GB1321246A - Undertrimmer mechanism in a sewing machine - Google Patents

Abstract

1321246 Trimming mechanism SINGER CO 1 Oct 1970 [7 Oct 1969] 46701/70 Heading DIG A sewing machine work trimming mechanism comprises a blade 119 co-operating with a ledger blade 121, means being provided to vary the amplitude of oscillation of the blade simultaneously with a variation of the vertical position of that blade. Oscillatory motion of the cutter blade 119 is provided by a bed shaft eccentric mechanism 31, 32 connected to the centre of a driving lever 34 the ends of which are respectively coupled to a crank arm 49 on a rock shaft 52 and a slide 40 on a pin 42 carried in a tiltable yoke 43. A further crank arm 55 on the rock shaft 52 is connected to one end of an arm 59 of a bell crank lever 60 pivoted at 61 to a lever element 89 urged against a spring biased pin 99 by a finger 93 on a control shaft 80. The other arm 62 of the bell crank lever 60 carries the blade 119 for co-operation with a ledger blade. A cam 74 rotatable by a handle 71 presents a notched cam track 76 to a follower 77, 78 secured to a control shaft 80, a selected position of the cam thus turning the control shaft to a corresponding angular position, a linkage (83, 86 Fig. 5 not shown) connecting the shaft 80 to the yoke 43. Angular movement of the shaft 80 by movement of handle 71 thus tilts the yoke 43 to set a particular cutter stroke and, through lever element 89, moves the centre of oscillation of the bell crank lever 60 and thus the vertical elevation of the cutter blade 119. In this embodiment the effect is to maintain the lower position of the blade irrespective of the stroke set (Figs. 11a-d not shown). A ply separator (113, Figs. 9 and 10 not shown) has a hook shaped end and is interposed between two plies to be stitched to raise the upper ply so that only the lower ply is severed.