Patent Publication Number: US-8974172-B2

Title: Boom assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119 of Japanese Application No. 2011-153842, filed on Jul. 12, 2011, the disclosure of which is expressly incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a boom assembly in a working vehicle, such as a front loader. 
     2. Description of Related Art 
     In a boom assembly of a front loader, for example, a front boom portion and a rear boom portion are curved at a center portion in a boom&#39;s length direction and are connected in a bowed shape protruding on an upper side. A left-right pair of side plates is fixedly positioned on both a left and right side of a rear portion side of the front boom portion and a front portion side of the rear boom portion. A central connection plate is attached between the pair of side plates, and a rear portion side of a cover plate on the front boom portion and a front portion side of a cover plate on the rear boom portion are connected thereby. A pivoting support for a working tool cylinder used to move a working tool connected to a foremost portion of a front boom assembly body is provided on a front side of a top portion on each of the left and right side plates. 
     In this type of boom assembly, in order to increase the strength in the area around the pivoting support for a working tool cylinder where stress is concentrated during excavation work and the like, it is possible to add a reinforcement plate to the area around the pivoting support. However, this negatively affects the appearance of the working vehicle. In a conventional boom assembly, the left and right side plates enable inclusion of the pivoting support for the working tool cylinder, and the thickness of the side plates is increased in an attempt to ensure strength and improve an external appearance (see, for example, Related Art 1). 
     [Related Art 1] Japanese Patent Laid-open Publication No. 2007-262689 
     SUMMARY OF THE INVENTION 
     Accordingly, due to the left and right side plates being thick in the conventional method, costs have increased and the weight of the boom assembly has increased. In view of the above circumstances, the present invention has as its advantage to provide a boom assembly capable of ensuring strength in the area around the pivoting support for the working tool cylinder and, moreover, to reduce costs and weight. 
     In order to achieve the advantage of the present invention, bow-shaped booms  27  are each composed of a rear boom portion  27 B and a front boom portion  27 A, the rear boom portion  27 B extending horizontally from a vehicle body and the front boom portion  27 A extending downward at a central portion of the boom  27  when a working tool  28  is positioned in contact with the ground. The front boom portion  27 A and the rear boom portion  27 B are configured from cover plates  62   a  and  62   b , and from left and right lateral plates  61   a  and  61   b . The left and right lateral plates  61   a  of the front boom portion  27 A and the left and right lateral plates  61   b  of the rear boom portion  27 B are each connected by a pair of side plates  58  having a boom cylinder pivoting support  70  and a working tool cylinder pivoting support  71 . In addition, the cover plate  62   a  of the front boom portion  27 A, the cover plate  62   b  of the rear boom portion  27 B, and the side plates  58  are integrally connected by a central connection plate  57  positioned between the left-right pair of side plates  58 . The central connection plate  57  is formed with a connection plate projection  84  projecting from a front portion attached to the rear portion of the cover plate  62   a  of the front boom portion  27 A toward a midway portion so as to approach the working tool pivoting support  71 . 
     The connection plate projection  84  is formed to project in a peaked shape so as to vertically overlap behind the pivoting support  71  in a state where the booms  27  are lowered and the working tool  28  is in contact with the ground. The central connection plate  57  includes a front attachment portion  75 , a front inclined portion  77 , a rear inclined portion  78 , an extended projection portion  80 , and a rear attachment portion  81 . The front attachment portion  75  overlaps with and is attached to the rear portion of the cover plate  62   a . The front inclined portion  77  curves upward from the front attachment portion  75  and inclines in a projection so as to approach the pivoting support  71  at a distance from the rear portion side of the cover plate  62   a  of the front boom portion  27 A. The rear inclined portion  78  inclines downward from the projecting end portion of the front inclined portion  77 . The extended projection portion  80  projects by extending to the rear from the lower end portion of the rear inclined portion  78 . The rear attachment portion  81  projects to the rear from the extended projection portion  80  and overlaps with and is attached to the front portion of the cover plate  62   b  of the rear boom portion  27 B. The connection plate projection  84  is configured from the front inclined portion  77  and the rear inclined portion  78 . 
     Strength in an area around boss portions of the pivoting support  71  for the working tool cylinder can be effectively increased by the connection plate projection  84 . Thus, in addition to ensuring adequate strength in the area around the pivoting support  71 , it becomes possible to form the left and right side plates  58  with a thin plate thickness. In this regard, it becomes possible to achieve a reduction in costs, and the booms  27  may be made cheaper and lighter. During excavation work and the like in which the booms  27  are lowered and the working tool is in contact with the ground, and for which there is a risk of putting the greatest stress on an area around the pivoting support  71  for the working tool cylinder, the connection plate projection  84  is overlapped from behind on the pivoting support  71  for the working tool cylinder, and thus the area around the pivoting support  71  for the working tool cylinder can be extremely effectively reinforced with the connection plate projection  84  and the strength in the area around the pivoting support  71  for the working tool cylinder can be yet further improved. 
     The central connection plate  57  has the front attachment portion  75 , the front inclined portion  77 , the rear inclined portion  78 , the extended projection portion  80 , and the rear attachment portion  81 , and thus rigidity of the connection portions on the rear portion side of the front boom portion  27 A and the front portion side of the rear boom portion  27 B can be increased. In addition, there is no need for the rear portion side of the front boom portion  27 A and the front portion side of the rear boom portion  27 B to be formed to be bulky, nor for the central connection plate  57 , the side plates  58 , and the like to be formed to be bulky. In this regard as well, structural materials for the boom assembly can be conserved and the boom assembly may be manufactured at a low cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein: 
         FIG. 1  is a lateral cross-sectional view of a central portion of a boom assembly according to an embodiment of the present invention; 
         FIG. 2  is a lateral view of the boom assembly; 
         FIG. 3  is a view of the same from the perspective of an arrow A in  FIG. 2 ; and 
         FIG. 4  is a lateral view of a tractor with a front loader mounted thereto. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description is taken with the drawings making apparent to those skilled in the art how the forms of the present invention may be embodied in practice. 
     Hereinafter, exemplary embodiments of the present invention are described with reference to the drawings. In  FIG. 4 ,  1  is a tractor (moving vehicle) and  2  is a front loader (loader) detachably mounted to a front portion of the tractor  1 . The tractor  1  includes a left-right pair of front wheels  3  and a left-right pair of rear wheels  4 , and further includes a hood  7  in the front portion covering an engine, a radiator, and the like. 
     A loader attachment frame  9  is included on the tractor  1  for detachably mounting the front loader  2 . The loader attachment frame  9  is provided with one left-right pair each of support platforms  11  provided so as to project outward in left and right directions from the vehicle body side of the tractor  1 , and main frames  12  provided upright on the support platforms  11 . 
     The front loader  2  includes one left-right pair each of side frames  15 , the booms  27 , boom cylinders  29 , and bucket (working tool) cylinders  30 . The front loader  2  further includes a single bucket (working tool)  28 , and the left and right side frames  15  are detachably attached to the left and right main frames  12 , respectively. In  FIGS. 1-4 , a pair of the left and right booms  27  is included positioned on both the left and right sides of the hood  7 . The left and right booms  27  are mutually connected at the front portion side thereof by a connecting member  54  having a tubular shape and the like. 
     Each of the left and right booms  27  is supported by and connected at the base end side (rear end side) thereof by a pivot  55  so as to be rotatable about a left-right directional axis on the upper portion of the side frame  15 . The booms  27  are thus vertically swingable. The left-right pair of boom cylinders  29  formed from double-action hydraulic cylinders is mounted spanning a midway portion in a length direction of each of the left and right booms  27  and a midway portion in a vertical direction of each of the left and right side frames  15 . The left and right booms  27  are vertically swingable through the expansion and contraction of the left and right boom cylinders  29 . 
     A foremost end (front end) of each of the left and right booms  27  is supported by and connected to a lower portion on the back face of the bucket (working tool)  28  via a pivot  56 . The left-right pair of bucket cylinders (working tool cylinders)  30  formed from double-action hydraulic cylinders is mounted between the back surface of the bucket  28  and left and right side plates  58  which will be discussed hereafter. The bucket  28  is swingable (capable of scooping/dumping motions) through the expansion and contraction of the bucket cylinders  30 . 
     Each of the left and right booms  27  is formed in a bowed shape curving at a central portion in the boom length direction and protruding on an upper side. In addition, each of the left and right booms  27  is formed such that the vertical width becomes gradually broader toward a central portion in the length direction from front and rear end portions. The booms  27  are each primarily configured from the front boom portion  27 A on the front side of the central portion in the length direction, the rear boom portion  27 B on the rear side of the central portion in the length direction, the central connection plate  57  connecting the front boom portion  27 A and the rear boom portion  27 B at the center in the length direction of each of the booms  27 , and the side plates  58  positioned on both the left and right sides of the center in the length direction of each of the booms  27 . 
     The front boom portion  27 A is configured from a main body  59   a  and a bottom plate  60   a , and the rear boom portion  27 B is configured from a main body  59   b  and a bottom plate  60   b . The main body  59   a  and the main body  59   b  are formed with roughly the same shape and the bottom plate  60   a  and the bottom plate  60   b  have roughly the same shape. Components may thus be made multipurpose. The main body  59   a  of the front boom portion  27 A has a squared U shape in cross-section having an open bottom formed by the left-right pair of lateral plates  61   a  and the cover plate  62   a  connecting the upper end portions of the left and right lateral plates  61   a . The main body  59   b  of the rear boom portion  27 B has a squared U shape in cross-section having an open bottom formed by the left-right pair of lateral plates  61   b  and the cover plate  62   b  connecting the upper end portions of the left and right lateral plates  61   b . The main body  59   a  and the main body  59   b  have a curved shape with a marked upward protrusion as viewed from the side. 
     The front and rear main bodies  59   a  and  59   b  are formed by flexion of a single plate member to have a squared U shape in cross-section and, after the bending work into a squared U shape, the front and rear main bodies  59   a  and  59   b  are worked through bending into a curved shape with an upward protrusion. The front boom portion  27 A and the rear boom portion  27 B are positioned inverted front to back so as to form a front-back symmetrical shape. The front boom portion  27 A and the rear boom portion  27 B are connected by the central connection plate  57 . A pivoting support  63  is provided at the front end side of the front boom portion  27 A, the pivoting support  63  formed by a tubular body penetrating the left and right lateral plates  61   a  and running therebetween, and additionally fixed thereto by welding. The bucket  28  is supported by and rotatably connected to the pivoting support  63  by the pivot  56 . 
     A pivoting support  64  is provided at the rear end side of the rear boom portion  27 B, the pivoting support  64  being formed by a tubular body penetrating the left and right lateral plates  61   b  and running therebetween and additionally fixed thereto by welding. The pivoting support  64  is pivotingly supported on the side frames  15  by the pivot  55  and the booms  27  are connected to the side frames  15  so as to be vertically rotatable. The front and rear bottom plates  60   a  and  60   b  are configured from flat plates, and are disposed below the cover plates  62   a  and  62   b  and between the right and left lateral plates  61   a  and  61   b . After the bending work on the main bodies  59   a  and  59   b , the left and right side edge portions of the bottom plates  60   a  and  60   b  are fixed by welding to an inner surface of the left and right lateral plates  61   a  and  61   b , respectively. The rear end portion of the bottom plate  60   a  and the front end portion of the bottom plate  60   b  are vertically overlaid and welded to one another. 
     In order to facilitate insertion of a welding torch between the lateral plates  61   a  and  61   b  at the center in the length direction of the booms  27  when welding the bottom plates  60   a  and  60   b  to the lateral plates  61   a  and  61   b , a cutaway  69  is formed on the front and rear main bodies  59   a  and  59   b  on an upper portion side at the center in the length direction of the booms  27 . The bottom plates  60   a  and  60   b  are welded from below to the lateral plates  61   a  and  61   b , beginning at each front and rear end portion side of the booms  27  and running to the midway portion in the length direction of the booms  27 . The bottom plates  60   a  and  60   b  are welded from above to the lateral plates  61   a  and  61   b  at the center in the length direction of the booms  27 . 
     After the bottom plates  60   a  and  60   b  have been fixed by welding to the front and rear main bodies  59   a  and  59   b , respectively, the bottom plates  60   a  and  60   b  are matched up at the center in the length direction of the booms  27 . The front and rear bottom plates  60   a  and  60   b  are welded to one another. In addition, the central connection plate  57  and the left and right side plates  58  are welded to the front and rear boom portions  27 A and  27 B and are thereby connected to one another. The central connection plate  57  and the left and right side plates  58  are welded together and are thereby connected. 
     The left and right side plates  58  are provided so as to span the front and rear lateral plates  61   a  and  61   b  at the center in the length direction of the booms  27 , and are fixedly positioned on both the left and right sides of the rear end side of the front boom portion  27 A and the front end side of the rear boom portion  27 B. The cylinder pivoting support  70  for the boom cylinder is provided at a rear side of a lower end portion of each of the left and right side plates  58 . The cylinder pivoting support  70  has pivoting support bosses welded to the exterior surfaces of each of the left and right side plates  58 . 
     The cylinder pivoting support  71  for the working tool cylinder is provided on a front side of the upper end portion of each of the left and right side plates  58 . The cylinder pivoting support  71  is positioned at a distance from the front boom portion  27 A such that the cylinder pivoting support  71  is positioned above the rear portion side of the cover plate  62   a  of the front boom portion  27 A in a state where the booms  27  are lowered and the working tool  28  is in contact with the ground (the state shown in  FIG. 4 ). Pivoting support bosses are then welded to the exterior surfaces of each of the right and left side plates  58 . 
     The pair of bucket cylinders  30  correspond to the pair of left and right booms  27  and are disposed directly thereabove. Each of the bucket cylinders  30  is disposed above and along the line of each of the front boom portions  27 A. The pair of boom cylinders  29  corresponds to the pair of left and right booms  27  and is positioned directly therebelow, each of the boom cylinders  29  being disposed below each of the rear boom portions  27 B. The front end portions of the boom cylinders  29  are supported by and connected to the cylinder pivoting supports  70  for the boom cylinders, and the rear end portions of the bucket cylinders  30  are supported by and connected to the cylinder pivoting supports  71  for the bucket cylinder. 
     The central connection plate  57  is formed by bending a flat plate. The central connection plate  57  is then provided spanning the front and rear cover plates  62   a  and  62   b , and is then attached between the pair of side plates  58  by welding. In addition, the central connection plate  57  is connected to the rear portion side of the cover plate  62   a  of the front boom portion  27 A and to the front portion side of the cover plate  62   b  of the rear boom portion  27 B by welding. The central connection plate  57  includes the front attachment portion  75 , the front inclined portion  77 , the rear inclined portion  78 , the extended projection portion  80 , and the rear attachment portion  81 . The front attachment portion  75  overlaps with and is attached to the rear portion of the cover plate  62   a  of the front boom portion  27 A. The front inclined portion  77  curves upward from the front attachment portion  75  and inclines in a projection so as to approach the pivoting support  71  at a distance from the rear portion side of the cover plate  62   a  of the front boom portion  27 A. The rear inclined portion  78  inclines downward from the projecting end portion of the front inclined portion  77 . The extended projection portion  80  projects by extending to the rear from the lower end portion of the rear inclined portion  78 . The rear attachment portion  81  projects to the rear from the extended projection portion  80  and overlaps with and is attached to the front portion of the cover plate  62   b  of the rear boom portion  27 B. The central connection plate  57  is disposed to be internally between the left and right side plates  58  along the entire length thereof. Aside from the front attachment portion  75  and the rear attachment portion  81 , the front inclined portion  77 , the rear inclined portion  78 , and the extended projection portion  80  connect the left and right side plates  58  at a position distant vertically from the rear portion side of the cover plate  62   a  and the front portion side of the cover plate  62   b.    
     The connection plate projection  84  is formed on the central connection plate  57 , the connection plate projection  84  projecting from the front portion attached to the rear portion of the cover plate  62   a  of the front boom portion  27 A toward a midway portion so as to approach the pivoting support  71 . The connection plate projection  84  is configured from the front inclined portion  77  and the rear inclined portion  78  and is formed to project in a peaked shape so as to vertically overlap behind the pivoting support  71  in a state where the booms  27  are lowered and the working tool  28  is in contact with the ground. 
     Then, both left and right ends of each of the front attachment portion  75 , the front inclined portion  77 , the rear inclined portion  78 , the extending projection portion  80 , and the rear attachment portion  81  of the central connection plate  57  are welded to an upper portion-side inner surface of the right and left side plates  58 . The front attachment portion  75  is welded to the rear portion of the cover plate  62   a  of the front boom portion  27 A. The rear attachment portion  81  is welded to the front portion of the cover plate  62   b  of the rear boom portion  27 B. Furthermore, a hook hole  86  is provided behind the pivoting support  71  on the left and right side plates  58 . 
     According to the above embodiment, the connection plate projection  84  is formed on the central connection plate  57 , the connection plate projection  84  projecting from the front portion attached to the rear portion of the cover plate  62   a  of the front boom portion  27 A toward a midway portion so as to approach the pivoting support  71 . Therefore, the strength in the area around the pivoting support  71  for the working tool cylinder can be effectively increased by the connection plate projection  84 . Thus, in addition to ensuring adequate strength in the area around the pivoting support  71 , it becomes possible to form the left and right side plates  58  with a thin plate thickness (for example, it becomes possible to modify a side plate having a plate thickness of 6.4 mm to 4.6 mm). In this regard, it becomes possible to achieve a reduction in costs (cost reduction of approximately 30%, for example) and the booms  27  can be made cheaper and lighter. Moreover, the central connection plate  57 , inclusive of the connection plate projection  84 , is between the left and right side plates  58  and so is difficult to see from the exterior. Thus, there is no longer any negative effect on exterior appearance due to the form of the connection plate projection  84  and the exterior appearance of the booms  27  improves. 
     In addition, the connection plate projection  84  is formed to project in a peaked shape so as to vertically overlap behind the pivoting support  71  in a state where the booms  27  are lowered and the working tool  28  is in contact with the ground. Therefore, during excavation work and the like in which the booms  27  are lowered and the working tool  28  is in contact with the ground, and for which there is a risk of putting the greatest stress on an area around the pivoting support  71  for the working tool cylinder, the connection plate projection  84  is overlapped from behind on the boss portions of the pivoting support  71  for the working tool cylinder, and thus the area around the pivoting support  71  for the working tool cylinder may be extremely effectively reinforced with the connection plate projection  84  and the strength in the area around the pivoting support  71  for the working tool cylinder can be yet further improved. 
     Moreover, the central connection plate  57  has the front attachment portion  75 , the front inclined portion  77 , the rear inclined portion  78 , the extended projection portion  80 , and the rear attachment portion  81 , and thus rigidity of the connection portions on the rear portion side of the front boom portion  27 A and the front portion side of the rear boom portion  27 B may be increased. In addition, there is no longer any need for the rear portion side of the front boom portion  27 A and the front portion side of the rear boom portion  27 B to be formed to be bulky, nor for the central connection plate  57 , the side plates  58 , and the like to be formed to be bulky. In this regard as well, it becomes possible to make the booms  27  cheaper and lighter. 
     Furthermore, when the central connection plate  57  is attached to the rear portion side of the cover plate  62   a  of the front boom portion  27 A and to the front portion side of the cover plate  62   b  of the rear boom portion  27 B, the position of the central connection plate  57  may be easily displaced forward and backward relative to the rear portion side of the cover plate  62   a  and the front portion side of the cover plate  62   b , and can be easily attached to the rear portion side of the cover plate  62   a  and the front portion side of the cover plate  62   b . In addition, the connection plate projection  84  may be attached as closely as possible behind the pivoting support  71  for the working tool cylinder, leaving the smallest gap necessary. Thereby, a reinforcement effect of the connection plate projection  84  on the area around the pivoting support  71  can be increased. 
     According to the above embodiment, the connection plate projection  84  is formed to project in a peaked shape so as to vertically overlap behind the pivoting support  71  in a state where the booms  27  are lowered and the working tool  28  is in contact with the ground. However, instead, the connection plate projection  84  may be formed to project so as to approach the pivoting support  71  from below in a state where the booms  27  are lowered and the working tool  28  is in contact with the ground. 
     The connection plate projection  84  is not limited to projecting in a peaked shape and may also project in a trapezoidal shape or a quadrangular shape. 
     It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular structures, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. 
     The present invention is not limited to the above described embodiments, and various variations and modifications may be possible without departing from the scope of the present invention.