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Driving both the handwheel and the bobbin winder with a single belt running in a triangular path causes traction problems at the motor, due to decreased belt contact area (from 90 degrees to about 60 degrees). This can be compensated by high belt tension, but that in turn will wear out the bearings and quickly exhaust a stretch belt.
The thread tension mechanisms, one for the upper thread and one for the lower thread, prevent either thread from pulling the entwine point out of the middle of the material. Prior to the invention of the rotating hook, lockstitch machines placed the lower bobbin inside a miniature shuttle which would be passed through the loop formed when the ...
Tension in a sewing machine refers to the pull of the thread between the needle and the bobbin. Sewing machines have tension discs and a tension regulator. If the stitch is too saggy or too tight, the most likely cause is a tension problem.
Tension of the bobbin thread is maintained with a bobbin case, a metal enclosure with a leaf spring which keeps the thread taut. The bobbin case has to be free-floating (not attached to an axle) in order to allow the top thread to pass around the bobbin completely and hook the bobbin thread. Bobbins vary in shape and size, depending on the ...
A short tension band, or brake band, adds drag to the bobbin such that when the spinner loosens their tension on the newly spun yarn, the bobbin and flyer spin relative to each other and the yarn is wound onto the bobbin. A tighter tension band increases relative torque and 'pulls' the yarn onto the bobbin more forcefully; a looser tension band ...
Needle moves slightly upward to form a small loop in the upper thread at the needle's eye. 4 Shuttle is midway, and its point ('hook') has passed through the loop in the upper thread. Upper thread is now looped around the shuttle's waist. Needle is up. 5 Shuttle is forward again, having completely passed through the loop in the upper thread.
In a sewing thread, the treads are doubled in two phases. Two or three strands are twisted together then three of these threads are twisted together, to form a six or nine cord. [9] The spun yarn is wound onto a bobbin using a doubling winding machine, and two or more of these bobbins are placed on doubling frame (doubling winding machine). The ...
The rotary hook or rotating hook is a bobbin driver design used in lockstitch sewing machines since the 19th century. It triumphed over competing designs because it can run at higher speeds with less vibration. Rotary hooks and oscillating shuttles are the two most common bobbin drivers in use today.