Patent Publication Number: US-11648657-B2

Title: Handheld power tool

Description:
This application claims priority under 35 U.S.C. § 119 to patent application number DE 10 2017 218 668.2, filed on Oct. 19, 2017 in Germany, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The disclosure relates to a handheld power tool. 
     DE 2752979 discloses a transmission for an electric angle tool, in particular an angle grinder, for connecting the output shaft of the motor to the delivery shaft, arranged perpendicularly with respect to said output shaft, by means of gear wheels, in particular bevel gears, of which at least in each case one is fastened to each shaft. One of the gear wheels is fixed on the shaft against axial movements by means of a holder arrangement. This holding arrangement is held by means of a Seeger ring which is pressed into a groove in the shaft. 
     SUMMARY 
     The disclosure is based on the object of improving a handheld power tool, in particular an angle grinder, using simple structural measures. 
     The object is achieved by a handheld power tool, in particular an angle grinder, comprising a drive unit for transmitting a movement to an output shaft which can be releasably connected to an insert tool, comprising a securing ring and comprising a securing element for securing the securing ring. 
     According to the disclosure, the securing element has a recess which is provided to surround the securing ring in the radial direction in at least one operating state. 
     Owing to the growing number of insert tools and, respectively, accessories for handheld power tools, increasingly higher torques, rotation forces and axial forces which act on the handheld power tools and in particular on the output shafts can also be observed. 
     Owing to the disclosure, the functional reliability of the handheld power tool is intended to now be increased by a securing ring holding the output shaft in or on the handheld power tool. Furthermore, the available installation space is intended to be used in a more optimal manner. 
     Furthermore, improved and, respectively, automated assembly can be achieved owing to the disclosure. 
     In this context, a “drive unit” is intended be understood to mean, in particular, a unit which is provided to generate at least one drive torque and to pass on said drive torque, in particular, to an insert tool. The handheld power tool advantageously has a drive unit. The drive unit particularly advantageously has at least one electric motor. The drive unit is preferably provided to drive and/or to move at least one insert tool, for example a drill and/or a tool bit and/or a cutting blade and/or a grinding disc and/or a scissor blade or the like, and/or at least the output shaft or a tool receptacle device, for example a chuck and/or a saw blade receptacle and/or a bit holder or the like, of the handheld power tool. 
     In this case, the output shaft can be connected directly or indirectly to the insert tool. In the case of indirect connection of the output shaft to the insert tool, a tool receptacle device can be provided for example, which tool receptacle device receives the insert tool. In the case of direct connection of the output shaft to the insert tool, the output shaft can have, for example, a thread or a connecting means which is provided to receive an insert tool in some other way and releasably connects the insert tool to the handheld work machine. 
     The securing ring is intended to be provided, in particular, to be fitted onto the output shaft in order to limit an axial movement of components, such as a transmission gear element and/or a bearing element for example, in an interlocking and/or force-fitting manner. The securing ring can be formed from a spring steel. The securing ring can be phosphatized. The securing ring can be lubricated. The securing ring can be designed in accordance with DIN 471. The securing ring can be of c-shaped design. 
     The recess of the securing element can extend in the circumferential direction around a rotation axis of the output shaft. 
     The securing element can be designed part of a component which is fitted onto the output shaft. In particular, the securing element can extend along the output axis of the output shaft in the axial direction and surround the securing ring at least in sections. The securing element can surround the securing ring in the circumferential direction around the output axis through 360°. 
     The output axis is understood to mean a geometric axis and is intended to form, in particular, a rotation axis of the output shaft. 
     The recess of the securing element can be introduced into a component. The recess can have a maximum radial extent in the radial direction of the output axis, which maximum radial extent is greater, in particular at least by up to 5%, preferably at least by up to 10%, preferably at least by up to 15%, further preferably at least by up to 20%, particularly preferably at least by up to 30%, and/or in particular at most by up to 40%, preferably at most by up to 35%, than a radial extent of a section of the output shaft, which section is surrounded by the recess of the securing element and/or of the securing ring in at least one operating state. The securing element can have a recess surface which delimits the recess in the radial direction of the output axis. The recess surface can be formed substantially concentrically about the output axis in relation to the output shaft. The recess surface can have an axial extent along the output axis, which axial extent is equal to or greater than an axial extent of the securing ring. 
     The dependent claims specify further expedient developments of the handheld power tool according to the disclosure. 
     It may be expedient that the recess delimits the securing element at least partially in the radial and/or in the axial direction of the output axis. As a result, the securing ring can be surrounded in a particularly advantageous manner and the functional reliability of the system can be improved. In particular, the securing element can protect the securing ring against damage. 
     It may further be expedient that the output shaft has a securing groove, which encircles the output shaft, for receiving the securing ring. The securing groove can be designed as an, in particular partial, tapered portion of a diameter of the output shaft. The securing groove can be designed as a securing notch which is provided to receive the securing ring and in particular to receive said securing ring in an interlocking and/or force-fitting manner in the axial direction along the output axis. The recess can be provided to surround the securing groove in the radial direction in at least one operating state. As a result, the securing groove can be particularly reliably protected against damage. 
     Furthermore, it may be expedient that the securing groove has a bent contour. The contour can be of concave design. The contour can be designed as an indentation in the output shaft. As a result, a notching effect of the output shaft can be minimized. In an alternative embodiment, the securing groove can have an angular contour. 
     Furthermore, it may be expedient that the securing element and the securing groove form a securing apparatus which is provided to secure the securing ring against independently coming loose in at least one operating state. The securing apparatus comprises the recess with a maximum radius which is smaller than a maximum radius of the securing ring in a state fitted on the output shaft which is not situated in the securing groove. In particular, the recess can surround the securing ring in at least one operating state in such a way that the securing ring is prevented from independently coming loose in the radial direction. The recess can have a maximum radius which is greater than a maximum radius of the securing ring in a state inserted in the securing groove. In other words, the maximum radius of the recess in a section of the output shaft adjacent to the securing groove can be smaller than a radius of the output shaft and the material thickness of the securing ring, so that the securing ring does not independently come loose from the securing groove in an operating state surrounded by the recess. The recess surface of the recess can form a distance from the output shaft, which distance is smaller than a material thickness of the securing ring. As a result, it is particularly advantageously possible to prevent the securing ring from jumping out or slipping out during operation of the handheld power tool. In addition, mounting of the securing ring can be facilitated in a particularly advantageous manner by the securing ring being pushed into an end position in the axial direction over the output shaft by means of the transmission gear element, in order to preferably snap into the securing groove. 
     The handheld power tool can have a transmission element. The transmission element can be designed as a crown gear element. 
     It is proposed that the handheld power tool has a bearing element, in particular a roller bearing element, which is provided to support the output shaft, wherein the bearing element is provided to make contact with a transmission gear element or a brake element in the axial direction in at least one operating state. As a result, the transmission gear element can particularly advantageously make contact with the bearing element by the transmission gear element forming a supporting region, in particular a supporting point, a supporting line and/or a supporting surface, in relation to the bearing element, which supporting region is at a distance from the output shaft in the radial direction. Therefore, the supporting region of a transmission element or of a brake element is displaced further radially outward in order to reduce a bending moment, which acts on the output shaft, as a result. Greater bending stiffness of the output shaft can be achieved in this way. 
     The brake element can be part of a run-down brake, such as an eddy current brake for example, which is arranged between the transmission gear element and the bearing element. The brake element can be connected, in particular in an interlocking manner, to the transmission gear element in a rotationally fixed fashion. The eddy current brake can be designed as a conventional eddy current brake which is known to a person skilled in the art and can be found in the prior art. 
     It may be expedient that the securing element is designed as a/the transmission gear element or a/the brake element and is formed, in particular, by the transmission gear element or the brake element. In particular, a/the transmission gear element and/or a/the brake element and/or a/the bearing element can be connected to the output shaft by means of an interference fit. A particularly reliable force-fitting connection to the output shaft can be formed in this way. 
     It is further proposed that the output shaft has a first contact region, in particular a first active surface for a/the bearing element of the drive shaft, and a second contact region, in particular a second active surface for a/the transmission gear element or a/the brake element, wherein the securing groove separates the first contact region from the second contact region. The first and, respectively, the second contact region can be provided, in particular, to serve as active surfaces of the roller bearing element or of the transmission gear element. The first and/or the second contact region can be connected to the associated bearing element or to the associated transmission gear element or brake element by means of an interference fit, so that a force-fitting connection is produced between the output shaft and the roller bearing element or the transmission gear element. 
     It is further proposed that a/the transmission gear element and/or a/the brake element and a/the bearing element are surrounded by a machine housing. 
     The securing ring can be formed from a wire. The securing ring can have a constant cross section. The securing ring can be bent around the output axis. The securing ring can have a tensioned and an untensioned state. In the untensioned state, the securing ring can be bent, in particular can be bent in a c shape, in such a way that a radius of the securing ring is smaller than a radius of the output shaft, and/or that a radius of the securing ring is equal to or smaller than a radius of the securing groove of the output shaft. In the tensioned state, the securing ring can have a larger radius than in an untensioned state. In the tensioned state, the securing ring can be fitted onto the output shaft. In the tensioned state, the securing ring, in a state mounted on the output shaft, can have a clamping force which is directed in the radial direction of the output axis. 
     Furthermore, it is proposed that the securing ring is designed as a circlip. 
     The disclosure further relates to a securing ring which is designed as a circlip. The securing ring, in particular the circlip, can have a round cross section, such as a circular or an oval or a teardrop-shaped cross section for example. The securing ring, in particular the circlip, can have an angular cross section, such as a square or a rectangular cross section for example. The circlip can be embodied as a round wire circlip. The circlip can have an inside diameter of precisely 10.8 mm, approximately to a manufacturing tolerance. The circlip can be designed in accordance with DIN 7993. The circlip can be of c-shaped design. The circlip can be designed as a segment of a ring. As a result, an installation space in the handheld power tool can be optimized in a particularly simple manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages can be gathered from the following description of the drawing. The drawing illustrates exemplary embodiments of the disclosure. The drawings, the description and the claims contain numerous features in combination. A person skilled in the art will expediently also look at the features individually and combine them to form useful further combinations. In the drawing: 
         FIG.  1    shows a view of an exemplary handheld power tool  13 , 
         FIG.  2    shows a section through a transmission housing of the handheld power tool  13 , 
         FIGS.  3   a  to  3   b    show two perspective views of an output shaft, 
         FIGS.  4   a  to  4   b    show two sections through a transmission element and a brake element, 
         FIG.  5    shows a section through the output shaft from  FIG.  3   , 
         FIG.  6    shows an enlarged view of the output shaft, and 
         FIG.  7   a  to  e    show several embodiments of securing rings. 
     
    
    
     DETAILED DESCRIPTION 
     Identical components are provided with the same reference symbols in the following figures. 
       FIG.  1    shows a handheld power tool  13   13 , which is designed as an angle grinder  13 , comprising a housing  15 , comprising an additional handle  17  which is arranged on the housing  15 , comprising a cutting disk  19  and comprising a protective hood  21  which surrounds the cutting disk  19  at least in sections. 
     The cutting disk  19  is designed to cut and/or grind workpieces. The cutting disk  19  can be used universally and is suitable, in particular, for processing workpieces which are composed of cellulose, such as grass, scrub or roots, wood, plastic or a composite for example. However, as an alternative, the cutting disk  19  may also be suitable for processing metal, stone or a composite for example. 
     The protective hood  21  is intended to be releasably held on rotationally driven commercially available angle grinders  13 . The protective hood  21  can be held in a holding apparatus  23 , which is already known to a person skilled in the art and is designed to hold the protective hood  21 , of a power tool, preferably a handheld power tool  13 , with a rotational and/or translatory movement towards a workpiece which is to be processed. 
     A suitable power tool is a non-stationary handheld power tool  13 , such as, for example, an angle grinder  13  or a handheld circular saw according to the application DE 3740200 A1 or such as, for example, a backpack-type brush cutter according to the application DE 19616764 A1. 
     The housing  15  is designed as a machine housing  25  and comprises a transmission housing  27 , which at least partially surrounds a transmission (not shown), in particular an angular transmission, and at least one handle housing  29 , which accommodates a drive unit (not shown) at least in sections or at least surrounds said drive unit. The protective hood  21  is expediently intended to cover at least or up to 180° of the cutting disk  19  in order to protect the operator of the angle grinder  13  against flying sparks. 
     The handheld power tool  13  has a drive unit, not shown, for transmitting a rotational movement U to an output shaft  31  which can be releasably connected to an insert tool  19 . The rotational movement U is transmitted from the drive unit to the output shaft  31  by means of a transmission  33  which is designed as an angular transmission  33 . 
     The drive unit has an electric motor. The electric motor can be designed as an electrically commutated motor. 
     The handheld power tool  13  further has a securing ring  35  which is provided to secure components, such as a transmission gear element  37  and/or a bearing element  39  for example, against axial movement along an output axis a of the output shaft  31 . In the present case, the securing ring  35  is intended to minimize and/or delimit the bearing element  39  and a brake element  41  ( FIG.  3   a   ) or the transmission gear element  37  ( FIG.  3   b   ) an axial movement along the output axis a. 
     The bearing element  39  is designed as a roller bearing element  39  which is configured in the form of a conventional ball bearing. The ball bearing  39  has an inner bearing ring  41   a  and an outer bearing ring  41   b  which surrounds the inner bearing ring  41   a . The outer bearing ring  41   b  is mounted on the inner bearing ring  41   a  by means of balls  41   c  ( FIG.  3   ). In an alternative embodiment, any other roller bearing arrangement which appears to be expedient to a person skilled in the art or a sliding bearing arrangement or the like can also be used. 
     The angular transmission  33  has a crown gear element  37  which forms an interference fit in relation to the output shaft  31  and is pressed onto the output shaft  31 . The crown gear element  37  has a helical gearing, so that the crown gear element  37  meshes with a bevel gear element  43  which extends along a longitudinal extent L of the handheld power tool  13  and is directly or indirectly coupled to the drive shaft  45  ( FIG.  2   ). In an alternative embodiment, other angular transmissions  33 , such as worm gear transmissions or spur gear transmissions for example, also come into consideration. 
     The drive shaft  45  is preferably integrally formed with a drive shaft  45  of the drive unit. 
     The handheld power tool  13  further has a securing element  47  with a recess  49  for securing the securing ring  35 . The recess  49  is provided to surround the securing ring  35  in the radial direction in at least one operating state. 
     The output shaft  31  is be directly connected to the insert tool  19 . The output shaft  31  protrudes out of the transmission housing  27  and has a receiving end  51  with a receiving thread  53 . The receiving end  51  of the output shaft  31  is provided to detachably receive an insert tool  19  and to be releasably connected to the output shaft  31  by means of a nut (not shown) and the receiving thread  53 . As a result, the insert tool  19  can be releasably connected to the handheld power tool  13 . 
     The securing ring  35  is provided to be fitted onto the output shaft  31  in order to limit an axial movement of components, such as a transmission gear element  37  and/or a bearing element  39  for example, in an interlocking and force-fitting manner. The securing ring  35  is formed from a spring steel. The securing ring  35  is phosphatized. The securing ring  35  is lubricated. The securing ring  35  is designed as a circlip  35 . The circlip  35  has a circular cross section Q (bottom of  FIG.  7   a   ). In an alternative embodiment, the circlip  35  can have an angular cross section Q, such as a square (bottom of  FIG.  7   b   ) or a rectangular (bottom of  FIG.  7   c   ) cross section Q for example, or a round cross section Q, such as an oval (bottom of  FIG.  7   d   ) or a teardrop-shaped (bottom of  FIG.  7   e   ) cross section Q for example. 
     The circlip  35  is formed from a round wire. The circlip  35  has an inside diameter of exactly 10.8 mm, approximately except for a manufacturing tolerance. The circlip  35  is designed in accordance with DIN 7993. The circlip  35  is of c-shaped design. The circlip  35  is designed as a segment of a ring. 
     The recess  49  of the securing element  47  runs in the circumferential direction U around the output axis a of the output shaft  31 . The securing element  47  can be formed by the brake element  41  ( FIG.  3   a   ,  FIG.  4   b   ) or the transmission gear element  37  ( FIG.  3   b   ,  FIG.  4   a   ) which is fitted onto the output shaft  31  in each case. The securing element  47  extends in the axial direction along the output axis a of the output shaft  31  and surrounds the securing ring  35  at least in sections. The securing element  47  surrounds the securing ring  35  in the circumferential direction U around the output axis a through 360°. 
     The recess  49  has a maximum radial extent in the radial direction of the output axis a, which maximum radial extent is greater than a radial extent of a section of the output shaft  31  which is surrounded by the recess  49  of the securing element  47  in at least one operating state. 
     The recess  49  delimits the securing element  47  at least partially in the radial and in the axial direction in relation to the output axis a. 
     The recess  49  has a recess surface  55  which delimits the recess  49  in the radial direction of the output axis a. The recess surface  55  is designed to be substantially concentric in relation to the output shaft  31  about the output axis a. The recess surface  55  can have an axial extent along the output axis a, which axial extent is greater than an axial extent of the securing ring  35 . 
     The output shaft  31  has a securing groove  57  ( FIG.  6   ), which encircles the output shaft  31 , for receiving the securing ring  35 . The securing groove  57  is designed as a partial tapered portion of the diameter of the output shaft  31 . The securing groove  57  is designed as a securing notch which is provided to receive the securing ring  35  and to hold said securing ring in an interlocking manner in the axial direction along the output axis a. The recess  49  is provided to surround the securing groove  57  in the radial direction in relation to the output axis a in at least one operating state. The securing groove  57  has a round or a concave contour  59  ( FIG.  6   ). In this case, the contour  59 , as viewed along the output axis a, steadily tapers and steadily rises again, so that there is no jump in the diameter profile. As a result, the notching effect of the output shaft is minimized. 
     The securing element  47  has a securing apparatus  61  which is provided to secure the securing ring  35  against independently coming loose in at least one operating state. The securing apparatus  61  comprises the recess  49  with a maximum radius which is smaller than a maximum radius of the securing ring  35  in a state fitted on the output shaft  31  which is not situated in the securing groove  57 . The recess  49  surrounds the securing ring  35  in at least one operating state in such a way that the securing ring  35  is prevented from independently coming loose in the radial direction. The recess  49  has a maximum radius which is greater than a maximum radius of the securing ring  35  in a state inserted in the securing groove  57 . In other words, the maximum radius of the recess  49  in a section of the output shaft  31  adjacent to the securing groove  57  is smaller than a radius of the output shaft  31  and the material thickness t of the securing ring  35 , so that the securing ring  35  cannot independently come loose from the securing groove  57  in an operating state surrounded by the recess  49 . The recess surface  55  of the recess  49  can form a distance x from the output shaft  31 , which distance is smaller than a material thickness t of the securing ring  35 . The securing ring  35  has a constant material thickness t. 
     The roller bearing element  39  is provided to support the output shaft  31  in a rotatable manner. The roller bearing element  39  makes contact with the crown gear element  37  or the brake element  41  in the axial direction. In the process, the crown gear element  37  can particularly advantageously make contact with the roller bearing element  39  by the transmission gear element forming a supporting region, in particular a supporting point, a supporting line and/or a supporting surface, in relation to the bearing element, which supporting region is at a distance from the output shaft in the radial direction. Therefore, the supporting region of a transmission gear element or of a brake element  41  is displaced further radially outward and reduces a bending moment, which acts on the output shaft  31 , as a result. 
     The output shaft  31  has a first contact region  64 , which is designed as a first active surface  63  for the roller bearing element  39 , and a second contact region  66 , which is designed as a second active surface  65  of the crown gear element  37  or of the brake element  41 . The first contact region  64  is separated from the second contact region  66  by the securing groove  57 . The first active surface  63  serves as the active surface onto which the roller bearing element  39  is fitted. The second active surface  65  serves as the active surface onto which the crown gear element  37  or the brake element  41  is fitted. 
     The circlip  35  has a constant cross section. The circlip  35  is bent around the output axis a. The circlip  35  can have a tensioned and an untensioned state. In the untensioned state, the circlip  35  is bent in a c shape in such a way that a radius of the circlip  35  is smaller than a radius of the output shaft, and/or that a radius of the securing ring is equal to or smaller than a radius of the securing groove of the output shaft. In the tensioned state, the securing ring has a larger radius than in an untensioned state. For example, in a tensioned state, the circlip  35  can be arranged on the first contact region  54  or the second contact region  66 , as a result of which the radius of the circlip  35  widens. For example, in an untensioned state, the circlip  35  can be arranged in the securing groove  57 , so that the radius of the circlip  35  reduces in size.