Device for the feeding of flat materials

Feeding device for flat materials for processing, such as sheets and envelopes, for machines using these materials, such as printers, comprising a frame and a movable support whereon a stack of said materials may be arranged and from which these materials are extracted one by one during selection cycles by selecting means meshing with a driving mechanism and suitable for displacing the top material of the stack to feed said top material into the machine, elastic means being provided for urging the movable support in the direction of the selecting means,

• said feeding device further comprising a retracting mechanism arranged so as to push back during at least one phase of a selection cycle the movable support against the action of the elastic means by a predetermined distance which is substantially constant and independent of the thickness of the stack of materials, so as to obtain a predetermined gap between the top material and the selecting means and of a magnitude such that friction between the top material and the selecting means is eliminated,
• wherein said retracting mechanism comprises kinematic linkage members linking the driving mechanism with said movable support so that the latter, in said phase, effects a predetermined movement starting from a first position wherein said stack is resting against said selecting means to a second position wherein the top material is removed from said selecting means by said predetermined gap, said movement being substantially constant whether the position occupied by said movable support member in said first position and whatever the thickness of said stack.