US3547420A - Production of carbonised fibres - Google Patents

Description

United States Patent [541 PRODUCTION OF CARBONISED FIBRES 8 Claims, 2 Drawing Figs.

[51] Int. Cl A. F27b 9/28 [50] Field of Search 263/3. 52; 34/ l 52 [56] References Cited UNITED STATES PATENTS 2,379,653 7/1945 Ridley 34/l52X 3,387,833 6/1968 Whittaker et al. 263/3 Primary Examiner.lohn J. Camby Attorney-Larson and Taylor ABSTRACT: ln the production of oxidised, e.g. carbon, fibres from organic material by heating, the fibres are moved continually, e.g. reciprocated, over guides which prevent the fibres from shrinking, the time spent between the guides being much longer than the time in contact with the guides.

IrIIIIIIIIIIII/r PRODUCTION OF CARBONISED FIBRES BACKGROUND OF THE INVENTION portions of the fibres which are in contact with the frame are not properly oxidized and cannot be used. in effect therefore, the maximum length offibre that can be produced is limited to the length of the frame. Since the process is conveniently carried out at a temperature of about 220 C. under closely controlled conditions, the size of the frame is normally limited by the size of the furnace.

It is an object of the present invention to provide a method and apparatus for the production of oxidized fibres which is not subject to this limitation.

SUMMARY OF THE INVENTION being carried out. One of these rollers is provided with means for causing it to rotate in a controlled manner and is desirably linked to the other roller by means of a chain and sprocket drive or some similar drive mechanism. A length of unoxidized 1 fibre is wound continuously over the two rollers so as to provide a single lap winding occupying substantially the entire length of the two rollers and conveniently each end of this length of fibre is tied back onto its immediate predecessor on the same side of the frame.

BRIEF DESCRIPTION OF THE DRAWlNGS In order that the present invention may more readily be understood, one embodiment of the same will now be described by way of example and with reference to the accompanying drawings wherein: FIG. 1 is a front view of the frameillustrating the same in a furnace shown diagrammatically and FIG. 2 is a side elevation of the frame taken in the direction of arrow ll of FIG. .1.

DESCRIPTION OF THE PREFERRED EMBODIMENT 7 Referring now to the drawings, it will be seen that FIG. 1 il- I lustrates diagrammatically a furnace 10 having an inlet ll and an outlet 12, together with a circling fan 13 driven by a motor 14. The arrangement is that air is drawn in at a controlled rate through the inlet 11 and is discharged through the outlet 12, together with volatiles emitted from the fibres. The furnace is also provided with electrical heating coils 15.

\ Located within the furnace 10 is a generally rectangular frame l6 comprising a base member 17, a top member 18 and two side'fmembers l9. Jou rnaled in the side members 19 are a pair of rollers 20,21 respectively at the top and bottom of the frame. In the preferred embodiment these rollers are 3% inches in diameter and are spaced 6% feet apart. Mounted upon the top member 18 of the frame is a reduction gearbox 22 driven by a shaft 23 which extends through the lid of the furnace. A shaft 24 extends from the gearbox 22 and carries a sprocket 25. A similar sprocket 26 is located upon one end of a spindle 27 for the roller 20 and the sprockets 25 and 26 are connected together by a chain 28. The other end of'the spindle 27 carries a'similar sprocket 29 whilstthe roller 21 also has a sprocket 30, the sprockets 29 and '30 being connected together by a chain 31. It will be seen that the arrangement;

such that drive transmitted through the shaft 23 is duly trans I mitted to both rollers 20 and 21. t

l in one arrangement the rollers are made of stainless steel with a good surface finish so as to be smooth and the fibres are kept in place by means of two grooved guide rollers 32 turning freely in trunnions 33 mounted upon the frame side members 19. In another arrangement (not illustrated) the side rollers 32 are not required and the rollers 20, '21 are themselves grooved.

In ,using the apparatus, a continuous tow of organic fibres,

for example 10,000 filaments'of polyacrylonitrile; are'wound -onto the rollers 20 and 21 and occupy about l8 inches of the length of these rollers so that a 1,000 foot length of fibre gives about a hundred turns of single lap winding. The two ends of the tow are knotted onto the next adjacent length of fibre on the same side of the frame. This arrangement permits the rollers to be rotated in a reciprocating manner so that the knots travel through approximately 360 around the rollers whereaften the direction of motion is reversed and the knots travel back to their'original positions. Since the knots travel in this way it follows that the remainder of the fibre also reciprocates between the two rollers. With the dimensions given above the-fibre spends about l4 times as long out of contact with the, rollers as it does in contact with them and this has been found to be completely" satisfactory. It is obviously desirable that the periodtout of contact with the rollers should be as long as possible but we have found that a reduction to l0 times is quite satisfactory. Similarly it will be seen that each piece of fibre takes approximately 2 minutes to travel in contact with the guides and'this period is again entirely satisfactory. It could probably be increased to 5 minutes if necessary. The fibre takes 15 minutes to travel through 360 before reversal is necessary.

In thearrangement illustrated the rollers are given a reciprocal movement but if instead of tying the fibres back to the next adjacent threads the two ends of the fibres are tied together, being taken over suitable guides, ,then alternative motions are possible. Thus although the reciprocating motion could still beused, since there is a closed length of fibre it wouldbe possible to provide unidirectional movement of the rollers until the knot returned to its starting position. Clearly knotting the two ends of the fibres together is only an expedient to restrain them and to ensure that the fibres remain in contact with the rollers and any other expedient would be possible. i

It must be emphasised that this invention relates solely to the initail oxidizing period when the fibres must be restrained from shrinking and that the precise process details are not important to the invention. Suitable process conditions are given in U.l(.- Pat. No. 1,110,791. I

lclaim: v

l. A process for the production of oxidized fiber comprising mounting a predetermined length of organic fiber on guides within a furnace, constraining the fiber from shrinkage, heating the constrained fiber in an oxidizing atmosphere in the furnace to oxidize thefiber, and moving the fiber continually over said guidessuch that an individual short length of fiber between the guides spends more time out of contact with the guides than in contact with the guides during the oxidation of said fiber.

2. The process of claim 1, wherein the fibres are reciprocated over the guides which are in the form of rollers.

3. The process of claim-1, wherein the maximum period of contact between the fibreand a guide is 5 minutes.

4. The process of claim 1, wherein the fibre spends at least 10 times as long out of contact with the guides as it does in contact.

5. The process of claim 1, wherein the fibres are wound in the form of a tow to give a single lap winding over the guides.

8. The process of claim 1, wherein the fibres are maintained in place on the guides by grooved rollers.

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