GB2185935A - Prepressing laminates - Google Patents

Abstract

An apparatus (10) for prepressing an assembly (13) of stacked, superimposed glass and plastic sheets for subsequent autoclave lamination to provide a glazing, includes a frame (30) positioned between a delivery conveyor (11) and a discharge conveyor (12) and carrying prepress (35) and support rollers (44). An assembly arrives on the delivery conveyor and is aligned and rotated ninety degrees before entry into the frame. The prepress rollers are rotatably mounted in pairs and attached to air cylinders (40) which retract the rollers during entry to clear a vacuum ring (25) which extends about the peripheral edge of the assembly such that a vacuum can be drawn on the assembly during the application of pressure and then extend the rollers into contact with an upper surface of the assembly to apply pressure thereto. The assembly is supported from its bottom side by the support rollers which are rotatably attached to the frame and are located on either side of a plurality of drive rollers (47) which are rotatably attached to the frame in pairs. The drive rollers are of different diameters and are adjustably mounted on an axis of rotation which is tilted from the horizontal path of the assembly. <IMAGE>

Description

SPECIFICATION Prepress apparatus and method The present invention relates generally to the production of laminated glass sheets and, more specifically, to an improved apparatus for prepressing antilacerative or laceration shield type glazings particularly adapted for use in automotive vehicles.

In the early stages of the automobile industry, single sheets of ordinary glass were employed as windshields. As it became evident that this type of windshield presented a considerable safety hazard, the single sheets of ordinary glass were replaced with single sheets of heat treated ortempered glass.

Thereafter, as laminated safety glass was developed to reduce the severity of lacerative injuries, its use in automotive windshields greatly increased until today, when almost all automotive windshields are constructed of sometype of laminated glass.

Typically, laminated glass of the type utilized in vehicle windshields consists of two sheets ofglass bonded together with a thin plastic interlayer, such as a sheet of polyvinyl butyral, for example. In the eventofan impact on a laminated glasswindshield sufficient to break the glass, the plastic interlayer functions to bind the glass fragments together, thus reducing the riskofinjurytoadriverorpassengeras a result of flying glass or contact with the windshield.

Further developments with this type of laminated glass, such as those disclosed in United States Patent No.3,231,461, have resulted in laminated windshields with improved penetration resistance.

Consequently, with the ever growing recognition of the necessity for increased safety precautions, continuing efforts have been and are still being madeto appreciably reducethe injury producing potential of automobile windshields.

Recently, it has been found that the addition of a second plastic layer bonded to the inner glass sur face of the laminated windshield further increases the safety effectiveness of the windshield. This second plastic layer has typically been termed a protective laceration inhibiting shield since it has been found that the additional plastic layer will appreciably reduce the number and severity of lacerative injuries to persons thrown against the windshield under all impact conditions.Further, it has been found that the laceration shield, when produced under certain conditions of manufacture, improves the ability of the laminated windshield to decelerate movement of a personthrownagainstthewind- shield, while also increasing the penetration resistance of the windshield as compared to conventional laminated windshields. Also, the laceration shield re ducestheamountofflying glass and thus the injury to car occupants as a result of objects that may be thrown against the windshield from overpass or elsewhere outside the vehicle.

An example of an automotive windshield which incorporates, as part of its laminated structure, a protective laceration shield bonded to its inboard glass surface is disclosed in United States Patent No.

4,242,403. In this patent, the laceration shield includes a penetration resisting multi-layerbodyconsist- ing of an inner layer of relatively soft, extensible plastic material such as polyvinyl butyral, for example, which is adhered to the inboard surface of the windshield, an intermediate layer of more durable plastic such as polyester, and an outer coating of an abrasion resistant material.

While the effectiveness of a laminated windshield having a laceration shield is obvious, very few vehicles utilize such a windshield. The chief reason forthis limited use has been the difficulty experience in trying to manufacture a windshield with a laceration shield on a production basis. In the automotive industry,the standard forwindshields isvery high, especially as to optical qualities, and it has been very difficultto manufactureawindshield having a laceration shield which is free of optical defects. Even when the individual sheets ofthe laminated assembly are free from optical defects before bonding them together, it is difficult to join them and preservethe optical qualities.

One method for applying a plastic layer to one surface of a single sheet of glass is disclosed in United States Patent No. 3,806,387. In this method, a sheet of glass, a layer of adhesive, and a layer of th i n trans- parent plastic sheeting are assembled in a stackto produce an assembly for subsequent lamination. A second sheet of glass (called a glass cover orforming sheet) conforming to the configuration ofthe sheet of glass in the stacked assembly is then placed on top ofthe plastic sheet. The surface of the glass forming sheet which is placed adjacent the plastic sheet is coated with a demolding agent to prevent any adhesion between the glass forming sheet and plastic sheet. Typically, the glass forming sheet is bent on the same form as the glass sheet of the lami- nated assembly.Next, the spaces between the individual laminae are evacuated and the assembly is positioned in an autoclave. The autoclave applies pressure to the exterior surfaces of the assembly while heating the assembly to a temperature which causes bonding between the glass sheet and the plastic sheet. After the assembly is removed from the autoclave, the forming sheet can be removed from the stack.

One cause of defects in laminated glass structures is air trapped between the layers. It has been found to reduce such defects if, priorto treatment in the autoclave, the assembly is pressed, or subjected to vacuum at its edges, or both. The preliminary pressing, or "prepressing" operation, is typically performed byan apparatus having upper and lower series of pressing or nipper rollers arranged in axi ally parallel, tangentially contacting relation. Gener- ally, the rollers are mounted in a cage orframeadapted to be swung arcuatelyfrom an assembly receiving position to an assembly discharge posi tin. it has also been found advantageous to apply a peripheral evacuation chamber less in thickness than the assembly to which it is attached enabling the evacuation chamber and assembly to pass between the prepressing rollers. Such an apparatus is disclosed in United States Patent No. 4,040,888.

One of the problems with the prior art evacuation chamberwasthat it required a thin flexible tape of air impervious material to seal the evacuation chamber to the laminated assembly. Then, when the prepressing was completed, the tape had to be stripped from the laminated assembly. All of this taping required time and manual labor and left a sticky residue of adhesive on both surfaces of the laminated glazing.

Furthermore, the use of the rigid tubes made processing curved assemblies extremely difficult and required the nipper rollers to be positioned a fixed distance apart less than that which would enablethe most efficient prepressing operation.

Accordingly, it is an object of the present invention to provide a prepressing apparatus which allows the use of a conventional vacuum ring on assemblies to be laminated including acurvedglasssheetor sheets.

It is another object of the present invention to provide an apparatus for prepressing assemblies to be laminated which automatically adjusts to the changing curvature ofthe plies as the assembly passes through the pressing rollers.

In the accompanying drawings: Figure lisa diagrammatic top plan view of a prepressing apparatus in accordance with the present invention with the upper prepress rolls removed and showing an assembly in three different positions as it passes through the prepressing apparatus; Figure2 is a front elevational view of the prepressing apparatus shown in Figure 1 taken along the line 2-2 of Figure 1 and increased in scale; Figure 3 is a cross-sectional view of the prepressing apparatus taken along the line 3-3 of Figure 2 and increased in scale and showing the upper rollers in pressure engagement with the assembly; and Figure 4 is a rear elevational view of the prepressing apparatus as if taken along the line 4-4 of Figure 3 and increased in scale.

According to the present invention, there is provided a method for removing air from between the interfaces of an assembly of superimposed sheets, said assembly including a leading edge, a trailing edge and opposed side edges, including enclosing the peripheral edges of superimposed sheets with a continuous evacuation ring, said evacuation ring being in communication with the interfaces of said superimposed sheets and coupled to a vacuum source, characterized by applying a vacuum to said ring to withdraw airtherethrough; providing a piurality of pairs of opposed rolls arranged in spaced apart relationship, the axes of rotation of opposed rolls lying in the same plane and the corresponding rolls of each pair having a common axis of rotation; positioning the leading edge of said sheet assembly inwardly of said evacuation ring between said spaced apartrollswith said leading edge being substantially parallel with the plane including axes of rotation of said rolls, the numberof pairs of opposed rolls providing a length measured along the axes of rotation of the rolls less than the distance between the inner edges of said evacuation ring enclosing the opposed side edges; effecting relative movement between said pairs of opposed rolls so that said rolls enter into pressure engagement with opposite sides of said sheet assembly inwardly of said evacuation ring; advancing said assembly between said opposed rolls while continuing to apply said vacuum to said evacuation ring until said ring atthetrailing edge of said assembly is adjacentto but not yet in contact with said rolls; separating said opposed rolls to release said pressure engagement on said sheet assembly; and removing said assembly from between said opposed rolls.

Also, according to this invention, there is provided an apparatus for prepressing assemblies of stacked sheets for subsequent lamination thereof, characterized by a frame; a delivery conveyorforsupporting and advancing a horizontally disposed assembly in a generally horizontal path to one side of said frame; means for aligning said assemblyfor entry into said frame; means mounted on said frame for applying pressure to said assembly; and means for moving said assembly through said frame and said means for applying pressure, said means for moving including a plurality of drive rollers of different diameter rotatably mounted along an axis of rotation tilted with respect to said horizontal path such that each of said rollers engages a surface of said assembly, and meansfordriving said rollers in rotation to move said assembly through said frame and said means for applying pressure.

Referring to Figure 1,there is shown a portion of a production line for laminating sheet assemblies including a prepressing apparatus 10 located between a delivery or entry conveyor 11 and a take-off ordischarge conveyor 12. Assemblies to be laminated, such as the assembly 13, travel along the production line in the direction ofthe arrow 14. These assemb liesaretypicallyintheform of glass and plastic sheets arranged in a sandwich-like stack.

With reference to the assembly's ultimate orientation, after lamination thereof, in a vehicle, the assembly 13, has an upper edge 15, a lower edge 16, and side edges 17 and 18. The stacked assembly 13 is deiivered to the prepressing apparatus 10 on the delivery conveyor 11 which includes a parallel pair of driven belts defining an opening between them. The assembly 13 is supported along its downwardlyfacing surface by the belts, with the upper edge 15 being the leading edge.

The assembly 13 of superimposed stacked sheets approaches the prepressing apparatus 10 with the upper edge 15 and the lower edge 16 generallytransverse to the direction of travel 14 of the conveyor 11.

When the upper edge 15, which is the leading edge of the assembly 13 in Figure 1, approaches the prepressing apparatus 10, the assembly 13 is generally centered over a rotator cup 19 which is positioned between the delivery conveyor belts. This position of the assembly 13 is shown in phantom line and designated by the reference numeral 21. A pair of spaced apart aligning arms 22 and 23 are located between the belts of the conveyor 11 to engage the upper edge 15 Of the assembly 13 and stop it over the rotator cup 19. The rotator cup 19 is raised into contact with the lower face of the assembly 13 and the arms 22 and 23 are retracted. The cup 19 is rotated in the direction of the arrow 20through an approximate ninety degree arc to position the side edge 18 of the assembly 13, as shown bythesolid line, between the spaced apart upper and lower pressing rollers (only the lower rollers being shown in Figure 1 forthe sake of clarity). The cup holds the assemby by vacuum and then releases and retracts when the upper rollers are lowered into pressure engagement with the assembly as will be hereinafter more fully described.

The assembly 13 is then moved through the prepressing apparatus 10 and onto the discharge conveyor 12 in the discharge position shown by the phantom line 24.

During the prepressing operation and during the approach to and movement away from the prepressing apparatus 10, an evacuation orvacuum ring 25 remains attached about the peripheral edge of the assembly 13. The vacuum ring 25 is connected to a sourceofvacuum (not shown) by a connector hose 26. During the prepressing operation, a vacuum is drawn on the ring in orderto assist in the evacuation of air from between the adjacent sheets in the assembly 13. As best shown in Figure 3, the vacuum ring 25 is generally C-shaped in cross section with the opening slightly smaller in width than the thickness of the assembly 13to provide an airtight seal.

The vacuum ring 25 and the edges of the assembly 13form a vacuum chamber 27 which is in communication with the entire periphery of the assembly 13 and the connector hose 26.

The prepressing apparatus 10 is shown in greater detail in Figures 2 through 4. The prepressing apparatus 10 includes a frame 30 having a lower horizontal bed 31 and an upper horizontal arm 32 each having one end attached to a ground engaging upright post 33. The bed 31 and the arm 32 are in a spaced apart parallel relationship and the other end ofthe bed 31 is supported bya ground engaging leg 34.

Referring to Figures 2 and 3, the upper arm 32 supports a plurality of pairs of rubber prepress rollers 35.

The rollers 35 are typically mounted in pairs with each pair being pivotally attached at the center of a cross-bar 36 having its ends supported between op posite ends of a generally C-shaped yoke 37. The yoke 37 is connected to one end of a vertically extending shaft 38 having its other end attached to a piston extension 39 of an aircylinder40.Theair cylinder 40 is mounted on a bracket41 which is attached to the horizontal arm 32. Also mounted on the bracket 41 is a roller guide assembly 42 for positioning the shaft 38 for vertical movement between the upper position shown by the phantom lines 43 and the lower position shown by the solid lines in Figure 3. The number and spacing ofthe prepress rollers 35 depend upon the width of the assembly 13 and the amount and distribution of the pressure to be applied to the assembly.

The assembly 13 is supported on top ofa plurality of pairs of lower prepress orsupport rollers 44which are similar in construction to the rollers 35. However, these rollers are not moveable, but are fixedly attached to brackets 45 and 46 which in turn are attached to the horizontal bed 31. Thus, the assembly 13 is supported by the lower prepress rollers 44 and pressure is applied by the upper prepress rollers 35 when they are lowered into position by the air cylin ders 40. The brackets 45 and 46 are spaced apart along the horizontal bed 31 on opposite sides of a plurality of drive rollers 47. The drive rollers 47 are typically mounted in pairs on a box 48 attached to an upper surface ofthe horizontal bed 31. Each pair of the drive rollers 47 is rotatably supported by a bracket 49.The bracket 49 is attached to an upper end of a vertically extending threaded shaft 50 which extends through an aperture 51 in an upper surface of the box 48. A pairofstop nuts 52 are threaded onto the shaft 50 with a lower one ofthe nuts 52 engaging the upper surface ofthe box 48 and an upper one of the nuts 52 locking the lower nut in position on the shaft 50. The shaft 50 is pivotally connected to the bracket 49 at pivot point 53 for a purpose which will be explained below.

A motor and gear set 54 drives a sprocket 55 which in turn drives a roller chain 56 which is designated by a dashed line.The rollerchain 56 in turn drivesa sprocket 57 attached to one end of a drive shaft 58.

The drive shaft 58 is rotatably supported by a plurality of adjustable slotted brackets 59 which are attachedtothe box 48. Attached to the shaft 58 for co-rotation therewith are a plurality of driven sprockets 60. Each of the driven sprockets 60 is associated with a pair ofthe drive rollers 47. Positioned between each pairofthe rollers 47 isa sprocket 61 which is attached to the rollers 47 for corotation therewith. Each of the sprockets 60 drives an associated sprocket 61 with a chain 62.

In Figure 4, the rollers 47 have been labeled from rightto left with the letters "A" through "F". In accordance with the present invention, the rollers "A" through "F" are progressively iarger in diameterand preferably are tapered to provide a frustum forthe purpose of moving the assembly 13 through the prepress apparatus 10 in an arcuate path to the discharge position 24. Since the lower edge 16 ofthe assembly is longerthan the upper edge 15, the roller "F" has a longer distance to travel than the roller "A" along the lower surface ofthe assembly 13. The dif ferent diameter rollers compensate for this differ enceintravel distance to preventslippageand/or sliding between the lower surface ofthe assembly 13 and the drive surfaces ofthe rollers 47.Also, the arcuate path the assembly travels provides for more effectual pressing and prevents possible interference between the rollers and the vacuum ring 25 which can lead to the displacement thereof. In order to maintain a horizontal supporting surfaceforthe transparent assembly 13, the axis of rotation 63 of the rollers 47 is tilted or angled with respectto horizontal with the drive roller "F" being at a lower point than the drive roller "A".

The tilting of the axis is accomplished by loosen ing a pairofthreadedfasteners64whichextend through elongated slots in each ofthe brackets 59 and are threaded into a backing plate 65. Loosening the fasteners 64 allows height adjustment on the brackets 59 and threading the stop nuts 52 in the des ired direction allows the raising or lowering of the associated drive rollers 47. The drive rollers are pivoted at 53 such that the pivot points of all the drive rollers 47 can be aligned on the axis of rotation 63.

The movementofthe drive rollers 47 and the assoc iated brackets 49 also causes the drive shaft 58 to be tilted such that its longitudinal axis remains parallel to the axis of rotation 63. Such movement is permit ted by the adjustable brackets 59 and then thethreaded fasteners 64 are tightened along with the stop nuts 52 to fix the entire assembly in place.

From the foregoing, it is apparent that the objects ofthis invention have been fully accomplished. As a result ofthis invention, an improved apparatus is produced for prepressing glass and plastic sheets for subsequent autoclaving and lamination in a mass production operation.

Claims (15)

1. A method of removing airfrom between the interfaces of an assembly of superimposed sheets, said assembly including a leading edge, a trailing edge and opposed side edges, including enclosing the peripheral edges of superimposed sheets with a continuous evacuation ring, said evacuation ring being in communication with the interfaces of said superimposed sheets and coupled to a vacuum source, characterized by:: applying a vacuum to said ring to withdraw air therethrough; providing a plurality of pairs of opposed rolls arranged in spaced apart relationship,the axes of rotation of opposed rolls lying in the same plane and the corresponding rolls of each pair having a common axis of rotation; positioning the leading edge of said sheet assembly inwardly of said evacuation ring between said spaced apart rolls with said leading edge being substantially parallel with the plane including axes of rotation of said rolls, the number of pairs of opposed rolls providing a length measured along the axes of rotation of the rolls less than the distance between the inner edges of said evacuation ring enclosing the opposed side edges;; effecting relative movement between said pairs of opposed rolls so that said rolls enter into pressure engagementwith opposite sides of said sheet assembly inwardly of said evacuation ring; advancing said assembly between said opposed rolls while continuing to apply said vacuum to said evacuation ring until said ring atthetrailing edge of said assembly is adjacent to but not yet in contact with said rolls; separating said opposed rolls to release said pressure engagement on said sheet assembly; and removing said assembly from between said opposed rolls.

2. An apparatus for prepressing assemblies of stacked sheets for subsequent lamination thereof, characterized by: a frame; a delivery conveyorfor supporting and advancing a horizontally disposed assembly in a generally horizontal path to one side of said frame; meansforaligning said assemblyforentryinto said frame; means mounted on said frame for applying pressureto said assembly; and means for moving said assembly through said frame and said means for applying pressure, said means for moving including a plurality of drive rollers of different diameter rotatably mounted along an axis of rotation tilted with respect to said horizontal path such that each of said rollers engages a surface of said assembly, and means for driving said rollers in rotation to move said assembly through said frame and said means for applying pressure.

3. Apparatus as claimed in claim 2, characterized inthatsaid meansforaligning includes a pairofspaced apart aligning arms positioned adjacent said one side of said frame for engaging a leading edge of said assembly.

4. Apparatus as claimed in claim 3, characterized in that said means for aligning further includes a vacuum rotator cup which is vertically moveable to engage a lower surface of said assembly and attach thereto by vacuum, means for retracting said aligning arms, and meansforrotating said cuptoalign said assembly for entry into said means for applying pressure.

5. Apparatusasclaimed in anyof claims2to4, characterized in that each of said drive rollers is in the shape ofafrustum with the basesthereofgener- ally perpendicular to the axis ofthe rotation ofthe roller.

6. Apparatus asclaimed in any of claims 2to 5, characterized in that said means for applying pressure includes a plurality of vertically moveable prepress rollers mounted on said frame, and means for moving said prepress rollers between a first position spaced from said horizontal path and a second position whereby said prepress rollers engage a surface of said assembly and apply pressure thereto.

7. Apparatus as claimed in claim 6, characterized in that said means for moving said prepress rollers includes an air actuated piston and cylinder, said cylinder attached to said frame and said piston attached to a vertically extending shaft having at least one of said prepress rollers rotatably attached thereto.

8. Apparatus as claimed in claim 6, characterized in that said prepress rollers are rotatably attached in pairs to each of a plurality of vertically extending shafts connected in turn to respective pistons of air actuated piston and cylinder combinationsfiaving cylinders attached to said frame.

9. Apparatus as claimed in any of claims 2 to 8, characterized bya plurality of support rollers rotatably attached to said frame for engaging and supporting a surface of said laminated assembly.

10. Apparatus as claimed in claim 9, characterized in that said support rollers are positioned on either side of said different diameter drive rollers.

11. Apparatus as claimed in any of claims 2 to 10, characterized by a vacuum ring enclosing all edges of said assembly.

12. Apparatus as claimed in any of claims 2 to 11, characterized in that said means for driving includes a first sprocket driven by a drive means, a second sprocket connected to said drive rollers for rotation therewith and a chain connected between said first andsecond sprockets.

13. Apparatus as claimed in any of claims 2 to 12, characterized by means for vertically adjusting the position of said drive rollers with respectto said surface of said assembly engaged thereby.

14. A method of removing airfrom between the interfaces of an assembly of superimposed sheets substantially as described in the specification.

15. Apparatus for prepressing assemblies of stacked sheets for subsequent lamination thereof substantially as described in the specification with reference to the accompanying drawings.