Patent Publication Number: US-2016229662-A1

Title: Winding shaft

Description:
The invention relates to a shaft axle for winding a material web, particularly plastic films, and here particularly stretch films. Additionally, the invention relates to a method for producing such a shaft axle as well as a winding device comprising such a shaft axle. 
     Winding shafts, comprising a shaft axle and a winding core for winding up and/or unwinding web-shaped, tape-shaped, or string-like materials of very different kinds, for example paper, aluminum, and plastic films, textiles, or fleece-like webs or the like, are widely known and designed particularly for the respective purpose for use and/or the specific winding technique applied. 
     The acceptance of the winding core in an appropriate winding device occurs commonly via expanding tension bars and/or tension pads with a mechanic or pneumatic control, causing a central stress of the winding core and allowing driving of the winding core even with strong torque. 
     Particular requirements of the winding core also arise during the winding up of stretch films. 
     Stretch films—depending on the respective application, also loading unit/safety film, pallet stretch film, winding stretch film, or packaging stretch film—are indispensable in modern logistics for the transportation of goods loaded on pallets. In addition to securing the pallets, such films also protect the goods on the pallet from exposure to weather and soiling. Here, the stretch film adjusts optimally to the shape of the pallet and the products without damaging them. 
     Additionally, in the meantime various semiautomatic or automatic stretching facilities for “stretch-wrapping” the pallets with the goods located thereon have become available for the application of the stretch film. 
     Stretch films are produced in most different thicknesses and widths. Typically, for example, film thicknesses are from 12-35 μm with a width of the roll from 200 mm to 1,000 mm, preferably 500 mm, which are wound onto rolls weighting 10-20 kg. 
     With presently approximately 1.5 million tons annually within Europe alone and approx. 3.0 million tons per year globally the market of stretch films will be of substantial volume in the future as well. The requirements set for the equipment for the production of stretch films are therefore steadily increasing with regards to efficiency and output. These increasing demands must be met by the winding device, which winds up the produced, finished stretch film onto a winding core at the end of the production facility. Here, a winding core may be used over the entire production width. Usually, however, several winding cores are used side-by-side, with the stretch film then prior to being wound onto the winding cores being divided in the direction of production by knives aligned appropriately. This way, for example, at a production width of 1,500 mm, here three application widths of 500 mm each are produced parallel and wound up. 
     The winding cores themselves are generally made from a cardboard tube and may be very different, depending on the application, with regards to width, interior diameter, and exterior diameter, and thus also with regards to their wall thickness. 
     In order to allow winding up the produced stretch film on the winding core for all applications, the respective winding device shows a shaft axle with adjustable tension pads for a radial clamping of the respective winding cores. However, since it is not known in advance what kind of winding cores will be placed upon the shaft axle, the shaft axle must be designed to accommodate all potential types of applications. Simultaneously it must be observed that the stretch film to be wound up shows great elasticity of up to 400%, due to the features described above. This leads to extreme requirements set for the shaft axle. 
     A winding device is known from WO2013/003968 A9, in which the shaft axle is supported at both sides in a double bearing, in order to prevent any undesired vibrations of the shaft axle and simultaneously allows high circular accelerations. 
     In order to yield high bending stiffness for the shaft axle with a simultaneously low external diameter, it is also known to produce the shaft axles entirely or partially from fiber-reinforced composite materials, as described for example in WO 2005/124212 A1 or in U.S. Pat. No. 5,746,387. 
     Shaft axles made from fiber-reinforced composite materials are commonly made from plastic or a cross-linked resin material (reaction resin), which comprises reinforcing fibers, for example natural fibers, fiberglass (FBE=fusion bonded epoxy material) or carbon fibers (CFL=carbon fiber laminate), in the form of sections of a final length, continuous fibers, fleece or webs. Composite materials with fibrous sections are particularly extruded continuously or processed by extrusion molding. Composite materials with continuous fibers are particularly processed in winding processes (filament winding) or by way of pultrusion in order to form tubes or sheaths. 
     CFRP shafts (=carbon fiber reinforced plastic) are particularly suited. Here, CFRP regularly comprises aligned continuous fibers, which are embedded in a plastic matrix, usually in several layers. The recesses required for the tension bars, however, reduce the strength and stiffness of the shaft axle in an undesired fashion. 
     The objective of the invention is therefore to provide a shaft axle with a strength and stiffness as high as possible. 
     This objective is attained in a shaft axle for winding up a material web, comprising a shaft body, made largely from fiber-reinforced plastic to yield bending stiffness as high as possible, and showing cavities, which are provided along the external perimeter of the shaft body, with said cavities being limited in the radial interior direction by a layer made from fiber-reinforced plastic and allowing tension bars to extend in the radial exterior direction out of the cavities. 
     An essential acknowledgement of the invention comprises that the cavities for the tension bars are not made from radially continuous recesses but are limited in the radial interior direction by a layer of fiber-reinforced plastic. This way, the strength and stiffness of the shaft axle can be effectively increased. 
     According to a preferred embodiment it is provided that the fiber-reinforced plastic is made from aligned continuous fibers, which are connected via cured resin. 
     According to another preferred embodiment it is provided that the aligned continuous fibers are made from carbon fibers. 
     According to another preferred embodiment it is provided that the tension bars show at their radial end cup-shaped elements, which are made from plastic and/or a fiber-reinforced material. 
     A potential method for producing the shaft axle according to the invention is a method in which formed bodies are provided for accepting tension bars that can radially expand, around which continuous fibers are layered, with the formed body in the radial internal direction resting on at least one layer comprising aligned continuous fibers, in which the formed bodies together with the continuous fibers are connected via a cured resin, and in which after the curing of the resin the radially expandable tension bars are inserted into the formed bodies. 
     The formed bodies may be made from aluminum or plastic, for example. In order to allow the formed bodies to sit fixed in their fittings, to the extent possible, the formed bodies may, in addition to the holding strength of the resin, also be adhered and/or screwed in. 
     Another method for producing the shaft axle according to the invention is a method in which for the purpose of yielding a bending stiffness as high as possible a shaft body is produced largely from fiber-reinforced plastic, with cavities being cut into the shaft body along the perimeter, with said cavities being limited in the radial interior direction by a layer made from fiber-reinforced plastic, and tension bars being inserted in the cavities that can radially expand. 
     The winding device for winding up a material web with a shaft axle according to the invention preferably represents a winding device with a bearing arrangement located at least at one side of the shaft axle, in which the respective end of the shaft axle is supported in two sections distanced from each other. 
     According to a preferred embodiment, bearing arrangements are provided at both sides of the shaft axle, with the ends of the shaft axle resting therein, with each of the two bearing arrangements supporting the corresponding end of the shaft axle in two areas distanced from each other. 
     According to another preferred embodiment, at least one winding core is provided encompassing the shaft axle, which can be fixed in reference to the shaft axle via the expanding tension bars. 
     The advantages of the invention are overall higher strength and stiffness of the shaft axle as well as its support, allowing permanently higher production speeds due to a higher rotation critical for bending. 
    
    
     
       Further details and advantages of the invention are described based on the attached drawings. Here it shows: 
         FIG. 1  a winding shaft with a disadvantageous alignment of the cavities in reference to the continuous fibers, 
         FIG. 2  a winding shaft with an alignment of the cavities to diagonally extending continuous fibers, 
         FIG. 3  a winding shaft with an alignment of the cavities towards axially extending continuous fibers, 
         FIG. 4  the support of a shaft axle at both sides via double bearings, and 
         FIG. 5  a cross-section through a shaft axle according to the invention. 
     
    
    
     At first, the alignment of the cavities is described in reference to the continuous fibers. 
     When the shaft axle is produced with continuous fibers in a winding process (filament winding), it must be observed that a parallel alignment of the continuous fibers in reference to the axis is not possible due to the limitations of the machines provided for the production of the winding core. Rather, only an alignment up to approx. 7° in reference to the axial direction is possible. If now, as shown in  FIG. 1 , the recesses of the cavities are still aligned axially, then this has negative influences upon the strength and stiffness of the shaft axle due to the intersecting continuous fibers. 
       FIG. 1  shows the left half of a winding shaft with a shaft axle  101 . The winding shaft shows axially aligned cavities  102 , into which the tension bars can be inserted, which can be pressed pneumatically towards the outside and optionally can be retracted again by a spring force. The alignment of a first layer of continuous fibers is indicated by  103  and the alignment of a second layer of continuous fibers inside the shaft axle by  104 . Due to the fact that the cavities shorten the continuous fibers  103  and  104 , this alignment of the cavities has negative influences upon the strength and stiffness of the shaft axle. 
       FIG. 2  shows a winding shaft with a shaft axle  201  and with an alignment of the cavities towards diagonally extending continuous fibers. The reference characters  201 ,  203 , and  204  are equivalent to the reference characters  101 ,  103 , and  104 , so that in this regard reference can be made to the description of  FIG. 1 . However, the cavities  202  are aligned here along the direction of the continuous fibers  204  so that said negative influence upon the strength and stiffness of the shaft axle can be reduced. 
       FIG. 3  shows a winding shaft with a specially produced shaft axle  301 , as known for example from WO 2005/124212 A1. The reference characters  301  and  302  are equivalent to the reference characters  101  and  102  of  FIG. 1 , so that in this regard reference can be made to the description of  FIG. 1 . The shaft axle is here produced such that the aligned continuous fibers  303  extend axially in reference to the shaft axle  301  and to the axially aligned cavities  302 . This is possible according to WO 2005/124212 A1 by the use of reinforcing ribs, which were produced in a pultrusion method and which allow a particularly high content of fiber volume. 
     The cavities are therefore aligned accordingly as well. 
       FIG. 4  shows the support of a shaft axle with double bearings at both sides, as known from WO 2013/003968 A9. WO 2013/003968 A9, however, fails to disclose the combination of a double bearing with a shaft axle made from fiber-reinforced plastic. This combination is also particularly advantageous in the point of view of the invention. The shaft axle  401  produced from CFRP is clamped fixed at the left side in the double bearing  402 . The bearing arrangement  403  is also embodied as a double bearing, however, this bearing arrangement is detachable via two-armed pliers so that one or more winding cores can be pushed from the right onto the shaft axle and/or can be removed therefrom again, after the pliers unit has pivoted away the bearing arrangement  403 . 
       FIG. 5  shows a cross-section through a shaft axle according to the invention of fiber-reinforced plastic. The shaft axle  501  shows five cavities distributed over its perimeter, in which the pneumatic tubes  502  as well as articulate tension bars  503  are inserted. The cavities are limited in the radial interior direction by a layer of fiber-reinforced plastic, so that the desired stiffness of the shaft axle is yielded. Optionally, but not necessarily, the tension bars  503  are additionally pre-stressed with spring elements which move the tension bars into the position shown in  FIG. 5 a    as soon as sufficient air has been removed from the hoses  502 . If the tension bars  503  are not pre-stressed, the tension bars  503  are in a position between the respective stops when air has exhausted, without it here being possible to transmit any torque upon the winding core located at the outside. 
     If now, based on the condition according to  FIG. 5   a,  the hoses  502  are filled with compressed air, the condition according to  FIG. 5 b    develops, according to which the tension bars  503  are extended and can apply a radial force upon the winding core located at the outside. 
     The tension bars  503  may extend continuously in the axial direction over the entire shaft axle. Alternatively it is also possible that the tension bars are made from several smaller elements, with their quantity being selected such that sufficient torque can be transmitted to the winding core located at the exterior. 
     The shaft axle  501  itself may be produced entirely from fiber-reinforced plastic or may be made from a hybrid structure with fiber-reinforced plastic and metal. 
     LIST OF REFERENCE CHARACTERS 
     
         
           101  shaft axle 
           102  cavity and/or tension bar 
           103  alignment of a first layer of the continuous fibers 
           104  alignment of a second layer of the continuous fibers 
           201  shaft axle 
           202  cavity and/or tension bar 
           203  alignment of a first layer of the continuous fibers 
           204  alignment of a second layer of the continuous fibers 
           301  shaft axle 
           302  cavity and/or tension bar 
           303  aligned continuous fibers 
           401  shaft axle 
           402  bearing arrangement, fixed 
           403  bearing arrangement, detachable 
           501  shaft axle 
           502  pneumatic hoses 
           503  tension bar