Patent Publication Number: US-10759635-B2

Title: SIDAS—spreader impact damage avoidance system

Description:
TECHNICAL FIELD 
     This document describes an improvement on the boom/mast safety control system of mobile shipping container handlers. A mobile shipping container handler comprises a chassis that is connected to a container spreader via a boom or mast, with such handlers more commonly referred to as reach stacker or top pick container handlers. 
     BACKGROUND 
     Mobile shipping container handlers are used worldwide and are manufactured by numerous companies. They are commonly found at rail intermodal yards or container shipping ports. Operation of a container handler is performed by a person referred to as the operator. The operator uses various controls including a joystick to maneuver the spreader. Over the years, safeties have been built into the machine using electric relays and timers and/or computer systems, such as a PLC (Programmable Logic Control), to decrease the number of accidents caused by operator error. The safety logic surrounding hoist function is typically limited based on the following situations: 
     1) Is the machine locked onto a container? (Green light) 
     2) Is the machine unlocked from a container? (Red light) 
     3) Is the machine within its safety envelope? 
     The locked and unlocked information is determined by proximity sensors on the twistlocks that are located in the four corners of the spreader (some older machines use only two sensors, one for each arm). The machine safety envelope is determined based on the type of machine. On a typical top pick, the safety envelope is simply the maximum capacity of the machine and weight is measured with a load cell or a pressure sensor on one or both of the lift cylinders. On a reach stacker, the safety envelope is more complex due to significant changes in the center of gravity caused by the reach capability of the machine. The envelope is determined based on three sensor readings. These readings are: 
     a) Boom angle—Inclinometer sensor 
     b) Boom length—Cable reel with a potentiometer 
     c) Weight of the load—Load cells or pressure sensors on the lift cylinders 
     A calculation of the boom angle and length readings is performed repeatedly and the maximum lift capacity is adjusted based on that calculation. The weight of the load is then logically compared to the maximum lift capacity to ensure that the machine is still within its safety envelope. If any one of the aforementioned situations are not met, boom/mast function is limited. In the event of situation 1 or 2 failing to be met, all boom/mast hoist and lower functions are locked. In the event of situation 3 failure, boom/mast hoist is locked. 
     SUMMARY 
     One area of limitation that has been overlooked is in the regulating of hoist function immediately after attaching the spreader to a shipping container. The machine manufacturers expect the operator to operate the controls smoothly and slowly when initially hoisting a load. However, the increased demand for faster operation and higher container lifts per hour has resulted in many operators ignoring this expectation. This results in significant strain and impact forces on the spreader that were not intended. Embodiments of this document may resolve this discrepancy between manufacturer expectations and operator&#39;s actions. Through the use of existing sensors, additional programming logic may be added to the machine to limit the hoist functionality of the machine subsequent to attaching onto a shipping container. 
     A method is disclosed of operating a mobile container handler, which has a spreader mounted on an extendable boom or a mast and carriage assembly, the method comprising: a. monitoring whether the spreader is locked to the shipping container; b. monitoring whether the spreader is landed on the shipping container; c. limiting a hoist function of the mobile container handler when both of the following conditions are satisfied: i=the spreader is locked to the shipping container; and ii=the spreader is landed on the shipping container; and d. resuming a normal mode of the hoist function of the mobile container handler when all of the following conditions are satisfied: iii=the spreader is locked to the shipping container; and iv=the spreader is not landed on the shipping container. 
     A method is disclosed for use with a mobile container handler of the reach stacker or top pick type in which the limitation of hoist function immediately subsequent to attaching the container spreader to a shipping container is achieved by the following logic: a. Monitoring the locked or unlocked signals from the spreader twistlock position sensors, b. Monitoring the landed signal from the spreader seated pin position sensors, c. Limiting hoist function if the results from a &amp; b are: i. a=spreader attached to a shipping container, ii. b=spreader landed on a shipping container, d. Resume normal hoist function once the result from b becomes negative and the elapse of a prescribed amount of time (presumably 2 seconds but adjustable based on machine). 
     In various embodiments, there may be included any one or more of the following features: The mobile container handler comprises a chassis with a drive axle and a steer axle, and that is connected to the spreader by an extendable boom. The mobile container handler comprises a chassis with a drive axle and a steer axle, and that is connected to the spreader by a mast and carriage assembly. The method is performed using control signals from a controller. The controller comprises a PLC (Programmable logic control). The controller controls the hydraulic hoist directly by means of a PWM (Pulse Width Modulation) value. The hydraulic hoist is controlled indirectly by means of a pilot control valve. The pilot control valve is located inline on a hoist pilot pressure from a joystick that controls a hoist valve. The pilot control valve comprises a pressure control valve. The pilot control valve comprises a flow control valve. The pilot control valve comprises a directional control valve and a pressure relief valve. Performing the method using electric relays and timers. Resuming further comprises resuming the normal mode of the hoist function of the mobile container handler when all of iii, iv, and the following condition are satisfied: v=a prescribed non-zero amount of time has elapsed after condition iv has occurred. The prescribed non-zero amount of time comprises two or more seconds. The spreader comprises twistlocks for locking the shipping container. Monitoring whether the spreader is locked is performed using signals from position sensors on the twistlocks. Monitoring whether the spreader is landed is performed using signals from landed pin position sensors on the spreader. Limiting the hoist function comprises reducing the maximum power of the hoist function to 25% or less relative to the maximum power of the hoist function when in the normal mode. Retrofitting the mobile container handler with a controller programmed to carry out the method. The mobile container handler comprises a reach stacker or a top pick. A mobile container handler configured to perform the method. A controller programmed to carry out the method when installed on the mobile container handler. A reach stacker in which the machine comprises a chassis with a drive axle and a steer axle that is connected to the container spreader by an extendable boom. A top pick in which the machine comprises a chassis with a drive axle and a steer axle that is connected to the container spreader by a mast and carriage assembly. The logic is performed by a PLC (Programmable logic control) or similar computer system designed for use on mobile industrial equipment. The PLC or computer system controls the hydraulic hoist directly by means of a PWM (Pulse Width Modulation) value. The PLC or computer system controls the hydraulic hoist directly by means of a PWM (Pulse Width Modulation) value. The PLC or computer system controls the hydraulic hoist indirectly by means of a pilot control valve, comprises a pressure control valve, located inline on the hoist pilot pressure from the joystick that controls the hoist valve. The logic is performed using electric relays and timers. The electric relays and timers controlling the hydraulic hoist indirectly by means of a pilot control valve, comprising a pressure control valve, located inline on the hoist pilot pressure from the joystick that controls the hoist valve. The electric relays and timers controlling the hydraulic hoist indirectly by means of a pilot control valve, comprising a pressure control valve, located inline on the hoist pilot pressure from the joystick that controls the hoist valve. The pilot control valve comprises a flow control valve. The pilot control valve comprises a directional control valve and a pressure relief valve. 
     These and other aspects of the device and method are set out in the claims, which are incorporated here by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Embodiments will now be described with reference to the figures, in which like reference characters denote like elements, by way of example, and in which: 
         FIG. 1A  is a simplified 3-dimensional view of the spreader arms  15  inserted into the spreader body  10 . The spreader comprises two identical arms oriented 180 degrees to each other with a corresponding tube on the spreader body. 
         FIG. 1B  is a flattened end view of the apparatus of  FIG. 1A  with one of the spreader arms  15  inside the spreader body  10 . This is the left side of the spreader where the left arm extends from. The wear pads  20  are attached to the spreader body and spaces exist to facilitate movement of the arm while attempting to limit slack. 
         FIG. 1C  is a flattened end view of the apparatus of  FIG. 1A  with one of the spreader arms  15  inside the spreader body  10 . This is the left side of the spreader where the end of the right arm is visible when in the 20′ orientation. The wear pads  20  are attached to the end of the spreader arm and spaces exist to facilitate movement of the arm while attempting to limit slack. 
         FIG. 1D  is a simplified 3-dimensional view of the spreader arms  15  extended to the 40′ orientation. 
         FIG. 2  is a block diagram illustration of the methodology logic of an embodiment process. 
         FIG. 3  is a block diagram illustration of a PLC (programmable logic control) system that controls the hoist function directly using a PWM (Pulse Width Modulation) valve. 
         FIG. 4  is a block diagram illustration of a PLC system that controls the hoist function indirectly through a pilot control valve, comprising one of the following: 
       a. a pressure control valve, 
       b. a flow control valve or, 
       c. a directional control valve and a pressure relief valve. 
         FIG. 5  is a block diagram illustration of a relay timer system that controls the hoist function indirectly through a pilot control valve, comprising one of the following: 
       a. a pressure control valve, 
       b. a flow control valve or, 
       c. a directional control valve and a pressure relief valve. 
         FIGS. 6-9  are a series of end elevation views illustrating a method of using a spreader of a mobile container handler to land, lock, and lift a shipping container, using hooking pins to lock to the sides of the container. 
         FIGS. 10-13  are a series of end elevation views illustrating another method of using a mobile container handler to land, lock, and lift a shipping container, using twistlocks to lock to the top of the container.  FIG. 12A  is a section view taken along the  12 A- 12 A section lines of  FIG. 12 . 
         FIG. 14  is a top plan view illustrating a spreading action of the spreader to fit a shipping container, with the outline of the spreader in retracted and extended modes illustrated in solid and dashed lines, respectively. 
         FIG. 15  is side elevation view illustrating a reach stacker mobile container handler and a shipping container, with the shipping container in two positions, namely a) disposed on a ground surface (solid lines) and b) lifted above the ground and locked to the spreader (dashed lines). 
         FIG. 16  is side elevation view illustrating a top pick mobile container handler and a shipping container, with the shipping container positioned on the ground. 
     
    
    
     DETAILED DESCRIPTION 
     Immaterial modifications may be made to the embodiments described here without departing from what is covered by the specification. 
     Embodiments of this document are advantageously designed to address damage caused by abrupt operator inputs on the joystick of a reach stacker or top pick container handler when initially hoisting a shipping container. 
     Based on conventional logic, there is no limitation in the hoist provided the aforementioned situations are met. A lack of limitation to boom/mast hoist is the cause of significant spreader damage. The situation in question occurs immediately after the spreader is attached to a container. The machine is within its safety parameters and full hoist function is allowed. The operator can pull full power on hoist resulting in a sudden upward jolt on the spreader. This is a problem due to space between the spreader arms  15  and the spreader body  10 . The space exists to facilitate movement of the spreader arms inside the spreader body. Some of this space is removed with the wear pads  20 , but as the pads wear, the space increases. The sudden hoisting of the spreader causes impact points on various parts of the spreader body and/or the spreader arms based on the orientation of the spreader. On most models, the spreader body comprises two square tubes joined together with additional reinforcing steel, although other variations of spreaders may be used. The spreader arms can be in one of several orientations, including: 
     1) Oriented for 20′ containers, 
     2) Oriented for 40′+containers. 
     Referring to  FIGS. 1A-D , the impact location may change depending on the orientation of the spreader arms  15 . In the 20′ orientation, impact may occur on the bottom side (position  25 ) of the spreader body  10  where the spreader arms  15  are inserted into the spreader body  10 . In the 40′ orientation, impact may occur at the same location (position  25 ) as the 20′ orientation and on the top of the spreader body (position  35 ) on the inside where the arms meet the spreader body  10 . This last location of impact (position  35 ) is often severe, resulting in the spreader body  10  fatiguing and severe structural failure of the plate steel on the top center (position  35 ) of the spreader body  10 . The prior mentioned damage in this example has been occurring for decades with total cost of damage being unknown but presumably in the hundreds of millions of dollars. 
     Referring to  FIG. 2 , a method of operating a mobile container handler  60  is illustrated. Referring to  FIGS. 15-16 , the handler  60  may comprise a spreader  45 . Spreader  45  may be mounted on an extendable boom  64  ( FIG. 15 ) or a mast and carriage assembly  66  ( FIG. 16 ). The handler  60  may comprise a chassis  68  with a drive axle and a steer axle. The embodiments shown may also be commonly referred to as reach stacker ( FIG. 15 ) or top pick ( FIG. 16 ) style mobile container handlers  60 . In some cases a container handler  60  may be retro fitted with a suitable controller or other suitable control device programmed to carry out the method. 
     Embodiments of this document may eliminate the damage being caused by sudden hoist inputs by the operator subsequent to attaching to a shipping container. This may be achieved by adding additional logic to the safety system of the machine. Referring to  FIG. 2  the following logical steps may be used, for example added to the controller:
         1) Is the spreader locked onto a shipping container (stage  205 )? (A suitable indicator may be displayed to the operator, for example a green light)
           i. Referring to  FIG. 10 , the method may involve monitoring to see whether the spreader  45  is locked. Monitoring whether the spreader  45  is locked may be performed using signals from a suitable sensor, for example proximity or other position sensors  44  for twistlocks  40 , with locked information obtained from the locked or unlocked twistlock position sensors  44 .   
           2) Referring to  FIG. 2 , if yes to 1), is the spreader landed on a shipping container (stage  210 )? (A suitable indicator may be displayed to the operator, for example a yellow light)
           ii. Referring to  FIG. 10 , the method may involve monitoring to see whether the spreader is landed on the shipping container  30 . For example, the spreader may comprise of landed pin sensors  42  or other suitable sensors, and monitoring for unlanding may be performed by using signals from the landed pin position sensors  42 .   
           3) Referring to  FIG. 2 , if yes to 1) and 2), perform the following:
           a. Limit hoist function by reducing maximum hoist power (stage  215 ) to a prescribed amount (25% of maximum power but could be adjusted based on machine), while the spreader is locked to the shipping container, and the spreader is not landed on the shipping container.   b. Monitor landed signal (stage  220 ) and upon loss of signal, resume a normal mode of the hoist function (stage  235 ), or maintain reduced hoist power (stage  225 ) for an additional prescribed amount of time (stage  230 ), in this example 2 seconds is used, after which the controller may move to resume a normal mode of the hoist function, or restore hoist to full power (stage  235 ). (A suitable amount of time may be selected, and may be different based on machine, for example 1 second, 5 seconds, or more or less), and in some cases the time period may be adjustable by the operator or controller.   c. Return to start (stage  200 )   
               

     In previously mentioned embodiments, with the addition of the previously described logic, the operator will no longer be able to pull at full power on hoist and cause impact forces on the spreader  45  immediately after attaching to a shipping container  30 . This may in turn eliminate or reduce the damage cause by impact forces that were previously commonplace. 
     Referring to  FIGS. 3-5 , various embodiments are described of how to administer logic controls on hoist function. One embodiment achieves the desired function through the use of a Programmable Logic Control (PLC  305 ) or similar computer system designed for mobile container handlers  60 . Some embodiments achieve same through the use of electric relays and timers  325 . 
     Referring to  FIG. 3 , a method is described using a PLC  305  system to administer control logic on hoist function. For example, operator input from the joystick  300  may be converted to an electronic signal that is transmitted to the PLC  305 . The PLC  305  may thereafter output a PWM (Pulse Width Modulation) signal to a hoist valve, for example hydraulic valve  310 , which may be, for example, a PWM directional control valve. Hydraulic valve  310  delivers hydraulic fluid to the hoist cylinders  315  corresponding to the hydraulic flow indicated by the PMW signal. 
     Referring to  FIG. 4 , a method is described for using a pilot control valve  320  for administering logic controls on hoist function. A pilot control valve  320 , for example, may be located inline on a hoist and may include the following: 
     a. a pressure control valve, 
     b. a flow control valve and/or, 
     c. a directional control valve and a pressure relief valve. 
     In the example shown, operator input on the joystick  300  may be transmitted to a pilot control valve  320  via hydraulic pilot pressure. PLC  305  may transmit an electronic signal to the pilot control valve  320  if hoist function is permitted. Pilot control valve  320  may receive a signal from PLC  305  indicating that hoisting is permissible and thus valve  320  may allow pilot pressure from the input on the joystick  300  through the pilot control valve  320  to a hydraulic valve  310 . Hydraulic valve  310  may be a suitable valve, such as a directional control valve that delivers hydraulic fluid to the hoist cylinders  315 . 
     Referring to  FIG. 5 , a method is described where electric relays and/or timers  325  may be used to administer logic controls on hoist function. In the example shown, relays and timers  325  may transmit an electronic signal to a pilot control valve  320  indicating that hoisting is permitted. Operator input on the joystick  300  is transmitted via pilot hydraulic pressure to a pilot control valve  320 . Pilot control valve  320  may receive a signal from the relays and timers  325  indicating that hoisting is permissible and valve  320  may thus allow pilot pressure from the inputs on the joystick  300  through the pilot control valve  320  to a hydraulic valve  310 . If hoisting is permissible, the pilot pressure is permitted through the pilot control valve  320  to a hydraulic valve  310 , 
     Referring to  FIGS. 6-9 and 14-16 , an embodiment is illustrated of locking and lifting a shipping container using hooking pins  26  on the interior sides of fingers  22  of a spreader  45  for a mobile container handler  60 . Referring to  FIG. 14-16 , the spreader  45  is first positioned above a top face  30 A of the container  30 . Referring to  FIG. 14 , once in place adjacent the top face  30 A, the spreader arms  15  are extended or retracted as needed relative to the spreader body  10  in order to align the distal ends  15 A of each arm  15  into respective positions adjacent respective opposed ends  30 B of the container  30 , or to other suitable locations for locking the spreader  45  to the container  30 . 
     Referring to  FIG. 6 , each arm  15  may have parts, such as opposed fingers  22 , that are mounted to spread relative to one another, for example along an axis  50  transverse to an axis  52  of spreading action of the spreader  45 , in order to engage side walls  30 C of the container  30 . The fingers  22  may be extended or retracted as needed in order to extend fingers  22  into respective positions (shown in dashed lines in the figure) beyond the side walls  30 C of the container  30 . 
     Referring to  FIG. 7 , once the fingers  22  are in a suitable position, the spreader  45 , may be lowered into contact with (landed upon) the shipping container  30 . In the example shown, the spreader  45  is lowered onto the container  30  such that the position sensor pads  24  ( FIG. 6 ) engage the container  30  and send signals to the controller to alert the container handler  60  to stop lowering to prevent damage. The spreader  45  is now in the landed position. Referring to  FIGS. 7-8 , the fingers  22  may be converged sufficiently to engage the container  30 , for example by insertion of respective hooking pins  26  of fingers  22  into respective hooking pin receptacles  32 A defined in corner castings  32  of container  30 . The hooking pin sensors  28 , which may be suitable sensors such as proximity sensors, are used to detect the locked position shown in  FIG. 9 , indicating that the pins  26  are safely engaged and the container handler  60  can begin to lift. 
     Referring to  FIG. 15-16 , the control logic incorporated in the container handler  60  may permit the container handler to begin to lift the spreader  45  and attached container  30 , albeit using a limited hoist function, for example set at 25% of maximum power relative to the normal mode of operation of the hoist. The hoist function may be provided by operating one or more actuators, such as hoist cylinders  315  and extendable boom  64  ( FIG. 15 ), or mast and carriage assembly  66  ( FIG. 16 ), to raise and lower the container  30 . In some cases adjusting parameters to balance the collective center of gravity of the handler  60  and container  30  to avoid tipping. Referring to  FIG. 9 , once the spreader  45  and container  30  have been lifted a sufficient distance, the pads  24  unseat and the spreader  45  and container  30  enter the unlanded, locked mode shown. Referring to  FIGS. 15-16 , once the unlanded, locked mode is detected, and in some cases after the passage of a suitable amount of time, the control logic then enters a normal mode of the hoist function, permitting the hoist function of the container handler  60  to resume operating at up to maximum power. 
     Referring to  FIGS. 10-13  an embodiment is illustrated of locking and lifting a shipping container using twistlocks  40 . Twistlocks  40  may be configured to engage the container  30  in a suitable fashion. The twistlocks  40  in  FIGS. 10-13  are shown depending from fingers  22  of spreader arms  15 , but may be in other suitable configurations. Referring to  FIGS. 10-11 , fingers  22  may mount twistlocks  40  that engage top face  30 A of the container  30  for the purpose of locking and lifting. The spreader body  10  may be positioned so that the twistlocks  40  are aligned with respective receptacles  32 B, which may be defined on the top faces, of the corner castings  32  of the container  30 . In the example shown, spreader  45  is lowered into contact with (landed on) the shipping container  30  such that the twistlocks  40  enter the corresponding twistlock receptacles  32 B on the top face of the corner castings  32 . As twistlocks  40  enter receptacles  32 B, landed pin position sensors  42  engage the container  30 , and the controller may, upon receipt of signals from the landed pin sensors  42  indicating sufficient extension of twistlocks  40  into receptacles  32 B, instruct the appropriate mechanism on container handler  60  to stop lowering to prevent damage. The spreader  45  is now in the landed position. 
     Referring to  FIGS. 11-12 and 12A , the twistlocks  40  may enter the locked position, for example by rotating a sufficient amount such as ninety degrees into the position shown in  FIGS. 12 and 12A  in dashed lines. Referring to  FIG. 12 , the twistlocks  40  are engaged and in the landed locked position. Referring to  FIGS. 15-16 , from the locked and landed position, the control logic incorporated in the container handler  60 , for example in a suitable controller, may then permit the operator to initiate the container handler  60  to begin to lift the spreader  45  and attached container  30 , albeit using a limited hoist function, for example, set at 25% of the maximum power relative to the normal mode of operation. 
     The hoist function may be provided by operating one or more actuators, such as hoist cylinder  315  and extendable boom  64  ( FIG. 15 ), or mast and carriage assembly  66  ( FIG. 16 ), to raise and lower the container  30 , adjusting parameters to balance the collective center of gravity of the handler  60  and container  30  to avoid tipping. Referring to  FIG. 13 , once the container has been lifted a sufficient distance, the landed pin sensors  42  unseat at least partially, upon which the spreader  45  and container  30  may enter the unlanded locked mode shown. Referring to  FIGS. 15-16 , once the unlanded lock configuration or mode is detected, the control logic enters a normal mode of the hoist function, permitting the container handler  60  to resume operating at up to maximum power. In some cases the control logic incorporates a further condition precedent to permitting maximum power, namely the elapse of a suitable prescribed non-zero amount of time has elapsed after the spreader  45  and container  30  enter the unlanded locked position. Signal flow may be through the controller or through direct connections between parts. 
     In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite articles “a” and “an” before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.