GB2218671A - Removing air from between the interspaces of an assembly of superimposed sheets - Google Patents

Description

PREPRESS APPARATUS AND METHOD 221867 1 Inupi TA U i-iuATE The present

invention relates generally to the production of laminated glass sheets and, more specifically, to an improved apparatus for prepressing anti-laceraitive or laceration shield type glazings particularly adapted for use 5 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 or tempered 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 some type of laminated glass.

Typically, laminated glass of the type utilized in vehicle windshields consists of two sheets of glass bonded together with a thin plastic interlayer, such as a sheet of polyvinyl butyral, for example. In the event of an impact on a laminated glass windshield sufficient to break the glass, the plastic interlayer functions to bind the glass fragments together, thus reducing the risk of injury to a driver or passenger as 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 made to appreciably reduce the injury producing potential of automobile windshields.

Recently, it has been found hat the addition of a second plastic layer bonded to the inner glass surface of the laminated win&shield further increases the safety effectiveness of the windshield. This second plastic layer 2 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 person thrown against the windshield, while also increasing the penetration resistance of the windshield as compared to conventional laminated windshields. Also, the laceration shield reduces the an.ount of flying glass and thus the injury to car occupants as a result of objects that nay be thrown against the windshield from overpasses 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-layer body consisting 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 for this 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 for windshields is very high, especially as to optical qualities, and it has been very difficult to manufacture a windshield having a laceration shield which is-free off 3 optical defects. Even when the individual sheets of the laminated assembly are free from optical defects before bonding them together, it is difficult to join them and preserve the 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 thin transparent plastic sheeting are assembled in a stack to produce an assembly for subsequent lamination. A second sheet of glass (called a glass cover or forming sheet) conforming to the configuration of the sheet of glass in the stacked assembly is then placed on top of the platic 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 laminated 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, prior to 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 by an apparatus having upper and lower series of pressing or nipper rollers arranged in axially parallel, tangentially contacting relation. Generally, the rollers are mounted in a cage or frame adapted to be swung arcuately from an assembly 1 4 receiving position to an assembly discharge position. 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 chamber was that 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 enable the most efficient prepressing operation. 20 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 a curved glass sheet or 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 of the plies as the assembly passes through the pressing rollers. In the accompanying drawings: 30 Fig. 1 is a 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; 1 4 1 Fig. 2 is a front elevational view of the prepressing apparatus shown in Fig. 1 taken along the line 2-2 of Fig. 1 and increased in scale; Fig. 3 is a cross-sectional view of the prepressing apparatus taken along the line 3-3 of Fig. 2 and increased in scale and showing the upper rollers in pressure engagement with the assembly; and Fig. 4 is a rear elevational view of the prepressing apparatus as if taken along the line 4-4 of Fig. 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 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 edqe 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 engagement with opposite sides of said sheet assembly inwardly of said 6 evacuation ring; advancing said assembly between said opposed rolls while continuing to apply said vacuum to said evacuation ring until said ring at the trailing 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.

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 conveyor for supporting and advancing a horizontally disposed assembly in a generally horizontal path to one side of said frame; means for aligning said assembly for 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 means for driving said rollers in rotation to move said assembly through said frame and said means for applying pressure.

Referring to Fig. 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 or discharge conveyor 12. Assemblies to be laminated, such as the assembly 13, travel along the production line in the direction of the arrow 14. These assemblies are typically in the form of glass and plastic sheets arranged in a sandwich-like stack.

4 7 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 delivered 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 downwardly facing 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 generally transverse 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 Fig. 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 20 through an approximate ninety degree arc to position the side edge 18 of the assembly 13, as shown by the solid line, between the spaced apart upper and lower pressing rollers (only the lower rollers being shown in Fig. I for the sake of clarity). The cup holds the assembly 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 discharqe position shown by the phantom line 24.

8 During the prepressing operation and during the approach to and movement away from the prepressing apparatus 10, an evacuation or vacuum ring 25 remains attached about the peripheral edge of the assembly 13. The vacuum ring 25 is connected to a source of vacuum (not shown) by a connector hose 26. During the prepressing operation, a vacuum is drawn on the ring in order to assist in the evacuation of air from between the adjacent sheets in the assembly 13. As best shown in Fig. 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 13 to provide an air tight seal. The vacuum ring 25 and the edges of the assembly 13 form 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 Figs. 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 of the bed 31 is supported by a ground engaging leg 34.

Referring to Figs. 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 opposite 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 air cylinder 40.

The air cylinder 40 is mounted on a bracket 41 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 9 by the solid lines in Fig. 3. The number and spacing of the 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 of a plurality of pairs of lower prepress or support rollers 44 which 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 cylinders 40. The brackets 45 and 46 are spaced apart along the horizontal bed 31 on opposite 15 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 of the 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 20 extending threaded shaft 50 which extends through an aperture 51 in an upper surface of the box 48. A pair of stop nuts 52 are threaded onto the shaft 50 with a lower one of the nuts 52 engaging the upper surface of the box 48 and an upper one of the nuts 52 locking the lower nut in 25 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 30 dashed line. The roller chain 56 in turn drives a 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 attached to the 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 of the drive rollers 47. Positioned between each pair of the rollers 47 is a sprocket 61 which is attached to the rollers 47 for co-rotation therewith. Each of the sprockets 60 drives an associated sprocket 61 with a chain 62.

In Fig. 4, the rollers 47 have been labeled from right to left with the letters 'W' through "F". In accordance with the present invention, the rollers 'W' through "F" are progressively larger in diameter and preferably are tapered to provide a frustum for the 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 of the assembly is longer than the upper edge 15, the roller "F" has a longer distance to travel than the roller 'W' along the lower surface of the assembly 13. The different diameter rollers compensate for this difference in travel distance to prevent slippage and/or sliding between the lower surface of the assembly 13 and the drive surfaces of the 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 surface for the transparent assembly 13, the axis of rotation 63 of the rollers 47 is.tilted or angled with respect to horizontal with the drive roller "F" being at a lower point than the drive roller "A".

The tilting of the axis is accomplished by loosening a pair of threaded fasteners 64 which extend through elongated slots in each of the 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 desired 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 I Z1 11 1 movement of the drive rollers 47 and the associated 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 permitted by the adjustable brackets 59 and then the threaded 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 of this invention have been fully accomplished. As a result of this invention, an improved apparatus is produced for 10 prepressing glass and plastic sheets for subsequent autoclaving and lamination in a mass production operation.

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Claims (2)

1. CLAIMS:

   is 1. A method of 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 air therethrough; providing a plurality of pairs of opposed rolls arranged ih 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 engagement with opposite sides of said sheet assemblI, 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 at the trailing edge of said assembly is adjacent to but not yet in contact with said rolls; W 22-1u116711 13 separating said opposed rolls to release said pressure engagement on said sheet assembly; and removing said assembly f rom between said opposed rolls.
2. 2. A method of removing air from between the interfaces of an assembly of superimposedsheets substantially as described in the specification.

   Published 1989 at The Patent Office. State House. 66'71 High Holborn. London WC1 R 4TP Y'u--ther copies maybe obtained from The Patent Office.