METHOD AND APPARATUS FOR PERFORATING CLIPS OF PLAIN MATERIAL Description of the Invention
The invention relates to a method for drilling individual cuts of a flat material from the group of leathers, artificial leathers, foam materials, papers, filter papers, cardboards and sheets, by means of at least one group of needles with perforation needles, being that the cut-outs are transported by an endless conveying device to the area of action of the at least one group of needles, and are removed by sliding them out of the piercing needles by at least one trapping device. The perforation processes serve to allow the flat material to allow the passage of steam and air, that is, to provide it with breathing capacity or, for example, to provide filter papers with certain filtering characteristics. The main fields of application are the covering materials for upholstering vehicle seats, parts for shoes, gloves, clothing and filter papers. In a known process without a clamping device, the flat material is passed in the tensioned state as an endless belt through a gap between cylinders formed between needle cylinders and support cylinders. During the rotation of the needle cylinders, the piercing needles penetrate the stretched flat material, and the flat material slides back out of the piercing needles by the continuity of the transport, i.e., by the tensile stress of the strip of flat material. However, this procedure does not work with material that is not available in the form of endless strip: the sections of this material would be wound on the needle cylinders leading to a stoppage of the process. It is known from US Pat. No. 4,653,366 to perforate uniform individual cut-outs, for example with a rectangle-shaped contour, by means of a cylinder of needles, wherein the cuttings are first guided on an endless conveyor belt. located by means of a guide cylinder with two fixed flanges. To avoid that the cuts are wound on the cylinder of needles, between the cylinder of needles and the cuts that are placed on the conveyor belt should be arranged parallel steel strips, fixed at both ends, which can be raised and lowered with the needle cylinder by means of actuators operated by a pressure medium, and which can not be crossed by the needles. This has the disadvantage that it is necessary to interrupt the rows of needles in the multiple locations of the steel belts, so that in the cutouts alternate perforated girdles with non-perforated girdles. As a result, the average density of needles and perforations per unit area is reduced and, in many cases, it is insufficient. This known device is not intended nor is it suitable for a perforation uniformly distributed in cutouts of irregular contour, since it can not be prevented that the needles pull out parts of the edges of the cuttings by pulling them upwards between the steel belts, which it can lead to a blockage of the device. It is known from the German patent document DE 42 01 411 A1 to transport sheets of paper or the like individually through a stamping station by means of two endless conveyor chains, between which gauging carriages are arranged, and then to transport them by means of a endless treadmill for smoothing purposes before laying them on a suction box to which a vacuum is applied. However, for this purpose the tread strip is between the sheets of paper and the cover wall of the suction box, in order to prevent the sheets from being sucked into the suction box. Therefore the treadmill strip should actually be called "strip to keep up". There is no needle cylinder as well as an endless band that passes through the stamping station. No suggestions are given for the further development of a drilling machine. The object of the invention is therefore to provide a method of drilling with which finite sections of material can also be drilled., irregular or uneven, with a uniform distribution of the drilling holes and a high density of holes per unit area, without a blockage of the drilling process. The solution of the proposed task is carried out in accordance with the invention proceeding in such a way that the cut-outs are maintained on the conveyor device by means of a tread strip transferable by the perforation needles moving with the conveyor device. A procedure of this kind can be used with particular advantage for leather and its cuts, because this material is only available in finite sizes for natural reasons. The process can be carried out in a stationary manner, for example in a kind of stamping machine, in a semi-continuous form or with transverse transport in steps, or continuously. In the case of a process in which the at least one group of needles is formed in each case by a needle cylinder, it is particularly advantageous if the stepper strip is driven synchronously with the cut-outs through the action area or separation between cylinders of at least one cylinder of needles. A tread strip of this nature - of limited length - can be developed from a supply drum, pass it in a tensioned state through the separation between the at least one cylinder of needles and the cuttings transported on the conveyor device and, return it to roll over a receiving drum to reuse it, in particular to re-use it repeatedly. Alternatively, it is possible to use the tread strip as a consumer material and, for example, to stick it with the cut-outs to make the thin leather more resistant, since then the intimate connection is divided again into individual cuts. However, it is particularly advantageous if the tread strip is configured as an endless strip and is passed on multiple occasions at the speed of transportation of the cuts through the area of action of the at least one cylinder of needles, that is, through of the separation between cylinders. As material for such treading strips, strips of textile material can be used, in particular woven strips, which have sufficient shelf life against the piercing needles. The invention also relates to an apparatus for perforating flat material from the group of leathers, artificial leathers, foam materials and sheets, with a conveying device for the flat material, with at least one group of needles with perforating needles and, with at least one trapping device that is disposed between the conveying device and the group of needles, and by which individual cutouts can be removed by sliding them out of the piercing needles. For the solution of the same task an apparatus of the type under consideration is configured in such a manner according to the invention, that the trapping device is configured as a treading strip that can be passed synchronously with the cut-outs through a gap between cylinders between the at least one cylinder of needles and the conveyor device. Such an apparatus is also suitable as a universal device for drilling endless material with a high and uniform hole density, whereas, on the contrary, apparatuses according to the state of the art are not suitable for perforating irregular or irregular cuttings. unequal. With the object of the invention it is possible to achieve without more piercing densities of up to 50 perforations per square centimeter with a single cylinder of needles, by means of a corresponding quantity of piercing needles. For this purpose it is particularly advantageous if the at least one group of needles is formed in each case by a cylinder of needles, and if the tread strip can be driven in a synchronized manner with the cuts through a gap between cylinders between at least a cylinder of needles and the cuts that are on the transporador device, particularly if the tread strip is configured as an endless strip. The effect of the tread strip is particularly advantageous if a guide cylinder is disposed in each case before the first needle cylinder and after the last needle roller, by means of which the tread strip can be retained on the cutouts. By means of this resource the embracing angle of the needle cylinders is kept to a minimum and the tread strip is maintained. In the following, two embodiments of the object of the invention are explained in more detail on the basis of FIGS. 1 and 2. They show, in each case in lateral elevation, FIG. 1 an apparatus with a finite trailing strip, and FIG. 2 a apparatus analogous to that of figure 1, but with endless treading strip. In figure 1 is represented a machine frame 1 on which there is a conveyor device 2 which is configured as an endless conveyor belt 3. This is driven on two cylinders
4 and 5 inverters and three support cylinders 6, and is constituted by a tensile-resistant material of which at least the outer surface is of soft consistency and consists, for example, of a foam material, a non-woven fiber fleece or a felt. The supports, drive means and tensioning devices are not represented to simplify the presentation. Above the support cylinders 6, a group of needles in the form of a needle roller 7 is parallel to its axes. The number of needle cylinders is variable and is a function of the required degree of drilling density, which in the case of three needle cylinders can be, for example, 150 holes per square centimeter after the last needle cylinder 7. The support cylinders 6 and the needle cylinders 7 each form a gap 8 between cylinders, through which they are guided - viewed in sequence from bottom to top - the conveyor belt 3, the cut-outs 9 and a gripper shape of a finite 10 stepper strip. This stepper strip 10 comes from a supply drum 11 and is wound again on a receiving drum 12, both of which are supported on a support frame. By driving and braking (both not shown), the tread strip 10 is kept under tension around the reversing cylinders 14. Before the first needle cylinder 7 and after the last needle cylinder 7, and advantageously also after each needle cylinder 7, the tread strip 10 is held downwards and tensioned horizontally on the cutouts 9 by the guide rollers 15 and 16, being that naturally the piercing needles also go through the tread strip. The cut-outs 9 are placed on the left end of the conveyor device 2 and fall in the perforated state into a receiving container 17. Figure 2, in which the same reference symbols are used, differs from Figure 1 in that an endless treadle 10a is employed, which is held taut by the horizontal displacement of the cylinder 1-4 inverter on the right that it is carried out with a tensioning device 18, which is indicated by a double arrow. The proportions of the thicknesses and the lengths of the needles are represented in exaggerated form.