Abstract:
A tool assembly provided with a housing defining a chamber, and a reciprocating work tool arranged in the chamber, is disclosed. A tool retention member has an aperture through which the work tool extends. Engaging structure including mutually engaging protrusions on the housing and the tool retention member is configured to permit engagement of the tool retention member with the housing by relative rotation of the tool retention member and the housing. Retention structure on the work tool is configured to prevent removal of the work tool from the housing when the tool retention member is engaged with the housing. A locking structure is configured to lock the tool retention member and housing against relative rotation. A prestressing structure is located between the protrusions on the housing and a portion of the tool retention member and is configured to urge the tool retention member away from the housing.

Description:
[0001]    This a continuation of U.S. application Ser. No. 11/452,381, filed Jun. 14, 2006, and claims the priority benefit of European Patent Application No. 05253700.8, filed Jun. 15, 2005. The entire contents of U.S. application Ser. No. 11/452,381 are hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates generally to a tool assembly having a removable tool, and more specifically to a hydraulic or pneumatic hammer assembly having a removable work tool. 
       BACKGROUND 
       [0003]    Hydraulic hammers are used on work sites to break up large hard objects before such objects can be moved away. Hydraulic hammers may be mounted to back hoes or excavators, or may be hand-held. Typically, the hammer assembly is powered by either a hydraulic or pneumatic pressure source. During a work or power stroke, high fluid pressure is applied to a first shoulder of a piston, thereby driving the piston in a forward direction. The piston then strikes a work tool, which is driven in the forward direction thereby causing a work tip of the work tool to strike the rock, concrete, asphalt or other hard object to be broken up. During a return stroke, fluid pressure is applied to a second shoulder of the piston in order to return the piston to its original position. 
         [0004]    The work tool is retained within a sleeve, commonly referred to as a front head. Conventionally a tool retention pin is used to retain the work tool within the front head. The pin extends across one side of the front head and engages with a transverse machined groove in the work tool. The height of the groove is greater than the diameter of the pin, thereby allowing reciprocal forward and backward movement of the hammer over a limited range of movement. The pin and groove are subject to burring in use, because of the repeated impact. Upon servicing it is necessary to remove the pin before the tool can be removed from the front head. The burring must then be removed before the pin or tool can be replaced in the front head. Moreover, the tool is restrained from rotation by the pin, so unwanted torque can be transferred from the tool to the tool assembly and the machine to which it is mounted. 
         [0005]    At least some of the disclosed embodiments may overcome one or more of the abovementioned drawbacks. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with a first aspect of the present disclosure, there is provided a tool assembly comprising a housing defining a chamber, a reciprocating work tool arranged in the chamber, and a tool retention member having an aperture through which the work tool extends. The housing includes engaging structure which permits the engagement of the tool retention member with the housing by relative rotation of the tool retention member and housing. The work tool is provided with retention structure which prevents the removal of the work tool from the housing when the tool retention member is engaged with the housing. 
         [0007]    In accordance with a second aspect of the present disclosure, there is provided a method of installing a work tool in a tool assembly, comprising: providing a tool assembly having a housing defining a chamber and a tool retention member having an aperture; inserting a work tool in the aperture of the tool retention member; engaging the tool retention member and the housing by relative rotation of the tool retention member and housing, thereby securing the work tool for reciprocating movement within the chamber, and locking the tool retention member and housing against relative rotation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a hammer assembly according to one disclosed embodiment; 
           [0009]      FIG. 2  is an exploded view of the hammer assembly of  FIG. 1 ; and 
           [0010]      FIG. 3  shows a longitudinal section of the front head and work tool of the hammer assembly of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    With reference to  FIGS. 1 to 3  there is shown a tool assembly  10 , specifically a hydraulic hammer assembly, which may be attached to a backhoe or excavator (not shown). The tool assembly  10  includes a housing  11 , a chamber  16  defined in the housing  11 , a piston  18  and a work tool  20 . The housing  11  is a two part housing including an upper housing member  12  and a lower housing member  14 , often referred to as a front head, which define an upper and lower chamber respectively, which together make up the chamber  16 . The piston  18  is operatively housed in the chamber  16  such that the piston  18  can translate in the general direction of arrows  22  and  24 . In particular, during a work stroke, the piston  18  moves in the general direction of arrow  22  so as to strike the work tool  20 . Conversely, during a return stroke, the piston  18  moves in the general direction of arrow  24 . 
         [0012]    A hydraulic circuit (not shown) provides pressurized fluid to urge the piston  18  towards the work tool  20  during the work stroke and to return the piston  18  during the return stroke. The hydraulic circuit is not described further, since it will be apparent to the skilled person that any suitable hydraulic arrangement may be used to provide pressurized fluid to the piston  18 , such as the arrangement described in U.S. Pat. No. 5,944,120. 
         [0013]    Near the end of the work stroke, the piston  18  strikes the upper end  40  of the work tool  20 . The work tool  20  includes a shaft  42 , a retaining flange  44  and a tip  46 . The shaft  42  passes through a tool retention member  80  in the form of a bushing with a central aperture  82 . The aperture  82  has a diameter smaller than that of the retaining flange  44  and thereby limits the movement of the work tool  20  in the general direction of arrow  22 . In a variation of the disclosure, instead of the retaining flange  44 , the tool retention structure can comprise a portion of the work tool of any other suitable shape having a lateral size greater than that of the aperture  82  of the tool retention member  80 . 
         [0014]    The tool retention member  80  can be removed from the housing  11 , as described below, to allow a variety of work tools  20  with different configurations of the tip  46  to be attached to the tool assembly  10 . As the piston  18  strikes the work tool  20 , the force of the piston  18  is transmitted through the work tool  20  to the tip  46  in the general direction of arrow  22 . Moreover, this force is applied to a hard object such as rock, concrete, or asphalt in order to break up the hard object. 
         [0015]    The upper and lower housing members  12 ,  14  are connected by a housing engaging structure  50 . In the illustrated embodiment the housing engaging structure  50  includes, for example, four lugs  52  provided equidistantly about the circumference of a plug portion  54  of the upper housing member  12 . These are shaped such that as the plug portion  54  is inserted into the lower housing member  14  the lugs  52  can pass between four projections (not shown), for example, formed on the internal wall of the socket portion  56 . The upper housing member  12  is then rotated by, for example, 45 degrees relative to the lower housing member  14  so that the lugs  52  engage beneath the projections  58 . 
         [0016]    Prestressing structure in the form of four jacking screws  70  are provided to urge the upwardly facing mating surfaces  72  of the lugs  52  against corresponding downwardly facing mating surfaces provided on the projections formed on the internal wall of the socket portion  56 . The screws  70  engage in threaded apertures  76  provided equidistantly around the perimeter of a circular flange  78  of the upper housing member  12 . The jacking screws  70  engage with an upwardly facing bearing surface  79  formed on the upper end of the lower housing member  14 . 
         [0017]    The tool retention member  80  and the housing  11  are connected by an engaging structure  90 . In the illustrated embodiment the engagement structure  90  includes four lugs  92  provided equidistantly about the circumference of a plug portion  94  of the tool retention member  80 . These are shaped such that as the plug portion  94  is inserted into a socket portion  96  of the lower housing member  14  the lugs  92  can pass between four projections  98  formed on the internal wall  100  of the socket portion  96 . The tool retention member  80  is then rotated relative to the lower housing member  14  so that the lugs  92  engage beneath the projections  98 . It is to be understood that other forms of mutually engaging protrusions may be envisaged, and the shape and number of lugs and protrusions can be varied and are not limited to those shown in the figures. A stop (not illustrated) may be formed on the internal wall  100  of the socket portion  96  such that upon rotation of the tool retention member  80  one of the lugs  92  comes into contact with the stop to indicate that sufficient rotation has taken place. 
         [0018]    Locking structure in the form of two set screws  110  are provided in apertures in the housing  11 . These engage with the plug portion  94  of the tool retention member  80  and prevent relative rotation of the tool retention member  80  and housing  11 . However, any other suitable locking structure may be provided, and the locking structure may be omitted if required. 
         [0019]    Prestressing structure in the form of a resilient seal ring  112  are provided to urge the first mating surfaces  114  of the projections  98  on the housing  11  against the second mating surfaces  116  of the lugs  92  on the tool retention member  80 . 
         [0020]    Movement of the tool  20  in the direction of arrow  22  is limited by the impact of the retaining flange  44  with the lower bushing or tool retention member  80 , while movement of the tool  20  in the direction of arrow  24  is limited by the impact of the top of the tool  40  with a shoulder  118  of a cylindrical tool stop  120  which in turn engages with the lower housing member  14 . 
         [0021]    Although the disclosed embodiments have been described with reference to lugs and projections, it is to be understood that other forms of mutually engaging protrusions may be provided. For example the second mating surface on the tool retention member  80  may be provided on a helical protrusion which forms a male thread and engages with the first mating surface of a corresponding helical protrusion on the housing  11 , serving as a female thread. In another example the engaging means may be a bayonet coupling in which two or more pins are provided on the plug portion  94  of the tool retention member  80 , the pins engaging with two or more L-shaped slots provided on the internal surface of the socket portion  96 . 
         [0022]    Although the disclosed embodiments have been described with reference to the plug portion  94  formed on the tool retention member  80  and the socket portion  96  formed on the housing  11 , the engaging structure may be reversed, so that the plug portion is formed on the housing  11  and the socket portion is formed on the tool retention member  80 . 
         [0023]    Although the prestressing structure described above comprises a resilient seal ring  112 , other prestressing structure may be used, such as springs or other resilient elements which urge the tool retention member  80  and housing  11  apart. In the case of corresponding helical protrusions on the tool retention member  80  and housing  11  the prestressing structure may be the elastic or plastic deformation of the threads under a tightening torque on the housing members. 
       INDUSTRIAL APPLICABILITY 
       [0024]    To remove a work tool  20 , the set screws  110  or other locking structure are first loosened, and the tool retention member  80  rotated through, for example, 45 degrees, until the lugs  92  are aligned with the clearance sections between the projections  98  on the internal wall  100  of the socket portion  96  of the housing  11 . The tool retention member  80  and tool  20  can then be removed from the housing  11  in the direction of arrow  22 . To replace a work tool  20 , the process is reversed. 
         [0025]    Although the disclosed embodiments have been described with reference to a hammer assembly in which the tool is driven by a hydraulically actuated piston, the disclosed embodiments are applicable to any tool assembly having a reciprocating work tool movable within a chamber by suitable drive structure and/or return structure. The disclosed embodiments encompass pneumatic tools and other impact tools. 
         [0026]    At least some of the disclosed embodiments may eliminate the need for a retainer pin, which eliminates a dust entry path and simplifies the process of tool replacement, since the need to remove burring from the pin or tool is eliminated. Furthermore, stress concentration at the point of contact with the pin may be avoided, since the tool retention member allows a more even distribution of stress. 
         [0027]    At least some of the disclosed embodiments may allow the work tool to rotate, unlike the prior art retainer pin, providing more even wear of the work tool and increased tool life. If particular circumstances require that the tool should not be able to rotate, the tool retaining flange  44  can include longitudinal keys (not shown) which engage with longitudinal grooves (not shown) in the internal wall  100  of the housing  11 . 
         [0028]    While the disclosed embodiments have been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only exemplary embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.