Speed reducer box for driving a pump jack

Claim 1

A speed reducer box for driving a pump jack, the box attached to a drive motor or the like and reducing the speed therefrom to the pump jack, the box comprising: an elongated housing having a front portion, a center portion, and a rear portion, said housing further including a separate upper housing and a separate lower housing so that said upper housing can be removed for performing maintenance on the speed reducer box; an input shaft rotatably attached to the rear portion of said lower housing and said upper housing, said input shaft rotatably attached to the drive motor; an input shaft sprocket mounted on said input shaft; an idle shaft rotatably attached to the center portion of said lower housing and said upper housing; a first idle shaft sprocket and a second idle shaft sprocket mounted on said idle shaft; an output shaft rotatably attached to the front portion of said lower housing and said upper housing, said output shaft rotatably attached to the pump jack; an output shaft sprocket mounted on said output shaft; a first endless sprocket chain connecting said input shaft sprocket and said first idle shaft sprocket for driving said idle shaft; a second endless sprocket chain connecting said second idle shaft sprocket and said output shaft sprocket for driving said output shaft; and a chain tightener having a pair of chain tightening arms attached at one end to a pivot housing, said pivot housing attached to the bottom of said lower housing, the other end of said tightening arms attached to chain tightening sprockets, said chain tightening sprockets biased against said first sprocket chain and said second sprocket chain to tighten said chains when the speed reducer box is in operation.