Patent ID: 8585015

Claim:
A forward and backward driving device comprising: a sprocket a chain guide; and engagement chain including a pair of individual engagement chains which are configured so as to engage and disengage with each other, each individual engagement chain comprising: a plurality of outer and inner link plates, each having a hook-shaped portion, which are connected together in a chain longitudinal direction by connecting pins, each of the plurality of outer and inner link plates further comprising an engagement tooth on a back surface of each of the plurality of outer and inner link plates for engaging with one of a pair of driving sprockets, wherein the pair of individual engagement chains are engaged and disengaged as the hook-shaped like portions of each individual engagement chain engage with each other when driven by the pair of driving sprockets which engages with the engagement tooth of the back-surface of each of the outer and inner link plates, causing the pair of individual engagement chains to engage and disengage with each other, respectively, wherein the outer link plates are positioned in outermost sides in a row in the chain width direction and comprise guide plates and intermediate plates which are disposed between the guide plates, and wherein the inner link plates are disposed alternately with said guide plates and intermediate plates in the chain longitudinal and width directions, and wherein the connecting pin has guide portions that project out of said guide plate, the guide portions consisting of projecting portions formed on the connecting pins which engage with a guide groove of the chain guide when the pair of individual engagement chains are disengaged with each other.