Sheet-straightening mechanism

Claim 2

Method of straightening individual sheets of material carried by conveyor means comprising the steps of establishing the difference in time between passages of opposite ends of the leading edge of each side of the sheet past a reference location intermediately located on the conveyor means; controlling the speed of each side of the sheet independently of the conveyor means; and differentially moving the sides of each sheet in response to said difference in time by an amount and in a direction such that the sheet is aligned with said reference location on the conveyor means wherein the side of the sheet which trails is accelerated momentarily to a higher speed for a period of time related to the difference between the time each side of said sheet passes said reference location.

Claim 3

Apparatus for straightening individual sheets of material carried by a conveyor comprising means on each side of the conveyor for detecting the passage of the leading edge of the sheet; timing means responsive to said sensing means for developing a signal representing the difference in time between the passages of opposite ends of the leading edge of each side of the sheet relative to said detecting means; and means mounted on each side of the conveyor for moving the adjacent side of the sheet independently of the conveyor, said means being controlled by said timing signal so that, as the sheet passes through said moving means, the edges of the sheet may be moved differentially and the sheet straightened relative to the conveyor.

Claim 4

Apparatus for straightening individual sheets of material carried by a conveyor comprising means on each side of the conveyor for detecting the passage of the leading edge of the sheet; timing means responsive to said sensing means for developing a signal representing the difference in time between the passages of opposite ends of the leading edge of each side of the sheet relative to said detecting means; and means mounted on each side of the conveyor for moving the adjacent side of the sheet independently of the conveyor, said means being controlled by said timing signal so that, as the sheet passes through said moving means, the edges of the sheet may be moved differentially and the sheet straightened relative to the conveyor.

Claim 5

Apparatus for straightening individual sheets of material carried by a conveyor comprising means on each side of the conveyor for detecting the passage of the leading edge of the sheet including switches mounted on each side of the conveyor, said switches being actuated by the leading edge of each sheet; timing means responsive to said sensing means for developing a signal representing the difference in time between the passage of opposite ends of the leading edge of each side of the sheet relative to said detecting means; and means mounted on each side of the conveyor for moving the adjacent side of the sheet independently of the conveyor; said moving means being controlled by said timing signal so that, as the sheet passes through said moving means, the edges of the sheet may be moved differentially and the sheet straightened relative to the conveyor; said moving means including a two-speed motor having drive means mounted to engage each side of the sheet after it passes said switch means, said motor having a first speed which moves the sheet at the same velocity as the conveyor, and a second speed which will accelerate the sheet to a higher velocity relative to the conveyor; said timing signal being operative to energize said motor on that side of the conveyor where the leading edge of the sheet trails so that said motor operates at the higher speed for a time period which is determined by the difference in time between the actuation of each of said switch means.

Claim 6

Apparatus for straightening individual sheets of material carried by a conveyor comprising means on each side of the conveyor for detecting the passage of the leading edge of the sheet including switches mounted on each side of the conveyor, said switches being actuated by the leading edge of each sheet; timing means responsive to said sensing means for developing a signal representing the difference in time between the passage of opposite ends of the leading edge of each side of the sheet relative to said detecting means; and means mounted on each side of the conveyor for moving the adjacent side of the sheet independently of the conveyor; said moving means being controlled by said timing signal so that, as the sheet passes through said moving means, the edges of the sheet may be moved differentially and the sheet straightened relative to the conveyor; said moving means including a two-speed motor having drive means mounted to engage each side of the sheet after it passes said switch means, said motor having a first speed which moves the sheet at the same velocity as the conveyor, and a second speed which will accelerate the sheet to a higher velocity relative to the conveyor; said timing signal being operative to energize said motor on that side of the conveyor where the leading edge of the sheet trails so that said motor operates at the higher speed for a time period which is determined by the difference in time between the actuation of each of said switch means.

Claim 7

Apparatus as defined in claim 3 wherein said timing means includes a capacitor which begins charging upon the closure of that switch sensing the end of the leading edge of the sheet which first arrives at said detecting means, and which ceases charging and begins discharging at a predetermined rate upon the closure of that switch sensing the end of the heading edge of the sheet which trails; and means sensing the magnitude of the charge on said capacitor to energize said motor on that end of the sheet which trails at the higher speed for a time period which is determined by the quantity of the charge on said capacitor.