Piston Pump Helps Drive Cotton Module Loading Procedure
- Sunday, 01 April 2007
World cotton production in 2006/07 is forecast at 115.7 million bales, and global cotton consumption is forecast at a record of nearly 121 million bales, with 13.2 million acres dedicated to cotton in the United States alone. Cotton is one of the most heavily traded commodities on the world market, and whose value is influenced by how fast the product leaves the field and gets to the gin for processing into fiber. Module Truck Systems (MTS, Lubbock, TX) designed a specialized truck, a cotton module mover, to facilitate quick transportation of cotton from the field to gin yard, using the Heavy Duty Series 2 Hydrostatic Pump from Eaton Corp. (Cleveland, OH) to drive the loading chains that holds the raw cotton as it loads into the trailer bed.
MTS uses the hydrostatic pump to drive a single drive motor that runs chains involved in the load process. MTS, already using other Eaton products, tapped the Series 2 due to individual end-users habitually overrunning existing pumps, causing cavitations and eventual pump failure. The Series 2 pump’s cast iron, single piece pump housing adds to its structural strength, and, additionally, the unit has a higher RPM rating in the required displacement. A structurally stronger pump allowed MTS module movers to run their input shafts at high speeds, enabling the truck to load faster in fields with loose or muddy soil not conducive to the loading process. The semi-automated cotton module loading process is accomplished using a control system that interfaces the pump, mounted on the power takeoff system, with electro-proportional (EP) control. The EP control provides repeatable and reliable pump function via an electrical interface.
After harvesting, raw cotton is either loaded directly onto trailers and shipped to the gin or processed by a machine called a module builder that compresses harvested cotton in large, rectangular “blocks” called modules, which are then temporary set to the edge of the field. Cotton modules, 32 × 8 × 8' can weigh on average 16,000 to 25,000 lbs but can be as much as 37,000 lbs. One module can produce up to 13 to 20 bales (one bale can weigh up to 650 lbs) of ginned cotton. A module mover, measuring 48.5 × 9 × 14.5', is legally defined as a motor truck, semitrailer, or a truck tractor in combination with a semitrailer, equipped with a self-loading bed and is designed and used exclusively to transport field-manufactured cotton modules a cotton gin. A cotton module is shaped to the proportions of a module mover’s trailer and is loaded as a unit directly into the vehicle.
Cotton module trucks are based on the design of hay loading trucks, where the bed of the truck tilts back and rolls under the payload to load it on to the trailer bed. Before cotton module trucks and their load procedures were developed, a low volume of raw cotton reaching the gin yards hampered the entire cotton industry with an ultimate result being low production levels of finished cotton fiber. Gins even ran out of cotton between shipments. Cotton yields likewise remained low to avoid a surplus rotting in the fields or blowing away. With the advent of the module truck, ten to fifteen bales of unprocessed cotton and entire cotton modules can be loaded in a matter of minutes. A gin could then stockpile a surplus amount of cotton modules and so never be concerned about running out of cotton to gin. This opened the door for the development of high-speed ginning equipment that until then was unnecessary because the low volume of cotton — higher speed gins would run out of cotton and sit idle.
During a loading procedure, the cotton module mover leaves the road and drives directly to the modules in the field. Modules are not pulled onto the truck; instead, the bed literally continuously slides underneath the module and “scoops” it into the trailer during the loading process. The driver lines the trailer up with the module and hydraulic lift cylinders on the outside of the chassis raise at an angle the bed of the truck (similar to a dump trunk) to an overhang of 17' feet so that the back of the bed touches the ground. The truck backs up to the module so that the back of the bed slides under the edge of the module. Chains that move opposite to the trucks direction catch and hold on to the module, lifting it as the truck moves backward; these chains are synchronized to match the speed of the truck. A vane motor and the hydrostatic pump move the chain drive. The pump works in conjunction with an electronic controller that controls the displacement of the pump, and therefore, the chain drive, proportional to the speed of the truck. Chains moving too quickly would stretch or shred the module. If too slow, the chains could not load the module fast enough and module mover would push the module over. When the module is fully loaded into the module mover, the bed is exactly where the module used to lie on the field. The bed chains automatically stop when the module has reached the front of the truck and the operator is not required to stop the truck when the module is completely loaded onto the bed. The driver monitors the process via the cab mirrors to ensure proper alignment and that a minimum of soil is picked up with the module.