Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-05-11
2001-04-17
Gray, Linda (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S289000, C156S291000, C156S301000, C053S239000, C053S287000, C053S401000, C053S416000, C053S454000, C053S467000, C053S473000, C053S477000, C053S560000, C053S546000, C053S547000, C053S548000
Reexamination Certificate
active
06217697
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for producing and coating melt portions, in particular melt adhesive portions, in which the melt is deposited in portions onto an endlessly circulating, horizontal conveyor belt. A first coating material layer is fed onto the surface of the upper end of the belt of the conveyor belt and a second coating material layer partly is applied onto the melt portions deposited on the first coating material layer and partly covering the surface of the melt portions. The present invention is also directed to a system and a device for the application of a melt in defined melt portions for the system.
BACKGROUND OF THE INVENTION
A system for the coating of melt adhesive portions is known from the German patent specification DE 93 18 554 U1. The system disclosed in this specification exhibits an endless circulating horizontal conveyor belt that is coated with a powdery coating material at the feed side. Then, a melt adhesive is applied in defined melt adhesive portions onto the moving conveyor belt. In an additional work station, a powdery coating material layer is applied onto the surface of the melt adhesive portions from above. Then, the melt adhesive portions that are coated on both sides with the coating material pass through a heating station that liquefies the powder of the coating material and that causes an even coating of the melt adhesive portion. A cooling area is attached to the heating station, in which the coated melt adhesive portions are cooled down. After having passed the cooling area, the melt adhesive portions are removed from the conveyor belt and packed in larger units.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method as well as a system of the above-mentioned kind that guarantees a faster and enhanced production and coating of melt adhesive portions.
This object is accomplished in that two sheet strips are continuously fed as coating material layers, the material properties of which are adjusted to the melt regarding chemical tolerance, and that the thickness of the melt portions imbedded between the sheet strips is calibrated in thickness, the melt portions are cooled, the sheet strips are connected to each other by closely encompassing each melt portion, and the sheet strips are cut lengthwise and crosswise to the conveying direction of the melt portions such that the melt portions become isolated. A smooth coating of the melt portion that can be easily handled is already achieved by providing the sheet strips without providing the heating station, as is provided in the related prior art, with the result that the expenditure of energy and thus also costs for the method of the present invention are reduced. The calibration of the thickness of the melt portions results in a more even and more defined cooling so that—compared with the related prior art—an improved cooling behavior is achieved. The sheet strips can be connected in the transition regions between the adjacent melt portions either before or after separating the sheet strips and the resulting isolation of the melt portions. The method according to the invention can be used for all molten masses, but it is particularly well suited for melt adhesives, the strongly adhesive surface of which has to be coated for easier further handling. Due to the chemical tolerance of the sheet strips with the melt, the melt is not impaired by the sheet material.
In one embodiment of the invention, the melt is prepared to have a specified viscosity at a specified temperature and is then applied step by step on the conveyor belt in equal portions, thus achieving even and consistent portioning. In addition, by preparing the melt, it is well adapted to the following cooling of the melt portions on the conveyor belt.
In a further embodiment of the invention, the melt portions are inserted into appropriate matrix spaces of a grid mask that is assigned to the conveyor belt and which travels with the latter and is disposed underneath the lower sheet strip. In this instance, the volume of the melt portion is adjusted to the free volume of each matrix space such that the molten mass overflows over the rims of each matrix space. The thickness of the calibrated melt portions is also greater than the height of the grid mask. By overflowing over the rims of each matrix space, the molten mass itself forms the connection between the two sheet strips forming the top and the bottom covering layers, because it adheres to the two sheet strips. This embodiment is particularly advantageous for melt adhesives having a strong adhesive surface. Contrary to other embodiments of the present invention, welding or gluing the sheet strips may be avoided in this embodiment. The molten mass overflowing over the rims has only a minor thickness so that the two sheet strips are only connected along the rims in an extremely small distance. Due to the grid mask, it is possible to achieve an individual shaping of the melt portions according to the form of the matrix spaces.
In another embodiment of the invention, before feeding of the sheet strips to the conveyor belt, a separating layer is inserted or provided between the underside of the first sheet strip resting on the conveyor belt or the grid mask and the surface of the conveyor belt or the grid mask. This prevents the sheet strip from adhering to the surface of the conveyor belt or the grid mask and causing damages when the melt portions are loosened.
In another embodiment of the invention, an additional separating layer is inserted or provided between the surface of the second sheet strip that touches an upper conveyor belt during calibration and cooling, and the belt surface of the conveyor belt. This separating layer also serves to facilitate an easy detachment of the sheet strip from the surface of the top belt after passing the cooling region.
In another embodiment of the invention, a water spray forms each of the separating layers. In addition to serving as a separator, water also has an additional cooling function in that the sheet strips touching the melt portions are cooled by the water layer between the respective belt surface and the assigned sheet strip.
For the system, the object according to the invention is accomplished in that the conveyor belt is part of a twin belt cooler used for cooling and that a storage roll equipped with a removable sheet strip is assigned to the conveyor belt and to the upper endless circulating belt of the twin belt cooler such that the sheet strips travel with the two belts at the end of the belts that face each other. A significant advantage using a twin belt cooler is that a calibration of the melt portions is achieved in its thickness, which makes a particularly even and defined cooling of the melt portions possible.
In another embodiment of the invention, the melt temperature of the sheet strip is lower than the processing temperature of the melt. As soon as the melt portions including the coating by means of the sheets are fed into a melt bath, the sheets melt without any residues that could impair the melt bath. Thus, there is no packaging refuse.
In another embodiment of the invention, a longitudinal cutting assembly and a transverse cutting assembly are assigned to the conveying path of the melt portions in the conveying direction behind the twin belt cooler. Thus, it is possible to separate the different rows of melt portions by isolating the respective melt portions.
In another embodiment of the invention, a matrix-shaped grid mask that can travel with the conveyor belt is assigned to the conveyor belt, which grid mask covers at least a major part of the belt surface and at least the length of the conveying end of the belt. The individual matrix spaces of the grid mask border the melt portions on all sides, wherein the melt portions are given an individual shape. The grid mask can either be carried along as a separate net strip with the conveyor belt or it can be firmly connected with the surface of the conveyor belt, thus also resulting in the conveyor belt bei
Baumann Warnfried
Kleinhans Matthias
Winter Jurgen
Burns Doane Swecker & Mathis L.L.P.
Gray Linda
Santrade Ltd.
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