Gap control

1. A device, comprising:

a flexible roller having a first surface;

a second surface opposite the first surface;

a gap between the first surface and the second surface; and

an actuator to flex the roller axially along a length of the roller while the roller is rotating to change the gap between the surfaces.

2. The device of claim 1 , comprising:

a sensor to measure the gap; and

a controller operatively connected to the sensor and to the actuator to flex the roller in response to a signal from the sensor.

3. The device of claim 2 , where the controller includes a processor and a processor readable medium with instructions thereon that when executed by the processor cause the controller to:

receive a signal from the sensor measuring the gap;

compare the measured gap to an acceptable range of gaps;

if the measured gap is not within the acceptable range, then signal the actuator to flex the roller to change the gap; and

repeating the receiving and comparing while the roller is rotating, and repeating the signaling if the measured gap is not within the acceptable range.

4. The device of claim 1 , where the actuator to flex the roller axially while it is rotating to change the gap between the surfaces includes a linear actuator to displace one or both ends of the roller radially while the roller is rotating.

5. The device of claim 4 , where the actuator is to simultaneously displace both ends of the roller radially while the roller is rotating.

6. A device, comprising:

a first roller having a first surface;

a second roller having a second surface opposite the first surface;

a gap between the first surface and the second surface;

a radially stationary first bearing supporting each end of the first roller;

a radially movable second bearing supporting each end of the first roller outboard from the first bearings; and

an actuator to move one or both of the second bearings radially with respect to the corresponding first bearing to change the gap between the surfaces.

7. The device of claim 6 , where the actuator is to move one or both of the second bearings while the first roller is rotating.

8. The device of claim 7 , where the actuator is to move both of the second bearings simultaneously while the first roller is rotating.

9. The device of claim 8 , comprising:

a sensor to measure the gap; and

a controller operatively connected to the sensor and to the actuator to move the second bearings in response to a signal from the sensor.

10. The device of claim 9 , where the controller includes a processor and a processor readable medium with instructions thereon that when executed by the processor cause the controller to:

receive a signal from the sensor measuring the gap;

compare the measured gap to an acceptable range of gaps;

if the measured gap is not within the acceptable range, then signal the actuator to move the second bearings to change the gap; and

repeating the receiving and comparing periodically or continuously while the roller is rotating, and repeating the signaling if the measured gap is not within the acceptable range.

11. A process to adjust a gap between two rollers, comprising:

rotating the rollers; and

while rotating the rollers, flexing one or both rollers axially along a length of the roller to change the gap.

12. The process of claim 11 , where the flexing includes displacing one or both ends of a roller radially.

13. The process of claim 12 , comprising, while rotating the rollers, detecting the gap outside an acceptable range and where the displacing includes displacing both ends of a roller in response to the detecting, to restore the gap to the acceptable range.