EP2429805A1

EP2429805A1 - Method and tool for repair of laminated glass

Info

Publication number: EP2429805A1
Application number: EP10727651A
Authority: EP
Inventors: Claus Grøndal HENRIKSEN
Original assignee: Greentek/racing V/claus Grondal
Current assignee: Greentek/racing V/claus Grondal
Priority date: 2009-05-12
Filing date: 2010-05-12
Publication date: 2012-03-21
Also published as: DK200900608A; WO2010130264A1

Abstract

A method for repairing damage (17) in laminated glass (18), preferably a windscreen in a car, by injecting resin, wherein a support tool (19) is fastened temporarily to the glass (18) opposite the damage (17), where an injection tube (4) with a packing means (3) provided at one end with a resin compartment (5) is attached to the support tool (19) and with the packing means (3) in tightly fitting contact with the glass (18), where resin is filled into the injection tube (4), where a piston arrangement (1) with a piston face (2) is inserted in the injection tube (4), and wherein a repair cycle including the steps of: - establishing an positive pressure in the resin chamber (5) for pressing resin into the damage (17); - establishing a first negative pressure in the resin chamber (5) for degassing the resin; is repeated until the damage (17) is filled with resin and the resin is sufficiently degassed, by which the repair cycle further includes the step of: - establishing a second negative pressure in the resin compartment (5) for drawing out moisture and foreign bodies from the damage (17), where the second negative pressure has a maximum value which is greater than a maximum value of the first negative pressure. Furthermore a piston arrangement (1) for use in performing the method.

Description

Method and Tool for Repair of Laminated Glass

Field of the Invention

The present invention concerns a method for repairing damage in laminated glass, preferably a windscreen in a car, by injecting resin, wherein a support tool is fastened temporarily to the glass opposite the damage, where an injection tube with a packing means provided at one end with a resin compartment is attached to the support tool and with the packing means in tightly fitting contact with the glass, where resin is filled into the injection tube, where a piston arrangement with a piston face is inserted in the injection tube, and wherein a repair cycle including the steps of: - establishing an positive pressure in the resin chamber for pressing resin into the damage;

- establishing a first negative pressure in the resin chamber for degassing the resin; is repeated until the damage is filled with resin and the resin is sufficiently degassed.

The invention furthermore concerns a piston arrangement for use in repairing damages in laminated glass, preferably a car windscreen, by injecting resin, wherein the piston arrangement is provided with a piston face adapted for tight-fitting insertion into a packing means in an injection tube, and where the packing means at one end is provided with a resin chamber.

hi the present application, by sufficiently degassed is meant that the amount of gas bubbles in the resin has reached a level where additional repetition of the repair cycle does not cause visible changes in the resin.

Background of the Invention From US 3,993,520 is known a method and a tool for repair of laminated glass, in particular car windscreens, where a resin is injected into a crack in the glass. The tool includes a bridge which is mounted on the glass opposite the damage. The bridge is secured by suction cups on the glass. An injection tube is screwed into the bridge. The injection tube has means for establishing tight-fitting contact between the interior of the tube and the damage. Resin is filled into the lower part of the injection tube, which is called a resin compartment, after which a piston is screwed into it. An positive pressure hereby arises in the resin chamber such that the resin flows into and fills the crack. When the piston is screwed out, a negative pressure arises, drawing air bubbles out of the resin. The piston is alternatingly screwed back and forth in order thereby to "massage" the resin into the crack and to remove trapped air. This massage is repeated until the crack is filled with resin and the resin is degassed to a level where further repetition does not provide visible changes. It is particularly time-consuming by great damages where relatively large amounts of resin are applied. An average repair typically takes 15 to 20 minutes.

If the damage is not covered immediately after its occurrence, moisture and foreign bodies will penetrate into the damage.

The resin has the same refraction index as the glass when hardened, such that the repaired damage is largely not seen on the condition that it is possible to extract all visible air bubbles, trapped foreign bodies and moisture in the resin. If this is not the case, the repaired damage will remain visible to a greater or lesser degree. The magnitude of the negative pressure required for repairing a damage such that it becomes invisible, depends on the extent of the damage as this determines the amount of resin to be degassed, the age of the damage as this determines the amount of moisture and foreign bodies that have penetrated into the damage, and whether the damage has been covered.

The area of the piston and its travel defines the size of the positive pressure and the negative pressure that may be attained. Since the pressure is on an incompressible liquid, very high positive pressures may be attained (> 100 psi ~ 6,8 atm.). Therefore, it is desirable with a relatively small piston area and a stroke providing better options for fine-tuning the pressure in order to avoid the pressure becoming too large during injection of the resin such that the glass bursts around the damage.

When the piston is screwed out, a drawing in a compressible gas is performed. The maximum size of the negative pressure that may be achieved by the same piston dimension is thus limited, and not near the absolute and maximum negative pressure (1 atm). The rate at which the resin is degassed and the size of the foreign bodies that may be drawn out of the damage depend directly on the magnitude of the negative pressure.

Thus it is desirable to attain an positive pressure of a limited size during injection of resin such that the crack is not made worse, while during formation of negative pressure it is desirable for it to be as great as possible for faster degassing of the resin and for repairing cracks that contain foreign bodies and moisture due to insufficient covering or cracks which are large.

Therefore, use of the repair tool according to US 3,993,520 presupposes that the damage is small, and that the damage is repaired or covered immediately after the damage has occurred, such that moisture and foreign bodies do not penetrate into the crack, since the piston dimension is limited by the allowable maximum positive pressure by injection of the resin, in turn entailing a substantial limitation to the size of the attainable negative pressure. This results in a repair where trapped foreign bodies or moisture may be present in the damage which thereby is still visible in spite of the reparation.

Object of the Invention

It is the object of the invention to indicate a tool for repairing damages in laminated glass panes, where the design of the tool makes it suited for repair of both small and large cracks, and in particular cracks containing moisture and foreign bodies. In addition, it is an object of the invention that it may be used in existing systems for repairing glass panes.

Description of the Invention This is achieved according to the present invention by a method of the kind mentioned in the introduction, which is peculiar in that the repair cycle further includes the step: - establishing a second negative pressure in the resin compartment for drawing out moisture and foreign bodies from the damage, where the second negative pressure has a maximum value which is greater than a maximum value of the first negative pressure. Furthermore, this it achieved by a piston arrangement of the type specified in the introduction which is peculiar in that the piston arrangement includes an inner pressure chamber with a displaceable inner piston body which may be displaced between a first extreme position at which the volume of the inner pressure chamber is the least, and a second extreme position at which the volume of the inner pressure chamber is the largest, and that an opening is formed in the piston face, the opening establishing a connection between the resin compartment and the inner pressure chamber.

Hereby is achieved that it is possible to repair even large cracks and cracks containing moisture and foreign bodies, as the repair worker has the option of adding a negative pressure which is greater than that which the piston face may produce only by itself. Thereby it will be possible to extract even large amounts of moisture and large foreign bodies due to the greater negative pressure. In addition is achieved the effect that the degassing of the resin proceeds rapidly and become more extensive.

The size of the total negative pressure that may be formed in the resin compartment during performing of the method, is the first negative pressure added the second negative pressure.

Moreover, it is achieved that the piston surface in the piston arrangement with the inner piston body in its first extreme position may function as a conventional piston where an positive pressure may be established in the resin compartment such that the resin is pressed in and fills the damage in the glass. This positive pressure has a limited size so as to avoid worsening of the damage.

Besides, a first negative pressure may be established in the resin chamber for degassing the resin. This negative pressure has a limited size and will in some cases be sufficient to degas the resin sufficiently, but will in many cases only contribute to partial degassing of the resin and not at all sufficient for extracting moisture and foreign bodies. In the latter case, the inner piston body is displaced towards its second extreme position, whereby a second negative pressure is established. The total negative pressure in the resin exceeds what the piston face may produce by itself. Hereby, the negative pressure may be of a size where moisture and foreign bodies may be extracted from the damage, and where degassing the resin proceeds rapidly and without requiring time-consuming massage back and forth of the piston face.

By the method and the piston arrangement, the skilled in the art repairing damage in laminated glass will be able to repair small as well as large damages, with and without moisture and foreign bodies in a rapid and simple way, and with a quality of the reparation by which it becomes invisible.

By performing the method, a support tool is used, a so-called "bridge", which is temporarily fastened to the glass over the damage by means of suction cups which can be released when the repair work is completed. The support tool typically has a through-going screw threaded hole which is adapted to receive the injection tube having an interacting thread on the outer side such that it may be screwed into the screw threaded hole.

The injection tube includes a packing means. This packing means is typically designed such as to be in tight-fitting contact with the surface of the glass when the injection tube has been screwed into the support tool, and so that it is in tight-fitting contact with the piston arrangement when inserted in the injection tube so that a hermetic resin compartment is formed in front of the piston face and above the glass surface.

The packing means may advantageously be provided with one or more lip seals along the inner side. These lip seals are directionally oriented such that they are either closing tightly around the part of the piston arrangement inserted in the packing means by negative pressure or positive pressure in the resin compartment, depending on their position along the length of the packing means. Close to the top position of the piston face in the packing means, this may have an upper lip seal which is adapted so as not to allow building up of pressure in the resin compartment but building up of a negative pressure.

When the inner piston body has been displaced against its second extreme position for building up a negative pressure in the inner pressure chamber and in the resin compartment, the resin will be degassed in the form of excess air. Now there will be an amount of excess air in the inner pressure chamber and the resin chamber. The excess air may be ventilated out of the piston arrangement past the upper lip seal by displacing the inner piston body back to the first extreme position, as the lip seal does not allow building up of pressure in the resin compartment.

Under the upper lip seal, the packing means will have one or more lip seals which are adapted such as to allow building up of a pressure in the resin compartment. Hereby it becomes possible again to build up a pressure in the resin compartment by moving the piston face into the packing means.

The function of the packing means may e.g. be as described in US 3,993,520.

The prestressing force of the injection tube against the glass surface may be read by assessing how much the packing means is expanded. This is done by inspecting the packing means from the opposite side of the glass. This inspection can be facilitated by placing a mirror, typically fastened by suction cups, at the inner side of the glass opposite the damage such that the repairman can perform this inspection from outside.

The invention is particularly suited for use together with a support tool and an injection tube with a packing means as known from US 3,993,520.

When the support tool and the injection tube with packing means are disposed as desired, resin is filled into the injection chamber. This may be performed by an hypodermic syringe having a needle which is long enough to reach into the injection tube and packing means to the resin chamber. The piston arrangement which has a diameter corresponding to the inner diameter of the packing means is inserted in the injection tube. An positive pressure hereby arises in front of the piston surface, forcing the resin to flow from the resin chamber and into the damage. The damage is hereby filled with resin.

The piston surface is then moved back such that a first negative pressure arises in front of the piston surface. Since the resin has a higher viscosity, the greater part of the resin will remain in the damage while the trapped air bubbles in the resin will be drawn out.

A second negative pressure may be established in the resin by means of the inner pressure chamber in the piston arrangement for drawing out foreign bodies and moisture and for faster degassing. The second negative pressure is achieved by displacing an inner piston body in the inner pressure chamber in the piston arrangement. The volume of the pressure chamber is determined by the disposition of the inner piston body. In the first extreme position of the piston body, the volume of the pressure chamber is the least, and in the second extreme position, the volume of the pressure chamber is the greatest.

The piston arrangement is typically designed with a cylindric cavity in which the piston body is arranged with a packing means. The packing means are adapted to fit tightly against the inner side of the cylindric cavity under longitudinal displacement of the piston body for establishing a pressure chamber between the piston face opening and the piston body.

Since a connection is established between the resin chamber and the inner pressure chamber through the piston face opening, the pressure in the inner pressure chamber and the pressure in the resin chamber will be the same. When the piston body is displaced from the first extreme position where the volume of the inner pressure chamber is the least against the second extreme position where the volume of the inner pressure chamber is the greatest, a negative pressure will be formed in the inner pressure chamber and thereby the resin chamber. The size of the negative pressure gradually rises without sudden pressure pulses during the displacement from the first extreme position against the second extreme position. The tool may perform repairs without moving the piston body completely to its second extreme position, as partial displacement of the piston body against the second extreme position may be enough for the resin to be sufficiently degassed.

In an alternative embodiment, the piston arrangement is formed by a jacket in which a commercially available disposable hypodermic syringe is inserted. The piston body is provided with the packing means from the hypodermic syringe and provided with a point extending down into the interior of the pistons arrangement to the piston face such that the point forms closure of the opening in the piston face.

Hereby is achieved adaptation of the piston arrangement in a particularly simple way whereby secure tightness is achieved as the cavity of the piston arrangement, here the interior of the hypodermic syringe, and the packing means have a demonstrated tightness. The arrangement is thus less sensitive to production tolerances.

The repairman continues with repeating the individual steps in the repair cycle until no further improvements can be achieved by further repetitions.

While performing the method, there are holding times for the various process steps. By a piston arrangement according to the invention, an average repair of a damage typically takes 8-10 minutes.

By a piston arrangement according to the invention, it is only necessary with a limited number of repetitions as compared with prior art. Since this type of repair is often made as piecework, it is very important that repairs can be executed in the shortest possible time but with the best possible quality.

Since the invention can be used directly with already known and widely used repair systems, the repairman can avoid carrying various types of repair systems. This also means that the individual repairman is only to receive instruction in use of the new piston arrangement together with the prior art injection tube and the support arrangement, and only the part of the method concerning the second negative pressure. If the repairman for some reason wants to shift freely between a system of the type known from US 3,993,520 and the system in the present application, this can readily be done as the system may be used without permanently changing the known elements.

According to a further embodiment, the method according to the invention is peculiar in that that the second negative pressure in the resin compartment is established by displacing an inner piston body from a first extreme position against a second extreme position in an inner pressure chamber in the piston arrangement, and that connection between the resin compartment and the inner pressure chamber is formed by an opening in the piston face of the piston arrangement.

Hereby is achieved that a negative pressure is formed in the resin chamber which is not limited by the size of the piston face which is dimensioned according to the desired maximum pressure. A negative pressure which is substantially greater than the negative pressure possibly attained only by retracting the piston face may easily be achieved

According to a further embodiment, the method according to the invention is peculiar in that the positive pressure in the resin chamber is established by screwing the piston arrangement into the injection tube.

Hereby is achieved a precise regulation of the pressure in the resin chamber as the travel of the piston face is small in relation to how much the piston arrangement is to be rotated. The rise of pressure per revolution of rotation of the piston arrangement is therefore small.

The screw thread may advantageously be designed such that the screw connection between the injection tube and the piston arrangement becomes self-locking such that no other means for retaining the piston arrangement at the desired position for a given pressure are required. There is established an external screw thread on the piston arrangement where the screw thread extends outside the packing means when the piston face is at a position where it is fully inserted in the injection tube. The screw thread of the piston arrangement interacts with an inner screw thread in the injection tube above the packing means.

The design of the screw thread of the piston arrangement, including type, diameter and pitch, may advantageously be chosen such that it fits with known injection tubes.

According to a further embodiment, the method according to the invention is peculiar in that the first negative pressure in the resin chamber is established by screwing the piston arrangement back into the injection tube.

Hereby is achieved a precise regulation of the negative pressure in the resin chamber as the travel of the piston face is small in relation to how much the piston arrangement is to be rotated. The pressure drop per revolution of rotation of the piston arrangement is therefore small.

The screw thread may advantageously be designed such that the screw connection between the injection tube and the piston arrangement becomes self-locking such that no other means for retaining the piston arrangement at the desired position for a given pressure are required.

There is established an external screw thread on the piston arrangement where the screw thread extends outside the packing means when the piston face is at a position where it is fully inserted in the injection tube. The screw thread of the piston arrangement interacts with an inner screw thread in the injection tube above the packing means.

The design of the screw thread of the piston arrangement, including type, diameter and pitch, may advantageously be chosen such that it fits with known injection tubes. According to a further embodiment, the piston arrangement according to the invention is peculiar in that the connection between the resin chamber and the inner pressure chamber is established when the piston body is displaced from its first extreme position, and that the connection is closed when the piston body is in its first extreme position.

Hereby is achieved a simple way of varying the negative pressure as the negative pressure rises as soon as the piston arrangement is displaced from its first extreme position. It becomes possible to build up pressure in the resin chamber without having to compress possible air in the inner pressure chamber.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that the piston arrangement has an external screw thread which is complementary to an inner screw thread in the injection tube.

Hereby may be achieved that the piston arrangement may directly form part of a known repair system of a type disclosed in US 3,993,520.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that the piston arrangement is provided with means for retaining the inner piston body at the first extreme position and at the second extreme position, respectively.

Hereby is achieved that it becomes easier precisely to hold the desired negative pressure in the holding time for performing the method step where a second negative pressure is established in the resin chamber.

Moreover, the repairman is free to perform other tasks while the second negative pressure is retained in the first or in the second extreme position.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that the piston arrangement is provided with means for retaining the inner piston body at at least one intermediate position between the first and second extreme positions.

Hereby is achieved that the size of the second negative pressure may be regulated accurately and be retained at at least one position between the two extreme positions. This may be desirable if it is not necessary to apply maximum negative pressure.

The means for retention may be designed so that they allow stepless or stepwise retention between the two extreme positions.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that the piston body has a rod-shaped handle and is adapted for manual displacement in its longitudinal direction between the two extreme positions.

Hereby is achieved that the repairman may easily displace the piston body to the desired position without external power supply in the form of pneumatically, hydraulically or electrically powered actuators.

The piston arrangement is thereby independent of external power supply sources, thus increasing the applicability to include on-site repairs at places where such sources are not available.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that it is provided with an insertion opening for the rod-shaped handle, where the shape of the insertion opening corresponds to the cross-section of the rod- shaped handle, that the rod-shaped handle is designed with at least one narrowed cross-section having the greatest transverse dimension such that the narrowed cross- section may be brought to engage the edge area of the insertion opening by rotating the rod-shaped handle in order to define and retain the rod-shaped handle in at least one of the following: the first extreme position, the second extreme position and the at least one intermediate position. In a simple way is hereby achieved establishing a locking of the rod-shaped handle and thereby the piston body at a defined position, such that it is not necessary for the repairman to retain the piston body in order to define a desired pressure.

The rod-shaped handle and the insertion opening have corresponding cross-sections so that it is possible to displace the rod-shaped handle into and out of the insertion opening. The cross-sections may have various designs, e.g. triangular, quadrangular, pentagonal, rectangular, oval, polygonal, sectors of a circle, and combinations of these. The cross-sectional shapes may be symmetric or asymmetric.

The narrowed cross-section may also have different shapes. The greatest transverse dimension of the narrowed cross-section may, however, not be greater than it allows rotation of the rod-shaped handle when the narrowed cross-section and the insertion opening are aligned.

An example of a cross-sectional design of the insertion opening and the rod-shaped handle may be a rectangular shape. The narrowed cross-section may be circular with a diameter which is less than the shortest transverse dimension of the rectangle. Such a design will allow longitudinal displacement of the rod-shaped handle and thereby the piston body through the insertion opening. By rotation of the rod-shaped handle at positions with the piston body at a desired position for retention - the first extreme position, the second extreme position or at the said at least one intermediate position, depending on the shape of the rod-shaped handle, the rod-shaped handle will be in engagement with the edge region of the insertion opening.

Description of the Drawing

The invention will be explained in more detail below with reference to the accompanying drawing, where: Fig. 1 shows prior art from US 3,993,520;

Fig. 2 shows a sectional view of the support tool, the injection tube and the piston arrangement;

Fig. 3 shows an isometric view of the piston arrangement with the piston body in its first position; Fig. 4 shows an isometric view of the piston arrangement with the piston body in its second position;

Fig. 5 shows a side view of the piston body with the rod-shaped handle, and Fig. 6 shows an isometric view of a detail of the rod-shaped handle and the piston arrangement.

hi the explanation of the Figures, identical or corresponding elements will be provided with the same designations in different Figures. Therefore, no explanation of all details will be given in connection with each single Figure/embodiment.

Detailed Description of Embodiments of the Invention

Fig. 1 show three figures of US 3,993,520 as prior art. The numbering used in the description below refers exclusively to Fig. 1. Only a description of the parts relevant to the present application is included.

The support arrangement 20 is temporarily attached to the surface of the laminated glass 12, 13, 14 with suction cups 22. An injection tube 28 with a packing means 33 is screwed into a thread in the support arrangement 20 such that the packing means 33 is in tightly fitting contact 33 A with the glass surface above the damage 1 IA and 1 IB.

Resin is filled into the resin chamber 44 of the injection tube.

A piston 40 is inserted in the injection tube 28 with a lower part 42 in tightly fitting contact with the packing means 33 that has lip seals 33B, 33C, 33D. The lower part 42 has a piston surface by which an positive pressure or negative pressure may be applied to the resin chamber 44, depending on whether the piston 40 is screwed in or out.

As it appears from the drawing, only a limited negative pressure can be achieved by the piston 40, as the negative pressure is established by the same piston face producing the positive pressure, cf. the section "Background of the Invention" in the present application. Fig. 2 shows a laminated glass pane 18 with a damage 17. A support tool 19 is temporarily fastened to the glass 18 with suction cups (not shown).

An injection tube 4 is located in the support tool 19 and secured by an interacting screw thread. The injection tube 4 has a packing means 3 which is in tightly fitting connection with the glass 18. The packing means 3 is provided at one end with a resin chamber 5 for receiving resin before injection into the damage 17.

A piston arrangement 1 is inserted in the injection tube 4. The piston arrangement 1 is provided with a piston face 2 at its lower end. This piston face 2 is in tightly fitting contact with the packing means 3. It is thus possible to establish an positive pressure or negative pressure in the resin chamber 5 by moving the piston face 2 in the packing means 3.

The injection tube 4 has an inner screw thread 10 that interacts with an outer screw thread 9 on the piston arrangement 1. The piston surface 2 may hereby be retained at a desired position in the packing means 3 and thereby define a desired pressure in the resin chamber 15.

The pressure in the resin chamber 5 is increased by screwing in the piston arrangement and is reduced by screwing out the piston arrangement.

A packing means as shown during the description of prior art in Fig. 1 may be chosen. Alternatively, a packing means 3 with more or fewer lip seals may be chosen, depending on the travel of the piston on the desired pressure. The piston arrangement 1 has an inner pressure chamber 6 with a piston body 7. On Fig. 2, the piston body is shown at an intermediate position between the first and second extreme positions.

The piston body 7 is provided with a packing 21 that prevents exchange between the inner pressure chamber 6 and the surroundings. The piston body 7 is provided with a point 20, and when the piston body 7 is in its first extreme position, this point 20 closes the opening 8 established in the piston face 2 when the piston body 7 is displaced from the first extreme position against the second extreme position. The piston face 2 is thus formed by the end of this point 20 and the jacket 22 of the piston arrangement enclosing the piston body 7 with associated point 20.

The connection between the resin chamber 5 and the inner pressure chamber 6 is formed between the point 20 and the interior of the jacket.

When the piston body is at its first extreme position, where the inner pressure chamber 6 has its smallest volume, and there is no communication between the resin chamber 5 and the inner pressure chamber 6, the piston arrangement 1 can be used as the piston of the prior art.

When the piston body 7 is displaced from the first extreme position against the second extreme position, it becomes possible to establish a negative pressure in the resin chamber 5 of a size which is not possible to achieve by the piston of the prior art. Hereby, it becomes possible for the repairman to attain a greater negative pressure providing faster degassing of the resin and enabling extraction of moisture and foreign bodies from the damage 17 as well.

Figs. 3 and 4 show an embodiment of the piston arrangement where this consists of an outer jacket 22 enclosing the piston body 7 and the inner pressure chamber 6 (see Fig. 2). The jacket is provided with external screw thread 9 adapted for interacting with inner screw thread 10 of the injection tube. The piston body 7 (see Fig. 2) is connected with a rod-shaped handle 13 that enables manual displacement of the piston body 7 (see Fig. 2). The jacket 22 is provided with a cover 23. The cover 23 has an insertion opening 14 for inserting and controlling the rod-shaped handle 13. On Fig. 3, the piston body (see Fig. 2) is at its first extreme position, and in Fig. 4 the piston body (see Fig. 2) is in its second extreme position. It appears from Fig. 4 that the rod-shaped handle 13 is provided with a cross-section having a shape corresponding to the cross- section of the insertion opening. The rod-shaped handle 13 is provided with narrowed cross-sections 15. In the shown embodiment, there are three narrowed cross-sections 15. These define and enable fastening in the first and second extreme positions 11 and in an intermediate position 12. For the repairman, it is thus not necessary to retain the rod-shaped handle 13 manually during the holding times in the individual method steps.

Fig. 5 shows the piston body 7 with the rod-shaped handle 13. The piston body has a packing 21 for tightly fitting contact during the manual displacement in the jacket 22 of the piston arrangement. The piston body has a point 20 which is inserted through the jacket 22 (see Figs. 3 and 4).

The end of the point thus becomes part of the piston face 2 when the piston body is entirely inserted in the jacket 22 (see Figs. 3 and 4) and thereby into its first extreme position. The piston body 7 has a piston face 24 for establishing a negative pressure in the resin chamber of a different size.

Fig. 6 shows the means for retention in the extreme positions and means 11, 12 for retention in the intermediate position. When the rod-shaped handle is inserted in the insertion opening in the cover 23 of the piston arrangement to a position where one of the narrowed cross-sections 15 is opposite the insertion opening 14, the rod-shaped handle may be rotated such that the narrowed cross-section rests on the edge area 16 of the insertion opening. This is a simple and intuitive way of establishing retention at the extreme positions and the intermediate positions.

The skilled in the art may readily indicate embodiments with additional narrowed cross-sections 15 for more intermediate positions if required with regard to the wanted size of the pressure in the resin chamber 15.

Claims

1. A method for repairing damage (17) in laminated glass (18), preferably a windscreen of a car, by injecting resin, wherein a support tool (19) is fastened temporarily to the glass (18) opposite the damage (17), where an injection tube (4) with a packing means (3) provided at one end with a resin compartment (5) is attached to the support tool (19) and with the packing means (3) in tight-fitting contact with the glass (18), where resin is filled into the injection tube (4), where a piston arrangement

(1) with a piston face (2) is inserted into the injection tube (4), and wherein a repair cycle including the steps of: - establishing an positive pressure in the resin chamber (5) for pressing resin into the damage (17);

- establishing a first negative pressure in the resin chamber (5) for degassing the resin; is repeated until the damage (17) is filled with resin and the resin is sufficiently degassed, characterised in that the repair cycle further includes the step:

- establishing a second negative pressure in the resin compartment (5) for drawing out moisture and foreign bodies from the damage (17), where the second negative pressure has a maximum value which is greater than a maximum value of the first negative pressure.

2. Method according to claim 1, characterised in that the second negative pressure in the resin compartment (5) is established by displacing an inner piston body (7) from a first extreme position against a second extreme position in an inner pressure chamber (6) in the piston arrangement (1), and that connection between the resin compartment (5) and the inner pressure chamber (6) is formed by an opening (8) in the piston face

(2) of the piston arrangement.

3. Method according to claim 1 or 2, characterised in that the positive pressure in the resin compartment (5) is established by screwing the piston arrangement (1) into the injection tube (4).

4. Method according to claim 1, 2 or 3, characterised in that the first negative pressure in the resin compartment (5) is established by screwing the piston arrangement (1) back in the injection tube (4).

5. A piston arrangement (1) for use in repairing damages (17) in laminated glass (18), preferably a car windscreen, by injecting resin, wherein the piston arrangement (1) is provided with a piston face (2) adapted for tight-fitting insertion into a packing means (3) in an injection tube (4), and where the packing means (3) at one end is provided with a resin chamber (5), characterised in that the piston arrangement (1) includes an inner pressure chamber (6) with a displaceable inner piston body (7) which may be displaced between a first extreme position at which the volume of the inner pressure chamber is the least, and a second extreme position at which the volume of the inner pressure chamber is the largest, and that an opening (8) is formed in the piston face (2), the opening establishing a connection between the resin compartment (5) and the inner pressure chamber (6).

6. Piston arrangement according to claim 5, characterised in that the connection between the resin chamber (5) and the inner pressure chamber (6) is established when the piston body (7) is displaced from its first extreme position, and that the connection is closed when the piston body (7) is in its first extreme position.

7. Piston arrangement according to claim 6, characterised in that the piston arrangement (1) has an outer screw thread (9) which is complementary to an inner screw thread (10) in the injection tube (4).

8. Piston arrangement according to claim 5, 6 or 7, characterised in that the piston arrangement (1) is provided with means (11) for retaining the inner piston body (7) at the first extreme position and at the second extreme position, respectively.

9. Piston arrangement according to claim 5, 6, 7 or 8, characterised in that the piston arrangement (1) is provided with means (12) for retaining the inner piston body (7) at at least one intermediate position between the first and second extreme positions.

10. Piston arrangement according to claim 5, 6, 7, 8 or 9, characterised in that the piston body has a rod-shaped handle (13) and is adapted for manual displacement in its longitudinal direction between the two extreme positions.

11. Piston arrangement according to claim 10, characterised in that the piston arrangement (1) is provided with an insertion opening (14) for the rod-shaped handle (13), where the shape of the insertion opening corresponds to the cross-section of the rod-shaped handle, that the rod-shaped handle (13) is designed with at least one narrowed cross-section (15) having the greatest transverse dimension such that the narrowed cross-section (15) may be brought to engage the edge area (16) of the insertion opening by rotating the rod-shaped handle (13) in order to define and retain the rod-shaped handle (13) in at least one of the following: the first extreme position, the second extreme position and the at least one intermediate position.