Patent Publication Number: US-2023150103-A1

Title: Electropneumatic impact mechanism

Description:
The present invention relates to an electropneumatic impact mechanism for an electric hand-held power tool, in particular a hammer drill and/or chipping hammer. The impact mechanism is provided with a transmission housing, a guide tube arranged at least partially in the transmission housing, an exciter piston that is movable in the guide tube, a connecting rod coupled to the exciter piston, and an eccentric wheel which is designed as an externally toothed gearwheel. The eccentric wheel is coupled to the connecting rod on one side and is mounted so as to be rotatable with respect to the transmission housing on the other side. 
     BACKGROUND 
     Impact mechanisms of the type mentioned at the beginning and hand-held power tools with such impact mechanisms are basically known from the prior art. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an impact mechanism which enables comparatively flexible use. 
     The present invention provides an axial gap between an eccentric wheel surface facing the connecting rod and a connecting rod surface facing the eccentric wheel. The axial gap is preferably used to optionally accommodate a lubrication space separating element, or at least a part thereof. It has been found to be advantageous if a radial spacing is provided between a contact point furthest away from the axis of rotation in the radial direction, which is between the connecting rod and the eccentric wheel, and the root circle of the eccentric wheel, which is designed as an externally toothed gearwheel. The radial spacing is preferably used to optionally accommodate a/the lubrication space separating element, or at least a part thereof. 
     The invention includes the finding that an optional introduction of a lubrication space separating element enables the lubrication space separating element to be dispensed with, for example in markets where lubrication space separation is not required. In markets where lubrication space separation is required, a lubrication space separation element possibly having seals can be introduced. By separating the impact mechanism lubrication space and the motor lubrication space, improved lubrication of the toothed parts, for example between a pinion of an electric motor and an external toothing of an eccentric wheel, is possible. In addition, this provides improved sealing against rock and concrete dust, which in turn reduces wear on the pinion-external toothing pairing or at least extends it over time. It is also conceivable for the hand-held power tools and/or the impact mechanisms to be delivered without a lubrication space separating element when they are first delivered and, depending on the type of use and wear, for the lubrication space separating element to be introduced during servicing. By reducing the number of parts, costs and weight are saved in impact mechanisms and/or hand-held power tools without a lubrication space separating element. 
     In a particularly preferred embodiment, the axial gap, based on the axis of rotation of the eccentric wheel in the axial direction, is at least 20 percent as large as the thickness of the eccentric wheel in the axial direction. It has been found to be advantageous if the axial gap is at least 5 mm. It has been found to be advantageous for the radial spacing between the contact point and the root circle to be at least 5 percent of a root circle diameter (FD) of the root circle. It has been found to be advantageous if the radial spacing is at least 5 mm. 
     In a particularly preferred embodiment, preferably for a specific market, the impact mechanism has a lubrication space separating element which is received in the axial gap and/or in the radial spacing. It has been found to be advantageous if the lubrication space separating element has an annular sealing collar with a dynamic sealing ring which is arranged coaxially with respect to the axis of rotation and is pressed against the radial spacing. 
     In a further preferred embodiment, the lubrication space separating element has an end sealing collar which at least partially seals the eccentric wheel in relation to a housing wall. The end sealing collar can have a static sealing ring which is arranged coaxially with respect to the axis of rotation and is pressed against an inner edge of the transmission. In a further preferred embodiment, the lubricating space separating element has a sleeve-shaped sealing chamber for receiving a pinion of an electric motor. It has been found to be advantageous if the annular sealing collar, the end sealing collar and the sealing chamber are formed integrally with one another. 
     In a particularly preferred embodiment, the lubrication space separating element is free from axial support loads which are indirectly or directly caused by the connecting rod. Advantageously, a height of the annular sealing collar in the axial direction is smaller than the axial gap. In a particularly preferred embodiment, the cover shell has, on a side facing the eccentric wheel, a retaining lip for securing the connecting rod in the axial direction. A profile of the retaining lip preferably at least partially follows a circular path of an eccentric point of the eccentric wheel. A plurality of retaining lips, each configured concentrically with respect to one another, can be provided. The retaining lips can differ in diameter from one another. The closure cover can have a support collar which extends in the axial direction and which stands up on the end sealing collar in the axial direction. 
     The present invention also provides an electric hand-held power tool, in particular a hammer drill and/or chipping hammer, with an impact mechanism as described above. It has been found to be advantageous if the hand-held power tool has an electric motor with a pinion for directly driving the eccentric wheel via the external toothing thereof. The pinion and the external toothing of the eccentric wheel can be located in a motor lubrication space. In a further preferred embodiment, the connecting rod and/or a surface portion of the eccentric wheel facing the cover shell are housed in an impact mechanism lubrication space which is hydraulically separated from the motor lubrication space. 
     The present invention also provides a lubrication space separating element with an annular sealing collar, an end sealing collar and a sealing chamber, which are formed integrally with one another. 
     Further advantages will become apparent from the following description of the figures. Various exemplary embodiments of the present invention are illustrated in the figures. The figures, the description and the claims contain numerous features in combination. A person skilled in the art will expediently also consider the features individually and combine them to form useful further combinations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       In the FIGURES, identical and similar components are denoted by the same reference signs. Specifically: 
         FIG.  1    shows a preferred exemplary embodiment of an impact mechanism according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     A first preferred exemplary embodiment of an electropneumatic impact mechanism  70  of an electric hand-held power tool is illustrated in  FIG.  1   . 
     The electropneumatic impact mechanism  70  has a transmission housing  60  and a guide tube  50 , wherein the guide tube  50  is arranged at least partially in the transmission housing  60 . The electropneumatic hammer mechanism  70  also has an exciter piston  40  that is movable in the guide tube  50 , a connecting rod  30  coupled to the exciter piston  40 , and an eccentric wheel  20 . The eccentric wheel  20  is coupled to the connecting rod  30  on one side and is mounted so as to be rotatable with respect to the transmission housing  60  about an axis of rotation DA via an end plate  10  of the transmission housing  60  on the other side. The end plate  10  is integrated in the transmission housing  60 . The eccentric wheel  20  is mounted rotatably on a bearing body  25  by means of a pair of plain bearings  28 . The bearing body  25  is introduced into the end plate  10  for rotation therewith. The eccentric wheel  20  is designed as an externally toothed gearwheel  29 , which can be rotationally driven by an electric motor  90 . For this purpose, the electric motor  90  has a pinion  91  which is paired with the external toothing  29 . 
     As can be seen from  FIG.  1   , an axial gap AS is provided between an eccentric wheel surface EO facing the connecting rod  30  and a connecting rod surface PO facing the eccentric wheel  20 . The axial gap AS, based on the axis of rotation DA of the eccentric wheel  20  in the axial direction AR, is, for example, about  30  percent as large as a thickness DE of the eccentric wheel  20  in the axial direction AR. As can likewise be gathered from  FIG.  1   , a radial spacing RA is provided between a contact point KP furthest away from the axis of rotation DA in the radial direction RR, which is between the connecting rod  30  and the eccentric wheel  20 , and the root circle FK of the external toothing  29  of the eccentric wheel  20 . The radial spacing RA between the contact point KP and the root circle FK is, for example, 5 percent of a root circle diameter FD of the root circle FK of the eccentric wheel. The connecting rod  30  has a connecting rod pin  31  which engages in the eccentric wheel  20 . The contact point KP is located at the transition from the connecting rod pin  31  to the eccentric wheel  20 . 
     Inside the transmission housing  60 , the impact mechanism  70  has an optionally introduced lubrication space separating element  90 , which realizes a hydraulic separation between the motor lubrication space  92  and the impact mechanism lubrication space  62 . The pinion  91  and the external toothing  29  of the eccentric wheel  20  are located in the motor lubrication space  92 . The connecting rod  30  and a wheel surface  26  facing the cover shell  65  (the diameter of which preferably corresponds at most to the root circle diameter FK) are housed in an impact mechanism lubrication space  62  which is hydraulically separated from the motor lubrication space  92 . 
     The lubrication space separating element  80  itself has an annular sealing collar  81 , an end sealing collar  83  and a sealing chamber  85 . In the exemplary embodiment shown here, the annular sealing collar  81 , the end sealing collar  83  and the sealing chamber  85  are formed integrally with one another. The lubrication space separating element  80  is composed, for example, of plastic. 
     The annular sealing collar  81  is used to seal the eccentric wheel  20  on its side facing the cover shell  65 . For this purpose, the annular sealing collar  81 , based on the axial direction AR, is accommodated in the axial gap AS between the connecting rod  30  and the eccentric wheel  20 . The annular sealing collar  81 , based on the radial direction RR, rests, as it were, on the radial spacing RA. The axial gap AS and the radial spacing RA are thus occupied by one and the same separating element in the form of the annular sealing collar  81 . The annular sealing collar  81  is provided with a dynamic sealing ring  82  which is arranged coaxially with respect to the axis of rotation DA and is pressed against the radial spacing RA. 
     The end sealing collar  83  is used to at least partially seal the eccentric wheel  20  in relation to a housing wall  68 . For this purpose, the end sealing collar  83  has a static sealing ring  84 , which is pressed in the axial direction AR against the housing wall  68 . The static sealing ring  84  in the exemplary embodiment of  FIG.  1    is arranged coaxially with respect to the axis of rotation DA in the region of the eccentric wheel  20 . In the region of the pinion  91 , the static sealing ring  84  also lies pressed against the housing wall  68  in the axial direction AR. In this region, however, the sealing ring  84  extends coaxially with respect to the rotation axis RO of the pinion  91 . 
     The sleeve-shaped sealing chamber  85  of the lubrication space separating element  80  finally serves to accommodate the pinion  91  of the electric motor  90 . 
     As can be gathered from  FIG.  1   , the transmission housing  60  is closed on an upper side  61 —from here the connecting rod  30  and the eccentric wheel  20 , inter alia, are introduced into the transmission housing  60 —by a cover shell  65 , which is composed, for example, of plastic. The cover shell  65  has a retaining lip  67  on a side  63  facing the eccentric wheel  20 , wherein a profile of the retaining lip  67  follows a circular path  23  of an eccentric point  21  of the eccentric wheel  20 . In the exemplary embodiment in  FIG.  1   , four retaining lips  67  which are concentric with respect to one another and each have a different diameter are provided. The retaining lips  67  are used to secure the connecting rod  80  in the axial direction AR. 
     The connecting rod  30  also secures the eccentric wheel  20  in the axial direction AR by an annular contact  33  of the connecting rod pin  31  in the eccentric wheel  20 —the contact point KP is furthermore located on said annular contact  33 . The cover shell  65  is thus directly responsible for securing the connecting rod  30  and indirectly (via the connecting rod  30 ) for securing the eccentric wheel  20  in the axial direction AR. This power flow described here manages without the “aid” of the lubrication space separating element  90 . In other words, the connecting rod  30  and the eccentric wheel  20  are axially secured even without the lubrication space separating element  90 , such that, if required —for example if there is no regulatory requirement—the lubrication space separating element  90  can be dispensed with. 
     In the exemplary embodiment of  FIG.  1   , a lubrication space separating element  90  is provided. As can also be gathered from  FIG.  1   , the cover shell  65  has a support collar  66  which extends in the axial direction AR and which stands up in the axial direction AR on the end sealing collar  83  and thus also exerts a pressing effect on the static sealing ring  84  in the axial direction AR. The lubrication space separating element  90  itself is thus held in the transmission housing  60 . In addition to the power flow described above without a lubrication space separating element  90  being introduced, when a lubrication space separating element  90  is introduced, additional securing of the eccentric wheel  20  in the axial direction is provided, namely indirectly via the dynamic sealing ring  82  of the annular sealing collar  81 , which is formed integrally with the end sealing collar  83 . Advantageously, the height of the annular sealing collar  81  is slightly smaller than the axial gap AS, and the annular sealing collar  81  and thus the entire lubrication space separating element  90  are free from axial support loads which are caused indirectly or directly by the connecting rod  30 . The lubrication space separating element  90  can thus optionally be encompassed by the impact mechanism  70 . 
     LIST OF REFERENCE SIGNS 
       10  End plate 
       20  Eccentric wheel 
       21  Eccentric point 
       23  Circular path 
       25  Bearing body 
       26  Wheel surface 
       28  Pair of plain bearings 
       29  External toothing 
       30  Connecting rod 
       31  Connecting rod pin 
       33  Contact 
       40  Exciter piston 
       50  Guide tube 
       60  Transmission housing 
       61  Upper side 
       62  Impact mechanism lubrication space 
       63  Facing side 
       65  Cover shell 
       66  Supporting collar 
       67  Retaining lip 
       68  Housing wall 
       70  Impact mechanism 
       80  Lubrication space separating element 
       81  Annular sealing collar 
       82  Dynamic sealing ring 
       83  End sealing collar 
       84  Static sealing ring 
       85  Sealing chamber 
       90  Electric motor 
       91  Pinion 
       92  Motor lubrication space 
     AR Axial direction 
     AS Axial gap 
     DA Axis of rotation of the eccentric wheel 
     DE Thickness of the eccentric wheel 
     EO Eccentric wheel surface 
     FK Root circle 
     KP Contact point 
     FD Root circle diameter 
     PO Connecting rod surface 
     RA Radial spacing 
     RO Rotation axis of the pinion 
     RR Radial direction