DEVICE FOR HEAT-TREATING SHEET METAL STRIPS

Abstract

A device is described for heat-treating sheet metal strips (6) having at least one radiator pipe unit (1), which has three pipes located in a common axial plane parallel to the sheet-metal strip (6), namely one middle pipe (2) attachable to a burner and two outer pipes (3) connected at both ends to the middle pipe (2) via pipe elbows (4), and having a bearing pin (9), connected to the two pipe elbows (4) between the middle pipe (2) on one side and the two outer pipes (3) on the other side, on the side of the radiator pipe unit opposite to the burner. To be able to take the occurring thermal expansions in the area of the pipe elbows (4) into consideration, it is proposed that the bearing pin (9) be arranged on a bridge (10), which bridges a gusset (11) between the two pipe elbows (4), having two sections (12) which extend on both sides of the axis of the middle pipe (2) and are inclined at an acute angle to the axis of the middle pipe (2).

Description

FIELD OF THE INVENTION

The invention relates to a device for heat-treating sheet metal strips having at least one radiator pipe unit, which has three pipes located in a common axial plane parallel to the sheet-metal strip, namely one middle pipe connectable to a burner and two outer pipes connected at both ends to the middle pipe via pipe elbows, and having a bearing pin, which is connected to the two pipe elbows between the middle pipe on one side and the two outer pipes on the other side, on the side of the radiator pipe unit opposite to the burner.

DESCRIPTION OF THE PRIOR ART

For heat-treating sheet metal strips (DE 20 2008 009 065 U1), providing radiator pipe units which can be heated with the aid of burners is known, which have two outer pipes originating from a middle pipe connected to the burner, located parallel to the middle pipe in a common axial plane, so that with the aid of the outer pipes connected terminally via pipe elbows to the middle pipe, a partial stream of the hot exhaust gases of the burner flowing in the middle pipe can be guided in the circuit in each case. The sheet-metal strip to be treated, which is conveyed parallel to the common axial plane of the pipes of the radiator pipe unit having a feed direction extending transversely to the pipe axes, is heated via the thermal radiation emitted from the pipes of the radiator pipe unit. Because of the high temperatures of the radiator pipes, the mounting of the radiator pipe unit is to be designed so that the thermal expansions of the pipes in the axial direction are taken into consideration. For this purpose, the middle pipe is axially fixed between the burner and outer pipes in a pivot bearing, while at the opposite end of the radiator pipe unit, a typically hollow bearing pin, which is welded onto the two pipe elbows connecting the ends of the middle pipe to the ends of the outer pipes, is supported so it is axially displaceable in a support. However, because thermal expansions occur not only in the direction of the pipe axes, but rather also in the area of the pipe elbows transversely thereto, a significant strain of the weld seams results between the bearing pin and the pipe elbows, which results in the danger of cracking, in particular because the strength of the steels used is reduced because of the high temperature strain.

SUMMARY OF THE INVENTION

The invention is therefore based on the object of implementing a device of the type mentioned at the beginning for heat-treating sheet metal strips in such a manner that the thermal expansions in the area of the pipe elbows connecting the metal pipe to the outer pipes can be taken into consideration when attaching the bearing pin to these pipe elbows.

The invention achieves the stated object in that the bearing pin is arranged on a bridge, which bridges a gusset between the two pipe elbows, having two sections extending on both sides of the axis of the middle pipe and inclined at an acute angle to the axis of the middle pipe.

Through the bridge which bridges the gusset area between the two pipe elbows, an advantageous condition is provided for accommodating thermal expansions in the area of the pipe elbows, so that the connection between the bearing pin and the bridge can be kept substantially tension-free. In addition, a direct heat transfer from the pipe elbows to the bearing pin is suppressed by the bridge, whereby the thermal strain of the bearing pin is reduced. In order that thermal expansions in the area of the two pipe elbows can advantageously be accommodated via the bridge, the bridge has two sections extending on both sides of the axis of the middle pipe and inclined at an acute angle to the axis of the middle pipe, so that through an angle change of the sections of the bridge inclined to one another at an obtuse angle, because of bending strains occurring in the elastic range, a sufficient length compensation is possible upon a thermal expansion of the pipe elbows.

Particularly simple design conditions result in this context if the bridge is implemented as symmetrical to the axis of the metal pipe, because in this case the coaxial mounting of the radiator unit to the middle pipe can be ensured in a simple manner.

BRIEF DESCRIPTION OF THE DRAWING

The object of the invention is shown as an example in the drawing. In the figures

FIG. 1 shows a device according to the invention for heat-treating sheet metal strips in detail in the area of the radiator pipe unit in a simplified side view and

FIG. 2 shows the radiator pipe unit in detail in the area of the bearing pin in a partially cutaway side view in a larger scale.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As can be inferred from FIG. 1, the device for heat-treating sheet metal strips has at least one radiator pipe unit 1, which comprises a middle pipe 2 and two parallel outer pipes 3 located in a common axial plane with the middle pipe 2. The outer pipes 3 each have a flow connection to the middle pipe 2 via terminal pipe elbows 4. The hot exhaust gases flowing from a burner, which is attached to an extension 5 of the middle pipe 2, into the middle pipe 2 are therefore partially guided in the circuit via the two outer pipes 3. A sheet-metal strip 6, which is indicated by dot-dash lines, and which is guided parallel to the common axial plane of the pipes 2, 3, in a feed direction 7 which extends transversely to the pipe axes, is heated with the aid of the radiant heat emitted from the pipes 2, 3.

The radiator pipe unit 1 is mounted on both sides of the pipes 2 and 3, so that a substantially uniform distribution of the weight load on the two supports results. While the support 8, which accommodates the extension 5 of the middle pipe 2 and is not shown for reasons of clarity, axially fixes the radiator pipe unit 1, the opposing support 8 supports the radiator pipe unit 1 so it is axially displaceable. For this purpose, the radiator pipe unit 1 carries, on the end of the middle pipe 2 opposite to the extension 5, a typically tubular bearing pin 9, which is supported so it is axially displaceable in a corresponding receptacle of the support 8. Because of the high exhaust gas temperatures inside the pipes 2, 3, these pipes are subjected to a corresponding thermal expansion, the axial length compensation thus required being ensured via the bearing pin 9, which is displaceable in the support 8. However, not only the pipes 2, 3, but rather also the pipe elbows 4 are subject to a thermal strain, which causes a thermal expansion of the pipe elbows in the elbow longitudinal direction. In order that these thermal expansions in the area of the pipe elbows 4 can also be taken into consideration, the bearing pin 9 is not fastened directly on the pipe elbow 4, but rather is arranged on a bridge 10, which bridges the gusset area 11 between the two pipe elbows 4. Therefore, thermal expansions of the pipe elbows 4 can be compensated for via this bridge.

According to FIG. 2, the bridge 10 is formed for this purpose by two sections 12, which extend at an acute angle to the axis of the middle pipe 2 and enclose an obtuse angle with one another. If the distance of the weld seams between the sections 12 and the pipe elbows 4 changes because of thermal expansions of the pipe elbows 4, these length changes can be readily compensated for by elastic bending and a change of the angle of the sections 12 connected thereto.

This means that the weld seams between the sections 12 of the bridge 10 and the bearing pin 9 remain substantially free of tensions as a result of the thermal expansion of the pipe elbows 4, which avoids the danger otherwise occurring to the connection of the bearing pin 9 to the pipe elbows 4. In addition, the direct heat transfer from the pipe elbows 4 to the bearing pin 9 is interrupted via the sections 12 of the bridge 10 and therefore a lesser thermal strain of the bearing pin 9 can be expected.

Claims

1. A device for heat-treating sheet metal strips (6) having at least one radiator pipe unit (1), which has three pipes located in a common axial plane parallel to the sheet-metal strip (6), namely one middle pipe (2) attachable to a burner and two outer pipes (3) connected at both ends to the middle pipe (2) via pipe elbows (4), and having a bearing pin (9), connected to the two pipe elbows (4) between the middle pipe (2) on one side and the two outer pipes (3) on the other side, on the side of the radiator pipe unit opposite to the burner, wherein the bearing pin (9) is arranged on a bridge (10), which bridges a gusset (11) between the two pipe elbows (4), having two sections (12) which extend on both sides of the axis of the middle pipe (2) and are inclined at an acute angle to the axis of the middle pipe (2).

2. The device according to claim 1, wherein the bridge (10) is implemented symmetrically to the axis of the middle pipe (2).