GB2163450A

GB2163450A - Reducing the moisture content of leather

Info

Publication number: GB2163450A
Application number: GB08519615A
Authority: GB
Inventors: Hanacek Josef; Miculka Zdenek
Original assignee: ZVS STROJOSVIT KONCERNOVY
Current assignee: ZVS STROJOSVIT KONCERNOVY
Priority date: 1984-08-22
Filing date: 1985-08-05
Publication date: 1986-02-26
Also published as: FR2569423A1; GB8519615D0; IT8521950A0; DE3528010A1; NL8502221A; FR2569423B3; IT1184829B; GB2163450B; CS247782B1

Abstract

Endless rope loops continuously wave (corrugate) the treated leather (u) from its middle to both sides. At the same time the endless rope loops are heated during their passage through a drying chamber and they transfer the heat at the processing contacting lines to the waved (corrugated) leather, which is also heated by heated air on the whole continuously varying remaining surface. The bottom branches of the endless rope loops of the upper conveyor and the upper branches of the endless rope loops of the bottom conveyor are symmetrically deviated from the longitudinal axis of the transporting area and they are arranged in the drying chamber. In the drying chamber are arranged heated-air nozzles (3a, 3b) the outlets of which are directed on to the treated leather. The endless rope loops consist of supporting elastic rope (46) which is coated by a resilient sleeve (47). The supporting elastic rope is provided with spaced knots. <IMAGE>

Description

SPECIFICATION Method of treating leather and apparatus for carrying out the method This invention relates to a method of treating leather in the phase between the wet and dry stages of its treatment in the course of its continuous feeding by mutually adjacent branches of the endless rope loops of the conveyor. This invention relates furthermore to an apparatus for carrying out the method which comprises two conveyors which are arranged one above the other and their transporting area is created by the endless rope loops, where the bottom branches of the upper rope conveyor endless rope loops are guided between the upper branches of the bottom rope conveyor endless rope loops.

During the treatment of leather in the phase between the wet and dry stages, that means between the working operations of the so-called wet pretreatment after tanning and finishing working operations, it is needed above all to reduce the moisture content in the leather. To say, after tanning the leather contents to 80% of the moisture in relation to its mass (weight) and before starting the finishing operations it is needed to reduce this moisture content to about 10-12%. When reducing this moisture content it is very desirable to prevent the loss of leather area as much as possible and at the same time to obtain the needed leather softness and suppleness. It is obvious, that these requests are contrary because the collagenous fibres of the leather structure are going to shrink and become harder when their moisture content is reduced.

Known is a method of treating leather in the phase between the wet and dry stages in which the treated leather is guided between two rubber conveyor belts which alternately pass with the leather through sections of mechanical treatment by vibrational tools and sections of heat treatment.

By this treatment the moisture content is being reduced by both mechanical and heat effect. A disadvantage of this method is that at a certain moisture content of the leather the vibrational tools leave impressions on the leather surface which effect appearance of the leather grain surface even after the dressing process has been finished. Another disadvantage of the said treating method is that between the individual cycles of the mechanical treatment by the vibrational tools the treated leather is influenced by a quite monotonous, uninterrupted heat. At the same time the leather is clamped between rubber conveyor belts, and the said heat which usually penetrates into the leather by heated-air convection, causes shrinking and drying contraction of the casual conglomerates of collagenous fibres. This produces hard even metal plate like areas in the leather structure.These concentrations of very hard collagenous fibres remain even after subsequent operating of the vibrational tools and final quality of the leather is thus deteriorated. A disadvantage of the said treating method is also in that the rubber conveyor belts carry the leather during the whole treating process in such a spread stage of its surface in which it had entered between the adjacent branches of the conveyors at the beginning of the treated process. Thus, if the leather enters between the adjacent branches of the conveyers with various folds and laps namely at its marginal areas, these folds and laps are more stabilized during subsequent heat and vibrationaltool operations.

Also known is an apparatus for the treatment of leather which consists of two conveyors which are arranged one above the other and their transporting area is created by endless rope loops guided in parallel, where the bottom branches of the endless rope loops of the upper conveyor are guided between the upper branches of the endless rope loops of the bottom conveyor. A disadvantage of this apparatus is that it is suitable only for leather transportation and cannot be used also for the treatment of leather, e.g. drying and softening, directly during transportation.

The aforementioned disadvantages are removed by a method of treating leather according to the present invention which is characterised in that the treated leather is in its whole surface waved (corrugated) in both directions from longitudinal shifting axis to sides by the action of endless rope loops which are heated while shifted and such a reached heat they transfer at proceeding contacting lines to the waved (corrugated) leather which is moreover at the same time heated by heated air at the whole continuously varying remaining surface.

An apparatus according to the present invention is characterised in that the bottom branches of the endless rope loops of the upper conveyor and the upper branches of the endless rope loops of the bottom conveyor are symmetrically deviated from the longitudinal axis of the transporting area and they are arranged in a drying chamber which is adapted for the flow of heated air. In the drying chamber, above the bottom branches of the endless rope loops of the upper conveyor, there is arranged an upper heating set of heated-air nozzles, the outlets of which are directed on to the transporting area. In the drying chamber, under the upper branches of the endless rope loops of the bottom conveyor there is arranged a bottom heating set of heated-air nozzles, the outlets of which are directed on to the transporting area.The endless rope loops of the conveyors consist of a supporting elastic rope which is coated by a resilient sleeve. The supporting elastic rope is provided with knots. The resilient sleeve is divided by gaps in spacings of the knots of the supporting elastic rope.

The higher technical effect of the method according to the present invention lies in that the mechanical and heat actuation of the conveyor endless rope loops operate together and at the same time with heat actuation of the flowing heated air. Thereby creation of shrinked and hard areas in the fibrous structure of the leather is prevented.

The higher technical effect of the apparatus according to the present invention lies in that during drying operation the conveyor endless rope loops stretch the leather from the middle to both sides by its continuous waving (corrugating) at the same time with drying. Thus losses of leather area are prevented and casual folds are smoothed. By the said waving (corrugating) the treated leather is also very effectively softened in the whole thickness of its fibrous structure. Heated air flowing out from the nozzles of the heat sets, acts on the treated leather both directly by convection and indirectly by conduction through the resilient sleeves of the conveyor endless rope loops. In combination of the supporting elastic rope and the resilient sleeve, the endless rope loops reach needed treating effect while keeping sufficient durability.The knots on the supporting elastic rope and the gaps between individual parts of the resilient sleeve prevent undesirable raking of the resilient sleeve.

Moreover when the resilient sleeve is divided by the gaps, assembling of the conveyor endless rope loops has substantially simplified.

An example of performing the method according to the present invention.

The wet leathers are individually inserted between extended ends of the mutually adjacent branches of the conveyor endless rope loops, by which they are driven further into the drying chamber. The conveyor endless rope loops continuously wave (corrugate) the treated leather in its whole surface in both directions from its longitudinal axis to the sides. When passing through the drying chamber the endless rope loops of the conveyors are heated as a consequence of flowing heated air and they transfer the heat by conduction to the waved (corrugated) leather at the proceeding contact lines. Moreover, the treated leather is heated at the same time at the whole continuously varying remaining surface by convection of flowing heated air.Thus the treated leather during waving (corrugating) is subjected to mechanical kneading which is performed at the same time with heat conduction in the direction from conveyor endless rope loops into the fibrous structure of the leather. Thus at the same time moisture is drained from the treated leather both directly as a consequence of the mechanical effect and indirectly by evaporation as a consequence of the heat effect. Moreover the heat effect is increased by heat convection as a consequence of the flowing heated air which also acts at the same time. In combination of conveyor endless rope loops mechanical treating, their heat conduction and heat convection of flowing heated air, drying effect is substantially increased and at the same time softening effect is obtained.By waving (corrugating) the treated leather from the middle to both sides losses of leather surface are prevented and folds are smoothed, that is the folds with which the leather was inserted between the adjacent branches of the conveyors at the beginning of the treating process.

The embodiment of an apparatus according to the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a general view; Figure 2 is a view in the direction of the arrow "P" in Figure 1; Figure 3 is a partial section along the line A-A in Figure 1 in a larger scale; and Figure 4 is a partial section along the line B-B in Figure 3.

In a frame 1 (Figure 1) is arranged a drying chamber 2 with an upper heating set a of heatedair nozzles 3a and a bottom heating set b of heated-air nozzles 3b.

In the frame 1 is further mounted an upper conveyor 4a under which is mounted a bottom conveyor 4b. Behind the conveyors 4a, 4b is arranged an outlet conveyor 5. In the frame 1 is further mounted, an electric motor 6 with a transmission 61 for driving both conveyors 4a, 4b and the outlet conveyor 5. The conveyors 4a, 4b comprise driving rollers 41a, 41b and stretching rollers 42a, 42b which are together wrapped around by endless rope loops 43a, 43b. The endless rope loops 43a of the upper conveyor 4a are guided by their bottom branches in grooves 45a (Figure 3) of guiding rollers 44a. The endless rope loops 43b of the bottom conveyor 4b are guided by their upper branches in grooves 45b of guiding rollers 44b, the grooves 45b being situated uniformly between the grooves 45a of the guiding rollers 44a of the upper conveyor 4a.The bottom branches of the endless rope loops 43a and the upper branches of the endless rope loops 43b are arranged adjacent to each other and thus create a transporting area p (Figure 2) with a longitudinal axis o in the direction s of feeding of the treated leather u. The bottom branches of the endless rope loops 43a of the upper conveyor 4a and the upper branches of the endless rope loops 43b of the bottom conveyor 4b are symmetrically deviated from the longitudinal axis o in the direction s of feeding of the treated leather u in such a way that within a length d of the transporting area p the deviation has a value h. The upper conveyor 4a is adjustable in height for adjusting mutual overlap m of the bottom branches of the endless rope loops 43a and of the upper branches of the endless rope loops 43b.

The conveyors 4a, 4b are arranged in the drying chamber 2 in such a way that their mutually adjacent branches, i.e. the bottom branches of the endless rope loops 43a and the upper branches of the endless rope 43b, are guided between the upper heating set a of the heated-air nozzles 3a and the heating set b of the heated-air nozzles 3b. The heated-air nozzles 3a of the upper heating set a are directed by their outlets from above on to the transportirig area p. The heated-air nozzles 3b of the bottom heating set b are directed by their outlets from below on to the transporting area p. The heated-air nozzles 3a, 3b are distributed through the whole transporting area p. The heating sets a, b of the heated-air nozzles 3a, 3b are provided with individual supplies 31a, 31b which are connected to a heated-air source (not shown). The whole space of the drying chamber 2 is connected to an air exhauster (not shown). If desired heated air of different physical properties may be applied to the individual heating sets a, b of the heated air noz zles 3a, 3b.

The endless rope loops 43a, 43b of the conveyors 4a, 4b are formed by a supporting elastic rope 46 which is covered by a resilient sleeve 47. The supporting elastic rope 46 is made of synthetic or natural fibres. The resilient sleeve 47 is made of a plastics hose with required elasticity and heat conductivity which does not leave undesirable feed marks when in contact with the surface of the treated leather u. The supporting elastic rope 46 is provided with knots z (Figure 4). The resilient sleeve 47 is divided by gaps r in spacings t of the knots z of the supporting elastic rope 46.

The apparatus according to the present invention operates as follows. The leathers to be treated are laid on to the inlet part of the bottom conveyor 4b, which part is situated outside the drying chamber 2. The treated leather u is thus transported to be clamped between the upper branches of the endless rope loops 43b of the bottom conveyor 4b and the bottom branches of the endless rope loops 43a of the upper conveyor 4a. In this clamped stage the treated leather u passes through the whole transporting area p. Because the bottom branches of the endless rope loops 43a and the upper branches of the endless rope loops 43b are symmetrically deviated from the longitudinal axis o of the transporting area p, the clamped treated leather u is continuously waved (corrugated) from its middle to both sides, this being done simultaneously with its passing through the drying chamber 2.The degree of this waving (corrugating) and thus also of the mechanical treatment effect of the treated leather u depends on the value h of deviation and on the mutual overlap m of the bottom branches of the endless rope loops 43a and of the upper branches of the endless rope loops 43b. If desired, the value h of deviation can be varied even during the treatment, e.g. by adjusting the guiding rollers 44a, 44b. For this purpose the guiding rollers 44a, 44b can be transversely divided in the line of the longitudinal axis o of the transporting area p and axially adjustable by an adjusting screw (not shown). Mutual overlap m can be adjusted by height setting of the whole upper conveyor 4a.

When passing through the drying chamber 2 the supporting resilient ropes 46 and resilient sleeves 47, are heated by flowing heated air and they transfer the heat by conduction to the waved (corrugated) treated leather u at proceeding contact lines. Moreover at the same time the treated leather u is heated at the whole continuously varying remaining surface by convection of heated air flowing from the nozzle 3a, 3b of the heating sets a, b. Thus the treated leather u is continuously kneaded through the whole thickness of its fibrous structure and at the same time is subjected to heat effects both by conduction from the supporting elastic ropes 46 resilient sleeves 47 and by convection from the flowing heated air. The values of heat received by conduction and heat received by convection are usually different.It is possible to deliver heated air of different temperature and moisture content through each individual supply 31a, 31b. Thus it is possible to treat e.g. the flesh side of the treated leather u by heated air of higher temperature and lower moisture content and the grain side by heated air of lower temperature and higher moisture content. The drying effect is thus conveniently increased by these different values of heat and moisture content in combination with the mechanical effect of the endless rope loops 43a, 43b. By continuous and alternative kneading and releasing the individual collagenous fibres of the treated leather structure there is conveniently reduced their concentration so that after completed treatment leather is softer and more supple.When the treated leather u is waved (corrugated) it is also at the same continuously spread from the middle to both sides and thus being lowering losses of leather surface area and possible folds are removed, the folds being those with which the leather might have been inserted between the adjacent branches of the conveyor 4a, 4b at the beginning of the treating process. When the treated leather u is continuously spread, it is at the same time guided from both surface side between adjacent branches of the conveyors 4a, 4b whereby space warping (distorting) of the treating leather is prevented. Thus the leather remains in the desired flattened form.

According to the needs of the technological process of leather treatment it is possible to arrange several machines according to the present invention into a common treatment line, either immediately next to each other or in combination with other inserted treating machines. For example, into a treatment line where the moisture content of the treated leather has already been properly lowered it is possible to insert a softening machine which acts on to the leather by vibrational tools only. For the transport of leather, treated in such a manner, between individual machines serves the outlet conveyors 5.

The present invention can be used for treating leather in the phase betwen the wet and dry stages of its treatment, especially for drying and softening them at the same time.

Claims

1. A method of treating leather in the phase between its wet and dry stages in the course of its continuous shifting by mutually adjacent branches of endless loops or rope conveyor means wherein the treated leather is in its whole surface waved (corrugated) in both directions from its longitudinal feeding axis to the sides by the action of the endless rope loops which are heated while shifted and transfer their heat at proceeding contacting lines to the waved (corrugated) leather which is moreover at the same time heated by heated air on the whole continuously varying remaining surface.

2. An apparatus for carrying out the method according to Claim 1, comprising two conveyors arranged one above the other, the transporting area of which is formed by endless rope loops, the bottom branches of the upper conveyor being guided between the upper branches of the bottom con veyor, wherein the bottom branches of the endless rope loops of the upper conveyor and the upper branches of the endless rope loops of the bottom conveyor are symmetrically deviated from the longitudinal axis of the transporting area and are arranged in a drying chamber which is adapted for the flow of heated air.

3. An apparatus according to Claim 2, wherein in the drying chamber, above the bottom branches of the endless rope loops of the upper conveyor, there is arranged an upper heating set of heatedair nozzles, the outlets of which are directed on to the transporting area.

4. An apparatus according to Claim 2 or 3, wherein in the drying chamber, under the upper branches of the endless rope loops of the bottom conveyor, there is arranged a bottom heating set of heated-air nozzles, the outlets of which are directed on to the transporting area.

5. An apparatus according to any one of Claims 2 to 4, wherein each of the endless rope loops of the conveyors consists of a supporting elastic rope which is covered by a resilient sleeve.

6. An apparatus according to Claim 5 wherein the supporting elastic rope is provided with knots.

7. An apparatus according to Claim 6, wherein the resilient sleeve is divided by gaps in spacings of the knots of the supporting elastic rope.

8. A method according to Claim 1 substantially as herein described with reference to the accompanying drawings.

9. An apparatus according to Claim 2 constructed, arranged and adapted to operate substantially as herein described with reference to, and as shown in, the accompanying drawings.

10. Leather treated in an apparatus according to any one of Claims 2 to 7 or 9.