System for bonding a windshield to a windshield frame

A system for bonding a windshield to a windshield frame, the system comprising: at least one layer of bonding material that bonds the windshield to the windshield frame; at least one heating element embedded in the bonding material; at least one shape memory element formed from a shape memory material embedded in the at least one layer of bonding material in close proximity to the at least one heating element; at least one electrical power source coupled to the at least one heating element; and a controller operable to control the at least one electrical power source to generate current in the at least one heating element to generate heat that softens and weakens the bonding material and causes the at least one shape memory element to transition to a remembered shape that operates to disrupt the bonding layer and free the windshield from the windshield frame.

FIELD

Embodiments of the invention relate to disengaging a windshield from a frame of an armored vehicle.

BACKGROUND

Armored vehicles, are designed and constructed of armored plating to withstand impact of various weapons during combat and to protect a crew operating the vehicle. The use of armored vehicles has long been found outside of professional military forces and are commonly in use for example by civilian police and security forces, various emergency services, escort services, and secure transportation services. Today, it is common to find civilian vehicles heavily armored for protection against acts of tenor, hijacking and robbery. Armored windows also conventionally referred to as “bulletproof glass” or “transparent armor”, constitute a portion of an armored vehicle's armor plating. An armored window is typically constructed of different layers of transparent materials, such as glass and plastic composites having various degrees of elasticity, to form a transparent armored window having high resistance to penetration. Armored windows are thicker and heavier than windows commonly used as windshields in ordinary vehicles and are bonded to a windshield frame of an armored vehicle using a strong layer of adhesive to hold the windshield securely in place. In addition, latches or clips may be used to grab and hold the windshield seated in the windshield frame. When service or repair of an armored windshield is required the windshield is removed from its frame by breaking up and/or otherwise damaging the adhesive using scoring and/or cutting tools and forcefully pulling and/or pushing the windshield out from the frame. Removing the windshield is typically an arduous and time consuming task that may result in damage to the removed windshield and its frame.

SUMMARY

An aspect of an embodiment of the disclosure relates to providing a system, hereinafter also referred to as “popwire system” (“POPSY” or “POPSY system”), for bonding a windshield to a windshield frame of a vehicle that provides for relatively easy removal of the windshield from the windshield frame. Optionally, the windshield is an armored windshield seated in a windshield frame of an armored vehicle.

In accordance with an embodiment of the disclosure, POPSY comprises at least one layer of bonding material configured to bond the windshield to the windshield frame, and embedded in the at least one layer a heating element and at least one shape memory wire and/or ribbon, hereinafter also referred to generically as a “popwire”, formed from a shape memory alloy (SMA) or polymer, hereinafter, generically a SMA material”, in close proximity to the heating element. In an embodiment the at least one popwire comprises a plurality of popwires, each comprising a segment of an SMA material shaped as a wire or ribbon. To remove the windshield from the windshield frame, the heating element is heated to heat the bonding material and the at least one popwire so that the bonding material softens and weakens and the popwire transitions from a martensite phase to an austenite phase. In transitioning to the austenite phase the popwire recovers a remembered shape that generates force that operates to disrupt the at least one layer of adhesive and push the windshield out of the windshield frame.

In an embodiment of the disclosure, POPSY may comprise a controller configured to control and monitor the at least one heating element and maintain temperatures to which it may heat the bonding material and at least one popwire below a temperature at which the bonding material may ignite.

DETAILED DESCRIPTION

In the following detailed description, an overview of a POPSY system installed in an armored vehicle to seal an armored windshield to a windshield frame in the vehicle is discussed with reference toFIG. 1. Details of components of the POPSY shown inFIG. 1are discussed with reference toFIGS. 2A and 2Bwhich show cross-section views of portions of the windshield and windshield frame shown inFIG. 1. InFIGS. 1-2BSMA popwires in the POPSY system are shown in a martensite phase, also referred to as a passive state, in which the popwires do not exert force to disassemble the windshield from its windshield frame. A method of installing a POPSY system in accordance with an embodiment of the disclosure is discussed with reference to a flow diagram shown inFIG. 3. Transition of the popwires from the martensite phase shown inFIGS. 2A and 2Bto an austenite phase in which the popwires change shape to exert force that pushes the windshield out of its windshield frame is discussed with reference toFIGS. 4A and 4Bwhich show the popwires in an austenite phase. Another configuration of a POPSY system installed in an armored vehicle to seal an armored windshield to a windshield frame of the vehicle in accordance with an embodiment are discussed with reference toFIG. 5. Details of features of the POPSY system shown inFIG. 5are shown inFIGS. 6A and 6Band discussed with reference to the figures. Disengagement of the windshield from the windshield is discussed with reference toFIGS. 7A and 7B.

In the discussion, unless otherwise stated, adjectives such as “substantially” and “about” modifying a condition or relationship characteristic of a feature or features of an embodiment of the disclosure, are understood to mean that the condition or characteristic is defined to within tolerances that are acceptable for operation of the embodiment for an application for which it is intended. Unless otherwise indicated, the word “or” in the description and claims is considered to be the inclusive “or” rather than the exclusive or, and indicates at least one of, or any combination of items it conjoins.

FIG. 1schematically shows a perspective view of an armored vehicle100, comprising an armored windshield201that is bonded to a windshield frame202using a POPSY system20in accordance with an embodiment of the disclosure. Windshield201and windshield frame202are shown enlarged in a partially exploded perspective view in an inset150to schematically show elements of POPSY20in accordance with an embodiment. POPSY20may comprise at least one layer of a bonding material indicated by a textured region30having embedded therein at least one heating element40. Optionally, at least one SMA popwire50overlies each of the at least one heating element. A power source22controlled by a controller26configured to provide power to at least one heating element40is connected to the heating element at electrical connection junctions, or lands24. Components of POPSY20and their relationships to windshield201and windshield frame202are shown enlarged inFIGS. 2A and 2B.FIG. 2Aschematically shows a perspective cross-section in a plane indicated by a cross section icon A-A inFIG. 1of windshield201, windshield frame202, and components of POPSY20in accordance with an embodiment.FIG. 2Bschematically shows an enlargement of the cross-section in plane A-A indicated inFIG. 1andFIG. 2A. As shown inFIGS. 2A and 2Bwindshield frame202has an L shaped cross-section profile having a bottom flange203and an edge flange204.

As schematically shown inFIGS. 2A and 2B, at least one heating element40is embedded in the at least one layer of bonding material30, and a plurality of SMA popwires50overlies the at least one heating element. Optionally, at least one bonding layer of bonding material30may comprise a portion31(FIGS. 2A, 2B) that adheres to bottom flange203and a portion32(FIGS. 2A, 2B) that adheres to edge flange204. At least one heating element40may comprise a heating element40embedded in portion31and a heating element40embedded in portion32of bonding material30. In an embodiment, each heating element40is thermally coupled to at least one temperature sensor25(FIG. 2B) configured to provide measurements of temperature of the heating element to which it is thermally coupled, and controller22controls current to heating elements40based on temperature measurements that the sensors provide. Popwires50may be formed having any of various martensite and austenite phase shapes from a suitable SMA alloy such as a nickel-titanium alloy conventionally referred to as nitinol, or a SMA polymer and may be formed in different shapes. For example, the popwires may be ribbon shaped or wire shaped. InFIGS. 1-4Bpopwires are assumed to be ribbon shaped and each popwire is bonded to the heating element40that it overlies by a thermally conducting epoxy layer34(FIG. 2B).

In accordance with an embodiment of the disclosure to remove windshield201from windshield frame202, controller26controls power source22to generate current in heating element40to heat at least one layer30of bonding material to soften and weaken the bonding material and to heat popwires50so that they transition from a martensite phase to an austenite phase. In the austenite phase popwires50distort to assume a remembered shape that operates to generate force that disrupts at least one bonding layer30and forces windshield201out of windshield frame202. InFIGS. 1-4B, popwires50are assumed in the martensite phase to have a flat ribbon shape. In transition to the austenite phase the SMA ribbon shape may, by way of example, morph to assume a wave shape displaced perpendicular to the plane of the ribbon over which it lies as shown inFIGS. 4A and 4Band discussed below.

By way of a numerical example, armored windshield201may be about 70 mm (millimeter) thick and at least one bonding layer30may be between about 3-5 mm thick and comprise any bonding material suitable for bonding an armored glass windshield to a material from which windshield frame202is formed. Typically, windshield frame202is formed from a steel, and the bonding material may be a polyurethane adhesive such as Sikaflex®-265. Ribbon shaped SMA popwires50may be formed from nitinol and have thickness equal to about 1 mm to about 2 mm, width 10 mm and length about 100 mm. Heating elements40embedded in bonding portions31and32of at least one bonding layer30may be continuous ribbons lying substantially along the full lengths of flange203and204respectively. Heating elements40may have thickness between about 0.5 mm and about 2 mm, widths between about 10 and 40 mm, and be formed from be stainless steel such as 303 or 304 stainless steel. Epoxy layers34(FIG. 2B) may be formed from a thermally conducting epoxy such as DP-100 and have thickness between about 0.3 to about 1 mm.

FIG. 3shows a flow diagram300of a procedure by which POPSY20may be assembled to bond an armored windshield to a windshield frame of an armored vehicle, such as vehicle100, in accordance with an embodiment of the disclosure. In a block301surfaces of windshield frame202are cleaned and prepared for receiving bonding material30. In a block303, a first layer of bonding material30is applied to heating elements40. In a box305at least one temperature sensor25is embedded in the first layer of bonding material30so that heating element40contacts the at least one temperature sensor25. In a block306the first layer of bonding material30is left to set for about 12 hours to allow the bonding material to partially harden yet remain tacky, optionally prior to adhering the heating elements and the at least one temperature sensor to surfaces of the windshield frame. In a block307heating elements40and at least one temperature sensor25are adhered to inner surfaces of bottom and side flanges203and204. As schematically shown inFIG. 2A, at least one temperature sensor25is optionally adjacent bottom flange203and adjacent side flange204and heating elements40are located over the temperature sensors. Alternatively, at least one heating element40may be adhered to the bottom or side flange203and204and at least one temperature sensor25located over the heating element. In a block309epoxy layer34is applied to each heating element40and in a block311SMA popwires50are pressed to and bonded to the epoxy layer. In a block313, a second layer of bonding material30is applied to, optionally, substantially encapsulate the first layer of bonding material30, heating elements40and popwires50and provide a thickness of bonding material30between about 1 mm and about 3 mm overlying the popwires. The second layer of bonding material30may be formed from a same or different bonding material as the first bonding material layer. In a block315armored windshield201is seated in windshield frame202to bond to the second layer of bonding material30. In accordance with an embodiment of the disclosure, portions31and32of bonding material30may cover a substantial portion of bottom and edge flanges203and204respectively, to provide relatively sufficient bonding of the windshield to the windshield frame.

It is noted, that whereasFIGS. 2A and 2B, as well asFIGS. 4A and 4Bshow that the adhesive layer that bonds the heating elements to the inside surfaces of the flanges203and204of windshield frame202, cover substantially the entire inside surfaces, embodiments of the disclosure are not limited to an adhesive that covers the entire inside surfaces of the windshield frame, and the adhesive may have various dimensions. By way of example, the adhesive applied to bond the heating element with the surface of the frame may have a width and length substantially congruent with the width and length of a heating element. In an embodiment of the disclosure and after the windshield is bonded to the frame as described in flow diagram300bonding portions31and32may each have a total cross section thickness of about 5 mm. In an embodiment, heating element40are embedded within the bonding material at substantially half way from the surface of the windshield frame to the windshield.

FIG. 4Aschematically, shows perspective cutaway exploded view of a corner of windshield201and portions of POPSY20, after controller26has activated POPSY20to push the windshield out of windshield frame202.FIG. 4Ashows a coordinate system60having x, y and z axes for convenience of referencing positions and orientations of features in the figure.FIG. 4Bshows a cross section of windshield201, frame202and portions of POPSY20after controller26has activated POPSY20to push the windshield out of windshield frame202.

In activating POPSY20, controller26controls power source22to drive current through heating elements40to heat the elements and thereby to heat and weaken bonding layer30and heat popwires50so that they transition to their respective austenite phases. In the austenite phases popwires assume remembered shapes that operate to break up binding layer30and push windshield201out of windshield frame202. In transitioning to the austenite phase, portions of popwires50embedded in bonding portion31along flange203optionally displace substantially perpendicular to bottom flange203in a direction of the z axis (FIG. 4A) of coordinate system60to assume a remembered wavy shape. In transitioning to the austenite phase, portions of popwires50embedded in bonding portion32along flange204optionally displace along the −y-axis of coordinate system60.FIG. 4Bschematically shows popwires50after they have assumed their austenite shapes disrupted bonding portions31and32of at least one bonding layer30and operated to displace windshield201out of windshield frame202.

It is noted that when heating heating elements40, controller26receives signals from temperature sensors25that provide measurements of temperature of the heating elements. The controller operates to control current that power source22generates in the heating elements so that temperature of at least one bonding layer30and popwires50remain within advantageous temperature ranges and do not ignite. It is also noted that whereas popwires50are described as having wavy austenite shapes, practice of embodiments of the disclosure is not limited to wavy shapes, or wavy shapes of the type described. For example, in an embodiment a popwire may transition to a corkscrew shape or simply elongate or contract to assume a lengthened or shortened shape.

FIGS. 5, 6A, 6B, 7A, 7Bschematically show features and operation of another POPSY system420installed in an armored vehicle, such as armored vehicle100inFIG. 1, bonding an armored windshield401to a windshield frame402, in accordance with an embodiment of the disclosure.FIG. 5shows a zoom out view of windshield401, windshield frame402, and POPSY420.FIG. 6Ashows components of POPSY420enlarged in a cutaway, perspective view of a corner of windshield401and windshield frame402within a circle160shown inFIG. 5.FIG. 6Bschematically shows an enlarged cross-section view of the windshield bonded to the windshield frame402in a plane B-B indicated inFIG. 6A. By way of example, as shown inFIGS. 6A-7Barmored windshield401may be formed having a relatively thick body406having thickness “D” (FIG. 6B), and a relatively thin lip405having thickness “C” (FIG. 6B) surrounding the body that is bonded to frame402by a layer of bonding material430having thickness “E” (FIG. 6B). Thickness of body406may be determined based on required impact resistance. Thickness of lip405may be determined so that armored windshield401seats substantially flush with windshield frame401when bonded to the frame by the layer of bonding material430(FIG. 6B, 7B).

In an embodiment, as shown inFIG. 5, POPSY420optionally comprises a single heating element440seated on and running substantially the complete length of a bottom flange403of the windshield frame. Heating element440is formed having a plurality of recesses411in each of which a popwire450is seated. At least one power supply22controlled by a controller426optionally powers heating element440and popwires450. In an embodiment, power supply22is connected to heating element440at a plurality of, optionally four, electrical connection junctions or lands445-1,445-2,445-3, and445-4, generically referred to as lands445. Power supply22may be connected to heating element440so that each segment of the heating element between two lands445that are adjacent to each other along the heating element is electrically connected to the power supply in parallel to the other segments. As a result, if electrical continuity of a segment of heating element440between two adjacent lands445is broken, the heating element can continue to receive power and be heated by power supply22. For example in POPSY420lands445-1and445-3may be connected to a same positive terminal of power supply22and lands445-2and445-4connected to a same negative terminal of power supply22. Connecting segments of heating element440to power supply22in parallel provides advantageous redundancy and robustness to operation of POPSY420. Optionally, temperature in each segment of heating element440is sensed by a different thermal sensor25, schematically shown inFIG. 6Bthat contacts the segment of the heating element. Controller426may control power that at least one power supply22provides heating element440based on signals that sensors25generate responsive to temperatures of segments of heating element440which they respectively contact. In an embodiment, controller426comprises a proportional-integral-derivative (PID) controller (not shown) that receives and processes the signals from thermal sensors25to control power to heating element440and maintain a desired temperature of the heating element.

In an embodiment, POPSY420provides advantageous operational robustness and redundancy by controlling power to popwires450from at least one power supply22via different circuits. For example, popwires in a first group of popwires450comprised in POPSY420may be electrically connected in series to at least one power supply22by a first power line415shown inFIG. 6A, and popwires in a second group of popwires450may be electrically connected in series to at least one power supply22by a second power line416shown inFIG. 6B. Controller426may control power to popwires450connected to power line415independently of power to popwires450connected to second power line416. In an embodiment, controller426comprises first and second PID controllers (not shown). Controller426controls current that at least one power supply22generates in popwires450responsive to signals that the PIDs provide, which measure deviations of currents flowing in first and second power lines415and416respectively from desired currents.

In an embodiment. controller426is configured to pop armored windshield401out from windshield frame402by controlling at least one power supply22to heat heating element440and generating current in the first group of popwires450prior to generating current in the second group of popwires450. In an embodiment, the controller controls current to activate the first group of popwires to generate and exert a relatively large force between the windshield401and frame402that disrupts bonding layer430. Subsequent to initiating current to popwires450in the first group of popwires controller426controls current to activate popwires450in the second group of popwires to displace armored windshield401by a distance sufficient to free the windshield from frame402. For example, the second group of popwires may be activated to displace windshield401by a distance equal to or greater than about D−(E+C).

FIG. 7Aschematically shows the perspective cutaway view of the portion of windshield401, windshield frame402, and POPSY420shown inFIG. 6Afollowing activation of POPSY to pop windshield401out from windshield frame402. As a result of activation, controller426controls power supply22to heat heating element440and drive current through popwires450so that bonding material430softens and deformation of popwires450transitioning to their austenite phase shape ruptures the layer of bonding material430and pops windshield401out of frame402.FIG. 7Ashows schematic perspective views of popwires450in the austenite phase andFIG. 7Bschematically shows a cross section in a plane B-B indicated inFIG. 7Aof the ruptured layer of bonding material30and popped windshield401.

By way of a numerical example, assume that thicknesses C and D of lip405and body406of windshield401as shown inFIG. 6Aare equal to about 6-8 mm and 22 mm and that thickness of bonding material430is equal to about 5 mm. If the windshield has an area of about 2.5 m2the windshield may weigh about 120 kg. Assuming the layer of bonding material is about 5 mm thick and the bonding material is a polyurethane adhesive such as Sikaflex®-265, a force of about 8000 Newtons is required to pop windshield401out of frame402. POPSY420may comprise 16 nitinol popwires450having dimensions equal to about 100 mm×10 mm×2.2 mm. Optionally, the 16 popwires comprise first and second groups of 8 popwires each. Controller426may control at least one power supply22to heat bonding layer430to about 120° C. and excite the popwires450in the first group of popwires to disrupt bonding layer430and excite popwires450in the second group of to displace windshield401by a distance equal to about 10 mm to pop windshield401out of frame402. In an embodiment, exciting popwires450in the first group of popwires comprises pulsing the popwires for 1 second with current of about 300 amps and for about ten seconds thereafter pulsing the popwires at a duty cycle of about 30% with current pulses of 300 amps. Optionally, exciting the popwires in the second group of popwires comprises pulsing the popwires for 2 seconds with a current of about 300 amps and for about ten seconds thereafter pulsing the popwires at a duty cycle of about 50% with current pulses of 300 amps. Operating POPSY420for the noted numerical specifications noted in this paragraph above may pop armored windshield401from frame402in about 15 seconds or less.

Whereas the description above has referred to a POPSY system for bonding a windshield with a windshield frame, embodiments of the invention are not limited to windshields and a POPSY system such as POPSY20or420may be applied for sealing various vehicle apertures such as non-operable side windows and sunroofs and various aperture panels. Optionally POPSY system may be applied to sealing various apertures such as windows or exits of a building.

Descriptions of embodiments of the disclosure in the present application are provided by way of example and are not intended to limit the scope of the disclosure. The described embodiments comprise different features, not all of which are required in all embodiments. Some embodiments utilize only some of the features or possible combinations of the features. Variations of embodiments of the disclosure that are described, and embodiments comprising different combinations of features noted in the described embodiments, will occur to persons of the art. The scope of the invention is limited only by the claims.