Adhering Material Detection and Panel Release System

The present invention relates to an adhering material detection and panel release system, and in particular to a system for use in accurately determining (for example detecting and/or mapping) the position of material adhering adjacent the reverse face of a screen or panel to be released or removed.

Vehicle windscreens and/or architectural glass panels may typically be bonded into respective supporting frames or mountings by means of interposed bonding material, conventionally applied as a substantially continuous bead running around and adhering to the periphery of the screen. The bonding material typically comprises a polymeric material (usually a polyurethane resin) which, when cured, secures the screen or panel in place in the frame and provides a watertight seal.

It is sometimes necessary to replace damaged panels or screens, which has in the past typically involved release of the bonded screen or panel by mechanical (cutting) means, followed by the paring back of the bonding material remaining in the frame. A fresh bead of bonding material is subsequently applied and a replacement screen or panel fitted in place.

Recently, "non-invasive" techniques for effecting release of the screen or panel have been proposed. Techniques have

proposed the use of light of sufficient intensity directed through the screen to cause localised degradation of the bonding material at the bonding material/screen interface. The light delivery apparatus is tracked about the periphery of the screen (tracing the path of the bonding bead) to effect complete release of the screen from the frame. An alternative technique utilises a source of ultrasonic energy which is directed through the screen in order to effect localised release, the source similarly being tracked around the screen tracing the path of the bonding bead to cause complete release. Such prior art techniques are disclosed, for example, in WO-A-96/17737 and WO-A- 00/09302.

Both of the "non-invasive" techniques described benefit from accurate knowledge of the positional track of the bonding bead relative to the screen. This is often difficult or impossible to determine visually because a layer of opaque screen print (commonly referred to as a ^λ frit' layer in the automotive glazing art) is typically applied to the screen or panel about its periphery to shield the bonding bead from naturally occurring ultraviolet radiation which could otherwise cause the bonding bead to degrade. Because of the screen print layer the positional track of the bonding bead is hidden from the view through the screen from the windscreen removal technician.

An improved method and apparatus for tracing (tracking, detecting and/or mapping) the location of adhering material has now been devised.

According to a first aspect, the invention provides a method of determining the position of material adhering to the reverse face of a screen or panel, wherein energy is directed through the screen or panel via the obverse face thereof, energy reflected in a direction away from the reverse face of the screen or panel being used to give an indication of the position of the adhering material adjacent the reverse face.

The adhering material is usually present as bonding material, which may comprise a substantially continuous bead, or may, alternatively, comprise an intermittent arrangement comprising a series of spaced discrete deposits of bonding material.

According to a second aspect, the invention provides apparatus for detecting the location of material adhering to the reverse face of a screen or panel, the apparatus comprising transmitter means arranged to direct energy through the screen toward the reverse face and receiver means arranged to receive energy reflected in a direction away from the reverse face of the screen, the receiver means being arranged to produce an output dependent on the reflected energy.

The proportion of the energy reflected from the reverse face of the screen is dependent upon the material in contact therewith. If air only is in contact with the reverse face of the screen, a relatively large proportion of the energy will be reflected from the glass/air interface. If however adhering material is present on the

- A - reverse face at the relevant location, then a significant proportion of the energy is transmitted to, and absorbed by the adhering material. As a consequence a relatively smaller proportion of the energy is reflected to the receiver.

It is therefore preferred that the magnitude or proportion of the energy reflected is sensed to ascertain the presence or absence of material adhered to the reverse face of the screen or panel at a particular location. The receiver means preferably produces an electrical output signal dependent on the magnitude of the reflected signal, which output signal is preferably manipulated by appropriate signal processing and conditioning apparatus to provide a visual, audible or physical indication of the location of the adhering material on the reverse face.

In on embodiment, the output signals may be manipulated to produce a visual output on a display. Alternatively, means may be provided for physically marking the obverse face of the screen or panel directly adjacent the location of the adhering material in response to the reflected energy. This would enable a "map" to be created on the obverse face of the screen or panel which would be easily traceable by a technician using trackable "non-invasive" releasing apparatus. As a further alternative, apparatus according to the invention could be provided in combination with "non-invasive" release apparatus. In this embodiment audible or visual warning means may be provided to provide an indication to the user that the track of the adhering bonding material bead is being accurately traced by the

detection apparatus, and hence accurately tracked by the "non-invasive" release apparatus.

In a yet further embodiment, data relating to the mapped location of the adhering material may be stored using suitable storage means/media (such as computer readable storage means/media) . The "non-invasive" release apparatus may then be computer controlled using the stored data to automatically track the adhering material about the periphery of the screen or panel.

The transmitter is preferably arranged to transmit a pulse of energy. It is preferred that acoustic wave energy (more preferably ultrasonic energy) is utilised for performance of the invention. The transmitter means and receiver means therefore preferably comprise ultrasonic transducer means, a single transducer advantageously acting as transmitter and receiver (although not necessarily utilising the same piezoelectric element to transmit and receive) .

Advantageously a matching or coupling gel is applied in order to improve the coupling of the transmitter with the screen or panel to improve transmission of the ultrasonic energy.

The invention will now be further described in a specific embodiment by way of example only and with reference to the accompanying drawing which is a schematic representation of an exemplary detection system according to the invention.

Referring to the drawing, there is shown a vehicle

laminated windscreen 1 comprising a pair of glass sheets 2,3 separated by an intermediate laminating plastics layer 4. Windscreen 1 is bonded to a vehicle windscreen frame 5 by means of an interposed polyurethane bonding bead 6 which extends around the periphery of the windscreen 1. The reverse face of windscreen 1 is provided with a peripheral ultra-violet barrier comprising a screen print layer 7 arranged to shield bead 6 from naturally occurring ultraviolet radiation. An external rubber seal 8 and internal vehicle trim 9 are provided at the screen I/frame 5 connection for weatherproofing and cosmetic reasons respectively.

In order to use a "non-invasive" screen releasing system (such as a laser or ultrasound screen releasing system) the location of the bonding bead 6 is first mapped. An ultrasonic transducer 20 is placed against the obverse face of the screen 1 and scanned across the peripheral edge; matching or coupling gel may be applied to improve the coupling of the transducer with the windscreen and thereby the transmission of the ultrasonic energy. The transducer 20 acts as an ultrasonic transmitter and receiver (although not necessarily utilising the same piezoelectric crystal) and directs an ultrasound pulse initiated by transmit circuitry 21 into the screen 1. Some time later, an echo is received from the reverse surface of the screen 1; the proportion of the energy reflected (echoing) from the reverse face of the screen 1 is dependent upon the material in contact therewith.

If air only is in contact with the reverse face of the

screen, a relatively large proportion of the energy will be reflected from the glass/air interface. If however bonding material is adhered to the reverse face at the relevant location, then a significant proportion of the energy is transmitted to, and absorbed by the bonding bead 6. As a consequence a relatively smaller proportion of the reflected energy (the echo) is reflected to the transducer 20.

The transducer 20 produces an output signal dependent upon the magnitude of the reflected echo, the signal being passed via amplifier circuitry 22 and analytical and processing circuitry 23 to determine the presence or absence of the bonding bead 6 at the reverse face of the screen for an instantaneous location of the transducer 20. If it is determined that the presence of the bonding bead 6 is detected, then an appropriate output is relayed to output apparatus 24. Output apparatus 24 may be a visual display monitor or, alternatively an audible or visual warning means, or marking apparatus arranged to physically mark the obverse surface of screen 1.

Alternatively, output apparatus 24 may be replaced or augmented by suitable data storage apparatus or media enabling mapping data to be stored for subsequent retrieval and use by "intelligent" non-invasive screen releasing apparatus capable of reading the stored data. As a further alternative output signals from the analytical and processing circuitry 23 could be relayed directly to such "intelligent" screen releasing apparatus to effect almost simultaneous localised screen release as the detection

apparatus and releasing apparatus track together about the screen.

The invention has been described primarily for use in automotive glazing applications. It is however envisaged that the technique would be applicable to other automotive applications such as in relation to bonded body panels or other bonded automotive components.