Abstract:
A hoist assembly and system capable of being adjusted prior to the lifting and transporting of the loads to accommodate infinite center of gravity changes on loads, such that no changes in position occur during the lifting and transporting process.

Description:
BACKGROUND  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates generally to a mechanism and associated system for stabilizing and controlling a hoisted load.  
         [0003]     2. Related Art  
         [0004]     Generally, load transporting mechanisms have a single point lifting capability, such as a single lifting cable. The lifting cable is generally stable only in the vertical direction. Under any external influence from the sides, the load may rotate or sway.  
         [0005]     Various conventional mechanisms have been developed that are intended to compensate for these motions, and stabilize the hoisted load. Single point hoist mechanisms, for example, typically include a heavy duty hoist mechanism, which may include a winch and block and tackle. However, load movement is a basic problem typical of such mechanisms.  
         [0006]     One example of a typical stabilized cargo-handling system uses a means for stabilizing suspended cargo in all six degrees of freedom. These systems have been known to employ at least six individually controlled cables in tension in a kinematic arrangement. Sensors, placed in the complex arrangement with the cables, with high-performance cable drives, are typically used to provide the means to control the multi-cabled system.  
         [0007]     While the aforementioned conventional system may provide varying degrees of control of a hoisted load, its complexity causes it to not be easily adapted to existing single point lift mechanisms.  
         [0008]     What is needed is a hoist assembly, which is capable of being adjusted to accommodate the lifting and transporting of loads of various sizes and weights.  
       SUMMARY  
       [0009]     The present invention provides a hoist assembly and system for lifting and transporting loads. The present invention is capable of being adjusted prior to the lifting and transporting of the loads to accommodate infinite center of gravity changes on loads, such that no changes in position occur during the lifting and transporting process.  
         [0010]     The present invention advantageously relates to a mechanism for stabilizing and controlling the movement of the hoisted load. The mechanism includes scissor like details and sheaves which clamp, brake and/or restrict wire rope movement (slippage) at the time of hoisting a load.  
         [0011]     In one aspect of the present invention, a hoist assembly is provided for stabilizing the movement of a hoisted load. The hoist assembly includes an upper pulley; a first lower pulley and a second lower pulley; a pair of upper scissor members; and a pair of lower scissor members. The pair of lower scissor members are in operational arrangement with the pair of upper scissor members to cause the upper pulley to move between an engaged position with the first lower pulley and the second lower pulley and a disengaged position with the first lower pulley and the second lower pulley.  
         [0012]     In another aspect of the present invention, a hoist system is provided for stabilizing the movement of a hoisted load. The hoist system includes a hoist assembly including a means for causing an upper pulley to move between an engaged position with a first lower pulley and a second lower pulley and a disengaged position with the first lower pulley and the second lower pulley. The system also includes a rope, such as a continuous rotation resistant wire rope.  
         [0013]     Beneficially, the hoist assembly of the present invention provides the ability to stabilize and control a load while it is being lifted or lowered. The hoist assembly is a single point lift mechanism that is relatively light weight, flexible, precise, and easy to operate.  
         [0014]     Advantageously, the present invention is equally compatible with various types of lifting means, including but not limited to, boom cranes, overhead bridge gantry-type cranes and tower-type cranes.  
         [0015]     Additional advantages, objects, and features of the invention will be set forth in part in the detailed description which follows. It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The accompanying drawings are included to provide further understanding of the invention, illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention. In the drawings, the same components have the same reference numerals. The illustrated embodiment is intended to illustrate, but not to limit the invention. The drawings include the following Figures:  
         [0017]      FIGS. 1A and 1B  are schematic diagrams of a hoist system using a hoist assembly in accordance with an embodiment of the present invention.  
         [0018]      FIG. 2  is a simplified perspective view of a hoist assembly in accordance with an embodiment of the present invention.  
         [0019]      FIGS. 3A-3F  are simplified illustrations of components of the hoist assembly embodiment of  FIG. 1 .  
         [0020]      FIG. 4  is a load diagram in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0021]     The motion of a hoisted load may best be described in terms of a Cartesian coordinate system. In describing embodiments of the present invention, the z-axis is in the vertical direction, and the x- and y-axes form the horizontal plane. Terms, such as “lift” and “hoist” as used herein should be understood to refer to lifting, transporting and/or lowering a load, or holding a load stationary in a suspended position.  
         [0022]      FIGS. 1A and 1B  are simplified schematic illustrations of a hoist system  100  shown in accordance with an embodiment of the present invention. In this embodiment, hoist system  100  includes hoist assembly  102  and cable or rope  104 , which may be a continuous “rotation resistant” wire rope  104  and the like. In an alternative embodiment, hoist system  100  may also include back spreader beam hoist tool  106  (hereinafter “back spreader  106 ”), which can be used to distribute pick-up points  110  on the load to positions that provide more stability for loads  108   a  or  108   b.    
         [0023]     As explained in more detail below, in one embodiment, hoist system  100  may be used to lift, hoist and transport loads, such as  108   a  and  108   b , which are different in that they have centers-of-gravity (CG) which vary relative to one another. To ensure that load  108   a  and load  108   b  are lifted with equal stability, hoist assembly  102  may be “repositioned” as load  108   a  is replaced in the system with load  108   b.    
         [0024]     The repositioning of hoist assembly  102  from one position to another to accommodate the hoisting of different load configurations, such as loads  108   a  and  108   b , is accomplished by allowing hoist assembly  102  to slide along wire rope  104  until hoist assembly  102  is positioned above the CG of the load to be lifted, thus making hoist system  100  stable. As described in detail below, as the load is then hoisted, hoist assembly  102  is made to lock wire rope  104  in a fixed position.  
         [0025]      FIG. 2  is a simplified perspective view of hoist assembly  102  in accordance with an embodiment of the present invention. In this embodiment, hoist assembly  102  includes a combination of mechanical linkages and pulleys that are linked into a “scissor” type relationship.  
         [0026]     In this embodiment, hoist assembly  102  includes hoist link  202 , upper scissor members  204 , lower scissor members  206 , biasing members  208 , upper pulley  210 , lower pulleys  212  (i.e. pinch rollers) and spacers  214 . It should be understood that each of these components is commercially available or may be custom made by machining, casting or milling the parts using conventional manufacturing methods. It should also be understood that the dimensions of the components and their material composition can be varied to accommodate specific hoisting applications and load requirements.  
         [0027]     As shown in  FIGS. 3A and 3B  in combination with  FIG. 2 , in one embodiment, each scissor member  204  and  206  includes two plates  302  and  304 , respectively, which are held together in a parallel relationship with a space therebetween to accommodate pulleys, spacers and the like.  
         [0028]     In one embodiment, a first end of each of the two upper scissor members  204  are coupled together at first pivot point  220 , using a conventional fastening means, for example, a bolt or rivet, which allow the members to pivot. Hoist link  202 , which may include, for example a fastening ring or a hook, can also be arranged secure with hoist assembly  102  at pivot point  220 .  
         [0029]     A second end of each upper scissor member  204  is coupled to a first end of each lower scissor member  206  at pivot point  222 . To ensure adequate space for pulleys and the like to be positioned between plates  304  of lower scissor members  206 , a spacer  214  may be sandwiched between the upper and lower scissor members  204  and  206 . Any conventional fastening means can be used to fasten the scissor members together, as long as the fastening means allows the scissor members to pivot.  
         [0030]     Lower scissor members  206  are coupled together at pivot point  224 , using the conventional fastening means. Referring again to  FIG. 2  and to  FIGS. 3C and 3D , upper pulley  210  is co-located at pivot point  224 , and held in a position between plates  304 , such that the fastening means couples upper pulley  210  to hoist assembly  102 , while also allowing upper pulley  210  to rotate thereabout.  
         [0031]     Lower pulleys or pinch rollers  212  are coupled at a second end of each lower scissor member  206 , between plates  304 . Lower pulleys  212  are positioned on the periphery of upper pulley  210 , such that an edge of upper pulley  210  may be made to contact an edge of each lower pulley  212  to be operationally effective.  
         [0032]     Lower pulleys  212  are biased into position using biasing members  208 . In operation, biasing members  208  cause pinch rollers  212  to be biased into position against upper pulley  210  when a load F is placed on hoist assembly  102  (see  FIG. 4 ). The positioning of lower pulleys  212  and upper pulley  210  relative to each other is such that a rope, such as wire rope  104  ( FIG. 1A ), that may be wrapped about upper pulley  210  is in operational contact with lower pulleys  212 . In this manner, lower pulleys  212  can allow the rope to slide around upper pulley  210  during repositioning, but provide a “pinching” effect to hold or lock the rope in place when a load is being hoisted.  
         [0033]     Referring again to  FIG. 1A , in operation a first load  108   a  is lifted using hoist system  100 . With no load applied, the centerline of hoist assembly  102  is positioned above the CG of load  108   a . In this embodiment, a back spreader  106  is used to spread pick-up points  110  out to a position on the periphery of load  108   a  so as to add to the stability of hoist system  100 .  
         [0034]     Referring now to  FIG. 1B , in this embodiment, it can be assumed that a portion of original load  108   a  has been off-loaded to create second load  108   b . To bring hoist system  100  into a desired level of stability, with no load applied, wire rope  104  is made to slide around upper pulley  110  until the centerline of hoist assembly  102  is repositioned above the CG of load  108   b.    
         [0035]     To accomplish this, once load F ( FIG. 4 ) is removed from hoist assembly  102 , biasing members  208  cause scissor members  204  and  206  to pivot relative to each other by forcing the pivot points  222  apart relative to the centerline C of hoist assembly  102 . This movement forces lower pulleys  212  to “disengage” from upper pulley  210  and thus allow wire rope  104  to move freely about upper pulley  210 .  
         [0036]     Once hoist assembly is positioned directly above the CG of second load  108   b , load F may be replaced on hoist assembly  102 , which overcomes biasing members  208  to cause pivot points  222  to move to a position away from centerline C. This movement forces lower pulleys  212  to “re-engage” wire rope  104  to hold the rope in position during hoisting and to maintain the stability of hoist system  100  with second load  108   b.    
         [0037]     It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.