Device and method for feeding cut sheets of paper in a one-by-one picking up manner without jamming

A cut sheet cassette for accommodating therein a plurality of neat stacked cut sheets of paper, said cassette being cooperative with a paper feed system including a pickup roller which is rotatable, in a paper pickup phase of a feed cycle of said system, in frictional contact with a top sheet of said plurality of cut sheets to force the same to slide in a forward sense of a substantially longitudinal direction of said cassette in accord with a paper feed direction of said system, so-that said top sheet can be picked up from said cassette into said system, said cassette comprising:

• a casing assembly including a front wall portion formed with a front opening having a slightly smaller transverse width than said plurality of cut sheets, a rear wall portion, and a side wall portion;
• a stack plate fitted in said casing assembly, in a vertically swingable manner about a rear edge thereof pivoted to said rear wall portion of said casing assembly;
• said stack plate cooperating with said front wall portion, said rear wall portion and said side wall portion of said casing assembly to define a substantially rectangular parallelepiped stack zone for holding therein said plurality of cut sheets, as they are stacked on said stack plate;
• a downwardly pointing first pickup pawl fronting either of a pair of transverse end regions of a front area of said stack zone from thereabove:
• a downwardly pointing second pickup pawl fronting the other of said pair of transverse end regions of said front area of said stack zone from thereabove;
• a spring member for normally upwardly biassing said stack plate, providing the same with a tendency to upwardly swing, causing said plurality of cut sheets to be each rearwardly shifted with a play left between a front periphery thereof and said front wall portion of said casing assembly, while bringing said front periphery of said top sheet into contact with said first and second pickup pawls so that, in said pickup phase of said feed cycle of said system, said first and second pickup pawls frictionally hold both ends of said front periphery of said top sheet, giving them twisting tendencies;
• and
• a stripe means provided on a front portion of said stack plate, for normally giving an upward deformation to an intermediate length of said front periphery of each of said plurality of cut sheets so that, in said pickup phase of said feed cycle of said system, said front periphery of said top sheet has along said intermediate length thereof an upwardly deforming tendency induced by each of and intensified by synergism between said upward deformation and said twisting tendencies, wherein:
• said stripe means comprises a bar member fixed to said front portion of said stack plate, said bar member extending in a crossing direction with respect to said longitudinal direction of said cassette;
• said stack plate has in said front portion thereof a plurality of central fixing means arranged substantially in a crossing direction with respect to said longitudinal direction of said cassette;
• and
• said bar member is detachably fixed to one of said plurality of central fixing means.

A cut sheet cassette for accommodating therein a plurality of neatly stacked cut sheets of paper, said cassette being cooperative with a paper feed system including a pickup roller which is rotatable, in a paper pickup phase of a feed cycle of said system, said pick up roller being in frictional contact with a top sheet of said plurality of cut sheets in order to force the top sheet to slide in a forward sense along a substantially longitudinal direction of said cassette in accord with a paper feed direction of said system, so that said top sheet can be picked up from said cassette and feed into said system, said cassette comprising:

• a casing assembly including a front wall portion formed with a front opening having a width that is a slightly smaller transverse than a width of said plurality of cut sheets, a rear wall portion, and a side wall portion;
• a stack plate fitted in said casing assembly, to swing in a vertical manner about a rear edge thereof, said stack wall being pivotally coupled to said rear wall portion of said casing assembly;
• said stack plate cooperating with said front wall portion, said rear wall portion and said side wall portion of said casing assembly to define a substantially rectangular parallelepiped stack zone for holding said plurality of cut sheets therein as they are stacked on said stack plate;
• a downwardly pointing first pickup pawl confronting either one of a pair of transverse end regions at a front area of said stack zone from thereabove;
• a downwardly pointing second pickup pawl confronting the other of said pair of transverse end regions of said front area of said stack zone from thereabove;
• a spring member for normally biassing said stack plate upwardly, said spring bias providing the stack plate with a tendency to swing upwardly, causing each of said plurality of cut sheets to be rearwardly shifted with a play left between a front periphery thereof and said front wall portion of said casing assembly, while bringing said front periphery of said top sheet into contact with said first and second pickup pawls so that, in said pickup phase of said feed cycle of said system, said first and second pickup pawls frictionally hold both ends of said front periphery of said top sheet, giving them a twisting tendency;
• and
• a stripe means provided on a front portion of said stack plate, said stripe means normally giving an upward deformation to an intermediate length of said front periphery of each of said plurality of cut sheets so that, in said pickup phase of said feed cycle of said system, said front periphery of said top sheet has along said intermediate length thereof an upwardly deforming tendency induced by each of and intensified by synergism between said upward deformation and said twisting tendencies, wherein:
• said stack zone has a variable total area;
• and
• said stripe means comprises a first bar member slidable along a cam groove formed in said front portion of said stack plate, within a near region thereof to either of said pair of transverse end region of said front area of said stack zone, and a second bar member detachably fixed to one of a plurality of fixing means arranged in a substantially crossing direction with respect to said longitudinal direction of said cassette, over a far region of said front portion of said stack plate from either of said pair of transverse end regions of said front area of said stack zone.