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TECHNICAL FIELD 
       [0001]    This disclosure relates to design improvements for optimizing longevity and/or reducing the maintenance and/or replacement of parts in hydraulic hammers subjected to harsh cyclic stresses. More particularly, the disclosure relates to an improved nut pocket configuration for the front heads of hydraulic hammers affixed to and utilized on machines. 
       BACKGROUND 
       [0002]    Hydraulic hammers are generally employed on worksites to demolish and break up hard objects, including rocks, concrete, asphalt, and frozen ground. The hammers may be mounted to machines, such as excavators and backhoes, for example. The hammers may alternatively be powered by pneumatic pressure sources, as opposed to only hydraulic sources. In either event, a high-pressure fluid may be utilized within the hammer to cyclically drive a piston to strike a work tool, which in turn may carry an impulse wave to the object of demolition for breaking that object into smaller pieces, generally for easier removal from a worksite. 
         [0003]    The high impact and repetitive nature of operating a hydraulic hammer is hard on its component parts which may suffer stresses resulting in bending or breaking. Repairing these components can be difficult and time consuming, particularly when components are bent or are forced out of alignment. Against this history, it may be beneficial to provide a hydraulic hammer that better accommodates cyclic stress loads, as particularly applied to parts employed in the hammer 
       SUMMARY OF THE DISCLOSURE 
       [0004]    In one aspect, a powered hammer assembly includes a front head having nut pockets, each nut pocket including a cavity, a tie rod nut inserted into a respective nut pocket in a first direction, and a tie rod inserted into the front head and mechanically coupled to the tie rod nut. The assembly may also include a structure mechanically coupled to the tie rod that engages the cavity and opposes motion in a direction opposite the first direction. 
         [0005]    In another aspect, a method of operating a hydraulic hammer may include providing a front head having a nut pocket, the nut pocket having a side opening, where a top of the nut pocket is coupled to a tie rod bore and a bottom of the nut pocket has a cavity. The method may also include inserting a tie rod nut into the nut pocket, capturing a tie rod via the tie rod nut and inserting a structure mechanically coupled to the tie rod into the cavity. 
         [0006]    In yet another aspect, a mounting structure for a head of a powered hammer may include a front head having four rectangular side faces, four nut pockets, one nut pocket formed at each edge joining the four rectangular side faces and four tie rod bores, one tie rod bore provided from a top of the front head to each nut pocket. Each nut pocket may include a cavity formed at a bottom of each nut pocket, with each cavity opposite the respective tie rod bore in each of the four nut pockets. The mounting structure may also include a plurality of tie rod nuts, one each inserted into each of the four nut pockets, a plurality of tie rods, one each inserted into a respective one of the four tie rod bores, each tie rod mechanically attached to a respective tie rod nut and a structure mechanically coupled to the tie rod that engages the cavity and opposes motion normal to a longitudinal axis of the tie rod. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of an excavating machine that may incorporate the disclosed hydraulic hammer; 
           [0008]      FIG. 2  is a perspective view of one exemplary embodiment of the disclosed hydraulic hammer; 
           [0009]      FIG. 3  is a perspective view disclosing certain interior parts of the hydraulic hammer of  FIG. 2 ; 
           [0010]      FIG. 4  is a cutaway view of a front head of a hydraulic hammer with tie rod and tie rod nut; 
           [0011]      FIG. 5  is a perspective view of a front head of the hydraulic hammer; 
           [0012]      FIG. 6  is a cutaway view of the front head of  FIG. 5 ; 
           [0013]      FIG. 7  is a cutaway view of the front head with a tie rod and tie rod nut installed; 
           [0014]      FIG. 8  is a cutaway view of the front head with a tie rod and tie rod nut showing alternative counterforce provision; 
           [0015]      FIG. 9  is an alternate embodiment of the front head; 
           [0016]      FIG. 10  is a cutaway view of the embodiment of the front head of  FIG. 9 ; 
           [0017]      FIG. 11  is an alternate embodiment of a tie rod nut for use with the front head of  FIG. 9 ; 
           [0018]      FIG. 12  is a cutaway view of the embodiment of the front head of  FIG. 9  showing the tie rod nut of  FIG. 11  and a tie rod; and 
           [0019]      FIG. 13  is a method of using a front head assembly in a hydraulic hammer 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Referring initially to  FIG. 1 , an excavating machine  10  of a type used for digging and removing rock and soil from a construction worksite is shown. The excavating machine  10  may incorporate a cab body  12  containing an operator station, an engine, and operating controls (not depicted). The machine  10  may be supported by, and may move on, tracks  14 . An extensible boom  20  may be movably anchored to the cab body  12 , and an articulating stick  22 , also variously called a lift arm, may be secured to and supported for movement on the boom  20 . 
         [0021]    The excavating machine  10  may incorporate a hydraulic hammer  30  as depicted, or may alternatively incorporate another implement, at an operational end  28  of the stick  22 . Hydraulic cylinder actuators  26  may be utilized to move the stick  22  relative to the boom  20 , and to move hydraulic hammer  30  relative to the stick  22 . 
         [0022]    Referring now also to  FIG. 2 , a fluid powered hammer assembly, although herein called a hydraulic hammer assembly  30  may be secured to the operational end  28  of the stick  22 . The hydraulic hammer assembly  30  may include an upper portion  31  that includes a power cell  32  shown below in  FIG. 3  and a lower so-called front head portion  36  secured to the power cell  32 . A hammer tool  40  having an upper end (not shown) may be retained within the front head portion  36 . The hammer tool  40  may be adapted to produce cyclic vibrational movement at an intensity sufficient to demolish rocks, for example. The functional parts of the hydraulic hammer assembly  30 , including the hammer tool  40  may be constructed of a forged or otherwise hardened metal such as a refined steel, for example, to assure appropriate strength, although other suitable materials such as diamond bits for operative portions of the hammer tool  40 , for example, may be utilized within the scope of this disclosure. 
         [0023]    Referring now also to  FIG. 3 , the hydraulic hammer assembly  30  is shown alone, i.e. detached from the stick  22  and with its exterior case covers removed, to reveal an exposed power cell  32 , and a plurality of tie rods  44  circumferentially disposed about a cylindrical piston-containing sleeve structure  45 . The sleeve structure  45  may contain a piston (not shown) adapted to drive the hammer tool  40 . As such, the power cell  32  may be effective to utilize a suitable working fluid, such as a hydraulic and/or pneumatic fluid, for example, to reciprocally impact the piston against the upper end (not shown) of the hammer tool  40 . It may also be appreciated that the plurality of tie rods  44  may be effective to retain or hold the power cell  32  and the front head portion  36  together under harsh impact loads as may be experienced within the hydraulic hammer assembly  30 . 
         [0024]    The lower front head portion  36  may define an actual front head  46 , which may function as a structural housing to support the upper end (not shown) of the hammer tool  40  (shown only fragmentarily in  FIG. 3 ). An upper end  42  of each of the tie rods  44  may be secured to an upper structure  38  of the power cell  32 . Each tie rod  44  may have a threaded lower end (not depicted) that extends downwardly through a vertically oriented aperture or tie rod bore  48  within the front head  46 . The tie rod bore  48  defines a longitudinal axis of the installed tie rod  44 . Each tie rod  44  may be adapted to be threadedly secured to a tie rod nut  50 . 
         [0025]      FIG. 4  is a cutaway view of a prior art front head  46  showing a tie rod  44  and a tie rod nut  50 . It may be appreciated that each tie rod nut pocket  60  may be correspondingly positioned within each corner of the front head  46  to accommodate one tie rod nut  50 . In the disclosed embodiment, one of four nuts  50  may be secured within one of four corresponding tie rod nut pockets  60 . Each tie rod nut  50 , though having a circular circumference may actually be pie-shaped when viewed along other orientations (not included herein). The shape of the nut pocket  60  in the planar frontal view may be elliptical or oval, and the actual size of the nut pocket  60  relative to a corresponding tie rod nut  50  has been somewhat exaggerated for clarity purposes. 
         [0026]    During assembly, the tie rod  44  is inserted into the tie rod nut  50  and as the tie rod is tightened, the tie rod nut  50  is pulled up against the roof of the nut pocket  60 . However, the contact area of the tie rod nut  50  at the front of the nut pocket  60  is smaller than the contact area of the nut  50  at the back of the pocket due to the placement of the nut pockets at the corners of the front head  46 . Further, because the front of the nut pocket  60  is open, the top of the nut pocket  60  lacks the support at the front that it has at the closed structure of the back. This relative imbalance of support surfaces and the corresponding differences in front-to-back stiffness combined with the unsupported on the exterior side of the nut  50 , can both deform the nut pocket  50  and allow the nut  50  to rotate in the nut pocket  60  when the tie rod nut  50  is pulled up by the tie rod  44 . Over time, this rotation can bend the tie rod  44  and/or bend the tie rod nut  50  in the nut pocket  60 . Even a slight rotation in the tie rod nut  50  and therefore the tie rod  44  can shift the stress loads in the tie rod  44  and reduce its load carrying capability. This rotation is illustrated by the arrow  66  showing exemplary movement of the bottom of the tie rod nut  50  toward the opening in the nut pocket  60 . In practice, the top of the nut may also move toward the center of the front head  36 . 
         [0027]      FIG. 5  is a perspective view of a front head  70 . The front head  70  has a nut pocket  60  at each corner of the front head  46 . A cavity  62  in the form of a disk-shaped recess may be formed at the bottom of each nut pocket  60 . The cavity  62  is discussed in more detail below. 
         [0028]      FIG. 6  is a cutaway view of the front head  70  of  FIG. 5  showing the nut pocket  60  and the cavity  62 . In the embodiment of  FIGS. 5 and 6 , the cavity  62  has a conical bottom. In other embodiments, the cavity  62  may have a flat bottom or the bottom may have another shape. 
         [0029]      FIG. 7  is a cutaway view of the front head  70  with a tie rod  72  and tie rod nut  50  installed. The tie rod nut  50  may be placed in the pocket  60  and the tie rod  72  may be threaded onto the tie rod nut  50  via mating threads (not depicted). The tie rod  72  may have an extension  64  that extends into the cavity  62 . 
         [0030]    In operation, the tie rod extension  64  engages the front head  70  so that the outward force  66  is countered by an inward force  68  to stabilize the tie rod nut  50  in the nut pocket  60 . The extension  64  may not extend to a bottom of the cavity  62  so that during elongation of the tie rod  72 , it will not be constrained to the front head  70 . 
         [0031]    Several mechanisms may be used to provide a second counterforce  69  that further restricts rotation of the tie rod nut  50 . In one embodiment, a tolerance between the nut  50  at the back of the nut pocket  60  may be reduced to place the tie rod nut  50  in contact with the back of the nut pocket  60  so that the rotational movement of the tie rod nut  50  is further restricted by the counterforce at arrow  69 . 
         [0032]      FIG. 8  illustrates additional embodiments for providing a second counterforce at the back of the tie rod nut  50 . In one embodiment, a spacer  73  such as a disk may be placed to reduce the clearance at the top back of the tie rod nut  50  and provide the secondary counterforce  69 . The spacer  73  may be embedded in the back wall of the nut pocket  60  or at a back of the tie rod nut  50 . In place of, or in addition to these alternatives, a bolt  74  may be inserted at the cavity  62  to seat the tie rod nut  50  to the back of the nut pocket  60  to provide the counterforce  69 . The bolt  74  may apply pressure to the tie rod extension  64 , as shown, or may apply pressure to a bottom of the tie rod nut  86  when used with the embodiment of  FIG. 12 . 
         [0033]      FIG. 9  illustrates a front head  80  adapted so that the nut pocket  82  has a cavity in the form of a slot  84 .  FIG. 10  is a cutaway view of the nut pocket  82  illustrating the slot  84 . 
         [0034]      FIG. 11  is a perspective view of a tie rod nut  86  adapted to engage the slot  84  via a bottom face  88  of the tie rod nut  86  and a notch  90 . 
         [0035]      FIG. 12  is a cutaway view of the front head  80  of  FIG. 9  with a tie rod  44  installed into a tie rod nut  86 . As shown in  FIGS. 9 and 10 , a bottom face  88  of the tie rod nut  86  engages the slot  84  at notch  90 . The tie rod nut  86  may be shaped to allow the tie rod nut  86  to be inserted at a  90  degree angle and rotated to the correct alignment so that its bottom engages in the slot  84 . This allows the tie rod nut  86  to be sized to fit into the opening of the nut pocket  82  during assembly but to engage in the slot  84  when the inward counterforce is needed. Similar to  FIG. 7 , a horizontal outward force  66  is counteracted by an inward force  92  provided at an edge of the slot  84  against the notch  90 , which, as above, acts to stabilize the tie rod nut  86  in the nut pocket  82  and limit bending of the tie rod  44 . 
         [0036]    As described above, the mechanisms to provide an additional counterforce  69  such as a reduced tolerance between the back of the nut  86  and the nut pocket  82 , with or without a bolt  74 , or a disk  73  may be provided. 
         [0037]      FIG. 13  is a flow chart of a method  200  of operating a hydraulic hammer  30 , or more particularly, of assembling and using the hydraulic hammer  30 . At a block  202 , a front head  46  may be provided, the front head  46  having a nut pocket  60 . The nut pocket  60  may have a side opening used to insert a tie rod nut  50  or  86 . A top of the nut pocket  60  may be coupled, that is, open to a tie rod bore  38  at the top and a bottom of the nut pocket may have a cavity  62  or  84 . The cavity  62  may be formed in a cylindrical shape and have any one of several bottom shapes including a flat bottom and a conically shaped recess bottom. In another embodiment, the cavity  84  may be in the form of a rectangular slot. 
         [0038]    At a block  204 , a tie rod nut  50 ,  86  may be inserted into the nut pocket. 
         [0039]    At a block  206 , a tie rod  44 ,  72  may be inserted into the tie rod nut  50 ,  86  via the tie rod bore  48 . The tie rod  44 ,  72  may be captured by the tie rod nut  50 ,  86 , for example, by threading the tie rod  44 ,  72  into the tie rod nut  50 ,  86 . 
         [0040]    At a block  208 , a structure mechanically coupled to the tie rod  44 ,  72  may be inserted into the cavity  62 ,  84 . In one embodiment, the structure may be an extension  64  of the tie rod  72  into the cavity  62 . In another embodiment, the structure may be a bottom portion of the tie rod nut  86  having a notch  90  that engages the cavity  84  in the form of a slot. 
         [0041]    At a block  210  a force may be applied to the tie rod nut  50 ,  86  that causes a rotational force at the tie rod nut  50 ,  86 . 
         [0042]    At a block  212 , one or more counterforces may be applied opposite the rotational force at the tie rod nut  50 ,  86 . As described above, a first counterforce  68 ,  92  may be applied at the bottom of the tie rod  50  nut via an extension  64  of the tie rod  44  or a structure of the tie rod nut  86  that engages a cavity  84  in the nut pocket  82 . An additional counterforce  69  may be applied at the inside top of nut  50 ,  86  by causing contact between a back of the nut  50 ,  86  and a back of the nut pocket  60 ,  82 , as described above. In this manner, damage such as bending of the tie rod can be minimized by preventing rotation of the tie rod nut  50 ,  86  in the nut pocket  60 . 
         [0043]    Although the drawings and description herein may be limited to the specific embodiments disclosed, those skilled in the art may appreciate that numerous variations may fall within the spirit and scope of the appended claims. 
       INDUSTRIAL APPLICABILITY 
       [0044]    In use, a tie rod  44  may be bent during normal use in a prior art manner because the open side of the nut pocket  60  and structural imbalance of the front head  36  at the nut pocket  60  may allow a tie rod nut  50  to rotate in the nut pocket  60  when the tie rod nut  50  is pulled up at the front head  36  by the tie rod  44 . As described above, a counterforce  68  or  92  to an outward force  66  caused by the impending rotation of the nut  50 ,  86  keeps the nut  50 ,  86 , and therefore the tie rod  44 , in better alignment, reducing wear and stress. A second counterforce  69  may increase the counter-rotational effect on the tie rod nut  50 ,  86 . 
         [0045]    Either the tie rod extension  64  or the tie rod nut notch  90  engages the cavity  62 ,  84  formed in the bottom of the nut pocket  60  or  82  to provide the counterforces  68 ,  69  and/or  92 . 
         [0046]    Because tie rod bending can result in difficult repairs and extended downtime, the ability to maintain tie rod integrity benefits an owner/operator through improved efficiency, reduced replacement parts costs, and reduced repair costs. The cylindrical cavity  62  associated with nut pocket  60  or the slot cavity  84  in the bottom of the nut pocket  82  and corresponding structure either in the tie rod  72  or tie rod nut  86  provides an effective solution to tie rod bending without changing the mode of operation of the hydraulic hammer assembly  30  or changes to maintenance procedures. 
         [0047]    Although several described embodiments of forming an improved nut pocket and its associated tie rod and tie rod nut have been disclosed herein, numerous other variations may fall within the spirit and scope of this disclosure.

Summary:
A hydraulic hammer may include a power cell adapted to reciprocally drive a piston along an axis. The piston may, in turn, drive a hammer tool. A power cell and housing may be axially secured together by a plurality of tie rods and nuts secured to ends of the tie rods, and the housing may include open-sided pockets for accommodating the nuts. Each pocket may include a cavity that accommodates an extension of the tie rod or a specially formed nut to minimize movement of the nut in the direction of the pocket opening and thereby minimize bending of the tie rod. Engaging the back of the nut with the inside of the nut pocket further reduces the opportunity for the nut to rotate in the nut pocket as a result of force applied to the nut by the tie rod.