Patent Publication Number: US-2009223093-A1

Title: Support Arm for a Work Machine

Description:
The invention pertains to a support arm for a work machine, for example a jib or boom on the work equipment of a excavator, with at least one wall having at least one plate-shaped element. 
     BACKGROUND 
     Work machines, both movable machines such as excavators, wheel loaders, tractors, telescopic handlers, or other such machines as well as stationary machines such as cranes have support arms of different types that, individually or in combination, bear or move a work tool, a support, or other components and that connect these components to the work machine. These support arms of varying length and design are often connected via a hinge to the drives moving the arm and to the machine, the work tool, the support, or other components. The support arms generally consist of a box-shaped cross-section that is formed by walls, for example upper and lower flanges, as well as by side walls. There are location points for pin supports welded onto or in the walls which connect the support arms to each other, the support arms to the drives, the support arms to the work machine, and the support arms to the work tool, the support, or other components. The walls are usually a welded constructions built of homogeneous plates of different thicknesses, whereby their contour of the walls along their length are dimensioned appropriately for the stresses expected to be placed on the component. 
     With this well-known welded support arm construction, it is possible to realize a support arm with the lowest possible intrinsic mass while still accounting for the load curve of the particular support arm, but manufacturing such a support arm is cost-intensive due to the high number of welding seams required for the connection of plates of different thicknesses. In addition, the production as well as the inspection of such welding seams is complex due to the high dynamic load placed on a work machine. 
     A welded cross-section for backhoe and loading shovel tools for an excavator is provided in DE 102 57 041 B3 in which the side walls, which have a uniform wall thickness, are equipped with upper and lower profile-reinforced end sections that form the corner sections of the upper and lower flanges located between the end sections. In this case, the end sections are formed by separate metal plates adapted to the particular contour of the tools that are connected by a weld to the corresponding side walls, which are thinner. The side walls connected to the profile-reinforced end sections are equipped with saddle rests for mounting the cylinder locating points. Such a cross-section is relatively complicated to manufacture due to the necessity of producing the additional profile-reinforced end sections. 
     SUMMARY OF THE INVENTION 
     The task of the invention is to produce a support arm of the type described that follows the component stresses to be expected to a high degree, has the lowest possible intrinsic mass, and can be manufactured with a minimum of effort. 
     This task is accomplished by the invention of a support arm of the type described at the beginning in that the at least one plate-shaped element, which is adapted to the component stresses to be expected, has at least one planar cut-out, whereby at least one cut-out is covered by a thin-walled cover element opposite the plate-shaped element. 
     Advantageously, the at least one wall is made of a single-piece plate-shaped element, but in an additional design it is possible for the at least one wall to be comprised of several plate-shaped elements that are welded together. It is preferable for the at least one plate-shaped element to have a uniform wall thickness. To enable ideal adaptation to the component stresses to be expected, it is advantageous to design the corresponding plate-shaped element with several cut-outs. The cut-outs can be designed according to the load curve to be expected. 
     Therefore a support arm with walls of the type described is suggested that is adapted to a high degree to the load curve expected for the component due to the cut-out(s) that can be designed accordingly. The cut-outs are correspondingly intended for those areas of the component where low stresses are expected. They can be manufactured without any problem and in any shape desired in the plate-shaped element. Due to the planar cut-outs, the intrinsic mass of the support arm is relatively low. 
     Depending on the requirements, it can be advantageous not to cover all cut-outs with thin-walled cover elements. It is advantageous to weld the particular cover element circumferentially around the edge of the cut-out. A weld can be produced automatically and economically since the necessary welding seam is small in size and the welding seams are all closed welding seams matching the contour of the cut-outs. Connection technologies other than welding are also possible, of course. 
     Depending on design of the particular support arm, the at least one cover element can be located on the outside or inside of the plate-shaped element, or located in the cut-out of the plate-shaped element itself. 
     Advantageously, the support arm has a box-shaped cross-section with several walls, whereby at least one wall has a plate-shaped cross-section manufactured in the manner described. 
     The support arm can be part of the work equipment of a work machine and serve to move and bear a work tool. On the other hand, support arm can also at least be used as a support or to carry other components. 
     The support arm can be the jib or boom of an excavator, whereby the box-shaped cross-section of the support arm has an upper flange, a lower flange, and side walls, and in which at least one flange and/or at least one side wall has a plate-shaped element of the type described. 
     It is advantageous to design the contour of the side walls along their length for the component stresses expected. The support arm can be located on the upper carriage or the lower carriage of the excavator. 
     Advantageously, the upper and the lower flanges are located between the side walls of the support arm. When this design is used, then it is also advantageous to integrate saddle bearings for cylinders and linkages into the side walls. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described in more detail in the following using examples based on the drawing. The drawings show the following: 
         FIG. 1  A general arrangement drawing of a work machine in the form of an excavator 
         FIG. 2  Perspective diagram of a support arm designed according to the invention 
       
         FIG. 3 to 5 
           
           
             
               Partial cross-section of the support arm according to  FIG. 2  in various designs. 
             
           
         
      
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an example of a work machine in the form of a machine generally referred to as an excavator and labeled here with  1 . The following description of the design of a support arm according to the invention can be realized in general for any type of mobile or stationary work machine; excavator  1  shown in  FIG. 1  is only an example of such a machine. 
     Excavator  1  has one lower carriage  2  and one upper carriage  3 , and is equipped with a work tool in the form of a shovel  4 . This shovel  4  is connected by work equipment consisting of several support arms  5  to excavator  1 , and in particular to the upper carriage  3  of the same excavator. Other support arms, either individually or in combination, can also be connected to the lower carriage  2 , of course, but this is not shown in detail in the drawing. 
     The individual support arms  5  of the work equipment of the excavator are connected by pin supports  6  to each other and to the hydraulic cylinders  7  moving the arms as well as to the upper carriage  3  and the shovel  4 . By adjusting the hydraulic cylinder  7 , the support arms  5 , and therefore the work tool such as shovel  4  shown in the example, can be brought to the desired working position. 
     The essential item is now the design of the support arms  5  that are shown in  FIGS. 2 to 5 . 
     Each support arm  5  in this sample design consists of a box-shaped cross-section with one upper flange  8 , a lower flange  9  and two side walls  10  connected to the flanges  8 ,  9 . These side walls  10  are dimensioned appropriately along the length of their outer contour to handle the expected component stresses. 
     To accomplish this, it is intended in the example according to  FIG. 2  that the particular side wall  10  consists of a single plate-shaped element  11  of uniform wall thickness, preferably a thick metal plate, that has several planar cut-outs  12 . These cut-outs  12  are designed differently in terms of their shape so that their shape is adapted to the component stresses to be expected. The corresponding side wall  10  is preferably made of a single-piece plate-shaped element  11 , but the side wall  10  can be divided into several pieces (with the same wall thickness) for handling reasons if the components are too long, but is not desirable due to adaptation to the component stresses. 
     In the design shown in  FIG. 2 , only the two side walls  10  consist of a plate-shaped element  11  with cut-outs  12 , and the upper flange  8  and the lower flange  9  are located between the two side walls  10  and are welded to the side walls  10 . In such a design, it is advantageous to place bearing points  13  for pin supports (for hydraulic cylinders and linkages) on the side walls  10 . 
     The support arm  5  shown in  FIG. 2  is only one example; the shapes of the support arms  5  are naturally different depending on the actual function of the particular support arm (see also the different designs of the support arms  5  in  FIG. 1 ). It is essential though that the walls are made of at least one plate-shaped element  11  with a uniform wall thickness and with at least one cut-out  12 , of which at least one cut-out is closed off by a thin-walled covering plate  14  ( FIG. 3 to 5 ) with an opposing plate-shaped element  11 . In contrast to the design shown in  FIG. 2 , instead of the side walls  10 , the flanges  8 ,  9  can also or only consists of plate-shaped elements  11  with at least one cut-out  12  and at least one thin-walled cover plate  14 . In general, it is also possible for only one side wall  10  or only one flange  8 ,  9  to consist of at least one plate-shaped element  11  with at least one cut-out  12  and at least one thin-walled cover plate. 
     As can be seen in  FIGS. 3 to 5 , one or more of the cut-outs  12  are covered by a cover element  14 . This cover element  14  preferably consists of a thin-walled plate opposite the plate-shaped element  11 , and its outer contour can match the contour of the corresponding cut-outs  12  and is preferably connected circumferentially around the edge of the cut-outs  12 , for example by welding. In doing so, the cover element  14  can be located and connected to the outside ( FIG. 3 ), inside ( FIG. 4 ), or even in the contour of the cut-out ( FIG. 5 ) on the plate-shaped element  11 . Depending on the design of the support arm  5 , all or only some of the cut-outs  12  can be equipped with a cover element  14 , but at least one must be equipped with a cover element  14 . These cover elements  14  made of thin-walled plating only contribute minimally to the load bearing capacity of the support arm  5 . They can be manufactured automatically, economically, and without complicated post-welding work by connected them to the plate-shaped element  11  using thin, closed welding seams. 
     Of course, the invention is not limited to the design examples shown. Other designs are possible using the same basic idea. For example, a support arm  5  according to the invention can not only be used as part of the working equipment of an excavator, but in general for any support arm of any type of work machine. These support arms can be connected to any part of the machine and can carry work tools as well as supports or other components even when these are not shown in the drawings. Additional designs according to the invention can also form support arms with walls with plate-shaped elements of the type described but without a box-shaped cross-section.