Source: {"pile_set_name": "USPTO Backgrounds"}

The present invention relates generally to a tandem axis vehicle and, more particularly, to a forward carrier assembly for a tandem axle vehicle.
It is ordinarily desirable that a vehicle have at least one reverse gear in addition to one or more forward gears. Typically, this is accomplished by providing a transmission including one or more countershafts with a plurality of countershaft gears thereon, the countershafts usually being driven by a geared connection with an input shaft driven by an engine. The gears on the countershaft mesh with gears mounted on, for example, an output shaft. At any given time, one of the gears on the output shaft drives is drivingly coupled to the output shaft, such as by a gear shift, to drive the output shaft. For the reverse gear, an idler gear is disposed between the countershaft gear and the output shaft gear so that rotation of the output shaft when the reverse gear is engaged is in the opposite direction from rotation of the output shaft when any of the forward gears is engaged, without having to alter the direction of rotation of the input shaft or the countershaft. Providing additional reverse gears adds complexity to the transmission.
It is desirable to provide a vehicle and powertrain that does not require a transmission with a separate reverse gear. It is also desirable to provide a vehicle and powertrain that permit provision of a substantial number of reverse gears without substantial additional transmission complexity.
According to an aspect of the present invention, a tandem axle vehicle comprises a powertrain, the powertrain comprising an input shaft, a forward drive axle assembly comprising a forward carrier assembly including a forward differential, a rear drive axle assembly coupled to the forward drive axle assembly via a connecting driveshaft and comprising a rear carrier assembly including a rear differential, the forward carrier assembly comprising an inter-axle differential (IAD), the IAD comprising an IAD housing, a differential spider comprising a plurality of legs attached to the IAD housing and a plurality of spider gears mounted on the legs, a first side gear engaged with the spider gears on a first side of the spider and arranged to drive a shaft for driving the driveshaft, and a second side gear engaged with the spider gears on a second side of the spider and arranged to drive the forward differential, and a clutch movable between an unlocked position, the clutch rotationally coupling the input shaft and the IAD housing when in the unlocked position, and a reverse position, the input shaft being rotationally decoupled from the IAD housing when the clutch is in the reverse position.
According to another aspect of the present invention, a forward carrier assembly for a tandem axle vehicle comprises an inter-axle differential (IAD), the IAD comprising an IAD housing having an internal spline, a differential spider comprising a plurality of legs attached to the IAD housing and a plurality of spider gears mounted on the legs, a first side gear engaged with the spider gears on a first side of the spider, the first side gear having an internal spline, a second side gear engaged with the spider gears on a second side of the spider, and a collar having one more external splines, the collar being movable between a first position in which the one or more external splines engage with the internal spline of the IAD housing and the internal spline of the first side gear, and a second position in which the one or more external splines is disengaged from the internal spline of the IAD housing and engaged with the internal spline of the first side gear.