Leather Drying

Abstract

Wet or moisture-saturated leather is placed on a surface of a heated drying cylinder with its grain arranged in a stretched and smooth condition and its longitudinal axis as defined by the rear edge of the leather piece parallel with the axis of the drying cylinder and with its fresh side out. In this condition the leather piece is then passed between the roller surface and a flexible conveyor band stretched as sling about a portion of the outer periphery of the drying roller, completely across its longitudinal length, until it is dried.

Description

BACKGROUND OF INVENTION

The present invention relates to a method and apparatus for drying flat skin material such as leather and in particular to the drying of leather on heated cylindrical rollers.

As is well known, during the tanning of leather, the leather piece becomes saturated with water or caustic solution which must be then mechanically removed before the piece can be further processed. Even after the mechanical removal of the water from the piece the leather contains a high degree of moisture and must then be dried. Up until now, this residual moisture has been removed either by naturally allowing the leather to be air dried in the open atmosphere or dried on a suitable heated drying surface.

The conventional methods have a number of drawbacks. Considerable space and time is required for the natural atmospheric drying since the leather must be manually placed or hung on poles or hooks and allowed to dry under ambient climatic conditions. In this system, the leather, furthermore, becomes folded, creased or curled and its ends and edges become broken and frayed.

To overcome this latter drawback, it was attempted to dry the leather piece by adhering it to a flat surface which admittedly would maintain the leather in flat condition. However, in order to adhere the leather, an adhesive or glue material had to be used, which resulted in causing the grain surface of the leather piece to stick to the flat surface and the glue would fill the grain of the leather so that the leather piece would then have to be washed or scraped of all adhesive after the drying process. In another technique, the leather was dried under vacuum conditions which, while being faster than the atmospheric technique, was much more costly and required extensive operating machinery and personnel.

It has been found to be preferable to dry moist leather pieces on a heated surface such as between a pair of conveyor bands and/or over a drying roller. In this manner, the leather piece may be satisfactorily flattened across its entire surface, glue or other adhesive material may be eliminated, and the leather quickly dried without folds, creases and/or broken ends.

It is accordingly the object of the present invention to provide an improved method and apparatus for drying leather which avoids the noted drawbacks of the prior art and in particular which provides a method for removing residual moisture from previously saturated leather by heating the same on a flat drying surface.

SUMMARY OF INVENTION

According to the present invention, the wet or moisture-saturated leather is placed on a surface of a heated drying cylinder with its grain arranged in a stretched and smooth condition and its longitudinal axis as defined by the rear edge of the leather piece parallel with the axis of the drying cylinder and with its fresh side out. In this condition, the leather piece is then passed between the roller surface and a flexible conveyor band stretched as sling about a portion of the outer periphery of the drying roller, completely across its longitudinal length, until it is dried. In the preferred form, the drying cylinder is provided with a surface having a circumference sufficiently large so that it is a multiple of the width of the leather piece to be treated and forms with the leather sling band a cooperating length at least as great as the width of the leather piece to be treated. The drying cylinder is also intermittently driven between an infeed station, at least one drying station, and a discharge station, so that the drying of successive pieces of leather may be effected in a more or less continuous manner.

In accordance with the present invention, the apparatus is provided for adjusting the length of the band slung about the periphery of the drying cylinder, as well as external air blowing means for drying the surface of the cylinder after the leather piece has been discharged.

BRIEF DESCRIPTION OF THE DRAWINGS

The method of the present invention and apparatus for carrying out is schematically shown in the single FIGURE of the drawing which accompanies this description.

DESCRIPTION OF INVENTION

As seen in the drawings, the suggested apparatus comprises a drying cylinder 1 having a relatively large diameter and an elongated length. The surface of the cylinder 1 is smooth and polished and is preferably made of rust-free material or is coated with a layer of chromium enamel or other material of a similar nature. The cylinder 1 is mounted on an axle 2 and is connected to a source of heat by which the interior may be heated to provide a warm drying surface. The cylinder 1 is also connected by suitable drive means such as a gear and clutch mechanism to a drive motor such as an electric motor, none of which is shown because of their conventional and well-known nature. By the use of such well-known and conventional mechanism, the cylinder 1 may be driven in stepwise or intermittent fashion in the direction of the arrow A. Suitable control means, also not shown, are provided whereby an operator may manually or automatically control the rotation and the operation of the cylinder.

The cylinder is also mounted on a suitable frame, and supported, etc., so as to maintain the various parts in operative arrangement. Additionally, the mechanism is situated so that an operator has access to the upper left hand quadrant of the cylinder which by its nature provides a free and readily accessible feeding station by which a moist leather piece 3 can be manually or mechanically placed in stretched and flattened condition upon the surface of the cylinder 1. The drying cylinder is made to have a length longer than the leather piece to be treated and a circumference at least twice as long as the width of the piece to be treated.

Located beneath the drying cylinder is a flexible porous holding band 4 having a width at least equal to the axial length of the cylinder 1. The holding band 4 is entrained over a pair of spaced rollers 5 and 6, which are spaced a distance apart greater than the width of the leather piece 3 to be treated. Both the roller 5 and 6 are spaced from the surface of the cylinder 1. The roller 5 serves as the intake mouth or infeed zone and is located adjacent the upper left quadrant or intake station previously described. The roller 6 serves as the outlet mouth or discharge zone for the leather piece after it has been dried.

The rollers 5 and 6 are both mounted by conventional means so as to be rotatable about their axes and at the same time positionable in an arc about the periphery of the drying cylinder 1. The rollers 5 and 6 are spaced from the surface of the drying cylinder, that is they do not touch it as is seen in the FIGURE, so as to normally provide a funnellike entrance or exit for the leather as it is carried by the cylinder 1 between it and the flexible band 4. The rollers 5 and 6 are also spaced apart from each other, an amount at least equal to the width of the leather piece 3 to be treated. Preferably, the rollers 5 and 6 are also positively driven by conventional drive means to move the band 4 at a rate equal with the movement of the drying cylinder 1. Such conventional means may include cooperating gearing and clutch mechanisms so that the cylinder 1 and the rollers 5 and 6 may be jointly and intermittently rotated.

The holding band 4 is pressed against the surface of the drying cylinder 1 by a second pair of rollers 7, each rotatable about an axle 8, connected radially to the axle 2 of the drying cylinder 1 by an adjustable coupling 9. This adjustable coupling, preferably automatically, maintains the rollers 7 in pressure contact against the band 4 which is thus also maintained in pressure contact against the surface of the drying cylinder 1. The rollers 7 are also adjustable in an arc about the periphery of the drying cylinder 1 so that the drying zone between the two rollers can be maintained at least equal to the width of the leather work piece 3. The adjustable couplings may be hydraulically or spring actuated and may comprise a conventional piston and cylinder arrangement. Again the specific details of this coupling 9 are omitted for the sake of brevity and conciseness of the present disclosure.

The endless holding band 4 is further trained over idler driven rollers 10 and 11 which are adjustably mounted by their axes so as to be movable in the frame of the apparatus with respect to the drying cylinder 1. The endless band 4 trained over the rollers 10 and 11 provide an extension on which the leather workpiece 3 may be carried after it is dried in the drying zone. In such an instance, the extension provides a discharge station.

Insofar as the circumference of the drying cylinder 1 is greater than three times that of the leather workpiece, the intermittent rotation of the cylinder will generally permit the leather workpiece to remain in the drying zone a sufficiently long enough time for it to be dried when it reaches the discharge station i.e., the discharge mouth defined by the roller 6 and the surface of the drying cylinder 1. The leather may be then carried by the extension of the holding band 4 which turns horizontally away from the surface of the cylinder to the right as shown in the solid lines. It will be appreciated that in this instance the full periphery of the cylinder is not necessarily required to provide the drying of the leather. To prevent heat loss from the unused portion, etc., a cover member 12 is located in the upper right quadrant of the cylinder. The cover member 12 restricts the heat from being dissipated into the atmosphere.

Should the leather be of such a large size or the cylinder 1 be of such a small diameter that the circumference is less than three times, perhaps slightly more than twice, that of the width of the leather workpiece, then an additional time may be required for drying the leather. In this situation, the cover 12 may be removed and the holding band 4 positioned so that it encompasses more of the periphery of cylinder 1. This may be accomplished by readjusting the position of the discharge roller 6 as well as those of the rollers 10 and 11 to a position as shown, for example, in the dotted lines of the figure. The discharge station can therefore be moved to a position further along the circumference of the drying cylinder and the leather workpiece will then be discharged after undergoing a more prolonged drying period in a longer drying zone. Under extreme conditions, the belt 4 may be entrained almost about the entire periphery of the drying cylinder as shown actually in the dotted lines of the figure so that the leather workpiece may be discharged at the position shown by the arrow C.

It will be understood that the discharge mouth defined by the rollers 6 or 6' can be placed anywhere between its extreme position as indicated in the figure so that the drying zone can be varied as required. Furthermore, by varying the intermittent motion of the drying cylinder and its rotation, the drying time can be elongated as desired. It is preferred, however, that the drying zone be of a length comprising some multiple of the width of the leather workpiece 3 to be treated as for example, twice, three times or even four times such a width so that by intermittently rotating the cylinder, successive pieces of moist leather workpieces may be applied at the intake station and simultaneously removed from the discharge station when completely dried. Under certain conditions, it may also be desired to maintain the workpiece on the surface of the cylinder 1 for a second circuit through the drying zone. This may occur when the workpiece is of sufficient size and the drying cylinder of small circumference so that a second drying period is required to remove satisfactorily the required degree of moisture. There will thus be observed the apparatus herein described is extremely flexible in its operation as well as being very simple and economical to construct.

The method of drying leather in accordance with the present invention can be accomplished in a continuous manner in which the leather workpieces may be put through the drying operation and removed successively therefrom. Operatively the machine operator lays the leather with its grain side on the open and available portion of the intake station and by hand or with the aid of a tool such as a pole, the operator smooths and straightens the flesh side or outside surface of the leather workpiece to remove any folds, creases and/or bumps that can be found thereon. The leather is laid so that its longitudinal axis, as defined by the rear edge portion, is parallel to the longitudinal axis of the drying cylinder 1. On placement of the leather on the surface of the drying cylinder, the operator causes the cylinder to be indexed by operating the control means described previously. In this manner, the leather 3 enters through the intake mouth defined by the roller 5 and the cylinder surface, between the holding band 4 and the surface of the drying cylinder 1 until the entire piece of leather is held securely between the holding band and the cylinder 1. At this instance, the cylinder is caused to stop at a second or succeeding leather workpiece 3 is placed on the cylinder surface at the intake station. The machine operator smooths and straightens the second piece of material while the first piece of leather remains in the drying zone defined by the pressure rollers 7 which cause the holding band 4 to press against the surface of the cylinder 1. At the proper time, the operator then indexes the cylinder again moving the succeeding workpiece into the drying zone while simultaneously moving the first workpiece to the extended portion of the endless band 4, for exiting out of the apparatus at the discharge mouth defined by the roller 6 or for passage further along the surface of the cylinder 1 until it reaches the extended discharge portion defined by the roller 6'.

Insofar as the circumference of the cylinder 1 is slightly larger than twice the width of the leather, then the operator prepares the leather at the intake station of the cylinder while the preceding piece of leather is being simultaneously dried between the cylinder 1 and the holding band 4. A single index of the rotating cylinder should be sufficient to dry the leather and the leather may then be taken off directly at the discharge station shown in the full lines of the schematic figure. The operator may then directly remove, by hand, the workpiece and place it aside for later operation on some other machine. It will be appreciated, however, that when it is necessary for the workpiece to be indexed through two, or three or even four times its interval of width so that it must remain in drying zone an extended period of time, then the holding band is positioned by repositioning the rollers 6, 10 and 11 as desired to accommodate this necessity. As noted, the present invention provides, advantageously, simple and effective means to accomplish without any detrimental effect either to the quality and condition of the leather workpiece.

The technical effect of the present invention rests in the fact that the drying of the leather on the cylinder 1 is accomplished by simultaneously heating its entire surface along its grain side by which it is essentially held against the surface of the drying cylinder 1. However, it is held without glue or other adhesive material and solely by the action of the sling holding band 4 so that it does not require the final washing or scraping after the leather workpiece has been dried. The resultant dried leather workpiece has a smooth clean grain and a smooth clean surface wherein folds, spots or other unwanted defects are virtually eliminated. A further advantage is obtained in the manner by which the leather is brought under the influence of the drying zone. By providing a drying cylinder of relatively large diameter and by placing the leather so that its longitudinal axis is parallel to the axis of the cylinder, the leather is placed on a relatively flat surface compared to its width and closer to the normally natural way in which the animal body would, for example, lie. In this manner, the workpiece can be stretched and placed on the cylinder in an extremely convenient and efficient manner and it can then be removed without causing the leather workpiece to coil or fold.

It will be apparent from the foregoing that the present invention provides an improved method and apparatus for the drying of the leather workpieces overcoming virtually all of the drawbacks of the prior art. Various modifications may be made in the present invention both in its method and apparatus forms, in that the degree of rotation, the timing of the indexing of the cylinder, the degree of pressure on the rollers and the holding band 4, and other varying features may be adjusted. Accordingly, it is intended that the present invention be illustrative only and not limited in any manner.

Claims

What is claimed:

1. A method for drying flat piece materials such as leather comprising the steps of placing the leather on a heated cylindrical surface with its grain so stretched that the longitudinal axis of the rear edge portion is parallel with the longitudinal axis of the cylinder, and wherein the flesh side of said leather piece is out, stretching and smoothing the leather workpiece, passing the same between a flexible band and the surface of said cylinder and indexing said cylinder at predetermined intervals thereby maintaining the leather workpiece between it and the holding band for a predetermined time interval until said leather is dried.

2. The method according to claim 1, wherein the belt is moved in a direction and at a speed corresponding to that of the drying cylinder so that the leather workpiece remains between the cylinder and the holding band in relatively fixed condition.

3. Apparatus for the drying of leather piece material comprising a rotating heated drying cylinder, said cylinder having a longitudinal axis greater than said leather piece and a circumference greater than twice the width of said leather piece to define at least infeed, drying and discharge stations, an endless flexible belt arranged about the periphery of a portion of the said cylinder at said dwell station, said belt being trained over an intake roller and a discharge roller spaced apart a distance at least equal to the width of said leather piece, pressure rollers spaced between the intake and discharge rollers for pressing said band against the surface of said cylinder including means for resiliently coupling the axis of said drying cylinder and the axis of said pressure rollers to provide a predetermined pressure on the leather piece and means for indexing said cylinder to move said leather piece at intervals, to permit successive application of leather pieces at said infeed station maintenance between said band and said cylinder at said drying station until dried and removal at said discharge station.

4. The apparatus according to claim 3, wherein said endless band is provided with an extending portion extending beyond the discharge roller to provide a discharge station for said dried leather workpiece.

5. The apparatus according to claim 4, wherein said extending portion is adjustably mounted with respect to the periphery of said drying cylinder so that the effective length of the band with respect to the surface of the cylinder may be varied.

6. The apparatus according to claim 5, wherein the intake roller and discharge roller are spaced from the surface of the drying cylinder so as to provide a funnellike entrance and exit for the leather workpiece.