Influence of Chain Pitch Increase on Bush-Sprocket Contact for Bush Chain Drives

One of the chain types used in machine construction is the bush chain. These types of chains can be with long or short links. In this paper it is proposed a case study, in which there is considered a standardized bush chain with short links, with known geometry of chain and sprocket. This is the starting point in the establishment of the contact between the sprocket and the chain during functioning. This will enable the precise determination of the static contact forces (value and direction). According to the literature, the pitch of a new chain should be bigger than its nominal value with up to 0.1%. In functioning, the pitch of the chain increases due to the wear of pin-bush joints and due to elastic deformation. This work proposes a comparative study of the most representative parameter, the contact angle (α) between the sprocket and the chain bush, for different sprocket sizes and different deviations of the chain pitch to the standard, which influence the contact forces and transmission behaviour. The evolution of the contact angle during gearing, in function of the sprocket’s number of teeth and the pitch difference (x), is highlighted with the help of the numerical simulations which permit drawing of some recommendations regarding the functionality of the transmission, minimization of vibrations or taking out the chain from functioning.