Patent Document

This application claims priority to U.S. Provisional Application Ser. No. 60/614,303 for Load Test Apparatus for Shipping Containers filed Sep. 28, 2004 by the above referenced Applicants, the entire contents of which are hereby incorporated by reference. 

   FEDERALLY SPONSORED RESEARCH 
   Not Applicable 
   SEQUENCE LISTING OR PROGRAM 
   Not Applicable 
   BACKGROUND 
   1. Field of Invention 
   This invention relates to the load testing of structures that are lifted or suspended by one or more cables or chains, collectively referred to as “Shipping containers”. The test apparatus applies a load to the lifting points of the containers, known as pad eyes, and simulates the application of loads present in the container when it is lifted or suspended. 
   2. Background 
   Shipping containers are designed, manufactured and tested in compliance with one or more specifications published by governmental and private organizations. These specifications require that the container be load tested to a multiple of the rated load of the container. The most popular method used to apply the test load is to fill the container with heavy objects such as concrete, steel, water, etc. This method is time consuming, expensive, and of questionable accuracy. 
   A second method is to use a hydraulic ram to apply a load to a cable attached to one or more pad eyes, where the reaction of this load is applied to the container near the pad eye being tested. This method applies the load only to the pad eye and not to the entire structure of the container. Therefore, this method does not simulate the actual loads applied the contents of the container when it is in use. 
   A third method is to use a single telescopic mast to apply a load to cables attached to two or more of the pad eyes. The reaction of this load is applied to the bottom of the structure, more closely simulating the loads applied by the contents of the container when it is in use. This method works well for smaller containers whose length and width are nearly equal, i.e., the container is nearly square. However, it is common for containers to have a large aspect ratio, where the length is several times the width, i.e., the containers are long and narrow. 
   Containers of large aspect ratios present at least two significant problems to the single telescopic mast method of application of the test load. First, the apparatus must be tall enough to allow the cables to form an angle of not less than 45 degrees with the horizontal. Such a test apparatus must be heavy enough not to fail by buckling when the test loads are applied and, because of the height and weight requirements, the apparatus presents a safety hazard to personnel setting up and operating the apparatus. The second problem with the single telescopic mast method is that the load is applied to a relatively small area at the center of the container unless large, heavy beams are used to distribute the load along the base of the container. 
   Considerations 
   A safe and efficient test apparatus for shipping containers should be compact, and easily set-up for testing. It should have a low weight-to-strength ratio, that is, it should be as light-weight as possible while being strong enough to apply and withstand the required loads. Members subject to compressive loads should be as short as possible to increase the resistance of the member to failure or excessive deformation due to buckling. It should reliably apply the test load to the lifting eyes and to the bottom of the container in such a manner so as to accurately simulate the magnitude and direction of an actual load typical to said container. The test load should be evenly distributed among the lifting eyes of the container. The design should provide a means to accurately measure the applied load and minimize the factors that contribute to measurement errors. Such factors include improper set-up resulting in improper alignment of components, improper angle between the cables and a horizontal plane, application of extraneous loads and moments to the load measuring members, and improper distribution of the reaction load to the structure of the container. 
   Objects and Advantages 
   Several objects and advantages of the present invention are: 
   (a) to provide a test apparatus that maximizes safety to personnel while setting up and operating the apparatus, specifically by attaining a low weight-to-strength ratio while maximizing the factor of safety of the apparatus against failure; 
   (b) to provide a test apparatus that reduces the weight-to-strength ratio by eliminating the application of moment loads to members of the test apparatus; 
   (c) to provide a test apparatus that resists failure and excessive deformation due to buckling, specifically by providing a plurality of load application members such as hydraulic cylinders; 
   (d) to provide a test apparatus that applies the test load to the container in a manner so as to accurately simulate the typical loading conditions applied to the container during use, specifically by applying and distributing said test loads so as to induce stresses within various members of the container; and, 
   (e) to provide a test apparatus that accurately measures the applied test load, specifically by reducing extraneous components of the applied and reaction loads and by minimizing deformation of members of the test apparatus. 
   SUMMARY 
   In accordance with the present invention a load test apparatus for shipping containers is comprised of a plurality of hydraulic cylinders or other force generating means to apply an upward force to a structure that applies and evenly distributes said load to lifting eyes of the container to be tested. A pivotal plate assembly is attached to each force generating means and eliminates the application of moment loads to the structure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of Load Test Apparatus of Applicants&#39; invention. 
       FIG. 2  is an isometric view of the Beam Assembly of the Apparatus shown in  FIG. 1 . 
       FIG. 3  is an isometric view of the Pivotal Plate of the Beam Assembly shown in  FIG. 2 . 
       FIG. 4  is an isometric view of the Beam Housing of the Beam Assembly shown in  FIG. 2 . 
       FIG. 5  is a top view of the Apparatus shown in  FIG. 1 . 
       FIG. 6  shows a partial section view cut a Section  6  of  FIG. 5 . 
       FIG. 7A  shows a section view cut at Section  7  of  FIG. 5  showing the Pivotal Plate Assembly and the Adjustment Pin of the Load Test Apparatus Assembly of  FIG. 1 . 
       FIG. 7B  shows the same section view as  FIG. 7A , with the exception that the Adjustment Pin is in its Retracted Position. 
       FIG. 8  shows a Cable Assembly  130  in detail. 
       FIGS. 9A and 9B  show an end view and front view, respectively, of the attachment of the Pivotal Plate Assemblies to the Basket. 
       FIG. 9C  shows an enlarged detail of  FIG. 9B . 
       FIG. 10  shows a typical prior art load test apparatus. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the reference drawings, numerals referencing assemblies are underlined. 
   Referring now to the drawings and more particularly to  FIG. 1 , there is shown an isometric view of Load Test Apparatus Assembly  100  of the present invention. The Load Test Apparatus  100  is comprised of a horizontal Beam Assembly  110 , which is supported by two vertical lifting means, such as Cylinder Assemblies  120 . Cylinder Assembly  120  is comprised of a Stationary Cylinder  250 , a coaxial Piston Rod  260  extending vertically upward from the top of Stationary Cylinder  250 , and a horizontal Base Plate  285  attached to the bottom surface of Stationary Cylinder  250 . Four Cable Assemblies  130  connect the Beam Assembly  110  to four Lifting Eyes  330  of a typical Basket  160 . Cylinder Assemblies  120  are pressurized by a Hydraulic Pump Assembly  150 . Cylinder Assemblies  120  are connected to the Hydraulic Pump Assembly by hoses. The hoses are omitted from the drawings for clarity. The upward force produced by Cylinder Assemblies  120  is displayed by a Load Indicator  140 . 
   The Basket  160  has a vertical centroidal axis  390 , a central vertical longitudinal plane  360 , and a central vertical transverse plane  370 . The Basket  160  is not a component of the present invention. It is included in the drawings to more clearly show the operation of the present invention. 
     FIG. 2  shows the Beam Assembly  110  which is comprised of a Beam  200 , and two Pivotal Plate Assemblies  210 . Beam  200  has a series of horizontal Adjustment Holes  230  bored transverse to a longitudinal Axis  220  of Beam  200  and perpendicular to the sides of Beam  200 . Each Pivotal Plate Assembly  210  is comprised of a Pivotal Plate  410  and a Beam Housing  420 . Pivotal Plate  410  is pivotally attached to Beam Housing  420  and to Beam  200  by an Adjustment Pin  430 . Adjustment Pin  430  has a longitudinal axis  435 . 
   Referring to  FIG. 3 , Pivotal Plate  410  is comprised of a Wing Plate  412  and an Adjustment Pin Housing  725 . Wing Plate  412  has a central rectangular thru-hole  515  and a series of cable attachment thru-holes  510  displaced from the bottom of Plate  412 . The longitudinal axis  730  of Adjustment Pin Housing  725  is horizontal and is coincident with the centroid  460  of rectangular thru-hole  515 . Pivotal Plate  410  has a central plane  480  parallel to the face of Pivotal Plate  410  and coincident with Centroid  460  of rectangular thru-hole  515 . 
   Referring to  FIG. 4 , the Beam Housing  420  is comprised of a horizontal Top Plate  550 , two vertical Side Plates  560 , and a horizontal Bottom Plate  570 . A Load Cell Housing  440  extends vertically downward from the bottom Plate  570 . Top Plate  550 , Side Plates  560 , and Bottom Plate  570  are fixedly attached together so as to form a horizontal, rectangular Beam Housing Opening  490  whose dimensions are slightly larger than the outside cross-section dimensions of Beam  200 , i.e., Beam  200  can fit through the Beam Housing Opening  590 . A transverse thru-hole  580  is bored through both Side Plates  560  such that the axis  585  of thru-hole  580  is horizontal and is coincident with and perpendicular to the horizontal axis  590  of Beam Housing Opening  490 . Bottom Plate  570  has a bottom surface  575 . Load Cell Housing has a vertical longitudinal axis  445 . 
     FIG. 5  shows a top view of the Load Test Apparatus Assembly  100  showing a top view of the Beam Assembly  110 .  FIG. 5  is included solely to describe the location of Section  6  depicted in  FIG. 6  and Section  7  depicted in  FIGS. 7A and 7B . 
     FIG. 6  shows a partial section view through the Beam  200 , Beam Housing  420  and the Piston Rod  260  of the Load Test Apparatus Assembly  100 . Beam  200  fits within the Beam Housing Opening  490  of the Beam Housing  420  such that each Pivotal Plate Assembly  210  fits slidably onto Beam  200 . A compression Load Cell  450 , shown in cross-section, is sandwiched between the top surface  280  of the Piston Rod  260  and the bottom surface  575  of Bottom Plate  570 . Piston Rod  260  fits slidably within Load Cell Housing  440 . 
   Load Cell  450  may be electronic, hydraulic, or other type of compressive load cell. Load Cell  450  is connected to Load Indicator  140 . This connection may be by electrical cable, radio-telepathy, or other means. The Load Cell  450  and the associated Load Indicator are standard components. The specifics of the type of Load Cell  450  and the type of Load Indicator  140  are not pertinent to the present invention. The connection between the Load Cell  450  and the Load Indicator  140  is omitted from the figures for clarity. 
     FIG. 7A  shows a section view cut at Section  7  of  FIG. 5  showing the Pivotal Plate Assembly  210  and the Adjustment Pin  430  of the Load Test Apparatus Assembly  100 .  FIG. 7B  shows the same section view as  FIG. 7A , with the exception that the Adjustment Pin  430  is in its Retracted Position  630 . The Piston Rod  260  and the Load Cell  450  are omitted from  FIGS. 7A and 7B  for clarity. The Adjustment Pin  430  has an Extended Position  640  and a Retracted Position  630  (seen in  FIG. 7B ). 
   In the Extended Position  640 , each Adjustment Pin  430  is centered within its respective Adjustment Pin Housing  725  such that it engages both the Beam Housing  420  of the Pivotal Plate Assembly  210  and the Beam  200 . Specifically, the Adjustment Pin  430  is disposed within Adjustment Pin Housing  725 , thru-holes  580  of the Beam Housing  420 , and a selected thru-hole  230  of the Beam  200 . Thus, when the Adjustment Pin  430  is in the Extended Position  640 , the respective Pivotal Plate Assembly  210  is restrained from sliding axially along Beam  200 , and Pivotal Plate  410  is free to rotate about the Adjustment Pin  430 . 
   In the Retracted Position  630 , the Adjustment Pin  430  is disposed axially within Adjustment Pin Housing  725  such that it continues to engage the Adjustment Pin Housing  725  and one thru-hole  580  of Beam Housing  420 , but it does not engage Beam  200 . Thus, when the Adjustment Pin  430  is in the Retracted Position  630 , the respective Pivotal Plate Assembly  210  is free to slide axially along Beam  200 , while the Pivotal Plate  410  is still pivotally attached to the Beam Housing  420 . 
     FIG. 8  shows a Cable Assembly  130  in detail. Each Cable Assembly  130  is comprised of a steel Cable  290  with a Clevis  300  attached to each end. The Cable Assemblies  130  are of equal length. Cable  290  has a longitudinal axis  295 . Cable Assemblies  130  and Clevises  300  are standard components commonly used for lifting objects. The operation of Clevis  300  is known to anyone skilled in the art of millwright. 
     FIGS. 9A and 9B  show an end view and front view, respectively, of the attachment of the Pivotal Plate Assemblies  210  to the Basket  160 . A Cable Assembly  130  extends from and between a selected Thru-Hole  510  in Wing Plate  412  of the Pivotal Plate  410  to a respective Lifting Eye  330  on the Basket  160  by means of the Clevises  300 . An Angle A 1  between the Cable Assembly  130  and a horizontal plane is projected onto the Transverse Plane  370  of Basket  160 . The projected Angle A 1  is determined by which Thru-Hole  510  of Pivotal Plate  410  is selected. An Angle A 2  between Cable Assembly  130  and a horizontal plane is projected onto the Longitudinal Plane  360  of Basket  160 . Each Cylinder Assembly  120  is displaced a distance D 1  from a respective end of Basket  160 . The projected Angle A 2  is determined by the distance D 1 . Common practice dictates that angles A 1  and A 2  must be greater than or equal to 45 degrees. 
     FIG. 9C  shows an enlarged detail of  FIG. 9B . In this view, Adjustment Pin  430 , its axis  435 , and plane  480  are perpendicular to the plane of the drawing. It can be seen that Axis  435  of Adjustment Pin  430 , Axis  220  of Beam  200  and Axis  445  of Load Cell Cylinder  440  all intersect at a common point  455 . Pivotal Plate  410  rotates freely about Adjustment Pin  430 , thereby allowing the central Plane  480  of Pivotal Plate  410  to become coincident with Axis  295  of Cable Assembly  130 . Plane  480  of Pivotal Plate  410  is coincident with Axis  435  of Adjustment Pin  430 . Axis  295  of Cable Assembly  130  represents the line of action of the force transferred by Cable Assembly  130 . This force is transmitted from Adjustment Pin  430 , through Plate  410 , through Cable Assembly  130  to Lifting Eye  330 . Axis  445  of Load Cell Housing  440  represents the line of action of the upward vertical force provided by the hydraulic Cylinder Assembly  120 . This force is transmitted from the Piston Rod  260  of Hydraulic Cylinder Assembly  120 , through Load Cell  450 , and through Bearing Housing  420  to Adjustment Pin  430 . Axis  220  of Beam  200  represents the line of action of the resultant of these two forces, specifically a tensile load transmitted from Adjustment Pin  430  to Beam  200 . From the preceding description, it is seen that all of the described forces are transmitted through Adjustment Pin  430 . 
   The intersection of the lines of action of the forces referred to above is significant because the forces do not impart moment loads on any of the members. In general, stresses from moment loads are considerably greater than stresses from tensile loads. By eliminating moment loads, the members may be considerably lighter than if moment loads were present. Reduction of the weight and size of a load test apparatus significantly increases the safety of operation. 
     FIG. 10  shows a general embodiment of the prior art. For purposes of the current discussion, the vertical lifting means, such as a hydraulic cylinder, is referred to as a column  900 . A load test apparatus comprising a single force generating means, such as a single cylinder assembly, i.e., a load test apparatus comprising a single column, requires that the column extend upward from the bottom of the basket to the point of convergence  910  of each of the cable assemblies  920 . This point of convergence  910  may be a considerable distance above the basket. For a projected horizontal angle of 45 degrees between Cable Assemblies  920  and the central transverse plane of Basket  160 , the height of a single column must be at least one half of the longest dimension of the basket. Thus it is seen that the single column cylinder assembly must be considerably longer than the columns of the Load Test Apparatus  100  of the present invention. 
   Vertical members loaded in compression, generally known as columns, have a property know as a “slenderness ratio”. In simple terms, the slenderness ratio is a relationship between the column&#39;s least radius of gyration and its length. The slenderness ratio of a column determines if the column is more likely to fail due to buckling rather than due to compressive axial stress. A column with a high slenderness ratio, i.e., a long, slender column, will fail due to a buckling load, known as the critical load for that column. In order to safely withstand a given load, such as the load to be applied to a basket  160  by a Load Test Apparatus, a longer column must have a larger radius of gyration than a shorter column. A longer column must therefore be larger and heavier than a shorter column designed to withstand the same load as that applied to the longer column. 
   Referring again to  FIG. 10 , it is seen that if each of the cables  920  are not exactly the same length, a side load will be induced at the top of the column  900 . Similarly, a side load will be induced if the column  900  is not positioned exactly at the center of the Basket  160 , i.e., not directly beneath the point of convergence of the cables. The presence of even relatively small side loads applied to the top of a long column significantly reduces the capability of the column to safely withstand a vertical load. Several factors, including human error on the part of the operator, make it inevitable that extraneous side loads will be applied to any load test apparatus. The Load Test Apparatus  100  of the present invention is more capable of safely withstanding the effects of side loads than that of the apparatus shown in  FIG. 10 . 
   OPERATION 
   In operation, the Load Test Apparatus Assembly  100  of applicant&#39;s invention is lowered into the Basket  160  and positioned such that Axis  220  of the Beam  200  is coincident with the Longitudinal Plane  360  of the Basket  160 , i.e., the Beam  200  is centered within the Basket  160 . The Adjustment Pin  430  of each Pivotal Plate Assembly  210  is moved axially to the Retracted Position  630 , as shown in  FIG. 7B . Each Pivotal Plate Assembly  210  is moved axially along Beam  200  such that each Pivotal Plate Assembly  210  is equidistant from the Transverse Plane  370  of Basket  160  and a distance D 1  from the end of Basket  160 . A first Clevis  30  of a first Cable Assembly  130  is attached to a first Lifting Eye  330 . The second Clevis  300  of the first Cable Assembly  130  is attached to a selected Hole  510  of a Pivotal Plate  410 . As described above, the selection of Hole  510  determines the size of the projected Angle A 1 . Projected Angle A 1  must be no less than 45 degrees from a horizontal plane. Conversely, it is desirable that the selected Hole  510  be as near to Longitudinal Plate  360  (that is, as near to the Beam  200 ) as possible in order to minimize the stresses within Pivotal Plate  410 . The Hole  510  is therefore selected such that it is as near to the Beam  200  as possible while still allowing projected Angle A 1  to be equal to or greater than 45 degrees. The remaining three Cable Assemblies  130  are attached to the remaining Lifting Eyes  330  and to Holes  510  in the same relative position as the first Hole  510  selected as described above. Thus, the connections of the Cables  130  to the Pivotal Plates  410  will be symmetrical about both the Longitudinal Plane  360  and the Transverse Plate  370   
   After all four Cable Assemblies  130  are attached to the four Lifting Eyes, the Pivotal Plate Assemblies  210  are then attached to the Beam  200 . The procedure for positioning and attaching a first Pivotal Plate Assembly  210  to Beam  200  is described below. The second Pivotal Plate Assembly  210  is the attached in a similar manner such that the position if the two Pivotal Plate Assemblies  210  is symmetrical about the Transverse Plane  370 . 
   The Pivotal Plate Assembly  210  is attached to Beam  200  by inserting the Adjustment Pin  430  through a selected Adjustment Hole  230  in Beam  200 . As described above, the projected Angle A 2  must be no less than 45 degrees from a horizontal plane. Distance D 1 , from the end of the Basket  160  to the Cylinder Assembly  120 , determines the magnitude of Angle A 2 . An Adjustment Hole  230  is selected such that Angle A 2  is equal to or greater than 45 degrees. After selection of the appropriate Adjustment Hole  230 , the Pivotal Plate Assembly  210  is moved axially along Beam  200  until the Alignment Pin  430  is coaxially aligned with the selected Adjustment Hole  230 . The Adjustment Pin  430  is moved axially within the Adjustment Pin Housing  725  until it is in the Extended Position  640  as shown in  FIG. 7A . 
   Hydraulic hoses are connected to the Hydraulic Pump Assembly  150  and the Hydraulic Cylinder Assemblies  120 . The Load Cell  450  is electrically connected to the Load Indicator  140 . This electrical connection may be made either by using wires or by radio-telepathy. 
   The Hydraulic Pump Assembly  150  is activated to energize the Hydraulic Cylinder Assemblies  120  so that the desired testing load is applied by the Hydraulic Cylinder Assemblies  120  to the Beam Assembly  110 , as measured by Load Cell  450  and displayed by Load Indicator  140 . This test load may be held for some amount of time as required by the governing standard or procedure. 
   After the test load has been applied to the basket for the required amount of time, the Hydraulic Cylinder Assemblies  120  are de-energized, the Cable Assemblies  130  are removed from the Lifting Eyes  330  of the Basket  160 , the Hydraulic Hoses are removed from the Hydraulic Cylinder Assemblies  120 , the Load Cell  450  is disconnected from the Load Indicator  140 , and the Load Test Apparatus  100  is removed from the Basket  160 . 
   The foregoing description is merely an illustration of the principles of the Load Test Apparatus of Applicants&#39; invention. Since numerous modifications and changes will readily occur to those skilled in the art, the description is not intended to limit the invention to the exact construction and operation shown and described. Accordingly, all suitable modifications and equivalents are intended to fall within the scope of the invention.

Technology Category: g