Low Paper Sensing Using Paper Roll Rotation
Original Publication Date: 2000-Sep-01
Included in the Prior Art Database: 2003-Jun-18
In point of sale printers it is desirable to detect that the paper supply is nearly exhausted. This is particularly important because of the inconvenience and possible loss of sales if a check-out lane were held up while paper is changed or a receipt is reprinted. Traditionally, POS printers use a lever actuated switch or side looking optical sensor that switch when the diameter of the paper roll is below a preset limit. These systems are not very accurate, resulting in wasted paper, and can not detect the ongoing status of the paper supply. Ongoing status would be important if the printer is scheduled to print a long report and might be unattended. It is also desirable to be able to detect the occurrence of a paper jam. This also would save paper and time if the printer were printing unattended. This invention consists a printer that supports the Paper Roll on Spindles that rotate as paper is fed through the printer. To facilitate paper loading, spindles are sprung together. The Paper Roll is inserted between the spindles until the spindle centers align with the Core of the Paper Roll. The attached figure shows a Pressure Spindle and a Driven Spindle. The distance between the outer extremes of the flanges is greater than the width of the Paper Roll, but the Inner Flanges are separated less than the width of the Paper Roll. The Paper Roll can be easily inserted between the spindles which spring apart. As the Paper Roll encounters the Independently Sprung Center a Cone Center springs out of the way until it springs into the whole in the Paper Roll core. This process is a simple, one handed operation. Once in place, the Paper Roll can spin Driven Spindle as paper is fed through the printer. The Driven Spindle has a simple molded emitter geared to it which interrupts an Optical Sensor as paper in fed during printing. The printer mechanism is omitted for clarity.