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1. (WO2018042057) A TRANSMISSION
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Claims

1. A transmission having a torque input and a torque output, a plurality of drive members that are selectively engagable for sequentially changing gear ratio between the torque input and the torque output, the transmission also having a shaft provided with at least one shifting feature each of which comprises :

a drum having a track at least partially around its outer perimeter and arranged such that torque can be transferred thereto by rotating the shaft, the drum also capable of being moved along the length of the shaft;

a biasing mechanism for urging the drum towards a rest position along the length of the shaft; and

a drive member selector member provided in operative relation to said track, wherein by rotating the shaft the drive member selector member can be selectively urged into contact with a first said drive member for drivingly engaging therewith in a first torque connection or into contact with a second said drive member for drivingly engaging therewith in a second torque connection, the first and second torque connections being in opposite directions;

wherein each respective said shifting feature is configured such that when the drive member selector member thereof is drivingly engaged with a said drive member in either a positive or negative torque condition of the transmission in use, rotation of the shaft is blocked in one direction whereby a blocking condition occurs part way between an initial rotational position of the shaft and a rotational position in which the next sequentially selectable gear ratio would be caused to be engaged if the torque condition of the transmission was reversed.

2. The transmission of claim 1, wherein each respective said shifting feature is configured such that when the drive member selector member thereof is drivingly engaged with a said drive member in a positive torque condition of the transmission a downshift to a lower said selectable gear ratio is blocked.

3. The transmission of claim 2 wherein each respective said shifting feature is configured such that when the positive torque condition of the transmission is reversed the downshift to a lower said selectable gear ratio is no longer blocked.

4. The transmission of claim 1 or 2, wherein each respective said shifting feature is configured such that when the drive member selector member thereof is

drivingly engaged with a said drive member in a negative torque condition of the transmission an upshift to a higher said selectable gear ratio is blocked.

5. The transmission of claim 4 wherein each respective said shifting feature is configured such that when the negative torque condition of the transmission is reversed the upshift to a higher said selectable gear ratio is no longer blocked.

6. The transmission of any preceding claim, wherein each respective said shifting feature is configured such that in a blocking condition thereof a first blocking feature of the drum engages a second blocking feature of the

transmission for preventing rotation of the shaft in the direction blocked.

7. The transmission of claim 6, wherein the second blocking feature is received in a first space on one side of the drum such that an operative surface of the first blocking feature engages the second blocking feature.

8. The transmission of claim 7, wherein the first space is a recess in a side of the drum and the operative surface of the first blocking feature defines a side of this recess.

9. The transmission of claim 8, wherein the second blocking feature of the transmission is wedge shaped and an operative surface thereof lies in flush engagement with the first blocking feature.

10. The transmission of claim 4 wherein the first and second blocking features comprise respective operative surfaces which are configured to block a transition between a lower and a higher gear ratio when the transmission is in an adverse torque condition and the respective operative surfaces are further configured to allow a subsequent transition between a lower and a higher gear ratio when the transmission is no longer in an adverse torque condition.

11. The transmission of claim 6 wherein the first blocking feature of the selector drum comprises first and second angled surfaces, at least one of which is an operative surface configured to engage the second blocking feature of the transmission for preventing rotation of the shaft in the direction blocked.

12. The transmission of claim 6 or claim 11 wherein the second blocking feature of the transmission comprises first and second angled surfaces, at least one of which is an operative surface configured to engage the first blocking feature of the selector drum for preventing rotation of the shaft in the direction being blocked.

13. The transmission of claim 11 wherein the operative surface of the first blocking feature lies in a plane which is inclined to a longitudinal axis of the shaft.

14. The transmission of any of claims 11 to 13 wherein the operative surfaces of the first and second blocking features lie in a plane which is inclined to a longitudinal axis of the shaft.

15. The transmission according to any of claims 11 to 14 wherein the selector drum comprises two first blocking features.

16. The transmission according to claim 15 wherein the two first blocking features of the selector drum are diametrically opposed to each other.

17. The transmission according to claim 15 or 16 wherein the two first blocking features of the selector drum are positioned substantially opposite each other with respect to an axis of rotation of the selector drum.

18. The transmission according to claims 17 wherein the two first blocking features of the selector drum are substantially 1800 apart from each other with respect to an axis of rotation of the selector drum.

19. The transmission according to any of claims 12 to 18 wherein the

transmission comprises two second blocking features.

20. The transmission according to claim 19 wherein the two second blocking features of the transmission are diametrically opposed to each other.

21. The transmission according to claim 19 or 20 wherein the two second blocking features of the transmission are positioned substantially opposite each other around a circumference of the shaft.

22. The transmission according to claim 21 wherein the two second blocking features of the transmission are substantially 1800 apart from each other with respect to an axis of the shift shaft.

23. The transmission according to any of the preceding claims wherein the first blocking feature of the selector drum comprises a projection.

24. The transmission according to any of the preceding claims wherein the second blocking feature of the transmission comprises a projection.

25. The transmission according to any of claims 1 to 4 wherein the first blocking feature of the selector drum comprises a blocking face, wherein the blocking face extends around a portion of the external surface of the selector drum in a plane perpendicular to the axis of the rotation of the selector drum.

26. The transmission according to any of claims 11 to 25 wherein an operative surface of the first blocking feature defines a bottom of a recess in a side of the selector drum.

27. The transmission according to any of claims 1 to 4 wherein the second blocking feature of the transmission comprises at least one roller.

28. The transmission according to claim 27 wherein the second blocking feature of the transmission comprises two rollers.

29. The transmission according to claim 28 wherein the two rollers are diametrically opposed to each other.

30. The transmission according to claim 28 or 29 wherein the two rollers are positioned substantially opposite each other around a circumference of the shaft.

31. The transmission according to claim 30 wherein the two rollers are

substantially 1800 apart from each other with respect to an axis of the shift shaft.

32. The transmission of any of claims 6 to 9, wherein each respective said 5 shifting feature is configured such that in a pre-synchronisation condition

thereof upon changing gear ratio in use, the second blocking feature is received in a second space on the other side of the first blocking feature.

33. The transmission of claim 32, wherein the second space is another recess in 10 the side of the drum.

34. The transmission of claim 32 or 33, wherein the second space is a V-shaped recess.

!5 35· The transmission of any of claims 6 to 34, wherein the second blocking

feature of the transmission forms part of a casing of the transmission.

36. The transmission of any preceding claim wherein each respective shifting feature is configured such that when the drive member selector member thereof 0 is drivingly engaged with the said drive member in either a positive or negative torque condition of the transmission in use, rotation of the shaft is blocked in one direction whereby the blocking condition occurs and the blocking condition subsequently no longer occurs when the torque condition of the transmission is reversed.

5

37. A transmission substantially as heretofore described and/or as shown in Figs. 2. 4a to 4c, 6a to 6c, 7a to 7c and 8a to 8c.

38. A vehicle comprising a transmission according to any preceding claim. 0