GB853019A - Mechanism for controlling the displacement of machine parts - Google Patents

Abstract

853,019. Sewing machines. MEFINA S. A. Jan. 7, 1959 [Jan. 14, 1958], No. 647/59. Class 112 [Also in Group XXIV] In a mechanism for controlling the displacement of a machine part, such as a cam 3 which is movable into two different axial positions to control a needle-carrier or work feed device in an embroidery sewing machine in accordance with digital electric signals received from a perforated programme sheet 17, the cam 3 carrying a number (four) of rachet teeth 4a, is biased right by a spring 12 into contact with pegs 11 of a fixed follower, and is frictionally mounted on a shaft 1 which is continuously oscillated through an angle 2 equivalent to half the pitch of the ratchet teeth, whereby when anti-clockwise rotation of the cam is arrested by one or other of teeth 13a, 13b of a selectively controlled pawl 13, the cam 3 rests either with its high or low points in contact with the fixed pegs 11, thus determining the axial position of the cam 3. The pawl 13 is normally pulled by a spring 15 so that the pawl tooth 13b is effective and the cam 3 remains in its rightward position. When an electromagnet 16 is impulsively engergized from the programme sheet 17, the pawl tooth 13a is effective to set the cam leftwards by an angle 2, but only for the duration of the impulse, additional impulses being required if that setting is to be repeated. The frictional mounting of the cam 3 on the shaft I comprises radially spring pressed balls 5, 6 engageable in internal recesses in the cam 3 which are spaced at half ratchet teeth pitch to locate the cam on the shaft in its selected settings. A circuit breaker 19, in series with the programme switch 17, breaks the circuit during operation of the switch 17 to prevent sparking at the latter. Figs. 5 and 6 (not shown) have multiple cams of different heights side-by-side on a common shaft to predetermine a large number of axial positions under control of electromagnets and pawls grouped about the cams. This arrangement includes a variable-stroke mechanism between the reciprocating members 35, Figs. 9, 10, which receive the controlled axial movement of the cam and a final output sleeve 28 which passes the axial movement to the machine. This mechanism comprises a pair of levers 31 loaded by springs 34 and oscillated about pivots 30 in a fixed frame 29 by the reciprocation of the input members 35. Tappets 37 fixed to the final output sleeve 28 bear in circular recesses in the levers 31 to cause the oscillating levers to reciprocate the final output sleeve 28, and the ratio between the axial stroke of the output members 35 and that of the sleeve 28 can be varied by turning the sleeve 28 on its own axis to vary the radius of action of the tappets 37 with respect to the lever pivot 30.