A machine for rolling leather into roll form

Abstract: Apparatus for mechanically rolling leather onto a support sleeve, comprising a stand (1), rolls journalled in the stand, an endless web (4) which extends over the stand rolls, and web drive-rolls (5, 7). The web (4) is intended to be moved in between two further rolls (12, 25) located at different heights, by means of the rollers (10) acting on opposite edges of the web, such as to form a pocket or hollow. Placed in the pocket is a sleeve around which the leather is intended to be wound by the web a desired number of turns in a fold-free and smooth fashion. The upper pocket-forming roll (12) is raised when rolling of the leather onto the cylinder is completed, and the finished leather roll is removed from the pocket, so as to enable the roll to be lifted by gripping devices (17) forming part of a traversing lifting device (16) movable across the web. The speed at which the machine drive devices operate is controlled, and the various part operations can be controlled individually and sequentially with respect to time. For the purpose of advancing the web through the machine in dependence on variations in leather thicknesses, the rolls and web may be driven at mutually different speeds.

Description: The present invention relates to a machine by means of which leather can be rolled-up onto a support cylinder with the aid of a drive motor. In the leather industry, animal hides are prepared for tanning to form leather, in certain instances referred to as skins. The leather is then transported to refining industries, for instance furniture industries or baggage-making industries. Leather pieces that are prepared from hides normally have an area of 0.5-6 m 2 and a thickness of 0.3-1.6 mm. These leather pieces must be delivered to the users in a completely smooth state and no pleats or folds whatsoever are allowed. It has long been found that the most reliable manner of transporting such leather pieces is to roll the leathers onto support cylinders. These cylinders are preferably made of paper-board and are at least 1 dm in diameter. A cylinder length of 1.5 m will suffice, even when the width of the leather is more than 2 m. A number of leather pieces are rolled on one and the same cylinder, in accordance with customers' wishes. In some instances, one cylinder may carry up to ten leather pieces, all of which must be completely smooth, without the resemblance of a crinkle or fold. The significance of this requirement will be obvious to those who are aware of the irregularities in animal hides from the time of slaughter, an irregularity which becomes more pronounced subsequent to the tanning process. Hitherto, leathers have been rolled onto cylinders manually and the work entailed requires two highly routined workmen. The leathers are preferably placed on a table of requisite size with the grain-side up, whereafter a support cylinder or cylindrical support core is placed along one edge margin of the leather. The two operators or workmen then lay all of the edge flaps or lobes onto the cylinder, in an implicit fashion, and begin to roll the leather onto the cylinder. It is extremely important that none of these flap-portions pleat or crinkle during the first revolution of the cylinder. During the second revolution of the cylinder, the cylinder will have reached a position inwards of the table extremities which makes it necessary for the two workmen to pull the cylinder towards them, so that rolling-up of the leather can continue. This pulling of the cylinder must take place at a uniform speed and quite simultaneously at both cylinder ends, so as to prevent buckling or bulging of the leather. If care is not taken, a buckle will be rolled-on by the cylinder and perhaps impair the quality of the leather, even though no fold should be rolled-up with the leather. The same care and precision as that exercised with the first rolling-revolution of the cylinder must be exercised for each additional leather rolled onto the cylinder. Weight determines the number of leathers that can be rolled-up on one and the same cylinder, without rendering the cylinder unmanageable. Although endeavours have been made to roll leathers onto cylinders mechanically, the cylinders have been driven on spindles or by some other direct drive, and the occurrence of folds has become much too frequent to introduce mechanical rolling procedures in continuous manufacturing processes. The present invention provides a machine with which leathers can be rolled smoothly and free from folds onto delivery cylinders in a reliable and efficient manner, which is thus the object of the invention. The inventive machine by means of which this object is achieved has the characteristic features set forth in the following claims. The machine comprises a machine stand, a plurality of rollers journalled in the stand, and an endless web, preferably made of PVC, extending around said rollers. Mounted at a given location adjacent the edges of the web are two mutually opposed rollers which are carried by pivotal devices. The rollers function to draw the web in between the rolls to form a pocket in which a cylinder, onto which the material will be rolled, can be placed. In order to compensate for the length of web taken-up to form the pocket, the machine includes a stretching or tensioning roll, which is preferably vertically movable and is partially weight-compensated by pneumatic piston-cylinder devices connected to the ends thereof. The web is driven in a direction such as to move into the pocket and around the positionally movable rollers. EP-A-0095790 describes an apparatus similar to the above for collecting and temporarily storing sheets. In this apparatus the stretching and tensioning roll is partially weight-compensated by a load supported by a roller. This apparatus is intended to be automatically fed sheets of photographic material each of which have a constant thickness. Therefore this apparatus has no means of compensating for variations in the thickness of a sheet of the material being rolled. This makes it unsuitable for items such as skins which naturally have thickness variations and which cause the diameter of the roll to vary along its length, leading to unequal pressures on the ends of the roll. These unequal pressures are undesirable as they can cause folds or bulges to develop in the material being processed. In the machine according to the invention, the web runs on a table located forwardly of the pocket, where the leathers to be rolled onto the cylinder can be smoothed out. This can take place with the web stationary, whereafter two workmen start-up the machine, with the aid of a foot-controlled double-command. The tension roll is raised progressively as the leather is rolled-up smoothly on the cylinder to a rotational position of more than 180° embraced by the pocket. If only one single leather is to be rolled-up on the cylinder, it is sufficient to provide guide rolls solely at those locations where the web enters and exits from the pocket, although it has been found advantageous to provide several support rolls beneath the pocket when the weight of the leather rolled on said cylinder in- creases. The centre axes of these rolls are preferably located on an arcuate line, which can conceivably extend in the working direction of the machine. Should the thickness of the leather vary along the length of the cylinder, causing diameter of the leather roll to vary along its length, compensation can be made by controlling the position of the rollers which draw-in the web to form said pocket, with the aid of pneumatic piston-cylinder devices. These devices can be connected in series for the purpose of equalizing pressure, such that mutually equal pressures will prevail at the two edges of the web. If found desirable, web-tension sensors can be arranged to deliver signals to control the supply of air to respective pneumatic piston-cylinder devices, such that the web-edges will be subjected to different pressures. In order to afford a large degree of freedom when varying the speed at which the web moves, for instance to suit varying degress of adroitness of different workmen and in accordance with different desired working speeds, the machine may conveniently be provided with a gear motor. This motor may be provided with a frequency converter, for maximum speed control. The motor is conveniently connected for direct drive of a first drive roll and power is transmitted between this drive roll and a second drive roll on the input side of the feed table by means of a drive chain. Since forming the pocket, the second drive roll will preferably feed-in a greater length of web per unit of time than the length of web that is drawn-out from the pocket, it has been found advantageous to use for the second drive roll a toothed wheel, or sprocket wheel, having fewer teeth than the teeth on the first drive roll. In order to further improve the possibility of achieving a speed differential between the two drive rolls, the shafts of said rolls are provided with friction couplings or magnetic couplings connected to the toothed wheels. Subsequent to the requisite number of leathers being rolled-up on a cylinder, the web is stopped and the pocket-forming rollers moved to their starting positions. At the same time, the stretching roll is lowered such as to straighten-out the pocket, and the rolled leather is moved forwards on the feed table. A reciprocatingly movable, preferably chain-driven traversing lifting device mounted on the side-members of the machine stand is then moved in over the feed table. A gripping device is then lowered over the leather roll by means of an angled arm guided by a pneumatic-cylinder device. Two mutually hinged plates of part-cylindrical configuration are opened so as to embrace the leather roll. The plates are then closed by means of pneumatic piston-cylinder devices into clamping engagement with the leather roll, whereafter the gripping device is raised and the overhead lifting device is returned to the rear side of the machine, where the leather roll is deposited onto a receiving table for subsequent transportation to a packaging department. Because of the aforedescribed possibility of varying the diameter of the leather roll along the length of said roll, it is possible to axially move the web laterally along the machine rolls. For the purpose of monitoring or supervising this procedure, the machine includes photocells which are arranged mutually opposite one another on both sides of the web. Should the web be moved towards one side or the other, the web will break the light beam projected by the photocell on the side concerned, causing the photocell to deliver a signal to an air valve. In response, the valve will open and therewith increase the air-pressure in a pneumatic piston-cylinder device which therewith moves a stretching roll against the edge of the web, so as to centre the web in the machine. The pressure on the stretching rolls and also the pressure exerted by the stretching rolls are controlled in a manner such that the web will normally move at the same speed as the speed of the drive rollers. The drive rollers, however, have a drive surface such that friction against the web can readily be overcome. Consequently, the web is able to slide or slip slightly on the drive rollers. This has been found advantageous in those,cases when the leather roll is given a hardness appropriate to certain leather qualities. In order to enable the operators to use the machine more easily, the machine is constructed so that they need only activate a peddle control in order to initiate movement of the web, this peddle control being connected to a double-command means. The motor is also provided with a start-and-stop control. The machine is controlled in other respects by means of a computer in which all the air-pressure set-point values are programmed, together with the rotational speed of the pocket-forming stretching rolls. Other parameters, including the serial sequence of the machine operations, have also been programmed in the computer, whereby all procedures from the time of forming the pocket to the time of transferring the finished leather roll, which is finally wrapped with self-adhesive paper, are programmed in a given sequence. It has surprisingly been found that this programming of the procedural steps enables leather to be rolled in the absence of a support cylinder. A preferred embodiment of the invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 is a perspective view of a leather-rolling machine seen from the infeed side thereof; Figure 2 is a diagramme illustrating schematically the passage of the web through the machine; and Figure 3 is a sectional view of the machine taken in the direction of its longitudinal axis. A machine for rolling leather onto support cylinders or cores comprises a floor-mounted stand 1. The stand 1 includes two side members 2, 3 in which a number of rolls are journalled. An endless web 4, preferably made of PVC and having a thickness of about 2 mm, extends over the rolls mounted on said side members. Although not shown, the machine is driven by a gear motor to which electric current is supplied via a frequency converter, for the purpose of controlling the operating speed of the machine. This motor is connected directly to a first drive roll 5 which is connected to a second drive roll 7 by means of a chain 6. The chain 6 turns over toothed wheels 8 and 9 on respective first and second drive rolls. The toothed wheel 9 of the second drive roll 7 has fewer teeth than the toothed wheel 8 of the first drive roll 5. Mounted between the toothed wheels 8, 9 and the shafts of respective drive rolls are friction couplings, or magnetic couplings, which enable the drive rolls 5, 7 to rotate at smaller speed differentials than otherwise made possible by the number of teeth on the wheels 8, 9. As will be seen, the machine includes rollers 10 which act on both sides of the web 4 such as to form a pocket or "hollow" in which a support cylinder on which the leather is rolled can rotate. These pocket-forming rollers 10 are attached to angled, pivotally movable arms 11. Pivotal movement of the angled arms 11 is controlled by pneumatic piston-cylinder devices, not shown. The rollers 10 are rotated to draw-in sufficient web between an upper guide roll 12 and a lower support roll 25 to form a pocket, in which the support cylinder or core is placed. The cylinder is caused to rotate by the web 4 as the web is driven round in the machine. The web moves forwardly of the thus formed pocket smoothly over a feed table 13, on which the leather is successively laid-up. The web 4 moves the leather from the feed table 13 into the pocket and around the support cylinder, and the thus-formed leather roll increases in diameter with each revolution of the cylinder. That part of the web 4 which embraces the leather roll constitutes a progressively greater length of the web. In order to compensate for this progressively greater web-length consumed by the pocket, a web-stretching or pulling roll 14 is raised. The ends of this stretching roll are connected to respective pneumatic piston-cylinder devices 15, which can either relieve the weight of the stretching roll 14, and therewith stretching of the web 4, or increase the stretching force on the web 4 by a downwardly acting force. Which of the operating modes of the pneumatic piston-cylinder devices 15 is selected depends on how firmly the leather is to be wound onto the support cylinder. The web 4 is stopped and the guide roll or turn roll 12 raised, subsequent to having rolled-up the desired number of leathers on the support cylinder. The stretching roll 14 is lowered and the depth of the pocket reduced by moving the rollers 10 forwards, thereby moving the leather roll out onto the feed table 13. Prior to this, the leather last rolled onto the cylinder is taped-down with the aid of self-adhesive paper introduced into the pocket as a final stage of the leather rolling or winding operation. For the purpose of preparing the leather roll-up machine for the next leather roll-up operation, a traversing lifting device 16 which can be moved over the two side-members 2, 3 is moved over to a position above the feed table. The lifting device 16 carries on its underside a gripping device 17 which comprises two hemi-spherical plates 18 and 19. The plates are mutually hinged by a hinge arrangement 20 and at least one plate 19 is movable in relation to an angle arm 21 on which the gripping device 17 is mounted. The angle arm 21 is guided by a pneumatic piston-cylinder device 22 such as to enable the gripping device 17 to be opened and lowered over the leather roll on the feed table 13. The plate 19 can be moved forwards by means of a small pneumatic piston-cylinder device 23, such that the gripping device 17 will embrace the leather roll. A plexiglass sheet 24 is mounted in front of the plate 18, as a safety guard against clamping damage and in order to enable the machine operator to supervise the gripping movement of said device. Subsequent to gripping the leather roll with the device 17, the roll is lifted and the lifting device 16 is rolled to the rear side of the machine, where the leather roll can be deposited on a receiving table (not shown) which functions as a temporary storage prior to packaging the leather roll. The various working operations of the machine are computer controlled. The computer can be programmed to control the total speed of the machine and also the speed of each individual part operation. For instance, the computer can be programmed to control the speed at which the pocket is formed at the initial stage of the leather-rolling operation. Furthermore, the pressure in each pneumatic piston-cylinder device can be determined both with respect to time and with respect to total final pressure. In this way, the pressure in the pneumatic piston-cylinder device 15 can be controlled so that the web-stretching or web-pulling roll will hold the web so extended during the introduction of the leather-rolling operation that the first turns of leather wound onto the support cylinder will be wound firmly whereas the subsequent turns will be wound more loosely, or vice versa.

Claims: A motor-driven machine for rolling leather onto a support cylinder comprising a stand (1), rolls journalled in said stand (1), and an endless web (4) which runs over said rolls, rollers (10) which are carried by guide means (11) and which abut mutually opposite edges of the web such as to move said web in a manner to form a cylinder-accommodating pocket, a web-stretching or web-pulling roll (14) which extends over the full width of the web and which can be lifted in relation to the increasing length of web required to embrace the leather roll as more leather is progressively rolled-up on said cylinder, characterized by pneumatic piston-cylinder devices which activate the guide means (11) of said rolls (10) in a manner to adjust positionally the pocket-forming rolls (10), so that when the thickness of the leather rolled-up on said cylinder varies along the length of said cylinder, therewith resulting in variation of the diameter of said leather roll between the two ends thereof during a rolling-up operation, the pressure at which the pocket-forming rolls (10) abut the web (4) can be adjusted through the medium of different air-pressures in said pneumatic piston-cylinder devices thereby forming spaces of mutually different size at both sides of the pocket. A machine according to claim 1, characterized in that the web (4) is driven by a first (5) and a second (7) drive roll which are mutually connected by a chain (6) extending therebetween, said chain moving around toothed wheels (8,9) mounted on the shafts of said rolls, wherein the toothed wheel (9) of the second drive roll (7) located on the infeed side of the machine has one or more teeth fewer than the first toothed wheel (8) of the first drive roll (5), such that a greater length of web is able to pass over the second drive roll (7) per unit of time, so as to increase the size of the pocket as the diameter of the leather roll increases. A machine according to Claim 2, characterized in that friction couplings or magnetic couplings are provided between the toothed wheels (8,9) of respective drive rolls and the shafts of said rolls. A machine according to Claim 2 or 3, characterized in that the first drive roll (5) is driven by a gear motor controlled by a frequency converter. A machine according to any one of the preceding claims, characterized by a preferably chain-driven traversing lifting device (16) which effects a translatory movement on the side members (2,3) of the machine stand; in that said lifting device carries a raisable and lowerable gripping device (17) which functions to transfer finished leather rolls from the pocket to a table located on the rear or remote side of the machine, said table optionally sloping and forming a temporary storage facility, prior to packaging the leather rolls. A machine according to any one of the preceding claims, characterized by photocells which are mounted in mutually opposing positions on the sides of the web and which function to detect the web (4) as it moves through the machine and, when detecting that the web deviates from a straight course, delivers signals to web-stretching or web-pulling rollers provided on opposite sides of the web, said rollers function-ing to stretching or pulling either one or the other side of said web (4), according to requirement, such that the web will move centrally in the machine, such adjustment being made possible by the fact that the friction acting between the machine rolls and the web (4) is adapted so that the web (4) will move at a constant speed along its centre line. A machine according to any one of the preceding claims, characterized in that the machine is controlled by a computer which is programmed to deliver a series of signals for driv-ing, pocket-forming, web-stretching and extension of the rolling-up pocket, and also movement of the traversing lifting device and the gripping device. A machine according to any of the preceding claims, characterised in that for the purpose of supporting the pocket and the leather roll present therein during a working cycle, with the roll increasing in diameter and weight, the machine further includes a number of support rolls (25) which are mounted beneath the web (4) with the centre axis of said rolls being located transversely along an imaginary, concave arcuate line which extends in the direction in which the web (4) is driven.

Inventors: FREDELIN CHRISTER, FREDELIN, CHRISTER
Applicants: ELMO CALF, ELMO-CALF
Application year: 1991
Main classification: C14B1
IPC codes: C14B1, B65H19