Mechanism for adjusting the ink supply zone in a two drum stencil duplicator

Claim 1

A stencil duplicator comprising a lower drum and an upper drum mounted rotably in parallel relationship; drive means for said drums including a continuously rotating drive shaft; an endless ink cloth trained around said drums to support a stencil; means for supplying ink to said ink cloth and including an ink tube extending parallel to the lower drum at a short distance therefrom, said ink tube being provided with a number of ink discharge apertures facing the lower drum; a zone adjustment member movably arranged in said ink tube to adjust the ink supply through said discharge apertures to any one of a number of different zones in the transverse direction of said ink cloth; and an adjusting mechanism to position said zone adjustment member for supplying ink in a desired zone; said adjusting mechanism comprising a number of individual operating members equal to the number of ink supply zones and a coupling which is selectively actuatable by each of said operating members to provide a drive connection between said drive shaft and said zone adjustment member and interrupt said drive connection when the zone adjustment member reaches the position corresponding to the ink supply zone associated with said operated member wherein said coupling comprises a coupling shaft connected with said zone adjustment member; a ball holder mounted rotatably on the coupling shaft; a number of balls accomodated in said ball holder; a gear wheel mounted rotatably on said coupling shaft on one side of said ball holder and having a plane abutment face facing said balls; transmission means for connecting said gear wheel with the drive shaft; a coupling disc secured on said coupling shaft on the other side of the ball holder and having a number of abuTment faces equal to the number of balls, each of said abutment faces being inclined relative to the axis of the coupling shaft, so that the axial distance between oppositely located points of said abutment face and said plane abutment face of the gear wheel decreases in the direction of rotation of the gear wheel; and means for biasing the ball holder relative to the coupling disc in said direction of rotation to clamp the balls between the inclined abutment faces on the coupling disc and the plane abutment face on the gear wheel, the ball holder being provided on its outer side with a number of stops equal to a number of individual operating members and each operating member comprising an element arranged to be inserted into the path of movement for an associated stop on the ball holder to prevent rotation thereof, whereby rotation of the coupling disc is prevented.