Stock material or miscellaneous articles – Structurally defined web or sheet – Nonplanar uniform thickness material
Reexamination Certificate
2002-05-07
2004-06-15
Loney, Donald J. (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Nonplanar uniform thickness material
C428S212000, C065S102000
Reexamination Certificate
active
06749926
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a bent glass sheet suitably used for a vehicle window, especially for a vehicle window having a mechanism to move the windowpane along the surface direction.
BACKGROUND OF THE INVENTION
Typical windows for front doors of automobiles are opened and closed by moving the windowpanes along the surface direction of the vehicle bodies. In such a case, windowpanes are shaped in general to be flat or cylindrical. A cylindrical glass sheet slides along a direction with a predetermined curvature radius and reciprocates between the inside of the door and the opening.
Recently, glass sheets bent both in the sliding direction and in the longitudinal direction of the vehicle are required to improve consistency with the vehicle's design. Such a bent glass sheet is often called a glass sheet having a “complex curved” surface or a “two directional” bent glass sheet.
A surface of such a bent glass sheet is required to be bent with high accuracy along a predetermined curved surface. When the surface has a point at which the curvature varies, reflected images on the glass surface will be distorted in the vicinity of the point. Especially, such a distortion of reflected images should be removed from windowpanes composing a sideline of an automobile.
A bent glass for a rear window or the like of such an automobile is not bent to have a constant curvature. Therefore, even if some regions of the bent glass sheet have curvatures different from a predetermined curvature, the influence is difficult to identify visually. On the other hand, since a glass sheet that is bent in two directions to have identical curvatures will provide extremely natural reflected images as a whole, even partial changes in the curvature and defects on the surface will be conspicuous.
When the glass sheet is used for a door window, preferably the windowpane slides while it is maintained at a certain position as much as possible in an opening (slit) formed at the upper end of the door housing. A wider slit for a margin may permit rainwater or dust to enter the door housing easily. Weatherstrips are provided for the slit in order to prevent passage of foreign objects. However, if the windowpane is leaned excessively in one direction, friction between the weatherstrips and the windowpane becomes unduly large, or a space is created between these them.
Because of these conditions, if a glass sheet for a vehicle window is bent in two directions, it should be processed with higher accuracy when compared to a bent glass sheet with a further complicated shape.
Various methods to bend glass sheets have been proposed. Surprisingly however, two-directional bent glass sheets with accuracy to respond to the demands of the market have not been manufactured, even though such glass sheets are required from a design viewpoint. This results from the limited accuracy in the conventional bending methods.
A typical method to bend a glass sheet is press molding. This method is suitable for mass-production of bent glass sheets with a complicated shape that are used for rear windows or the like of automobiles. However, in a glass sheet
503
that is pressed while being supported with a ring mold
501
and being attracted by a mold
502
, a central portion
504
hangs down slightly (
FIG. 33B
) before it is cooled. If the degree of deformation caused by gravity could be expected, the shape of the mold might be adjusted finely. However, since there are various factors determining the deformation, precise expectation of the deformation degree is substantially impossible. Similarly, in press-molding using tongs, the deformation degree is difficult to expect. In another method, a mold is arranged entirely along both surfaces of a glass sheet to be bent before cooling the bent glass sheet while keeping the glass sheet along the mold. This method also might be available. However, since a great internal stress remains in the glass sheet, the bent glass sheet may be deformed when it is released from the mold. In conclusion, problems should be solved to manufacture with accuracy a glass sheet that is bent in two directions by press-molding.
U.S. Pat. No. 4,123,246 and JP-A-3-174334 propose a method to heat glass sheets while conveying them by rollers in order to bend the glass sheets along the rollers. However, the glass sheets will be bent intermittently if they are bent by using rollers arranged above and below the conveying passage. More specifically, the glass sheets will be bent and folded in part while they are bridged between pairs of rollers, especially in initial stages of the bending process. When the glass sheet is bent also in a direction perpendicular to the conveying direction, the rollers should be bent before being arranged. It is difficult to bend the respective rollers arranged along the conveying direction with high accuracy and rotating the rollers in that state. Bending glass sheets by sandwiching them with rollers is excellent in view of mass production but it cannot provide sufficient processing accuracy.
JP-A-5-9037 proposes a method of conveying glass sheets while supporting the same sheets with a gas spouting upwards from a hearth bed arranged below. The gas heats the glass sheet at the same time, and the sheet sags down along the hearth bed. In this manner, defects due to roller “bending/folding” or due to contact with rollers can be prevented. However, the passage to convey glass sheets should be inclined to bend the glass sheet in two directions and thus, conveying glass sheets while keeping a stable orientation is difficult. When the glass sheet cannot be oriented stably, accuracy in forming the glass sheet also will deteriorate. The method of conveying and bending glass sheets by spouting a gas is suitable for providing a simpler form, but the process accuracy is sacrificed when a glass sheet is bent in two directions.
As mentioned above, it has not been considered in any conventional bending methods that a glass sheet is cooled (quenched or annealed) after a bending process while keeping the bent shape accurately, nor have any ideas relating to such methods been disclosed.
Because of the above-mentioned reasons, no methods to produce glass sheets bent in two directions with accuracy have been established. In the above references, manufacturing of glass sheets bent in two directions is attempted. The glass sheets according to the references may be bent in two directions as a whole, but some regions thereof are not bent as desired when observed in detail, because of limitations resulting from the methods themselves. As a result, bent glass sheets arranged in the sides of an automobile such as a door glass are shaped in a simple manner actually.
JP-A-11-500796 proposes to use door glass made of a glass sheet that is bent to have a more complicated shape than a glass sheet bent in two directions. This reference discloses a mechanism to lift a bent glass sheet of an imaginary barrel-shaped sleeve surface along the longitudinal direction of the vehicle. This mechanism allows a glass sheet of a barrel-shaped sleeve surface to lift while swiveling to maintain the lower side of the glass sheet in parallel. In such a bent glass sheet with complicated shape, distortion of reflected images would be less distinguishable.
However, a complicated lifting mechanism should be provided to a space formed inside the door (door housing) in order to lift the glass sheet. Such a complicated mechanism will cause troubles and raise costs. For swivel-lifting a glass sheet of a barrel-shaped sleeve surface, a guide rail that is bent three-dimensionally so as to describe a spiral is needed. If the guide rail has complicated curved lines, a wire is also bent at a point, and the durability of the wire can be negatively affected due to friction with the guide rail. In some cases, changing tension of the wire hinders smooth operation. Positions of the glass sheet at the door slit will also vary considerably.
For the above-mentioned reasons, the market's needs for glass sheets that are bent accurat
Loney Donald J.
Merchant & Gould P.C.
Nippon Sheet Glass Company Limited
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