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INVENTOR: Eli Whitney
TITLE OF INVENTION: Cotton Gin
ISSUE DATE: March 14, 1794

US Patent Class: 19/61

Eli Whitney

To all to whom these presents shall come, Greeting:

I certify that the annexed Writings and Drawings are True Copies of Original papers in this Office by Eli Whitney and still remaining therein:

In faith whereof, I James Madison, Secretary for the Department of State of the United States of America, have signed these presents, and caused this Seal of my Office to be affixed hereto, at the City of Washington, this Twenty fifth day of November, A.D. 1803, and in the Twenty eighth year of the Independence of the United States.

(signed) James Madison

Description of a New Invented Cotton Gin or Machine for cleaning and separating Cotton from its Seeds.

This machine may be described under five divisions, corresponding to its five principal parts: viz., 1st, The frame; 2, the cylinder; 3, the breastwork; 4, the clearer, and 5, the hopper.

1st, The frame, by which the whole work is supported and kept together, ought to be made of soft seasoned lumber, so that it may be firm and steady, and never become loose in the joints. Scantling four inches by these will perhaps be a staff of as suitable size as any. The frame should be of a square or parallogramic form, the width must answer to the length of the cylinder and the height and length may be proportioned as circumstances shall render convenient.

In the Drawing rendered, Fig. 1, is a section of the machine. A represents the cylinder; B, the breastwork; C, the clearer; D, the hopper.

II. The cylinder is of wood; its form is perfectly described by its shape, and its dimensions may be from six to nine inches in diameter, and from two to five feet in length. This cylinder is placed horizontally across the frame, in such manner as to give room for the clearer on one side of it, and the hopper on the other, as in Fig. 1.

Its height, if the machine is worked by hand should be about three feet four inches; otherwise it may be regulated by convenience. In the cylinder is fixed and (illegible) is sol large as to turn in the lathe without quivering. The axis may pass quite through the cylinder or consist only of gridgems, drawn with cement into each and, These must be a shoulder at B; Fig. 2, on each side the bearing or box to prevent any horizontal variation in the cylinder. The bearings of the axis or those parts which rest on the boxes must be rounded in a lathe, so that the centre of the axis may coincide with the centre of the cylinder. One end of the axis should extend so far without the frame as to admit the winch by which it is turned, to be connected with it at C, and so far at the other end as to receive the winch designed for putting the clearer in motion.

The brass boxes in which the axis of the cylinder derives consist each of two parts, c & d, Fig. 7. The lower part, d, is sunk into the wood of the frame to keep it firm and motionless, and the upper, c, is kept in its place by 2 small iron bolts, H, H, headed on the lower end at H. These bolts are inserted into the underside of the rail or scantling of the frame and continued up through both parts of the box. A portion of the bolts, as H, a’, should be square, to prevent them from turning. The upper part of the box, c, is screwed down close, with a nut on the end of each bolt. At c, is a perforation for conveying oil to the axis.

After the cylinder, with its axis is fitted and rounded with exactness, the circular part of its surface is fitted with both set in annular rows. The spaces d; e, f, g, h, Fig. 2 7 between the rows of teeth must be so large as to admit a cotton seed to turn round freely in them every way; and ought not to be less than seven sixteenths of an inch. The spaces k, l, m, n, o, Fig. 1, between the teeth in the same row must be so small as not to admit a seed or a half seed; they ought not to exceed one twelfth of an inch; and I think about one sixteenth of an inch at best.

The teeth are made and set in the following manner.

Take common iron wire about No. 12, 13, or 14. Draw it about three sizes less without annealing in order to stiffen it. Cut it into pieces four or five feet in length and straight in them. Then with a machine somewhat like that used for cutting nails, cut the wire into pieces about an inch long. In the jaws of this machine at ,o, Fig. 10, are fixed the two pieces of steel, d, d; which are pressed together as may be observed from the figures by the operation of a compound lever. These pieces of stub are so set in, that upon being pressed together, their approaching surfaces meet only on the side next to d, d; leaving between them a wedgelike opening, which enlarges, as the distance from the place of contact increases. Steel wire would perhaps be best, if it were not too expensive. On the side d,d, about an inch distant from the place of contact is fixed a guage. Then in forcing down the levers, the wire is separated, leaving that end of the wire next [to] the side d,d, out smoothly and transversely off and the end of the other part flutted like a wedge. The flutted end is then thrust forward to the guage and the same operation is repeated. In this manner, the teeth are cut of equal length withone end flutted and the other end directly off. Tlutting one end of the wire is beneficial in two ways: 1st, The flutted end of the teeth are driven into the wood with ease and exactness; and 2, it prevents them from turning after they are set. To prevent the wires from bending while driving, they are held in with pliers, the jaws of which ought to be about half an inch in width, with a corresponding transverse groove in each jaw. Thus, holding the teeth with a slight manner driven one by one into the cylinder, perpendicular to its axis. Then, with a tool, like a chisel or common screwdriver each tooth is inclined directly towards the tangent to that point in the circle into which it is inset, till the inclination is such that the tooth and tangent form an angle of about 55 or 60 Degrees. If this inclination be greater, the teeth will not take sufficient hold of the cotton; if it be less, there will be more difficulty in disengaging the cotton from the teeth after it is separated from the seeds.

When the teeth are all set they should be cut of an equal length. In order for this take a crooked gage, Fig. 8, having two openings, q, r; thie curvature of which corresponds with that of the cylinder. This gage is merely a crooked fork, the thickness of whose prongs or tines, as represented between s & t, Fig. 9, equalizes the length of the teeth, and is applied to the cylinder with one turn on each side of an (illegible). With a pair of cutting pliers, cut the teeth 1,2,3,, etc. off even with the gage; then slide it along to 6, 7, 8, etc., and so proceed till you have trimmed all the teeth to an equal length. This (illegible) put the cylinder into a lathe and with a file, bring the teeth to a kind of angular point, assembling a wire flattened cut obliquely. After the teeth are brought to a proper shape, smooth them with a polishing file and the cylinder will be finished.

Remarks. (though the dimensions of the cylinder may be varied at pleasure), yet it is thought that those described are the best, being more easily made and kept in repair than those of a larger size. The timber should be greater stuff, i.e., a greater of the trunk of the tree; otherwise,, it will crack in seasoning. It must also be wood of an equal density, such as beech, maple, black birch, etc. (illegible) and any other kinds of wood there are spaces between the grains which are not so hard as the grains themselves; and the teeth driven into those spaces would not stand sufficiently firm while the grains are so hard as to prevent the teeth from being driven without bending.

The breastwork, Fig. 11, and B, Fig. 1 & Fig. 2, is fixed above the cylinder, parallel and contiguous to the same. It has transverse grooves in openings 1, 2, 3, 4, etc. through which the jaws of teeth pass as the cylinder revolves; and its use is to obstruct the seeds while the cotton is carried forward through the grooves by the teeth. That side of the breastwork next the cylinder should be made of Brass or Iron that it may be the more durable. Its face or surface as Fig. 1, ought to make an angle with the tangent less than 30 Degrees. A tooth in passing from knofe to the breastwork, B, fastens itself upon a certain quantity of Cotton, which is still connected with its seeds. The seeds being too large to pass thru’ the breastwork are then stopped, while the cotton is forced thru’ the groove and disengaged from the seeds. Now if the point of the tooth enters the groove before the spool, or that part (illegible) the cylinder, it carries through all which it has collected in coming from k; but if the part of the tooth under the groove before the point, part of the cotton fastened on it will slied off; and this latter case is preferable as it helps to give the cotton a rotary motion in the hopper. The thickness of the breastwork or the distance from a to i, Fig. 1, should be about 2½ or 3 inches, in proportion to the length of the Cotton. It should be such that the Cotton which is carried thru’ by the teeth may be disconnected from that which is left in the hopper before it leaves the grooves; otherwise that which is carried partly through the breastwork will by the motion of that with which it is connected in the hopper become so collected and knotted at I, as to obstruct and bend the teeth. *

The under part of the breastwork next the cylinder ought, as has before been observed, to be made of Iron or brass. It may be cast either in a solid piece and the openings for the passage of the teeth cut with a saw and files; or in as many parts as there are spaces between the several rows of teeth in the cylinder and in form of Fig. 12, and the pieces set by means of a shank or (illegible); in a groove running lengthwise along the wooden part of the breastwork.

The breastwork described, if properly constructed, will it is thought answer every valuable purpose. But I shall mention one of a different construction which I have used with success and is made in the following manner:
(If a perforation about 3/16ths of an inch be made thru’ the breastwork at the upper part or end of each groove; the metal part need not be more than 3/8ths of an inch.)

Form a breastwork of the same shape and dimensions as the one before described, entirely of wood. Place a bar of wood one inch below the cylinder and parallel to it. Then with straps or ribs of is on brass or tinplate, connect the breastwork of wood with the bar below. The ribs or straps must be so applied as to sit close to the surface of the cylinder between the wooden breastwork and the bur; and of a width that will permit them to work freely between the annular rows of steel. That end of each strap which is fastened to the breastwork should divide widthwise into two parts, one of which should pass along the lower surface of the breastwork and the other (illegible) up its front. In Fig. 14, B is the wooden breastwork; D the bar below the cylinder; the dotted circles b, b, the cylinder; r, c, the strap; c, the place where the strap divides; and a’a’, a wood screwed or nails with which the strap is made fast to the bar of the breastwork, N. The clearer, C, Fig. 1, is constructed in the following manner. Take an iron (illegible) perfectly similar to that described as extending through the cylinder, except that it need not be so large nor fitted for the application of a wench. (illegible) together crosswise ar right angles two pieces of timber of suitable size and of a length about equal to the diameter of the cylinder, so as to make the four arms equal in length, and insert the axis thru’ o the centers of two crosses or frames of this kind. Set their distance from each other be one third of the length of the cylinder and make them fast on the axis. The arms of the two crosses are then connected by four pieces of the same length of the cylinder equidistant from the axis, and parallel to the same, and to each other. In each of the parallel pieces on the outside or side opposite the axis, a channel is made lengthwise before the reception of a brush. The brush is made of hog’s bristles, set in a manner somewhat similar to that of setting seeds in a weaver’s high Between two strips of wood about 1/8 of an inch in thickness and half an inch in breadth, is placed a small quantity of bristles; then a strong thread or twine is wound round the stiches clos to the bristles; then another quantity of bristles is inserted, etc., till a brush is formed equal in length to the cylinder. The bristles on the side a, a, Fig. 6, are smeared with pitch or rosin and seared down with a hot iron even with the wood, to prevent them from drawing out. On the other side, they are cut with a cissel to the length of about an inch from the wood. A brush of this kind is (illegible) in each of the before mentioned channels.

(*Perhaps nailing three straps together, would be better than winding them with twine.)

The b axis as well as axis of the clearer, are like those of the cylinder. The clearer is placed horizontal with the cylinder parallel to it and at such a distance, that which it involves the ends of the bristles strike with a small degree of friction on the cylinder’s surface. Its function is to brush the cotton from the teeth after it is forced thru’ the grooves and separated from its seeds. It turns in a direction contrary from that of the cylinder and should so far (illegible) it, as completely to sweep its whole surface.

The clearer with two brushes may be in a de’ by simply screwing upon the aqxis the board K, Fig. 4, and an other similar board on the opposite side which leaves spaces for the insertion of the brushes, s,s. The clearer may also be formed of a cylinder with grooves crossing lengthwise in it for the reception of the brushes or in any other way which may be convenient.

The number of brushes in the clearer is not material; let it be observed that the distance from e to r; Fig. 1, between the brushes must be at least 4 or 5 inches; otherwise the cotton will wind up round the clearer. The surface of the clearer moving much faster than that of the cylinder; the brushes sweep off the bottom from the teeth. The air put in motion by the clearer and the centrifugal force of the bottom disengage it from the brushes. Note: It is best to set the brushes in the grooves in such a manner that the bristles will make an angle of 20 or 25o, with the diameter of the clearer in the direction e, o, Fig. 1, by that means the bristles fall more perpendicularly on the teeth, strike them more forcibly and clear off the cotton more effectually.

The clearer is put in motion by the cylinder by means of a band and whirls. These whirls are plain wheels of solit wood about 2½ or 3 inches thick. Their periphery is a spherical surface swelling at the centre, and sloping off at the edges. To give them the proper shape, take a perfect globe of the same diameter as your intended whirl; inscribe upon it a circle dividing it into two equal parts; then cut the globe on each side parallel to the plane of this circle, and at this distance from it of half the thickness of your whirl. On these whirls (illegible) a leather band, the breadth of which answers to the thickness of the whirls. The band may be broader or narrower and the whirls thicker or thinner in proportion as the resistance to be overcome is greater or less. The reason for giving the whirls this shape is to secure them the better from being rebanded. A band of this kind always inclines to the highest place on the whirl, and is much less liable to be cast off from the work, when it runs on a spherical surface than when it runs in a groove in the periphery of the whirl.

(† The brushes may be fixed in a Stock which is movable by screws so as to bring them nearer or carry them farther from the cylinder.)

The whirls are four in number, and must be so arranged as to make their central planes coincident. The whirl E, Fig. 3, is fixed upon the whirl of the axis of the cylinder without the frame, and the button A, Fig. 3, is screwed on with the screw Driver B, to keep the whirl in its place I. is perpendicular to the axis of the clearer in the sam manner. P, Q, whose axes are pivots made fast in the frame, are false whirls added for two purposes. 1st, to make the clearer turn in a contrary direction from the cylinder; 2nd, for the purpose of doubling the band more completely around the small whirl I, so as to bring a greater portion of the whirl’s surface into contact with the band increase the force on and consequently turn the whirl more forcibly. The first of thesepurposes might be accomplished by the addition of one false whirl, but this second not so fully without two. The dotted line, w, v, represents the band. The distances of the whirls E, L, should be so proportioned as to produce a proper degree of velocity in the clearer. This axis of the whirl, Q, is fixed in a plate of Iron which is movable in a groove in the side of the frame, and the band is made tighter or looser by moving the plate. This arrangement of whirls produces the same movement as a cogwheel and pinion, with much less friction and discrepancy; and without the rattling noise which is always caused by the quick motion of cogwheels: V, One side of the hopper is formed by the breastwork, the two ends by the frame, and the other side is movable so that, as the quantity of Cotton put in at one time decreases, it may sliede up nearer the cylinder, and make the Hopper narrower. This is necessary in order to give the seeds a rotrary mode on in the hopper by bringing them repeatedly up to the cylinder till they are entirely stripped of the cotton D, Fig. 1, is a section of the movable part of the hopper. The part from H to I, should be concave on the side next the breastwork, or rather it should be a portion of a hollow cylinder. Between H and Y is a crate of wire thru’ which the sands and the seeds, as soon as they are thoroughly cleansed, fall into a receptacle below. The crate may be either forced in the frame or connected with the movable part of the hopper. The wires of which the crate is in a de should be large and placed perpendicular to the cylinder, that the bottom may turn the more easily in the hopper.

A few additional remarks will sufficiently show the construction, use and operation of this machine.

The bottom is put into the hopper I, D, H, k, a, a, s, Fig. 1, in as large a quantity as the cylinder will put in motion. Some of the seeds become stripped sooner than others. If it be black seed cotton, the seeds being smooth, will most of them fall through the crate as soon as they are clear, but a considerable part of the green seeds, which are thus disctiminated from being covered with a kind of green coat, assembling (illegible) will continue in the hopper. It will not answer therefore to supply it gradually as the quantity in it diminishes, because the seeds will soon grow (illegible) bruises, and by their constant interaction prevent the teeth from attaching themselves to the bottom so fast as they otherwise would; but one hopper full must be finished, the movable part drawn back, the hopper cleared of seeds and then supplied with cotton anew. There is a partition, y, w, under the cylinder; on the left hand of which, or the side beneath the hopper, the seeds fall, and the clean cotton on the other side. There may be a receptacle for the clean cotton in the frame, but it is best to have an opening through the wall or partition into a contiguous (illegible) in their place he end of the machine against this opening and let the cotton fly into a (illegible)., Or it may fall through an opening in the floor into a room below. This machine may be turned by horses or water with the greatest ease. It requires no other attendance than putting the Cotton into the hopper with a basket or fork, narrowing the hopper when necessary, and letting out the seeds after they are clean. One of its peculiar excellencies is that it cleanses the kind called green seed cotton almost as fast as the black seed. If the machinery is moved by water, it is thought it will diminish the usual labour of cleaning the green seed cotton at least forty nine (illegible).

The foregoing is a Description of the machine for cleansing cotton, alluded to in a Petition of the Subscriber, Dated, Philadelphis, June 20th, 1793, and loged in the Office of the Secretary of State, alledging that he the Subscriber is the inventor of said Machine, and signifying his desire of obtaining an exclusive property in the same.

(signed) Eli Whitney

Signed in the presence of
Chaunncey Goodrich, Counnsellor at Law, Hartford
John Allen, Counnsellor at Law, Litchfield

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