Method for forming a closed frame-shaped spacer for an insulating glass pane

A method for forming a closed frame-shaped spacer for an insulating glass pane by applying a paste-like and subsequently hardening strand has at a beginning of the strand a ramp in which the thickness of the strand increases from zero to a nominal thickness. An end of the strand's thickness is complementary to the rising ramp on the same path, overlapping the ramp, decreasing from the target thickness to zero, the surface of the ramp forming an interface between the beginning and the end of the strand. The beginning and end of the strand are pressurized on either side by placing it between a first jaw and a second jaw. The exerting surface of the first jaw has a property enabling the material of the strand which comes into contact with the surface of the first jaw to be removed therefrom by lifting the first jaw from the strand.

DESCRIPTION

Field of the Invention

The invention is based on a method for forming a closed frame-shaped spacer for an insulating glass pane by application of an initially pasty strand which subsequently consolidates, delimited by a lower side, an upper side and two side faces, and which has a nominal thickness between the lower side and the upper side as well as a nominal width between the two side faces, onto a glass plate along the edge of the glass plate in a manner such that at a start of the strand, its thickness comprises a ramp over a section with a predetermined length, wherein the thickness of the strand increases from zero to the nominal thickness. At an end of the strand, said thickness decreases from the nominal thickness to zero in a manner which is complementary to the increasing ramp over the same section, overlapping the ramp, so that the surface of the ramp forms an interface between the start and the end of the strand.

Background of the Invention

A method of this type is known from DE 44 33 749 C2.

The term “lower side” is used to describe that side of the strand which comes into contact with the glass plate. The term “upper side” is used to describe the side of the strand opposite to the lower side. The two side faces connect the upper side and the lower side together.

In the known method, in order to form a thermoplastic spacer, a strand which initially has pasty properties at a temperature which is above ambient temperature is extruded by means of a nozzle and applied to the glass plate in a manner such that the start and end of the strand are not blunt, but are abutted together via an inclined face (ramp) which is formed because, on being discharged from the nozzle at the start, over a section with a predetermined length, the thickness of the strand increases from zero to the nominal thickness of the strand and in complementary manner thereto, at the end of the strand, it is decreased over the same section from the nominal thickness to zero. This can be carried out with the aid of a nozzle with a variable discharge cross section and which also, while it is moved at a predetermined distance to the edge of the glass plate along the edge of the glass plate, can be lifted from the glass plate. Inevitably, this manner of operating produces a joint between the start and end of the strand. This joint is placed under pressure when assembling the insulating glass pane, because it is vitally necessary and usual to compress insulating glass panes, on the one hand in order to obtain the desired nominal thickness for the insulating glass pane, and on the other hand in order to ensure a firm connection which is sealed against the diffusion of water vapour between the spacer and the attached glass plates. During this compression, the two inclined faces at the start and end of the pasty strand are necessarily compressed together and bonded tightly together without taking further action, so that the frame-shaped spacer hermetically seals the interior space of the insulating glass pane, as is the intention. Upon cooling, the initially pasty strand consolidates and forms the intended spacer.

In the prepared insulating glass pane, the position of the interface between the start and the end of the strand on the side face of the strand facing the interior space of the insulating glass pane is still visible as a line running diagonally across this side face. Some people find this displeasing. The line which can be discerned on that side face of the strand which delimits the interior space of the insulating glass pane after it has been assembled marks the interface between the start and end of the strand lying in this section of the edge in this side face.

DE 10 2004 115 218 B3, which is not pre-published, discloses a method by means of which mechanical vibrations are applied to at least that side face of the pasty strand which, after assembling the insulating glass plate, delimits the interior space thereof, in a region which extends to either side of the edge of the interface between the start and the end of the strand, in particular by means of vibrating bodies which are placed in a contact-free manner at the side faces of the strand.

WO 2015/113080 A1 discloses a method for the production of spacers for insulating glass panes, in which a strand formed from thermoplastic material is applied as a spacer to a plate of glass and in which the start and end of the strand are connected together, wherein mutually overlapping ends of the strand are compressed between an inner jaw and an outer jaw. While the inner jaw and the outer jaw are placed against the strand, between them in the region of the connecting point between the start and end of the strand formed in this manner, a depression is produced by means of which, upon subsequent compression of the insulating glass plate to its nominal thickness, pressure equalization may be carried out. The depression for the pressure equalization is still visible after compression of the insulating glass pane to its nominal thickness. A subsequent treatment of this site with mechanical vibrations as taught in DE 10 2004 115 218 B3 is not possible, however, because the visible site is positioned in the insulating glass pane which has already been assembled.

The objective of the present invention is to indicate a manner by means of which a spacer of the type defined above can be produced, in which the position of the butt joint between the start and the end of the strand in the prepared insulating glass pane is more difficult to discern than before.

SUMMARY OF THE INVENTION

This objective is achieved by means of a method with the features of the independent patent claim. The subject matter of the dependent claims pertains to embodiments and further developments of the method in accordance with the invention.

In accordance with the invention, a pasty strand which has been applied to a glass plate in accordance with the method disclosed in DE 44 33 749 C2 in order to form a spacer is post-treated, wherein pressure alone is applied by means of and between a first jaw and a second jaw in a region which extends to either side of the edge of the interface between the start and the end of the strand, wherein at least the surface of the first jaw exerting pressure on the first side face of the strand which delimits the interior space of the insulating glass pane after assembly thereof has a property enabling the material of the strand which comes into contact with the surface of the first jaw to be removed therefrom by lifting the first jaw from the strand. In contrast to what is disclosed in DE 10 2014 115 218 B3, the strand is not post-treated by the application of mechanical vibrations, but rather, pressure jaws which face the side faces of the strand are merely moved towards each other in order to exert pressure on the strand, but in contrast to the teaching of DE 10 2014 115 218 B3, the pressure jaws are not vibrated. By applying pressure, in the side face of the strand which delimits the interior space after assembly of the insulating glass pane, the transition between the start and the end of the strand can be smoothed out in a manner such that the position of the interface between the start and the end of the strand in that side face which delimits the interior space of the insulating glass pane after assembly thereof, can no longer be discerned in the finished insulating glass pane, or is not as discernible as in the prior art. This is made possible because when the method in accordance with the invention is carried out, the insulating glass pane has not yet been assembled. In this regard, it is of no consequence whether the interface between the start and the end of the strand on the second side face of the strand facing outwards in the insulating glass pane and on the upper side and on the lower side of the strand which adhere to both glass panes in the insulating glass pane is still discernible, because these three sides are no longer visible after assembly and sealing of the insulating glass pane and/or after installation of the insulating glass pane in a window frame or door frame.

The method in accordance with the invention may be carried out in a production line for insulating glass panes, after the pasty strand has been applied to a first glass plate and before a second glass plate is pressed onto the frame-shaped strand which is formed thereby in order to complete the insulating glass pane. In this phase of the assembly of the insulating glass pane, the strand is still freely accessible on three sides, namely the first side face, which delimits the interior space of the insulating glass pane after the latter has been assembled, on its opposing second side face and the upper side of the strand applied to the first glass plate, which is subsequently joined to the second glass plate.

In the production line for insulating glass panes, the first glass plate with the frame-shaped strand adhering thereto may be moved away from the working area of the nozzle with which the strand has been extruded and applied to the glass plate to a station in which a tool is provided for post-treatment of the butt joint in the frame-shaped strand. The time taken for the post-treatment of the butt joint may be shorter than the time required for extrusion and application of the strand to the glass plate, so that the cycle time for the production line for the production of the insulating glass plate is not extended by the post-treatment. In general, the post-treatment may also, however, be carried out in the same station of the insulating glass pane production line in which the strand is extruded and applied to the glass plate.

The pressure may be exerted on the side faces of the strand in a variety of manners. In one embodiment of the invention, jaws are used in this regard which not only extend slightly beyond the section of the edge of the interface between the start and end of the strand in the side faces of the strand, but also cover a region of the side faces which extends to either side of the edge of the interface. In this regard, a surface of the jaws acting on the side faces of the strand may be in the shape of a rectangle with the length of its sides being determined by the height of the strand applied to the glass plate and by the length of the ramp measured in the longitudinal direction of the strand which marks the position of the interface between the start and end of the strand.

In another embodiment of the invention, the surface of the jaws which will act on the side faces of the strand are in the shape of a rhombus which is long enough to cover the edge of the interface in the relevant side face of the strand completely or almost completely. In this case, the jaws can be applied to the side faces of the strand in a manner such that the rhombus is essentially delimited by the upper side and the lower side of the strand as well as by two lines parallel to the edge of the interface and the edge of the interface essentially lies in the rhombus. This embodiment of the invention has the advantage that the region of the side face of the strand which is compressed can be minimized.

In a further embodiment of the invention, the surface of the first jaw acting on the first side face of the strand may be in the shape of a rhombus, while the second jaw acting on the second side face of the jaw may have a rectangular surface.

In a region which extends to either side of the interface between the start and the end of the strand, pressure may be exerted on the upper side of the strand using a die. This preferably occurs before pressure is exerted on the side faces of the strand for the first time. Exerting pressure on the upper side of the strand has the advantage that the thickness measured between the side faces of the strand becomes slightly greater as a consequence of the action of the die. After lifting the die from the upper side of the strand, the action of the jaws on both side faces of the strand means that their separation can be reduced to the original value. The material squeezed out thereby between the two jaws facilitates and favours smoothing of the side faces in the region of the interface between the start and the end of the strand.

The first jaw is preferably applied to the strand in a manner such that it does not come into contact with the glass plate. This ensures that the first jaw does not leave any traces on the glass plate; they could no longer be removed after assembly of the insulating glass pane. The second jaw may come into contact with the glass plate. Traces which it left on the glass plate would in fact not be visible in the finished and installed insulating glass pane.

The surface of the jaws that comes into contact with the strand should consist of a material or be coated with a material to which the pasty strand does not adhere or only adheres so weakly that the jaws can only deposit and/or pick up from the strand a non-negligible quantity of the material of the pasty strand. In this manner, the butt joint between the start and end of the strand can be made far less conspicuous. Examples of materials to which the material of the pasty strand do not adhere or only adhere to a slight extent which may be considered are fluoropolymers, for example polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), fluoroethylenepropylene (FEP), and also polyether-ether ketone (PEEK) and polysiloxanes.

Adhesion of the material from which the strand is formed to the jaws can not only be kept to a minimum by the selection of the material, but also by keeping the roughness of the surface of the jaws which comes into contact with the strand to within predetermined limits. In this regard, the surface of the jaws which comes into contact with the strand may have a mean roughness Ra in accordance with DIN EN ISO 4287:2010 of 0.5 μm to 2 μm, for example, in particular from 1 μm to 1.5 μm. In this manner, the contact surface between the surface of the jaw which comes into contact with the strand and the strand can be reduced and the non-stick action—also in combination with selection of the material as mentioned above—can be improved.

In a further embodiment of the method, jaws may be used which consist of a material or which are coated with a material with a thermal conductivity of no more than 0.3 Watt/(m·K). This ensures that the post-treatment of a thermoplastic strand in the region of its butt joint does not result in local cooling of the side faces of the strands concerned to such an extent that its smoothing could be compromised.

Preferably, at least those surfaces of the jaws and of any optional die which could come into contact with the strand are heated. This is primarily advantageous when the strand consists of a thermoplastic material or mainly of a thermoplastic material. Heating has the advantage that the temperature and therefore the viscosity of the strand, primarily at the surface which is to be smoothed, can be maintained in a region in which the material of the strand can be shaped readily by the jaws. The surfaces of the jaws and optionally of the die may be heated to that temperature at which the pasty strand was applied to the glass plate. In this state, the pasty strand can readily be shaped for the purposes of the invention. To this end, the surfaces of the jaws and optionally of the die may be heated to a temperature in the range from 80° C. to 130° C., in particular to a temperature of 120° C. to 130° C. This temperature range is particularly suitable for the case in which a material based on polyisobutylene, which is a thermoplastic, is used for the pasty and subsequently consolidating strand.

If the strand contains a curing component wherein curing is not accelerated by heating, then in this case, heating of the jaws and optionally of the die may again be advantageous. In cases in which the strand contains a heat-curable component, it is recommended that the post-treatment in accordance with the invention be carried out as soon as possible, when the strand is still sufficiently pasty.

The jaws should be applied to the side faces of the pasty strand with a pressure which is so low that the first jaw does not leave any indentations which would be visible to the naked eye on the side face which will subsequently delimit the interior space of the insulating glass pane. Particularly advantageously, the pressure is selected in a manner such that the first jaw only just leaves no visible indentation on the first side face of the strand. The type and temperature of the material used for the strand determines what this pressure is. The optimum can be determined by testing.

Whether the action of the jaw on the strand leaves a persistent indentation in it and also whether material is left behind on the jaw when the jaw is lifted from the strand is not only dependent on the pressure with which the jaws act on the strand, but also on the duration of the action. Thus, the pressure with which the jaws act on the strand and the duration of the action are coordinated in a manner such that at least the first jaw is free of residue and its removal from the strand does not leave an indentation on the first side face of the strand which is visible to the naked eye. The pressure with which the optional die is applied to the upper side of the strand may also be limited in a manner such that it is set to be at the shortest possible distance from the glass plate that the die can be set to. Similarly, the shortest separation of the two jaws from each other can be preset to the nominal thickness or almost the nominal thickness of the strand.

The jaws may be components of a gripper. The first jaw is applied to the first side face of the pasty strand at which the separating line between the start and end of the strand as a result of the post-treatment should no longer be visible or no longer be as visible to the naked eye. The second jaw may be placed on the glass plate and be applied to the second side face of the strand which will subsequently face outwards in the insulating glass pane. The gripper may have a closed position in which the two jaws lie parallel to each other and be at a separation that is identical to the nominal width of the strand. If the open gripper is initially placed with the second jaw on the glass plate and applied to the side face of the strand which will subsequently face outwards and if the gripper is only then closed by moving the first jaw up to the nominal width of the strand, then in a particularly simple manner, the position of the strand is unchanged following the post-treatment. Because the first jaw does not leave any traces on the glass plate, it may be that the edge facing the glass plate could be slightly retracted from the surface of the glass plate, i.e. by fractions of a millimetre, with respect to the other, second jaw placed on the glass plate. In this manner, the glass plate may be used as a reference for setting the position of the first jaw on the pasty strand.

Normally, with different glass plates—possibly apart from at the corners—the strand is always at an identical distance from the edge of the glass plate. This means that it is possible to use the edge of the glass plate as a reference for setting the position of the jaw on the strand, and when the jaws are components of a gripper, the second jaw can be preset by positioning it at the edge of the glass plate.

The edges of the surfaces of the jaws and optional die acting on the side faces of the strand may be rounded. This is advantageous in order to prevent traces which are visible to the naked eye from being left on the strand, in particular on the first side face of the strand.

The surface of the first jaw by means of which pressure is applied to the first side face of the strand may have a contour and preferably has a contour which matches the given contour of the first side face of the strand. This further facilitates the solution to the problem of reducing or removing the visibility of the position of the butt joint between the start and the end of the strand in the first side face of the strand. Preferably, the contour of the surfaces of the second jaw and the optionally provided die are also matched to the given contour of the second side face of the strand or respectively the given contour of the upper side of the strand.

The two jaws may initially be disposed such that—with respect to the longitudinal extent of the strand—the center of their surfaces which are to be placed on the side faces of the strand lies in the center of the region over which the interface between the start and the end of the strand extends, and in that the jaws act a first time in this position with pressure on the two side faces of the strand, in that afterwards, the jaws are lifted from the strand and displaced a little further along the strand in one direction and in the position obtained by the displacement, pressure is again applied to the side faces of the strand, in that subsequently, the jaws are displaced in the opposite direction a little further along the strand over and past the center of the region over which the interface between the start and the end of the strand extends and in the position attained by the second displacement, act again on the side faces of the strand. In this manner, the offset is selected each time in a manner such that the surface regions of the strand on which the displaced jaws act overlap with the central region of the strand in which its side faces were first acted upon. This procedure has the advantage that—if, despite everything, a small indentation remains on the first side face of the strand—it will be less discernible or even no longer discernible with the naked eye. To achieve this, particularly advantageously, the action on the side faces of the strand with jaws which are displaced with respect to the central position is repeated at least one more time, wherein the magnitude of the offset with respect to the initial central position of the jaws can then be equal to or different from the preceding offset.

Advantageously, the time during which the pressure is exerted on the side face of the strand is no longer than 1 second in each case. If pressure is exerted again on the side faces of the strand, advantageously, the duration for times subsequent to the first time during which the pressure is exerted is shorter than when the pressure is exerted on the side faces of the strand for the first time.

The invention is suitable both for the manufacture of rectangular insulating glass panes and also for the manufacture of shaped panes. Shaped panes are insulating glass panes with a contour that differs from the rectangular shape. The procedure during the manufacture of shaped panes may be such that the position at which the start and end of the strand butt together lies in a linear section of the strand. This procedure means that the post-treatment of the butt joint is easier to carry out than if it were in a curved section of the spacer. The post-treatment may, however, also be carried out when the butt joint lies at a corner of the applied frame-shaped strand, and might even extend beyond the corner. This has the advantage that the butt joint may be found at a position on the insulating glass pane at which it is less conspicuous than in a linear section of the edge of the insulating glass pane.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The nozzle1shown inFIGS.1to5for applying a pasty strand2to the surface3of a glass plate4is attached to the end of a shaft5which is rotatable about a rotational axis6which is perpendicular to the surface3of the glass plate4. The shaft5is hollow in configuration and opens into a channel7which passes through the nozzle1and leads to a discharge opening8of the nozzle1. The nozzle1has an end face9which in its working position is inclined to the surface3of the glass plate4and directly borders the discharge opening8which is perpendicular to the surface3of the glass plate4. The discharge opening8has an essentially rectangular outline. The rotational axis6of the shaft5runs through the center of the discharge opening8.

The hollow shaft5serves to rotate the nozzle1about its rotational axis6as well as to supply, to the nozzle1, the pasty mass which is to be applied to the glass plate4. A slide valve10is provided in order to close the discharge opening8; it is interchangeable and disposed between a wall11of the channel7which is disposed parallel to the rotational axis6and a removable counter-holder12. The slide valve10is guided in displacement parallel to the rotational axis6between the wall11and the counter-holder12. In order to be able to displace it, it is provided with a rack13which engages with a pinion14which can be controlled and driven by a small electric motor15mounted on the shaft5.

In order to apply a pasty strand to the surface3of the glass plate4, the nozzle1is initially brought close to the surface3of the glass plate4in the direction of the rotational axis6until the nozzle1comes into contact with the surface3of the glass plate4or almost comes into contact with it. During this, the discharge opening8of the nozzle is initially closed by the slide valve10. This situation is shown inFIG.2.

The nozzle1is then moved along the edge of the glass plate4, wherein the distance of the nozzle1from the edge of the glass plate4is kept as uniform as possible. The nozzle1may in this manner be moved along the edge of the glass plate4, either by moving the nozzle1and keeping the glass plate4stationary or by moving the glass plate4and keeping the nozzle1stationary, or by moving both the nozzle1and the glass plate4in a coordinated manner. The movement of the nozzle1relative to the glass plate4is made in a direction which is opposite to the discharge opening8of the nozzle1.

In the start phase of the movement over a section with length L (seeFIG.3), the slide valve10is steadily opened until it reaches a predetermined position in which the strand2dispensed from the nozzle1has its nominal thickness D. Because the slide valve10is opened steadily, in the start phase on the section with length L, the strand2has a steadily increasing thickness so that the upper side of the strand2here has an inclined face16which provides the first section of the strand2with the shape of a ramp which is inclined upwards, with length L.

The nozzle1is moved around the glass plate4parallel to the surface3of the glass plate4at the edge thereof, depositing thereby a strand2with an essentially uniform cross section and uniform thickness D on the glass plate4, to which the strand2adheres. Finally, the nozzle1comes back to the ramp16, seeFIG.4. It continues its movement unchanged relative to the glass plate4, until finally its lower edge17reaches the tip18of the start section of the strand2. Because of the inclined profile of the lower end face9of the nozzle, the angle of which can be selected to be somewhat greater than the angle between the surface3of the glass plate4and the upper surface of the ramp16, planar contact does not occur between the lower end face9of the nozzle1and the ramp16. As the movement of the nozzle1relative to the glass plate4continues in the direction of the arrow19, the nozzle1is now lifted up in a controlled manner from the glass plate4, so that its lower edge17moves along the upper side of the ramp16. Simultaneously and synchronously therewith, the slide valve10is steadily advanced in the direction of its closed position; it reaches its closed position when the lower edge17of the nozzle1has reached the upper end20of the ramp16. This status is shown inFIG.5.

In this manner, a wedge-shaped end section21of the strand is formed, which is configured in complementary manner to the ramp16and rests on the ramp16so that the strand2forms a closed frame which adheres to the glass plate4the edge of which lies externally of the frame.

The wedge-shaped end section21may be applied to the ramp16in a manner such that here, the strand2is slightly thicker than the nominal thickness D of the strand2. This facilitates obtaining a particularly reliable and tight bond between the ramp16and the wedge-shaped end section21upon subsequent compression of the insulating glass pane. This surplus thickness can readily be obtained by not starting the closing movement of the slide valve10when reaching the ramp16until the lower edge17of the nozzle1has already passed over the tip18of the starting section of the strand2(the start of the ramp16) by a short distance which is small compared with the length L of the ramp16.

The edge22of the interface between the start and the end of the strand2, i.e. between the edge16and the wedge-shaped end section21of the strand2, is initially easy to see. This visibility is reduced or completely removed by applying the invention.

FIG.6shows a portion of the glass plate4with a strand2applied thereto, in top view. The strand2lying on the glass plate4runs parallel to the edge27of the glass plate24and has a first side face23, which in the subsequent insulating glass pane faces the interior space of the insulating glass pane, and has a second side face24which faces outwards. The side of the strand2facing the observer inFIG.6is denoted its upper side25here; the side of the strand2lying on the glass plate4is termed its lower side26. The edge22of the interface between the start and end of the strand2is seen inFIG.6as a line which is perpendicular to the two side faces23and24. The arrow19indicates the longitudinal direction of the strand2in which the nozzle1is moved relative to the glass plate4.

FIG.7shows a cross section through a portion of the glass plate4with a view of the first side face23of the strand2, on which the edge22of the interface between the ramp16and the wedge-shaped end section21of the strand2running obliquely to the surface3of the glass plate4can be seen. In order to reduce the discernibility of this edge22or to remove it, a jaw35is applied to this edge22and to an adjacent region of the first side face23of the strand on either side of the edge22, which jaw35is pressed onto the edge22, completely or partially covering the side face23, at least once, preferably repeatedly. The jaw35may lie flush against the side face23and its surface acting on the side face23may have a rectangular outline, as shown inFIG.8; it may also have a rhomboidal outline, as shown inFIG.9. The latter has the advantage that the contact surface between the jaw35and the side face23of the strand2can be minimized. In both cases, the jaw35may maintain a small distance from the surface3of the glass plate4, so that it cannot leave any traces on the surface3of the glass plate4.

Merely for safety reasons, a second jaw36is placed opposite to the jaw35and is applied to the second side face24of the strand2and acts as an abutment, preventing the first jaw35from displacing the strand2in the region of the connecting point between the start and the end of the strand2from its nominal position outwardly in the direction of the nearby edge27of the glass plate4.

The surfaces of the two jaws35and36which act on the strand2should have a property that enables the jaws35and36to be removed from the strand2without substantial residues of the preferably thermoplastic material from which the strand2consists, at least at its surface, remaining adhered to the jaws35and36. With the first jaw35, which acts on the first side face23of the strand2, which lies internally in the finished insulating glass pane, residues which originated from the first side face23of the edge2and which could leave traces which were easily visible to the naked eye could be substantial and therefore would be undesirable. On the opposite side face24of the strand2, the requirements are less strict, because in the finished and installed insulating glass pane, the side face24is no longer visible. Examples of materials to which hot thermoplastic masses based on a polyisobutylene, which are in routine use to seal insulating glass panes, do not adhere or adhere poorly are polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), fluoroethylenepropylene (FEP), polyether-ether ketone (PEEK) and polysiloxanes.

When the strand2has consolidated, the connecting point between the start and the end of the strand2can no longer be smoothed, and thus the connecting point can no longer be made less conspicuous or no longer discernible to the naked eye. Thus, preferably, the surface of the jaw is heated to a temperature at which the material from which the strand consists can still be shaped plastically; with a material based on a polyisobutylene, for example to a temperature in the range from 80° C. to 130° C., in particular to a temperature of 120° C. to 130° C. A temperature at which the material from which the strand2is formed is pumped to the nozzle1is particularly suitable.

Preferably, a die38is additionally provided, which can press in the direction of the arrow37on the upper side of the strand2before the two jaws35and36are pressed onto the side faces23and24. This has the advantage that the two side faces23and24can initially bulge outwards somewhat and in this manner, surplus material is present at the side faces23and24which is squeezed out when, after lifting the die38, the two jaws35and36press onto the side faces23and24of the strand2and close together up to the nominal width of the strand2. The squeezing process that occurs here reduces or removes the visibility of the connecting point between the start and end of the strand2.

Particularly preferably, the method has the following steps:

The two jaws35,36may initially be disposed such that—with respect to the longitudinal extent of the strand2—the center of their surfaces which are to be placed on the side faces23,24of the strand2lies in the center of the region over which the interface between the start and the end of the strand2extends, and in that the jaws35,36act a first time in this position with pressure on the two side faces23,24of the strand2after earlier, the die38has been pressed onto the upper side25of the strand2, in that afterwards, the jaws35,36are lifted from the strand2and displaced a little further along the strand in one direction, and in the position obtained by the displacement, pressure is again applied to the side faces23,24of the strand2, in that subsequently, the jaws35,36are displaced in the opposite direction a little further along the strand2over and past the center of the region over which the interface between the start and the end of the strand2extends and in the position attained by the second displacement, act again on the side faces of the strand. In this manner, the offset is selected each time in a manner such that the surface regions of the strand2on which the displaced jaws35,36act overlap with the central region of the strand2in which its side faces23,24were first acted upon. This procedure has the advantage that—if, despite everything, a small indentation remains on the first side face23of the strand2—it will be less discernible or even no longer discernible with the naked eye. To achieve this, particularly preferably, the action on the side faces23,24of the strand2with jaws35,36which are displaced with respect to the central position is repeated at least one more time, wherein the magnitude of the offset with respect to the initial central position of the jaws35,36then can equal to or different from the preceding offset.

FIG.10shows a section of a production line for insulating glass panes with a frame28, which carries a horizontal conveyor29with a series of synchronously operable conveyor rollers30as well as a support wall31, on which glass plates4standing on the conveyor rollers30can be supported. In the example shown inFIG.10, a glass plate4can be seen onto which a frame-shaped spacer has been applied which—as described above—is formed by a pasty strand2. This may be a strand2formed from a thermoplastic material, for example based on a polyisobutylene. A rail32is attached to the frame28and extends from bottom to top parallel to the support wall31and onto which a gripper33is attached for movement up and down, has a variable distance from the support wall31and is pivotably mounted about an axis running perpendicular to the support wall31. The rail32may be mounted in a stationary manner on the frame28, however it may also be displaceably mounted parallel to the horizontal conveyor29on a horizontal crossbeam34of the frame28.

The gripper33has a pair of jaws35and36which may have parallel facing surfaces which can move together, or it may have a contour which is matched to the side faces23and24of the strand2and their mutual separation can be varied between an open position and a closed position. In the closed position shown inFIG.10, the jaws35and36can apply pressure to the two side faces23and24of the strand2. In the open position, the jaws35and36release the strand2.

The glass plate4and the gripper33are positioned relative to each other in a manner such that the jaws35and36of the gripper33cover the side faces23and24of the strand2at the position where the start and end of the strand2meet. For a rectangular glass plate4, as shown inFIG.10, this position is advantageously always on the lower horizontal edge of the glass plate; however, as shown inFIG.11, it may be on an upright edge of the glass plate or, as shown inFIGS.12and13, for a glass plate4for the production of a shaped pane with an outline that differs from a rectangular shape, somewhere in a position along the edge of the glass plate4which is above the lower edge of the glass plate4. The described way of mounting the gripper33on the frame22with the possibility of moving it up and down as well as backwards and forwards and horizontally to and fro and of pivoting it about an axis which is perpendicular to the supporting wall31, means that it is possible to place the butt joint between the start and end of the strand2anywhere and to post-treat it in accordance with the invention.

FIG.14shows an enlarged section of the equipment shown inFIG.10with the gripper33open. The jaws35and36are in the open position and parallel to each other and further apart than in the closed position. By pushing the gripper33forwards against the glass plate4, the jaws35and36are in a position in which they only have to be moved towards each other. The lower, second jaw36makes contact with the surface3of the glass plate4, but the upper, first jaw35does not. A die38is placed on the upper side25of the strand2and is pushed forwards between the two jaws35and36out of the gripper body40, and thus is brought to sit on the upper side25of the strand2; before closing the gripper33, it can compress the strand2and thereby make the action of the jaws35and36on the side faces24and25of the strand more effective.

By reducing the separation of the two jaws35and36between each other, they come to lie on the side faces23and24of the strand2and then cover the edge22of the interface lying between the start and end of the strand2.

The closed position of the gripper33is shown inFIGS.15and16.FIG.16clearly shows that the lower jaw36can come into contact with the glass plate4while the upper jaws35maintains a small distance from the surface3of the glass plate4. The die38is between the two jaws35and36and comes into contact with the upper side25of the strand2, preferably before the two jaws35and36act upon the side faces23and24of the strand2. After completing the application of pressure to the strand2, the gripper33is opened again and withdrawn from the glass plate4so that the glass plate4with the frame-shaped spacer formed by the strand2adhering to it can be conveyed away on the horizontal conveyor29without the projecting section of the strand2colliding with the gripper33. Preferably, however, the glass plate is only conveyed after the jaws35and36have acted on a plurality of mutually offset and mutually overlapping sections. In this regard, either the gripper33can be displaced relative to the stationary glass plate4, or the glass plate4can be displaced relative to the stationary gripper.

List of reference signs1nozzle2pasty strand3surface of 44glass plate5hollow shaft6rotational axis7channel8discharge opening9end face10slide valve11wall12couner-holder13rack14pinion15electric motor16inclined face, ramp17lower edge of 118tip of start section of 219arrow shows the movement of the nozzle inthe longitudinal direction of the strand20upper end of 1621wedge-shaped end section of 222edge of interface between 16 and 2123first side face of 224second side face of 225upper side26lower side27edge of glass plate 428frame29horizontal conveyor30conveyor rollers31support wall32rail33gripper34crossbeam35jaw36jaw37arrow38die39arrow40gripper bodyBnominal width of strand 2Dnominal thickness of strand 2Llength of ramp 16