Controllable tensioning devices for strand material

Claim 2

In a sewing machine including a stitching mechanism paying out an upper strand from a supply spool and a lower strand from a bobbin of a lower strand dispensing mechanism, wherein the improvement comprises: an upper strand tensioning device positioned on the sewing machine for frictional engagement with the upper strand between the supply spool and the stitching mechanism; and a lower strand tensioning device positioned adjacent to the lower strand dispensing mechanism of the sewing machine, said lower strand tensioning device adapted to receive a variable electrical signal and exert a drag on the lower strand dispensing mechanism to control the dispensing rate thereof, the amount of drag exerted by said lower strand tensioning device varying in accordance with the electrical signal received; wheRein said lower strand tensioning device includes, a housing, a plunger reciprocally mounted within said housing, a brake pin attached to and reciprocally movable with said plunger, said brake pin having one end extending from said housing for contacting the bobbin of the lower strand dispensing mechanism and exerting a frictional drag thereon when said plunger moves said brake pin to an extended position, biasing means positioned within said housing for biasing said plunger and said brake pin in a retracted position, and signal responsive means mounted in said housing and responsive to the electrical signal for moving said plunger and said brake pin to the extended position, the extending force exerted by said moving means varying in response to the electrical signal applied thereto.

Claim 3

A command responsive tensioning device according to claim 1 wherein said signal responsive means comprises an electromagnet and said plunger forms the core of said electromagnet, and the variable electrical signal is in the form of a variable voltage amplitude, said electromagnet applying a force to said rod proportional to the voltage amplitude applied thereto.

Claim 4

Command responsive tensioning devices as claimed in claim 1 further including mounting means connecting said lower strand tensioning device to the sewing machine, the mounting means adapted to permit pivotal movement of said lower strand tensioning device between an operational position and an access position to allow servicing thereof, said mounting means comprising: a bracket attached to the sewing machine; a trunion extending from said bracket; at least one arm extending from said lower strand tensioning device, said arm adapted for pivotable movement about said trunion; a flat formed on said arm; and a detent spring attached on one end thereof to said bracket, the other end of said detent spring positioned to engage said flat to accurately position said lower strand tensioning device in the operational position and to yield when said lower strand tensioning device is moved to the access position.

Claim 5

In a sewing machine including a stitching mechanism paying out an upper strand from a supply spool and a lower strand from a lower strand dispensing mechanism, wherein the improvement comprises: a strand engaging mechanism rotatably mounted to the sewing machine and positioned for engaging the upper strand between the supply spool and the stitching mechanism; an electromagnetic clutch mounted to the sewing machine having a driving and a driven end with the driving end fastened to prevent rotation thereof and the driven end coupled to said strand engaging mechanism, said electromagnetic clutch responsive to a first variable voltage signal for varying the retardation of rotation of the driven end to vary the tension applied to the strand and thus control the stitches formed by the sewing machine; a housing mounted adjacent to the lower strand dispensing mechanism; a plunger reciprocally mounted within said housing; a brake pin attached to and reciprocally movable with said plunger, said brake pin having one end extending from said housing for contacting a bobbin of the lower strand dispensing mechanism and exerting a frictional drag thereon when said plunger moves said brake pin to an extended position; biasing means positioned within said housing for biasing said plunger and said brake pin in a retracted position; and signal responsive means mounted in said housing and responsive to a second variable electrical signal for moving said plunger and said brake pin to the extended position, the extending force exerted by said moving means varying in response to the electrical signal applied thereto.

Claim 6

In a sewing machine including a stitching mechanism paying out an upper strand from a supply spool and a lower strand from a lower strand dispensing mechanism, wherein the improvement comprises: a strand engaging mechanism rotatably mounted to the sewing machine and positioned for engaging the upper strand between the supply spool and the stitching mechanism; an electromagnetic clutch mounted to the sewing machine having a driving and a driven end with the driving end fastened to prevent rotation thereof and the driven end coupled to said strand engaging mechanism, said electromagnetic clutch responsive to a first variable voltage signal for varying the retardation of rotation of the driven end to vary the tension applied to the strand and thus control the stitches formed by the sewing machine; a housing mounted adjacent to the lower strand dispensing mechanism; a plunger reciprocally mounted within said housing; a brake pin attached to and reciprocally movable with said plunger, said brake pin having one end extending from said housing for contacting a bobbin of the lower strand dispensing mechanism and exerting a frictional drag thereon when said plunger moves said brake pin to an extended position; biasing means positioned within said housing for biasing said plunger and said brake pin in a retracted position; and signal responsive means mounted in said housing and responsive to a second variable electrical signal for moving said plunger and said brake pin to the extended position, the extending force exerted by said moving means varying in response to the electrical signal applied thereto.

Claim 7

A command responsive tensioning device according to claim 4 wherein said signal responsive means comprises an electromagnet and said plunger forms the core of said electromagnet, and the second variable electrical signal is in the form oF a variable voltage amplitude, said electromagnet applying a force to said rod proportional to the voltage amplitude applied thereto.