Running filamentary material is treated by continuously supporting it by engagement with a belt which travels around a series of rolls in a path which is a zig-zag in a vertical plane through a vessel containing a treating agent, and is driven so as to carry the material with it through the vessel. The term "treating agent" includes liquids, gases and sources of radiant heat. The belt may be of rubber and may be contoured to provide a longitudinal channel adapted to receive and contain the filamentary material. The latter may consist or an organic ester of cellulose and the treatment may consist in continuously saponifying, washing and drying the ester. As shown in Fig. 1, wet-spun cellulose acetate yarns 12 emerge over guide rolls 13 from a spinning assembly 11 and enter a treating section 14. <PICT:0755865/IV(a)/1> <PICT:0755865/IV(a)/2> <PICT:0755865/IV(a)/3> <PICT:0755865/IV(a)/4> <PICT:0755865/IV(a)/5> <PICT:0755865/IV(a)/6> <PICT:0755865/IV(a)/7> This section is a compartmented vessel comprising a series of driven parallel upper rolls 15 and a series of lower idler rolls 16. The rolls 15, 16 are all provided with closely spaced parallel circumferential grooves 17 (Figs. 4, 6 and 8). A set of endless flexible belts 18 having channels 19 in both of their faces are trained in parallel alternately over the upper rolls 15 and under the lower rolls 16 from the input end to the output end of the treating section 14 (Figs. 1 and 2), and are guided back from the output to the input end by idler rolls 20, 21, both grooved in the same manner as the rolls 15, 16. Between each upper roll 15 and the succeeding lower roll 16 a twist of 180 degrees is inserted in each belt 18, except that between the first of the upper rolls 15 and the first of the lower rols 16, and between the last of the lower rolls 16 and the last of the upper rolls 15, the belts are not twisted. Advantageously the twists between successive rolls are equal and in opposite directions. As shown in Figs. 4-6, the belts 18 are of a section contoured to fit closely into the grooves 17 in the rolls 15, 16 so that the grooves will hold them closely and evenly spaced and parallel with one another as they travel through the treating section 14. As the yarns 12 reach the treating section, they are led to the first of the upper rolls 15 and will lie one in each groove 17 of the roll, under the corresponding belt (Fig. 4). Each yarn 12 and belt 18 will move away together from the first upper roll, the yarn 12 lying in the channel 19 of the belt (Fig. 5) and being supported and carried along by the belt. The yarn is then carried under the first of the lower rolls 16 by the belt, which now lies between the yarn and the surface of the roll (Fig. 6). As the belt moves up from the first of the lower rolls 16 it is twisted through an angle of 180 degrees so that when it reaches the next upper roll 15 the yarn, which still lies in the channel 19 of the belt, is again held away from the roll by the belt. The belt will then carry the yarn through the remainder of the treating section 14 in the same way without allowing the yarn to make contact with any of the rolls 15, 16, except that after leaving the last lower roll 16 the belt is not twisted, so that the yarn lies in the groove 17 of the last upper roll 15 underneath the belt. The yarn then passes to a conventional winding apparatus 51. The saponifying medium is supplied through a conduit 26 and header 27 to the compartment 22 of the treating section 14 and overflows through a header 28 and a conduit 29. In this compartment the cellulose acetate yarn is converted into a regenerated cellulose yarn. In the second compartment 23 the yarn is washed by water which enters at spaced points through conduits 31, 32 and headers 33, 34, and leaves by overflowing through a header 35 and a conduit 36. Two baffles 37 extend upwardly from the floor of the compartment to a level below that of the overflow header 35, and two further baffles 38 extend downwards from a level above that of the header 35 (and thus above the surface of the wash water in the compartment) to a level a little above that of the lower rolls 16. The batfles 37, 38 cause the wash water to flow through the compartment in a sinuous path. In the third compartment 24, which is similarly provided with baffles and conduits, the yarn is further washed with water, and in the last compartment the yarn is dried by means of a steam-heated convection heater 46 and a number of vertical radiant heaters 49. To enable the apparatus to be threaded rapidly on starting up or in the event of a yarn breaking, each belt 18 is provided with a series of slits 52 inclined (from the face of the belt inwards) backwardly with respect to the direction in which the belt moves. The end of the yarn is inserted in one of the slits 52 (Fig. 7) and when, after being carried through the treating section 14, the end of the yarn reaches the last of the upper rolls 15, the yarn is removed from the slit and led to the winding apparatus 51. In a modification (Fig. 8) a flat belt 53 is substituted for the contoured belt 18. As this flat belt rides in the V-shaped grooves 17 of the rolls 15, 16, its cross-section also assumes a V-shaped form, so providing channels 54 for supporting the yarn 12. Specification 744,319 is referred to.ALSO:Running filamentary material is treated by continuously supporting it by engagement with a belt which travels around a series of rolls in a path which is a zigzag in a vertical plane through a vessel containing a treating agent, and is driven so as to carry the material with it through the vessel. The term "treating agent" includes liquids, gases and sources of radiant heat. The belt may be of rubber and may be contoured to provide a longitudinal channel adapted to receive and contain the filamentary material. The latter <PICT:0755865/IV(c)/1> <PICT:0755865/IV(c)/2> <PICT:0755865/IV(c)/3> <PICT:0755865/IV(c)/4> <PICT:0755865/IV(c)/5> <PICT:0755865/IV(c)/6> <PICT:0755865/IV(c)/7> may consist of an organic este of cellulose and the treatment may consist in continuously saponifying, washing and drying the ester. As shown in Fig. 1, wet spun cellulose acetate yarns 12 emerge over guide rolls 13 from a spinning assembly 11 and enter a treating section 14. This section is a compartmented vessel comprising a series of driven parallel upper rolls 15 and a series of lower idler rolls 16. The rolls 15, 16 are all provided with closely spaced parallel circumferential grooves 17 (Figs. 4, 6 and 8). A set of endless flexible belts 18 having channels 19 in both of their faces are trained in parallel alternately over the upper rolls 15 and under the lower rolls 16 from the input end to the output end of the treating section 14 (Figs. 1 and 2) and are guided back from the output to the input end by idler rolls 20, 21, both grooved in the same manner as the rolls 15, 16. Between each upper roll 15 and the succeeding lower roll 16 a twist of 180 degrees is inserted in each belt 18, except that between the first of the upper rolls 15 and the first of the lower rolls 16, and between the last of the lower rolls 16 and the last of the upper rolls 15, the belts are not twisted. Advantageously the twists between successive rolls are equal and in opposite directions. As shown in Figs. 4 to 6, the belts 18 are of a section contoured to fit closely into the grooves 17 in the rolls 15, 16 so that the grooves will hold them closely and evenly spaced and parallel with one another as they travel through the treating section 14. As the yarns 12 reach the treating section, they are led to the first of the upper rolls 15 and will lie one in each groove 17 of the roll, under the corresponding belt (Fig. 4). Each yarn 12 and belt 18 will move away together from the first upper roll, the yarn 12 lying in the channel 19 of the belt (Fig. 5) and being supported and carried along by the belt. The yarn is then carried under the first of the lower rolls 16 by the belt, which now lies between the yarn and the surface of the roll (Fig. 6). As the belt moves up from the first of the lower rolls 16 it is twisted through an angle of 180 degrees so that when it reaches the next upper roll 15 the yarn, which still lies in the channel 19 of the belt, is again held away from the roll by the belt. The belt will then carry the yarn through the remainder of the treating section 14 in the same way without allowing the yarn to make contact with any of the rolls 15, 16, except that after leaving the last lower roll 16 the belt is not twisted, so that the yarn lies in the groove 17 of the last upper roll 15 underneath the belt. The yarn then passes to a conventional winding apparatus 51. The saponifying medium is supplied through a conduit 26 and header 27 to the compartment 22 of the treating section 14 and overflows through a header 28 and a conduit 29. In this compartment the cellulouse acetate yarn is converted into a regenerated cellulose yarn. In the second compartment 23 the yarn is washed by water which enters at spaced points through conduits 31, 32 and headers 33, 34, and leaves by overflowing through a header 35 and a conduit 36. Two baffles 37 extend upwardly from the floor of the compartment to a level below that of the overflow header 35, and two further baffles 38 extend downwards from a level above that of the header 35 (and thus above the surface of the wash water in the compartment) to a level a little above that of the lower rolls 16. The baffles 37, 38 cause the wash water to flow through the compartment in a sinuous path. In the third compartment 24, which is similarly provided with baffles and conduits, the yarn is further washed with water, and in the last compartment the yarn is dried by means of a steam heated convection heater 46 and a number of vertical radiant heaters 49. To enable the apparatus to