Abstract:
This patent relates to a method of assembling a spindle assembly comprising: a tubular spindle ( 2 ); a beat piece structure which is capable of being located and slid within a part ( 6 ) of the spindle ( 2 ); a stop mechanism ( 20 ) located within the spindle ( 2 ) which prevents the beat piece structure from sliding past it when the beat piece structure is located in and sliding within the spindle ( 2 ); and a retention mechanism capable of being located within the spindle ( 2 ) and which prevents the beat piece structure from sliding past it when the beat piece structure is located in and sliding within the spindle ( 2 ); wherein the method comprises the steps of: 
       i) inserting the beat piece structure into the spindle through one end of the spindle and sliding it along the spindle ( 2 ) in one direction until it abuts the stop mechanism ( 20 );    ii) inserting the retention mechanism into the spindle through the same end of the spindle ( 2 ) until it locates at a predetermined position;    iii) sliding the beat piece structure in the opposite direction away from the stop mechanism ( 20 ) until it abuts the retention mechanism  106.  It also covers a spindle constructed by such a method.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to hammer drills, and in particular to a spindle assembly, and more in particular, to a spindle assembly comprising a ram catcher, a bush damper, a bearing beat piece and a beat piece mounted within the rotary spindle, and a method of assembly of such a spindle assembly.  
       BACKGROUND OF THE INVENTION  
       [0002]     A typical hammer drill is capable of operating in at least two modes of operation, a hammer only mode where the end of a drill bit located within the tool holder of the drill is repeatedly struck, usually by a beat piece, and a hammer and drill mode, where the end of the drill bit is repeated struck whilst the drill bit is rotated. Such drills typically consist of a spindle in which is located a ram which is reciprocatingly driven within the spindle by a reciprocating piston which is driven by a motor. The reciprocating ram strikes the beat piece which in turn strikes the end of the drill bit located within the tool holder. The spindle can also be rotatingly driven by the motor via gearing. Internal mode change mechanisms enable the hammer drill to operate in and change between the modes of operation. However, such hammer drills are complex in construction which result in complicated manufacturing procedures. It is therefore desirable to simplify to such procedures and to construct such a drill in a manner that simple construction procedures can be utilised.  
       BRIEF SUMMARY OF THE INVENTION  
       [0003]     According to the first aspect of the present invention, there is provided a method of assembling a spindle assembly comprising: 
        a tubular spindle;     a beat piece structure which is capable of being located and slid within a part of the spindle;     a stop mechanism located within the spindle which prevents the beat piece structure from sliding past it when the beat piece structure is located in and sliding within the spindle;     and a retention mechanism capable of being located within the spindle and which prevents the beat piece structure from sliding past it when the beat piece structure is located in and sliding within the spindle;     wherein the method comprises the steps of: 
            inserting the beat piece structure into the spindle through one end of the spindle and sliding it along the spindle in one direction until it abuts the stop mechanism;     inserting the retention mechanism into the spindle through the same end of the spindle until it locates at a predetermined position;     sliding the beat piece structure in the opposite direction away from the stop mechanism until it abuts the retention mechanism.    
               
 
         [0012]     According to the second aspect of the present invention, there is provided a method of disassembling a spindle assembly comprising: 
        a tubular spindle;     a beat piece structure located in and capable of being slid within a part ( 6 ) of the spindle;     a stop mechanism located within the spindle on one side of the beat piece structure with a space there between and which prevents the beat piece structure from sliding past it when the beat piece structure is slid within the spindle;     and a removeable retention mechanism located within the spindle adjacent the beat piece structure on the opposite side of it to that of the stop mechanism which prevents the beat piece structure from sliding past;     wherein the method comprises the steps of: 
            sliding the beat piece structure in a direction away from the retention mechanism into the space between the beat piece structure and the stop mechanism until it abuts the stop mechanism;     removing the retention mechanism from the spindle;     removing the beat piece structure from the spindle through the same end of the spindle as the retention mechanism.    
               
 
         [0021]     According to the third aspect of the present invention, there is provided a spindle assembly comprising: 
        a tubular spindle;     a beat piece structure located in and capable of being slid within a part of the spindle;     a stop mechanism located within the spindle on one side of the beat piece structure and which prevents the beat piece structure from sliding past it when the beat piece structure is slid within the spindle;     and a removeable retention mechanism located within the spindle adjacent the beat piece structure on the opposite side of it to that of the stop mechanism which prevents the beat piece structure from sliding past;     wherein a space is provided between the stop mechanism and the beat piece structure and the retention mechanism abuts against the retention mechanism.       
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     An embodiment of the present invention will no be described with reference to following drawings of which:  
         [0028]      FIG. 1  shows a vertical cross section of the front end of a hammer drill;  
         [0029]      FIG. 2  shows a vertical cross section of a spindle assembly during a first phase of assembly;  
         [0030]      FIG. 3  shows a vertical cross section of the spindle assembly during a second phase of assembly; and  
         [0031]      FIG. 4  shows a vertical cross section of the spindle assembly during a second phase of assembly;  
         [0032]      FIG. 5  shows a computer generated picture of a vertical cross section of the spindle assembly from the side;  
         [0033]      FIG. 6  shows a computer generated picture of a vertical cross section of the spindle assembly from a rear perspective view; and  
         [0034]      FIG. 7  shows a computer generated picture of a vertical cross section of the spindle assembly from a front perspective view. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]     Referring to  FIG. 1 , a hammer comprises a body in which is mounted an electric motor (not shown) which drives the hammer. The electric motor is capable of driving a hollow piston  80  in a reciprocating manner via a wobble bearing  82  which in turn is connected to the electric motor via a gear mechanism generally indicated by reference number  84 . The hollow piston  80  is located within a tubular spindle  2  which is capable of being rotatingly driven via a drive sleeve  86  which in turn is rotatingly driven via the gear mechanism generally shown at  84 . The hollow piston  80  reciprocatingly drives a ram  88  within the hollow piston  80  and which is used to strike a beat piece  16  which in turn strikes the end of the drill bit  90  located within a tool holder generally indicated at.  
         [0036]     The gear mechanism generally indicated at  84  enables the wobble drive and/or the drive sleeve  86  of the spindle  2  to be disconnected from the rotary drive of the electric motor. As the gear mechanism  84  forms no part of the present invention it is not described in any further detail. The mechanism by which the hammer action and the drilling action of the hammer is performed is well known in the art and therefore also will not be described further.  
         [0037]     The present invention relates to the construction of the spindle assembly and in particular to a method of construction of the beat piece arrangement within the spindle.  
         [0038]     As mentioned previously, the hammer comprises a tubular spindle  2  which is capable of being rotationally driven by the electric motor. The spindle  2  is hollow and circular in cross section along its length and is made in a one piece construction from steel.  
         [0039]     Referring to FIGS.  2  to  7 , the spindle  2  comprises two sections, a first tubular section  4  of circular cross section at the working end of the spindle  2  having a first outer diameter A and a first inner diameter B; and a second tubular section  6  of circular cross section towards the rear of the hammer having a second outer diameter C which is greater than the first outer diameter A and a second inner diameter D which is greater than the first inner diameter B. A shoulder  20  is formed between the sections  4 ,  6 .  
         [0040]     Formed on the inner wall  12  of the first section  4  of the spindle  2  are two splines  10  (only one is shown). An aperture  8  is formed through the wall of the first section  4  of the spindle  2 . The splines  10  and the hole  8  form part of a locking mechanism, more of which is shown in  FIG. 1  for an SDS drill bit  90 , the end of the shaft of which is inserted into the first section  4  in order to be attached to the first part of the spindle  2  by the locking mechanism. The locking mechanism and SDS drill bits do not form part of this invention and therefore will not be described in any more detail.  
         [0041]     Located in the second section  6  of the spindle  2  is a beat piece support mechanism which has two parts, a bearing beat piece  14  and a bush damper  18  which both support a beat piece  16  located within the bearing beat piece  14  and bush damper  18 . The bearing beat piece  14  is mounted between the bush damper  18  and the shoulder as shown in  FIG. 2  to  4 .  
         [0042]     The beat piece  16  is a solid bar of circular cross section along its length. An annular rib  22  is formed around the outer circumference of the beat piece  16  which projects radially outwards.  
         [0043]     The bearing beat piece  14  is tubular and circular in cross section. Its outer diameter is fractionally less than that of the inner diameter D of the second section  6  of the spindle  2 . The inner diameter of the bearing beat piece  14  is fractionally larger than that of the beat piece  16  enabling the beat piece  16  to be located within it as shown. A ledge  70  is formed in the inner surface of the bearing beat piece  14  at one end of the bearing beat piece  14  so that its inner diameter is larger than the rest of the inner surface of the bearing beat piece  14 . The size of the ledge  70  is such that the annular rib  22  of the beat piece  16  can be located within the space created by the ledge. When the bearing beat piece  14  is located within the spindle, the end which contains the ledge  70  faces the bush damper  18 . A groove  72  is formed around the outer surface of the end containing the ledge in which is located a rubber O ring  74 . A second groove is formed in the inner surface of the bearing beat piece  14  close to the other end in which is located a seal  76 .  
         [0044]     The bush damper  18  is also tubular and circular in cross section. Its outermost diameter is fractionally less than that of the inner diameter D of the second section  6  of the spindle  2 . The innermost diameter of the bush damper  18  is fractionally larger than that of the beat piece  16  enabling the beat piece  16  to be located within it as shown. A ledge  78  is formed in the inner surface of the bush damper  18  at one end of the bush damper  18  so that its inner diameter in the ledge is larger than the rest of the innermost surface of the bush damper  18 . The size of the ledge is the same as that in the bearing beat piece  14  and as such enables the annular rib  22  of the beat piece  16  to be located within the space created by the ledge  78 . When the bush damper  18  is located within the spindle, the end which contains the ledge  78  faces the bearing beat piece  14 . The two ledges  70 ,  78  create a space in which the rib  22  of the beat piece  16  can be located and slide as the beat piece  16  slides within the bearing beat piece  14  and bush damper  18 .  
         [0045]     A ram catch  60  is mounted within the spindle adjacent the bush damper  18  on the opposite side of the bush damper  18  to that of the bearing beat piece  14  as shown in FIGS.  2  to  7 . The ram catcher  60  is also tubular and circular in cross section. Its outermost diameter is fractionally less than that of the inner diameter D of the second section  6  of the spindle  2 . The innermost diameter of the bush damper  18  is larger than that of the beat piece  16  enabling the beat piece  16  to pass through it. The ram catcher  60  partially surrounds the bush damper  18  as shown.  
         [0046]     A flange  62  is formed on the bush damper  18  at its radially outermost position. Similarly a flange  64  is formed on the ram catcher at its radially outermost position. An O ring  66  is sandwiched between the two flanges  62 ,  64  as shown. A second flange  68  is formed on the ram catcher  60  at its radially inner most position. A ram catcher ring  100  is sandwiched between the end the bush damper  18  and the second flange  68 . An annular recess  102  is formed in the outermost flange  64  of the ram catcher  60  which faces away from the bush damper  18  as shown in  FIG. 2  to  7 .  
         [0047]     A groove  104  is formed in the inner wall of the spindle  2 . A circlip  106  is located within the groove  102  to prevent the ram catcher  60 , the bush damper  18  and bearing beat piece  14  from sliding past it. When fully assembled, the circlip  106  locates within the annular recess  102  of the outermost flange  64  of the ram catcher  60  as shown in FIGS.  4  to  7 .  
         [0048]     The function of the beat piece  16 , beat piece support mechanism, the ram catcher  60  and ram catcher ring  100  is well known and will not be described in any more detail.  
         [0049]     The method by which the structure is assembled will now be described.  
         [0050]     The assembly comprising the bearing beat piece  14 , the bush damper  18 , the ram catcher  60 , the seal  76 , the O rings  74 ,  66  and the ram catcher ring  100  are assembled into one beat piece and ram catcher assembly. Then, the beat piece and ram catcher assembly is inserted into the second section  6  of the spindle  2  through the end of the second section  6  and slid using a tool (not shown) within the spindle along the length of the second section  6  until abuts the shoulder  20 , the bearing beat piece  14  being located adjacent to and in contact with the shoulder as shown in  FIG. 2 . As the, the beat piece and ram catcher assembly is slid to this position, it passes over the groove  104  and leaves it exposed when the , the beat piece and ram catcher assembly is adjacent the shoulder  20 . The circlip  106  is then inserted into the same end of the spindle  2  as the beat piece and ram catcher assembly, and then is slid within the spindle along the second section  6  of the spindle  2  until in engages the groove  104  within the second section  6  of the spindle  2  wherein it locates within the groove  104  due to the outward biasing force of the circlip  106 . The circlip  106  is thus prevented from sliding in either direction by the groove  104 . A tool  110 , such as a metal rod, is then inserted into the end of the spindle in the first section  4  and pushed into the spindle until it engages with the beat piece  16 . Using the tool  110 , a force is applied to the beat piece  16  which causes the beat piece  16  to slide within the beat piece support structure until the rib  22  engages the rear wall of the ledge  78  of the bush damper  18  as shown in  FIG. 3 . A force is continued to be applied to the beat piece  16  by the tool  110 , pushing the whole of the beat piece and ram catcher assembly along the second section  6  of the spindle  2  until ram catcher engages with the circlip. At this point, the circlip  106  is located within the annular recess  102  formed around the ram catcher  60  as shown in  FIG. 4 . This locks the circlip  106  in the groove  104  as it is prevented from leaving it by the wall of the annular recess  102  A space  112  is left between the shoulder  20  and the bearing beat piece  14 .  
         [0051]     The beat piece and ram catcher assembly can be removed in the reverse manner. Using a tool inserted through the end of the second section  6  of the spindle  2 , the beat piece and ram catcher assembly can be slid along the second section  6  of the spindle towards the first section  4  until the bearing beat piece  14  engages the shoulder  20 , the circlip  106  now having been removed from the annular recess  102 . Thus the circlip is no longer locked into the groove  104 . The circlip  106  is removed from the groove  104  and slid along the spindle until it exits the end in the second section  106 . A tool is then inserted into the end of the spindle in the first section and pushed into the spindle until it engages with the beat piece  16 . Using the tool, a force is applied to the beat piece  16  which causes the beat piece  16  to slide within the beat piece support structure until the rib engages the rear wall of the ledge of the bush damper  18 . A force is continued to be applied to the beat piece  16  by the tool, pushing the whole of the beat piece and ram catcher assembly along the second section  6  of the spindle  2  until it is pushed out of the spindle  2  through the end in the second section.  
         [0052]     It will be appreciated that the the beat piece and ram catcher assembly can be assembled inside the spindle  2  by first sliding in the bearing beat piece  14  with the seal  76  and O ring  74  until it abuts the shoulder, then inserting the beat piece  16  into both the spindle and bearing beat piece  14 , then sliding in the bush damper  18  until it abuts the bearing beat piece  14  and then sliding in the ram catcher with the O ring  66  and ram catcher ring  60  until they abut against the bush damper  18 . The beat piece and ram catcher assembly is then pushed backwards to engage the circlip  106  as described previously.