Patent Publication Number: US-7707692-B2

Title: Control system for roller gin

Description:
BACKGROUND 
   In the field of cotton ginning, there are two major systems currently used: saw ginning and roller ginning. Saw ginning is by far the most commonly used system because of its much higher capacity also termed rate of processing. Roller ginning on the other hand has been a much slower process and therefore more expensive, but, it is less aggressive than the saw ginning process and therefore better preserves the fiber staple length and produces fewer “neps” which are tiny entanglements of the fibers. Laboratory tests have proven that the roller ginning process may be dramatically increased in processing rate making it much more competitive with saw ginning cost-wise. This combination of the more economical high capacity ginning and the superior fiber quality of roller ginning is making roller ginning the method of choice for raw cotton markets desiring high quality fiber. While the recently proven much higher roller ginning rates are feasible, these ginning rates cannot always be maintained on all cotton varieties (cultivars) and all incoming seed cotton conditions. There are some varieties that do not lend themselves to the high capacity roller ginning process and will choke the gins at the highest feed rates into the gins. Merely reducing the rate of feed of these seed cottons to the gins results in overheating of the ginning roller. This overheating has serious consequences such as shortened ginning roller cover packing life, and in extreme cases complete destruction of the ginning surface of the packing roller. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide remedies to allow roller ginning of various cultivars with apparatus that adjust the speeds of the critical revolving components of the roller gin and the force pressing the gin roll against the stationary knife to optimize the ginning rates of the respective varieties and conditions of cotton. It is a further object of this invention to automatically adjust the speeds of the critical revolving components with the use of sensors indicating the need for changing the speeds and contact force of these components. It is a further object of the current invention that the sensors used to indicate the need for changing the speeds of the critical rotating components include as needed: heat sensors, load sensors on the rotating components, pressure sensors on the gin roll relative to the stationary knife, rotational speed sensors, or sensors indicating the presence or absence of matter in a selected space. A still further object of the current invention is to optimize the ginning rate for each seed cotton condition through algorithms employing various combinations of inputs from the above mentioned sensors and monitors. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The Figures illustrate a typical roller gin having a plurality of sensors strategically located to monitor the operational conditions in the gin. 
   

   DESCRIPTION OF A PREFERRED EMBODIMENT 
   Current roller gins include three vital elements: a ginning roller covered with fibrous material, a stationary knife pressed against the ginning roller surface with considerable pressure, and a rotary knife about two and three-quarters inches in diameter having up to six radial blades equally spaced from each other. Seed cotton is dropped onto the surface of the rotating ginning roller, which carries the cotton to the stationary knife drawing the fibers under the edge of the knife. The knife edge strips back the seeds thus pulling the fibers from the seed. As the seeds accumulate on the edge of the stationary knife, the blades of the rotary knife periodically sweep the seeds away from the stationary knife. 
   Referring now to the Figure for a better understanding of our invention, as stated, we will describe the same in association with a more or less standard roller gin feeder combination. Thus, at  10  we show a seed cotton feeder to which seed cotton is delivered from a conveyor-distributor, not shown, through a chute indicated at  11 . The feeder  10  delivers the cotton to be ginned to a roller gin indicated generally by the numeral  13  on shaft  27  via slide  57  and guide  26 . Trash removed in feeder  10  is carried away by conveyor  51 . A suitable conveyor is located beneath the gin to carry away seed. The lint removed from the seed is discharged from the back of the gin through a lint flue  15  having a suction fan  16  connected thereto. 
   Referring to the Figure it will be understood that the gin embodies the usual framework or box-like enclosure  17 . Mounted in the gin  13  on shaft  27  is a driven ginning roll  18  the outer surface of which is covered with a fibrous material  19  as is understood in the art. The ginning or stationary knife is indicated at  21  and is mounted on relatively heavy supporting framework  22  which spans the gin from end to end so that the knife  21  is coextensive in length with the roll  18 . Roll  18  may be driven by a motor connected by appropriate belts and sheaves as is well known in the art. At  23  we show what is known in the trade as a rotary knife and which is driven in the direction of arrow  24  by a motor. The rotary knife  23  also is substantially the length of the roller  18  and stationary knife  21 . 
   As noted above, a substantial problem exists in the art relative to cotton varieties and conditions that do not lend themselves well to the high capacity roller ginning process and the known solutions create overheating problems along the roll  18 . As seen in  FIG. 1 , lint cotton is carried on the surface  19  past the stationary knife  21  and exits through conduit  15 , such that the roll surface  19  is substantially free of lint cotton as it traverses the arc from conduit  15  to the feeder slide  57 . In this region we have placed a sensor  71  which is designed to determine the temperature of the surface  19  of ginning roll  18 . Sensor  71  is preferentially a non contact sensor designed to monitor and note the spectral emissivity of the surface  19  to determine whether the roll is within the proper temperature regimen. Alternatively, an internal sensor, built into ginning roll  18 , could be used. Sensor  71  may be a set of sensors spaced along the length of roll  18  and offset from the roll at a distance such that each adjacent sensor overlaps marginally with the sensors on either side thereof or it may be a traversing sensor or sensors that travel the length of the roll  18 . It will be appreciated that sensor  71  may be selected from the available categories of thermal based bolometers, thermocouples or thermopiles, and pyrometers or pyroelectric, and optical pyrometers. Electrical output options for infrared temperature sensors include analog current, analog voltage, analog frequency, serial, parallel, other digital, and switch or alarm. In either event sensor  71  should have output to a control logic  77  which can initiate an alarm to an operator at a selected temperature threshold and can initiate shutdown of the gin if necessary. However, the goal of the invention is not to present an alarm or shut down but rather generate an electric signal, which corresponds to a particular condition or temperature to control the gin parameters to avoid high temperatures and take corrective measures when high temperature changes are encountered due to changes in the seed cotton, extraneous matter, or fiber presented for ginning. 
   It is to be understood that the speed of roller  18  and rotary knife  23  are important factors in the efficiency of ginning cotton and that the speed of these elements should be varied as a function of the rate of feed of the seed cotton through the feeder  10  to the gin. When difficult to gin cultivars are introduced to the gin, the feed rate will likely become too high and the roll  18  and rotary knife  23  will not efficiently gin the seed in which case the seed cotton may accumulate on slide  57  and the seed exiting over knife  21  will contain excess fiber. Additionally, the power required to turn the ginning roll and rotary knife will increase. Accordingly, sensors  18   s  and  23   s  are connected to the motors or to the drive system to measure the load on the gin roll motor or rotary knife motor. Sensors  18   s  and  23   s  may be wattage or torque transducers. Where the roll and rotary knife are driven by the same motor  55 , utilizing different gearing or belting outputs, then the load may be measured on the single power source. Further, sensor  23   s  may be configured to measure the power required to drive rotary knife  23 . As with temperature sensor  71 , the output of sensors  18   s  and  23   s  are input to control logic  77 , which may be resident in a PC or other industrial programmable controller, and may be used to generate control signals controlling the rate of feed of the feeder  10 , the speed of the roll  18 , or the speed of rotary knife  23 . That is to say, varying power requirements may be used to indicate less than optimal operation of the gin, necessitating changes in the feed rate of cotton to the gin and/or changes of the speed of the roll and/or rotary knife. 
   In addition to temperature and power measurements, the efficiency of the gin with various cultivars and conditions may be indicated by the accumulation or lack thereof of seed cotton on roll  18  up stream of the rotary knife  23 . Accordingly sensor  81  is positioned upstream to detect the quantity of seed cotton accumulated on the roll awaiting ginning. Sensor  81  may be selected from the available categories of photocells. Variations from the optimum quantity are output to control logic  77  which again controls the feed rate of feeder  10  and the speed of roll  18  and rotary knife  23 . Further, the efficiency of the gin may be indicated by the quantity of fiber left on the seed after it passes the stationary knife and is released from the roll  18  and rotary knife  23 . This value can be determined by a sensor  91  positioned downstream of the stationary knife and in position to measure the reflectivity of the cotton seed. A suitable sensor can be selected from the categories of retro-reflective photocells. If excessive fiber remains on the seed then the speed of roller  18  and/or rotary knife  23  can be adjusted which requires a commensurate adjustment of the rate of feeder  10 , thus sensor  91  must also have an output to control logic  77 . 
   Still another factor affecting the efficiency of the roller gin is the force pressing the ginning roll against the stationary knife which is exerted by air cylinders on each gin roll end journal which supports roller shaft  27 . Excessive force produces overheating of the gin roll. Inadequate force allows slippage of fibers between gin Roll and stationary knife and loss of ginning rate. Accordingly, pressure sensors  101  are mounted in the compressed air lines adjacent the air cylinders. The pressure signals are output to control logic  77  which may combine the pressure signals with the signals from the other sensors  18   s ,  23   s ,  81  and or  91  to modulate the speed of roller  18  and/or knife  23  and feed rate from feeder  10 . Control logic  77  may also modulate the pressure output of the compressed air regulators at said air cylinders. 
   The rate of speed of the feeder  10  may be linear or may be computed from a non linear mathematical formula contained in software in control logic  77  using one or more of the values provided by sensors  18   s ,  23   s ,  77 ,  81 ,  91 , or  101 . Specifically, the formula depends on the interaction of the signals from the sensor or sensors employed relative to the respective components to optimize the ginning rate for each condition of seed cotton being processed while avoiding the risk of damage to the gin roll or stoppages. Exemplary formulas showing the relationship between gin roll speed in rpm (GRS), gin roll temperature (GRT), and feed rate as a percentage of maximum rate (FR) are as follows and are based on operating the roll at 400 rpm or lower.
 
 FR  %=(GRS/4)−25 where 200&lt;GRS&lt;400 and  FR &amp;GRS= O @GRS&lt;200
 
GRS=400−(GRT−225)×16 where GRT&gt;225
 
And FR %=0.25[400−(GRT−225)×16], thus at a sensed temperature of 240 degrees F., the Feed rate would be:
 
FR %=0.25[400−(240−225)×16]=160.@ GRS&lt;200,FR=0. Note−@ GRS&lt;200 RPM,GRS also drops to 0 RPM and switch on roller gin actuates air cylinders on gin roll to back away gin roll from stationary knife.
 
   While the invention has been described generally, it is to be understood that various combinations of sensors and control algorithms may be employed without departing from the scope of the appended claims.