inner face of the gear casing  56 . The bearing unit  36  is partially axially supported against the collar  50  of the support element  44 . In the axial direction  62 , the bearing unit  36 , on a side facing toward the screw-in depth limiting element  12 , is supported against the gear casing  56 . On a side which, viewed in the axial direction  62 , is facing away from the screw-in depth limiting element, the bearing unit  36  is supported against the collar  50  of the support element  44 . In the case of a force acting axially on the output spindle  16 , the force can be relayed via the clutch unit  20  to the planet carrier element  28 . From the planet carrier element  28 , the axial force can be relayed by means of an active pressing to the bearing unit  36 . The bearing unit  36  is supported in the axial direction  62  against the collar  50  of the support element  44 , whereby an axial force is relayed to the support element  44 . The support element  44  is axially supported against a cover plate  60 . The cover plate  60  is disposed in the motor casing  58 . The cover plate  60  is held radially and axially in the motor casing  58  via a circumferential groove encircling the motor casing  58 . An axial force can hence be diverted from the support element  44 , via the cover plate  60 , to the motor casing  58 . Accordingly, a force acting axially on the output spindle  16  can be diverted to the motor casing  58 . At least partially axially supported against the cover plate  60  are the ring gear  46  and the support element  44 . The ring gear  46  and the support element  44  are axially supported against the cover plate  60  on a side which, viewed in the axial direction  62 , is facing away from the screw-in depth limiting element. 
     On a side facing toward the drive unit  18 , the planet carrier element  28  has three recesses  104 ,  106 ,  108 . Through the three recesses  104 ,  106 ,  108 , three bolts  110  are guided. In turn, the three planet gears  96  are mounted on the three bolts  110 . In addition, the planet carrier element  28  has a recess  112 , which runs axially to the axis  38  of the output spindle  16 . The output spindle  16  is mounted and/or guided partially in the gear element  22  of the gear unit  14 . The output spindle  16  is partially mounted and guided in the planet carrier element  28  of the planetary gearing  26 . In the recess  112 , the output spindle  16  is guided in an axially movable manner. The planet carrier element  28  is designed to transmit the rotary motion of the planet gears  96  about the rotational axis of the sun gear  94  to the clutch unit  20 . 
     On a side of the planet carrier element  28  that is facing toward the screw-in depth limiting element  12 , a collar  114  is arranged around the recess  112 . Radially spaced around the collar  114 , the three driving elements  30 ,  32 ,  34  of the first coupling element  24  are formed onto the planet carrier element  28 . The driving elements  30 ,  32 ,  34  have on their faces facing in the peripheral direction end ramps  116  (see  FIG. 2 ). The clutch unit  20  has, in addition to the first coupling element  24 , a second coupling element  118  and a third coupling element  120 . The second coupling element  118  has both on a side facing toward the first coupling element  24  driving elements  122 , and on a side facing away from the first coupling element  24  driving elements  124 . On a side facing toward the second coupling element  118 , the third coupling element  120  has driving elements  126 . The driving elements  30 ,  32 ,  34 ,  122 ,  124 ,  126  project respectively in the axial direction. In an operating state, the first coupling element  24  is rotationally driven by the planet carrier element  28  directly from the gear unit  14 . The second coupling element  118  is seated on the collar  114  of the planet carrier element  28  such that it is movable axially and in the peripheral direction, and is engaged with the first coupling element  24 . The third coupling element  120  is fixedly connected to the output spindle  16 . 
     Between the second coupling element  118  and the third coupling element  120  is disposed, in the axial direction  62 , a spring element  128 . The spring element  128  is configured as a helical spring. The spring element  128  is designed to keep the second coupling element  118  and the third coupling element  120 , in a non-actuated state (as represented in  FIG. 1 ), disengaged. To this end, the spring element  128  forces the second coupling element  118  and the third coupling element  120  apart in the axial direction  62 . 
     In an actuated state, the operator presses the drywall screwdriver in the axial direction  62  against a workpiece. As a result of the force which an operator applies to the drywall screwdriver in a screw-in operation, the third coupling element  120  moves toward the second coupling element  118  counter to a spring force of the spring element  128 . If a contact arises between the second coupling element  118  and the third coupling element  120 , the second coupling element  118  is braked in relation to the first coupling element  24 . The second coupling element  118  is thereby pushed onto the end ramps  116  of the first coupling element  24  and moved against the third coupling element  120 , whereby coupling is aided. 
     The driving elements  30 ,  32 ,  34 ,  122 ,  124 ,  126  of the first coupling element  24 , of the second coupling element  118  and of the third coupling element  120  are designed to, in an actuated state, bear one against another in a peripheral direction of the rotary motion of the gear unit  14 . The driving elements  30 ,  32 ,  34  of the first coupling element  24  here transmit the rotary motion of the gear unit  14  to the driving elements  122  of the second coupling element  118  and thus to the second coupling element  118 . The driving elements  124  of the second coupling element  118  transmit the rotary motion of the gear unit  14  to the driving elements  126  of the third coupling element  120  and thus to the third coupling element  120 . 
     Once the operator-set screw-in depth of a screw is reached, the stop face  84  of the depth stop  68  bears upon a surface of the workpiece. In this state, the force in the axial direction  62  which the operator applies to the drywall screwdriver is transmitted via the depth stop  68  to the workpiece, instead of to an insert tool. This causes the third coupling element  120 , which is subjected to load by the spring element  128 , to disengage from the second coupling element  118 , so that the rotary motion of the gear unit  14  is no longer transmitted to the third coupling element  120 , or to an insert tool.