Field of the Invention

A piston arrangement for use in repairing damages in laminated glass, preferably a car windscreen, by injecting resin, wherein the piston arrangement includes a first piston body provided displaceable in a boring in an injection tube and having a first piston crown with a piston face adapted for tight-fitting insertion into a packing means in the injection tube, which packing means surrounds a resin chamber, wherein the piston arrangement further includes a second piston body provided displaceable in a casing and having a second piston crown that sealingly bears against the inner side of the casing and forms an inner pressure chamber having a varying volume in dependence of the position of the second piston body in the casing, and wherein an aperture establishing a communication between the resin chamber and the inner pressure chamber is formed in the first piston body. 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. A 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 large 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 applied on an incompressible liquid, very high positive pressures may be attained (> 100 psi ~ 6.8 bar.). 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 bar). 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. In order to remedy the drawbacks of these prior art tools, a tool of the type indicated in the introduction is disclosed in WO 2010/130264. This tool has appeared to be very well suited for repairing 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 can produce 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.

However, it has appeared that in use there is a risk of clogging of the tool due to insufficient care in cleaning when the repair worker has finished the repair procedure. The aperture establishing communication between the resin chamber and the inner pressure chamber is located in the piston face. By lack of cleaning it has therefore appeared that hardened resin will clog the aperture, and therefore the first piston body has to be replaced in order for the tool still to be usable. Object of the Invention

It is the object of the invention to indicate a tool for repairing damages in laminated glass panes where the tool is not associated with the drawback of the prior art tools, and which is easy to clean. The design of the tool makes it suited for repairing both small and large cracks, in particular cracks containing moisture and foreign bodies. In addition, it is an object of the invention that the tool can be used in existing systems for repairing glass panes. Description of the Invention

According to the present invention, this is achieved by a piston arrangement of the type mentioned in the introduction which is peculiar in that sealing means are provided on the first piston body sealing against an inner wall of the boring, and that the aperture is formed in a side wall of the first piston body at a position between the sealing means and the piston face

As the aperture is formed in the side wall of the first piston body at a distance above the piston face, the risk of resin coming in contact with the aperture is very small. The resin chamber is delimited by the piston face and the surrounding packing means, and thus there is no risk of resin penetrating up along the side wall of the first piston body and into the aperture.

If resin is drawn into the aperture, the piston arrangement can easily be cleaned by blowing through with pressurised air.

By the second piston body it is possible by the piston arrangement to establish a second negative pressure in the resin compartment for drawing out moisture and foreign bodies from the damage, the second negative pressure having a maximum value which is greater than a maximum value of the first negative pressure that can be established by the first piston body.

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 can 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 can 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 first piston body in its first extreme position may function as a conventional piston where a positive pressure can be established in the resin compartment such that the resin is pressed in, filling the damage in the glass. This positive pressure has a limited size so as to avoid increasing 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 first piston body is displaced towards its second extreme position, whereby communication is established between the inner pressure chamber and the resin chamber through the aperture, and a second negative pressure is established. The total negative pressure in the resin exceeds what the piston face can produce by itself. Hereby, the negative pressure may be of a size where moisture and foreign bodies are extracted from the damage, and where degassing the resin proceeds rapidly and without requiring time-consuming massage back and forth by the piston face.

By 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 repair 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 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. This packing means of the injection tube 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 first piston body 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 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.

The prestressing force of the injection tube against the glass surface may be ascertained 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 piston arrangement according to 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 a 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. A 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 for drawing out foreign bodies and moisture and for faster degassing. The second negative pressure is achieved by displacing the second piston body in the inner pressure chamber. The volume of the pressure chamber is determined by the disposition of the second piston body. In the first extreme position of the second piston body the volume of the pressure chamber is the least, and in the second extreme position of the second piston body the volume of the pressure chamber is the greatest. The piston arrangement is typically designed with a cylindrical cavity in which the second piston body is arranged with a packing means. The packing means is adapted to fit tightly against the inner side of the cylindrical cavity under longitudinal displacement of the piston body, for establishing a pressure chamber. In an alternative embodiment, the piston arrangement is formed by a casing 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 piston arrangement. Hereby is achieved adaptation of the piston arrangement in a particularly simple way whereby secure tightness is achieved as 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. During the use of the tool, 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, only a limited number of repetitions are required 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. By a piston arrangement according to the invention there is used a lesser amount of resin that in prior art systems. By the new tool there is thus only used 0.15 ml resin as compared with prior art tools where 0.20 ml is used. The piston arrangement according to the invention thus enables a saving of consumed material by a repair procedure.

For making a piston arrangement according to the invention there may be used a combination of plastic and aluminium. Other metals than aluminium can be applied.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that the communication between the resin chamber and the inner pressure chamber is interrupted when the piston body is in a first extreme position where it is pressed to the bottom of the injection tube, and that the communication is established when the first piston body is displaced from a first extreme position at such a distance so that the piston face is brought out of the tight-fitting insertion into the packing means.

By this embodiment it is possible that the first positive pressure is provided by the first piston body whereby resin can be pressed into a damage. When the first piston body is displaced such that the piston face is brought out of the tight-fitting engagement, there is established communication so that the second piston body can be used for establishing a vacuum for drawing out moisture and air from the damage. 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 internal screw thread in the injection tube.

By using a threaded connection a particularly simple design is achieved. As the piston arrangement according to the invention has a screw thread corresponding to the internal thread in the injection tube, the above mentioned advantage by using the piston arrangement is achieved by a system of the type disclosed in US 3,993,520.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that the first piston body has a reduced diameter in an area between the aperture and the piston face.

By this embodiment there is established an annular communication duct between the first piston body and the injection tube in a simple way. This will ensure the possibility of communication between the pressure chamber and the resin chamber.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that the sealing means include at least one and preferably two O-rings. An O-ring is a very well suited sealing means. However, other types of packings may be used as well. According to a further embodiment, the piston arrangement according to the invention is peculiar in that a visual indication is provided on the first piston body, showing that the piston face is brought out of the tight-fitting insertion into the packing means. The operator will know by the visual indication that the tight-fitting engagement between the piston face and the packing means is finished, and that hereby it is possible to use the second piston for establishing a negative pressure.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that the external screw thread of the piston arrangement is provided on the first piston body.

It is ensured hereby that the assembled piston arrangement can be screwed into the injection tube in a prior art system.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that the visual indication is a coloured ring on the external screw thread of the first piston body, and that this is disposed such that it becomes visible outside the injection tube when the piston face is brought out of the tight-fitting insertion into the packing means.

The visual indication can be established very easily in that an annular area is provided with a colour marking. When this is provided on the external screw thread of the first piston body, it can be ensured that the thread is still in engagement with the internal screw thread in the injection tube. The various parts of the piston arrangement will therefore not be brought out of engagement with each other.

According to a further embodiment, the piston arrangement according to the invention is peculiar in that the casing of the piston arrangement and the first piston body are releasably interconnected.

By this design it will be possible to use a separate tool, e.g. a disposable syringe, for establishing the second piston body. The disposable syringe can easily be replaced in case of wear. Since the first piston body is typically made of metal, it will not be subjected to wear in the same way as will be the case of the second piston body, if this is a disposable syringe. Hereby is achieved a reasonably priced product and at the same time a product where tightness between valve body and casing can be established in a secure way.

Description of the Drawing

The invention will be explained in more detail below with reference to the accompanying drawing, where:

Fig. 1 shows sectional views through a tool known from US 3,993,520;

Fig. 2 shows a sectional view of the support tool, the injection tube and the piston arrangement, which are known from WO 2010/130264;

Fig. 3 shows a view of an embodiment of a piston arrangement according to the invention, shown with the parts of the piston arrangement in exploded view; Fig. 4 is a view of the embodiment shown in Fig. 3 for the piston arrangement with the parts assembled and ready for use;

Fig. 5 is a sectional view of the embodiment of the piston arrangement according to the invention shown in Figs. 3 and 4;

Fig. 6 shows the piston arrangement of Fig. 5 as seen from the side;

Fig. 7 is an enlarged detail of the piston arrangement shown in Fig. 5. Detailed Description of Embodiments of the Invention

In 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.

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 33A with the glass surface above the damage 11A 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 a 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 a 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 aperture 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. 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.

In Figs. 3-7 are shown a piston arrangement operating according to the same principle as the piston arrangement shown in Fig. 2. When the piston body 7 is displaced from the first extreme position towards the second extreme position, it becomes possible to establish a negative pressure in the resin chamber 5 of a size that is impossible to achieve by the piston according to the technique known from US 3,993,520.

In Figs. 3 and 4 appear views of an embodiment of a piston arrangement which is shown in disassembled and assembled conditions, respectively. The piston arrangement has an injection tube 4 corresponding to the one shown in Fig. 2. This includes a packing means 3 forming a resin chamber 5 that is delimited by the piston face 2 on the first piston body 32. The first piston body 32 is provided with the piston face 2 at a first piston crown 33 provided for tight-fitting insertion into the packing means 3. The second piston body 7 is provided displaceable in the casing 22 and has a second piston crown 35 which bears sealingly against the inner side of the casing 22. The pressure chamber 6 is hereby formed with varying volume that depends on the position of the second piston body in the casing.

In this embodiment, there is established an aperture 8 in a side wall of the first piston body 32. The first piston body 32 is provided with sealing means 34 in the form of O- rings that seal against an inner wall 36 of the injection tube 4.

The aperture 8, which communicates with an internal duct (described below in connection with Figs. 5-7), is formed in the side wall at a position between the sealing means 34 and the piston face 2. The apertures 8 are thus provided spaced apart from the piston face that delimits the resin chamber.

In an area 38 between the aperture 8 and the piston face 2, the first piston body 32 has reduced diameter in relation to the diameter of the part of the first piston body 32 on which the sealing means 34 are mounted. Thus there is formed an annular chamber between the piston body 32 and the internal duct 36 in the area 38. A visual indication 37 is formed on the first piston body 32. In a flange 39 on the first piston body 32 there is formed an aperture 40 for receiving a point 41 of a disposable syringe which provides the second piston body 7.

In Figs. 5-7 are shown sectional views and a side view of the piston arrangement shown in Figs. 3 and 4. Identical or corresponding elements will therefore not be explained in detail in connection with these figures.

It appears on Figs. 5-7 that the aperture 8 in the first piston body 32 communicates with an internal duct 42. The internal duct is connected with a boring 43 at the collar 40. The boring 43 can receive the point 41 of the disposable syringe. In the area 38 and together with an inner surface 44 of the injection tube, the first piston body 32 will form an annular chamber 45 that forms a communication between the aperture 8 and the resin chamber when the first piston body 32 is screwed to an extreme position as shown in Figs. 5-7.

The sealing means 34 are disposed at a position above the aperture 8, and will therefore ensure that the connection established via the annular chamber 45, the aperture 8 and the duct 42 form an airtight communication between the resin chamber 5 and the pressure chamber 6.

As seen from the Figures, between the piston face 2 delimiting the resin chamber 5 and the aperture 8 there will be a spacing corresponding to the height of the area 38. There is thus a very limited risk that resin will penetrate up through the annular chamber 45 and contaminate the aperture 8.

During use, if a situation arises where resin has penetrated into the aperture 8 and the duct 42, the piston arrangement can be blown clean very easily by pressurised air. When the first piston body 32 is screwed off the injection tube 4, and when the second piston body 7 is released, it will be very simple to blow pressurised air into the boring 43 and to remove any resin that is present in the duct 42 and the aperture 8, respectively.