Portable cradle

Abstract

Described is a portable cradle which includes a removable planar surface, a base and a plurality of vertical support members removably coupled to the base and supporting the planar surface above the base. Each vertical support member includes a biasing member urging the planar member upward away from the base with a total biasing force applied to the planar member being selected based on property of materials to be supported on the planar surface so that a position of an upper surface of the supported materials remains substantially constant as a quantity of materials supported on the planar surface is changed.

What is claimed is:  
     
         1 . A portable cradle, comprising: 
 a removable planar surface;    a base; and    a plurality of vertical support members removably coupled to the base and supporting the planar surface above the base, each support member including a biasing member urging the planar member upward away from the base with a total biasing force applied to the planar member being selected based on property of materials to be supported on the planar surface so that a position of an upper surface of the supported materials remains substantially constant as a quantity of materials supported on the planar surface is changed.    
     
     
         2 . The portable cradle according to  claim 1 , wherein each of the support members is substantially perpendicular to the base.  
     
     
         3 . The portable cradle according to  claim 1 , wherein the base includes a storage portion which accommodates the removable planar surface and the support members in a disassembled configuration.  
     
     
         4 . The portable cradle according to  claim 1 , wherein the biasing member includes a spring and a guide.  
     
     
         5 . The portable cradle according to  claim 4 , wherein the spring is a coil spring.  
     
     
         6 . The portable cradle according to  claim 1 , wherein each of the support members is disposed at a corresponding corner of the base.  
     
     
         7 . The portable cradle according to  claim 4 , wherein the guide defines an internal channel for the spring designed to limit movement of the spring in directions perpendicular to a longitudinal axis of the channel.  
     
     
         8 . The portable cradle according to  claim 4 , wherein the guide includes a structural portion adapted to prevent buckling of the guide.  
     
     
         9 . The portable cradle according to  claim 4 , wherein the removable planar surface is detachably attached to the spring.  
     
     
         10 . The portable cradle according to  claim 9 , wherein the removable planar surface has extensions slidably fitting in the guide, allowing movement of the planar surface along the guide.  
     
     
         11 . The portable cradle according to  claim 4 , wherein the base is detachable attached to the springs.  
     
     
         12 . The portable cradle according to  claim 1 , wherein the biasing member includes: 
 a spring guide detachably attached to the base, the spring guide extending in a direction of movement of the planar surface; and    a spring disposed in the spring guides, the springs providing a restoring force in the direction of movement, wherein the springs are attached at one end to the planar surface.    
     
     
         13 . The portable cradle according to  claim 12 , wherein each of the plurality of spring guides is substantially perpendicular to the base.  
     
     
         14 . The portable cradle according to  claim 1 , wherein the base and the planar surface are adapted to form sides of a box when the support members are in the disassembled configuration, and wherein the support members fit in the box.  
     
     
         15 . The portable cradle according to  claim 1 , wherein the biasing member resists displacement of the planar surface with a force proportional to the displacement.  
     
     
         16 . The portable cradle according to  claim 1 , wherein the support members are storable in a chamber formed by the base and the planar surface.  
     
     
         17 . The portable cradle according to  claim 1 , further comprising: 
 a plurality of moving arrangements coupled to the base.    
     
     
         18 . The portable cradle according to  claim 17 , wherein each of the moving arrangements is a wheel having a braking mechanism and wherein, when the braking mechanism is engaged, it prevent the cradle from moving.  
     
     
         19 . The portable cradle according to  claim 1 , wherein the materials are loaded onto the cradle by being placed on a top of the planar surface.