Abstract: A drive transmission mechanism including a shaft including a reduced diameter portion at an outboard end, an engaging portion inboard of the reduced diameter portion, and an installation portion inboard of the engaging portion and having the same diameter as the engaging portion, a first bearing having an inner ring onto which the reduced diameter portion is fitted, a connecting member provided to the shaft and including a main body into which the installation portion is fitted and a fitting portion provided to the main body on a side in which the engaging portion is provided to accommodate the engaging portion, and a second bearing engaging the shaft to support the shaft at an inboard end of the shaft opposite the first bearing with the connecting member interposed between the first and second bearings.

Abstract: A belt driving device and associated method are provided. The driving device includes a plurality of rollers including a driving roller. A belt is configured to be tensioned by the plurality of rollers, and to be driven by the driving roller. An outside roller is configured to contact an outer surface of the belt and to be driven by a driving source. A detection portion is configured to detect a driving load of one of the driving roller and the outside roller. A controller is configured to drive the other one of the driving roller and the outside roller based on the driving load detected by the detection portion.

Abstract: A method of measuring and correcting the Young's Modulus inline to eliminate its impact on image length variation during print runtime. The method includes intentionally perturbing the nominal operating condition of the web printing system which is controlled by the double reflex printing controller. The perturbation creates misregistration in a control target printed image that is detectable by in-situ sensors, from which Young's Modulus is estimated. Specifically, the web tension before the print zone is set differently from the web tension in the print zone to create misregistration. The error is detected by the inline sensors, and it is used to calculate the actual Young's Modulus. The implementation of the method consists of measuring the Young's Modulus at various frequencies. The correct Young's Modulus in then incorporated into the double reflex printing algorithm.

Abstract: A reducer for an industrial motor including a housing assembly, an input shaft assembly, an output shaft assembly and a cogged belt. The housing assembly defines a cavity. The input shaft assembly includes a first sprocket. The input shaft assembly is coupled to the housing assembly and positioned within the housing. The input shaft is configured for coupling to a motor positioned outside of the cavity through the input opening. The output shaft assembly includes a second sprocket, and is coupled to the housing assembly while being positioned within the housing. The output shaft is configured for coupling to a mixer agitator assembly having an impeller positioned outside of the cavity through the output opening. The cogged belt couples the first sprocket to the second sprocket and being positioned within the cavity.

Abstract: A torque transmission chain and torque transmission device of which the strength of links is increased by devising lock points that regulate the maximum relative rotation angle between the links are provided. Lock points that contact with pins and interpieces to regulate the maximum relative rotation angles are provided at four portions, that is, a front surface of a link front pillar portion, a rear surface of a link rear pillar portion and a front surface and rear surface of a link intermediate pillar portion. Each of allowable maximum relative rotation angles regulated by the lock points of a link outline portion is set so as to be smaller than each of allowable maximum relative rotation angles regulated by the lock points of the link intermediate pillar portion.

Abstract: The invention is a combination drive and suspension system that includes an upper drive assembly and a lower drive assembly pivotally connected. The pivoting drive system provides improved ground clearance for a farm vehicle capable of carrying a large quantity of field application material.

Abstract: A system for an engine drive that engages a single timing band with a camshaft, a crankshaft and various accessory drives in such a configuration that the camshaft is rotated in a direction opposite that of the crankshaft, while ensuring a reflex wrap angle around each drive sprocket coupled to the camshaft, crankshaft and various accessory drives.

Abstract: A driving device includes a stretched member, and a first rotation member and a second rotation member that support the stretched member in a stretched manner. The first rotation member has a first rotation axis, and the second rotation member has a second rotation axis. The first rotation member includes a plurality of members arranged in an axial direction of the first rotation axis.

Abstract: A working unit includes a gear body disposed forwardly of a tubular member around which a wire is wound and having a rotational axis disposed substantially parallel to the tubular member, and a first gear and a second gear for transmitting rotation of a gear body to another gear body. The numbers of turns of wires, the size of a main shaft, and the size of a gear body, which are positioned forwardly of the tubular member, have no adverse effect on the manner in which a wire is wound around the tubular member. The wire can be wound around the tubular member over a wide region thereof for increasing the angular displacement of the gear body. The increased angular displacement of the gear body makes it possible to increase the angular displacement and rotational torque of the gear body.

Abstract: Chain return arrangement and sprocket and chain assembly employed therein with the bow flanks of the horizontal chain links (1) of the chain assembly (10) exhibiting a concave trough at least below an equatorial line (7) and the chain link pockets (52) of the sprocket (50) that receive the horizontal chain links at their tooth flanks (53) in the contact areas (55) to the chain links (1) having a convex crown shape to match the troughed bow flank. This significantly reduces the surface pressures between the two parts. (See FIG.

Abstract: An idler pulley is described for a front end accessory drive. The idler pulley includes plurality of angled spokes, such as angled ribs molded into the pulley to join an outer hub and an outermost belt interacting region. As the belt runs over the surface of the pulley, any defects on the belt running surface of the pulley due to shrinkage and fill are now angled, and angling of the defects reduces direct impact with the belt and therefore reduces the structureborne noise produced by operation of the belt and the pulley.

Abstract: In a friction drive belt (B), a belt body (10) made of a rubber composition is wrapped around pulleys to transmit power. A powder layer (16) is combined and integrated with a pulley contact-side surface of the belt body (10) located on a side that is to contact the pulleys, so that the powder layer (16) covers the pulley contact-side surface.

Abstract: In a belt continuously-variable transmission, a casing or a housing is formed with an air communicating hole extending through an upper part of the casing or the housing. The casing and the housing include inner walls defining an air breather chamber and communicating parts. The air breather chamber is defined in a region located above a joint between the casing and the housing and ranging from an upper side of the second shaft to an upper side of the first shaft and between the second shaft and the first shaft. The communicating parts are defined at a position in the upper side of the first shaft and at a position between the second shaft and the first shaft. The air breather chamber communicates with open air via the air communicating hole, and communicates with an inside part of a casing assembly via each of the communicating parts.

Abstract: One embodiment may include an automotive timing chain system component (10, 12) such as a tensioner arm (10) or a chain guide (12) that, during use, bears directly or indirectly against a chain (22) of an automotive timing chain system (14). The component (10, 12) may have an elongated body (16, 116) made into a generally hollow shape by a hydroforming process. The body may have a first open free end (26, 126) and a second open free end (28, 128).

Abstract: Drive device for a wind mill comprising a large pulley (21) disposed on a main shaft (22) and at least one belt (27) or chain adapted to transfer rotation from the pulley (21) to a generator (30, 31). The pulley (21) is rotationally coupled to at least two secondary shafts (23, 24), which are disposed parallel to the main shaft (22). One or more belts (27), which transfer the rotation, extend over the pulley (21) and the secondary shafts (23, 24). The secondary shafts (23, 24) are in turn rotationally coupled to at least one, preferably two, electric generators (30, 31).

Abstract: Starter-alternator assembly including a poly-V belt comprising a body made of elastomeric material, a plurality of filiform resistant inserts longitudinally embedded in the body, and a coupling portion integrally connected to the body and comprising a plurality of V-shaped ribs set alongside one another and alternating with V-shaped grooves. The belt has a dynamic modulus, with a tensile force pre-set at 600 N at a frequency 15 Hz, that after 10 000 cycles is higher than 110 000 N/rib/branch, and is advantageously made with resistant inserts obtained from at least one first fibre material and one second fibre material.

Abstract: A drive mechanism for a vehicle seat track assembly includes a housing and a motor having an output shaft. An output speed reducing mechanism is coupled to the output shaft. The motor and the output speed reducing mechanism are mounted to the housing. A toothed drive pulley is rotatably mounted to the housing and coupled to the output speed reducing mechanism. A first toothed pulley is rotatably mounted at a first end of the housing. A second toothed pulley is rotatably mounted at a second end of the housing. A continuous toothed belt is rotated by the toothed drive pulley and causes rotation of the first and second toothed pulleys.

Abstract: The present invention relates to a transmission system for a two-wheeled cycle of the type comprising at least one sprocket (1) attached to the rear wheel hub (2) and rotatably mounted around an axis (x); at least one chainring (3) secured to the frame of the cycle and rotatably mounted around a second axis (y) parallel to the axis (x); a crankset composed of two pedals (7, 8) rotatable around a third axis (z) parallel to the axes (x, y) and located inside the rear wheel; and a main transmission element (6) drivable by actuating the crankset and passing through said sprocket (1) and also passing through, or controlled by, said chainring (3).

Abstract: A one-way or selectable clutch with multiple circumferential rows of ratchet elements is disclosed. The clutch may include two or more rows of ratchet elements extending between two or more races. The device may be either a one-way clutch or a selectable mechanical clutch, and afford the benefits of reduced backlash and multiple modes of operation. Those modes may include free-wheel/overrun in both clockwise and counterclockwise directions, lock/transmit torque in both directions, lock in clockwise and overrun in counterclockwise directions, and lock in counterclockwise and overrun in clockwise directions.

Abstract: A drive mechanism of the present invention includes: a housing part composed of a first resin cover and a second resin cover; a first sheet metal member housed in the housing part; a first rotation transmission wheel group disposed on the first sheet metal member on a side directed to the first resin cover; a second rotation transmission wheel group disposed on the first sheet metal member on a side directed to the second resin cover; a positioning part rotatably supporting a first rotation transmission wheel of the first rotation transmission wheel group; and a pin member positioned by inserting into the positioning part via the first resin cover.

Abstract: An apparatus for driving an actuating mechanism, of an apparatus for opening and/or closing a furniture part accommodated in a movable manner on a basic furniture part, including a drive unit for driving the actuating mechanism via a transmission arrangement with a plurality of transmission members. The actuating mechanism is arranged on one of the furniture parts and can be brought temporarily into contact with the other furniture part during opening and/or closing. The contact between the actuating mechanism and the other furniture part is broken during an opening operation. The transmission arrangement includes a traction-mechanism device.

Abstract: A method for reducing NVH in a vehicle having the steps of providing at least one repeating event, replicating at least one component, and delaying at least one equivalent part. The repeating event is a complete cycle, such that the repeating event ends when the cycle begins to repeat itself. The component is replicated at least one time so that at least one equivalent part is formed. The equivalent part is delayed with respect to the component by angularly positioning the equivalent part with respect to the component in a predetermined way, such that at least one harmonic in the NVH-spectra is reduced during the component's repeating event and the equivalent part's repeating event in operation.

Abstract: A reel cutting unit of a reel mower is provided with a belt and pulley drive system for rotating the reel of the cutting unit at variable speeds when the ground speed of the reel cutting unit is substantially constant to provide different clips. The drive system has three pulleys of different diameter in engagement with the belt in drive, driven and idler positions. The pulleys can be interchangeably used in any of the positions by moving the pulleys around into the different positions in six different possible arrangements. The pulleys are selectively placed in one arrangement at a time to select the clip provided by that arrangement. A chain and sprocket drive system with different diameter sprockets may be used in place of the belt and pulley drive system. The belt and pulley drive system may comprise toothed pulleys and toothed timing belt.

Abstract: An inverted tooth chain and sprocket drive system in which the initial contact distance ICD, the meshing impact angle Sigma (?), the link plate entrance angle Beta (?), and other aspects of the meshing geometry are controlled and optimized to reduce noise and vibration by using a particular chain link plate form and, in preferred cases, by modifying the sprocket tooth pressure angle. The system can include first and second sprockets for which the pressure angle can be controlled to ensure that the desired values for the initial contact distance ICD, the meshing impact angle Sigma (?), and the link plate entrance angle Beta (?) are equal for both sprockets even though the sprockets have different tooth counts. For a chain pitch P in the range of 6.35 mm to 7.7 mm, the initial contact distance ICD is controlled such that 0.49 P?ICD?0.53 P, the meshing impact angle Sigma (?) is controlled such that ??34°, and the link plate entrance angle Beta (?) is controlled such that ??9°.

Abstract: The present invention concerns a power transmission for a rotary type of walk-behind lawn mower. The transmission comprises a first transmission part (7A) arranged to be mounted in a lawn mower housing (1) and comprising a transmission pulley (6) , which in turn is arranged to be connected to an engine pulley (4) of a lawn mower via a drive belt (5) . A second part (7B) of the transmission is arranged to be connected to a wheel axle (9) of the lawn mower, wherein the first transmission part (7A) is connected to the second transmission part (7B) via an articulated joint (11) such that the second transmission part (7B) and the wheel axle (9) are arranged to be pivotally mounted on said lawn mower housing (1) . Thereby pivoting will adjust the height of said lawn mower housing (1) in relation to a ground plane. The invention also concerns a walk-behind lawn mower comprising such a transmission.

Abstract: In a belt transmission system A, a drive pulley 1 and at least one driven pulley 2-4 are flat pulleys, and power transmission between the pulleys is performed through a substantially flat transmission surface b1 of the power transmission belt B. This can improve transmission efficiency and durability of the power transmission belt to be comparable to those of a flat belt, while significantly reducing the cost of the system. A plurality of protrusions 82a extending in the longitudinal direction of the belt are provided on an outer surface of the belt, and are allowed to engage with circumferential grooves 5a of a restriction pulley 5, 6, thereby restricting movement of the power transmission belt in the lateral direction of the belt. This can keep the belt running stably even when rainwater etc. is adhered to the belt or the pulley.

Abstract: The invention is a combination drive and suspension system that includes an upper drive assembly and a lower drive assembly pivotally connected. The pivoting drive system provides improved ground clearance for a farm vehicle capable of carrying a large quantity of field application material.

Abstract: A continuously-variable transmission includes two transmission members each having coupling elements engageable to couple the transmission members for movement together. At least one of the transmission members is a rotary member rotatable about a rotary axis; and at least one of the groups of coupling elements is radially displaceable towards and away from the rotary axis to change the conversion ratio of the transmission. The coupling elements of one group on one transmission member are of a fixed configuration defining projections alternating with depressions each of a fixed configuration formed on a surface of the transmission member between opposite side faces and having the same pitch for every cross section of the surface perpendicular to the mentioned rotary axis.

Abstract: A chain gear (1) for gearing an engine torque comprises three gearing stages, wherein the first gearing stage is formed by a first gear rim (6) and a fourth gear rim (9), the second gearing stage is formed by a second gear rim (7) and a fifth (10) gear rim, and the third gearing stage is formed by a third gear rim (8) and a sixth gear rim (11). The first gear rim (6), the second gear rim (7) and the third gear rim (8) are disposed on a first shaft (3), and the fourth gear rim (9), the fifth gear rim (10) and the sixth gear rim (11) are disposed on a second shaft (4). A transmission chain (27, 28, 29) is provided in each gearing stage for transmitting the torque.

Abstract: A flywheel energy storage system for a vehicle, comprising a first shaft, a second shaft operatively coupled to the first shaft and to the vehicle's drivetrain, a flywheel operatively coupled to the first shaft, and a motor operatively coupled to the first shaft and electrically coupled to a power source, the motor being adapted to receive energy from the vehicle's electrical system and the flywheel energy storage system being adapted to transfer energy to the vehicle's drive system.

Abstract: A winch driven by a rotatable cassette. The cassette can be rotated into multiple different positions. Each of the addition positions produces a different speed up the output for a cable.

Abstract: A friction drive belt (B) includes a pulley contacting portion (13) which is made of a rubber composition of an ethylene-?-olefin elastomer as raw rubber in which carbon black having an iodine adsorption number of 40 mg/g or lower, and 3-10 parts by mass of short aramid fiber (14) relative to 100 parts by mass of the raw rubber are blended.

Abstract: A hollow yoke is inserted into a bore section of a frame. The yoke is connected to a slider via a slit in the frame. A timing belt is inserted into a belt hole of the yoke. Further, a pair of guide members are provided on both side surfaces of the yoke, which engage with guide grooves of the frame. The yoke is displaced along the guide grooves by the timing belt, under a driving action of a driving section. Accordingly, the slider is displaced in the axial direction along the frame.

Abstract: A hybrid motorcycle includes a body frame, a front wheel, and a hybrid driving source. The hybrid driving source is mounted on the body frame between a head pipe and a swing arm pivot. The hybrid driving source includes an engine and a motor. The engine has a crankshaft whose axial direction is substantially parallel to a vehicle longitudinal direction. The motor is provided at a front shaft end adjacent to the front wheel.

Abstract: A dual-ratchet wheel transmission apparatus includes: a drive wheel set, having a first drive wheel and a second drive wheel coaxially integrated with a drive shaft; a driven wheel set, being coaxially set with a driven shaft in which the driven shaft is connected to an output for transmission, the driven wheel set including: a first driven wheel being centrally integrated with a unidirectional ratchet wheel, in which the first driven wheel engages with the first drive wheel for transmission, a second driven wheel being centrally integrated with another unidirectional ratchet wheel, in which the second driven wheel is connected to the second drive wheel via a transmission element. By the aforementioned configuration, whether the drive wheel set rotates forward or backward, the transmission set rotates in only one direction.

Abstract: Belt drive assembly for driving accessory parts of an internal combustion engine comprising a reversible electric machine, comprising a belt with a plurality of longitudinal ribs alternating with grooves and with a plurality of cavities spaced at equal distances from each other longitudinally and obtained transversely with respect to the ribs in such a way as to interrupt them; the pulley comprises a plurality of ribs suited to engage the grooves of the belt and a plurality of teeth transverse with respect to the ribs, spaced at equal distances from each other on the circumference and suited to engage the respective cavities of the belt. The cavities of the belt have a depth at the most equal to the height of the ribs of the belt itself, and the ribs of the pulley have a radial height larger than the teeth, so as to cooperate with the belt continuously along the whole winding arc.

Abstract: A dual mode continuously variable transmission (DMCVT), which can maintain advantages of a reducer operated in low-speed running mode and makes the diameter ratio of variable speed pulleys in high-speed transmission mode act as a reducer, thus improving durability and energy efficiency of the CVT. The DMCVT has a drive variable speed pulley mounted on an input shaft connected to an engine, a driven variable speed pulley mounted on an output shaft and receiving a rotatory force from the drive pulley through a belt, a drive shaft, first and second mode output gears mounted on the output shaft, first and second mode drive gears mounted on the drive shaft and gearing into the first and second mode output gears, respectively, and a synchro selector selectively engaging with a gear of one of the drive and driven shafts.

Abstract: A self aligning belt drive system comprises a belt drive having a plurality of longitudinally spaced inner lobes each having an alignment groove. The system further comprises at least one pulley comprising a frame configured to rotate about a rotation axis and having a circular outer rim. A plurality of circumferential teeth extend radially and axially of the rim with each tooth being configured to be received between adjacent inner lugs of the drive belt. An alignment flange extends radially between circumferential teeth. The alignment flange is configured to be received in the alignment groove and the alignment flange extends no further radially from the rotational axis than the circumferential teeth. The circumferential teeth, the alignment flange and the alignment groove are configured so that with the alignment flange received in the alignment groove, the drive belt rides on the circumferential teeth.

Abstract: A scissor gear assembly may include first and second gears, a friction plate, and a biasing member. The first gear may have a first number (n) of gear teeth extending from a perimeter thereof. The second gear may have a second number (m) of gear teeth extending from a perimeter thereof and may be concentrically mounted relative to the first gear and rotatable relative to the first gear. The second number (m) of gear teeth may be greater than the first number (n) of gear teeth. The friction plate may be rotationally fixed relative to the first gear. The biasing member may have a first end axially fixed relative to the first gear and a second end axially biasing the second gear and the friction plate into engagement with one another.

Abstract: A driving force transmitting apparatus includes a driving source; a drive pulley rotatable by a driving force supplied from the driving source; a follower pulley rotatable with a member to be rotated; a belt member extending around a cylindrical surface of the driving pulley and a cylindrical surface of the follower pulley; and an intermediate transmission member disposed between the driving pulley and the follower pulley, the intermediate transmission member having a rigidity higher than that of the belt member and contacted to the pulleys or opposed to the pulleys with the belt member therebetween.

Abstract: A power transmission system for a people mover includes a transmission housing, a first motor having a motor shaft, an output gear located inside the transmission housing, and a plurality of gears located inside the transmission housing. The plurality of gears includes an output gear located inside the transmission housing, and first and second reduction gears cooperating to drive the output gear. At least one of the first and second reduction gears has an input/output shaft extending outside the transmission housing. The system also includes an external reduction stage located outside the transmission housing and driven by the first motor shaft to rotate the input/output shaft.

Abstract: A plug-in hybrid vehicle drive system, including an internal combustion engine for driving one or more wheels of a vehicle, at least one on-wheel electrically powered motor, the motor coupled to a speed reduction mechanism, the speed reduction mechanism coupled to a vehicle wheel for driving at least one wheel of the vehicle, a battery located in the vehicle and connected to the at least one on-wheel motor for supplying power to the on-wheel motor, a battery charger including an AC/DC power converter, and an AC outlet connector in communication with the battery charger for receiving power from an external source.

Abstract: With a view to suppressing fretting in a power transmission chain, when a chain straight-line area is seen from a chain widthwise direction W, a flat portion 18 of a first pin 3 of the chain extends in an inclination direction D. A point of intersection P0 is formed by an imaginary line L1 which passes through a center position of an overall height h of the first pin 3 along the inclination direction D intersecting the flat portion. A point of intersection P2 is formed by an imaginary line L2 which passes through a contact portion A0 and which extends in a chain advancing direction X intersecting the flat portion 18 between the point of intersection P0 and one end P1 of the flat portion. When assuming that a distance between the point of intersection P0 and the point of intersection P2 is referred to as h1 and a distance between the point of intersection P2 and the one end P1 of the flat portion 18 is referred to as h2, 0.1·h1?h2.

Abstract: A method for reducing variations in tension in a drive belt 7 of an accessory belt drive system is disclosed in which an electrical load imposed upon the drive belt 7 by an electrical generator 8 is modulated based upon fluctuations in the speed at which the drive belt 7 is driven. By reducing the electrical load when the drive belt 7 is being accelerated and increasing the electrical load when the drive belt is decelerating the difference between the maximum tension and the minimum tension in the drive belt 7 is reduced.

Abstract: A synchronous belt drive system comprising an obround sprocket (10) having a toothed surface and at least one linear portion (16) disposed between two arcuate portions (14,15), the arcuate portions having a constant radius (R1, R2), the linear portion having a predetermined length, a second sprocket (300) having a toothed surface, the second sprocket engaged to the obround sprocket by an endless toothed member (200), the second sprocket connected to a rotary load, the rotary load having cyclic torque fluctuations, and a radius (R1) of the obround sprocket (10) oriented at a belt entry point (201) which coincides with a maximum amplitude of a cyclic torque fluctuation such that a span length (SL) of the endless toothed member is made to vary in a manner that substantially cancels the cyclic torque fluctuations.

Abstract: A thermoplastic endless belt (100) has a smooth outer surface substantially free of discontinuities and an inner surface with a plurality of teeth (106) at a given belt pitch. The teeth are adapted to engage a pulley (102) with circumferentially spaced sheaves (104) at a pulley pitch greater than the belt pitch. The belt is slightly stretchable so that the pulley can drive the endless belt when engaging the teeth within a range of load on the belt. Means (132, 136, 138) are provided to minimize friction between the belt and the drive pulley. Also, a position limiter (200) ensures that the driven tooth stays engaged optimally with the drive sheave.

Abstract: A power transmission mechanism comprising: a flexible power transmission element; a pair of a drive pulley and a driven pulley on which the flexible power transmission element is wound, each the pulley having a pin-embedding hole formed to extend from the outer circumferential thereof toward the center thereof, and a slit elongated in the circumferential direction of the pulley to extend to opposite sides of the embedding hole and communicating with the embedding hole; and a pair of columnar or tapered anchor pins each having a path hole penetrating the anchor pin across the lengthwise direction thereof to receive the flexible power transmission element inserted therein, wherein each the anchor pin receiving the flexible power transmission element in the path hole thereof is embedded in the embedding hole of the associated pulley under pressure, and the flexible power transmission element is thereby held on the pulley.

Abstract: In chain and sprocket systems with at least two resonance modes, two or more tension reducing sprockets are oriented to cancel each other at a first resonance mode and have no effect to increase tensions at such first resonance mode. The tension reduction sprockets, however, are oriented with each other so that tensions will be reduced at a second resonance mode. Hence, two or more tension reducing sprockets are used to reduce tensions at a second resonance mode from sources outside the chain and sprocket system while minimizing tension increases at first resonance mode.

Abstract: There are provided a power transmission chain which can improve not only noise level but also durability by eliminating unfavorable combinations from a random arrangement of combinations of pitch lengths and pin shapes by paying attention to maximum bending angle and bending angle minimum value and a power transmission system using the same power transmission chain. With respect to pitch length, links include two types of a link L1 which has a small pitch length and a link L2 which has a large pitch length. With respect to pin shape, pins include two types; a pin P1 of which a curvature of a rolling contact surface is large and a pin P2 of which the curvature of the rolling contact surface is small.

Abstract: A drive mechanism comprising a first sprocket encircled by a tensioned chain and an orbit sprocket arranged to orbit the first sprocket in response to a resynchronisation signal. The orbit sprocket is arranged to displace the tensioned chain relative to the first sprocket. The first sprocket is rotatable and is coupled to an output drive sprocket by the tensioned chain such that the first and output drive sprockets are rotatable in synchronicity, whereby the orbit of the orbit sprocket alters the relative angular orientation of the first and output drive sprockets.