Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority, under 35 U.S.C. §119, to UK Patent Application No. 16 109 53.0, filed Jun. 23, 2016, titled “Motor End Cap”, contents of which are incorporated herein by reference in entirety. 
       FIELD 
       [0002]    The present invention relates to a drill having a motor with an end cap which forms a separating wall between two chambers inside of the drill. 
       BACKGROUND 
       [0003]    Drills, hammer drills and chippers are power tools that can operate in at least one of three modes of operation. Drills, hammer drills and chippers have a cutting tool such as a drill bit or chisel that can be operated in at least one of a hammering mode, a rotary mode and a combined hammer and rotary mode. Drills, hammer drills and chippers will typically comprises an electric motor and a transmission mechanism by which the rotary output of the electric motor rotationally drives the cutting tool and/or repetitively strikes the cutting tool to perform the hammer function. Such a transmission mechanism can be mounted within a transmission housing which is in turn mounted within an external housing of the hammer drill. The electric motor can be directly mounted onto the transmission housing. The use of such a transmission housing allows the transmission mechanism to be assembled within the transmission housing and the electric motor mounted onto the transmission housing with the rotary output of the electric motor being drivingly connected to the transmission mechanism to form a single sub-assembly which can then inserted into the external housing. 
         [0004]    EP1674215 discloses a hammer drill capable of operating in all three modes of operation and which has a transmission mechanism mounted within a transmission housing and an electric motor mounted onto the transmission housing which are then mounted within an external housing. 
       SUMMARY 
       [0005]    Accordingly there is provided a drill comprising: a body, the body comprising a housing formed internally with at least two chambers; a rear handle mounted on the body; a tool holder mounted on the front of the body; an electric motor mounted in a first chamber, the electric motor comprising an end cap attached to a motor housing; a transmission mechanism mounted in a second chamber which is in driving connection with the electric motor, the transmission mechanism being driven by the electric motor when the electric motor is activated to either impart impacts to and/or rotate a cutting tool when held by the tool holder. The end cap engages with the housing to form a separating wall which separates the first and second chambers. 
         [0006]    An embodiment of the invention will now be described with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a side view of a hammer drill; 
           [0008]      FIG. 2  shows a side view of the hammer drill of  FIG. 1  with half of the external housing removed; 
           [0009]      FIG. 3  shows a side view of the hammer drill of  FIG. 1  with half of the external housing and half of the transmission housing removed; 
           [0010]      FIG. 4  shows a perspective view of the electric motor; 
           [0011]      FIG. 5  shows a top view of the electric motor; 
           [0012]      FIG. 6  shows a bottom view of the electric motor; and 
           [0013]      FIG. 7  shows a side view of the electric motor with the tubular can removed. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring to  FIG. 1 , a battery-powered hammer drill comprises a body  2  having an external tool housing formed from a number of clam shells  4 ,  6 ,  8  connected to each other, and a tool holder  10  for holding a cutting tool such as a drill bit (not shown). Mounted on the body  2  via a vibration dampening mechanism  12  (which is not described in any detail as it does not form part of the present invention), is a handle  14  having a trigger  16  for activating the hammer drill. A battery pack (not shown) can be releasably attached within a receptacle  18  attached to the bottom of the handle  14 . A mode selector knob (not shown) is provided on the side of the body  2  for selecting the mode of operation of the hammer drill, the modes of operation being a hammer only mode, a rotary only mode and a combined hammer and rotary mode. 
         [0015]    Referring to  FIG. 2 , mounted inside of the body  2  is a transmission housing  20 , in which is mounted a transmission mechanism  22  (described in more detail below), and an electric motor  24  (described in more detail below) attached to the transmission housing  22 . 
         [0016]    Referring to  FIG. 3 , the electric motor  24  has an output shaft  26  which extends into the transmission housing  20 . The end of the output shaft  26  has a pinion  28  formed on it. The transmission mechanism comprises a first gear  30  rigidly attached to a first rotatable shaft (not shown), which meshes with the pinion  28  such that rotation of the pinion  28  results in rotation of the first gear  30 , which in turn results in rotation of the first rotatable shaft. The first rotatable shaft is rotatably mounted within a first set of bearings  36 . 
         [0017]    Mounted on the end of the first rotatable shaft in a freely rotatable but non-axially slideable manner is a fourth gear  40 . A crank plate  42  is rigidly attached to the fourth gear  40 . A crank shaft  44  is pivotally attached at one of its ends to an eccentric pin (not shown) mounted on the crank plate  42 . A piston (not shown) is pivotally attached to the other end of the crank shaft  44 . The piston is slidingly mounted within a rotatable output spindle  46 . Rotation of the fourth gear  40  results in rotation of the crank plate  42 , together with the eccentric pin, which in turn results in the reciprocation of the piston within the output spindle  46 . The piston forms part of a hammer drive mechanism. The reciprocating movement of the piston drives the hammer drive mechanism. Hammer drive mechanisms are well known in art and any suitable design of hammer mechanism can be used. As the design of such a hammer mechanism does not form part of the invention, no further description of the hammer drive mechanism 
         [0018]    Mounted on the first rotatable shaft in a freely rotatable but non-axially slideable manner is a second gear  32 . The second gear  32  meshes with a third gear  34  which is rigidly mounted on a second rotatable shaft (not shown). The second rotatable shaft is rotatably mounted with a second set of bearings  38 . Rigidly mounted on the end of the second rotatable shaft is a first bevel gear  50 . The first bevel gear  50  meshes with a second bevel gear  52  mounted on the output spindle  46 . The second bevel gear  52  is drivingly connected to the output spindle  46  via a torque clutch  54 . When the torque across the torque clutch  54  is below a pre-set value, the rotary movement of the second bevel gear is transferred to the output spindle  46 . When the torque across the torque clutch  54  is above the pre-set value, the torque clutch  54  slips and no rotary movement of the second bevel gear  52  is transferred to the output spindle  46 . Rotation of the second gear  32  results in rotation of third gear  34 , the second rotatable shaft and first bevel gear  50 . Rotation of the first bevel gear  50  results in rotation of the second bevel gear  52  which results in rotation of the out spindle  46 , so long as the torque clutch does not slip. The tool holder  10  is mounted on the output spindle  46  and therefore rotation of the output spindle  46  results in rotation of the tool holder  10 . The design of torque clutches are well know if the art and any suitable design can be used. As the torque clutch does not form part of the invention, no further description will be provided. 
         [0019]    Mounted on the first rotatable shaft in a non-rotatable but axially slideable manner is a mode change sleeve  60 . As such, the rotation of the first rotatable shaft results in rotation of the mode change sleeve  60 . In certain axial positions, the mode change sleeve  60  can mesh with the second gear  32  to drivingly engage the second gear  32 . When the mode change sleeve  60  drivingly engages the second gear  32 , the rotation of the first rotatable shaft results in rotation of the mode change sleeve  60  which in turn rotatingly drives the second gear  32 . In certain other axial positions, the mode change sleeve  60  can mesh with the fourth gear  40  to drivingly engage the fourth gear  40 . When the mode change sleeve  60  drivingly engages the fourth gear  40 , the rotation of the first rotatable shaft results in rotation of the mode change sleeve  60  which in turn rotatingly drives the fourth gear  40 . 
         [0020]    A mode change mechanism  62  can move the mode change sleeve  60  between three axial positions on the first rotatable shaft. In a first lowest position, the mode change sleeve  60  is in driving engagement with the second gear  32  only. As such, rotation of the first rotatable shaft results in rotation of the mode change sleeve  60  which in turn rotatingly drives the second gear  32  only, the fourth gear  40  remaining disengaged from the mode change sleeve  60 . As such, the hammer drill works in rotary only mode. In a second middle position, the mode change sleeve  60  is in driving engagement with both the second gear  32  and the fourth gear  40 . As such, rotation of the first rotatable shaft results in rotation of the mode change sleeve  60  which in turn rotatingly drives both the second gear  32  and the fourth gear  40 . As such, the hammer drill works in a combined hammer and rotary mode. In a third highest position, the mode change sleeve  60  is in driving engagement with the fourth gear  40  only. As such, rotation of the first rotatable shaft results in rotation of the mode change sleeve  60  which in turn rotatingly drives the fourth gear  40  only, the second gear  32  remaining disengaged from the mode change sleeve  60 . As such, the hammer drill works in hammer only mode. The design of mode change mechanisms are well know if the art and any suitable design can be used. As the mode change mechanism does not form part of the invention, no further description will be provided. 
         [0021]    The transmission mechanism  22  is mounted in the transmission housing which comprises two clam shells  64  fastened together with screws  68 . A seal  66  is sandwiched between the edges of the clam shells  64  to seal lubrication grease inside of the transmission housing  20 . 
         [0022]    The electric motor  24  will now be described with reference to  FIGS. 4 to 7 . 
         [0023]    The electric motor  24  is a brushless motor which comprises a tubular can  70  of generally circular cross section which is open at the top end and which has a longitudinal axis  90 . Mounted inside of the tubular can is a stator  72 . The stator  72  has a passageway formed through it. An armature  74  is mounted onto the output shaft  26 . The armature  74  is located inside of the stator  72 , with the longitudinal axis  90  of the output shaft  26  extending in a direction co-axial to that of the can  70 , the output shaft  26  extending through the length of the can  70 . 
         [0024]    Integrally formed as part of the can  70 , at the lower end of the can  70 , is a base plate  78 . The base plate  78  supports a first bearing  92  which supports one end of the output shaft  26  in a rotary manner. The output shaft  26  extends through the base plate  78  and away from the can  70 . Electric cables (not shown) are also mounted on to the base plate  78  and connect to the stator  72  to provide power and controls signals to the motor  24 . 
         [0025]    Attached to the upper end of the can  70  is an end cap  82 . The end cap  82  is manufactured in a one piece construction and comprises three sections; a first section  94  located adjacent the can  70 , a second section  98  located remote from the can  70  and a third section  96 , separating the first and second sections, comprising a radial flange which extends generally outwardly in a direction perpendicular to the longitudinal axis  90  of the can  70 . The end cap  82  is secured to the can  70  using four screws  100  which are inserted through four apertures  102  formed in the end cap  82  and screwed into four threaded bosses  104  formed in the can  70 . 
         [0026]    The end cap  82  supports a second bearing  110 , the second bearing  110  rotationally supporting the output shaft  26 , the output shaft  26  passing through the end cap  82  and extending away from the can  70  and end cap  82 . 
         [0027]    A radial fan  106  is mounted on the output shaft  26  adjacent the armature  74 . The majority of the fan  106  locates inside of the end cap  82 , the remainder being located inside of the end of the can  70  adjacent the end cap  82 . A first series of apertures  112  are formed in the second section  98  of the end cap  82 . The inside wall of the end cap  82  surrounding the fan  106  is shaped to form a baffle to guide the air expelled radially be the rotating fan  106  towards and through the first series of apertures  112 . The end of the can  70  adjacent the end cap  82  is shaped to form a baffle which co-operates with the baffle formed inside of the end cap  82  to guide the air. It will be appreciated that as an alternative design, the whole of the baffle could be formed inside of the end cap  82 . 
         [0028]    Formed in the base plate  78  is a second series of apertures  114 . 
         [0029]    When the motor  24  is activated, the armature  74 , the fan  106  and the output shaft  26  rotate. The rotating fan  106  draws air into the motor  24  through the second series of apertures  114 . The air passes through the inside of the can  70 , passing over the armature  74  and the stator  72 , and is drawn into the radial fan  106 . The radial fan  106  expels the air in a radial direction. The baffle formed by the inside wall of the end cap  82  then guides the air towards and directs it through the first series of apertures  112 . The flow of air through the motor  24  cools the motor down. 
         [0030]    When the motor  24  is assembled, the stator  72  is secured inside of the can  70 . The armature  74  and fan  106 , which have been mounted onto the output shaft  26 , are inserted into the stator  72  within the can  70 , the output shaft  26  being supported by the first bearing  92  in the base plate  78 . The end cap  82  is then secured to the can  70  using the screws  100  with the second bearing  110  supporting the output shaft  26 . The construction of motor  24  using a can  70  with an integral base plate  78  which is sealed by an end cap  82  produces a standalone component which can be manufactured and tested remotely from the rest of the hammer drill. 
         [0031]    When the hammer drill is assembled, the transmission mechanism  22  is assembled and mounted inside of the transmission housing  20 , the two clam shells  64  of the transmission housing  20  being fastened together with screws  68  to support and seal in the transmission mechanism  22 . The construction of such a transmission mechanism  22  mounted within such a transmission housing  20  (collectively referred to as a transmission) produces a standalone component which can be manufactured and tested remotely from the rest of the hammer drill. 
         [0032]    The assembled electric motor  24  is then attached to the assembled transmission. The output shaft  26 , which extends from the end cap  82 , is inserted into the transmission housing  20  through an aperture in the transmission housing  20  and is engaged with the first gear  30 , the pinion  28  meshing with the first gear  30  inside of the transmission housing  20 . The second section  98  of the end cap  82  then abuts against the base of the transmission housing  20 . The end cap  82  is then secured to the transmission housing  20  by using bolts  116  which pass through apertures  130  in the end cap and engage with threaded bores (not shown) formed in the transmission housing  20 . The securing of the end cap  82  to the transmission housing  20  attaches the electric motor  24  to the transmission housing  20  and transmission mechanism  22 . Attachment of the transmission to the motor  24  produces a standalone component which can be assembled and test separately from the rest of the hammer drill. 
         [0033]    The assembled transmission and motor  24  are then inserted into the external tool housing  4 ,  6 ,  8 . The transmission housing  20  is then secured to the external housing  4 ,  6 ,  8  using fasteners (not shown). This results in the electric motor  24  being secured indirectly to the external housing  4 ,  6 ,  8  via the transmission housing  20 . 
         [0034]    When the assembled transmission and motor  24  is located inside of the external housing  4 ,  6 ,  8 , the periphery of the flange of the third section  96  of the end cap  82  engages with an internal wall  118  of the external tool housing  4 ,  6 ,  8 , the flange forming an internal wall inside of the hammer drill. The flange forms part of a separating wall between two cambers  120 ,  122  formed inside of the external tool housing  4 ,  6 ,  8  when the assembled transmission and motor  24  are located inside of the external housing  4 ,  6 ,  8 . The first chamber  120  is formed on the side of the flange where the first section  94  of the end cap and the can  70  of the motor  24  are positioned with the motor  24  extending into and being located in the first chamber  120 . The second chamber  122  is formed on the side of the flange which is remote from the can  70 . The transmission mechanism  22  and transmission housing  20  is mounted within the second chamber  122 . 
         [0035]    The first series of apertures  112  in the end cap  82  are located inside of the second chamber  122 . The second series of apertures  114  in the base plate  78  are located in the first chamber  120 . Air is drawn from the first chamber  120  into the motor  24  through the second series of apertures  114 . Air is then expelled from the first series of apertures  112  into the second chamber  122 . The flange prevents air from moving from the first chamber  120  to the second chamber  122  except by passing through the motor  24 .

Technology Category: 7