Driving pin wheel 1 has pin b and rotates about fixed axis A.• When driving pin wheel 1 rotates continuously, driven sprocket 2 rotates intermittently with dwells about fixed axis B. The average transmission ratio from wheel 1 to sprocket 2 is i₁₂=z₂/z₁ where z₁ is the number of pins on wheel 1 and z₂ is the number of teeth of sprocket 2. Pawl 3 turns about fixed axis C and prevents unintentional rotation of sprocket 2 during the dwells. Pawl 3 is raised to release sprocket 2 during its rotation periods by cam surface a-a of wheel 1 which actuates lug d of the pawl.
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