Harvesters – Motorized harvester – With selective control of drive means
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a drive structure useable with a lawn and garden tractor that carries and powers an implement such as a rotary mower. A preferred embodiment of the present invention relates to an assembly comprising a plurality of idler pulleys for a mower deck belt drive which are mounted on a singular pivotable bracket.
2. Description of Related Art
Vehicles such as lawn and garden tractors are often adapted to carry and operate an implements such as mower decks which require rotary drive input. To drive the blade or blades of a mower deck, a pulley and belt primary drive arrangement is commonly provided in which a pulley is coupled with a crankshaft on the vehicle's engine. A V-belt is entrained around the crankshaft pulley as well as a pulley which is operably coupled to the spindles of the mower implement. Often, the V-belt entrained around the crankshaft pulley is part of a primary drive system which is coupled to a secondary drive system by a double-pulley jacksheave arrangement which may, for example, utilize a spindle on the mower implement as a jackshaft connecting the two pulleys of the jacksheave.
Primary belt drives on mower decks require a tensioning mechanism to maintain adequate tension to overcome normal stretch and wear of the belt and absorb the impact of engaging the deck and impacts by the blade. Many conventional decks utilize one tight-side idler and one backside idler to accomplish this task. A spring is attached to the backside idler to take up slack and to maintain as constant a tension as possible. Due to space constraints, particularly with belly-mounted mower decks, it would be desirable to develop a tensioning assembly which would reduce the amount of idler movement necessary to maintain a desired belt tension. In addition, some conventional belt drives have high belt angles which decreases belt life.
SUMMARY OF THE INVENTION
The present invention provides a primary drive tensioning assembly which utilizes dual pivoting idlers, allowing the idlers to pivot about a single axis and while still permitting the tight side and backside idlers to rotate. The geometry of the system allows the forces on the tight side to counter the forces on the slack side. The idler system therefore has to travel fewer degrees of rotation to take up a desired amount of slack in the drive belt.
According to the present invention, the number of parts and space required to properly tension a primary drive belt is reduced. Every degree of rotation of the idler system nearly doubles the amount of belt takeup. The offset of forces between the previously fixed and backside idler allows a spring to provide a more uniform tension through its total required travel. In addition, the fewer degrees of rotation needed for this system allows the idlers to be placed further away from the drive sheave on the deck, reducing the belt angle from horizontal with respect to the various pulleys around which it is entrained.
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Sabre 1338GR/1538GR Lawn Tractors Owner's Manual, cover, foreword and pp. ENG22-ENG25, published 1999 in U.S.A.
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Holland Ronald Paul
Kuhn John Boyd
Thorman Christopher Scott
Deere & Company
Pezzuto Robert E.
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