PROCEDURE FOR REMOVING THE LAYER OF HAIRY ELEMENTS FROM A COMPLETE ANIMAL SKIN

Abstract: A method of hair removal from an animal pelt including freezing a skin of said pelt to a temperature where hair pores of the skin open and to removing hairs from said skin.

Description: This invention relates to a method of hair removal from an animal pelt including freezing a skin portion of said pelt to a temperature where pores open for releasing the hair from the skin, and removing hairs from the skin. Such a method, especially as indicated in the preamble of the main claim, is known from FR-A-552,899, wherein the pelt is frozen in a single action to approximately minus 180°C. Furthermore, GB-A-163,294 indicates a process for unhairing hides which consists in subjecting hides to the action of intense cold at a temperature below minus 100°C in order to render the hairs brittle, and whilst said hairs are still brittle, breaking off and removing them. The novel features of the present application with respect to this prior art have been indicated in the characterizing portion of the accompanying main claim and comprise therefore that the pelt is preliminary cooled to a temperature between zero and minus 20°C, whereafter the thus cooled pelt is frozen to a temperature of minus 220°C. The accompanying second claim relates to preferred form of the invention which will now be described with reference to the dewoolling of an animal pelt such as the pelt of a sheep. This procedure in accordance with the invention is characterised by the fact that the fresh animal pelt in its flexible state is positioned, flesh side down on a movable apertured support. The pelt is subjected to suction from within the support by the apertures which secures the pelt onto the support. At least one application of a liquified gas is carried out against the flesh side of the pelt through the aperture surface to effect a preliminary freezing of between naught (0) degrees Celsius and minus twenty (20) degrees Celsius of the skin of the pelt. Thereafter, the pelt is subjected to one or more sprayings with the same or another liquified gas so as to cool the skin from a temperature of about minus twenty (20) degrees to about minus two hundred and twenty (220) degrees Celsius and thereafter extraction of the wool is then carried out by conventional pulling means. The dewoolled skin is warmed until a temperature at which it can be handled is reached. Where the skin if the pelt is particularly thick the freezing process occurs relatively slowly with a proportionately high consumption of liquified gas. Given that the objective of the freezing process is for the freezing to occur at the root of the hair or wool as rapidly as possible, it is envisaged that the liquified gas may also be applied on the upper surface of the skin. A minimum of one further application of liquified gas to the upper side of the skin will accelerate freezing of the roots of the hair or wool thereby increasing efficiency of the extraction process. Any such acceleration in the freezing process will ensure greater overall uniformity and will serve to lessen the risk of undesirable contractions in the leather. The skin will be more stable and will conform more easily to the perforated conveyor belt with the possibility that the necessity for a suction securing system may be avoided. The application of the liquified gas to the upper surface of the pelt may be carried out contemporaneously with its administration to the lower surface or, alternatively, these processes may be carried out separately if desired. The liquified gases used for freezing the pelt may be as follows: Nitrogen, Carbon-dioxide, liquid air, freon and argon. It should be noted however that liquid nitrogen is preferred for this process. Figure 1 shows a side view of the processes involved in extracting wool or hair from complete animal pelts. Figure 2 shows the same processes depicted in Figure 1 viewed from above. Figure 3 is a schematic diagram showing the extraction equipment which consists of rotating cylinders. Figure 4 is similar to Figure 3 save that the extraction equipment is supplemented by a pneumatic suction device. Figure 5 is a similar view to that shown in Figure 3 save that the extraction equipment consists of both a rotating cylinder and a pneumatic suction device. The process which is the subject of this invention may be carried out using a frame (1) equipped with a perforated conveyor belt (2) or a drum which secure and transport the animal skins (3) which are placed fleshy side down on the conveyor belt and then pass through a preparation tunnel (5), a hair or wool removal area (6) and a recovery tunnel (7). The pneumatic equipment (8) and liquified gas (preferably nitrogen) (9) injection equipment are housed in the lower part of the frame (1). The conveyor belt (2) is driven by a cylinder (10) which is in turn driven by a motor (11), and runs over freely rotating rollers (12) and a tension cylinder (13). The tunnels (5) and (7) are equipped with isolation curtains (14) as shown in Figures 1 and 2. The extraction area (6) as shown in Figure 3 comprises a set of three revolving rollers (15, 16 and 17) which are mounted on a base rotating on an axle (18) and are equipped with the desired medium (comb, blade and brush). The active roller is equipped with a wool or hair expulsion device (19). The equipment also comprises a belt (20) which picks up the wool or hair and carries it to a further belt (21) which in turn carries the wool or hair to a pipe (22). A cold air intake pipe (23) is also fitted. As shown in Figure 3, an optional inlet (24) may be provided for recycled air which comes from the pneumatic equipment 8. The latter equipment consists of ventilator fan (25) and primary (26) and main (27) suction ventilators. The nitrogen spray equipment consists of a nitrogen tank (28) and associated piping feeding the primary (29) and main (30) nozzles by means of appropiate valves. In the modification shown in Figure 4 the belt (20) and hair or wool collection roller (19) are replaced by a system composed of a suction nozzle (31) connected to a cyclone separator (32) which forces air through a nozzle (33) and blows the wool or hair to a container below (34). In the modification shown in Figure 5, the belt (20) and hair or wool collection roller (19) are replaced by a system composed of a rotating roller (15) and a suction device (31) linked to a cyclone separator (32) which forces air through a nozzle (33) driving the hair or wool to a container beneath (34). Thus the hair or wool extraction process is carried out on the fleshy side of the pelt in the following manner: The skins (3) are placed on the conveyor belt (2) in the perforated area (5) as shown in Figure 2 and are secured to the perforated conveyor belt by the action of the suction ventilator (26) and in the extraction area by means of suction ventilator (27). Between the two suction phases there are also two nitrogen sprayings stages carried out by use of nozzles (29) and (30). Provision is made for either a single or multiple rows of nozzles which administer the liquid nitrogen at successively lower temperatures of about minus 20 degrees Celsius and minus 220 degrees Celsius. The effect of the nitrogen is to freeze the skins (3) in such way that the pores open and release the wool or hair (4). Consequently, the hair or wool may be removed by simple traction using, for example, one of the rollers (15, 16 and 17)-depending on the type or wool or hair. The extraction process is carried out in conjunction with an expulsion device (19) which causes the wool or hair to drop on the conveyor belt (20) whence it is transferred to the next conveyor belt (21) which transports the wool or hair along a pipeline (22) to a tank or final rinsing unit. As a terminal stage, the skins (3) travel through the recovery area (7) for warming to enable them to regain their original flexibility. The wool or hair does not need to undergo any such process. Nitrogen is the preferred gas for use in the freezing stage although it may be feasible to use freon, although this is not advisable due to its chlorine content. Argon may also be used although this has the disadvantage of high cost. Carbon-dioxide may also be used although it poses difficulties when temperatures of below minus 50 degree Celsius are required. Liquid air is not considered appropiate for this process due to the difficulty of obtaining a bulk supply. The speed of travel of the skins (3) along the conveyor belt (2) is preferably in the order of 1 to 20 metres per minute given that freezing of the pelts takes place almost instantaneously and it is also noted that the humidity of the pelts at the start of processing should range from 50 to 500 percent.

Claims: A method for removal of hair from a pelt, comprising freezing a pelt to a temperature below minus 180°C by means of liquified gas, characterized in that prior to said freezing, the pelt is cooled to a temperature between zero and minus 20°C, and in that after said cooling, said freezing takes place to a temperature of minus 220°C. A method for removal of hair from a pelt as set forth in claim 1, wherein the pelt is laid upon a perforated conveyor belt, after which the pelt is kept on the conveyor belt by suction through the perforations of the conveyor belt, subsequently subjecting at least the fleshy side of the pelt at least once to liquified gas through the perforations of the conveyor belt in order to produce said cooling to a temperature between zero and minus 20°C, and conveying the cooled pelt into an apparatus wherein said pelt is subjected to liquified gas on at least one side of the pelt in order to produce said freezing to a temperature minus 220°C, after which the hair is removed from the skin portion of the pelt. Hair produced by the method as set forth in claim 1 or 2.

Inventors: COTS TANA, ESTEBAN, COTS TANA, JUAN
Applicants: COTS TANA, ESTEBAN, COTS TANA, JUAN
Application year: 1986
Main classification: C14B1
IPC codes: C14B1, C14C1