Design of sprocket tooth profile for composite pitch block chain transmission

LU Jianfu; SHOU Qifeng; ZHANG Kefei; ZHOU Zhidi; SHOU Yulai; SUN Bing

doi:10.16578/j.issn.1004.2539.2025.07.018

Abstract：[Objective]The composite pitch block chain drive is widely used in the cold drawing machine and other similar equipment in the mechanical industry.The block chain has a special structure with different pitches between internal and external links,which is completely different from the ordinary roller chain and conveyor chain.At present,there is no corresponding industry standard and mechanical design manual for reference,so designers cannot directly use the existing calculation formula of chain sprocket pitch-circle to design the tooth profile.For this purpose,a design method of two circular arcs and one straight line tooth profile of the block chain sprocket was proposed for the sprocket tooth profile design of composite pitch block chain drive.[Methods]According to the meshing principle of chain drive,under the meshing state when the number of sprocket teeth was determined,the calculation formula of the pitch-circle diameter for the theoretical calculation was obtained by introducing the equivalent pitch based on the feature that the included angle between the inner and outer chain links was kept constant.[Results]The application results of the design example show that it is feasible to adopt the design of two circular arcs and one straight tooth profile for the sprocket of composite pitch block chain,and can provide design reference for engineering technicians.It should be pointed out that,because the block chain drive has the characteristics of non-conjugate meshing transmission,the sprocket tooth shape engaged with the block chain drive may not be completely the same,and the designers can also use the straight tooth shape or the involute tooth shape.