A tensioner (10) for an endless loop power transmission member can include the assembly of a plunger (12) operably engageable with an endless loop power transmission member, and a piston (14) guiding the plunger (12) for sliding coaxial movement in a direction of the endless loop power transmission member and defining an oil reservoir (26) for receiving hydraulic fluid. A bearing (28) can have bearing balls (30) located in a counter bore (32) coaxial with piston bore (34). The counter bore (32) can have a steep taper (36) on which the bearing balls (30) ride, such that as the plunger (12) moves in an extending direction, the bearing balls (30) move out of the counter bore (32) allowing free extending movement of the plunger (12), and as the plunger (12) moves in a retracting direction, the bearing balls (30) are driven down into the steep taper (36) preventing the plunger (12) from retracting.

In a first aspect, a tensioner is provided which includes: an arm, including a pivot mount; a pulley rotatably mounted to the arm; and a strut pivotally connected to the arm. The strut includes: a base, having a pivot mount; a first body moveable relative to the base; a first resilient element connected between the base and the first body, the first resilient element having a first stiffness coefficient; a second body moveable relative to the first body, the second body having a pivot mount; a second resilient element connected between the first body and the second body, the second resilient element having a second stiffness coefficient that is lower than the first stiffness coefficient; and an actuator, connected to the base and first body, for selectively moving the first body towards the base and compressing the first resilient element.

An earth working machine (10), encompassing a drive motor (42) and a working apparatus (22) drivable by the drive motor (42) so as to move rotationally, the drive motor (42) being connected to the working apparatus (22), for transfer of a torque, with interposition of a shiftable transmission (50; 150) comprising at least two gearing stages having different torque transfer ratios, is characterized in that by means of a first gearing stage of the shiftable transmission (50), an input shaft (48), coupled on the input side to the drive motor (42), of the shiftable transmission (50) is connectable in torque-transferring fashion directly to an output shaft (52), coupled on the output side to the working apparatus (22), of the shiftable transmission (50) so as to rotate together at the same rotation speed; and by means of a second gearing stage of the shiftable transmission (50), the input shaft (48) is connectable in torque-transferring fashion, with interposition of a transmission assemblage (64), to the output shaft (52) so as to rotate together at different rotation speeds.

An earth working machine (10), encompassing a drive motor (42) and a working apparatus (22) drivable by the drive motor (42) so as to move rotationally, the drive motor (42) being connected to the working apparatus (22), for transfer of a torque, with interposition of a shiftable transmission (50; 150) comprising at least two gearing stages having different torque transfer ratios, is characterized in that by means of a first gearing stage of the shiftable transmission (50), an input shaft (48), coupled on the input side to the drive motor (42), of the shiftable transmission (50) is connectable in torque-transferring fashion directly to an output shaft (52), coupled on the output side to the working apparatus (22), of the shiftable transmission (50) so as to rotate together at the same rotation speed; and by means of a second gearing stage of the shiftable transmission (50), the input shaft (48) is connectable in torque-transferring fashion, with interposition of a transmission assemblage (64), to the output shaft (52) so as to rotate together at different rotation speeds.

Provided is a chain tensioner that can, with a simple structure, supply sufficient and necessary oil when restarted after a long time after the stop of oil supply, and control pressing force in accordance with operating conditions during the drive, thereby reducing vibration of the chain not only when restarted but also during the drive. In a chain tensioner 100 in which a plunger 120 inserted in a plunger bore of a tensioner body 110 is biased outward by biasing means 140 provided in an oil pressure chamber 101 to be extendable and contractible, an oil supply hole 114, an oil supply space 102, and a plunger hole 124 that together form a continuous oil supply passage is formed in such a shape that an oil amount changes in accordance with a position of the plunger 120.

A single-sprocket system for integration into a bicycle trainer, the system including a sprocket having teeth about a perimeter of the sprocket, a first planar side, and a second planar side, wherein the teeth of the sprocket are configured to engage a chain of a bicycle mounted to the bicycle trainer. The system further includes a first chain guide adjacent the first planar side of the sprocket, wherein the first chain guide is configured to re-engage the teeth of the sprocket with the chain when the chain has become disengaged from the teeth of the sprocket towards the first planar side, and a second chain guide adjacent the second planar side of the sprocket, wherein the second chain guide is configured to re-engage the teeth of the sprocket with the chain when the chain has become disengaged from the teeth of the sprocket towards the second planar side.

A single-sprocket system for integration into a bicycle trainer, the system including a sprocket having teeth about a perimeter of the sprocket, a first planar side, and a second planar side, wherein the teeth of the sprocket are configured to engage a chain of a bicycle mounted to the bicycle trainer. The system further includes a first chain guide adjacent the first planar side of the sprocket, wherein the first chain guide is configured to re-engage the teeth of the sprocket with the chain when the chain has become disengaged from the teeth of the sprocket towards the first planar side, and a second chain guide adjacent the second planar side of the sprocket, wherein the second chain guide is configured to re-engage the teeth of the sprocket with the chain when the chain has become disengaged from the teeth of the sprocket towards the second planar side.