Hoist for loading and unloading objects on a truck bed

Abstract

A hoist for elevating cargo onto the bed of a truck includes a frame which may be mounted to the truck bed, a platform or container which is connected to the frame by a pivoting arm, and an arrangement of linkages for rotating the arm to position the platform either on the truck bed or on a loading and unloading position resting on the ground behind the truck. A threaded screw and an arm tube are connected to the arm via the linkages, with the linkages being arranged to increase the effective “flow” of the arm to provide a long travel distance of the arm. Rotational movement is imparted to the screw by electric, pneumatic and hydraulic systems to extend or retract the cantilever arm as desired.

1 . A pickup truck and a bolt-on removably mounted hoist for loading and unloading objects to said pickup truck bed from the ground level;
 said hoist comprising: a frame, a platform and a moving structure system;   said frame comprising two or more stringers for mounting adjacent to and overlying said pickup truck bed in a generally horizontal orientation when mounted and defining a substantially horizontal plane;   said platform being suitable for carrying an object, said platform being displaceable between a first position supported on said pickup truck bed and a second position rearwardly and downwardly displaced from said pickup truck bed;   said moving structure system comprises a rigid dogleg L-shaped cantilever arm, a threaded screw, and a linkage system;   said rigid dogleg L-shaped cantilever arm for moving said platform between said first and second positions having a first end pivotally mounted to said platform adjacent said upper first end of said platform and having a second ends end pivotally mounted to a rod extending between two said stringers at a point where said cantilever arm will not engage said pickup truck bed as said arm moves through a range of motion;   said cantilever arm having a 90 degree bend spaced from said first end thereof so that when said platform is in said first position, said cantilever arm extends generally vertically from said pivotal connection to said platform to a point below said platform and above said stringers where said cantilever arm extends generally horizontally below said platform;   said cantilever arm has a second bend spaced from said second end to position said second end of said cantilever arm at said pivotal attachment on said stringers;   said threaded screw having first and second ends,   said threaded screw being threadably engaged to an arm tube;   said first end being pivotally mounted to a forward region of said frame, said second end indirectly connected to said cantilever arm for rotating said cantilever arm;   said threaded screw and said arm tube are longitudinally extendable and retractable by imparting rotation to said screw;   said linkage system for indirectly connecting said second end of said threaded screws and said arm tube to said cantilever arm;   said linkage system comprising first and second elongate rigid links;   a first pivot mount joining together said first and second links about a single axis of rotation;   second and third pivot mounts joining said first and second elongate rigid links to said stringers and said cantilever arm respectively, wherein said first and second links, a portion of said cantilever arm and said horizontal plane of said stringers respectively define four sides of a tetragon all four sides of which are pivotal relative to each other;   said threaded screw and said arm tube being positioned generally forward of said rigid links when folded;   said first link being pivotally mounted to said stringers between said threaded screw and said arm tube and said cantilever arm for rotating between a rearwardly leaning position when said threaded screw and said arm tube are fully extended;   an intermediate vertical position and a forwardly leaning position when said threaded screw and said arm tube are fully retracted;   said first link and said second link indirectly join the second end of said threaded screw and said arm tube and said cantilever arm for transmitting force therebetween;   said first link being positioned and configured such that in said rearwardly leaning position the angle between said first and second links is about 90 degrees wherein extension and retraction of said screw and said arm tube actuates said linkage system and said cantilever arm to move said platform between said first and second positions.   
   
   
       2 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 1  wherein opposing sides of said tetragon are non-parallel. 
   
   
       3 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 1  wherein said threaded screw and said arm tube are exterior to said tetragon and extends forwardly therefrom. 
   
   
       4 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 1  having two or more extendible screws and arm tubes, each operatively attached to said cantilever arm and said linkage system. 
   
   
       5 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 1  further comprising an electric motor driving a gear box and a screw coupler to impart rotation to said threaded screw to extend or retract said cantilever arm as desired. 
   
   
       6 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 1  further comprising an electric pneumatic pump driving a pneumatic drive through operatively connected air lines to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired. 
   
   
       7 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 1  further comprising an electric hydraulic pump which moves hydraulic fluid to and from a reservoir and a hydraulic drive to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired. 
   
   
       8 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 1  having two or more extendible screw and arm tubes, each operatively attached to said cantilever arm and said linkage system. 
   
   
       9 . A bolt-on hoist sized to operatively fit in the bed of a standard pickup truck for loading and unloading objects to and from said pickup truck bed and to and from positions at and significantly lower than ground level;
 said hoist unit comprising: a frame, a moving structure system attached to said frame, and a platform movable by said moving structure system;   said frame comprising at least two stringers for mounting adjacent to and overlying said pickup truck bed and presenting a generally flat surface to said pickup truck bed when mounted and defining a substantially horizontal plane;   said frame is removably secured to said pickup truck bed by at least two bolts;   said platform being suitable for carrying one or more objects;   said platform being displaceable between a first position supported on said pickup truck bed and a second position rearwardly and downwardly displaced from said pickup truck bed;   said moving structure comprising a rigid dogleg L-shaped cantilever arm, a threaded screw and arm tube, and a linkage system powered from an electric power supply from said pickup truck;   said rigid dogleg L-shaped cantilever arm moves said platform between said first and second positions and has a first end pivotally mounted to said platform adjacent said upper first end of said platform and has a second end pivotally mounted to a rod extending between two said stringers at a point where said cantilever arm will not engage said pickup truck bed as said cantilever arm moves from said first position to said second position through a range of motion;   said single longitudinally extendible screw and arm tube having first and second ends;   said first end being pivotally mounted to a forward region of said frame;   said second end indirectly connected to said cantilever arm for rotating said cantilever arm;   said cantilever arm having an approximately 90 degree bend spaced from said first end thereof so that when said platform is in said first position, said cantilever arm extends generally vertically from said pivotal connection to said platform to a point below said platform and above said stringers where said cantilever arm extends generally horizontally below said platform;   said cantilever arm has a second bend spaced from said second end of said cantilever arm to said position of said second end of said cantilever arm at said pivotal attachment at said stringers;   a linkage system for indirectly connecting said second end of said screw and arm tube to said cantilever arm;   said screw and arm tube being positioned generally forward of said rigid links when folded;   said first link being pivotally mounted to said stringers between said screw and arm tube and said cantilever arm for rotating between a rearwardly leaning position when said screw and arm tube is fully extended, an intermediate vertical position and a forwardly leaning position when said screw and arm tube is fully retracted, and said second link directly joining the second end of said screw and arm tube and said cantilever arm for transmitting force therebetween, said first link being positioned and configured such that in said rearwardly leaning position the angle between said first and second links is about 90 degrees; and,   said extension and retraction of said screw and arm tube actuates said linkage system and said cantilever arm to move said platform between said first and second positions.   
   
   
       10 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 9  further comprising an electric motor driving a bear box and a screw coupler to impart rotation to said threaded screw to extend or retract said cantilever arm as desired. 
   
   
       11 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 9  further comprising an electric pneumatic pump driving a pneumatic drive through operatively connected air lines to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired. 
   
   
       12 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 9  further comprising an electric hydraulic pump which moves hydraulic fluid to and from a reservoir and a hydraulic drive to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired. 
   
   
       13 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 9  having two or more extendible screws and arm tubes, each operatively attached to said cantilever arm and said linkage system. 
   
   
       14 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 9  having two or more extendible screws and arm tubes, each operatively attached to said cantilever arm and said linkage system. 
   
   
       15 . A pickup truck and a bolt-on removably mounted hoist for loading and unloading objects on the bed of a vehicle, said hoist comprising: a framework for mounting on said bed of said vehicle;
 said framework including a longitudinally extending stringer;   a platform for receiving an object from loading onto said bed of said vehicle;   said platform being moveable between a first position supported on said bed of said vehicle and a second horizontal position rearwardly displaced from said bed to receive an object thereon;   a cantilever arm for moving said platform and having a first end and a second end;   said first end being pivotally jointed to said platform and said second end being pivotally joined to said stringer at a point where said cantilever arm will not engage said bed of said vehicle as said cantilever arm moves through a range of motion;   said cantilever arm having a 90 degree bend spaced from said first end thereof so that when said platform is in said first position, said cantilever arm extends generally vertically from said pivotal connection to said platform to a point below said platform and above said stringers where said cantilever arm extends generally horizontally below said platform;   said cantilever arm has a second bend spaced from said second end to position said second end of said cantilever arm at said pivotal attachment on said stringers;   a longitudinally extendable actuator comprising a threaded screw and a threadably engaged arm tube;   said actuator having a first end and a second end;   said first end being pivotally mounted to said framework at a forward region thereof;   a linkage arrangement joining said second end of said actuator to said cantilever arm for rotating said cantilever arm for selectively raising and lowering of said platform;   said linkage arrangement comprising a first generally upstanding pivotal link connecting said second end of said actuator with said framework;   a second pivotal link connecting said second end of said actuator with said cantilever arm; and,   said pivotal links both being pivotally mounted at both ends thereof.   
   
   
       16 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 15  further comprising an electric motor driving a gear box and a screw coupler to impart rotation to said threaded screw to extend or retract said cantilever arm as desired. 
   
   
       17 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 15  further comprising an electric pneumatic pump driving a pneumatic drive through operatively connected air lines to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired. 
   
   
       18 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 15  further comprising an electric hydraulic pump which moves hydraulic fluid to and from a reservoir and a hydraulic drive to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired. 
   
   
       19 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 15  wherein said linkage arrangement forms a tetragon; and,
 said tetragon having non-parallel opposing sides.   
   
   
       20 . The pickup truck and said bolt-on removably mounted hoist as defined in  claim 15  wherein said linkage arrangement forms a tetragon and said threaded screw and said arm tube are exterior to said tetragon and extend forwardly therefrom.