The present invention relates generally to an apparatus for aligning glass sheets in a production line and, particularly, to an apparatus for aligning sheets in a windshield bending operation.
The movement of glass sheets along a production line presents the problem of properly aligning the sheets at one or more work stations. One prior art aligning apparatus is disclosed in U.S. Pat. No. 3,638,564 in which a glass sheet is moved on a conveyor belt to an orientating station where a pair of edge engaging members and a pair of end engaging members orient the glass sheet longitudinally and laterally on the conveyor belt. Suction then is applied to hold the glass sheet in place while the conveyor belt moves the glass sheet to a work station where a predetermined pattern is applied by a silkscreen process. Each of the edge engaging members is hydraulically actuated and its relative position is manually adjustable by rotation of a threaded rod in a threaded sleeve to which a hydraulic cylinder is pivotly secured.
U.S. Pat. No. 3,701,643 and U.S. Pat. No. 3,992,182 both disclose aligning devices for positioning a moving glass sheet on a conveyor in a glass sheet production line. A pair of glass edge engagement members are located on opposite sides of the conveyor and move with the conveyor at the speed of the glass sheet. The engagement members are mounted on reciprocating carriages which move into and out of engagement with opposed edges of the glass sheets to align them.
U.S. Pat. No. 4,205,744 discloses a device for locating a windshield as it is being moved between two conveyor lines. A locating bar is manually adjustable on a threaded shaft to permit location of various lengths of windshields. A pair of locating pads are provided at the ends of the locating bar. A windshield is moved by a first conveyor into a holding structure which will rotate the windshield through 180.degree. and move it laterally to place it on the end of a second offset conveyor. During the lateral movement, one edge of the windshield comes into contact with one of the locating pads to position the windshield when it is placed on the second conveyor.
U.S. Pat. No. 4,367,107 discloses an apparatus for aligning a pair of bent glass sheets in an assembly station. The stacked glass sheets are moved into the assembly station and guide rollers engage the top and bottom edges and the end edges of the glass sheets. Both sheets are engaged by suction means and separated vertically while a flexible sheet layer is inserted between them. The glass sheets are reassembled to form a sandwich to be laminated.
U.S. Pat. No. 4,440,288 and U.S. Pat. No. 4,488,846 both disclose sensors for controlling the spacing of objects being moved between two conveyors. In the '288 patent, pans of dough are collected at a gate positioned at the end of a grouping conveyor being fed from an unloader conveyor. A pan sensor is moved along the grouping conveyor to determine when a moving pan is a predetermined distance from one or more stopped pans so that the speed of the conveyor can be reduced below a speed at which rising dough would fall when the moving pan strikes the stopped pan. The '846 patent discloses a device for controlling the movement of an auxiliary conveyor which is feeding glass sheets onto a main conveyor. The auxiliary conveyor is stopped until the distance between the last sheet on the main conveyor and the next sheet on the auxiliary conveyor is equal to a predetermined distance at which point the auxiliary conveyor is started to move the stopped glass sheet onto the main conveyor.
U.S. Pat. No. 4,493,412 discloses a device for positioning glass sheets on a conveyor platform prior to removal by a robot. A leading edge of the glass sheet engages fixed stop pins. Then a pair of transversely moveable tables advance to engage the opposed side edges of the article. Finally, adjustable pins are moved vertically and longitudinally into engagement with the trailing edge of the article to align the article in a precise position relative to a fixed reference point.
U.S. Pat. No. 4,458,628 discloses a turn table for supporting a glass panel and moving it relative to a robot glass panel is supplied to the turn table by a conveyor. The panel is located on the turn table by a plurality of positioning shoes hydraulically actuated in a vertical direction to engage the peripheral edges of the glass panel. The panel is then gripped with vacuum cups and the shoes are retracted before the turn table begins rotation.
In a laminated anti-laceration windshield production line, an outer curved sheet, an inner curved sheet and a curved cover plate are stacked with intervening plastic layers. These glass sheets must be properly oriented prior to the lamination process in order to provide proper edge alignment for accepting a vacuum ring. Since the glass sheets are curved, they are formed of decreasing length from the outer sheet to the inner cover plate such that the edges can be aligned. All of the prior art systems discussed above would have a problem properly aligning the three differently sized sheets.