Development of the Roller Gin

The roller gin was the first mechanical device used for ginning cotton. It used two rollers similar to a latter-day clothes wringer that pinched and pulled the fibers from the seeds, to produce about 5 pounds of lint per day. This roller gin or Churka, as it was called, was the primary ginning tool until Eli Whitney's saw gin came along in 1794.

The saw gin did not replace the roller gin entirely. Although much slower, the roller gin is gentler to the cotton than the saw gin, whose serrated saws tend to break more of its fibers. Roller gins, therefore, continue to be used for ginning Pima cotton to protect its extra-long staple or length, a desirable quality that increases the value of the cotton fiber.

Even though the roller gin continued to be used for ginning extra-long-staple cottons, its low ginning rate made it too expensive to maintain and operate. In an effort to increase its ginning capacity, several gins were developed that improved the roller ginning rate, though not significantly. It wasn't until the 1960's, when the rotary-knife gin was developed at the Southwestern Cotton Ginning Research Laboratory in cooperation with gin manufacturers and private ginneries, that roller gins became more efficient and less expensive to operate.

The rotary-knife gin improved on the McCarthy gin invented by Fones McCarthy in 1840. It retained the McCarthy Gin's ginning roller and stationary knife, but replaced its reciprocating knife with a rotary knife that greatly increased the roller ginning rate. Compared to the McCarthy Gin which produces only 1/4 bale of lint an hour per stand, the rotary-knife gin can produce up to 1 1/2 bales of lint an hour per stand.

Research Programs in Roller Ginning

Roller Ginning in the United States is limited primarily to the Southwest Region of the Cotton Belt where Pima cotton is grown. Because of its geographic location, the Southwestern Cotton Ginning Research Laboratory is the only USDA ginning laboratory that conducts research in roller ginning.

First started in 1953 to study and develop ways to increase the ginning rate for roller gins, our program has expanded to include all aspects of the roller ginning process. Since then, we have developed not only a more efficient roller gin, but other new technology that could save gins thousands of dollars each year in operating expenses.

A research accomplishment that could make roller ginning more cost effective is a cooling nozzle (H) we designed to help prevent heat damage to the covering (I) on the ginning roller as it squeezes tightly against the roller. These covers are expensive to replace. By blowing air onto the ginning roller as it spins, this cooling nozzle keeps the cover's temperature down, preventing it from overheating and being damaged. Gins will thus be able to save in maintenance and repair costs. To further lengthen the life of the roller covering, we also developed a stronger roller covering material made from layers of bonded cotton that can withstand extended ginning longer than the walrus hides used before.

Another factor that contributes to the wear and tear of the ginning roller covering is the condition of the seed cotton itself. When too moist, cotton forms large clumps that can jam between the ginning roller and the stationary knife, often damaging the roller covering. At the Southwestern Cotton Ginning Research Laboratory, we are currently working on a computer control to help with the problem. If the gin stand becomes jammed, this computer control will recognize the problem and try to fix it either by altering the feeding rate, or in the case of a serious jam, by shutting down the stand to prevent any damage to the roller covering.

Another research accomplishment in roller ginning developed by our staff under our air-quality-control program was a dust hood for the roller-gin stand. This hood acts as an exhaust system to capture and remove the cotton dust air pollution generated by trash in the seed cotton from around the area of the stand where it is most intense, thereby contributing to a cleaner work environment.

Research has been essential to the growth and success of roller ginning. From the Churka to the rotary-knife gin, research has changed roller ginning from the slow process it was yesterday to the efficient process it is today. Research is still vital to roller ginning, a job we take seriously at the Southwestern Cotton Ginning Research Laboratory. As recognized leaders in roller ginning research, our goal is to continue to conduct the same comprehensive research programs that have made it possible for the ginning industry to remain competitive through the years.