Method and apparatus for adjusting media positioning and indexing using an encoder in an image forming device

1. A method for indexing a lift plate in an image forming device, comprising:

driving a motor in a first direction to drive a pick mechanism for feeding media from a stack of media sheets on a raisable lift plate such that as media is fed the height of the pick mechanism decreases;

when the height of the pick mechanism falls below a predetermined level, driving the motor a predetermined amount of rotation in a second direction opposite the first direction to raise the lift plate in order to raise the pick mechanism to a desired pick height;

advancing the media with a roller disposed downstream from the pick mechanism;

after a leading edge of the media reaches the roller, stopping the drive of the motor in the first direction; and

when the height of the pick mechanism falls below the predetermined level, beginning the drive of the motor in the second direction to raise the lift plate before a trailing edge of the media sheet being fed disengages from the pick mechanism.

2. The method of claim 1 , further comprising determining if the height of the pick mechanism has fallen below the predetermined level based on whether a sensor adjacent to the pick mechanism has changed from a first state to a second state as a result of the decrease in height of the pick mechanism.

3. The method of claim 2 , wherein the state of the sensor is changed by a flag arm extending from the pick mechanism.

4. The method of claim 2 , wherein the state of the sensor is analyzed between each media feed when the motor is not being driven in the first direction and ignored during each media feed when the motor is being driven in the first direction.

5. The method of claim 2 , further comprising:

when the height of the pick mechanism falls below the predetermined level, driving the motor in the second direction to raise the lift plate until the increase in height of the pick mechanism changes the sensor from the second state to the first state; and

after the increase in height of the pick mechanism changes the state of the sensor from the second state to the first state, performing the step of driving the motor the predetermined amount of rotation in the second direction to further raise the lift plate in order to raise the pick mechanism to the desired pick height.

6. The method of claim 1 , wherein the predetermined amount of rotation of the motor in the second direction is determined using an output from an encoder wheel coupled to the motor.

7. The method of claim 1 , wherein when the motor is driven the predetermined amount of rotation in the second direction, the lift plate is raised between about 1 mm and about 10 mm.

8. A method for indexing a lift plate in an image forming device, comprising:

driving a motor in a first direction to drive a pick mechanism for feeding media from a stack of media sheets on a raisable lift plate such that as media is fed the height of the pick mechanism decreases;

when the height of the pick mechanism falls below a predetermined level, driving the motor a predetermined amount of rotation in a second direction opposite the first direction to raise the lift plate in order to raise the pick mechanism to a desired pick height; and

determining if the height of the pick mechanism has fallen below the predetermined level based on whether a sensor adjacent to the pick mechanism has changed from a first state to a second state as a result of the decrease in height of the pick mechanism,

wherein the state of the sensor is analyzed between each media feed when the motor is not being driven in the first direction and ignored during each media feed when the motor is being driven in the first direction.

9. The method of claim 8 , wherein the state of the sensor is changed by a flag arm extending from the pick mechanism.

10. The method of claim 8 , further comprising:

when the height of the pick mechanism falls below the predetermined level, driving the motor in the second direction to raise the lift plate until the increase in height of the pick mechanism changes the sensor from the second state to the first state; and

after the increase in height of the pick mechanism changes the state of the sensor from the second state to the first state, performing the step of driving the motor the predetermined amount of rotation in the second direction to further raise the lift plate in order to raise the pick mechanism to the desired pick height.

11. The method of claim 8 , wherein the predetermined amount of rotation of the motor in the second direction is determined using an output from an encoder wheel coupled to the motor.

12. The method of claim 8 , wherein when the motor is driven the predetermined amount of rotation in the second direction, the lift plate is raised between about 1 mm and about 10 mm.

13. A method for indexing a lift plate in an image forming device, comprising:

driving a motor in a first direction to drive a pick mechanism for feeding media from a stack of media sheets on a raisable lift plate such that as media is fed the height of the pick mechanism decreases;

determining if the height of the pick mechanism has fallen below the predetermined level based on whether a sensor adjacent to the pick mechanism has changed from a first state to a second state as a result of the decrease in height of the pick mechanism;

when the height of the pick mechanism falls below the predetermined level, driving the motor in a second direction opposite the first direction to raise the lift plate until the increase in height of the pick mechanism changes the sensor from the second state to the first state; and

after the increase in height of the pick mechanism changes the state of the sensor from the second state to the first state, driving the motor a predetermined amount of rotation in the second direction to further raise the lift plate in order to raise the pick mechanism to a desired pick height.

14. The method of claim 13 , wherein the state of the sensor is changed by a flag arm extending from the pick mechanism.

15. The method of claim 13 , wherein the predetermined amount of rotation of the motor in the second direction is determined using an output from an encoder wheel coupled to the motor.

16. The method of claim 13 , wherein when the motor is driven the predetermined amount of rotation in the second direction, the lift plate is raised between about 1 mm and about 10 mm.