Patent ID: 7178472

Claim:
A gearbox for transmission systems in devices for metering materials, comprising: a pair of shafts, including a drive-input shaft and a drive-output shaft, respectively, provided on the drive-output shaft at least one pair of coaxial freewheels, on each of which an end of a respective linkage carrying a movable fulcrum means is active, the opposite end of each linkage being driven with a reciprocating oscillatory motion about the fulcrum means by an eccentric device provided on the drive-input shaft in order to convert the reciprocating oscillatory motion into an intermittent rotary motion of each freewheel and to bring about a rotary motion of the drive-output shaft in a preselected direction of rotation, the drive-input shaft including at least one pair of cranks with eccentric pins, and each linkage including a respective connecting-rod element having a first end connected kinematically to the corresponding freewheel and a second, opposite end articulated on the respective pin of the drive-input shaft with a capability for rotary and translational movement relative to the pin, the movable fulcrum means including, for each connecting-rod element, a respective fulcrum pin, each fulcrum pin being movable, in adjustable manner, between the first end and second end of the connecting-rod element so as to define different lever arms between said ends and to adjust a transmission ratio between the drive-input shaft and the drive output-shaft of the gearbox, and each fulcrum pin has a first end restrained on a stationary structure of the gearbox and an opposite second end restrained on the corresponding connecting-rod element to constitute the center of the rotation of said connecting-rod element during the reciprocating oscillatory motion relative to the drive-input shaft, said first end of the fulcrum pin being guided slidably in a wall of a casing constituting a gearbox housing and the second end of said fulcrum pin being engaged rotatably and slidably in a seat formed in the corresponding connecting-rod element.