Splitter gearbox vent tube
Vent tube for a splitter gearbox mounted on the rear axle assembly of a four-wheel drive tractor. The vent tube extends into the rear axle assembly, while in fluid flow communication with the lubricating oil in the splitter gearbox, and either breaks a vacuum at a balance hole or permits oil transfer from the splitter gearbox, depending upon which direction the output gears are being driven. The output gears turn at high rpm and cause churning of the oil. The vent tube assembly relieves this condition and thereby significantly reduces parasitic power losses.
Therein is discussed the desirability of integrating all the drives for the input driven components of an articulated four wheel drive tractor into a single gearbox affixed to the rear axle housing of the tractor. The instant invention is an improvement to a splitter gearbox as generally disclosed in the patent.
Accordingly, one object of the present invention is to provide a vent tube that significantly reduces parasitic losses due to the churning of oil by the output gears of a splitter gearbox.
Another object of the present invention is to provide a novel means for reducing parasitic losses in a splitter gearbox.
It is yet another object of this invention to provide an improved splitter gearbox for a four wheel drive, hydrostatically driven tractor which is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use.
It is a still further object of the instant invention to provide a vent tube for a splitter gearbox mounted on the rear axle assembly of a four-wheel drive tractor. The vent tube extends into the rear axle assembly, while in fluid flow communication with the lubricating oil in the splitter gearbox, and either breaks a vacuum at a balance hole or permits oil transfer from the splitter gearbox, depending upon which direction the output gears are being driven. The output gears turn at high rpm and cause churning of the oil. The vent tube assembly relieves this condition and thereby significantly reduces parasitic power losses.
As a matter of clarification, it should be understood that the output gears otate at generally high speeds during vehicle transport/roading, in the range of 5,000 rpm. When these gears are rotated in one direction, as they would be when tractor is moving rearward, they create a suction, drawing oil into the splitter gearbox from the rear axle that is the hydraulic sump of the vehicle. Too much oil in the splitter gearbox creates churning and constant power losses (parasitic losses). When gears rotate in the opposite direction, i.e., the tractor is moving forward, they create a pumping action and oil is pumped out of the splitter gearbox. Thus, parasitic losses, similar to those described above, are created.
Balance hole is present between the splitter gearbox the rear axle housing to allow oil to drain from gearbox, which is pressure lubed, to the rear axle housing. Hole is located at a level where the output gears and mesh. When the tractor is driven forward, the output gears rotate in such a manner as to pump oil from the gearbox into the rear axle through the balance hole. As oil is drawn into the gearbox, the level increases, covering the gears and creating high parasitic losses due to churning. The vent tube assembly is mounted such that one end of tube covers the balance hole, one end connects to a check valve at the same level as the balance hole, with the free flow direction from the gearbox to the rear axle housing , and leg extends above the oil level L of the rear axle.
When the tractor is driven in reverse, the vent tube assembly breaks the vacuum at the balance hole created by the output gears of the splitter gearbox, thereby not allowing oil to be drawn into the splitter gearbox and keeping the parasitic churning losses low. When the tractor is driven in this direction up an incline, the check valve closes off due to the oil level rising in the splitter gearbox 30/rear axle housing junction and the vent tube then breaks the vacuum created by the output gears of the splitter gearbox as above.
When the tractor is driven forward, the check valve allows the oil that is being pumped by the splitter gearbox output gears through the balance hole, to be drained into the rear axle, keeping the parasitic churning losses low. An additional balance hole may be added as needed to help with the balancing issue.
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