DE2105954A1 - Laminated safety glass windshield - Google Patents

Description

PATENT '"·'. · ^ I

a Fr -.- k ¹ ·. '..: .U W- February 5, 1971

jchnccki. "ihc; -ir. ~ jj - U-. j! / -

PPG INDUSTRIES, INC., Pittsburgh, Pennsylvania 1522ξ U.S.A. Layered safety glass windshield

The invention relates to laminated safety glass windows, and more particularly to those used for vehicles while such layered objects can also be used in buildings.

Laminated glass is currently used as a glazing material in the windshields of automobiles, trucks and other vehicles because it reduces the possibility that passengers using such vehicles will be seriously injured by the windshield or parts thereof if an accident occurs. Layered glass contains two or more sheets of glass that are bonded together by means of an elastomeric interlayer material. Polyvinyl butyral is commonly used as an intermediate layer because it adheres to glass when subjected to appropriate temperatures and pressures, because it is transparent when bonded between the two sheets of glass, and because it is resilient and resilient when impacted against such a layered object expands. Other recently used interlayer materials are polyurethane compounds, sometimes introduced as a partial polymer and sometimes potted in place between a pair of sheets of glass. , - *

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The term "intermediate layer" is chosen here for descriptive purposes to denote an elastomeric material, that lies between layers of glass, regardless of whether this material is from the beginning as a single sheet or Layer of elastomeric material or as several sheets is interposed or as a layer of elastomeric material by potting a liquid resin between the panes of glass is molded.

Layered windshields offer two main safety benefits. In the event of an accident, the bond between the glass and the intermediate layer keeps the glass parts in the same place relative position to each other as in the unbroken state, which creates the possibility of injury from flying around Glass is reduced. Keeping the glass parts in the same relative isge also limits the possibility of Occurrence of jagged edges of the broken glass, which cause lacerations.

Another benefit of the layered windshield is related to the physical properties of the elastomeric Intermediate layers, for example polyvinyl butyral, polyurethanes or the like, back. In contrast to glass or other For rigid materials, an elastomer stretches before it breaks instead of breaking immediately when subjected to impact. In case of impact The elastomer stretches, thereby absorbing energy from the impacting object and increasing the speed of the impacting object Item is reduced. In many cases the speed of the impacting object can be reduced to zero before it penetrates the windshield.

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When polyvinyl butyral is used as an intermediate layer between panes of glass, the layer structure retains something of the elastomeric properties of polyvinyl butyral. Hence, a windshield that consists of two expands There is glass panes that are bonded with a polyvinyl butyral interlayer, in the immediate case of impact Impact area, which absorbs energy from the impacting object and reduces its speed will. This property of a layered windshield is known as penetration resistance.

The penetration resistance is particularly desirable in a windshield of an automobile because to keep these passengers inside the vehicle when they are thrown against the windshield and these break. In addition, a polyvinyl butyral interlayer reduces the possibility of passengers be seriously injured by a "ruff" resulting from partial penetration. Of the The term "ruff" is used to describe the periphery of a serrated hole in a windshield, that forms when penetrating. With a standard windshield the "ruff" consists of a number of sharp and jagged edges that are inclined at such an angle are that they can inflict severe wounds. This "ruff" can of course inflict fatal wounds on a passenger of a vehicle who hits the windshield with sufficient Force is thrown so that his face penetrates the windshield and on the sharp and jagged glass edges to Calm comes.

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The thickness of the intermediate layer is a factor in promoting penetration resistance. Another factor that determines penetration resistance is the stress distribution across the thickness of the glass panes of a laminated safety glass windshield O

The low thickness of glass is usually due to small surface scars and the fragility, which does not allow that the glass is subject to very high local stresses Neighborhood of these scars. Since the stress-concentrating effect of scars only applies to tensile stress ins When play comes, glass is only weak against tensile stress. Its compressive strength is high and in the absence of gross manufacturing defects, fractures persist from being under tension standing surface »

Tempering strengthens glass by pre-compressing its surfaces. This compression of the surface layers is balanced by internal tensions. While the tensile loads, which are thus generated inside have an influence on the strength of the glass, their presence can be a factor have far-reaching influence on the course of the breakage, once the pressure has been released.

There are currently two types of starch procedures

/ these
of glass. They are thermal and chemical annealing.

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During thermal annealing, the desired compressive stresses in the surface are by rapid cooling ces initially hot glass obtained so that their surfaces are tight and contract, while the core is still relatively fluid _o The nucleus is also gradually, its contraction act already against solid surface layers, which are thus put under pressure, while the core itself is put under tensile stress. The stress distribution over the thickness of the thermally annealed glass is characteristically parabolic.Typically, the areas of the glass are in the vicinity of the surfaces, to a depth of about 2/10 of the total thickness, under compression with a maximum value of the compressive stress on the surface of approximately 14.06 kg / mm (20,000 pounds per square inch). To compensate for this surface compression, the inner 6/10 of the glass thickness are in tensile stress, with the maximum stress in the middle of the glass thickness and having a value of about half the maximum surface compression.

While untempered glass usually breaks into a few large, sharp-edged pieces, thermally tempered glass falls Glass, when it breaks, into many small fragments, typically cubes with dimensions equal to the thickness of the glass and relatively blunt edges and corners. Both the size and shape of these fragments help that they are less dangerous than the fragments of untempered Glass. The mean particle size of tempered glass is likely to be related to the specific one Tension energy of the glass, do h. the elastic energy, which is stored in a unit volume of the pre-stressed material. That in turn depends mainly on the

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maximum stresses on the glass, since the parabolic The shape of the stress distribution in thermally tempered glass is essentially independent of the level of stress.

Chemical strengthening, also called chemical tempering, although somewhat newer than thermal annealing, is well known. There are several mechanisms by which it can be achieved. One of these mechanisms results in an ion exchange in the surface layers of the glass at a temperature close to the strain point of the glass. In the ion exchange process, relatively small ions, for example sodium, are replaced by larger ions, for example potassium, or smaller ions, for example lithium, are replaced by larger ions, for example sodium and / or potash. The crush of the larger I _o nen in the spaces that are zurückgeblieden by removal of the smaller ions produces a compression of the surface layers. Two other mechanisms for chemical annealing involve either ion exchange or partial crystallization, or both, at elevated temperatures such that the modified surface layers of the glass have a lower coefficient of expansion than the base glass. When an object treated in this way is cooled to room temperature, the different contractions of the surface and of the inner layers again produce compressive stresses in the surface.

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Since diffusion is a relatively slow process, the effects of chemical temperature do not go very deep the glass. This is reflected in the stress distribution on chemically tempered glass. With such a Glass extends the compressive stress from a relatively high level on the surfaces to zero at a depth of only a few thousandths of a centimeter (inches) below the surface. The rest of the inside of the jar holds only a very low tensile stress is maintained, which is used to balance the compressive forces in the very thin layers close to the surfaces is required. It can be seen that chemically tempered glass has the same surface pressure stress how thermally tempered glass can have a much lower internal stress and much less specific stress energy. While such strength in the absence of coarse surface wear and tear can be the same as that of thermally tempered glass, it does not have the same Tendency to disintegrate when broken. This may be beneficial in some applications, as explained below. It is commonly seen as a disadvantage in automotive engineering Considered applications where the small size of the fragments is as important as the increase in strength. To a To achieve such fragmentation, one can increase the surface compressive strength or the thickness of the compressed Layers, or both, enlarge to raise the specific stress energy of the glass to a level at which the particle size of its fragments is comparable to that of thermally tempered glass, in order to achieve a surface compression of about 14.06 kg / mm (20,000 pounds per square inch). In fact, the usual is chemically annealed Glass for automotive applications with surface compressive stresses on the order of

.56.25 kg / mm (80,000 pounds per square inch).

If one compares thermally and chemically tempered glass, then

• the former has the advantage that the greater thickness of the compressive layers on its surface is greater Abrasion resistance gives. Chemically tempered glass has the advantage of being easier to obtain to allow much higher tempering stresses and therefore higher strengths. In addition, it has the advantage that the thickness of the compressive layer, and with it the specific tension energy of the material, can be varied freely, which allows the fracture pattern of chemically tempered glass to be controlled regardless of its thickness.

It is also known to chemically temper glass that has previously been thermally tempered. This combination of tempering steps places a higher compressive stress in the surface of the glass at a shallower depth than the depth the compression zone created by thermal annealing resulting in a stronger glass article than it could be obtained by thermal annealing alone.

According to a typical method, increased impact resistance, fracture strength and penetration resistance in glass are ensured by chemical tempering. In a typical example with an alkali-silicon glass, for example sodium-lime-silicon glass, a pane of glass is made with a potassium salt at a preselected temperature range, preferably above 475 ^° C (875 ^° F) and below the strain point. of the glass, for enough time,

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so that an exchange can take place in the surface zone of the glass. Preferably, the glass panel is in immersed in a molten bath of potassium salt, preferably potassium nitrate. An exchange takes place during the immersion instead of introducing potassium from the potassium bath into the glass surface, apparently in exchange for sodium, which is in the outer or surface zone of the sheet of glass. It is believed that chemical tempering of sodium-lime-silicon glass is an ion exchange phenomenon in which potassium ions are exchanged for sodium ions.

Other glass compositions can be chemically annealed by immersion in alkali metal salt baths, one containing lithium Alkali silicon glass can e.g. B. advantageously by immersion in a molten bath of a sodium or potassium salt or a mixture thereof at elevated temperatures near the strain point of the glass be chemically tempered. It is also possible to carry out the chemical annealing process in several steps, wherein the lithium ions of a lithium-containing glass are exchanged for sodium ions, which subsequently exchanged for potassium ions during a second immersion, whereby the surface zone enriched with sodium, generated in the first ion exchange step «, becomes a potassium-enriched surface zone during the second dip.

After the chemical tempering treatment described above, the chemical nature of the alkali metal oxide components becomes clear the surface zone of the glass object basically by replacing lithium with sodium and / or potassium or

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Sodium changed by potassium, depending on the initial glass composition «, Contained at the same time the central inner areas of the glass object have essentially the same concentration of alkali metal, as before the treatment.

At lower temperatures, the effect of such contact with a molten metal salt is much slower with the result that chemically tempered glass articles are difficult to obtain within a period of time that is economically reasonable. For example, immersion of soda-lime-silica glass for one hour in molten potassium nitrate does not significantly enhance the strength properties of the glass at 38O ⁰ C (700 ⁰ F). At this temperature, much longer periods of immersion are required to produce strength (strength) comparable to that achieved in a minimal period of time (5 to 10 minutes) at higher temperatures. At temperatures above about 470 ° C (870 ⁰ F) the desired strength improvement also occurs Shneller.

The upper limit of the contact temperature depends on the softening and melting temperature of the material being treated Glass object. The contact temperature cannot override the melting temperature of the glass composition, However, it can lower the strain point and also the softening point of the glass composition exceed certain circumstances. For example, the contact temperature can be kept correctly as long as the glass is correct can also be used at a temperature above the melting

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temperature of the glass, provided that the contact at these elevated temperatures is of sufficiently short duration to allow thermal relaxation of the strength properties induced by ion exchange to avoid. Indeed, in some cases it is possible to keep the temperature of the touch within to maintain the softening temperature range of the particular glass object under treatment. Under these thermal conditions can have extremely short contact times, for example of the order of magnitude of 1 minute or less, can be used "

The depth or thickness of the surface zone of compression depends on the temperature and the duration of the chemical tempering treatment _o

U.S. Patent No. 3,396,079 discloses a laminated safety glass windshield comprising a pair of glass panes, of which at least one is chemically tempered, and which are made of by means of an intermediate layer stick together elastomeric plastic. The invention sees an improvement on laminated safety glass windshields with a relatively thick outer pane of tempered Glass, which is preferably chemically tempered, to a compressively stressed surface zone of at least 0.005 centimeters (0.002 inch) thick with an intermediate plastic layer at least 0.075 centimeters (0.03inch) thickness that is preferably treated to her Sticking to glass, and an inner pane of glass,

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which points into the interior of the enclosure in which the Object is installed, and made of relatively thin, preferably untempered pane glass with a preferred Thickness is in the range between about 0.15 centimeters (0.05 inches) and about 0.18 centimeters (0.07 inches).

The compression stress zone of the outer glass pane is, by virtue of its minimum depth of 0.005 centimeters (0.002 inch), able to withstand road stone impacts and still does not become opaque, like thermally tempered glass, if the outward-facing glass pane of the layered windshield is touched by a small object or a large zoom flying object, such as a head, a bird, a brick, or the like, is broken ₀ the outwardly facing compressive stress zone must be sufficiently deep, shut off to wear on their depth during the normal life of the windshield.

The outer surface of the outer glass sheet tends to develop small damaged parts in use Areas known as service flaws. These operational spots occur during handling in windshield manufacture and installation in the automobile and are in the field of their exterior Surface more often due to wear and tear, rubbing with windshield wiper blades and the like after being installed in an automobile. The inner surface of the outer

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Glass facing the intermediate layer, on the other hand, is exposed to wearing elements through direct contact protected with the intermediate layer

A shock from an object outside of a vehicle in which the windshield is installed will bend the Windshield in the hit area to reduce the compressive stress in the outer surface zone Neighborhood of the shock, while a tensile stress-inducing stress in the inner surface the outer disk is communicated. However, since the inner surface of the outer pane of glass is relatively is free of stains (scratches and the like), the resulting tensile stress is sufficient in its Surface zone adjacent to the intermediate layer is not sufficient to cause breakage because these starting points of the break are absent, therefore the outer chemically tempered glass pane has a greater resistance to penetration than a pane of glass whose inner surface is not so protected. As a result, their resistance to breakage increases Resistance of the entire windshield against penetration in the event of impact by objects coming from outside ο However, if a sharp object is the outer If the chemically tempered glass pane penetrates, smooth particles are produced, which by means of the intermediate layer are held and therefore provide a low visual obstruction.

An internal object, on the other hand, induces an inclination to generate tension in the outer surface of the outer pane when it hits the inner one

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Surface of the windshield “This voltage stress introduction causes the outer pane of glass to break whenever the impact force, for example through the head of an occupant, introduces a change in stress large enough to cause a break in the faulty one (scratched) local area to begin. Such a breaking force is less than required would be if the outer surface zone of the outer glass pane were not defective (scratched). Therefore it is not necessary in the present structure that a chemically tempered glass sheet, one of the Windshield layers is worn locally to form stress peaks, as in FIG US Patent No. 3,473,997 proposed because the fewer operational defects (e.g. scratches), which form over the free surface, in the manner of stress increases over the entire surface the outer disc and the likelihood of welted neck fracture resulting from the impact result in relatively high speeds.

Furthermore, if the windshield according to the invention from the inside of the vehicle with a blunt object is hit, for example the head of an occupant, at a speed sufficient to break it the outer chemically tempered glass pane forms small because of the resulting high bending stress Particle. These tiny particles, in turn, control the size of the particles that result from the broken thin Form untempered glass on a sufficiently small one

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Dimension, which leads to a significant reduction in Cuts leads. If the outer pane of glass were to break into large particles, the resulting ones would larger particles of the inner pane of glass cause larger cuts »

If the windshield is secured with an inner sheet of chemically strengthened glass, the inner one is Surface thereof facing the intermediate layer free from operational defects (e.g. scratches) and resists breakage when hit by an occupant's head. Increased loads must be introduced, to reduce the resistance of the inner chemically tempered glass pane to breakage. Resilience the inner glass pane against breakage at high impact velocity would otherwise reduce the likelihood increase of serious injuries to the occupant.

When the head of an occupant hits a windshield according to the invention, the unannealed, thin one bends inner disc more than one, which has a greater usual thickness at low impact speeds; the interlayer contributions and the mechanical stress applied to the outwardly facing surface of the outer glass sheet acts while the latter bends convexly on the joint are sufficient to absorb the compressive stress caused by the outer surface imposed by chemical annealing is to be overcome. Therefore, it is more likely that the outer panes of glass as well as the thin inner pane breaks when pressed against the layered windshield

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bumps inside an occupant's head or other blunt object rather than resisting breakage and to strike a blow.

The inner pane of glass, consisting of fire-polished, non-tempered pane glass, is less likely to break Resilience than the outer pane of glass, but since a human head is relatively blunt compared to Objects that are likely to hit the outer pane of glass will distribute the impact force on the inner pane Glass pane over a larger area than is the case with the outer glass pane. Preferably the inner glass pane is not strengthened by chemical or thermal annealing. The flexibility before breakage depends on the Thinness of the untempered inner glass pane. In addition, the thinness enables the unannealed inner Pane simply shatters into relatively harmless fragments if once the blunt impact force of the head of one Occupant is sufficient to trigger the break.

Another safety factor arises when using windshields are composed of sheets of glass that are much thinner than conventional sheets of glass currently known as Automotive windshields (nominal thickness of about 0.32 centimeters (1/8 inch)) can be used. For example, if the chemically tempered outer glass sheet has a thickness of about 0.175 centimeters (0.07 inches) to about 0.375 centimeters (0.15 inch) and the inner sheet of glass is about 0.125 centimeters (0.05 inches) to about 0.175 centimeters thick (0.07 inch), the broken inner pane of glass has a much lower risk of injury to you

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butting head, as their relative thinness is less damaging as a jagged fragment of untempered glass of the more usual thickness. Preferably the inner Glass pane by cutting a slice with required

/ one
Outline made from ⁷ right-angled washers that were previously

was cut on a ribbon of thin glass, which was produced by a method described in a parallel patent application "thin sheet glass of low deformation and method and apparatus for its production"
was suggested.

When the interlayer material is plasticized polyvinyl butyral from about 0.075 centimeters (0.03 inches) to about 0.15 centimeters (0.06 inches) thick and treated to control the degree of its adhesion to glass, its contribution to impact is considerably better than that of an intermediate layer of the type previously used commercially at a thickness of 0.0375 centimeters (0.015 inch). The combination of the controlling thickness and adhesion to the interlayer glass improves the penetration control characteristics of the laminated safety glass windshield. if
If the thickness of the plastic interlayer used in the windshield is less than 0.075 centimeters (0.03 inch), the possibility of a "frill" increases, particularly when glass of the thickness currently used in conventional windshields is used.

The present invention provides laminated windshields with overall safety features similar to known laminated windshields

^: Outperform windshields. The safety glass industry has stratified several tests to determine the safety

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Windshields determined »A test facility is a sled like the one shown in" Eleventh STAPP Car Crash Conference "; proceedings by the Society of Automotive Engineers, Inc., New York, 1967, page 143.

This typical system for testing laminated windshields includes a full-scale automotive Windshield test fixture that pneumatically engages a sled (total load approximately 500 pounds) including the Alderson doll) on a · preselected Speed 'The slide and its actuating cylinder are stopped hydraulically. The sleigh is with a trough-shaped seat that carries the Alderson doll and is pushed to a desired thrust speed with a accelerates pneumatic cylinder, which separates from the carriage before the latter comes into engagement with a deceleration cylinder. An · electronic · measuring device measures the carriage speed in the interval between its disengagement from the accelerating cylinder and its engagement with the retarding cylinder. The slide is brought to a stop at a desired location by the deceleration cylinder. During the sledge stops, the chrysalis continues to fly in a manner that doubles a barrier-like thrust on the vehicle stopped before the passenger touches it. Another way of interpreting the results is by viewing them the relative velocity of impact and comparison with other types of accidents where such relative velocities can be achieved. A windshield * ?.

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frame is attached to a track along which the slide moves. The windshield structure will used to have the same construction conditions of resilience, frame retention, glass angle and the surrounding components. This ensures the maximum reality of the test conditions. The device is positioned so that the forehead of the Aiderson doll with the test windshield is approximately 12.5 centimeters (5 inches) meets up to 15 centimeters (6 inches) below the upper bracket in the plane of the glass «

The windshields are in the frame using of adhesive glazing similar to most ugly, commercial manufacturing attachments. This makes it easier the replacement of test windshields "

Biaxial accelerometers are placed immediately behind the forehead area of the doll's head to help guide the Measure delay in impact. The delays are then compared to the delay violation curve, to determine whether a head injury is likely to occur. These comparisons, expressed as a safety index, are described later,

Since carcasses cannot be used for many tests, became a means of determining soft tissue injuries, and especially minor soft tissue injuries, achieved by covering the head of the Alderson doll with two layers of damp chamois leather to keep the human

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Simulate skin. Surface lesions on the outer Shifts are only classified as "minor" and assigned an injury score of 1, while injuries would occur both layers of chamois leather are viewed as "serious" and given an injury score of 5, with intermediate stages of damage to the chamois leather with the numbers 2, 3 or 4 depending on the severity the damage are intended.

Films are usually, but not always, recorded when testing windshields of various configurations with the sled assembly described above. Such films help those studying this technology.

A factor known as the severity index was identified with identified the relative safety of the windshields, as determined from impact tests with the Alderson manikin, which is covered with two layers of damp chamois leather on the test sled device. The severity index (S. I.) is calculated from the formula:

SI = J Α ² ' ⁵ dt, where

A is the acceleration in units of gravity and dt is the time differential in milliseconds between the moment of Bump of the manikin's head against the test windshield and 'the time a horizontal accelerometer, attached to the doll's head indicates sudden negative exposure. This value will be for every millisecond determined during the time interval and the value above integrated throughout the time period. The severity index

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is calculated, in other words, from the area under the curve, which results from a plot of the acceleration forces, acting on the doll's head as a function of time. A severity index of A thousand has been suggested as the injury threshold for head butts. In general, the severity index increases with the speed of impact.

Prior to the invention, it was believed to be the safest laminated glass-plastic automotive windshield Vehicle closure according to U.S. Patent No. 3,473,997 “This known windshield includes a outer pane of glass approximately 0.268 centimeters (0.105 inch) thick, an inner pane of chemically tempered glass approximately 0.175 centimeters (0.070 inches) thick and an intermediate layer plasticized polyvinyl butyral, which is treated to regulate its adhesion to the glass and has a thickness of approx 0.075 centimeters (0.030 inch) with the inner pane of glass having a series of stress risers is provided in order to divide up its breakage after a predetermined stress level is exceeded. Severity index measurements based on impacts with simulated Head shapes on a sled tester similar to the type described above, and dislocation numbers based on Damage to the chamois leather, were used to determine the relative safety figures for the present invention ' as compared to the windshield of U.S. Patent No. 3,473,997.

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The construction, which is provided according to the invention, avoids the need for increasing loads, as provided in U.S. Patent No. 3,473,997 are, and still gives results that are favorable in comparison with the known windshields, that provide for such increases in stress, are " Eliminating the stress increases eliminates an additional step in the windshield manufacturing process, thereby reducing the cost of manufacture. In addition, the test results have indicated that windshields with stress lifts contradicting test results of windshield to windshield surrender »

Table I shows the results of impact tests performed with the sled assembly at various impact speeds including a comparison of injury numbers based on damage to the Chamois leather, and a comparison of the severity index.

/ was ° ο

In all cases, the windshield is below 35 in the Built-in test room.

The so-called PPG construction, its test results in the table were in accordance with the present invention and included an external A disk about 0.32 centimeter (1/8 inch) thick of flow glass that has been chemically annealed to form a Create a compressive stress zone that extends approximately 0.005 centimeters (0.002 inches) from each surface and an inner sheet of sheet glass approximately 0.162 centimeters (0.065 inch) thick, which after

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the process described in the co-pending application "Thin, low-deformation sheet glass and the method and apparatus for its production "was proposed. No glass pane of the PPG construction? was provided with increased loads.

You so-called. Howitt (U.S. Patent No. 3,473,997) construction, the test results of which are also listed in the table contained an outer disc Made of untempered glass of approximately 0.262 centimeters (0.105 inch) thick and an inner sheet of chemically tempered glass approximately 0.175 centimeters (0.070 inch) Thickness, provided with increased loads. The Howitt design test windshields were the same as tested the PPG constructions. Both constructions had an intermediate layer of plasticized polyvinyl butyral approximately 0.075 centimeters (0.030 inch) Thickness treated to control adhesion to glass. Prevented in every case shown in the table the unit tested at the stated impact velocity that the doll's head penetrated the test windshield *.

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Table I.

Comparison of impact tests

PPG construction

Impact velocity Injury
number Violent
ability
index 20.4 1 520 22.2 - - 22.5 1 779 24.5 - - 25.0 - - 25.2 3 630 26.0 - - 27.6 2 1370 29.1 - - 29.5 2 1564 33.1 3 804

Howitt-Konstrult t ^ on

Injury severity3 number index

1
2

1
2

390 2327

832 1062

2205 687

2 not available

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Further features, advantages and possible uses of the. The present invention will emerge from the enclosed Representations of exemplary embodiments as well as from the following description,

Show it:

Figure 1 is a schematic plan view of a curved, layered safety windshield according to the invention, and

FIG. 2 shows a cross-sectional view of the windshield according to FIG. 3 along the line II-II.

The drawings illustrate a curved, laminated windshield W with an outer, chemical tempered glass pane 11 and an inner glass pane 12, which are connected by an adaptation layer 13 made of elastomeric material, for example plasticized polyvinyl butyral are. The outwardly facing surface 15 is convexly curved; the inner surface 16 of the inner glass sheet 12, which faces inside the enclosure in which the windshield W is installed, has a concave shape. the Surface 15 of the outwardly facing glass pane 11 has a surface compression stress zone which extends extends approximately 0.005 centimeters (0.002 inches) deep from the outwardly facing disc 11. The one another opposite surfaces of the inwardly facing pane 12 are fire polished as they are in a pane glass drawing process are created where a continuous band,

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which provides the disc, no solid member contacts, until it has cooled to about 515 ⁰ C (95O ⁰ F). Normally, the surface 17 of the glass pane 11 facing the intermediate layer, as well as the peripheral edge surfaces, are provided with compression stress zones with the same thickness as the surface zone 15 of the outer glass pane 11. The preferred minimum compressive stress on surface 17 is 35.16 kg / mm (50,000 pounds per square inch).

The thickness of the inner glass pane should be between 0.1QO Centimeters (0.040 inches) and 0.225 centimeters (0.090 inches) and that of the outer pane of glass between 0.100 centimeters (0.040 inch) and 0.375 centimeter (0.150 inch) and the thickness of the plasticized polyvinyl butyral interlayer between 0.075 centimeters (0.030 inches) and 0.150 centimeters (0.060 inches). A preferred arrangement is one outer sheet of flow glass nominal 0.32 centimeter (1/8 inch) thick, inner sheet of 0.162 centimeter (0.065 inch) thick and an intermediate layer 0.075 centimeter (0.030 inch) thick.

The compression zone in the outside Facing surface zone 15 of the outer glass pane 11 is sufficiently thick to provide sufficient protection against impact to be provided by road objects, even if they are during the course of the normal life expectancy of the automobile, in which it is built is worn out. The intermediate layer flexes when impacted by most street objects. The thinner inner, untempered glass pane 12 is sufficient

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thin in order to provide relatively harmless splintering when it breaks in cases when an object ··: - ♦ ·· - \ ■■> strikes against the outer glass pane 11 with a force which leads to the breakage of the latter.

If an accident occurs, an occupant of the vehicle against the inwardly facing surface 16 of the interior When flapping washer 12, the flexible inner washer 12 does not simply break at low speed shock because its flexibility allows for some yield and since a vehicle occupant's head is relatively blunt compared to sharp penetrating objects, for example stones and the like that can strike the outer glass pane 11. When the blunt impact force against the inner glass pane 12 is sufficient to trigger a break, it simply spreads around to form relatively harmless fragments of the thin pane glass of the inner pane. The extent of the break in the inner thin glass sheet 12 is influenced by the small particle size of the fragments in the chemically annealed outer glass pane 11, if the latter is hit by a blunt object, for example the head of a vehicle occupant, breaks.

The invention recommends the use of conventional soda-lime-silica flow glass for the outer pane the layered safety glass windshield and a commercially available soda-lime-silicon oxide pane for the inner pane of glass. Since none of these panes of glass wears out during their manufacture, theirs is mechanical

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Strength from pane to pane more uniform than with Panes made from commercially available sheet glass, which is primed and polished during manufacture will. As previously mentioned, the ablation of glass to form stress bumps, as suggested in U.S. Patent No. 3,473,997, leads to inconsistencies in strength from disc to disc. In addition, the thinness of the inner pane is made of untempered Window glass has a lower wounding effect than the more rigid, thicker panes of commercially available windshields.

A typical soda-lime-silicon flow glass that is suitable for use as an outer pane of glass in accordance with of the invention has the following composition:

Components by weight

SiO 73.05 (usual range 71 to 7596)

Na ₂ O 13.68 (usual range 12 to 14 #)

K ₂ O 0.03 (usual range 0 to 196)

CaO 8.91 (usual range 8 to 1296)

MgO 3.85 (usual range 2 to 596)

SO ₃ 0.37 (usual range 0.1 to 1.096)

Fe ₂ O ₃ 0.13 (usual range 0.1 to 1.09Ä)

O ₃ 0.11 (usual range 0.1 to I.O96)

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The outer glass pane 11 is provided with a compression stress zone of at least 0.005 centimeter (0.002 inch) thick by immersion for 64 hours in the potassium nitrate at about 490 ⁰ C (900 ⁰ F). The inner glass sheet 12 is preferably sheet glass which is produced by a method as proposed in the parallel application "Thin sheet glass of low deformation and method and device for its production" «

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A typical soda-lime-silica pane glass composed

setting suitable for use as an inner pane of glass 12 has the following components:

Components by weight

SiO ₂ 72.58 (usual range of variation 71 to 74%)

Na ₂ O 13.13 (usual range of variation 12 to 14%) CaO 8.58 (usual range of variation 7 to 10%)

MgO 3.60 (usual variation range 2 to 5%)

Na ₂ SO ₄ O ₀ 58 (usual range of variation up to 1%)

Fe ₂ O 0.11 (usual range 0.1 to 1%)

Al ₂ O ₃ 1.30 (usual range 0.1 to 3%)

The creation of curved, layered windshields uses a pair of sheets of glass of matching contour and different Composition (one made of flow glass, the other of fire-polished sheet glass) on each of a row of bending forms of concave elevation with a suitable separation material placed between the panes of glass. the

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Molds are passed through an elongated tunnel where the glass is heated to bending temperatures to achieve the to lower the concave shape of the mold. The curved panes are cooled at a controlled rate, until the slices are cold enough to handle. The curved panes are separated, and the lower, thicker flow glass pane each bent pair is chemically annealed for sufficient time to create surface compression stress zones about 0.005 centimeter (0.002 inch) thick. The upper disk made of fire-polished Pane glass in each pair is saved for further use, if the corresponding flow glass pane has completed its chemical tempering. The chemically strengthened flow glass panes are then ready for assembly with the fire-polished discs. When joined with a plasticized polyvinyl butyral interlayer will be a sandwich structure with one of the fire polished Discs of a curved pair formed, which is arranged on one side of the intermediate layer, around a concave outer Surface of the sandwich structure to form that goes into the interior of a vehicle, and with one of the chemically tempered flow glass panes of the curved pair, which is on the outer Side of the intermediate layer is arranged to form a convex outer surface of the sandwich structure, which for the exterior of the vehicle has.

The assembly is carried out in two stages. The first stage, prepressing, is using rubber tubing edge channels as described in U.S. Patent No. 2,948,645. The matching pairs of curved glass panels

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are arranged with the intermediate layer to form sandwich structures. The tube is then fitted around the edge periphery of each sandwich structure and angeschlossen- to a vacuum source, the pre-pressing is at a temperature of about 15O ⁰ C (300 ⁰ F) for 13 minutes "under a vacuum of about 65 to 72 centimeters (26 to 29 inches) of mercury. The precompressed windshield patterns are then in a Ölautoklaven for 45 minutes at about 140 ⁰ C (275 ⁰ F) using 0.14 kg / mm (200 pounds per square inch) Autklavendruck autoklavierto After autoclaving allowed to cool the laminated windshield Ramtemperatur .

A specific embodiment of the invention has been described above. Some obvious changes to the interlayer material ζ »B * different treatments of the plasticize polyvinyl butyral, as in the following US patents proposed can be made:

U.S. Patent No. 3,178,334; 3,220,568; 3,231,461; 3,249,487; 3,249,488? 3,249,489 i 3,249,490; 3,262,835; 3,262,836; 3,262,837; 3,271,233i 3,271,234; 3,271,235; 3,361,699; 3,372,074; 3,384,532; 3,396,074; 3,402,099; 3,424,646; 3,434,915; 3,437,552; 3,437,553; 3,455,754; or 3 468 749.

Other changes may affect the use of polyurethanes as an intermediate layer. For example, are suitable Polyurethane interlayers and glass layers with polyurethane interlayers in U.S. Patent No. 3,388 and No. 3,445,423 and Canadian Patent Nos. 673,674, 673,678, $ 813,857, and 817,392. Other

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Changes relate to the reduction in the adhesion of one or both panes of glass to the intermediate layer a technique as described in British Patent No. 1,144,369.

In addition to the design of the glass panes to the desired shape of the layered windshield by gravity lowering technology of the type described in U.S. Patent No. 3,248 is the shaping of the individual glass sheets contemplated into their desired shape by press bending, then chemically annealing one of the disks prior to stratification as suggested in U.S. Patent Application No. 736,019 dated June 11, 1968.

Other changes concern the type of stratification. Initial pressing can be done by using a roller press device ' of the type described in U.S. Patent Nos. 2,983,635 and Nro3 351 001 instead of vacuum technology In addition, the final stratification can be achieved in an air autoclave instead of a Qautoclave technique can be achieved =

The essence of the invention, regardless of the method of manufacture, is the combination of a relatively thin, untempered glass pane with a chemically tempered glass pane, which is regulated by means of a suitable plastic intermediate layer Bond, with the panes of glass oriented relative to the vehicle in which they are installed, that an optimal penetration resistance against sharp objects that strike from outside the vehicle, is provided, as well as sufficient flexibility and ability to break when impacted by a blunt object »

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For example, the head of a vehicle occupant before the impact force is sufficient to cause serious injury of a passenger, and the particles resulting from the breakage for minimal Worry about cuts.

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Claims (3)

35 - Claims Laminated safety glass windshield, characterized by an inward-facing layer unannealed glass with a thickness between about 0.125 Centimeters (0.05 inches) and about 0.175 centimeters (0.07 inches), an intermediate layer of plastic organic material from the class of plasticized polyvinyl butyral and polyurethane with a minimum thickness of about 0.075 Centimeter (0.030 inch) adhered to the inwardly facing layer and an outwardly facing layer Adhesive glass having a thickness ranging from about 0.175 centimeters (0.07 inches) to about 0.375 centimeters (0.15 inches) on the intermediate layer, the outwardly facing glass layer having a compression stress zone in it Surface facing away from the intermediate layer to a depth of at least 0.005 centimeters (0.002 inch) produced by chemical annealing. 2. Windshield according to claim 1, characterized in that that the outwardly facing layer consists of flow glass. 3. Windshield according to claim 1, characterized in that the intermediate layer made of plasticized polyvinyl butyral exists, which treats to regulate the degree of adhesion to at least one of the glass layers is. 109834/1530 Windshield according to Claim 3, characterized in that that the intermediate layer is treated to regulate the adhesion to the outward-facing glass layer, 5ο windshield according to claim 3, characterized in that that the windshield is treated to regulate the adhesion to the inward-facing glass layer » 6 = windshield according to claim 3, characterized in that the intermediate layer for regulating the adhesion to both the glass layers is treated. 7ο windshield according to claim 1, characterized in that that the outwardly facing glass layer has a compressive stress of at least 35 = 16 kg / mm (50,000 pounds per square inch) in its surface zone facing the intermediate layer. 109834/1530