Sewing machine with an upper feed mechanism
AssigneeG. M. Pfaff Aktiengesellschaft
InventorKurt Klundt
Life of this patent
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Abstract
Sewing machine with an upper feed mechanism is provided with a stroke-adjusting system in which the drive connection between the upper feed foot and the presser foot has a three-position control device for automatic adjustment of the height position of the upper feed system. This is preferably a hydraulic control device, whose hydraulic cylinder is subdivided by its adjusting piston into two chambers. A hydraulic difference measuring unit is provided wherein the two chambers 82a, 82b of the hydraulic cylinder 59 are connected via two antiparallel-connected pressure relief valves 71, 71'. Each pressure relief valve 71, 71' preferably consists of a spring-tensioned check valve R and a pressure-limiting valve D arranged downstream of it.
Claims3
A sewing machine, comprising:
- an upper feed system including an upper feed mechanism having an upper feed foot, a presser foot mechanism having a presser foot, and a lifting drive and a pushing drive for the upper feed foot, said lifting and pushing drive including a support which is adjustable in height via a drive connection connected to a housing of the sewing machine, said drive connection including hydraulic control means with a hydraulic cylinder and an adjusting piston, a force of reaction arising from a lifting force acting on said upper feed foot and on said presser foot during a sewing process being imparted via a linkage connection to said adjusting piston, said adjusting piston subdividing said hydraulic cylinder into a first chamber and a second chamber, and pressure relief means including a first pressure relief valve connecting said two chambers, acting in one direction and a second pressure relief valve connecting said two chambers, acting in an opposite direction.
Dependencies are inferred from the claim text.