Welding device for producing tubular bodies

Abstract

The invention relates to a welding device (1) for producing tubular bodies by the edge-side welding of two substrate edges (2, 3), in particular two laminate edges, said welding device having a continuous, circulating first contact belt (5) for coming into contact with the substrate (4), and an energy source (12, 13) for providing welding energy. According to the invention, the first contact belt (5) has a seamless polyimide contact surface (35) for coming into contact with the substrate (4).

Claims

1. Welding device (1) for producing tubular bodies by edge-side welding of two substrate edges (2, 3), having an endless, circulating, first contact belt (5) for coming into contact with the substrate (4), having an energy source (12, 13) for providing welding energy, and having means for conveying the substrate (4) along the energy source (12, 13) while the substrate edges (2, 3) are welded, characterized in that the first contact belt (5) has a seamless polyimide contact surface (35) for coming into contact with the substrate (4).

2. Device according to claim 1, characterized in that a second endless, circulating contact belt (6) is provided, which has a seamless polyimide contact surface (36) for coming into contact with the substrate.

3. Device according to claim 2, characterized in that the contact belts (5, 6) are arranged such that the substrate (4) can be clamped, between them, and transported together with the contact belts (5, 6).

4. Device according to claim 2, characterized in that the entire first and/or second contact belt (5 and 6), is made entirely of polyimide.

5. Device according to claim 2, characterized in that the polyimide contact surface (35, 36) of the first and/or second contact belt (5 or 6) is applied to a metal.

6. Device according to claim 5, characterized in that the polyimide of the polyimide contact surface (35, 36) is applied directly to the metal with no interposed adhesive layer, optionally over a primer.

7. Device according to claim 2, characterized in that the polyimide contact surface (35, 36) of the first and/or second contact belt (5 and 6) is roughened, with a roughness R.sub.a between 1 nm and 5 μm.

8. Device according to claim 2, characterized in that at least 50 percent by weight of the polyimide of the polyimide contact surface (35, 36) of the first and/or second contact belt (5 and 6) is an aromatic polyimide.

9. Device according to claim 2, characterized in that the polyimide contact surface (35, 36) of the first and/or second contact belt (5 and 6) is produced by application of a solution containing tetracarboxylic acid anhydrides and diamides and subsequent polycondensation of said solution, at a temperature above 300° C. to yield polyimide.

10. Device according to claim 2, characterized in that the first and/or second contact belt (5 and 6) is produced as a single part, without butt joints, made of polyimide.

11. Device according to claim 2, characterized in that the polyimide contact surface (35, 36) of the first and/or second contact belt (5 and 6) has a layer thickness between 5 and 100 μm.

12. Device according to claim 2 characterized in that the first and/or second endless contact belt has a length greater than 1 m.

13. Device according to claim 2 characterized in that the first and/or second endless contact belt has a width between 2 mm and 50 mm.

14. Use of a welding device (1) according to claim 1 having a substrate (4) that comprises at least one polymer layer, for producing tubular bodies by edge-side welding of two substrate edges (2, 3).

15. Method for producing tubular bodies in which a substrate (4) having two substrate edges (2, 3) is welded on the edge side by a welding device (1), wherein a first endless contact belt (5) is brought into contact with the substrate and wherein the substrate (4) welded by means of an energy source (12, 13) past which the substrate is conveyed during welding, characterized in that the first contact belt (5) comes into contact with the substrate (4), with a seamless polyimide contact surface (35, 36).

16. Method according to claim 15, characterized in that the energy source (12, 13) heats a metal layer in the substrate (4).

17. Method according to claim 15, characterized in that the energy source (12, 13) heats a metal layer in the first contact belt (5) preferably by induction.

Description

(1) In the drawing:

(2) FIG. 1 is a schematic representation of a welding device configured as a high frequency welding apparatus for producing tubular bodes for packaging tubes from a substrate,

(3) FIG. 2 is a sectional view of a welding device configured as a high frequency welding apparatus in the welding area, and

(4) FIG. 3 is a welding device with butted substrate edges.

(5) In the figures, the same elements and elements with the same function are identified with the same reference numerals.

(6) FIG. 1 shows important components of a welding apparatus 1 for edge-welding two substrate edges 2, 3 of a substrate 4 shown in FIG. 2. Substrate edges 2 and 3 are welded together to form a tubular body for a packaging tube.

(7) Welding device 1 comprises a first endless, driven circulating contact belt 5, embodied here as a welding belt with a steel belt coated with polyimide, and a second endless, driven circulating contact belt 6 running partially parallel thereto. Second contact belt 6, the lower belt in the figure, is constructed in the form of steel belt coated with polyimide, forming an “inner welding belt”, of which the right section 7 in the drawing plane protrudes into the tubular body to that is to be manufactured—not shown—whereas first contact belt 5 runs along the outer surface. First contact belt 5 is guided over a number of rollers and a first electric motor drive unit is provided for driving first contact belt 5 in the circumferential direction. In addition, a first clamping device 9 is assigned to first contact belt 5 to ensure that first contact belt 5 is clamped according to defined parameters. A second, similarly constructed clamping device 10 is assigned to second contact belt 6. A second electric motor drive unit 11 is also provided.

(8) Overall, device 1 comprises energy sources 12, 13 (first power source 12, second power source 13), each of which has the form of a high-frequency generator and is designed in a manner known per se and can cooperate with the respective contact belt 5, 6. In an area between the opposing power sources 12, 13, the substrate edges—not shown—are welded to each other to form a longitudinal weld seam. A cooling zone 25 formed by a chilled beam for rapidly cooling the joined substrate edges 2, 3 is provided after energy sources 12, 13. Downstream of cooling zone 25, there are cutting means—not shown—for cutting the endless tubular pipe into individual tubular bodies.

(9) First contact belt 5 has been coated with polyimide, in such manner that a contact surface 35 for contacting the substrate consists of polyimide. The coating was prepared by converting aromatic tetracarboxylic acid anhydrides, in the form of pyromellitic acid dianhydride (1,2,4,5-benzenetetracarboxylic acid dianhydride) and aromatic diamines, in the form of 4,4′-diaminodiphenyl ether in an anhydrous polar solvent, in the form of N-methyl-2-pyrrolidone (NMP), into a polyamidocarboxylic acid, and this solution was applied as a surface coating to the steel belt. The conversion to polyimide was effected by applying a temperature above 360° C., wherein was driven off and the solvent evaporated.

(10) FIG. 2 serves merely to illustrate the mode of operation of welding apparatus 1. FIG. 2 shows a schematic sectional view through the weld zone of FIG. 1.

(11) As is shown in FIG. 2, each power source 12, 13 comprises a coil 19, 20 and a ferrite core 21, 22, an insulating layer 23, 24 being arranged between each coil 19, 20 and the associated contact belt 5, 6.

(12) In the present example, two coils 19, 20 are shown. In general, one coil 19 or 20 would suffice.

(13) FIG. 3 shows a welding device 1 in which two butt joined substrate edges 2, 3, which are sandwich clamped by two welding belts 5, 6 circulating at slightly different speeds. Otherwise, the welding device 1 of FIG. 3 corresponds to the welding device 1 shown in FIG. 2.