Abstract:
This invention has an object to provide a method for precisely fabricating transportation pallets readily adaptable to model change and other alterations. In the method for fabricating a transportation pallet according to the invention, in which jig mounting plates are fixed on a steel pallet base, projecting pieces having holes to which jigs are attached are provided on one longer side of the jig mounting plates at a predetermined interval, a positioning member is secured on the pallet base, the jig mounting plates are temporarily secured along the positioning member, and the jig mounting plates are welded to be fixed on the pallet base.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Divisional application of Application No. 11/664,700, filed Apr. 5, 2007, which is a national stage application filed under 35 USC §371 of International Application No. PCT/JP2006/312733, filed Jun. 26, 2006 which claims priority of Japan Application No. 2006-169410, filed Jun. 19, 2006, the contents of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to a method for fabricating transportation pallets, and for example, to a method for precisely fabricating a transportation pallet readily adaptable to model change or other alterations of various machine parts by changing the position of jigs so as to fit the machine parts. 
         [0004]    2. Description of the Prior Art 
         [0005]    Conventionally, transportation of various goods has been carried out with transportation pallets with components to be transported mounted thereon. Transportation pallets for general purpose use have difficulty in securely supporting and retaining the goods mounted thereon. 
         [0006]    The transportation pallets are also used to transport parts of construction machines or the like mounted on the pallets. In the case where such parts are mounted on the general-purpose transportation pallet, the pallet cannot securely support the parts and also occasionally may damage the parts. To overcome the drawbacks, transportation pallets with jigs, which are suitable for each part, directly attached thereon are used. 
         [0007]    However, the preparation of the transportation pallets fitting each part has a drawback in requiring much time and cost, because the transportation pallets need to be modified every time the parts are remodeled with changes of specification or for other reasons. 
         [0008]    A transportation pallet capable of securely retaining various goods and readily adapting itself to the change in shape of the goods has been proposed (see Japanese unexamined patent publication No. 9-156642). This transportation pallet includes a substrate in which a large number of small holes for mounting jigs are made and projecting edges formed along the periphery of the substrate so as to stick out upward and downward, respectively,. Several types of jigs for supporting transportation articles are arranged in predetermined positions on the upper surface of the substrate and detachably secured by bolts, which pass through the small holes, and nuts. The height of the jigs and the height of the securing bolts and nuts are set so as to be not higher than the height of the projecting edges. 
         [0009]    For the transportation pallet disclosed in the above-mentioned Japanese unexamined patent publication No. 9-156642, the large number of small holes for mounting the jigs need to be formed in the substrate, which is a complicated work. In addition, in order to mount a heavy load on such a transportation pallet, the pallet should include a substrate of high strength in consideration of the necessary provision of the large number of small holes, which causes heavy weight and high cost of the pallet. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    In view of the circumstance, an object of the present invention is to provide a method for precisely fabricating a transportation pallet readily adaptable to model change and other alterations. 
         [0011]    In a method for fabricating a transportation pallet with a steel pallet base and jig mounting plates fixed on the pallet base, the present invention is characterized by providing projecting pieces having holes for attaching jigs on one longer side of a jig mounting plate at a predetermined interval, securing a positioning member on the pallet base, temporarily securing the jig mounting plate along the positioning member, and welding the jig mounting plate to be fixed on the pallet base. 
         [0012]    Preferably, after the shorter sides of the jig mounting plate are welded, a longer side that is not provided with the projecting pieces is welded, and subsequently, welding is performed between the projecting pieces. 
         [0013]    In addition, the positioning member can include pin members to be inserted into the holes provided in the projecting pieces and a main positioning body to which the pin members are inserted. 
         [0014]    Further, the positioning member can be a template provided with engaging cut portions for engaging the projecting pieces of the jig mounting plates. In addition, the engaging portions are provided on the projecting pieces of the jig mounting plates to engage with the engaging cut portions. 
         [0015]    According to the above-mentioned structure, the jig mounting plates can be precisely positioned to be securely fixed on the steel pallet base. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    Detailed descriptions of embodiments of the present invention will be now made by referring to drawings. It should be noted that the same components or equivalent components are denoted with the same reference numbers and their descriptions are not reiterated to avoid repetition.  FIG. 1  is a perspective view of a transportation pallet fabricated according to the fabrication method of the present invention. As shown in  FIG. 1 , this transportation pallet comprises a pair of longer-side pallet bases  10 ,  10  and a pair of shorter-side pallet bases  11 ,  11  fixed to the longer-side pallet bases  10 ,  10 . The longer-side pallet bases  10 ,  10  are provided with cut-away portions  10   a  with which the shorter-side pallet bases  11  are engaged, and welded to fix with the shorter-side pallet bases  11 ,  11 . The longer-side pallet bases  10  and shorter-side pallet bases  11  are, for example, lightweight channel steels with dimensions of 250 mm by 75 mm. The longer-side pallet bases  10  and shorter-side pallet bases  11  are laser-machined so as to have a length of 2800 mm and a length of 1100 mm, respectively. This lightweight channel steel may be a hot rolled steel plate for general structure (SS400), a cold rolled steel plate (SPC), a hot rolled steel plate (SPH) and so on. In this embodiment, the hot rolled steel plate for general structure (SS400) is used. 
         [0017]    The pallet bases  10 ,  10  have recesses  10   b,    10   b  and the pallet bases  11 ,  11  have recesses  11   b,    11   b,  both for having blades of a forklift inserted therein. 
         [0018]    Each of the longer-side pallet bases  10 ,  10  and the shorter-side pallet bases  11 ,  11  is fixedly welded with jig mounting plates  12  or  13  by a method which will be described later. A jig mounting plate  12  includes a support base  12   b  having four projecting pieces  12   a  on a longer side thereof. Each projection piece  12   a  has a hole  14  for attaching a jig. A jig mounting plate  13  includes a support base  13   b  having three projecting pieces  13   a  on a longer side thereof. Each projecting piece  13   a  has a hole  14  for attaching a jig. The jig mounting plates  12  and  13  have a different number of projecting pieces and therefore are different in length based on the number of the projecting pieces; however the dimension of the projecting piece, the interval between the projecting pieces and the width of the support base of the jig mounting plates  12  and  13  are the same. 
         [0019]    These jig mounting plates  12 ,  13  are made from a hot rolled steel plate for general structure (SS400), cold rolled steel plate (SPC), hot rolled steel plate (SPH) or the like. In this embodiment, a hot rolled steel plate for general structure (SS400) is used to form the jig mounting plates  12 ,  13  into the predetermined shape by highly precise laser beam machining 
         [0020]    On the bottom of the pallet bases  10 ,  10 ,  11 ,  11 , a bottom plate  15  is fixed to complete a transportation pallet. 
         [0021]      FIG. 2  is a perspective view illustrating an example when a jig suitable for a component is attached to the jig mounting plates  12 ,  13  of the transportation pallet. 
         [0022]    As show in  FIG. 2 , the holes  14  of the projecting pieces  12   a  (or  13   a ) of the jig mounting plates  12 ,  12  (or  13 ,  13 ) are aligned with holes  23  of attachment pieces  22  that are raised from a base  21  of a jig  20 , and secured by bolts  30  and nuts  31 . The base  21  is provided with a supporting shaft  25  for fitting and supporting a component. When the pallet carries remodeled components or different components, the things to do are to prepare the jigs  20  each having a supporting shaft  25  of the proper size for the respective components and to secure the jigs  20  to the predetermined holes  14  of the projecting pieces  12   a  (or  13   a ) of the jig mounting plates  12 ,  12  (or  13 ,  13 ). 
         [0023]    However, attachment of the jig mounting plates  12 ,  12 ,  13 ,  13  in improper fixing positions on the pallet bases  10 ,  11  affects the assembly precision of the jig  20  with the holes  14  of the projecting piece  12   a  or  13   a.  This degraded assembly precision not only causes unstable retention of the components but also occasionally scratches the components. Therefore, the fixing position of the jig mounting plates  12 ,  12 ,  13 ,  13  should be properly determined to precisely attach the jig mounting plates  12 ,  12 ,  13 ,  13  on the pallet bases  10 ,  11 . 
         [0024]    This invention provides a method for properly determining the fixing positions of the jig mounting plates  12 ,  12 ,  13 ,  13  to attach them on the pallet bases  10 ,  11 . The fixing positions of the jig mounting plates  12 ,  12  ( 13 ,  13 ) are set by properly determining four dimensions as will be described later. As mentioned above, the jig mounting plates  12 ,  12  ( 13 ,  13 ) are precisely dimensioned by laser machining Therefore, the fixing positions of the jig mounting plates  12 ,  12  ( 13 ,  13 ) can be properly determined by properly aligning the dimensions of H 1 , P 1 , P 2 , W shown in  FIG. 1  in order to attach the jig mounting plates  12 ,  12  ( 13 ,  13 ) to the fixing positions on the pallet bases  10 ,  11 . 
         [0025]    The four dimensions, as shown in  FIG. 1 , include a height (H 1 ) of the pallet base  10  ( 11 ) to the hole  14  of the jig mounting plates  12 ,  12  ( 13 ,  13 ), pitches (P 1 ) and (P 2 ) each between the jig mounting plates  12  and  13 , and a width (W) between the jig mounting plates  12  and  12  (or  13  and  13 ). 
         [0026]    Highly-precise attachment of the jig mounting plates based on the above-mentioned dimensions is carried out with a setting jig to fabricate a pallet. The constraint conditions defined by the jig include the height (H 1 ) of the jig mounting plates  12 ,  12  ( 13 ,  13 ). The pitches (P 1 ), (P 2 ) between the jig mounting plates  12  and  13  are constrained to the same pitches (P 1 ), (P 2 ) between holes, or to a prescribed dimension. The space between jig mounting plates  12 ,  12  (or  13 ,  13 ) is constrained to a constant dimension irrespective of the variation of the width of the lightweight channel steel of the pallet base. 
         [0027]    With  FIGS. 3 through 7 , the fabricating method using the setting jig will be now described.  FIG. 3  is a perspective view illustrating an example of how the setting jig  40  is used to attach the jig mounting plates  12 ,  12  ( 13 ,  13 ) to the longer-side pallet base  10 . This setting jig  40  sets the pitches (P 1 ), (P 2 ) between the jig mounting plates  12  and  13  and the width (W) between the jig mounting plates  12  and  12  (or  13  and  13 ). The width W 2  of the setting jig  40  is set to the width (W) between the jig mounting plates  12  and  12  (or  13  and  13 ). This setting jig  40  is positioned by an attachment member  45  and secured on the longer-side pallet base  10 . As shown in  FIG. 4 , a position to be attached with a vertical jig  41  for setting the vertical position of the jig mounting plates  12 ,  12  (or  13 ,  13 ) is prescribed on the setting jig  40 , and therefore the vertical jig  41  is attached to the prescribed position. The setting jig  40  is provided with an axial constraint pin  43  to be inserted into the holes  14  of the projecting pieces  12   a  ( 13   a ) to position the holes  14  in order to set the pitches (P 1 ), (P 2 ) between the jig mounting plates  12  and  13 . 
         [0028]    Height-setting jigs  42  for the jig mounting plates  12 ,  12  (or  13 ,  13 ) are placed under the jig  41  and near one end of the setting jig  40 . 
         [0029]      FIG. 5  is a perspective view illustrating an example of how a setting jig  50  is used to attach the jig mounting plates  13 ,  13  on the shorter-side pallet base  11 . This setting jig  50  sets the position of the jig mounting plates  12  and  13 , the width (W) between the jig mounting plates  13  and  13 . The width of the setting jig  50  is set to the width between the jig mounting plates  13  and  13 . This setting jig  50  is positioned by an attachment member  55  and secured on the shorter-side pallet base  11 . A position to be attached with a vertical jig  51  for setting the vertical position of the jig mounting plates  13 ,  13  is prescribed on the setting jig  50 , and therefore the vertical jig  51  is attached to the prescribed position. The setting jig  50  is provided with an axial constraint pin  53  to be inserted into the holes  14  of the projecting pieces  13   a  to position the holes  14  in order to set the position of the jig mounting plate  13 . 
         [0030]    Height-setting jigs  52  for the jig mounting plates  13 ,  13  are placed under the jig  51  and near one end of the setting jig  50 . 
         [0031]      FIG. 6  is a perspective view illustrating the state where the jig mounting plates  12 ,  12  (or  13 ,  13 ) is positioned after attachment of the setting jig  40  (or  50 ) on the pallet base  10  (or  11 ). 
         [0032]    As shown in  FIG. 6 , the jig mounting plate  12 ,  12  (or  13 ,  13 ) is mounted on the jig  42  (or  52 ) so that the edge of the jig mounting plate  12 ,  12  (or  13 ,  13 ) abuts against the vertical jig  51  to set the vertical direction and height Hl. Then, the axial constraint pin  53  is inserted into the hole  14  of the projecting piece  12   a  (or  13   a ) to determine the position of the jig mounting plate  12 ,  12  (or  13 ,  13 ), thereby completing the positioning of the jig mounting plate  12 ,  12  (or  13 ,  13 ) on the pallet base  10  (or  11 ). The jig mounting plate  12 ,  12  (or  13 ,  13 ) in this position is fixedly welded to the pallet base  10  (or  11 ). 
         [0033]    In the fabricating method according to the present invention, welding order is also considered. As a result, it is found that the order of welding causes deformation, including distortion or the like, of the jig mounting plates  12 ,  12  (or  13 ,  13 ). To avoid the deformation, as shown in  FIG. 7 , the jig mounting plate  12  ( 13 ) is welded from its shorter side in the present invention. In this embodiment, part A is welded first, and subsequently part B is welded. After that, the longer side (part C in  FIG. 7 ) that is not provided with the projecting pieces  12   a  ( 13   a ) is welded. At last, the spaces between the projecting pieces  12   a  ( 13   a ) (part Ds in  FIG. 7 ) are welded. By welding in this order, the jig mounting plates  12 ,  12  (or  13 ,  13 ) can be fixed without deformation. 
         [0034]    In this embodiment, arc welding is adopted. Arc welding is performed under the following conditions. The welding current system is operated at a rated output current of 350 A (200 A for single phase), a rated input voltage of 200 V for three-phase and 220 V for single phase. The rated input is 18 kVA/15.2 kW; the output welding current range is from 100 A to 250 A; and the output crater current range is in 125 A. The rated load voltage is 36 V. The output welding voltage range is from 14 V to 38 V and the output crater voltage is from 14 V to 38 V. The rated duty cycle is 60%. The diameter of applicable wires is 0.9 mm, but 1.0 mm or 1.2 mm is also available. 
         [0035]    The wire feeder uses wires having a diameter of 0.9 mm, however, 1.0 mm or 1.2 mm is also available. The cable length is 0.35 m. 
         [0036]    The welding torch is operated at a rated current of 350 A, a rated duty cycle of 40% (carbon dioxide)) and 20% (MAG). The diameter of applicable wires is 0.9 mm, but 1.0 mm or 1.2 mm is also available. The cable length is 3 m. The welding torch is an air-cooled type and curved in shape. The maximum gas flow rate is 10 liters to 20 liters/min. 
         [0037]    Next description will be about another embodiment of the present invention.  FIG. 8  is a perspective view illustrating another embodiment of the invention, while  FIG. 9  is a perspective view illustrating the relevant part of the embodiment of the invention. In this embodiment, a laser processed template is used as a setting jig  60 . In the setting jig  60 , cuts  61  for engaging the projecting pieces  12   a  (or  13   a ) of the jig mounting plates  12 ,  12  (or  13 ,  13 ) are formed by laser processing. This setting jig  60  serving as a template is precisely formed by laser processing. In addition, the projecting piece  12   a  (or  13   a ) is provided with engaging portions  12   f  ( 13   f ) for engaging the cuts  61 . The engaging portions  12   f  ( 13   f ) are also precisely formed by laser processing. 
         [0038]    The above-mentioned setting jig  60  is located at a prescribed position on the pallet base  10  (or  11 ) and then secured by bolts  62 . Subsequently, the engaging portions  12   f  ( 13   f ) are engaged with the cuts  61  to locate the jig mounting plates  12 ,  12  (or  13 ,  13 ) at the prescribed position on the pallet base  10  (or  11 ). After thus being located, the jig mounting plates  12 ,  12  (or  13 ,  13 ) are welded in the same order as mentioned above to be fixed on the pallet base  10  (or  11 ). 
         [0039]    It should be understood that the embodiments disclosed herein are to be taken as examples and are not limited. The scope of the present invention is defined not by the above described embodiments but by the following claims. All changes that fall within meets and bounds of the claims, or equivalence of such meets and bounds are intended to be embraced by the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
       [0040]      FIG. 1  is a perspective view of a transportation pallet fabricated according to the fabrication method of the present invention. 
         [0041]      FIG. 2  is a perspective view illustrating an example when a jig suitable for a component is attached to the jig mounting plates of the transportation pallet. 
         [0042]      FIG. 3  is a perspective view illustrating an example of how a setting jig is used to attach the jig mounting plates to the longer-side pallet base. 
         [0043]      FIG. 4  is a perspective view of a vertical setting jig in an attached state. 
         [0044]      FIG. 5  is a perspective view illustrating an example of how the setting jig is used to attach the jig mounting plates to the shorter-side pallet base. 
         [0045]      FIG. 6  is a perspective view illustrating the state where the jig mounting plate is positioned after attachment of the setting jig on the pallet base. 
         [0046]      FIG. 7  is a front view showing the order of welding the jig mounting plate. 
         [0047]      FIG. 8  is a perspective view of another embodiment of the invention. 
         [0048]      FIG. 9  is a perspective view illustrating a relevant part of another embodiment of the invention.