Detection system

1. A method for detection of objects in a screening device comprising one or more screening decks, said method comprising:

transmitting signals from an ultrasound sensor in relation to a mass flow from the one or more screening decks, said ultrasound sensor being arranged such that it can detect objects leaving said at least one screening deck; and

differentiating, by a control unit operably connected to the ultrasound sensor, between signals from the sensor resulting from the material to be screened and signals from the sensor resulting from a foreign object, such as a dislodged screening module or liner element, by applying one or more predefined threshold values, wherein a threshold value is based on a time an object is present in the range of the sensor.

2. The method according to claim 1 further comprising the step of:

controlling an operation parameter of the screening device based on an outcome of said comparison of signals received by said control unit from said ultrasound sensor with said threshold values.

3. The method according to claim 1 , wherein the sensor is arranged to detect objects present outside a predefined area adjacent to a discharge of the at least one screening deck.

4. The method according to claim 3 , wherein the predefined area is at least in part defined by a ballistic trajectory.

5. The method according to claim 4 , wherein the ballistic trajectory has a starting point at or near a discharge end of the at least one screening deck.

6. The method according to claim 1 , wherein the ultrasound sensor is a rangefinder.

7. The method according to claim 1 , wherein said ultrasound sensor is arranged on a structure which is independent of the screening device.

8. The method according to claim 1 , further comprising the step of determining whether or not a foreign object, such as a dislodged screening module or liner element, is present in the mass flow based on a comparison of signals received by said control unit from said ultrasound sensor with said predefined threshold values.

9. The method according to claim 8 , further comprising the step of controlling an operation parameter of the screening device based on an outcome of said comparison of signals received by said control unit from said ultrasound sensor with said predetermined threshold values.

10. A method for detection of objects in a screening device comprising at least one screening deck, said method comprising:

transmitting signals from an ultrasound sensor in relation to a mass flow from the at least one screening deck, the ultrasound sensor being arranged such that it can detect objects leaving the at least one screening deck outside of a predefined area that is adjacent to a discharge of the at least one screening deck, wherein the mass flow of the screened material will be found within the predefined area after leaving the at least one screening deck; and

determining, by a control unit arranged to receive signals from the ultrasound sensor, whether or not a foreign object, such as a dislodged screening module or liner element, is present in the mass flow based on a comparison of signals received by the control unit from the ultrasound sensor.

11. The method according to claim 10 , further comprising the steps of:

defining threshold values for the signal from the ultrasound sensor; and

determining whether or not a foreign object is present in said mass flow by applying the threshold values.

12. The method according to claim 10 , wherein the ultrasound sensor is a rangefinder.

13. The method according to claim 10 , wherein said ultrasound sensor is arranged on a structure which is independent of the screening device.

14. The method according to claim 11 , further comprising the step of:

determining whether or not a foreign object, such as a dislodged screening module or liner element, is present in the mass flow based on a comparison of signals received by the control unit from the ultrasound sensor with the defined threshold values.

15. The method according to claim 14 , further comprising the step of controlling an operation parameter of the screening device based on an outcome of the comparison of signals received by the control unit from the ultrasound sensor with the defined threshold values.