The present invention relates to methods and apparatus for bonding components under pressure. It is concerned particularly, although not exclusively, with bonding a translucent or transparent glass panel to a metal supporting frame to form a door for a large-scale electronic display.

In the context of this specification, "large-scale" means, in relation to a large-scale electronic display, a minimum visible screen size of approximately 50 inches (127 cm), measured diagonally across the screen.

Electronic advertising displays are being used increasingly at the present time. They are now being used in outdoor as well as indoor venues; in locations such as traditional roadside and city centre billboard locations, travel

environments (e.g. rail platforms, airports, bus stops, trams, underground rail), retail environments (e.g. shopping malls, supermarkets, petrol stations), entertainment venues (e.g. stadiums, arenas, cinemas, restaurants, bars) and typically any location where advertisers can reach large audiences as they go about their day to day business.

Such displays are typically large— e.g. high-brightness 70 inch (178 cm) or more visible screens that can be viewed by a mass audience from a distance— and very heavy. Such displays typically have a requirement to attach or bond a protective glass panel to metal framework so that an LCD (or other type) screen of the display can be viewed and protected from vandalism and weather.

Many displays do not provide access at the front of the display, which means that the glass can be bonded or otherwise fixed to the metal framework without a requirement for opening the front of the display— e.g. the inside of the display is accessed from the rear of the display. However, there are benefits to accessing the inside of the display from the front of the display— for example, to facilitate servicing.

If a display is provided with a "glass bonded to metal" opening front door, opening and closing the door can put additional stress on the glass— particularly if there are pressure points built up within the glass that are susceptible to movement, twist, heat, cold etc. Fractures in the bond and glass can occur as a result of spot weakness in pressure points under these various conditions. It is known that bonding glass to a metal frame / door can be achieved in a number of ways:-

Mechanical— mechanical fixings such as bolts are provided to apply pressure around the metal frame to fix the glass to the metal;

Adhesive— a layer of adhesive is provided between the glass and the metal;

Tape— strips of industrial adhesive tape are provided around the metal frame to bond to the glass.

The key issue with all these methods is to achieve a consistent pressure across the full surface of the bond between the glass and the metal frame as a whole, to eliminate any spot or localised pressure points that can manifest as weaknesses under door usage (e.g. twist, movement, closing forces) and weather conditions (heat, cold, frost, solar loading). There is a need to remove or eliminate air pockets that can expand or compress under such conditions— especially as the door flexes when opened and closed. This is a key requirement for achieving a field serviceable product. In manufacture, sufficient and even pressure needs to be applied to eliminate spot weaknesses as above, in a way that does not mark or damage the glass, which is also susceptible to damage by the application of pressure, force, heat, etc. All of the above known methods are susceptible to issues as above— e.g.

Mechanical— it can be difficult to get a consistent pressure across the bond as a whole where studs, clips, brackets, etc. naturally form localised pressure points around fixing points;

Adhesive— control of the thickness of the adhesive may be difficult, typically where stand offs (used to control adhesive thickness) provide local pressure points and air pockets or bubbles form within the adhesive bond area;

Tape— although this has the advantage of providing a dedicated thickness for a specific pressure, it is difficult to control the applied pressure on a consistent basis across the bond area as a whole (i.e. the entire border of the frame around the glass) in a way that can be applied easily and safely for large scale manufacturing operations without damaging or marking the glass.

The bond of the glass and the metal frame has to provide sufficient rigidity in the bonded glass door (as a complete unit) for day to day operations of opening, closing and flexing of the bonded glass door structure.

Preferred embodiments of the present invention aim to provide methods and apparatus for bonding a glass panel to a metal frame that may be generally improved in the foregoing respects. According to one aspect of the present invention, there is provided a method of bonding first and second components, comprising the step of compressing the two components together by a device comprising one or more first wheel that applies pressure to an outer surface of the first component and one or more second wheel that applies pressure to an outer surface of the second component, such that the device travels along the first and second components with movement of the first and second wheels, the device further comprising one or more actuator that urges said first wheel(s) and second wheel(s) together in order to compress the two components together and facilitate bonding therebetween, wherein the first and second wheels apply pressure to only a partial region of the outer surfaces of the two components.

The term 'wheel' encompasses any wheel, roller or equivalent that rotates to facilitate movement of the device along the two components whilst applying pressure to them. The wheels may apply pressure to the first and second components directly or via one or more element between one or more of the wheels and one or more of the components.

Preferably, the device travels along an edge region of the first and second components in order to compress the two components together along said edge region.

Preferably, an adhesive is applied between the first and second components, prior to compression by said device.

Preferably, said adhesive is an adhesive tape. Preferably, said adhesive tape is of double-sided closed-cell foam construction with a viscoelastic acrylic core.

Preferably, said device provides an even and consistent pressure across the full width of the adhesive compressed between the two components. Preferably, said first component is a translucent or transparent panel and said second component is a frame that supports the panel.

Preferably, said panel is of glass.

Preferably, said frame is of metal.

A method as above may comprise the steps of applying adhesive to the panel and/ or the frame, bringing the panel and frame together with the adhesive therebetween so that they are bonded together by the adhesive, and applying pressure by said device to compress the panel and frame together with the adhesive therebetween, such that the device travels along an edge region of the panel and frame with movement of the first and second wheels. Such a method may comprise the subsequent step of fitting the panel and frame to the housing of a large-scale electronic display, to serve as a door for said housing.

Bonding between the first and second components may be effected by thermal bonding or ultrasonic welding. Preferably, said device further comprises one or more third wheel that is mounted orthogonally to said first and second wheels and engages a surface to position the device with respect to said first and second components. Preferably, one or more of said first and second wheels applies pressure to said components via one or more element between one or more of said first and second wheels and one or more of said components.

Preferably, one of said components is supported on a first face of a table that provides a second surface with which the or each said second wheel engages.

Preferably, said table affords a third surface that joins said first and second surfaces and said device comprises one or more third wheel that engages said third surface to position the device with respect to said table. Preferably, the or each said second wheel and said second surface are provided with one or more interengaging rib and groove.

A method as above may be of particular advantage where said first and second components when assembled together form a non-planar assembly.

Said device may be moved relative to said two components by a human operator or by a robot.

In another aspect of the invention, a device for use in bonding first and second components comprises one or more first wheel that, in use, applies pressure to an outer surface of the first component and one or more second wheel that, in use, applies pressure to an outer surface of the second component, such that the device travels along the two components with movement of the first and second wheels, the device further comprising one or more actuator that is arranged to urge said first wheel(s) and second wheel(s) together in order to compress the two components together and facilitate bonding therebetween. Preferably, said first and second wheels are mounted on a common chassis of the device that is arranged to be moved along an edge region of the first and second components.

Preferably, said chassis is arranged to be moved manually along the edge region of the first and second components.

Alternatively, a driving mechanism may be arranged to drive said chassis along an edge region of the first and second components.

Preferably, the or each said actuator is operated pneumatically or hydraulically. Alternatively, the or each said actuator may be operated electrically or mechanically.

A device as above may further comprise one or more user key arranged to control operation of one or more said actuator.

A device as above may further comprise one or more third wheel that is mounted orthogonally to said first and second wheels and is arranged to engage a surface to position the device with respect to said first and second

components.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

Figure 1 is a perspective view of a large-scale electronic display; Figure 2 is a side view of the display of Figure 1, showing a front door in an open position;

Figure 3 is an exploded perspective view of a precision table, a metal frame, a glass panel and a glass bonding jig; Figure 4 is a perspective view similar to Figure 3 but showing the respective parts in an operative position;

Figure 5 is a perspective view of the glass bonding jig from the front and one side;

Figure 6 is a perspective view of the glass bonding jig from the front and above;

Figure 7 is a perspective view of the glass bonding jig from the rear and opposite side, in position with the metal frame and glass panel on the precision table, but not fully engaged in an operative condition;

Figure 8 is a view similar to Figure 7 but with the glass bonding jig fully engaged in an operative condition;

Figure 9 is a perspective view of the glass bonding jig from the front, above and one side, fully engaged with the glass panel and the precision table in an operative condition;

Figure 10 is a perspective view of the glass bonding jig from the one side and slightly below, fully engaged with the glass panel and the precision table; Figure 11 is a schematic diagram to illustrate operation of the glass bonding jig;

Figure 12 is a perspective detail view showing pneumatic valves of the glass bonding jig and connections thereto; Figure 13 is another perspective view of the detail of Figure 12, viewed from below, showing pneumatic valves of the glass bonding jig and connections thereto; and

Figure 14 is a schematic view of a bonding jig used for ultrasonic welding of two components under pressure. In the figures, like references denote like or corresponding parts.

It is to be understood that the various features that are described in the following and/ or illustrated in the drawings are preferred but not essential.

Combinations of features described and/ or illustrated are not considered to be the only possible combinations. Unless stated to the contrary, individual features may be omitted, varied or combined in different combinations, where practical.

The large-scale electronic display 100 that is shown in Figure 1 is mounted on a plinth 210 by brackets 211 that are largely covered by claddings 208, 209. As shown in Figure 2, the display 100 has a front door 913 that opens by pivoting upwardly. An LCD panel 915 is supported by the front door 913 and, as shown, hangs downwardly from it. The front door 913 comprises glass that is bonded to a metal frame. An example of a method of bonding the glass to the frame will now be described. Figures 3 and 4 show a transparent glass panel 1500 above a metal frame 1501, with high-strength bonding tape 1510 bonding the glass panel 1500 and metal frame 1501 together. In this example, the glass panel 1500 is a sheet of substantially uniform thickness, affording a flat outer surface on both sides of the sheet. The metal frame 1501 is of rectangular shape and defines a central, rectangular aperture 1525. The frame 1501 forms a substantially flat border around the rectangular aperture 1525, the border affording a flat outer surface on both sides of the frame 1501. The frame 1501 has a flange 1528 that extends at right angles to the flat border, around the aperture 1525. The metal frame 1501 is supported on a precision table 1502, which provides a highly accurate hori2ontal surface on which the metal frame 1501 rests. The metal frame 1501 may engage with recesses or abutment surfaces on the precision table 1502, for example by way of the flange 1528, in order to position the frame 1501 accurately with respect to the table 1502. A device in the form of a glass bonding jig 1503 is provided, to ensure a high quality of bonding between the glass panel 1500 and the metal frame 1501.

As may be seen in Figures 5 and 6, the glass bonding jig 1503 comprises a chassis 1520 of tubular metal or other strong material, at the top of which are mounted two pairs of first, polyurethane wheels 1504, each mounted for free rotation about a horizontal axis. At the bottom of the chassis 1520, there is mounted a further pair of second, polyurethane wheels 1506, which are located below the first, upper wheels 1504 and are also mounted for free rotation about a horizontal axis. Each of the second wheels 1506 is formed with an annular rib 1521 for engagement in a corresponding groove in an under face of the precision table 1502.

A pair of third, polyurethane wheels 1505 are mounted for free rotation about a vertical axis. The second and third wheels 1506, 1505 are also arranged for movement upwardly and downwardly, as seen in the figures, by way of a pneumatic ram 1514.

Reference 1507 shows a pneumatic air intake and 1508 (Figures 11 and 12) shows a pneumatic air output. Control buttons 1509 control operation of the pneumatic ram 1514 by way of pneumatic valves 1512. 1513 denotes a ram cylinder, with air flow apertures 1516, 1517 at the top (1516) and the bottom (1517) of the cylinder 1513. 1515 shows a plate on which the second and third wheels 1506, 1505 are mounted, and which travels upwardly and downwardly with the ram 1514. 1518 denotes compressed air intakes for the valves 1512. 1519 (Figure 13) denotes a compressed air input bar that feeds compressed air to the compressed air intakes 1518 of the valves 1512, by means of suitable tubing (not shown).

The glass bonding jig 1503 is intended for manual use, such that it may readily be positioned and operated where needed. The tubular metal chassis 1520 is convenient to hold, the upper parts 1522 of the chassis affording handle portions where the jig 1503 can be conveniently held and operated, with the control buttons 1509 in easy reach. As may be seen in the figures, the chassis 1520 comprises two tubular parts that are joined together at the bottom of the jig 1503, adjacent the cylinder 1513, and extend upwardly and away from each other to support the two spaced pairs of upper wheels 1504. As may be seen in Figure 10, the chassis 1503 is generally C-shaped in side view, with the upper wheels 1504 positioned above the lower wheels 1506 and in the same vertical plane. The spacing between the two pairs of upper wheels 1504 is significantly greater than that between the two lower wheels 1506, which is the same as that between the two side wheels 1505. Figure 7 shows the glass bonding jig 1503 in position around the periphery or edge region of the glass panel 1500 and metal frame 1501, supported on the precision table 1502. The first wheels 1504 rest on the upper surface of the glass panel 1500. However, in Figure 7, the ram 1514 is lowered so that the second wheels 1506 do not engage the under face of the precision table 1502 and therefore no pressure is applied to the glass panel 1500 and metal frame 1501.

In Figure 8, the ram 1514 is raised so that the second wheels 1506 engage the under face of the precision table 1502 and, at the same time, the third wheels 1505 engage the outer face of the precision table 1502. This 'engaged' condition of the glass bonding jig 1503 is shown also in the views of Figures 9 and 10. In particular, Figure 10 shows the annular rib 1521 on one of the second wheels 1506 engaging in a corresponding groove 1511 formed in the underside of the precision table 1502. The interengaging rib 1521 and groove 1511 provide positive location of the glass bonding jig 1503 with respect to the precision table 1502. In a variant, the second wheels 1506 may be formed with annular grooves to receive one or more interengaging rib on the underside of the precision table 1502.

Figure 11 illustrates pneumatic control of the ram 1514. Compressed air is supplied at intake 1507 to the input bar 1519, which feeds the compressed air to both Button 1 and Button 2. In the condition illustrated, both buttons are released, such that Button 2 vents the top of the cylinder 1513 to atmosphere via port 2 and Button 1 feeds compressed air via port 2 (reference 1518) to the lower part of cylinder 1513. This causes the ram 1514 to be raised. When both buttons are pressed, they connect to the respective ports 1, such that Button 1 now vents the lower part of the cylinder 1513 to atmosphere and Button 2 feeds compressed air via port 1 (reference 1518) to the upper part of the cylinder 1513, to lower the ram 1514.

Figures 12 and 13 show further details of the valves 1512 and their connections. To bond the glass panel 1500 to the metal frame 1501, the glass and metal surfaces are firstly cleaned from dirt, grease, contaminants, etc, to provide a clean bond area for the adhesive tape 1510. The frame 1501 is placed on the precision table 1502. The adhesive tape 1510 is then applied to the metal frame 1501. The glass panel 1500 is then lowered carefully onto the adhesive tape 1510, so that the glass panel 1500 and the metal frame 1501 are brought together and initially bonded together by the adhesive tape 1510.

With the buttons 1509 depressed and the ram 1514 lowered, the glass bonding jig 1503 is then positioned carefully at one side of the initially bonded glass panel 1500 and frame 1501, with the first rollers 1504 resting on top of the glass panel 1500 and the third rollers 1505 engaging a side surface of the precision table 1502, in which position the annular ribs 1521 on the second wheels 1506 are positioned below the respective grooves 1511 in the underside of the precision table 1502.

The buttons 1509 are then released, to cause the ram 1514 to be raised and thereby urge the second wheels 1506 firmly into engagement with the underside of the precision table 1502. As the first wheels 1504 are initially resting on the upper surface of the glass panel 1500, this causes the first and second wheels to be urged together and thereby compress the glass panel 1500 and metal frame 1501 together, with the adhesive tape 1510 therebetween. The glass bonding jig 1503 can provide an even and consistent pressure at a high force— e.g. 1500 Newtons— across the full width of the tape 1510 compressed between the glass panel 1500 and metal frame 1501. The jig 1503 can readily be moved along the perimeter of the glass panel 1500, with movement of the first, second and third wheels 1504, 1506, 1505, such that the even and consistent pressure may be applied along the entire perimeter of the glass panel 1500 and metal frame 1501. The jig 1503 may readily be moved by hand, although automated movement is possible.

By controlling the applied air pressure, which determines the force by which the first and second wheels 1504, 1506 are urged together, a controlled force may be applied to the glass panel 1500 and metal frame 1501, to achieve the desired thickness of adhesive bonding tape 1510 therebetween. The greater the applied force, the thinner the thickness of tape 1510 as it is squee2ed between the glass panel 1500 and metal frame 1501. An industrial-strength tape is preferred as the adhesive tape 1510. An example of such tape is VHB® tape, sold by 3M Corporation, to provide a Very High Bond. It is of double-sided closed-cell foam construction with a viscoelastic acrylic core.

The use of polyurethane in the wheels 1504, 1506 helps to clamp the construction either side of the bond in a way that the wheel material does not cause marking or damage to the glass panel 1500, and also allows the jig 1503 to roll easily across the glass or metal surface to achieve a consistent bond around the perimeter of the glass panel.

Air pockets or bubbles can readily be squee2ed out as the jig 1503 is moved along the perimeter of the glass panel 1500, avoiding localised pressure points in the bond formed by the tape 1510. Once cured, any flexing of the door comprising the glass panel 1500 and metal frame 1501 is thus applied across the bond as whole, avoiding the problems and issues raised earlier.

The precision table holds the glass 1500, tape 1510 and metal frame 1502 in place whilst the bond is made, providing a flat surface and sides of the table that control the position of the jig 1503 to ensure that pressure is applied directly over the bond area defined by the tape 1510.

The shape of the jig 1503, the guidance provided by the third jig wheels 1505 and the "channelling" of the second jig wheels 1506 into table tracks 1511 provides directional control.

When air pressure is applied, forcing high pressure directly across the bond, the jig 1503 can be moved simply and manually from side to side by hand — and the jig can 1503 easily be released to repeat the process on all sides of the glass panel 1500. The precision table 1502 holds the bonded glass door in place for a period of time whilst the bond afforded by the tape cures. Once cured, any gap at the edges between metal frame 1501 and glass panel 1500 can readily be sealed with weatherproof sealant.

Whilst the above-described example of the invention utilises pneumatic power for an actuator to urge the upper and lower wheels together, hydraulic power may alternatively be employed. As another alternative, an electrical actuator may be used— e.g. using a motor and screw feed or an electromagnetic device. A mechanical actuator might also be used— for example, using a mechanical lever and spring. Whilst the above-described example of the invention utilises an adhesive tape, it is possible to employ adhesive applied in an alternative manner.

The above-described example of the invention shows a transparent glass panel bonded to a metal supporting frame. However, the glass may be translucent instead of transparent or indeed may be opaque - for example, to provide a matching rear panel of a display housing. A bonded panel and frame may be used for displays of any size— e.g. for any display that requires environmental or other protection, such as a screen at the entrance of a store in a shopping centre. Other materials than glass may be used— e.g. plastics (PVC, acrylic, polycarbonate etc), as well as metal or other materials. In general, the two components to be bonded together may be of any materials suitable for the bonding process. The supporting frame may be of plastics and/ or composite materials.

It is particularly convenient that the jig 1503 is moved by hand around an edge region of the glass panel 1500 and metal frame 1501 to effect bonding, since the flange 1528 on the frame 1501 extends at a right angle to the flat border that the frame 1501 provides and therefore it is not practical to feed the full width of the glass panel 1500 and metal frame 1501 between compression rollers, as the assembly of the components 1500, 1501 is non-planar. The manually operated jig 1503 may apply pressure to the components 1500, 1501 where required, around their edge region, and readily manoeuvred to avoid any obstructions. However, as indicated above, it is feasible for the jig 1503 to be driven along a predetermined path for repetitive bonding of identical parts— for example, by a production robot rather than by a human operator. If the reach of the jig 1503 is extended— that is, if the upper wheels

1504 and lower wheel/ram assembly 1505, 1506, 1513, 1514 are disposed at a greater distance from the side of the chassis 1520 where the control buttons 1509 and valves 1512 are located— the jig 1503 may be used to provide bonding in a limited or partial region of the panel 1500 and frame 1501 that is spaced from their outer edges. Figure 14 illustrates a bonding jig 1503 that is similar to that illustrated in the preceding figures and described above and, in Figure 14, like reference numerals denote like or corresponding parts. Thus, the jig 1503 has a frame or chassis 1520 on which one or more upper wheel 1504 and one or more lower wheel 1506 are mounted, with a pneumatic cylinder 1513 and ram 1514 to urge the upper and lower wheels 1504, 1506 together in order to compress together a first component 1600 and a second component 1601, in order to facilitate bonding between the two components 1600, 1601.

However, in the configuration of Figure 14, the two components 1600, 1601 are bonded together by ultrasonic welding rather than by adhesive tape. To this end, an ultrasonic generator 1550 delivers an ultrasonic signal to a transducer 1555 that forms or is part of a core of the upper wheel 1504. In this

arrangement, the upper wheel 1504 may be of metal and serve as a sonotrode for the ultrasonic welding process. The lower wheel 1506 may also be of metal.

Ultrasonic welding is particularly suitable for the bonding of plastics materials, although it can also be used for bonding metals. In this example, both of the components 1600, 1601 are of plastics. The jig 1503 is moved manually (or driven) along an edge region of the components 1600, 1601 with movement of the upper and lower wheels 1504, 1506. The components 1600, 1601 are bonded together by ultrasonic welding as the jig 1503 is moved along their edge region. In Figure 14, the components 1600, 1601 are not shown supported on a table (such as the precision table 1502 of the preceding figures), but a supporting table or other structure may be provided for the components 1600, 1601, and it may be positioned between the upper and lower wheels 1504, 1506. In a modification of the option shown in Figure 14, the components

1600, 1601 may be thermally bonded together by means other than ultrasonic welding— e.g. by heat that is applied via the wheels 1504, 1506, which are of metal or other suitable heat-conducting material and incorporate heating elements. Whilst opposing faces of the glass panel 1500 and metal frame 1501 are flat in the above example, they could be formed with complementary ribs and grooves with adhesive therebetween.

In this specification, the verb "comprise" has its normal dictionary meaning, to denote non-exclusive inclusion. That is, use of the word "comprise" (or any of its derivatives) to include one feature or more, does not exclude the possibility of also including further features. The word "preferable" (or any of its derivatives) indicates one feature or more that is preferred but not essential.

All or any of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/ or all or any of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/ or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing

embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.