Dwell cam

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A dwell cam is an intermittent motion mechanism that alternates forward and return motion with holding position.

Dwell cams are often used in pairs in sewing machines to operate the four motion feed dog, with one cam moving the dog up and down, and the other cam moving the dog fowards and backwards. The cams in this application are usually phased 90 degrees apart allowing a pause in the up/down movement of the dog while it is being moved forwards/backwards. A seperate adjustable sliding block or link is used to control the amount of forwards/backards movement of the dog.