Sheet transfer cylinders

Claim 1

A sheet transfer apparatus for a rotary printing machine capable of successive printing selectively on one or both sides of a sheet, comprising a transfer cylinder mounted between the side walls of said machine for rotation about its central axis and being provided adjacent the surface thereof with a fixed transverse bar and with a rotatable shaft spaced therefrom, gripping means secured to said shaft in opposition to said bar, said bar and said gripping means adapted to receive the edge of a sheet therebetween, and means for selectively actuating said shaft to cause said gripping means to engage said transverse bar and hold said sheets during rotation of said cylinder, comprising a fixed centering ring mounted between said transfer cylinder and one side wall coaxially with the axis of rotation of said transfer cylinder, said centering ring having a pair of circular segments secured to opposed peripheral faces of said centering ring adjacent each other, said segments having radially extending circular cam surfaces, roller means carried at one end of said shaft adjacent said centering ring for engaging the cam surfaces of each of said circular segments, means for biasing said roller means to engage with said cam surfaces, said engagement causing said gripping means to be activated into engagement with said transverse bar, the first of said segments being fixed with respect to said centering ring and the second of said segments being circumferentially adjustable with respect to said first of said segments to vary the length of engagement of said rollers with said cams whereby the point at which said grippers are free from engagement with said transverse bar is adjustable relative to the degree of rotation of said transfer cylinder.