GB1367211A - Drive mechanism for a reciprocating member - Google Patents

Abstract

1367211 Punching INTERNATIONAL BUSINESS MACHINES CORP 4 Sept 1972 [28 Oct 1971] 40854/72 Heading B3W [Also in Division F2] A drive mechanism for a reciprocating member, e.g. the punch 100 of a web punching apparatus, comprises a pendulum-like oscillating drive member 111 coupled to the punch 100 by a cable 110 and mounted on a rotating support 104 and oscillatable under the control of centrifugal force resulting from the rotation of the support 104, and control means comprising a cam follower 114 coupled to the drive member 111 and controlled by a cam member 118 for initially moving the drive member 111 to one limit of its oscillating movement, so that subsequently the centrifugal force causes oscillation of the drive member 111 and corresponding reciprocation of the punch 100. The drive member 111 is an eccentrically weighted pulley, the weight 115 being so located that its mass centre of oscillation is furthest from the axis of rotation of the support 104 when the punch 100 is at the midpoint of its reciprocation stroke. The support 104 is screwed to a hollow shaft 101 for rotation. Cam follower 114 has a laterally projecting pin 116 that rides in a cam groove 117 in the inner radial face of the cam member 118 which is suitably anchored and disposed about the rotating shaft 101. Springs 103 nested in the support 104 act, through a plate 105, on the rear face 106 of punch 100 to maintain its V-shaped sides in slidable surface contact with corresponding mating surfaces of a die 107. The cutting edge 102 cuts V-shaped notches to remove triangular chips C from one edge of a web 108, the chips being removed through the hollow shaft 101 which is connected to a vacuum source. The mass and radius of oscillation of weighted pulley 111 are calculated to cause the pulley to oscillate at a fundamental natural frequency synchronized with the angular velocity of punch 100 as the punch will complete an integral number of harmonic reciprocations per revolution of shaft 101. Cam member 118 and cam follower 114 are provided merely to positively ensure that such synchronization will be maintained despite frictional drag. Driving force exerted by the pulley 111 on the punch 100 thus desirably increases as the angular velocity of the shaft 101 increases, whereas the load on the cam member 118 remains substantially negligible irrespective of angular velocity. This enables operation at very high rotational (and hence reciprocating) speeds that produce centrifugal forces significantly exceeding those possible with prior art arrangements.