Abstract:
An automatic signaling system to prevent a tractor from being accidently lifted with the cargo by a ship to shore gantry crane. The embodiment includes multiple sensors to detect a lifted condition and radio output upon a lifted condition. The radio output channel is determined by an automatic identification system that identifies the crane the tractor is under. Upon receiving a lifted signal the cranes hoist will be stopped and disabled but will still allow lowering until the lifted signal stops.

Description:
FEDERALLY SPONSORED RESEARCH 
     Not Applicable 
     SEQUENCE LISTING OR PROGRAM 
     Not Applicable 
     BACKGROUND 
     1. Field 
     This invention generally relates to container handling gantry cranes including ship to shore, rubber tire gantry, and rail mounted gantry. 
     2. Prior Art 
     Every year the ships and cranes get bigger and faster, but the means for loading stay the same. The driver of a tractor pulling a chassis with a container on it pulls under a crane, two or more workers on the ground uncouple the container from the chassis, and the load is lifted onto the ship. The container is coupled to the chassis by strong elliptical toggles in each corner which are rotated in elliptical sockets in the container. Sometimes the chassis is not fully uncoupled and the container, chassis, tractor, and operator are lifted into the air. This usually results in the tractor breaking free and falling to the ground causing injuries to the operator and damage to the equipment. Because the tractors have no rear springs, a drop from as little as 200 mm can jostle the operator and cause neck and back injuries, for this reason an improved system is needed. 
     Several attempts have been made to resolve this problem. U.S. Pat. No. 5,260,688 issued Nov. 9, 1993 used a user selectable radio transmitter to deactivate the crane if the tractor was rotated around the front wheel and a wand contacted the ground. This system had several drawbacks. The wand could be easily damaged by hitting debris in the container yard. Also by the time the wand contacted the ground the rear of the tractor could be up to 800 mm off of the ground. While it would protect the tractor from being lifted entirely off of the ground, the driver could still be injured. A careless operator could improperly select the radio channel, or forget to altogether. This could leave the tractor unprotected. It could also shut down an adjacent crane while it is in motion causing the crane operator to lose control of the load endangering workers on the ship and dock. 
     U.S. Pat. No. 5,455,567 describes a system using a photo sensor on the rear of the tractor to trigger a 28 Hz strobe light. The strobe is picked up by a pulse discriminator mounted on the cranes trolley that inhibits the crane hoist. The system is active any time the tractor is running. This system worked fairly well when it was developed but is not adequate for the newer, faster cranes unless slowdowns are added. Photo sensors are unreliable on asphalt. Paint stripes and other color changes can change their set points and result in a delayed hoist deactivation. The reaction time between the strobe and the pulse discriminator can be as high as 500 ms. Modern cranes have hoist speeds of 190 m per minute and accelerate to full speed in 2.0 seconds. If you take into account the strobe does not signal until the tractors rear wheels have lifted to about 150 mm and the crane continues to accelerate, the tractors rear wheels can be 800 to 1500 mm off of the ground before the hoist is stopped. For this reason the later versions of this system added a 2 second slowdown to the crane that limited the hoist speed to 20% of the base speed when hoisting a container from the dock. The later systems also abandoned the photo sensor and used a single axis tilt sensor to trigger the strobe. The single axis tilt sensor still did not detect the lift until the tractor had been lifted about 200 mm off of the ground. Even with the added slow down a perfectly operating system did not stop the hoist until the tractors rear wheels were about 300 mm off of the ground. The single axis tilt sensor was also ineffective at detecting roll that can happen if only one corner is coupled. 
     ADVANTAGES 
     The present embodiment solves these problems and has many advantages over prior art. The tractor can pull under any crane and the controller will automatically select the proper radio channel. Another advantage is the improved lift detection. This embodiment can detect lift before the tractor comes off of the ground. This coupled with a microprocessor based controller, and radio output. The signal for hoist deactivation is almost instantaneous. It can stop the hoist before the tractors rear wheels come off of the ground without adding a timed slow down to the crane and affecting production. Another added benefit is a reduction in jostling injuries that are common when the rear of the tractor is dropped from 200 mm or more. 
     SUMMARY 
     A system to prevent a tractor-trailer from being accidently lifted by a gantry crane including multiple tilt, height, and pressure sensors on the tractor to trigger a multichannel radio transmitter that will be received by the appropriate crane and stop the hoist from raising while still allowing lowering. The radio channel is automatically determined by communication between the crane and the tractor. 
    
    
     
       DRAWINGS FIGURES 
         FIG. 1  is an elevational view of a gantry crane that shows a chassis, and container that use the invention. 
         FIG. 2  is a side view of  FIG. 1  showing more detail with the tractor visible; and 
         FIG. 3  is an enlarged view of  FIG. 2  with the crane structure removed; and 
         FIG. 4  is an enlarged view of the tractor in  FIG. 3 ; and 
         FIG. 5  is an enlarged view of the circled area in  FIG. 4   
         FIG. 6  is a block diagram of the circuitry employed in the crane spreader; and 
         FIG. 7  is a block diagram of the circuitry employed in the tractor; and 
         FIG. 8  is a flow chart of the software used in the tractor; and 
     
    
    
     REFERENCE NUMERALS 
     
       
         
               
               
               
               
             
           
               
                   
               
             
             
               
                 10. 
                 Container 
                 12. 
                 Chassis 
               
               
                 14.  
                 Tractor 
                 16. 
                 Trolley 
               
               
                 18.  
                 Head Block 
                 20.  
                 Spreader 
               
               
                 22.  
                 Crane Boom 
                 24.  
                 Ship 
               
               
                 26.  
                 Tractor Controller 
                 28.  
                 Inductive Proximity Sensor 
               
               
                 30.  
                 Hydraulic Cylinder 
                 32. 
                 Landing Leg 
               
               
                 34.  
                 Fifth Wheel Plate 
                 36.  
                 Ultrasonic Sensor 
               
               
                 38.  
                 Dual Axis Tilt Sensor 
                 40. 
                 Multi-Channel Radio Transmitter 
               
               
                 42.  
                 Radio Receiver 
                 44.  
                 Infrared Emitter 
               
               
                 46.  
                 Infrared Decoder 
                 48.  
                 Junction Box 
               
               
                 50.  
                 Messenger Cable 
                 52. 
                 Spreader Controller 
               
               
                 54.  
                 Off Delay Timer 
                 56.  
                 Shaft 
               
               
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  illustrates a ship to shore gantry crane for loading and offloading cargo containers from ships. When loading, a container  10  on a chassis  12  is pulled under the crane by a tractor  14   FIG. 2 . Tractors are spring-less vehicles that are never used on the highway. Dock workers unlock the container  10  from the chassis  12 . A trolley  16  is positioned over the container  10  a head block,  18  and spreader,  20  are lowered into position and lock on to the container  10  which is then hoisted out on to the cranes boom  22   FIG. 1  and loaded onto a ship  24 . Sometimes the container  10  is not completely uncoupled and the chassis  12  and tractor  14  are hoisted in to the air. This has resulted in many serious injuries and equipment damage. This invention will prevent the tractor  14  from being hoisted making ship loading a much safer operation as well as reduce equipment damage. 
     The invention uses a microprocessor based controller  26 ( FIG. 3 ) installed in the tractor. The controller  26  constantly monitors the status of several sensors to determine if the tractor  14  has been lifted. The primary sensor is an inductive proximity switch  28   FIG. 4  mounted on a fifth-wheel lift cylinder  30 . The tractors  14  are equipped with a hydraulic lift system to raise and lower the front of the chassis so that the operator does not have exit the cab and climb down to the ground to raise and lower a set of landing legs  32   FIG. 3  when coupling or de-coupling from the chassis. This system powers a fifth-wheel plate  34  up and down using double acting hydraulic cylinders  30   FIG. 4 . When the tractors fifth wheel plate  34  is pulled upward by the chassis  12  it also pulls up the lift cylinders  30 . The lower end of the cylinder is clamped around a shaft  56   FIG. 5  that is connected to the tractors frame. The shaft  56  is 2 mm smaller than the cylinder clamp leaving a gap at the bottom. By drilling and installing a shielded inductive proximity switch  28  any upward movement of the fifth wheel assembly can be detected. Using this as the primary sensor the crane hoist can be stopped before the tractors  14  rear wheels have been lifted off of the ground. This is also before any lift is visually detected by the crane operator. Many injuries are caused when the rear of the tractor is lifted 200 mm or more and dropped jostling the operator. As backups the embodiment uses an ultrasonic sensor  36  mounted on the rear frame of the tractor  14 . It will send a digital signal to the tractor controller if the frame of the tractor  14  is lifted a predetermined distance off of the ground. The system also utilizes a dual axis tilt sensor  38  with digital outputs mounted on the tractor frame to sense tilt and roll that will trigger at predetermined angles. 
     An off delay timer  54   FIG. 7  is used to keep the system active for several minutes after the tractor has been shut down. The tractors engines are loud and the operators occasionally shut them off to talk to workers on the ground. This could leave them unprotected if the crane lifted them while the engine is off. 
     When a lift is detected, the crane is signaled via a multi-channel radio transmitter  40   FIG. 3  and received by a radio receiver  42   FIG. 2  with a discrete or relay output mounted on the crane. The receiver  42  is shown mounted under the trolley cab  16  but can be mounted anywhere on the crane where the cranes controller inputs are accessible. When the signal is received the receiver  42  will send a discrete output signal to one of the cranes programmable logic controller inputs. The cranes controller will stop the hoist and trolley motion and prevent further hoisting but will allow lowering until the fault is corrected. The multi channel radios are widely available through many manufactures, one is Abacom Technologies, Etobicoke, Ontario Canada. 
     The radio channel the tractor transmits on is determined by multi channel infrared emitters  44   FIG. 3  mounted on the ends of the spreader  20  that are received by an infrared decoder  46  with relay outputs. It functions similar to the remote controls in use for televisions, radios, and other devices. The emitters  44  are controlled by the spreader controller  52  that acts the same as pushbuttons on a remote control transmitter. There are several manufactures of these products including Infrared Remote Solutions Inc. Syosset, N.Y. When an infrared signal is received by the tractors decoder  46  it is decoded and the appropriate relay is energized sending a signal to a discrete input on the tractor controller  26  this tells the controller which crane to signal in the event of a lift. The spreader  20  can often be damaged during operations and can be detached quickly from the head block  18  and replaced with a spare to reduce the amount of time the crane is out of service. The spreaders  20  will also fit on multiple cranes, for that reason the emitters  44  cannot transmit a fixed identification code. The cranes identification is set by jumper wires in the head block  18  junction box  48 . The head block is permanently attached to the crane by the hoist cables. The identification signal travels through a messenger cable  50   FIG. 3  and to a spreader controller  52  mounted on the spreader. The spreader controller  52  determines the timing, duration, and identification output of the emitters  44 . Emitters are required on both ends of the spreader  20  because the tractor can approach from either direction. 
     To help eliminate the possibility of false triggers the cranes built-in controller will only accept the hoist deactivation for the first several meters of hoisting after locking onto a container on the dock. Also the tractor controller  26  will not be permitted to transmit a signal unless the infrared crane identification signal transmitted from the spreader  20  is present. The only exception to this is if two or more lift sensors are triggered, the tractor controller  26  will signal the last crane it received an infrared identification signal from. A display or mode lights on the dashboard of the tractor will keep the operator updated on crane identification numbers, system faults, and sensor status. 
       FIG. 6  shows a block diagram of wiring connections in the cranes spreader  20   FIG. 3  and head-block  18 . The spreader controller  52   FIG. 6  is a Programmable Logic Controller with digital inputs and outputs. It receives its crane identification signal through permanent jumpers in the cranes head-block junction box  48  transmitted through the messenger cable  50 . The controller sends an output to the infrared emitters  44  located on both ends of the spreader. The output controls the channel output, timing, and duration of the infrared emitters that acts as a key press would on a remote control. 
       FIG. 7  shows a block diagram detailing wiring connections between the tractors components. The tractor controller  26  is a Programmable Logic Controller with digital inputs and outputs and either a small display screen or status lights to keep the operator informed of the system status. Although there are many controllers that are acceptable I have chosen a Horner APG model XLT with a 3 inch touch screen, 2 gigabytes of data logging memory, and 1.2 ms scan time. Connected to the controller are several input and output devices. The first is an infrared decoder  46  that receives the crane identification number when a crane spreader is in range. The decoder  46  has relay outputs that energize when a signal is received, relay one equals crane one and so on. Next is a multi-channel radio transmitter  40  for transmitting a lifted signal to the crane. Multiple sensors inductive proximity  28 , ultrasonic  36 , and dual axis tilt  38  are connected to inputs on the controller. This embodiment uses extra sensors for added safety but one or more can be eliminated and still achieve the desired results. An off delay timer  54  will control power to the system. 
       FIG. 8  shows a software flowchart for the tractor controller. To start  57  the controller determines if a crane identification signal is being received. If it is, the controller will save the crane identification number into a buffer  58  for later use. It will also update the operator display  60  to show a crane present. It will then check to see if any lift sensors are triggered  62 . If no sensors are triggered it will return to block  57  and start the scan over. If one or more sensors are triggered it will get the crane identification from the buffer and transmit a lifted signal  64  on the proper channel. It will then log the date, time, and the sensor status into memory  66  for later retrieval. It will also update the display to show current status  68 . Moving back to  57  if no crane identification is received it will update the display to show no crane present  70 . It will continue to check the sensor status and if two or more sensors are triggered  72  it will get the crane identification number of the last crane from the buffer and transmit lifted signal  74 . It will then log the date, time, and the sensors tripped into memory  66  for later retrieval. It will also update the display to show current status  68 . 
     CONCLUSION, RAMIFICATIONS, AND SCOPE 
     Thus the reader will see the embodiment provides a faster and safer system that eliminates human error and can stop the cranes hoist before the tractor is lifted. Furthermore it provides additional advantages in that:
         it can react before the crane operator can see any lift, preventing the tractor operator from being jostled in the cab;   it provides a visual display for the operator that shows system status, crane identification number, system faults, and sensor status;   it provides logged data for later retrieval;   it is fully automatic and does not require any operator inputs;   it does not require any production robbing slowdowns;       

     Although the description above contains much specificity, this should not be construed as limiting the scope of the embodiments but merely providing illustrations of the presently preferred embodiment. For example the crane identification could be accomplished using large bar codes or long range RFID. The primary lift detection sensors could be pressure sensors in the tractors hydraulic system or mounted under the fifth wheel plate to sense a chassis is present. 
     Thus the scope of the embodiments should be determined by the appended claims and their legal equivalents, rather than by the examples given.