EP2084938B2 - Device for laying down a thin metal wire on a surface - Google Patents

Abstract

A device for laying a thin metal wire taken from a coil of wire stock onto a surface, in particular onto the surface of a sheet, using a presser. The device includes a mechanism exerting mechanical tension in a region of the wire that lies between the rotary coil of wire stock and the presser, and a wire-guiding device provided in the region. The wire-guiding device includes a tensioning device that acts directly on the wire taken off the coil of wire stock. That makes it possible effectively and appreciably to compensate for changes in relative speeds at which the wire and the sheet progress.

Description

The invention relates to a device for depositing a thin metal wire on a surface and in particular on the surface of a sheet, which has the characteristics of the preamble of claim 1. It relates in particular to the preparation of sheets for laminated windows heated by heat. son.

By wire-heated laminated panes is meant in particular panes for windows and the like which have a multilayer structure consisting of at least one rigid pane (of glass or of synthetic material) and of a layer or sheet of synthetic material which adheres at its surface, several resistance threads deposited by machine being arranged in the boundary surface between the rigid pane and the layer or sheet of synthetic material. These wires are generally electrically connected in parallel and are supplied with heating voltage using at least two collectors. The collectors generally extend along each outer edge of the window. In general, the sheets equipped with wires are enclosed between two rigid panes.

European patent EP 0 443 691 describes a device of this type, for depositing these threads on sheets. It comprises a mobile laying device to which the threads which come from a spool are brought by means of an eyelet guide and two toothed wheels which mesh with one another. The document FROM 20 43 746 discloses such a thread laying device which has a thread guide tube disposed between the thread reserve spool and the laying location.

The document DE 41 01 984 A1 describes a similar device which has a simple guide between the wire reserve spool and the toothed wheels. A reduction transmission is provided between the toothed wheels and the constantly driven roller, which pushes the threads back onto the sheet. The cogwheels turn slightly slower than the push roller. It is thus obtained that the corrugated wire always remains under a low tensile stress on the path which extends between the toothed wheels and the push roller. This prevents uncontrolled movements of the deposited wire.

In the document DE 42 01 620 A1 , for such a device provided for laying wires in a straight line, which therefore does not have any means for undulating the wires, an electric brake is provided on the reserve spool of wire. The latter must maintain constant tension in the unwound thread. On their path between the spool and the push roller, the wires pass over deflection and guide rollers without braking function mounted on ball bearings.

Usually, the sheets which are to be provided with the threads in these known devices are fixed on rotary drums which allow the sheet substrate to be advanced more or less continuously below the thread laying devices. Depending on the local curve provided for the yarns, the rotational displacement of the drum can also be controlled at different speeds, so that braking or acceleration transitions are obtained.

When such a device is provided with a braking system and mechanisms for undulating the wire to be deposited, oscillations which result from the deformation of the wire and the relative inertia of the reserve wire spool mutually influence each other. and therefore lead to the formation of irregular undulations.

In addition, the ratio between the speed of rotation of the wire reserve spool and the speed of rotation of the drum on which the sheet of PVB is fixed which is to be being endowed with wires is not constant. As a result, the tensile force under which the wire is withdrawn from the spool is not constant. There is therefore a need to keep the thread tension constant.

The problem at the basis of the invention is therefore, for a device of the type indicated at the beginning, to further improve the guiding of the wire before it is placed on the sheet.

According to the invention, this problem is solved with the characteristics of claim 1. This loop allows a fairly significant compensation of the length, of several centimeters, in the part of the wire which is located at all times between the spool 6 of reserve of. wire and the push roll 8. The features of the dependent claims give advantageous developments of the invention.

With the insertion of a clamping device or a clamping element in the yarn path between the braked or unbraked yarn reserve spool, the desired improvement is achieved. The clamping element ensures a constant tension of the wire before the actual laying operation and possibly before its corrugation. This greatly reduces the influence of a relatively slow rotation of the wire reserve spool, at least when it is completely full, on the subsequent corrugation and the laying of the wire.

In other words, the wire is passed through a "buffer zone" (for example provided with guide rollers) to thereby compensate for the change in the tensile force at the exit of the buffer zone by an appropriate compensation of the force as well. than by compensating for the length of the wire inside the buffer zone.

This solution according to the invention has not been proposed so far by the state of the art, because fundamentally, with the known electric brake, the problem of wire oscillations could be considered solved. The solution according to the document FROM 20 43 746 mentioned above, which consists in passing the wire through a tube, could not give any indication in this regard. The document does not disclose that it envisages that this guide tube exerts a braking effect. On the contrary, it is assumed that the wire slides inside this tube with little friction.

Concrete possibilities of achieving the regularization of the thread tension in the relevant compensating part include passive compensation by gravity-actuated mechanisms and active compensation by means of elastic elements, pneumatic cylinders or regulating motors.

A device for laying wires thus equipped is suitable both for laying wires in a conventional manner in a uniform manner, with or without corrugation, in regular paths, as well as for laying the wire following the paths recently proposed in any curves, in divergent paths. , in non-circular paths with variable radius, with local increases and / or decreases in the density of thread laying, etc. the clamping device according to the invention deploys its advantages in particular for the forms of laying mentioned last, because in this case it is often necessary to control the sheet support at variable speeds. It is even possible (in a manner known per se) to have to carry out reversals of the direction of movement.

Other details and advantages of the subject of the invention emerge from the drawing of an exemplary embodiment of a thread laying device according to the present invention and from its description given below.

• la figure 1 représente une vue globale du dispositif selon l'invention, avec un tambour de fixation du substrat en feuilles et un unique dispositif de pose de fil et
• la figure 2 représente une vue d'un dispositif de compensation de la tension du fil.

In simplified representations and not to scale:

• the figure 1 shows an overall view of the device according to the invention, with a drum for fixing the substrate in sheets and a single device for laying the wire and
• the figure 2 shows a view of a yarn tension compensation device.

The device according to the invention shown in figure 1 comprises a drum 1 which, thanks to a drive 2, forms a movable laying surface for thermoplastic sheets (in particular made of polyvinyl butyral). The sheets 3 provided with wires are generally placed between two rigid panes of glass and / or synthetic material and connect the latter by adhesion over their entire surface, so that a laminated glazing is thus obtained which can be heated by means of sons.

The cylindrical drum 1 advantageously has a large diameter and a large circumference, so that several sheets 3 can be placed on its cylindrical wall. We can see here two sheets 3 of the same size. They are fixed to the casing surface of the drum preferably by depression or pressure difference. For this purpose, the casing surface is provided in known manner with a large number of bores through which air is sucked. Atmospheric pressure pushes the leaves back onto the husk surface.

Above the drum 1 is arranged a device 4 for laying the thread (also called the laying head). Thanks to a drive not shown in detail, this device can be moved back and forth parallel to the axis of rotation of the drum (and therefore parallel to the direction of examination of the figure) along a guide rectilinear 5. A wire 7 is extracted from a reserve spool 6 of wire and is finally laid with the aid of a push roller 8 (preferably heatable) on the sheet 3 or incorporated into the surface of the latter.

In the figure 1 , it can be seen that the thread is deposited continuously in successive loops, even on the edges of the sheet 3. It is obvious that these loops must be cut after the laying of the thread and before the sheet 3 is removed from the drum 1 It is also evident that on a drum 1 it is possible to use several thread laying devices located next to each other and synchronized.

The wire reserve spool 6 can in a known manner be equipped with an adjustable brake, for example electric. The push roller 8 is preferably elastically prestressed against the casing surface of the drum 1 and rolls without its own drive on the sheet 3.

On the path between the wire reserve spool 6 and the push roller 8, the wire 7 passes through a guide device generally designated by 9 in the figure 1 . It serves on the one hand and in a known manner to impart a zigzag pattern or an undulation in the thread which passes through it. It is known that laying the wires 7 in a zigzag way minimizes their visibility in the finished laminated glazing (see in this connection the literature mentioned at the beginning).

In addition, the guide device 9 has for the wire 7 which passes through it another clamping device whose figure 2 gives more details.

For the sake of simplicity, this figure 2 represents in the same plane the whole of the guide device 9 and the path of the wire 7 between the coil 6 wire reserve and the push roller 8, because it is only a question of explaining the operation and not of showing an actual embodiment.

Similar to the figure 1 , we can see a piece of a sheet 3 placed on the drum and the thread 7 which is unwound from the thread reserve spool 6 (being damped by the brake 6B known per se) and which is fed to the push roller 8 by the guide device 9, as indicated by several arrows in the path of the wire. On both sides of the push roller 9, the arrows show the instantaneous direction of advance of the casing surface of the drum and the sheet 3. When the push roller and the whole thread laying device are made from suitably, the direction of rotation of the drum can also be reversed to lay yarns following more complicated paths and / or, when the drum is stationary, a yarn can also be deposited by simply moving the laying device sideways. wire.

Certain lines of thread 7 'have already been laid on the sheet 3 by previous rotation of the drum 1 and the push roller 8 must then be located so as to be able to lay another line of thread 7' to its right. In an embodiment known per se, the pushing roller 8 has a flat and convex pushing surface. Wire 7 passes over the line of its top. In this way, the thread 7 is driven into the surface of the sheet 3 without the side edges of the push roller 8 entering the sheet 3.

The guide device 9 comprises in a manner known per se two toothed wheels 10 which mesh with one another and which give the wire 7 guided between them the desired undulation immediately upstream of the push roller 8. To simplify , we have not shown the corrugation of the wires placed on the sheet 3. As regards the relative speed between the toothed wheels and the push roller, reference will be made to the state of the art described above.

According to the invention, starting from the wire reserve spool 6, and before entering between the toothed wheels 10, the wire 7 passes through a clamping device generally designated by 11. In its embodiment shown here, the latter comprises two fixed guide rollers 12 and between the latter, a movable and elastically prestressed clamping roller 13. The latter is rotatably mounted in the clamping device 11 and / or in the guide device 9 on an oscillating or pivoting lever 14 which itself is pre-stressed by means of a thrust spring 15. There is shown in broken lines. various possible positions for the pivoting lever 14 to exit from the central position shown in solid lines.

Overall, the invention makes it possible to obtain a reaction which is as sensitive and quick as possible of the clamping device 11 to variations in the instantaneous tension of the thread. A particularly low mass of the moving parts of the clamping device and low friction in all mounting and possibly sliding locations can make a particularly interesting contribution in this respect.

It can be seen that between the two guide rollers 10, the wire 7 forms a U-shaped loop, the depth of which in relation to the guide rollers 12 is defined by the effective position of the movable clamping roller 13 which is kept under stress. by the spring 15. This loop allows a fairly significant compensation of the length, of several centimeters, in the part of the wire which is located at all times between the wire reserve spool 6 and the push roller 8.

If it is necessary to compensate for an even greater variation in length, the clamping roller 13 (elastically prestressed) can also be guided in a straight line in an easily accessible sliding guide, in opposition to an elastic force or the like, instead of the 'be by the pivoting lever shown, so as to be able to extend over a greater length without angular offset.

Overall, it is possible to compensate very simply and with low inertia for variations in the speed of rotation of the drum 1 which cause an acceleration or a slowing down of the rotation of the push roller 8 and therefore in general also an irregular consumption of yarn. In particular, the mass of the wire reserve spool 6, which varies greatly as a function of the wire reserve still present, and the relative inertia of the brake 6B are not involved in this compensation, which can therefore react very sensitive.

After the guide roller 12 located downstream in the direction of advance of the wire, the wire 7 still passes between two guide rollers 16 which make it enter exactly in the middle between the toothed wheels 10. The latter can obviously also be replaced by the sliding guide or even be completely eliminated if, starting from the second guide roller 12, the sufficiently exact introduction of the wire 7 between the toothed wheels 10 is guaranteed.

Further, instead of the pushing coil spring 15 shown here schematically, other adjusting means of the clamping roller 13 can also be used, for example an air spring, a pneumatic, electric or similar adjustment drive.

The clamping device may optionally also include a measurement unit (not shown here) which determines the effective tension of the thread which then imposes the clamping force required at all times on an associated adjustment drive. Such a measurement unit could for example detect the force exerted on its bearing by one of the return rollers 12, which force increases when the drum 1 accelerates and decreases when the drum 1 slows down. When the force on the wire is reduced, then additional tightening will have to be exerted, while if the tensile force increases, the tension may be reduced.

Claims (11)

1. A device for laying onto a surface a thin metal wire (7) taken from a coil (6) of wire stock, in particular onto the surface of a sheet (3), using a presser (8), which device has means for exerting mechanical tension in that part of the wire (7) that lies between the coil (6) of wire stock and the presser, and a wire-guiding device (9) provided in this region, characterized in that the wire-guiding device (9) comprises a tensioning device (11) which acts directly on the wire (7) taken off the coil (6) of wire stock so as to obtain a reaction, to variations of the instantaneous tension of the wire, the wire (7) being guided in the region of the tensioning device (11) over a portion of variable length, the variable length of the portion which can be defined using at least one mobile tensioning roll (13), and in that the wire (7) is guided in the tensioning device (11) by, in turn, a first turn roll (12), the mobile tensioning roll (13) and another turn roll (12), so as to form a U-shaped loop, the depth of which with respect to the turn rolls (12) is defined by the effective position of the mobile tensioning roll (13).
2. The device as claimed in one of the preceding claims, characterized in that the tensioning roll (13) is mounted on an elastically urged pivoting lever (14).
3. The device as claimed in one of the preceding claims, characterized in that the wire is guided in the tensioning device (11) by a mobile and preferably curved sliding rail.
4. The device as claimed in claim 3, characterized in that the tensioning roll (13) is mounted in a sliding guide.
5. The device as claimed in one of the preceding claims, characterized in that the tensioning device (11) comprises at least one spring (15) and/or a drive mechanism that is feedback controlled.
6. The device as claimed in one of the preceding claims, characterized in that the tensioning device (11) comprises a device for measuring the tension in the wire at any moment.
7. The device as claimed in one of the preceding claims, characterized in that a brake (6B), the braking force of which is preferably feedback controlled, is provided, so as to damp the rotational movement of the coil (6) of wire stock.
8. The device as claimed in one of the preceding claims, characterized in that means (10) are also provided for mechanically corrugating the wire (7) between the tensioning device (11) and the presser (8).
9. The device as claimed in one of the preceding claims, characterized in that it comprises several laying devices as claimed in one of the preceding claims.
10. The device as claimed in one of the preceding claims, characterized in that the sheet (3) that is to be equipped with the wire (7) is fixed to a flat or curved laying surface, and in that the wire is laid down by relative movement of the presser (8) and/or of the sheet (3), one relative to the other.
11. The device as claimed in one of the preceding claims, characterized in that an element for supporting the sheet (3) can be moved reversibly with respect to the presser (8).

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