Patent Publication Number: US-8992158-B2

Title: Apparatus and method for reinforcement of a load bearing structure

Description:
TECHNICAL FIELD 
     The present disclosure relates to a reinforcement apparatus for a load bearing structure, in particular, a reinforcement apparatus for a box-beam-type structure configured to enhance rigid support against torsional loads while allowing external access to welded portions. 
     BACKGROUND 
     Implement carrying linkages for excavators and other similar machines may include multiple load bearing structures, such as a boom and/or a stick, which may be fabricated from a number of steel plates joined together by welds forming a box beam (also referred to as a box section). The box beam includes a hollow region enclosed by the steel plates. The box beam structures may be subjected to torsional loads during use of the machine, which may result in deformation and/or failure the box beam structure. 
     One solution to provide enhanced rigidity to a box beam structure subject to torsional loads is to weld baffle plates within the box beam at various locations. However, manufacturing a box beam structure having such internally welded baffle plates requires a significant amount of tooling, welding equipment, and process time. Additionally, because the baffle plates are internal to the structure, visual inspection and repair of the baffle plate welds require cutting into the box beam to access the baffle plates and their associated welds then repairing the box beam after the inspection and/or repair has been completed. 
     U.S. Pat. No. 5,152,659 discloses increasing torsional rigidity of an excavator boom by including a cylindrical cross-tie member penetrating through and welded to the side plates of the boom assembly. However, the cylindrical cross-tie member does not provide for diffusion of torsional loads or distribution of the loads into the boom structure. 
     U.S. Pat. No. 4,439,089 discloses a loader boom arm assembly having a pair of box section boom arms and a cross tube welded to the inboard sidewalls of each of the box section boom arms. In this configuration, the cross tube is not enclosed within a structure and simply provides a rigid connection between two box section boom arms. 
     Japanese Patent JP 59170332A discloses construction of a boom without reinforcing plates or partition walls by welding upper and lower intermediate brackets to the left- and right-handed boom cylinder brackets. However, this configuration is internal to the box section and would require removal of the boom cylinders and/or cutting into the box section to inspect and/or repair the welds. 
     The disclosed apparatus and method for reinforcing a load bearing structure is intended to overcome one or more of the problems set forth above and/or other problems of the prior art. 
     SUMMARY OF THE INVENTION 
     One aspect of the present disclosure is directed to a reinforcement apparatus for a load bearing structure. The reinforcement apparatus may include a tubular wall including a first end, a second end, a throat disposed between the first end and the second end, and a stress diffuser disposed between the throat and each of the first end and the second end The tubular wall may include a first thickness at the throat and a second thickness at each of the first and second ends. 
     Another aspect of the present disclosure is directed to a linkage assembly for a machine including a load bearing structure and a reinforcement apparatus. The load bearing structure may include a first sidewall including a first aperture and a second sidewall including a second aperture, the first sidewall being spaced apart from the second sidewall. The reinforcement apparatus being disposed between the first sidewall and the second sidewall includes a tubular wall including a first end, a second end, a throat portion disposed between the first end and the second end, and a stress diffuser portion disposed between the throat portion and each of the first end and the second end. The tubular wall may include a first dimension at the throat portion and a second dimension at each of the first and second ends, the first dimension being smaller than the second dimension. The first end is arranged in cooperation with the first aperture and the second end arranged in cooperation with the second aperture. 
     Yet another aspect of the present disclosure is directed to a method for reinforcing a load bearing structure including a first sidewall including a first aperture and a second sidewall including a second aperture. The method including the steps of placing a reinforcing apparatus between the first sidewall and the second sidewall, the reinforcing apparatus including a tubular wall including a first end and a second end, wherein the first end is placed in cooperation with the first aperture and the second end is placed in cooperation with the second aperture, joining the first end to the first sidewall, and joining the second end to the second sidewall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic side view of an excavator including a linkage including a boom in accordance with an exemplary embodiment of the present disclosure; 
         FIG. 2  is a perspective view of a boom including reinforcement apparatuses in accordance with an exemplary embodiment of the present disclosure; 
         FIG. 3  is a perspective view of a reinforcement apparatus included in the boom of  FIG. 2 ; 
         FIG. 4  is a side elevation view of the reinforcement apparatus of  FIG. 3 ; and 
         FIG. 5  is a detailed cross-section view of a portion of the tubular wall of the reinforcement apparatus of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an exemplary machine  100  having a body  102  mounted on an undercarriage  104 . Although in this exemplary embodiment the machine  100  is shown as an excavator, the machine  100  could be a backhoe, crane, loader or any similar machine. The machine  100  includes a linkage  106  having mating components, such as, for example, a boom  108 , a stick  110 , and a work implement  112 . The boom  108  may be connected to the body  102  at a pinned boom joint  114  that allows the boom  108  to pivot about the boom joint  114 . The stick  110  may be connected to the boom  108  at a pinned stick joint  116 , and the work implement  112  may be connected to stick  110  at a pinned work implement joint  118 . 
     Movement of the linkage  106  may be achieved by a series of hydraulic cylinder actuators  120 ,  122  and  124  coupled to the linkage  106  as is known in the art. For example, a boom actuator  120  may be coupled between the body  102  and the boom  108  by way of pinned boom actuator joints  126  and  128 . The boom actuator joints  126  and  128  are configured to allow the boom actuator  120  to pivot relative to the boom  108  and the body  102  during movement of the boom  108 . 
     A stick actuator  122  may be coupled between the boom  108  and the stick  110  by way of pinned stick actuator joints  130  and  132  to allow the stick actuator  122  to pivot relative to the boom  108  and stick  110  during movement of the stick  110 . Further, a work implement actuator  124  may be coupled between the stick  110  and mechanical links  134  coupled to the work implement  112 . The work implement actuator  124  may be connected to the stick  110  and mechanical links  134  at work implement actuator joints  136  and  138 , respectively. The mechanical links  134  may also include link joints  140 ,  142  attaching the mechanical links  134  to the work implement  112  and the stick  110 . 
     The work implement  112  may be used to engage the ground or other material in a digging action to move and/or remove earth or other material. Such digging action subjects the work implement  112  to forces which may be transmitted to the stick  110  and the boom  108 . Such forces may have a vector oriented laterally and/or offset to a long axis of the stick  110  and/or boom  108 , resulting in a torsional load being applied. 
       FIG. 2  shows a boom  108  including a top plate  144 , a bottom plate  146 , and a pair of spaced apart sidewalls  148 ,  150  attached to the top plate  144  and the bottom plate  146 , for example, by a welding process. The top plate  144 , bottom plate  146 , and sidewalls  148 ,  150  form a box-beam-type structure which defines a hollow chamber within the boom  108  which is enclosed by plates  144 ,  146 ,  148 ,  150 . 
     The boom  108  further includes a reinforcement apparatus  200 . The exemplary embodiment of  FIG. 2  depicts an L-shaped boom  108  including two reinforcement apparatus  200 , one reinforcement apparatus positioned in each leg of the boom  108 . Also, each reinforcement apparatus  200  may be positioned in line with the neutral axis of the boom  108 . Alternatively, the reinforcement apparatus  200  of the present disclosure may be positioned at any location within the boom  108  relative to the neutral axis, depending on the location requiring reinforcement. Further, although the reinforcement apparatuses are shown in  FIG. 2  as being the same size, it is contemplated that different reinforcement devices in a given load bearing structure may be of different sizes, depending on the application. For example, the forward reinforcement device shown in  FIG. 2  may be smaller than the rearward reinforcement device. The reinforcement apparatuses  200  of the present disclosure may be located at predetermined locations in a load bearing structure as determined, for example, by finite element analysis or other techniques known in the art. As should be apparent, the number, positioning, and size of reinforcement apparatuses  200  may be varied according to a particular application and may be applied to any box beam structure without departing from the scope of the present disclosure and the appended claims. 
     Referring to  FIGS. 3 and 4 , reinforcement device  200  includes a tubular wall  202  disposed about an axis  204 . The tubular wall  202  is configured to include a first end  206  and a second end  208 , with a throat portion  210  disposed between the first end  206  and the second end  208 . The tubular wall defines a channel  209  through the reinforcement device  200  from the first end  206  to the second end  208 . The throat portion  210  has an outside diameter D 1 . The first end  206  and the second end  208  each have an outside diameter D 2  that is greater than outside diameter D 1 . Moving outward laterally from the throat portion  210  in both directions, the tubular wall  202  flares outward radially about axis  204  forming a first stress diffuser portion  212  disposed between the throat  210  and the first end  206  and a second stress diffuser portion  214  disposed between the throat  210  and the second end  208 . The first and second stress diffuser portions  212 ,  214  may have a cross sectional profile of a curve, such as an arc, a parabola, or a hyperbola, giving the first and second stress diffuser portions  212 ,  214  a trumpet-shaped configuration. Alternatively, the first and second stress diffuser portions  212 ,  214  may be configured to have a linear cross sectional profile. 
     Reinforcement device  200  may also include a first rim  216  disposed about the circumference of the first end  206  and a second rim  218  disposed about the second end  208 . Each rim  216 ,  218  may include a bevel edge  220 ,  222 . The bevel edges  220 ,  222  are configured to cooperate with apertures  152 ,  154  in sidewalls  148 ,  150  to provide a weld bed between each rim  216 ,  218  and the respective sidewall  148 ,  150 . 
     The tubular wall  202  of reinforcement apparatus  200  may vary in thickness from the throat  210  outward laterally to the first and second ends  206 ,  208 , or may be of uniform thickness. A representative section of tubular wall  202 , symmetrical about axis  204  and centerline  224  is shown in  FIG. 5 . In the disclosed embodiment, tubular wall  202  has a first thickness T 1  at the throat  210 . First thickness T 1  may be uniform throughout the throat portion  210 . The thickness of the tubular wall  202  increases as the tubular wall  202  transitions outwardly from the throat  210  to the second stress diffuser portion  214  until the thickness T 2  is greatest at the second end  208 . In the exemplary embodiment second thickness T 2  is more than two times greater than first thickness T 1 . The trumpet-shaped configuration of first and second stress diffuser portions  212 ,  214  in combination with increasing wall thickness allows stresses produced by torsional loads to be diffused and distributed to the sidewalls  148 ,  150 . 
     The reinforcement apparatus  200  disclosed herein may be of unitary construction or may be constructed from a pair of symmetrical tube segments  226 ,  228  joined at the centerline  224  of the reinforcement apparatus  200 , as shown in  FIG. 3 . Each tube segment  226 ,  228  may have a profile as shown in  FIG. 5 , and as described previously herein. In the exemplary embodiment, the tube segments  226 ,  228  may be formed as a metal casting, for example carbon steel, aluminum, metal alloys, and the like. However, the tube segments may be formed by any acceptable metalworking method known in the art, such as rolling, forging, machining, spinning, and the like. Further, the reinforcement apparatus  200  may be formed by joining tube segments  226 ,  228  to a tubular member (not shown) therebetween, thereby forming an extended throat portion  210 . Referring again to  FIG. 3 , reinforcement apparatus  200  may be constructed by joining together tube segments  226 ,  228  by a weld  230 . 
     A load bearing structure, such as a boom  108  may be reinforced to provide enhanced rigidity against torsional loads by positioning a reinforcement apparatus  200  between the sidewalls  148 ,  150  such that the first end  206  and the second end  208  are in cooperation with the first and second apertures  152 ,  154 , respectively. First and second ends  206 ,  208  of reinforcement apparatus  200  may be joined to the sidewalls  148 ,  150  by welding processes known in the art. A weld may be disposed about the first and second apertures  152 ,  154  thereby joining the first and second ends  206 ,  208  to the first and second sidewalls  148 ,  150 , respectively. In an exemplary embodiment, first and second rims  216 ,  218  are welded to the first and second sidewalls  148 ,  150  at the first and second apertures  152 ,  154 , respectively. 
     Reinforcement apparatus  200  may be provided as a unitary piece. Alternatively, reinforcement apparatus may be provided as an assembly constructed from a pair of tube segments  226 ,  228  joined together by welding before positioning the reinforcement apparatus  200  in cooperation with first and second apertures  152 ,  154 . Alternatively, the first tube segment  226  may be positioned in cooperation with the first aperture  152  and welded in place. The second tube segment  228  may be positioned in cooperation with the second aperture  154  and welded in place. First tube segment  226  and second tube segment  228  then may be joined together by welding the throat portion  210  through the channel  209 . 
     INDUSTRIAL APPLICABILITY 
     The disclosed reinforcement apparatus may be applicable to reinforce any box-beam type load bearing structure against torsional loads. In particular, the present reinforcement apparatus may be applicable to a linkage assembly of a machine, for example a boom or a stick attached to an excavator, backhoe, crane, loader, or similar machine. The disclosed reinforcement apparatus may provide torsional rigidity to a load bearing structure without the need for internal baffle plates and associated welding. The disclosed reinforcement apparatus allows access to weld points from outside of the load bearing structure, facilitating manufacture, inspection, and repair of the load bearing structure without the need to access internal regions of the structure. 
     It will be apparent to those skilled in the art that various modifications can be made to the disclosed reinforcement device without departing from the scope of the invention. Other embodiments of the reinforcement device will be apparent to those skilled in the art from consideration of the specification and the practice of the reinforcement device disclosed herein. For example, although the disclosed reinforcement device has been described primarily for use with excavators and other machines, it is contemplated that a similar reinforcement device may be used with any box-beam type load bearing structure subject to torsional loads. Additionally, although the disclosed reinforcement apparatus has been describes as including a pair of symmetrical cast wall segments welded together about a centerline, it is also contemplated that the reinforcement device may be formed as a unitary piece. It is intended that the specification and examples be considered exemplary only, with a true scope being indicated by the following claims and their equivalents.