Apparatus for automatically centering an endless band trained over two rolls

Claim 1

An apparatus for automatically centering an endless band trained over a driven guide roll and a stretching roll, each roll having two ends wherebetween the endless band is centered in a starting position, the rolls having axes defining a plane in the starting position, the band having respective side edges adjacent respective ones of the roll ends, and including a nut-and-spindle mechanism at each end of the stretching roll, the nut of each mechanism being mounted on the roll end and the spindle of each mechanism being in threaded rotatable engagement with the nut but axially stationary whereby rotation of the spindle displaces the end in the plane, the centering apparatus comprising (a) a first hydraulic means for displacing either end of the stretching roll in the plane, the first hydraulic means including (1) a double-acting cylinder-piston unit at either end of the stretching roll and having a piston connected to a respective one of the spindles, (b) a second hydraulic means for displacing one of the ends of the stretching roll substantially perpendicularly to the plane, the second hydraulic means including (1) another double-acting cylinder-piston unit and (2) a frame pivotally mounted for swinging in a plane substantially perpendicular to the first-named plane, the nut-and-spindle mechanism at the one end being slidably mounted in the frame, and the other cylinder-piston unit being connected to the frame for swinging the frame in the perpendicular plane, (c) a sensor means disposed adjacent each of the side edges of the endless band and spaced therefrom when the band is centered, a respective one of the sensor means producing a control signal when a respective one of the side edges moves into contact therewith when the endless band deviates from the centered position between the ends of the rolls, and (d) a hydraulic fluid control circuit including a three-way solenoid valve for delivering hydraulic pressure to the double-acting cylinder-piston units of the first and second hydraulic means, the valve being responsive to the control signal to deliver hydraulic pressure to the cylinder-piston units for simultaneously displacing the one end of the stretching roll in both planes until the endless band has resumed its centered position.

Claim 2

An apparatus for automatically centering an endless band trained over a driven guide roll and a stretching roll, each roll having two ends wherebetween the endless band is centered in a starting position, the rolls having axes defining a plane in the starting position, the band having respective side edges adjacent respective ones of the roll ends, and including a nut-and-spindle mechanism at each end of the stretching roll, the nut of each mechanism being mounted on the roll end and the spindle of each mechanism being in threaded rotatable engagement with the nut but axially stationary whereby rotation of the spindle displaces the end in the plane, the centering apparatus comprising (a) a first hydraulic means for displacing either end of the stretching roll in the plane, the first hydraulic means including (1) a double-acting cylinder-piston unit at either end of the stretching roll and having a piston connected to a respective one of the spindles, (b) a second hydraulic means for displacing one of the ends of the stretching roll substantially perpendicularly to the plane, the second hydraulic means including (1) another double-acting cylinder-piston unit and (2) a frame pivotally mounted for swinging in a plane substantially perpendicular to the first-named plane, the nut-and-spindle mechanism at the one end being slidably mounted in the frame, and the other cylinder-piston unit being connected to the frame for swinging the frame in the perpendicular plane, (c) a sensor means disposed adjacent each of the side edges of the endless band and spaced therefrom when the band is centered, a respective one of the sensor means producing a control signal when a respective one of the side edges moves into contact therewith when the endless band deviates from the centered position between the ends of the rolls, and (d) a hydraulic fluid control circuit including a three-way solenoid valve for delivering hydraulic pressure to the double-acting cylinder-piston units of the first and second hydraulic means, the valve being responsive to the control signal to deliver hydraulic pressure to the cylinder-piston units for simultaneously displacing the one end of the stretching roll in both planes until the endless band has resumed its centered position.