US3698865A - Method and apparatus for the treatment of filamentary material - Google Patents

Abstract

FOR THE PRODUCTION OF CARBON FILAMENTS OF HIGH TENSILE STRENGTH AND MODULUS OF ELASTICITY, A METHOD AND APPARATUS IS PROVIDED FOR FEEDING A CONTINUOUS THREAD OF FILAMENTARY MATERIAL IN A HELICAL PATH AROUND A ROLLER CAGE WHICH IS ENCLOSED IN A FURNACE FOR CONTINUOUS PYROLYSIS TREATMENT OF THE THREAD.

Description

Oct. 17, 1972 J. ZBRZEZNIAK 3,698,865

METHOD AND APPARATUS FOR THE TREATMENT OF FILAMENTARY MATERIAL Filed June 30, 1969 5 Sheets-Sheet 1 Oct. 17, 1972 J. ZBRZEZNIAK I 3,698,865

METHOD AND APPARATUS FOR THE TREATMENT OF FILAMENTARY MATERIAL Filed June 30, 1969 3 Sheets-Sheet 2 Q m o .3 53 6'3 3 T i I Och 1972 J. ZBRZEZNIAK 3,698,

METHOD AND APPARATUS FOR THE TREATMENT OF FILAMENTARY MATERIAL Filed June so, 1969 s Sheets-She et s United States Patent Office 3,698,865 Patented Oct. 17, 1972 US. Cl. 23209.1 3 Claims ABSTRACT OF THE DISCLOSURE For the production of carbon filaments of high tensile strength and modulus of elasticity, a method and apparatus is provided for feeding a continuous thread of filamentary material in a helical path around a roller cage which is enclosed in a furnace for continuous pyrolysis treatment of the thread.

This invention relates to a method of and an apparatus for maintaining under longitudinal tension a thread of filamentary material exposed to pyrolysis treatment in the production therefrom of carbonaceous filamentary material.

It is known to produce carbon filaments, having very high tensile strength and modulus of elasticity, by the controlled pyrolysis of carbonisable filamentary material, such as threads composed of organic filaments, particularly polymers or co-polymers of acrylonitrile.

It is an object of this invention to prevent linear shrinkage of a thread of filamentary material whilst effecting exposure of the thread to continuous controlled pyrolysis treatment, such as in a furnace through which the thread is passed, in the production of carbon filaments, generally called carbon fibres.

.According to the invention, a method of maintaining the thread under longitudinal tension comprises continuously delivering the thread lengthwise to be wound in spaced convolutions round a cage formed by at least three rollers the rotational axes of which are oblique to the longitudinal axis of the cage and positively rotating at least one of the rollers so as to draw the thread around the cage in a substantially helical path, the thread convolutions each extending in contact with an arc of the surface of each roller transversely to the rotational axis thereof and substantially tangentially from roller to roller.

The term thread includes continuous filament yarns and staple yarns of suitable carbonisable material such as a polymer or co-polymer of acrylonitrile or a viscose rayon. Also, although individual filaments of the material are preferably of substantially circular cross-section, the thread may be of various cross-sectional shapes, including a somewhat (flat or tape form, for example a band of filaments somewhat spread laterally.

For best results, in terms of a constant rate of feed of the thread to and from the roller cage and regularity of the spaced convolutions of the thread, the rollers should be identical and journalled by their ends equally spaced around coaxial pitch circles of the same diameter, the ends of the rollers at one end of the cage being all set around their pitch circle out of parallel alignment with the other ends by a very small angle so that the rollers all have the same small obliquity to the axis of the cage. The speed of the rollers should be uniform and constant and this can be achieved by a chain drive in common, for example.

All of the rollers in a cage need not be positively driven and some may free-wheel provided that sufficient rollers are driven to wind the thread evenly and smoothly.

Apparatus for carrying out the method of the invention preferably comprises a cage consisting of a frame and at least one set of at least three rollers journalled in the frame by their ends in bearings equally spaced around coaxial pitch circles of the same diameter as between one end of the set of rollers and the other, the bearings of the respective set of rollers at one end of the frame being mounted on a carrier which is pivoted coaxially with said pitch circles and provided with means for setting the carrier in an angularly adjusted position about its pivotal axis.

Two or more sets of rollers or roller cages can be provided coaxially, one within another, with independent drives or a drive in common. With such an arrangement, one thread can be passed around the rollers in series or two or more threads could be passed around respective sets of rollers for simultaneous treatment.

The invention is illustrated, by way of example, on the accompanying drawings, in which:

FIG. 1 is an end elevation of a simple apparatus,

FIG. 2 is a sectional elevation on the line II-II of FIG. 1, and

FIG. 3 is a diagrammatic end elevation, somewhat similar to FIG. 1, to illustrate use of multiple sets of rollers As shown by FIGS. 1 and 2, three cylindrical rollers, 1, 2 and 3 are arranged as a cage symmetrically about and at an equal distance from an alignment shaft 4. The rollers are journalled in pairs of self-aligning bearings 5 which are mounted on a frame wall 6 at one end of the rollers and a pivotally adjustable carrier plate 7 at their other end. The alignment shaft 4 is located in a pair of bushes 8 and 9 mounted respectively in frame walls 6 and 10 which are thus accurately aligned on the frame base 11.

The plate 7 can pivot about the rim 9a of the bush 9, as on a bearing journal, and studs 12 are set in the plate and protrude through arcuate slots 13 in the frame wall 10 so that the plate can be angularly adjusted and looked against the frame wall 10 by tightening nuts 14.

The rollers extend beyond the frame wall 6 so that a suitable drive, for example a sprocket and chain drive (not shown), may be connected thereto to rotate the rollers at uniform speed and in the same direction.

In use, the pivoted plate 7 is turned slightly, to give the rollers a small inclination, away from mutually parallel relationship, so that they are slightly oblique to the longitudinal axis of the cage represented by the alignment shaft 4. The angle of adjustment required to give an effective helix angle is very small. For example, with rollers of a length of 2 m. substantially less than 1 of adjustment will suffice. After adjustment, the plate 7 is locked to the frame wall 10 by tightening the nuts 14.

A leading loop of a thread of filamentary material 15 is then tied around the roller cage and the roller drive is started. The inclination and rotation of the rollers causes the loop to be fed lengthwise of the rollers, building up a helical winding behind the loop and along the cage. The thread 15 passes over an arc of the surface of each roller, transversely to the axis thereof, and extends tangentially from roller to roller but, because of the inclination of the roller axes, each convolution of the thread progresses sideways along the cage so that a helical winding is built up. Thus, the filamentary material is not subjected to lateral drag when in contact with the rollers, the advance of the thread along the cage taking place between the rollers.

When a complete helical winding of the thread has been built up on the roller cage, the leading loop is untied and the leading end 15a of the thread is paid out to be attached to a take-up spool, or the like, for the eventually carbonised thread.

The cage loaded with the helically-wound thread is then enclosed in a furnace for pyrolysis treatment, in the known manner, during which the rollers are driven and thread is continuously fed to and from the apparatus. The driving speed of the rollers is controlled to provide the required time for treatment of the thread while it is passing around the roller cage in the furnace.

During treatment, particularly in the initial stage of the pyrolysis treatment, the tendency of the thread to shrink may be very strong and therefore, to withstand the heavy load imposed by a large number of convolutions of thread around the roller cage, the rollers must be strong and rigid and supported in ample bearings.

For furnace temperatures up to about 400 C., the rollers and other parts of the apparatus may be made of metal, for example steel, but for higher temperatures refractory materials such as graphite or mechanical ceramics may be used in the construction or protection of parts of the apparatus.

Due to the obliquity of the rollers, the circumference of the roller cage, i.e. the shortest distance around the rollers, reduces slightly towards the mid-lengths of the rollers so that the intermediate convolutions of the thread may be able to shrink slightly more at the middle of the roller cage than at the ends. Such shrinkage may be negligible but it could be offset by using rollers of convex longitudinal profile, i.e. barrel-shaped rollers. For special effects, in controlling or permitting shrinkage for example, specially profiled rollers, either convex or concave, i.e. waisted, may be used.

In the apparatus shown by FIGS. 1 and 2, only three rollers are provided but a larger number of rollers may be used and also multiple sets of rollers as illustrated diagrammatically in FIG. 3.

FIG. 3 shows three generally coaxial sets of four rollers A B and C Each set of rollers constitutes an individual cage with fixed-location, self-aligning bearings at one end, in a frame wall corresponding to the wall 6. The bearings at the other end are mounted on an angularly adjustable carrier plate, corresponding to the plate 7, for each set. The bearings of each set of rollers are located on equal coaxial pitch circles and each carrier plate can be independently angularly adjusted to give its respective set of rollers a required obliquity.

A thread 15 is first led to and looped around one end of the innermost set A of rollers and helically wound thereon, as described above with reference to FIGS. 1 and 2. From the other end of the set A, the thread is then led to one end of, and similarly wound on to, the middle set B and then the outer set C before the end 15a of the thread is led away for attachment to a take-up spool or the like.

The rollers are driven at uniform speed to give a uni- 4 form linear rate of feed to the thread but it will be seen that the middle set B is driven in the opposite direction to that of the sets A and C.

The apparatus initially loaded with thread is then enclosed in a furnace and the treatment is carried out while thread is continuously fed through the apparatus.

I claim:

1. A method of maintaining under longitudinal tension a thread of carbonizable filamentary material while said thread is exposed to pyrolysis treatment in the production therefrom of carbonaceous filamentary material, said method comprising continuously delivering the thread lengthwise and winding the thread in spaced convolutions around only the outside of a cage formed by at least three rollers journaled in end bearings angularly spaced around coaxial pitch circles so that their rotational axes are oblique, successively in the same direction, to the longitudinal axis of the cage and positively rotating at least one of the rollers so that the rollers all in turn in the same direction to draw the thread around the cage in a substantially helical path, the thread convolutions each extending in contact with only a minor arc of the surface of each roller transversely to the rotational axis thereof and substantially tangentially from roller to roller successively around the outside of the cage.

2. A method according to claim 1, in which, prior to commencement of delivery of the thread to the cage of rollers, the ends of the rollers at one end of the cage are simultaneously turned about the longitudinal axis of the cage to an angularly adjusted position and set in said position to hold said rollers oblique to the longitudinal axis of the cage.

3. A method accordingly to claim 2, in which all the rollers of the cage are positively rotated at a uniform and constant peripheral speed.

Derwent Belgian Patent Reports No. 53/67 Jan. 31, 1968; 2A, pp. 2-3. Abstract of Belgian Pat. No. 700,655, Carpenter et al.

EDWARD J. MEROS, Primary Examiner G. ALVARO, Assistant Examiner US. Cl. X.R.

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