Abstract:
A heating device (1) for a corrugated cardboard facility includes several heating plates (3) arranged sequentially along a path in the advancing direction of a sheet of corrugated cardboard (2). Compression elements (4) are arranged above the heating plates (3) in position to act on the sheet of corrugated cardboard (2) as it advances along the path. An intake belt (e) is located in a starting area (a) of the heating plates (3) between at least a part of the sheet of corrugated cardboard (2) and at least one compression element (4.1, 4.2).

Description:
BACKGROUND OF THE INVENTION 
     The invention pertains to a heating device for a corrugated cardboard facility and, more particularly, to such a heating device having several heating plates arranged sequentially in the advancing direction of the sheet of corrugated cardboard, and also having compression elements arranged above the heating plates for acting on the sheet of corrugated cardboard. 
     Such a device in a corrugated cardboard facility has the function of drying glue between superimposed sheets, for example, one-sided sheets of corrugated cardboard and finally the cover sheet. 
     To this end, known devices have heating plates that are heated, for example, with steam or thermal oil. By means of a continuous transport belt, the sheet is conveyed through the heating zone. Compression elements press the sheets of corrugated cardboard against the surface of the heating plates in order to achieve an appropriate contact of the sheets of corrugated cardboard with the surface of the heating plates, that is, a good transfer of heat to the glue line. 
     In the case of one known compression unit shown in U.S. Pat. No. 5,632,830, weighted rollers are also used, which are affixed by intervening levers to a bearing arranged transversely to the advancing direction of the sheet of corrugated cardboard. 
     Further state of the art is also a compressing unit in the form of a pressure plate consisting of several units extending along the sheet of corrugated cardboard as shown in Canadian Patent No. 2,197,921. Also known is the use of pressure hoods shown in European Patent Publication EP 0,412,255 A1, as well as rollers shown in U.S. Pat. No. 5,632,830, which exert pressure on a circulating conveyor belt. 
     In order to avoid the disadvantages of the transport belt, it is also state of the art, as shown in U.S. Pat. No. 5,632,830, that the transport belt is eliminated and the sheet of corrugated cardboard is pressed directly against the heating surfaces by compression elements. 
     When the transport belt is dispensed with, however, automatic intake of the introduced sheets is no longer possible. Furthermore, eliminating the transport belt results in increased friction with the cardboard, and this increased friction produces frequent tears in the cardboard as it passes through the heating zone. Tears in conjunction with troublesome reinsertion bring about unacceptable production losses. 
     SUMMARY OF THE INVENTION 
     Accordingly, the basic objective of the present invention is to create a corrugated cardboard heating device in which the sheets of corrugated cardboard arriving from preceding parts of the facility are drawn in and automatically advanced through the beltless part of the heating device. 
     This objective is realized according to the invention, in that an intake belt is located in the starting area of the heating plates between at least a part of the sheet of corrugated cardboard and at least one compression element. With the aid of this intake belt it is possible to join together functionally securely the individual layers of the corrugated cardboard and also to compensate for any possible frictional losses of the preceding facility sections. 
     The intake belt can be designed as a conveyor belt running over two physically separated deflection rollers. Here there exists the possibility that the conveyor belt is acted upon by at least one compression element oriented in the advancing direction of the sheet of corrugated cardboard. Furthermore, the intake belt can be designed to be heated. 
     For good adaptation to the given conditions, it is possible that the distance between the two deflection rollers be variable. Here the rear deflection roller can be designed to be displaceable in the running direction of the sheet of corrugated cardboard with the conveyor belt running over an adjustable tension roller. 
     According to one embodiment form of the invention, the possibility exists that all of the layers of the sheet of corrugated cardboard can be affected by the compression elements acting on the conveyer belt. Alternatively, it is also feasible, for example, with three layers of the sheet of corrugated cardboard, that the compression elements acting on the conveyor belt initially affect only two layers of the sheet of corrugated cardboard and that the third layer be added to the sheet of corrugated cardboard behind the second deflection roller. This third layer can, for example, be transported by a feeder roller. 
     In order to achieve a more rapid gluing, heatable compression elements can be provided in front of the feeder roller. 
     A particularly simple embodiment of the invention results when the heating device is designed with an upper and a lower intake roller in the initial area of the heating plates. In this case, the upper intake roller can also serve as the first deflection roller for the conveyor belt. 
     In a further refinement of the invention, the feeder roller can also be designed to be heatable. 
     These and other objects, advantages, and features of the invention will be apparent from the following description of the preferred embodiments, considered along with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side view of a first embodiment of the invention. 
     FIG. 2 is a schematic side view of an alternative embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Illustrated in FIG. 1 is a heating device 1 for a corrugated cardboard facility. Heating device 1 consists of several heating plates 3 arranged sequentially in the advancing direction of the sheet of corrugated cardboard 2 and arranged above them, compression elements 4 acting on the sheet of corrugated cardboard 2. The sheet of corrugated cardboard 2 can consist of several layers, for example, a one-sided sheet of corrugated cardboard &#34;a&#34;, another one-sided sheet of corrugated cardboard &#34;b&#34; and a cover sheet &#34;c&#34;. 
     The compression elements 4 can be of any desired design, for example, a pressure hood, weighted rollers, or pneumatically charged compression units. 
     The sheet of corrugated cardboard 2 runs from a starting area &#34;A&#34; of the heating plates 3 to a tractor station 30 in the end area, which undertakes the cooling of the glued sheet of corrugated cardboard 2 by way of conveyor bands, rollers 11&#39; and 11&#34; as well as 12&#39; and 12&#34;, tension rollers 13&#39; and 13&#34; as well as compression elements 4, and furthermore serves to transport the sheet and to compensate for the high friction losses, especially in the case of a beltless heating section. 
     According to the invention, an intake belt &#34;E&#34; is positioned in the starting area &#34;A&#34; of the heating plates 3 between at least a part of the sheet of corrugated cardboard 2 and at least one compression element, in this case two such elements 4.1 and 4.2. This intake belt &#34;E&#34; can be designed as a conveyor belt 10 running over at least two physically separated deflection rollers 11 and 12. This conveyor belt 10 can be heated, for example, by way of deflection rollers 11 and 12. 
     In the embodiment of the invention shown in FIG. 1, the conveyor belt 10 is acted on by at least two compression elements, compression elements 4.1 and 4.2 arranged sequentially in the running direction of the sheet of corrugated cardboard. 
     As can be seen in FIG. 1, an upper intake roller &#34;O&#34; and a lower intake roller &#34;U&#34; are present in the starting area &#34;A&#34;. Here it is possible that the upper intake roller &#34;O&#34; also forms the first deflection roller &#34;11&#34; for the conveyor belt &#34;10&#34;. 
     As indicated in broken outline in FIG. 1, it is possible to vary the distance between the two deflection rollers 11 and 12, for example, in that the rear deflection roller 12 is designed to be displaceable in the running direction of the sheet of corrugated cardboard 2. Here adjustable tension roller 13 is especially advantageous, whereby assurance is given that when the separation of the two deflection rollers is changed, the conveyor belt 10 always remains tautly tensioned. 
     In the embodiment of the invention according to FIG. 1, all three layers (&#34;a&#34;, &#34;b&#34; and &#34;c&#34;) of the sheet of corrugated cardboard 2 are acted upon by the conveyor belt 10 and the two compression elements 4.1 and 4.2 in the starting area A. 
     According to FIG. 2, it is also possible that only two layers, namely &#34;b&#34; and &#34;c&#34;, are acted upon by the conveyor belt &#34;10&#34;, which itself again runs over two deflection rollers 11 and 12. The third layer &#34;a&#34; is introduced via a feeder roller 20 behind the second deflection roller 12. Accordingly, a complete sheet of corrugated cardboard 2 is formed, which is in turn acted upon by the aforesaid compression elements 4, and runs over the surface of the heating plates 3. At least one heatable compression element 25 can be provided between the deflection roller 12 and the feeder roller 20. 
     By virtue of the present invention, assurance is given in a simple manner that the layers (&#34;a&#34;, &#34;b&#34; and &#34;c&#34;) to be glued are so joined together that an adequately stiff sheet of corrugated cardboard 2 is formed, which can be automatically threaded into the corresponding heating section with the heating plates 3. 
     The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit the scope of the invention. Various other embodiments and modifications to these preferred embodiments may be made by those skilled in the art without departing from the scope of the following claims.