Patent Publication Number: US-2018030686-A1

Title: Boom assembly of machine

Description:
TECHNICAL FIELD 
     The present disclosure relates to a boom assembly of a machine and more particularly to a load carrying member of the boom assembly. 
     BACKGROUND 
     Machines, such as hydraulic excavators and hydraulic shovels, perform different works at a work site. Among the different works performed, the machines are employed to raise load from a loading location and dump the load at a dumping location. For the purpose of handling such load, the machines employ a work tool, such as a bucket, coupled to a boom assembly via a stick of the machine. The boom assembly includes a boom coupled to the stick and multiple hydraulic actuators to enable pivotal movement of the stick. Further, the boom is pivotally coupled to a frame of the machine to allow travel of the work tool to a desired height or depth. Typically, the boom is formed from steel. Although steel provides structural stability to the boom, steel renders the boom heavy. In cases where the machine includes a long boom, the weight of the boom would be higher than desired. In addition, such long boom may often be subjected to dipping, where the frame of the machine tends to lift from ground surface when the boom lifts heavy loads. As such, weight of the boom becomes detrimental to operation of the machine, thereby restricting optimization of boom design. 
     Chinese Patent Application Number 103332610 describes a connection structure of an end part of a cantilever, which is made of carbon-fiber composite materials. The connection structure is formed by successive adhesion of metal and carbon-fiber, where a metal internal layer is the inner part, a metal outside plate is the outer part, and a carbon-fiber enhanced layer is arranged between the inner part and the outer part. The metal internal layer and the metal outside plate are connected by welding, and form a sandwich structure. The metal inner layer includes a long metal tube, two short metal tubes, and a frame. One end of the frame is provided with a square component, and the other end of the frame is provided with a U-shaped connector. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect of the present disclosure, a load carrying member for a machine is provided. The load carrying member includes an outer shell and an inner shell disposed within the outer shell. The inner shell is pre-stressed. The load carrying member also includes a polymer composite disposed between an outer surface of the inner shell and an inner surface of the outer shell. 
     In another aspect of the present disclosure, a machine is provided. The machine includes a frame and a boom assembly coupled to the frame. The boom assembly includes a work tool and a stick coupled to the work tool. The boom assembly also includes a load carrying member having a first end coupled to the frame and a second end coupled to the stick. Further, the load carrying member includes an outer shell and an inner shell disposed within the outer shell. The inner shell is pre-stressed. The load carrying member also includes a polymer composite disposed between an outer surface of the inner shell and an inner surface of the outer shell. 
     In yet another aspect of the present disclosure, a boom assembly of a hydraulic excavator machine is provided. The boom assembly includes a work tool and a stick coupled to the work tool. The boom assembly also includes a load carrying member having a first end coupled to the frame and a second end coupled to the stick. Further, the load carrying member includes an outer shell and an inner shell disposed within the outer shell. The inner shell is pre-stressed. The load carrying member also includes a polymer composite disposed between an outer surface of the inner shell and an inner surface of the outer shell. 
     Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  a side view of a machine equipped with a boom assembly having a load carrying member, according to an embodiment of the present disclosure; 
         FIG. 2  is the side view of the machine showing a partial cross-section view of the load carrying member having an inner tube disposed in an outer shell of the load carrying member, according to an embodiment of the present disclosure; 
         FIG. 3  is the side view of the machine showing a partial cross-section view of a load carrying member having the inner tube disposed in the outer shell of the load carrying member, according to another embodiment of the present disclosure; and 
         FIG. 4  is a schematic diagram of the load carrying member of  FIG. 3  showing different curvatures of the inner shell within the outer shell during loading operation, according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts. Moreover, references to various elements described herein, are made collectively or individually when there may be more than one element of the same type. However, such references are merely exemplary in nature. It may be noted that any reference to elements in the singular may also be construed to relate to the plural and vice-versa without limiting the scope of the disclosure to the exact number or type of such elements unless set forth explicitly in the appended claims. 
       FIG. 1  illustrates a side view of a machine  100  equipped with a boom assembly  102 , according to an embodiment of the present disclosure. In the preferred embodiment, the machine  100  is a hydraulic excavator. However, in some embodiments, the machine  100  may be embodied as a hydraulic mining shovel, a material handler, or a crane. The boom assembly  102  includes a load carrying member  104  and a work tool  108 . The load carrying member  104  is pivotally connected to a frame  110  of the machine  100  and the work tool  108  is pivotally connected to the load carrying member  104 . A boom  103  and a stick  106  constitute the load carrying member  104  of the machine  100 . Load carried by the work tool  108  is distributed between the boom  103  and the stick  106 . 
     The machine  100  also includes a drive unit  112 , such as tracks and wheels, for propelling the machine  100  over a ground surface ‘G’, a power source  114  to power the boom assembly  102  and the drive unit  112 , and an operator cabin  116  for hosting user interface devices that aid in controlling the boom assembly  102  and the drive unit  112 . The power source  114  may embody an engine, such as a diesel engine, a gasoline engine, a gaseous fuel-powered engine, or any other type of combustion engine known in the art. The power source  114  may alternatively embody a non-combustion source of power, such as a fuel cell and a power storage device. The power source  114  may produce mechanical or electrical power output that may then be converted to hydraulic power for moving the boom assembly  102  and the work tool  108 . 
     Further, a movement of the work tool  108  includes raising and lowering the load carrying member  104  with respect to the frame  110 , moving the stick  106  inward and outward with respect to the operator cabin  116 , and rotating the work tool  108  relative to the stick  106 . The load carrying member  104  may be raised and lowered by a first hydraulic actuator  120 . The stick  106  may be moved toward and outward with respect to the operator cabin  116  by a second hydraulic actuator  122 . In addition, a third hydraulic actuator  124  is used to curl and uncurl the work tool  108  relative to the stick  106 . Furthermore, the frame  110  and the boom assembly  102  may be rotated about a vertical axis ‘V’, with respect to the drive unit  112 , by a fourth hydraulic actuator  126 , such as a hydraulic motor. 
       FIG. 2  illustrates a partial cross-section view of the machine  100 . Specifically,  FIG. 2  illustrates a cross-section of the load carrying member  104  of the machine  100 , according to one embodiment of the present disclosure. The load carrying member  104  includes a first end  202  and a second end  204 . Each of the first end  202  and the second end  204  includes an attachment fixture configured to couple the load carrying member  104  to the frame  110  and the stick  106 , respectively. As illustrated in  FIG. 2 , the first end  202  includes a first attachment fixture  206  and the second end  204  includes a second attachment fixture  208 . The first attachment fixture  206  and the second attachment fixture  208  can be embodied as, but not limited to, brackets that aid in coupling of the load carrying member  104  to the frame  110  and the stick  106 , respectively. 
     The load carrying member  104  includes an outer shell  210 . In one embodiment, the cross-section of the outer shell  210  can be a rectangle. In other embodiments, the cross-section of the outer shell  210  can include one of a polygon, a circle, and an ellipse. In order to have better structural stability, the outer shell  210  needs to be formed from materials which provide better strength. Accordingly, in an example, material of the outer shell  210  may include, but not limited to, at least one of high speed steel (HSS) and carbon fibers. The first end  202  and the second end  204  correspond to a first end and a second end of the outer shell  210 . As such, the first attachment fixture  206  and the second attachment fixture  208  are provided at the ends of the outer shell  210 . 
     The load carrying member  104  further includes an inner shell  212  disposed within the outer shell  210 . Such configuration of the inner shell  212  disposed within the outer shell  210  is illustrated with respect to the boom  103  only for the purpose of description and should not be construed as a limitation. In one embodiment, the inner shell  212  and the outer shell  210  configuration can be implemented in the stick  106 . In another embodiment, the inner shell  212  and the outer shell  210  configuration can be implemented in both the stick  106  and the boom  103 . Further, it will be appreciated that the inner shell  212  and the outer shell  210  configuration described in the present disclosure can be implemented in any front structures of the machine  100  that are capable of extending away from the frame  110  of the machine  100 . 
     In one embodiment, the cross-section of the inner shell  212  can be a circle. In other embodiments, the cross-section of the inner shell  212  can include one of a rectangle, a polygon, and an ellipse. The first attachment fixture  206  and the second attachment fixture  208  can be configured to couple to ends of the inner shell  212 . In one embodiment, the first attachment fixture  206  and the second attachment fixture  208  can be embodied as metal plates configured to couple to the ends of the inner shell  212 . In the preferred embodiment, the inner shell  212  is pre-stressed prior to introducing the inner shell  212  into the outer shell  210 . Selection of materials for the inner shell  212  and pre-stressing process is performed in a manner, such that the inner shell  212  acquires a spring rate post the pre-stressing process. As such, the inner shell  212  would be capable of springing back to its original condition, which is straight condition, when the inner shell  212  is subjected to bending loads. In an example, the inner shell  212  may be composed of shape memory polymers. In another example, material disposed between the inner shell  212  and the outer shell  210  can be a shape changing fluid, such as a magnetorheological fluid (MR fluid). 
     In one embodiment, length of the inner shell  212  can be greater than a length of the outer shell  210 . In such a condition, the inner shell  212  is bent at a predetermined curvature when the inner shell  212  is disposed within the outer shell  210  and between the first attachment fixture  206  and the second attachment fixture  208 . In one case, the inner shell  212  can be bent in a manner, such that the inner shell  212  is concave towards the work tool  108 , as shown in  FIG. 2 . The load carrying member  104  further includes a polymer composite  218  disposed between an outer surface  214  of the inner shell  212  and an inner surface  216  of the outer shell  210 , as shown in  FIG. 2 . In an example, the polymer composite  218  may be a Sandwich Plate Steel (SPS) polymer or a thermosetting polymer. The polymer composite  218  can be heated to a predefined temperature and can be filled in a cavity formed between the outer surface  214  of the inner shell  212  and the inner surface  216  of the outer shell  210 . Subsequently, the polymer composite  218  is allowed to settle and cool down. The polymer composite  218  provides a stiffness required for the operation of the load carrying member  104 . 
       FIG. 3  illustrates a cross-section of the load carrying member  104  of the machine  100 , according to another embodiment of the present disclosure. As illustrated in  FIG. 3 , the first end  202  of the load carrying member  104  includes a first attachment fixture  302  and the second end  204  of the load carrying member  104  includes a second attachment fixture  304 . The first attachment fixture  302  and the second attachment fixture  304  can be embodied as brackets or metal plates to support the load carrying member  104 . The load carrying member  104  includes an outer shell  306  and an inner shell  308  disposed within the outer shell  306 . The inner shell  308  is bent in a manner, such that the inner shell  212  is convex towards the work tool  108 , as shown in  FIG. 3 . It should be understood that the first attachment fixture  302  and the second attachment fixture  304  of  FIG. 3  correspond to the first attachment fixture  206  and the second attachment fixture  208  of  FIG. 2 , but with few variations to accommodate the inner shell  308 . In this embodiment as well, the polymer composite  218  is disposed between an outer surface  310  of the inner shell  308  and an inner surface  312  of the outer shell  306 , as shown in  FIG. 3 . 
     Various embodiments disclosed herein are to be taken in the illustrative and explanatory sense, and should in no way be construed as limiting of the present disclosure. 
     INDUSTRIAL APPLICABILITY 
     A schematic diagram of the load carrying member  104  in operation, according to an embodiment of the present disclosure, is illustrated in  FIG. 4 . The machine  100  is deployed at a worksite  400  for digging and loading operation.  FIG. 4  illustrates three exemplary positions of the load carrying member  104 , such as a first position ‘P 1 ’, a second position ‘P 2 ’, and a third position ‘P 3 ’, during raising of load ‘L’ from a depth ‘D’. 
     The load carrying member  104  of the hydraulic excavator is embodied as a long extending boom. When the load carrying member  104  lifts the load ‘L’ from the first position ‘P 1 ’ to the second position ‘P 2 ’, the inner shell  212  is subjected to bending loads owing to the length of the load carrying member  104 . In such a scenario, the inner shell  212  bends due to the load ‘L’ and force acting on the work tool  108  by virtue of gravity. The curvature of the bend is towards the work tool  108 , i.e., convex towards the work tool  108 , as shown in  FIG. 4 . However, the inner shell  212  develops a tendency to return to its original condition, which is the straight condition. As the load ‘L’ is being raised by the machine  100  from the depth ‘D’, bending load acting on the inner shell  212  decreases gradually. Accordingly, the curvature of the inner shell  212  decreases while the load carrying member  104  moves from the first position ‘P 1 ’ to the third position ‘P 3 ’, as shown in  FIG. 4 . Similarly, in cases where the load carrying member  104  is implemented with the inner shell  308  of  FIG. 3 , the curvature of the inner shell  308  of  FIG. 3  decreases while the load carrying member  104  moves from the first position ‘P 1 ’ to the third position ‘P 3 ’. 
     Such configurations of the load carrying member  104 , particularly the inclusion of the inner shell  212 , minimizes efforts to lift the load ‘L’, which is otherwise high. In addition, since the load carrying member  104  is embodied as shell composed of thin steel or carbon fiber, overall weight of the load carrying member  104  is minimized. Furthermore, owing to bending ability of the inner shell  212 , the machine  100  may encounter minimum or no dipping. As such, the operation of the machine  100  may be enhanced. The load carrying member  104  of the present subject matter also provides better visibility to an operator around the machine  100 . 
     While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.