Abstract: A thread catcher of a cutting device in sewing machines is actuated by an air cylinder whose piston has two portions of unequal diameter. The small cylinder space accommodating the smaller-diameter piston portion is permanently pressurized while the larger cylinder space is alternately pressurized and vented. The larger cylinder space portion on its end closer to the smaller piston portion is permanently vented through a conduit. Both this conduit and the conduit for supplying the larger cylinder space include a throttle. The obtained effect is that the first step of motion of the thread catcher is quick and exact in duration, while the second step of motion is slower but performed with a greater force, so that thin threads are prevented from tearing prematurely and thick threads are cut reliably.

Abstract: A sewing machine includes a material engaging part such as a dog which is engageable with a material workpiece to selectively feed it in a forward and a reverse direction. In addition, the sewing machine includes the usual mechanism for raising and lowering the dog so as to complete an advancing or reverse movement of the material. The dog is driven preferably by a mechanism which includes an eccentric which may be adjusted so as to vary the length of horizontal feeding movement of the dog while the elevational changes of the dog remain constant by a separate feeding control mechanism. The magnitude of movement of the dog is controlled in accordance with a stitch length to be sewed by a stitch setting device which includes a movable contacting member which is connected to the eccentric mechanism and is movable between two end positions in order to adjust by a selected amount the movement of the eccentric in driving the dog by a selected amount.