Force measuring unit and system for measuring chain forces

1. A force measuring unit for measuring a force applied to an individual chain link of a chain strand used in underground mining applications, the chain strand including a plurality of chain links engaging each other, each chain link of the plurality of chain links having a first chain link leg and a second chain link leg opposite to the first chain link leg, the force measuring unit comprising:

a housing having a first end configured to be contacted by the first chain link leg and a second end configured to be contacted by the second chain link leg, the housing being elastically deformable such that a distance variation between the first chain link leg and the second chain link leg is possible;

a distance measuring device accommodated within the housing and configured to measure an actual distance between the first chain link leg and the second chain link leg, the distance measuring device including a first unit part configured to be contacted by the first chain link leg and a second unit part configured to be contacted by the second chain link leg;

a magnet provided at the first unit part; and

a magnetic field sensor provided at the second unit part and configured to detect a magnetic field caused by the magnet,

wherein, due to the distance variation between the first chain link leg and the second chain link leg caused by the force applied to the chain strand, the first unit part and the second unit part move relative to each other, such that the actual distance between the first and second chain link legs can be measured, and

wherein, due to the relative movement between the first unit part and the second unit part, the magnet moves relative to the magnetic field sensor causing a variation of the detected magnetic field.

2. The force measuring unit of claim 1 , further comprising a potting material potted within a free space provided between the housing and the first and second unit parts positioned within the housing.

3. The force measuring unit of claim 1 , wherein the second unit part includes a recess configured to at least partially accommodate the magnet.

4. The force measuring unit of claim 1 , further comprising a processor configured to receive and process signals provided by the distance measuring device.

5. The force measuring unit of claim 4 , further comprising a memory configured to at least temporarily store data processed by the processor.

6. The force measuring unit of claim 1 , further comprising an electric power supply configured to provide electric power to the distance measuring device.

7. The force measuring unit of claim 1 , further comprising a transmitting unit configured to transmit signals provided by the distance measuring device to a signal receiving unit remotely disposed with respect to the force measuring unit.

8. The force measuring unit of claim 2 , wherein at least one of the housing and the potting material includes an elastomeric material.

9. The force measuring unit of claim 1 , wherein the housing includes a recess configured to accommodate a filling element matching with the recess, when the force measuring unit is mounted to a chain link of the plurality of chain links.

10. The force measuring unit of claim 1 , further comprising: at least one of an acceleration sensor configured to detect an acceleration of the chain link; and a temperature sensor configured to detect a temperature of the chain link.

11. A chain force measuring system for measuring a chain force of a chain strand of an extraction device or a plow device used in underground mining applications, the chain force measuring system comprising:

at least one force measuring unit in accordance with claim 1 , the at least one force measuring unit being mounted to a chain link of the chain strand;

at least one signal receiving unit configured to receive signals from the at least one force measuring unit; and

a control unit communicating with the at least one signal receiving unit and configured to process the signals provided by the at least one signal receiving unit for deriving the chain force.

12. An extraction device for mining the extraction device comprising:

a first drive station including a first sprocket;

a second drive station spaced apart from the first drive station and including a second sprocket;

at least one chain strand including a plurality of chain links engaging each other and running around the first sprocket and the second sprocket to form an upper run and a lower run; and

a chain force measuring system in accordance with claim 11 .

13. The extraction device of claim 12 , further comprising a tensioning means for tensioning the at least one chain strand by changing the distance between the first sprocket and the second sprocket in dependency on the derived chain force.

14. A method for determining a force of at least one chain link of a chain strand including a plurality of chain links engaging each other, each chain link having a first chain link leg and a second chain link leg opposite to the first chain link leg the method comprising:

transferring a distance variation between the first chain link leg and the second chain link leg into a relative movement between a magnet coupled to the movement of the first chain link leg and a magnetic field sensor coupled to the movement of the second chain link leg;

measuring a magnetic field caused by the magnet; and

based on the measured magnetic field, deriving the force at the at least one chain link.