ES314159A1 - IMPROVEMENTS IN THE DRIVING DEVICES OF AN ELECTRIC SEWING MACHINE - Google Patents

Abstract

In a sewing machine, driving and driven pulleys are interconnected by endless belts via a reduction gear arrangement mounted on at least one telescopic linkage pivoted substantially co-axially with at least one of the pulleys, and the linkage is subjected to resilient bias such that the belts are automatically tensioned irrespective of their length. A motor 6, mounted on a sewing machine base 3 and covered by a hood 7, has a shaft 5 connected by a pulley 4 and an endless belt 10 to a large pulley 11 on a shaft 12. A pulley 8 on the arm shaft 9 of the machine is connected by an endless belt 13 to a small pulley 14 on shaft 12. The latter is mounted on a link 16 loosely guided at its lower end on the machine frame 2 by a stud 21 and telescopically engaged at its upper end with the lower end of a link 15 pivoted at its upper end co-axially with shaft 9. Links 15, 16 are biased apart by a spring 17 for tensioning belt 13. Telescopic links 23, 24 are pivoted at their outer ends co-axially with shafts 12 and 5 respectively, and are biased apart by a spring 25 for tensioning belt 10, nuts 19 and 27 are provided for adjusting the tension of springs 17 and 25. In a modification, Fig. 3, (not shown), a plate (54) is pivoted at its upper end coaxially with the arm shaft (47), and is loosely attached to the machine frame at its lower end by a stud (56). A plate (57), slidably mounted on plate (54), carries a shaft (63) journalling a pulley (65) having a small sheave connected by a belt (77) to a pulley on shaft (47) and a large sheave connected by a belt (78) to a motor-driven pulley. Plate (57) is biased downwards by a spring (70) for tensioning belt (77), and the lower end of plate (54) is biased away from the motor-driven pulley by a spring (75) for tensioning belt (78).