Synchronous belt drive tensioning assembly

Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Pulley shifter

Reexamination Certificate

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C474S118000, C474S133000, C056S011600

Reexamination Certificate




1. Field of the Invention
The present invention relates to synchronous drives and more particularly to assemblies for tensioning a drive belt in a synchronous drive. A preferred embodiment of the present invention relates to a synchronous belt drive tensioning assembly for use on a rotary mower deck.
2. Description of Related Art
Vehicles such as lawn and garden tractors are often adapted to carry and operate 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.
Synchronous, or timed, drives are known which allow a plurality of blades to overlap in cutting area without interfering with each other. Synchronous drives have been implemented on a multiple blade mower deck as a secondary drive system which operates in conjunction with the primary drive to maintain proper blade orientation to prevent interference. A typical synchronous secondary drive system includes a toothed belt or chain, a mating toothed sprocket on each of the mower spindles and at least one tensioning idler which is commonly spring-biased to provide tension on the belt.
Problems commonly associated with conventional synchronous drives include: slipping or other undesired movement of tensioning idler, bending of idler support brackets upon movement of the tensioning idler, inability to obtain a desired tension in the toothed belt directly and predictably, and the loss of proper orientation (timing) of the sprockets/spindles/blades due to movement (ratcheting) of the toothed belt relative to the mating toothed sprockets.
The present invention provides a tensioning assembly for a synchronous belt drive on a mower deck. A plurality of idlers are mounted for rotation on a bracket. One end of the bracket engages an abutment surface mounted on the deck which restricts its movement, whereas a second end of the bracket is acted upon by a tensioning member which acts in substantially the same direction as the abutment surface. The bracket includes an elongated slot disposed between one of the idlers and the abutment surface, and a member fixed to the deck and engageable with the slot for confining movement of the bracket.
The preferred embodiment of the present design provides a synchronous drive which provides rigid and symmetrical support to idler sprockets before and after the tensioning process, a predictable and simple method for tensioning the drive belt, and a high degree of belt wrap to reduce (left) spindle-belt ratcheting, adjustable belt guides to eliminate (right) spindle-belt ratcheting, individual support plates for the spindles and secondary drive components, and formed features extending radially outward from the spindle pocket allowing hardware mounting of the support plates.

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