Device for outputting single sheets from a printer

A method and device for output of single sheets from a printer employs a driven first roller pair having a conveying nip in which a respective single sheet is transported and deflected from an approximately vertically proceeding conveying path into an approximately horizontal conveying path. A separation element that suppresses a continued conveying of the respective single sheet on a circumferential surface of a lower roller of the roller pair is arranged in a proximity of the circumferential surface of the lower roller. An edge sensor is arranged preceding the roller as viewed in a conveying direction for determining whether single sheets have pushed on top of one another. A discharge brush electrically discharges one side of the single sheet arranged in the conveying path following the roller pair. A deflection device deflects the single sheet emerging from the conveying nip into a substantially horizontal attitude shortly before the conveying nip as viewed in a direction of the conveying path. The discharge brush is mounted to the end of the deflection device.

BACKGROUND OF THE INVENTION
 The invention is directed to a device for outputting single sheets from a
 printer or a copier, comprising a driven roller pair in whose conveying
 nip the respective single sheet is transported and which is deflected from
 an approximately vertically proceeding conveying path into an
 approximately horizontal conveying path, and comprising a deposit
 compartment for the deposit of the conveyed single sheets.
 Such a device is utilized, for example, in high-performance printers,
 whereby the deposit compartment is a specimen compartment in which, for
 example, individual sheet specimens of a test printing are deposited.
 Traditional apparatus have shown that their operating dependability is
 limited and a paper jam in the output region occurs disproportionately
 often.
 JP-A-57 072561 discloses a device for outputting single sheets from a
 printer or copier. The single sheets are conveyed forward by a roller
 pair. A rejector unit that suppresses a further-conveying of the
 respective single sheet on the circumferential surface of this roller is
 arranged at the roller.
 U.S. Pat. No. 4,511,238 discloses a device in an electrophotographically
 working copier. This device successively supplies single sheets to further
 units. A sensor, for example a mechanical sensor, acquires the presence of
 a single sheet between conveyor rollers.
 U.S. Pat. No. 4,570,801 discloses a device for conveying single sheets. An
 optoelectronic sensor checks the conveyed single sheets. When a jam
 occurs, for example due to single sheets sliding on top of one another,
 this jam is reported to a higher-ranking control.
 JP-A-58 089557 discloses a paper output unit of a copier machine where
 single sheets are conducted between rollers. Each single sheet passes a
 guide that assures that the single sheet is supplied to a deposit
 compartment.
 SUMMARY OF THE INVENTION
 An object of the invention is to specify a device for the output of single
 sheets that works operationally dependably and avoids a paper jam.
 This object is achieved by the initially cited device in that a rejection
 unit is arranged in the proximity of the circumferential surface of the
 lower roller of the roller pair, this rejection unit suppressing a
 continued conveying of the respective single sheet on the circumferential
 surface of the lower roller.
 The invention is based on a perception that it is precisely the lower
 roller of the roller pair that is critical, since single sheets are still
 held at the generated surface due to electrostatic forces or the force of
 gravity in the transition between vertical conveying and horizontal
 conveying, and can be drawn into the structural necessary gap between
 lower roller and deposit compartment, whereby they can cause a paper jam.
 According to the invention a rejection or separating element is arranged
 in the proximity of the circumferential surface of the lower roller. This
 rejection or separating element lifts the respective single sheet off from
 the generated surface of the lower roller, and adhesion of the single
 sheet is no longer possible. The single sheet is compelled to pass through
 the discharge gap between roller pair and deposit compartment. The present
 invention thus works operationally dependably and reliably.
 The generated surface of the lower roller preferably has at least one
 channel-shaped recess into which the rejection or separating element
 engages. When this rejection unit is designed as a flashing, it has front,
 finger-like sections engaging into the recess or into a plurality of
 recesses on the generated surface of the lower roller. As a result of this
 arrangement, the single sheet is reliably lifted off from the generated
 surface of the lower roller, as a result whereof a wrapping of the lower
 roller is made impossible.
 According to the invention, a discharge brush which preferably electrically
 discharges that side of the single sheet lying up is arranged in the
 conveying path following the roller pair. The discharge brush is thus
 arranged at a position such that the single sheet is no longer in
 frictional contact with conveyor elements. The electrostatic discharge of
 the sheet can thus no longer be reversed by such conveyor elements. The
 single sheets deposited in the deposit compartment thus do not adhere due
 to electrostatic effects and can be easily individually separated from one
 another.
 In the invention, an edge sensor with the assistance of which a
 determination can be made as to whether prescribed intervals are adhered
 to between single sheets following one another is arranged preceding the
 roller pair as viewed in a conveying direction. The structure of such an
 edge sensor is known in and of itself For example, the edge sensor can be
 designed as a light barrier that indicates the lack of a sheet within the
 light barrier. When conveyed single sheets slide on top of one another in
 the conveying path, then the edge sensor can no longer detect a starting
 edge or, respectively, ending edge of single sheets. Such a condition is
 then interpreted as a paper jam. The operating dependability of the
 apparatus is further enhanced by this technique.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 An exemplary embodiment of the invention is described below with reference
 to the single Figure. This Figure shows the output-side apparatus section
 of a high-performance printer that successively prints single sheets. The
 single sheets 12 are individually successively deposited in a specimen or
 sample compartment and can be removed individually or as a packet. A
 roller pair 18 with an upper roller 20 and a lower roller 22 serves the
 purpose of forward conveying of the single sheets 12. The single sheets 12
 are conveyed up via a vertically proceeding paper channel 24, reach the
 conveying nip in the roller pair 18, are subsequently diverted into a
 horizontal attitude and are then deposited in the specimen or sample
 compartment 14.
 The lower roller 22 has annular recesses in the fashion of channels on its
 generated surface. Fingers of a flashing or baffle 26 as a separation
 element engage into these channels. When conveying single sheets 12
 through the conveying nip, the flashing 26 reliably lifts or separates the
 respective single sheet 12 from the generated surface of the lower roller
 22, so that it cannot remain adhering to the surface of the lower roller
 22 due to the force of gravity or due to electrostatic forces.
 The single sheets conveyed through the conveying nip are redirected by a
 deflection element 28, i.e. the conveyed edge of a conveyed single sheet
 strikes the arced, leading surface 30 inclined in the direction of the
 horizontal line in the deflection unit designed as a profile, whereby the
 single sheet 12 is deflected little by little from the vertical paper
 channel 24 via the conveying nip and the deflection element or device 28
 into a horizontal attitude and is then gently output onto the stack of
 single sheets 12 in the specimen compartment 14.
 The attack angle of the surface 30, the angle of the plane proceeding
 through the rotational axes 32, 34 of the roller pair 18 and the bent-over
 end 36 of the guide profile arranged in the paper channel 24 are matched
 to one another such that the respective single sheet 12 is deflected from
 the vertical into the horizontal upon exertion of slight forces.
 At its end remote from the roller pair 18, the deflection element or device
 28 carries a discharge brush 40 that frees the upper side of the single
 sheet 12 from electrostatic charges. Since this upper side of the single
 sheet 12 subsequently no longer comes into contact with further conveyor
 elements, a renewed electrostatic charging cannot occur. The single sheets
 12 of the stack 10 can thus be also easily withdrawn individually without
 overcoming electrostatic forces.
 A light barrier 42 is arranged preceding the roller pair 18 as viewed in
 the conveying direction. Whether prescribed intervals are still present
 between successive single sheets 12 or whether single sheets have slipped
 on top of one another as a result of a paper jam can be recognized with
 the assistance of this light barrier. When the latter is true, then a
 control signal that indicates a paper jam condition and potentially shuts
 down the printer can be determined from the signal of the light barrier.
 A further roller pair 44 is shown in FIG. 1 that supplies single sheets to
 a further output compartment (not shown). Dependent on the position of the
 shunt 46, single sheets are supplied either to the roller pair 18 (this
 condition is shown in the Figure) or to the roller pair 44.
 The apparatus of the invention makes it possible to arrange the discharge
 opening behind the roller pair 18 relatively far toward the top at the
 upper end of the entire frame 48 of the printer, as a result whereof the
 stacking capacity of the specimen or sample compartment 14 is enlarged.
 The combination of baffle or flashing 26, deflection element or device 28
 and discharge brush 40 means that a paper jam is avoided and the overall
 output of single sheets into the specimen compartment 14 occurs reliably.
 Although various minor changes and modifications might be proposed by
 those skilled in the art, it will be understood that our wish is to
 include within the claims of the patent warranted hereon all such changes
 and modifications as reasonably come within our contribution to the art.