Chain casing and chain tensioning assembly

1. A chain casing for encasing of a chain spanning a main chain sprocket and a driven chain sprocket, such as comprising two free chain parts, a pulling chain part and a returning chain part, of preferably a vehicle, such as a bicycle comprising a frame, the chain casing comprising:

a main chain sprocket cover element for covering of the chain at the main chain sprocket, such as a pedal spindle chain sprocket:

a pulling chain part cover element for enclosing of at least a part of a pulling chain part between a main chain sprocket and the driven chain sprocket;

a returning chain part cover element, positioned at a distance from said pulling chain part cover element, for enclosing of at least a returning chain part between the main chain sprocket and the driven chain sprocket; and

a chain tensioner cover element for covering of a chain tensioner assembly with the chain arranged therethrough.

2. The chain casing according to claim 1 comprising the chain tensioner assembly for providing tensioning to a part, such as the pulling chain part or the returning chain part, the chain tensioner assembly comprising:

a frame tube fastening element for fastening of the chain tensioner assembly to a frame tube,

a tensioning arm for providing a tensioning relative to the chain in which the tensioning arm is movably arranged relative to the frame tube fastening element,

tensioning means for providing a bias to the tensioning arm,

a first guide sprocket, for guiding of the chain, in which

at least one guide sprocket is arranged at the tensioning arm in order to provide a tensioning action relative to the chain, and in which

the first guide sprocket is functional for guiding under bias during use, of one of the chain parts as tensioned part, such that the tensioned part is longer than the other part.

3. The chain casing according to claim 1 comprising the first and a second guide sprocket, wherein a first of the first and second guide sprocket is arranged at a first side of the chain during use and a second of the first and second guide sprocket is arranged at a second side of the chain during use.

4. The chain casing according to claim 1 , comprising a front side support for supporting of the chain cover at the front side thereof at the main chain sprocket of the bicycle.

5. The chain casing according to claim 1 comprising a rear sprocket cover element.

6. The chain casing according to claim 1 comprising coupling means for coupling of cover elements with the chain tensioner assembly.

7. The chain casing according to claim 1 , in which the tensioning arm is rotatably arranged relative to the frame and or frame tube fastening element around a rotation heart line of the first and or the second guide sprocket.

8. The chain casing according to claim 1 , in which the tensioning arm is rotatably arranged relative to the frame.

9. The chain casing according to claim 1 comprising a biasing member.

10. The chain casing according to claim 1 , in which the chain tensioner cover element is arranged at the returning chain part.

11. The chain casing according to claim 1 comprising a mounting bracket.

12. The chain casing according to claim 11 , wherein the mounting bracket serves the purpose of adjustable or adaptable arrangement of the guides progress relative to the frame tube fastening element.

13. The chain casing according to claim 11 , wherein the mounting bracket serves the purpose of supporting the chain casing or a cover element thereof, such as the chain tensioner cover element.

14. The chain casing according to claim 11 , wherein the mounting bracket comprises support means for supporting of the chain casing or a cover element thereof, such as the rear chain sprocket cover element.

15. The chain casing according to claim 1 , wherein the chain tensioner assembly comprises support means for supporting the chain casing or a cover element thereof.

16. The chain casing according to claim 1 , wherein the tensioning arm is mountable to a fastening member, such as a fastening eye, by means of the frame tube fastening element, arranged at the frame.

17. The chain casing according to claim 1 , wherein the chain casing or a cover element thereof is mountable to a fastening member arranged at the frame.

18. The chain casing according to claim 16 , wherein the fastening member is attached to the frame by means of a screw connection.

19. The chain casing according to claim 16 , wherein the fastening member, such as the fastening eye, is mounted to the frame, such as the bottom stay thereof, by means of a welding connection.

20. The chain casing according to claim 1 , in which the tensioning arm extends substantially in a backward direction towards a rear axle of the bicycle from a fastening point and or a rotation points thereof relative to the frame.

21. The chain casing according to claim 1 comprising at least one pass through opening for a guide sprocket.

22. A chain tensioning assembly for providing a tensioning action to a chain part, the chain tensioning assembly comprising:

a frame tube fastening element for fastening of the chain tensioning assembly to a frame tube,

a tensioning arm for providing a tensioning relative to the chain in which the tensioning arm is movably arranged relative to the frame tube fastening element,

tensioning means for providing a bias to the tensioning arm,

a first guide sprocket, and a second guide sprocket, for guiding of the chain, in which

at least one guide sprocket is arranged at the tensioning arm in order to provide a tensioning action relative to the chain, and in which

the first guide sprocket and the second guide sprocket are functional for guiding under bias during use, of one of the chain parts as tensioned part, such that the tensioned part is longer than the other part, and

the frame tube fastening element for fastening of the chain tensioner assembly to the frame tube functioning in coaction with a fastening provision of the frame tube.