(1) Field of the Invention
This invention relates to ginning seed cotton. Builders of cotton gins have ordinary skill in this art.
(2) Description of the Related Art
The invention relates to an improved method and apparatus for removing seeds from a roll box of an operating gin stand at an accelerated rate, whereby the indigenous density of seed rolls is reduced and capacity of ginning stands is increased.
As is well understood by those familiar with the design and operation of the so called saw type cotton gin, a gin stand consists of a plurality of coaxially spaced saw blades or discs mounted in mutually spaced relation on a driven shaft and having projected there between elongated seed roll support members, commonly referred to as ginning ribs, or, more conveniently, ribs. The teeth of the saw blades extend between the ribs and engage the fibers of seed cotton as it is fed to the gin stand. The fibers are, in turn, pulled through ginning gaps, defined by the adjacent ribs, while passage of the seeds is precluded. The thus rejected seeds, along with fibers not engaged by the teeth, tend to accumulate in a comingled cohesive mass to establish a seed roll which is continuously rotated in response to the action of the saw blade action thereon. The seed roll is confined by head plates and scrolls which collectively form a cavity, commonly referred to as a roll box. The seed roll will basically consist of a center of ginned seed surrounded by a covering of seed cotton and lint. Of course, the lint or fibers carried by the blades through the ribs, is doffed or removed from the teeth and delivered to subsequent stations at which additional operations are performed.
The preferred diameter of the saw blades in my gin is 12" with a thickness of 0.045". The teeth are die cut with the leading edge straight and tangent to a circle with a radius of 4" and whose center is common to the center of the saw. The preferred speed of the saw is 800 to 850 rpm.
Currently, it is common practice to adjust the ginning rate of a gin stand to the discharge rate for ginned seed, rather than the rate the lint removal by the saw teeth occurs. The normal contours before this invention of the ginning rib and scrolls forming the roll box cavity limit the seed discharge rate for reasons which will be explained later. With this limitation, as the rate of flow of unginned cotton into the roll box is increased, the population of ginned seeds in the seed roll increases. Unless the seed discharge rate can be increased to match the inflow and the rate of lint removal, the density of the seed roll increases to the point that the disc brake effect of the mass against the saw blades increases the power consumption beyond a practical level.
When a gin stand is put into operation with an empty seed roll cavity, the cotton fibers are engaged by the saw teeth and are carried, along with the seed to which they are attached, to the rib gap where the seed are rejected. The fibers engaged firmly by the teeth pass between the ribs, or through the rib gap where they are doffed and conveyed by the doffing air to the next process. There is always a mass of fibers pulled from the seed and not firmly attached to the saw teeth, but are pulled into the rib gap. As additional loose fibers are pulled into the gap and accumulate ahead of the saw teeth, the mass is pushed upward in the gap between the ribs. It is this upward or forward movement of the fibers in the gap that starts the rotation and formation of the seed roll. To begin with, the seed roll is a comingled mass of seed in various stages of lint removal.
At the point where the saw blade enters the rib gap the rib spacing is narrow, with a gauge of 0.110" to 0.125". In order for the loose fibers which are pulled into the gap to move freely up the gap between the ribs, the gap must gradually widen to form a tapered opening. The upper section of the gap must be wide enough to permit all the loose fibers to be pulled back into the seed roll.
As the ginning action continues with the seed roll rotating, the ginned seed work their way to the core of the seed roll where they accumulate. The core builds until the ginned seed reach the surface where they mix with the incoming cotton. The established seed roll will basically consist of a cohesive mass with a center of ginned seed surrounded by this layer or covering of seed cotton and lint. As the seed roll approaches the saw, its surface is permitted to sag into the seed passage and the ginned seed are loosened, and discharge down the seed passage. Of course the saw penetrates the roll surface and releases seed to fall between the saws.
Before combing lint cleaners came into general use, the gin stand capacity was limited to a loose roll, or low density, because if the lint was packed tightly into the saw teeth the fibers would be kinked after doffing, and this condition resulted in the classer lowering the grade due to what was called "rough preparation". The price was penalized severely because these kinked groups of fibers dropped out as waste in the mill processing.
In the very early development of saw ginning, the manufacturers found that a saw spacing in the range of 3/4", along with very little sag in the seed roll into the seed passage would, with dry cotton, operate with a loose roll and discharge seed with low residual lint. Sometime in the mid 1800's, when it was found that cotton seed had some value, means to separate trash from the cotton as it entered the gin was introduced by having the saw drag it between huller ribs on its way into the seed roll. This limited the saw spacing to about 3/4" because the unginned cotton would not pass between ribs with closer spacing.
After the introduction of combing lint cleaners, which are almost universally used today, the gin stand no longer had to produce a smooth sample. The lint cleaners would comb out the kinks. This opened up new possibilities for increasing the production rate of the gin stand. This was first done by merely feeding more cotton in the unit and letting it operate with a higher density seed roll. This higher density forced more fibers into the saw teeth, thus removing more lint per saw blade. It was slowly learned that an improved ginning rate, since, with the higher density seed roll, the lint could be removed from the seed at a greater rate than the seed were being discharged. It was necessary to adjust the rate of feed to that of the seed discharge rate.
The contour of the gin rib and the seed roll scrolls were rather sacred, having been developed over a period beginning with the 1796 Holmes Gin. The first real effort to change the roll box contour to improve seed discharge, to take advantage of this higher rate of seed discharge was made by this applicant in the early 1960's. This basically amounted to having the seed roll in its rotation, approach the saw at a steeper angle to increase the sag of the roll as it passed over the seed passage. This caused a more drastic rupture of the seed roll surface, thus releasing the ginned seed that were on and near the surface of the roll. This was very effective and became a very popular gin stand conversion. These are still being sold over 20 years later.
Another step in improving the gin stand production rate was the use of a rotating cylinder in the core of the seed roll to increase the pressure of the seed roll mass against the saw to more thoroughly load the saw teeth, thus increasing the rate of lint removal. One such rotating cylinder consisted of a series of discs with serrated edges mounted on a tube or shaft at an angle so that they wobbled as they rotated. This along with the proper roll box contour was an effective means of applying the unginned seed to the saw teeth. This device is the subject of U.S. Pat. No. 3,091,001, which the applicant is co-patentee.
The applicant later introduced a method of removing the ginned seed through a perforated metal tube located in the core of the seed roll (U.S. Pat. No. 4,310,949). The tube also served to a great extent, the same purpose of increasing the pressure of the seed roll mass against the saw teeth, as did the rotating cylinder with discs as mentioned above.
These developments resulted in the reverse situation which were faced earlier, wherein the seed could be removed faster than the lint removal capacity. The next approach then was to increase the lint removal rate, by spacing the saws closer together. Although this did not necessarily increase the per saw capacity, it did result in an increase in per unit capacity. The same spacing is now reduced from 3/4" (0.75") mentioned to 9/16" to 5/8"(0.58").