Patent ID: 7549814

Claim:
A low paper sensor mechanism for a printer comprising: a housing, including first and second faces and sidewalls formed to support the first and second faces in opposition to one another, and having pairs of corresponding guide members defined in each of the first and second faces; first and second support rollers, rotatable about a first and second rotational axis, respectively, being supported within the housing by the guide members to support a portion of a paper supply roll from which a supply of paper is dispensed horizontally from the top of the paper roll until a diameter of the paper supply roll is less than a distance between the first and second support rollers, the first and second support rollers being further configured to move from first to second positions of the guide members during an entire time the paper supply roll is expended and a diameter of the paper supply roll decreases, the second positions being closer to the portion of the supply of the paper being dispensed; first and second biasing members, coupled to the housing, to expansively bias the first and second support rollers toward the second position in opposition to a force of a mass of the paper supply roll; and a detection device, including a light emitting element and a light detecting element, disposed adjacent to the first and second support rollers within the housing, the light emitting element being disposed in a line of sight of the light detecting element, wherein: a current rate of the movement of the first and second support rollers is directly proportional to the corresponding current diameter of the paper supply roll, and, when the first and second support rollers reach the second position and once the diameter of the paper supply roll decreases sufficiently such that the diameter of the paper supply roll is less than the distance between the first and second support rollers, the paper supply roll drops toward the detection device and disrupts the line of sight between the light emitting element and the light detecting element.