Device for blocking the entrance of a sheet feeder

Abstract: A device for blocking or intercepting sheets for a sheet feeder may be applied to copiers, printers and similar office machines, and comprises a lever (32) capable of detecting the presence or absence of a sheet on the sheet entry hopper (16). The lever controls a stop member (42) to prevent the introduction of further sheets when at least one sheet is still present in a hopper.

Description: The present invention relates to a device for blocking the entrance of a sheet feeder, and more particularly to a device to prevent the introduction of further sheets into the entry hopper of a feeder when at least one sheet is still present in the hopper. A device of this type may be used in copying machines, printers and other similar office machines having automotic sheet feeders. It is known, in conventional sheet feeders that, after the pick-up roller has advanced a sheet, the next sheet remains gripped between a roller and a double sheet rejection block. As a result of this, if other sheets are introduced they will become trapped between the pick-up roller and the current sheet. Consequently, on the next actuation of the pick-up roller the added sheets will be advanced in a group, causing a jam in the feeder. In DE 3531461 a device for preventing the transport of an incorrectly aligned sheet in a paper transport path is disclosed. A detection element is rotated by the leading edge of a sheet correctly aligned along a lateral reference edge. The movement of the detection element enables the actuators to move away from the path of the sheet. In turn the actuators cause the start of rotation of feeding rollers to advance the sheet. When the sheet is incorrectly aligned the leading edge does not touch the detection element. The actuators do not then move and thus prevent the sheet from being advanced. DE 3601667 discloses a similar device for preventing the transport of poorly aligned sheets. A rectilinear detection arm and two L-shaped prevention levers are mounted on a rotatable shaft. At a first position they intercept the transport path of the sheets. When an improperly aligned sheet fails to contact the detection arm, the leading edge of the sheet is prevented from advancing by the L-shaped levers. On the other hand, a correctly aligned sheet first contacts the detection arm which is then rotated to a position out of the transport path. The rotation of the detection arm causes the L-shaped levers also to rotate out of the transport path. Thus the sheet can advance freely. SUMMARY OF THE INVENTION A preferred embodiment of the present invention provides a device for blocking the entrance to a sheet feeder. An entry hopper is provided to introduce sheets on to a supporting surface. A pick-up roller removes sheets from the supporting surface and supplies them to a machine such as a photocopier. The device comprises a feeler to determine the presence of a sheet on the supporting surface. A stop member co-operates with the supporting surface and is controlled by the feeler to prevent the introduction of sheets into the hopper when at least one sheet is present on the supporting surface. The embodiment therefore provides a device which prevents the introduction of additional sheets into the hopper when at least one sheet is still present in the hopper. The invention is defined in its various aspects in the appended claims to which reference should now be made. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The invention will now be described in detail by way of example with reference to the drawings in which: Fig. 1 represents a sheet feeder including the sheet blocking device according to the invention; Fig. 2 represents the blocking device in Fig. 1 on an enlarged scale; Fig. 3 is a section along the line III-III of Fig. 2. With reference to Fig. 1, sheets 12 are inserted one at a time or in groups of not more than 50 sheets on to a table 14 of an entry hopper 16, for example that of a copying machine 10. A pick-up roller 18 is selectively rotatable in the clockwise direction to advance a sheet 12 towards a pair of registration and advancing rollers 22. A block 24 is pressed against the roller 18 by a spring 26 to restrain any subsequent sheets which may remain adhering to the first, which is to be advanced by the roller 18. On the hopper 16 (Fig. 2) there is mounted a device 30 to block sheets 12' added for example on top of a sheet 12 already present on the tray 14. The device 30 comprises a lever 32 which is rotatable on a pivot 34 fixed on two projections 36, 37 (Fig. 3) integral with an upper wall 38 of the hopper 16 parallel to the sheet support surface 39 of the tray 14, The lever 32 has its centre of gravity G in such a position with respect to the pivot 34 that the lever 32 is made to rotate by gravity in an anti-clockwise direction. A blocking member, or intercepting catch, 40, is hinged on the pivot 34 and has a first end 42 capable of resting on the surface 39 and a second end 44 capable of engaging with a projection 46 of the lever 32. One end 48 of the lever 32 intercepts the path of the sheet 12 present in the hopper 16, whereby, when a sheet; 12 is present, the lever 32 is rotated in a clockwise direction and is placed in a working position 50 shown by the continuous line in Fig. 2. Consequently the blocking member or catch 40 is not engaged by the projection 46 and, having its own centre of gravity G' in such a position that it is made to rotate by gravity in a clockwise direction, is placed by gravity with the end 42 resting on the sheet 12. In this sheet interception position of the member 40, any sheets 12' added on top of sheet 12 will be intercepted and stopped by the stop face 42' of the end 42 of the catch 40. However when sheets are not present in the hopper 16, the lever 32 may rotate in an anti-clockwise direction by gravity. The end 48 passes through the surface 39 into an aperture 41 and the lever 32 is placed in a second stable position 53, indicated by broken lines in Fig. 2. The catch 40 is then rotated in an anti-clockwise direction by the projection 46 to a position 53' in which the end 42 is raised with respect to the surface 39. In this position of the member 40, indicated by broken lines, it is possible to insert sheets in the hopper 16 and advance them up to the pick-up roller 18 (Fig. 1). During the operation of the copier 10, the pick-up roller 18 advances a sheet 12 up to the rollers 22 for its registration. A sensor 56 located before the rollers 22 signals the presence of the sheet 12 to a control circuit (not shown) of the copier 10 to proceed with the copying cycle. In the next cycle, the sheets 12' halted against the end 42 prevent the anti-clockwise rotation of the catch 40 and remain blocked as shown in Fig. 2. The sensor 56 then signals an absence of paper, as a result of which the control circuit produces an illuminated signal 58 on the panel 60 (Fig. 1) to indicate that the group of sheets 12' should be removed and reinserted in the hopper 16. As soon as the sheets 12' have been removed from the hopper 16 the catch 40 is rotated by the lever 32 to position 53', as a result of which the sheets 12' may be reinserted in the hopper 16 as far as the pick-up roller 18 (Fig. 1). It is to be understood that modifications, additions or substitutions of parts may be made to the sheet blocking device according to the invention without departing from the scope of the invention. For example, the catch 40 (Figs 2 and 3) may be replaced by a sliding block slidable perpendicularly with respect to the surface 39 and raised by the lever 32 when its end 48 enters the aperture 41 as a result of the absence of sheets on the surface 39.

Claims: A device for blocking the entrance of a sheet feeder, having an entry hopper (16) to introduce sheets onto a supporting surface (39) and a pick-up roller (18) to remove the sheets from the supporting surface, the device comprising a lever (32) rotatable from a working position (50), in which a first end (48) is kept raised by a sheet (12) present on the supporting surface (39), to a stable position (53), in which the first end (48) passes into an aperture (41) when the sheet is not present, and a stop member (40) movable in response to the rotation of the lever (32), characterized in that the stop member comprises an oscillating catch (40) having a stopping end (42) cooperating with the supporting surface (39), the catch (40) being rotated in a preferred direction by gravity to contact the stopping end (42) with the supporting surface (39) when the lever (32) is in the working position (50), and being rotated in an opposite direction by the lever (32) to an inserting position (53') in which the stopping end (42) is raised from the supporting surface (39), whereby when at least one sheet is still present on the supporting surface the stopping end (42) prevents further sheets from entering the sheet feeder. A device according to claim 1, characterized in that the lever (32) comprises a projection (46), the projection (46) driving an opposite end (44) of the catch (40) to rotate the catch to the inserting position (53') when the lever (32) is not in the working position (50). A device according to claim 1 or 2, characterized in that the lever (32) rotates on a pivot (34) and has its own centre of gravity (G) in such a position with respect the pivot (34) that the lever freely rotates to the stable position (53) in the absence of sheets on the supporting surface (39), and in that the catch (40) rotates on the pivot (34) and has its own centre of gravity (G') in such a position with respect to the pivot (34) that when the lever (32) is in the working position (50) the catch (40) freely rotates in the preferred direction until the stopping end (42) rests on the present sheet (12).

Inventors: PERINO ANDREA, PERINO, ANDREA
Applicants: OLIVETTI CANON IND SPA, OLIVETTI - CANON INDUSTRIALE S.P.A.
Application year: 1991
Main classification: B65H7
IPC codes: G03G15, B65H7, B65H43, B65H3, B65H1, B41J13