sewing machine with a device for generating a druckmittelbetätigbaren adjustment, a stoffdrücker penetrating andrückkraft

摘要

A device in a sewing machine for applying a variable downward force to a presser bar. A guide lever engages the presser bar and in turn is urged downward by the force of a spring. The bottom of the spring is held fixed to a lock sleeve on the guide lever. The top of the spring is fixed to a sleeve on a shaft which is disposed vertically inside the spring. The shaft passes freely out the bottom of the spring and through the guide lever without engaging either of these. The shaft and thereby the top of the spring are urged downward by a controllable pneumatic device in order to set the compression of the spring and thereby the downward force applied to the pressure bar by the guide lever. The pneumatic device preferably includes a pair of separately controlled pneumatic pistions arranged in series for moving the shaft to at least two predetermined positions.