Device and method for detecting paper sheets on a pallet including a point of reflection displacement

1. A device for detecting the presence of paper sheets, in particular sheets of securities or banknotes, on a pallet, wherein the device has:

at least one optical sensor, which emits a light beam, inclined at an angle in relation to the surface of the pallet, and which irradiates the surface of the pallet at a point of reflection,

means for displacing the point of reflection by a predetermined distance over the surface of the pallet between a start position and an end position, and

means for analyzing the light signal generated by reflection for sensing the presence of sheets during the displacement of the point of reflection and for generating a signal dependent on a detection result.

2. The device as claimed in claim 1 , wherein the angled inclination is approximately 40°.

3. The device as claimed in claim 2 , wherein it contains two symmetrical sensors.

4. The device as claimed in claim 1 , wherein the means which allow the point of reflection to be displaced are formed at least by a compressed-air cylinder which acts on a support, on which each sensor is fastened, such that the sensor is displaced parallel to the surface of the pallet.

5. The device as claimed in claim 1 , wherein the displacement takes place over a predetermined distance.

6. A method for sensing a ream of paper, in particular a ream of securities or banknotes, on a pallet by means of at least one optical sensor which emits a light beam onto a point of reflection, the process comprising the following steps:

switching on the sensor,

displacing the point of reflection,

analysing a reflected light signal for sensing the presence of sheets,

stopping the movement of the point of reflection,

emitting a suitable signal depending on the result of the sensing step,

switching off the sensor.

7. The method as claimed in claim 6 , wherein the displacement of the point of reflection takes place by linear displacement of the sensor by a predetermined distance running parallel to the surface of the pallet.

8. The method as claimed in claim 6 , wherein the predetermined distance is greater than the dimension of a hologram provided on the paper.

9. The method as claimed in claim 6 , wherein it uses two symmetrical sensors.

10. The device as claimed in claim 1 , wherein the distance between starting position and end position is adjustable.

11. The device as claimed in claim 1 , comprising a gripper system for correcting the position of the pallet depending on the result of the detection.

12. The device as claimed in claim 11 , wherein the correction carried out by the gripper system can be determined by the sensors.

13. The device as claimed in claim 5 , wherein the displacement taking place over a predetermined distance is superior in size to that of a hologram present on the sheets.