METHOD OF AND APPARATUS FOR TENTERING A HIDE

Abstract: Method of and apparatus for tentering a hide. In a continuous-action tentering method, endless tentering mats (1, 2) are circulated along an upper and lower endless run. By means of compressed air, passed inside run eyelets, said mats (1, 2) are pressed face-to-face over a given run section. Stretching means gripping the mat edges are used to stretch the face-to-face pressed sides of the mats continuously as they advance. An endless delivery wire (5) is used to feed hides into the nip between mats (1, 2). An advantage gained by the method is a high rate of speed and advantages gained by the apparatus include high reliability in operation and long service life.

Description: Method of and apparatus for tentering a hide. The invention relates to a method of tenetering a hide, wherein endless, elastic tentering mats are circulated along an upper and lower endless run and a hide is squeezed between the tentering mats and tentering is effected by stretching the mats in a direction cross¬ wise relative to the running direction. The invention relates also to an apparatus for carrying out the method and the apparatus comprises two annular or hose¬ like hide tentering mats, adapted to circulate along endless runs in a manner that the lower run of the upper mat is squeezed or pressed against the upper run of the" lower mat, said mats being made of an elastic- ally extensible material, and mat stretching means for " stretching the face-to-face pressed runs of said mats in a direction crosswise relative to the running direct¬ ion. Tentering of a hide serves to open its fiber structure for softening a hide. At the same time, the surface area increases. It is prior art to carry out the above type of method and apparatus in. single action so that the edges of circular or elliptical stretching mats are gripped by a plurality of radial stretching means for stretching the mats radially from center towards the sides. The face-to-face pressed edges of the mats are sealed and the mats are squeezed face-to-face by sucking a vacuum in the space between the mats. This prior art method and apparatus involve several drawbacks. ■ First of all, a single-action method is slow as all various steps of the method must be repeated separately for each hide to be tentered. Secondly, the construction is sophisticated and expensive as it requires a plural¬ ity of radial power units for stretching the mats. Thirdly, the compressive force is irregular since the vacuum is not distributed evenly all the way to the central.area of a hide. This, results in irregular stretching of a hide. In the fourth place,, the apparatus has proved unreliable as to its durability, since the-- stretching mats have of en been ripped adjacent to the rim-gripping fastening means or at the vacuum duct lead-in. When a mat is stretched in all directions, the length of i.ts rim increases but the rim-gripping fastening means of said stretching units prevent the increase of peripheral length over approx¬ imately half of the peripheral distance, the increase of the peripheral length occurring as a disproportionat¬ ely large peripheral elongation between the gripping means, resulting in untimely tearing. French Patent publication 2 267 268 discloses a hide stretching means, wherein the stretching elements in the form of aperture discs are adapted, to be. shifted along an endless run or track. The side runners of said track comprise a. section where the side runners are closer to each other, whereby the forcepts gripping the hide edges can be secured in the nearest apertures of said aperture discs. Thereafter, the side runners are drawn away from each other to the plane of the side runners of the rest of said track and the tentering track is shifted forward. The apparatus is not a con- timuous-action unit but the fastening and removal of hides must be effected as tedious manual work with the track stopped. Neither is stretching of the mats based on continuous mat stretching as the mats advance for¬ ward but, instead, the. stretching occurs first locally and most of the endless track or run serves like a storage for stretched hides. This prior art device is slow and requires a lot of work. The capital costs and operating costs, will be high in terms of productive . capacity. FI Patent application -823457 and DE publication print 1 760 381 disclose tentering and stretching of a hide between endless, elastic mats. Stretching of the mats is effected by means of special ram members for work¬ ing mechanically from each side of the face-to-face pressed sections of the mats. Thus, the compressive engagement between mats and a hide is local, resulting in relative slipping between mats and a hide in areas which lack sufficient compression. For example, the crosswise stretching results in lengthwise retraction of a hide. When, at the point of stretching, said stretching mats have extended more than a hide to be stretched, a consequence is that, after the point of stretching, with the mats retracted to their original state, said mats crumple a hide therebetween resulting in the formation of wrinkles thereon. An object of the invention is to provide a continuous- action method and apparatus for tentering the hides at a high productive capacity while ensuring the prime quality work by pressing or squeezing a hide to be tentered entirely between the mat runs to be stretched with sufficient and uniform compressive force. This object is achieved on the basis of the inventive features set out in the annexed claims. One embodiment of the invention will now be described in detail with reference made to the accompanying draw¬ ings, in which fig. 1 is a schematic vertical section of an apparatus of the invention and fig. 2 is a pain view of the interior of said apparatus. Fig. 3 shows a cross-section taken through the rear end of the apparatus and fig. 4 illustrates a detail- shown in fig. 3 to a larger scale. As shown in fig. 1, two endless tentering mats 1 and 2 are adapted to circulate along an upper and lower endless run. Mats 1 and 2 are passed around swing rollers 3 and 4. Swing rollers 3 and 4 are located at the outset and terminal ends of the face-to-face press¬ ed run sections of mats 1 and 2. The terminal end rollers 4 are adapted to be driven in a manner de¬ scribed in more detail later, so that the face-to-face pressed run sections of mats 1 and 2 travel in the di¬ rection indicated by the arrows. The face-to-face pressing of mats 1 and 2 over the entire area with a uniform pressure is accomplished by means of compressed air supplied inside the mat eye¬ lets. The open ends of mat eyelets are closed and sealed as described later. Mats 1 and 2 are made of- an elastic material, such as rubber, the mats being extensible crosswise relative . to their -running direction. At least the rim- areas of mats 1 and 2 are provided with reinforcing wires, ex¬ tending in the running direction and keeping constant the peripheral length of mat eyelets. The hides to be tentered are fed in between mats 1 and 2 by means of an endless wire 5, running between the face-to-face pressed sides of mats 1 and 2. Wire 5 is also extensible crosswise relative to the running di¬ rection. The return run of wire 5 is passed around swing rollers 6, one swing roller 6 being positioned so as to. build in front of the feed-in point between rollers 3 an elongated delivery table for spreading a hide to be tentered thereon. The hide tentering is thus effected by stretching the face-to-face pressed run sections of tentering mats 1 . and 2 crosswise relative to the running direction in a manner that the. stretching force and s.tretching dis¬ tance or elongation increase continuously towards the terminal end of the nip between said mats. As a hide will thus be tentered in a single delivery in one di¬ rection, each hide must be delivered through a contin¬ uous-action tentering apparatus twice, the second tentering step serving to stretch a hide in the di- ' rection perpendicular to the stretching direction of the first tentering step. Despite the double delivery, the continous action of the apparatus means that the increase of the rate of speed will be approximately triple, as compared to a single-action apparatus. Although the tentering could, in principle, be effected " in all directions at the same time (which solution is not beyond the scope of invention) , the present embodi¬ ment is preferred as it increases the durability and service life of a rubber mat, simplifies the apparatus construction and, by means of two separate stretching or elongation perpendicular to each other, the fiber structure can be opened more effectively than by effect¬ ing the elongation in all directions at one time. Thus, a hide can be softened more effectively. Extended through mateyelets are main pipes 7 from which extend bars 8, with swing rollers 3 and 4 journalled thereon. Compressed air can be supplied into mat eye¬ lets through main pipes 7. The return runs of mat eyelets are on the outside supported by means of rollers 9 , mounted on cover sect¬ ions 10 and 11. Cover sections 10 and 11 can be removed in whole units for maintenance or replacement of the tentering mats. The following describes In more detail the tenetering means for gripping the edges of tentering mats 1 and 2, with reference to figs. 2-4.. To both edges of mat 1, 2 are fastened adjacent track shoes 12 which, together with chains 13 fastened to the inner surfaces of said track shoes, build up chain tracks which follow the mat edges. Each extreme chain link 13a of chains 13 is secured to a track shoe 12. The articulated shafts of chains 13 lie in the same plane as the middle plane of mat 1, 2. Thus, no stresses are produced at the reversing points between mat 1, 2 and chain track 12, 13. At the positions corresponding to the swing rollers 3 and 4 of mats 1 and 2 there are provided sprockets 14, whose shafts 18 are journalled to frame plates 21. The shafts 18 with its sprockets 14, positioned at the rear end rollers .4, are connected by way of a reduction gear 19 to a motor 20. Drive shafts 18 are connected by means of articulated shafts, not shown, to the corresponding rear end rollers 4, whose opposite ends are in turn connected by means of articulated shafts to shafts 18 on the left in fig. 3, both rear end rollers 4 and the chain tracks at both edges of mats 1 and 2 being thus driven. In fig. 3, rollers 4 and the articulated shafts engaging their ends are not shown. The angle of inclination of shafts 18 shown in fig. 3 serves to stop the stretching of mats 1 and 2 immediately after the nip of rollers 4, said stretch¬ ing not proceeding to the outermost point of rollers 4 where no stretching any longer occurs. The angle of inclination of shafts 18 is also significant in terms of space utilization since, despite the described chain track construction, the mats can be guided against each other. For the lateral stretching of the mats, the ends of track shoes 12 are provided with hook-like members 12a to whose inner surfaces are fastened slide members 12b, made of e.g. plastics a_nd rested against the surface 15a of a guide track 15. A guide track 15 can be made as a single integral element whose outline follows the shape of the mat eyelets shown in fig. 1. As an alter¬ native, a guide track 15 may comprise two wheels mounted on shafts 18 and a fixed member extending therebetween. What is essential is ' that guide tracks 15 are secured to end plates 21 that can be pivoted to the position shown by dot-dash-lines in fig. 2 whereby, when pro¬ gressing in the hide-feeding direction, said end plates 21 and simultaneously therealong said guide tracks 15 together with their guide surfaces 15a diverge from each other on the opposite sides of the apparatus. A result of this is that the face-to-face pressed sides of rubber mats 1 and 2, advancing in the diverging di¬ rection of guide tracks 15, will be tentered or stretch¬ ed in lateral direction. The stretching force is trans¬ mitted by way of the bent ends 12a of track shoes 12 and slide members 12b to the surfaces 15a of guide .tracks 15. The return runs of mats 1 and 2, in turn, travel in the direction in which the guide tracks 15 on the opposite sides of said apparatus converge, the elasticity of said mats brings the mats back to their original width for renewed stretching and tentering. It can now be appreciated that the inclined position of shafts 8, tracks 15 and end plates 21, as shown in fig. 3, results in quicker set-off of retraction with¬ out unnecessary extra stretching after the nip between rollers 4. ' The elongation or degree of tentering of mats 1 and 2 can be readily adjusted in stpless fashion by means of a piston-cylinder unit, which grips the frame 21 at a point 25 and is capable of turning plate 21 around a shaft 24. The turning point 24 can also be shifted crosswise of the apparatus, whereby the permanent elongation remaining in the mat can be compensated for whenever necessary. Each track shoe 12 is fastened by means of a link 16 to a metal gripping plate 17, which is riveted to a metal sheet on the opposite side of the edge of mat 1, 2. At the same time, between the fastening plates is sqeezed a lip seal 23, leaning against an end plate 22 shown in fig. 3. Each open end of both mat eyelets is closed with an end plate 22 matching the shape of a mat eyelet (see fig. 1). Thus, the internal space " of said mat eyelets has been made air-tight for com¬ pression with compressed air. Hence, the compressive force is uniform over the entire face-to-face pressed area of mats 1 and 2. As shown in fig. 2, end plate 22 is connected to frame plate 21 by way of a pipe .26. The lead-in of a main pipe 7 is sealed with a sealing 27 to said frame plate 21. Energy consumption of the apparatus is low since the energy used for stretching the rubber mats is largely recovered as a thrust generated by the retraction of mats occurring on the return side. This advantage cannot be found in a single-action device. It is appreciated that the above-described apparatus construction is just one exemplatory embodiment, with a plurality of modifications conceivable to a skilled person within the scope of the invention. For example, a guide track can be made of successive rollers, which engage themselves behind the catch members provided on or fastened to the edges of tentering mats.

Claims: Claims 1. A continuous-action method of tentering a hide, wherein endless,.- elastic * tentering mats {1, 2)- are circulated along an" upper and lower endless run and a hide is. squeezed between the tentering mats and tenter¬ ing is effected by stretching the mats in a direction crosswise relative to the running direction, c h a r a c t e r i z e d in that mats (1 , 2) are pressed face-to-face with .compressed air supplied in¬ side the eyelets formed by the endless mat runs, that over the face-to-face pressed run sections of mats (1, 2) said mats are continuously stretched by tentering the mats by means of their edge-gripping stretching members (12,. 15, 21) from center towards the sides as the mats advance forward so as to increase the tenter¬ ing force and stretching distance produced by stretch¬ ing means (12, 15, 21) gripping the edges of said mats, said increase occurring in the running direction to¬ wards the terminal end of a nip between said mats, and that, over the return run sections of said mats, the elasticity of said mats is allowed to re-establish the mats to their original width for renewed stretching and tentering. 2. A method as set forth in claim 1, c h a r a c t e r i z e d in that a hide is passed in between the mats on endless wire (5) , travelling between the face-to-face pressed sides of said mats. 3. A method as set forth in claim 1 or 2, c h a r a c t e r i z e d in that each hide is passed through a continuous-action tentering means twice, in a second tentering step the hide being stretched in a direction orthogonal- to the stretching direction of the first step. 4. An appratus for carrying out the method set forth in claim 1, 2 or 3, said apparatus comprising two annular or hose-like hide tentering mats (1, 2), adapt¬ ed to circulate along endless runs so that the lower run of the upper mat is pressed against the upper run of the lower mat, said mats being made of an elastic- ally extensible material, and mat stretching means for stretching the face-to-face pressed runs of said mats in a direction crosswise to the running direction, c h a r a c t e r i z e d in that the eyelets provided by said endless mat runs are sealed (22, 23) into closed pressure chambers or spaces and that said mat stretching means comprise on one hand edge-gripping track shoes (12) and on the other hand guide tracks (15, 15a) for track shoes, said guide tracks, when ad¬ vancing in the running direction of the face-to-face pressed sides of said mats, diverging from each other thus producing the diverging running paths for track shoes (12) for stretching the face-to-face pressed sides of the mats in a direction crosswise relative to the running direction. 5. An apparatus as set forth in claim 4, c h a r a c t e r i z e d by an endless wire (5) , which runs between the facε-to-faσe pressed sides of the mats and extends a substantial distance rearwards of the feed- in point of hides. 6. An apparatus as set forth in claim 4, c h a r a c t e r i z e d in that fastened to track shoes (12) are chains (13) for driving the track shoes, said chains, together with track shoes (12) , building chain tracks for gripping the edges of said mats. 7. An apparatus as set forth in claim 6, c h a r a .c t e r i z e d in that sprockets (14) of chains (13) have their shafts (18) journalled to frame ' plates (2.1) of the apparatus and make up -revers¬ ing wheels" for chain tracks (12, 13), and that mats (1, 2) are passed around swing rollers (3, 4) position¬ ed at the outset and terminal ends of the face-to-face pressed run sections of the mats, and that the terminal end rollers (4) are adapted to be driven by coupling them by way of articulated, shafts to the shafts (18) of said sprockets (14), the latter shafts being connect¬ ed to a drive motor (20) . 8. An apparatus as set forth in any of the preceding claims 4-7, c h a r a c t e r i z e d in that the return runs of mats (1, 2) are supported from the outside by means of rollers (9) or the like, that the side edges of said mats are sealed with sealings (23) , leaning against end plates (22) which close the end openings of mat eyelets, and that inside the eyelets formed, by the mats is passed compressed air.

Inventors: VILJANMAA LEENA, VILJANMAA,LEENA
Applicants: VILJANMAA LEENA, VILJANMAA,LEENA
Application year: 1985
Main classification: C14B1
IPC codes: C14B1, C14B17