DE1696051B1 - SAFETY GLASS PANEL, IN PARTICULAR WINDSHIELD FOR MOTOR VEHICLES, MADE OF A SILICATE GLASS PANEL AND A PLASTIC PANEL CONNECTED TO THE SILICATE GLASS PANEL ON THE JOINT SIDE - Google Patents

Description

The invention relates to a safety glass pane, in particular one Windshield for motor vehicles, consisting of a silicate glass pane and a with this connected plastic disc exists.

Two different types of safety glass are used for windshields today used, namely on the one hand so-called "single pane safety glass" and on the other hand "Laminated safety glass".

Toughened safety glass is toughened glass that is in its surface layers has a compressive prestress caused by tensile prestress in the none of the glass pane is kept in balance.

The usual laminated safety glass consists of two non-toughened glass Single panes of glass made with the help of a thermoplastic interlayer made of polyvinyl butyral are connected to each other.

Tempered safety glass breaks down into small fragments in its entirety. If, when the vehicle suddenly decelerates, an occupant is thrown against a windshield made of single-pane safety glass, the pane breaks at an impact speed of the occupant's head of around 15 km / h as a result of the local bending stress. The breaking process takes place extremely quickly. Already about 1 millisecond after the head touches the windshield, the windshield is completely broken and the occupant's head is released, so that no more decelerating forces act on the head. As a result of this extremely short duration of action of the deceleration forces, only a very small part of the kinetic energy of the body is absorbed by the windshield.

Laminated safety glass panes are also broken through at certain impact speeds. With a thickness of the polyvinyl butyral intermediate layer of 0.38 mm, as has been generally used up to now, the penetration of the human head takes place at an ambient temperature of about 201 ° C. at a head impact speed of about 25 to 30 km / h. The consequence of piercing through a laminated safety glass pane, however, is the formation of the extremely dangerous so-called "ruff", i. H. a collar of sharp glass splinters held in place by the butyral film at the edge of the breakthrough, which can easily lead to life-threatening cuts.

In order to reduce the risk of piercing, a move has been made to double the thickness of the butyral layer. It will only penetrate at about twice the impact speed, namely from about 45 km / h. If the windshield does not break through, up to four times more of the kinetic energy of the human body is destroyed by such a windshield than with a windshield with a 0.38 mm thick butyral layer. In contrast to single-pane safety glass panes, in which the duration of impact forces is less than 1 msec, the duration of impact forces on laminated glass panes is incomparably longer due to the plastic deformation of the butyral interlayer. It reaches values of up to 160 msee.

For the internal injuries that occur when an occupant hits the windshield, however, as we know today, in addition to the amount of the deceleration forces, the duration of these forces' action is of decisive importance. The longer the duration of these forces, the lower the deceleration forces that are endured.

The various human organs have different levels of resistance (tolerance limit) to deforming forces and their duration of action. The work on the stresses and injuries of the human head in the event of an impact with the stim on hard plates, which is best known to date in the specialist world, can be traced back to LM P atrick, Department of Enginee-Mecwanics at Wayne State University. Among other things, they have been published in the publication "Human Tolerance to Impaet - Basis for Safety Design". In this publication, LM P atrick set up a tolerance curve for the permissible effective delays depending on the duration of exposure on the basis of his test results for moderate concussions. This curve clearly shows how important the duration of the delay forces is for concussions.

It is also known that car accidents can also be life-threatening Cervical injuries occur due to the strain on the cervical spine can be caused when the head hits the windshield. More precise Studies on the resilience of the cervical spine in the event of an impact of the head on the windshield and on the behavior of the various safety glasses with regard to injuries to the cervical spine, however, were not previously known.

It has now been found that safety glass panes with long peak times, i.e. in particular the known laminated glass panes, can lead to life-threatening injuries to the cervical spine even at relatively low impact speeds and that, on the other hand, the tolerance limit for macroscopic cervical vertebrae injuries is significantly below the tolerance limit for concussions already mentioned (D. Zif f er, F. B backner and R. Henn: "The behavior of the cervical spine in connection with the skull base and the upper thoracic spine when falling on safety glass for automobile windscreens (single-pane safety glass - laminated safety glass)", Central Journal for Traffic Medicine, Traffic Psychology and Adjacent Areas, (December 1967).

As these investigations have shown, the Injuries to the cervical spine caused by the fact that these are already relatively low impact speeds to a dangerous extent on bends or kinks really stressed when the head hits a windshield made of laminated glass This bulges namely after the breakage of the glass panes as a result of the deformation the butyral interlayer at the point of impact, and the head is thereby fixed in place. Then the body inasse pushes itself progressively after. But since the body mass is essentially below the head and the Head is fixed in its position, it comes within the impact process except for the dangerous compression in the cervical region to a significant bending the cervical spine, which causes the severe damage mentioned above.

To what extent the resistance of the cervical spine in these circumstances is less than the resistance of brain tissue against concussions, is the following figures show: While with an exposure time of 10 msec, the tolerance limit for concussions after LM Patrick at about 320kp, ff is (the LM Patrick values given in accelerations were converted into kp by multiplication with the mean skull mass of 4.5 kg ), according to the experiments of D. Ziff he the cervical spine is already at around 160 kp with a shock on the windshield lasting the same time , f, badly damaged. With a duration of the effective impact forces of 50 msec, the tolerance limits for concussions according to LM P atrick are around 220 kp, ff, for damage to the cervical spine, however, already at 50 kp, ff. These values apply to macroscopic damage to the cervical spine, such as B. cracked intervertebral discs. They are even lower if microscopic damage is also taken into account, which can also be life-threatening.

The invention is intended to provide a safety glass pane, in particular a windshield can be created that takes this new knowledge into account and thus in the event of an impact of the human body on the windshield offers increased security against injuries. Besides reducing the risk of internal injuries, the new windshield should also reduce the risk of Cuts caused by contact with broken glass can be safely avoided.

The safety glass pane according to the invention consists of a silicate glass pane and a plastic pane that sits on its abutment side and is connected to the silicate glass pane and is characterized in that the plastic pane has smaller dimensions than the silicate glass pane so that at least the greater part of its circumference is not in the frame is clamped and the safety glass pane is fastened to the protruding edge of the silicate glass pane, and that the plastic pane consists of a non-brittle, preferably thermoplastic material from 0.2 to 3 mm thick, the plastic in the temperature range from -20 to +401 C. Notched impact strength according to DIN 53453 of more than 5 kp - cm / cm2 and a tensile strength according to DIN 53455 (0.1 1 / o elongation limit) of more than 200 kp / cm2.

The thickness of the plastic pane depends essentially on the tensile strength and elongation of the material and should not exceed 3 mm , because the greater mass of the pane then increases the impact forces to unfavorable values.

The mode of action of a windshield with these features in the event of a collision is as follows: Provided that the impact speed of the head is sufficient to trigger the breakage of the silicate glass pane, i.e. at least about 10 to 15 km / h, the silicate glass pane is within a time span of less than Broken 1 msee after the head came into contact with the windshield as a result of the local deflection at the point of impact of the head. Since the plastic disk is not clamped in the frame and has the minimum properties specified above, it is not pierced by the head. Rather, a deformation wave emanates from the point of impact of the head, which spreads in the composite of plastic pane, adhesive and glass. As soon as this deformation wave reaches the edge of the windshield, the broken silicate glass pane is released in its entirety from its surround. This release from its enclosure, hereinafter also referred to as “release”, has always taken place after a period of 25 msee. After this release, there are no longer any dangerous deceleration forces acting on the head, because it can be assumed that at the moment when the silicate glass pane is completely loosened, the part of the windshield in the vicinity of the point of impact is accelerated to the own speed of the head at this point in time .

According to a first embodiment, the silicate glass pane consists of cooled, i. H. essentially stress-free silicate glass in a thickness of 2 to 8 mm and preferably 2.5 to 6 mm. In this embodiment, the release occurs when the plastic pane shears off the silicate glass pane, which breaks within 1 msec after the start of the impact, at its edge when the deformation wave emanating from the point of impact reaches the edge of the plastic pane. The investigations have shown that the forces necessary for this shearing off of the silicate glass pane, contrary to expectations, do not represent any significant additional stress for the head and the cervical spine and are therefore harmless if the shearing takes place in a sufficiently short time, i.e. i.e. when the deformation wave reaches the edge of the disc fast enough. The speed of propagation of the deformation wave is, among other things, a function of the modulus of elasticity or the modulus of shear as well as the thickness of the layers and the reflection ratios at the interfaces of the various layers.

According to another embodiment, the silicate glass pane consists of toughened glass with a thickness of 2.5 to 6 mm. In this embodiment, the release of the silicate glass pane at the edge is favored by the breakage of the pre-stressed pane, namely by the energy frozen in as a result of the pre-stressing, which is released when it breaks and the glass pane crumbles up to the edge into small crumbs, with the rate of breakage propagation 1500 m / see is. In this case, too, the speed of propagation of the deformation wave is responsible for the complete detachment and the progressive acceleration of the entire disk to the own speed of the head and is therefore also of crucial importance.

The specified minimum values for notched impact strength and tensile strength of the plastic material are required according to the invention so that the impact process occurring high deformation speeds and tensile stresses from the plastic disc be withstood without it breaking or becoming too plastically deformed. If these limits are respected, even the highest will be practical Occurring impact speeds no more piercing the pane. Next to The triggering thereby also becomes any direct contact between the human Body and the glass edges safely avoided. The specified dimensions of the silicate glass pane gives on the other hand a guarantee that this breaks before the deceleration forces assume dangerous values in the event of an impact.

In an expedient development of the invention, one with a windshield composed of non-toughened glass the glass pane along the circumference of the plastic pane with a predetermined breaking line, for example a notch made in the glass surface, whereby the shearing process is facilitated at this point.

The structure and advantage of the new safety glass pane are explained in more detail using the drawing, namely # i g. 1 the basic structure and # i g. 2 a comparison of several force-time curves in impact tests on different types of safety glass.

As shown in FIG. As can be seen, the side of the new pane facing away from the impact, that is to say the outside in the case of a windshield, is formed by the silicate glass pane 1 , which is held in the frame 2 along its circumference. The plastic pane 3 sits on the side facing the joint. It ends, preferably over its entire circumference, directly in front of the edging groove for the silicate glass pane 1, so that, in contrast to this, it is not clamped.

With the silicate glass pane 1 the plastic disc 3 is connected by means of a suitable adhesive layer. 5 The adhesive layer is expediently designed in such a way that, within the required temperature range, it absorbs the mechanical stresses that arise as a result of the different thermal expansion of glass and plastic.

On the basis of the minimum values specified according to the invention for the mechanical properties of the material used for the plastic disk 3 , it can be selected from the known plastics. For example, these conditions are met by a 0.25 mm thick film made of polyterephthalic acid ethylene glycol ester, a 1 mm thick film made of high molecular weight, thermoplastic polycarbonate of aromatic dihydroxy compounds, in particular bisphenylolalkanes, a 0.25 mm thick film made of amorphous polyamide of an aromatic bifunctional acid, in particular terephthalic acid, and an aliphatic alkyl-substituted bifunctional amine, in particular hexamethylenediamine, or a 0.5 mm thick film made from a plasticizer-free polyvinyl chloride.

The disk according to the invention is, as stated above, in full Scope meets the demands that arise on the basis of our own investigations and Knowledge about the tolerance limit for cervical vertebrae injuries. There However, such impact tests with natural preparations as those mentioned for the above Medical examinations used were not repeated any number of times can be, an experimental arrangement was developed, which is suitable for the implementation reproducible experiments. The results obtained with this test arrangement are directly related to the results obtained with natural preparations, so that they can draw conclusions about the properties of Allow safety glass panes in real impact accidents.

The chosen experimental set-up consists of a phantom body weighing a total of 20 kg. This consists of the actual impact body, namely a wooden head 19 cm in diameter and a weight of 14 kg arranged behind it. This weight of 14 kg represents the body mass participating in the impact and was chosen in this size because it can be assumed that about 20 to 25 1 / o of the body mass transfer its kinetic energy to the head and participate in the impact of the head. Between the wooden head and the weight, i.e. at the point that corresponds to the location of the cervical vertebrae, a measuring cell is arranged for measuring the forces that occur. In turn, it weighs 1 kg, so that the total weight of the impactor is 20 kg .

This phantom body is of different heights corresponding to the desired impact velocities on a test disc having the dimensions 50 - dropped 110 cm. The test panes are clamped at the edge under different conditions, in one case by placing a 56 kg frame, which corresponds to a clamping force of 120 kp / cm2, and in the other case by screwing the placed frame, creating an absolutely firm clamping, such as it is present, for example, when the windshield is glued into the body.

Such a rigid impact body has the same impact velocities and the same mass participating in the impact, provided a higher impact force and a shorter total impact time, i.e. H. Duration of impact force than with a natural preparation. This is due to the different behavior of the impacting mass, in which in the case of the rigid impactor the entire mass is involved in the impact from the beginning, while in the case of an impact of the human body, due to its deforinability, the body masses more or less one after the other on the impact participates.

Despite these differences in the measurement results, the essential Clearly show the advantage of the new lens with the described phantom test.

F i g. 2 shows six different force-time curves I to VL. Curves 1 to IV were determined in phantom tests, curves V and VI in an impact test with a natural preparation, ie. H. a natural cervical spine. All tests were carried out at an impact speed of 22.5 km / h, with the exception of test 1, in which the impact speed was 19.7 km / h. In this case, the speed had to be reduced so much because the disk was punctured at a higher speed and was therefore ruled out for a comparison. The clamping conditions were kept constant in all tests, and the clamping forces were 120 p1CM2.

The curves shown show the impact behavior of the following types of windshield: Curve 1 of a normal laminated safety glass pane made of two individual panes of glass, each 3.1 mm thick and a 0.38 mm thick polyvinyl butyral intermediate layer, Curves II and V of such a laminated glass pane with a polyvinyl butyral intermediate layer of 0.76 mm Thickness (curve II for rigid phantom, curve V for natural preparation), curve III of a pane constructed according to the invention with a 4.2 mm thick normally cooled silicate glass pane and a 0.25 mm thick polyester film, curve IV and VI of a pane also constructed according to the invention Disc with a 4.2 mm thick, but thermally toughened silicate glass pane and a 0.25 mm thick polyester film (curve IV for rigid phantom, curve VI for natural preparation).

All curves basically show the same characteristic curve, which is characterized by two shock phases, namely a high force peak at around 1 msec after the start of the shock and a subsequent second force component that extends over a significantly longer period of time compared to the first force peak. For the first shock phase, the peak of which represents the force required to break the silicate glass, the thickness of the windshield is essential. So that this peak force does not reach dangerous values, the thickness of the individual layers must not exceed the specified maximum values.

To make it easier to see, the course of the force peak is only shown in curve 1 and, for the rest, only the maximum value of this first force peak is indicated with I 'to VI'. After the silicate glass is broken, the force drops again very quickly. Although this first force peak is relatively high, it is not dangerous for internal injuries as long as it is below about 1500 kp, because the duration of action is extremely short.

On the other hand, the second force component is dangerous, and the invention relates to it precisely the shortening of this force component or the resulting shortening of the entire pushing process. This further course of the force curve is now next to the mass, among other things, through the plastic disc and the intermediate layer as well whose behavior in terms of plasticity and propagation of the deformation wave is determined.

Curve 1 itself can be disregarded, since a windshield with this structure will break through at a speed of the phantom body of around 20 to 25 km / h and such a windshield can therefore lead to the dangerous "ruff" at higher speeds. But even at these low speeds, the total impact time is 38 msee. It increases in curve II up to 60 msec, whereby at the same time the effective force, i. H. the mean force acting over the period of the second force component increases from 120 to 190 kp.

Compared with curve II (laminated safety glass, rigid phantom), curves III and IV (panes according to the invention, tests with rigid phantom) show the extent to which the total impact time is reduced by the invention: it is only about 16 for both cases msec. The level of force is not influenced in any remarkable way, but with the short burst times now achieved, it remains below the tolerance limit for macroscopically detectable cervical vertebrae injuries.

Curves V and VI, which were obtained from impact tests with natural cervical spine, show that, in the event of a real impact, the behavior of the cervical spine generally increases the peak times. On the other hand, however, they show with great clarity that this effective lengthening of the rush hour in turn depends on the structure of the pane and that it is significantly less in the case of a pane according to the invention than in the case of the laminated glass pane represented by curve V. The comparison of the curves shows that in real impact accidents the pane according to the invention represents an even more substantial improvement than the comparison of the phantom tests alone showed: the total impact time in the case shown is namely from 115 msec for a conventional laminated glass pane to less than 25 msec reduced.

Claims (2)

Claims: 1. Safety glass pane, in particular windshield for motor vehicles, made of a silicate glass pane and a plastic pane seated on its abutment side and connected to the silicate glass pane, characterized in that the plastic pane has smaller dimensions than the silicate glass pane, at least not on the larger part of its circumference is clamped in the frame and the safety glass pane is fastened to the protruding edge of the silicate glass pane, and that the plastic pane made of a non-brittle, preferably thermoplastic, from -20 to + 40'C has a notched impact strength according to DIN 53453 of at least 5kp-cm / cm? -and has a tensile strength according to DIN 53455 (0.1% elongation limit) of more than 200kp / cm2. 2. Safety glass pane according to claim 1, characterized in that the silicate glass pane consists of thermally stress-relieved glass in a thickness of 2 to 8 mm, preferably 2.5 to 6 mm. 3. Safety glass according to claim 1, characterized in that the silicate glass pane consists of toughened glass and has a thickness of 2.5 to 6 mm. 4. Safety glass pane according to claim 2 or 3, characterized in that the plastic pane consists of a 0.2 to 1 mm thick film made of ethylene glycol polyterephthalate. 5. Safety glass pane according to claim 2 or 3, characterized in that the plastic pane consists of a 0.5 to 2 mm, preferably 1 to 1.5 mm, thick film of high molecular weight, thermoplastic polycarbonate of aromatic dihydroxy compounds, in particular bisphenylalkanes. 6. Safety glass pane according to claim 2 or 3, characterized in that the plastic pane consists of a 0.2 to 1 mm thick film made of amorphous polyamide of an aromatic bifunctional acid, in particular terephthalic acid, and an aliphatic alkyl-substituted bifunctional amine, in particular hexamethylenediamine. 7. Safety glass pane according to claim 2 or 3, characterized in that the plastic pane consists of a 0.2 to 1 mm thick pane made of plasticizer-free polyvinyl chloride. 8. Safety glass pane according to one of claims 1 to 7, characterized in that the silicate glass pane and plastic pane are connected to one another by means of an elastic adhesive layer which absorbs the stresses occurring in the temperature range from -20 to + 40'C due to the different thermal expansion of glass and plastic . 9. Safety glass pane according to one or more of claims 1 to 8, characterized in that the glass pane is provided with a predetermined breaking line along the circumference of the plastic pane on its surface. 10. Safety glass pane according to claim 9, characterized in that the predetermined breaking line consists of a notch made in the glass surface.