Patent Publication Number: US-4148947-A

Title: Method for treating leathers

Description:
This is a continuation application of Ser. No. 9,574 filed Feb. ], 1970, now abandoned. 
    
    
     The object of this invention is to provide a method of moistening sheet material such as leather, carboard, etc., in order to make it supple, as well as to provide equipment for performing the method. 
     For processing, many types of sheet material and particularly leather is required to be supple, and therefore, it is necessary to treat it. This is done mostly by moistening the purpose of which is to achieve a hygroscopic balance in leather. The classic method of laying the leather in wet sawdust requires difficult and legnthy handling. A more simple conditioning of leather occurs after a short immersion of the leather in water or after the leather has passed through a spraying or padding machine in which it is heated, and thus becomes well and uniformly moistened. However, all these methods require a long treatment time and none of the presently known equipment can be included in a production line. 
     These drawbacks are eliminated by the method of the present invention wherein sheet material such as leather and the like is subjected simultaneously to hot moisture, and a cooling medium under pressure, alternatively from the grain side and from the flesh side in a continuous method. This is performed between two endless conveyor belts which are wetted by water, each of which is independently guided and saturated with water on the outer side and which are guided together on the inner side, i.e. they are guided alternatively from above and from below round a portion of the circumference of a plurality of rollers. Moistening, cooling and heating units are arranged on the outside of the rollers. 
    
    
     An example of the appropriate equipment or apparatus is diagrammatically illustrated in the drawing. 
    
    
     Each of the two endless conveyor belts, the upper 1 and the lower one 2, is guided independently round the guiding rollers 3 on the outer portion of the runway. On the inner portion of the runway both belts 1, 2 are guided together on the portion of the circumference of active rollers 4 which are freely rotable in bearings 5. There is a greater number of active rollers 4 arranged one after the other and both conveyor belts are guided together alternatively from above and from below the rollers 4. For moving both belts 1 and 2 a common driving roller 6 cooperates with drive means from a control driving unit (not shown). Where the drive is applied directly to the active rollers, the rollers 6 acts as a guiding roller. Each of the belts 1, 2 is tightened by an independent tightening roller 7. Endless conveyor belts 1, 2 are wetted by water and for their saturation each is provided on the outer portion of the runway by the immersing through 8 provided with the roller 9. Moreover, on the outer side of the rollers 4 where the belts are guided together and opposite to the rollers 4, there are provided moistening, cooling and heating units 10. A sheet material 11, such as leather, cardboard, etc., is put between the endless conveyor belts 1, 2 which on the input portion of the rollers 4 come together in wedge-shaped method in order to facilitate the placing or insertion of sheet material. On the output portion the lower conveyor belt 2 is enlarged in order to facilitate the piece being processed to be taken off. 
     The technological effect of the equipment or apparatus according to the invention is distinctly evident in the case of leather which, after being stripped from plates of the paste drier, is stiff, and therefore, must be subjected to further processing to make it supple. The leather is inserted between wet endless conveyor belts 1, 2 and being clamped between them is fed to the first roller 4 which is heated to a temperature controlled within the range from 40° to 140° C. On their outer sides, the belts 1, 2 are treated with the cooling units 10. Thus, a temperature gradient developes for a quick moisture penetration into the leather in the direction of heat flow. When the conveyor belts are being transferred onto the second active roller, the outer conveyor belt contacts the heated roller, so that the heat flow is now directed from the flesh side of the leather. For the moisture to be captured in leather, two other active rollers are used which are cooled together with the units arranged on the outer side of the belts. The number of active rollers and their temperature depends on the type of the material being processed. 
     Equipment arranged according to the invention permits the active rollers to be heated or cooled and the respective units to serve for cooling or heating. Moreover, they can be also used for additional moistening. 
     The described method enables suppling sheet material in the shortest possible time in what is the necessary condition for its further processing; The equipment according to the invention is the most effective means for achieving the foregoing postulates and serves as an effective part of a continuous flow system, especially in the existing production line in tanneries prior to further processing in the through-feed staking machine.