Device for conveying sheetlike material

A device for conveying sheet-like material between a driven roller and a counter-pressure roller is disclosed. The device also includes opposing guide plates that form a channel for feeding the sheet-like material to the nip between the two rollers. At least one of the rollers includes a channel-like recess into which its associated guide plate extends.

FIELD OF THE INVENTION
 The invention is directed to a device for conveying sheet-shaped material.
 BACKGROUND OF THE INVENTION
 Such a device is utilized, for example, in a single-sheet printer in order
 to convey single sheets of paper from one processing station to a next
 processing station. More recent printers require a plurality of such
 conveyor devices, so that the demand for high operating dependability is
 made of these. It can occur in traditional conveyor devices that, given
 imprecise guidance of the leading edges, of the trailing edges and of the
 side edges of a single sheet, a corner of the single sheet can be bent
 over and the corner that has been bent over, what is referred to as a "dog
 ear", is fixed in the fashion of an ironing procedure due to the transport
 of the roller and counter-pressure roller lying opposite one another. Such
 a bent-over corner leads to a reject or can lead to a paper jam in the
 printer over the course of the further conveying path. It is therefore
 desirable to increase the operating dependability of such a conveyor
 device.
 U.S. Pat. No. 5,040,781 discloses a device for conveying sheet material
 that is not flat, for example envelopes. The counter-pressure roller of
 this device has channel-shaped recessed in which the longitudinal edges of
 the envelope proceed. An obliquely guided envelope thus does not cause a
 conveying jam.
 German AS 22 55 920 discloses a device for conveying card-shaped data
 carriers. The device has a driven roller that has a free-running
 counter-pressure roller residing opposite it. The data carriers are
 conveyed in the conveying nip between the two rollers.
 DE-A 39 30 737 discloses a paper conveying means for printer devices,
 whereby paper is conveyed in the conveying nip between a driven roller and
 a counter-pressure roller that is likewise driven. The roller and the
 counter-pressure roller have recesses into which guide plates that supply
 the sheet-shaped material to the generated surfaces of the roller and the
 counter-pressure roller project.
 Patent Abstracts of Japan, vol. 016, No. 195 (M-1246), May 12, 1992 and
 JP-A-04 028640 (Canon, Inc.), Jan. 31, 1992, disclose a paper guide unit
 wherein a counter-pressure roller has channel-shaped recesses into which
 tongues of a pressure plate engage. During operation, a single sheet is
 conveyed along the circumference of a conveyor roller in the conveying nip
 between conveyor roller and the pressure plate. The tongues engaging into
 the channel-shaped recesses of the counter-pressure roller guide the
 single sheet to the circumferential surface of the counter-pressure
 roller.
 U.S. Pat. No. 3,957,366 discloses a paper delivery means wherein conveyor
 rollers residing opposite one another contain channel-shaped recesses.
 Nose-shaped sections that are bent off at their ends and that have two
 operating positions project into these recesses. In the one operating
 position, the bent-off ends serve as detents that hold the single sheet at
 the front end edge, so that it arcs up given continued conveying. In the
 other operating position, the sections are lifted so that they release the
 single sheet and it is further-conveyed by the conveying nip formed by the
 rollers. The nose-shaped sections serve for aligning the single sheet, so
 that, after being supplied slanting, it can be further-conveyed with
 correctly aligned end edge.
 U.S. Pat. No. 5,147,274 discloses an alignment means for sheet material.
 The sheet material is conveyed between rollers residing opposite one
 another. The longitudinal edges of the sheet material run freely between
 roller elements.
 Therefore, there is a need for a device for conveying sheet-shaped material
 that works disturbance-free with high dependability.
 SUMMARY OF THE INVENTION
 The above need is satisfied by the present invention, wherein the guide
 plate engages into the channel-shaped recess. The individual sheets are
 thus reliably supplied to the generated surface of the roller or,
 respectively, of the counter-pressure roller. A tilting of the leading
 edges of the single sheet or of the lateral edges is largely precluded.
 In one exemplary embodiment of the invention, at least one longitudinal
 edge runs in the channel-shaped recess. The corners of longitudinal edges
 of a sheet-shaped material, namely, can present problems during conveying
 since they can easily yield and be bent over when striking against
 counter-surfaces. The embodiment then provides that such longitudinal
 edges remain reserved from the pressure of the roller and of the
 counter-roller, i.e. run loosely along during conveying. Accordingly, no
 force that can effect a bending of the corners or of the edges can attack
 at such longitudinal edges. Consequently, the conveying of sheet-shaped
 material becomes more dependable then hitherto and ensues
 malfunction-free. Even if a plurality of conveyor devices of the invention
 are utilized in a single printer, the probability of outage due to
 conveying malfunctions is hardly increased since a faulty folding at the
 longitudinal edges cannot occur.
 The shape of the recess provided in the invention can be rectangular,
 quadratic, semi-circular. The recess proceeds along the circumference of
 the respective roller. The recess or, respectively, the recesses can only
 be arranged on one roller, for example on the driven roller or on the
 counter-pressure roller. However, it is also possible to provide recesses
 on both rollers, whereby one preferably avoids having two recesses
 residing directly opposite one another.
 The appertaining roller preferably has recesses at the locations at which
 longitudinal edges of single sheets of different width and formats
 proceed. What is thereby achieved is that it is also assured given a
 change in format that the longitudinal edges of the respective single
 sheets proceed within recesses and are conveyed merely force-free.
 According to one embodiment of the invention, a paper running channel is
 formed by guide plates at at least one side of the conveying nip, these
 guide plates opening tunnel-shape in the direction of the conveying nip.
 The guide plates have salient sections that at least partially engage into
 the recess or, respectively, the recesses.
 Given this type of arrangement of the guide plates, it is assured that a
 sheet of the sheet-shaped material is reliably supplied to the conveying
 nip between the roller and the counter-pressure roller or, respectively,
 is discharged therefrom without the leading edge or, respectively, the
 trailing edge of the sheet-shaped material being greatly bent down.
 In an embodiment, the present invention provides a device for conveying
 sheets of material. The device comprises a cylindrical driven roller
 disposed opposite a cylindrical free wheeling counter-pressure roller. The
 driven roller and the counter-pressure roller are capable of engaging one
 another to form a conveying nip disposed therebetween. The
 counter-pressure roller comprises at least one circumferential
 channel-shaped recess. The driven roller comprises at least one
 circumferential channel-shaped recess. The at least one recess of the
 counter-pressure roller is aligned with the at least one recess of the
 driven roller. The device further comprises first and second parallel and
 opposing guide plates disposed on opposing sides of the nip. The guide
 plates define a channel for delivering the sheets of material to the nip.
 The first guide plate extends into the recess of the counter-pressure
 roller and the second guide plate extends into the recess of the driven
 roller. The first guide plate is pivotally mounted to the device and
 capable of being pivoted away from the driven roller.
 In an embodiment, the guide plates are flared outward away from each other
 at the nip to thereby define a wider channel at the nip.
 In an embodiment, the driven roller comprises two recesses disposed on
 opposing sides of a wider driving section that engages the
 counter-pressure roller. The second guide plate comprises a window-like
 aperture for at least partially accommodating the driving section of the
 driven roller. The second guide plate further comprises webs that extend
 through the two recesses of the driven roller and on opposing sides of the
 driving section thereof.
 In an embodiment, the driven roller has a longitudinal axis and the second
 guide plate comprises a flared guide element disposed parallel to the
 longitudinal axis of the driven roller and at one side of the aperture.
 The flared guide element extending away from the counter-pressure roller.
 In an embodiment, the first guide plate is pivotally mounted to the device
 for pivotal movement away from the counter-pressure roller.
 In an embodiment, the counter-pressure roller comprises two recesses
 disposed on opposing sides of a wider engagement section that engages the
 driven roller. The first guide plate comprises a window-like aperture for
 at least partially accommodating the engagement section of the driven
 roller. The first guide plate further comprises webs that extend through
 the two recesses of the counter-pressure roller and on opposing sides of
 the engagement section thereof.
 In an embodiment, the counter-pressure roller has a longitudinal axis and
 the first guide plate comprises a flared guide element disposed parallel
 to the longitudinal axis of the counter-pressure roller and on one side of
 the aperture. The flared guide element extends away from the driven
 roller.
 Other objects and advantages of the present invention will become apparent
 from reading the following detailed description and appended claims, and
 upon reference to the accompanying drawings.

It should be understood that the drawings are not necessarily to scale and
 that the embodiments are sometimes illustrated by graphic symbols, phantom
 lines, diagrammatic representations and fragmentary views. In certain
 instances, details which are not necessary for an understanding of the
 present invention or which render other details difficult to perceive may
 have been omitted. It should be understood, of course, that the invention
 is not necessarily limited to the particular embodiments illustrated
 herein.
 DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
 FIG. 1 shows a conveyor device of the invention. A plurality of such
 conveyor devices are utilized, for example, in a high-performance printer
 for printing single sheets. A driven, essentially cylindrical roller 10 as
 well as a free-running, likewise essentially cylindrical counter-pressure
 roller 12 lying opposite it form a conveying roller pair in whose
 conveying nip 13 single sheets of paper can be successively conveyed in
 both directions. Paper running channels 14 are formed by upper guide
 plates 16 and lower guide plates 18 at both sides of the conveying nip 13.
 As indicated in FIG. 1, the ends of the guide plates 16, 18 engage into
 recesses in the rollers 10, 12, as can be seen in greater detail in FIG.
 2.
 FIG. 2 shows a part of a view onto the counter-pressure roller 12 seen from
 below. The counter-pressure roller 12 has recesses 20, 22, 24 disposed on
 opposing sides of engagement sections 12a, 12b and that proceed
 channel-shaped around the axis 26 of the counter-pressure roller 12. The
 recesses 20, 22, 24 have a rectangular cross-section in the present case.
 The upper guide plates 16 have projecting sections engaging into the
 recesses 20, 22, 24. Given a transport of single sheets, thus, the leading
 edge or, respectively, the trailing edge of a single sheet is guided such
 that nearly no sag ensues. In this way, the circumferential surfaces of
 the counter roller 12 sees the leading edge or, respectively, the trailing
 edge of the single sheet simultaneously and gently, so that a buckling of
 the leading edge or, respectively, of the trailing edge is not possible.
 A longitudinal edge 28 of a single sheet is shown as a dashed line in FIG.
 2. The longitudinal edge 28 proceeds approximately centrally within the
 recesses 20. When conveying the single sheet, no pressure bears on this
 longitudinal edge 28 within the recess 20. It can therefore also not be
 bent over--a paper jam or a creasing of the page is avoided.
 It is to be pointed out that the generated surface of the counter-pressure
 roller or, respectively, of the roller preferably has a layer with high
 friction in order to convey the individual sheets with optimally little
 slippage.
 FIG. 3 shows a further exemplary embodiment of the invention wherein the
 paper running channel 14 is formed by two upper guide plates 16 arranged
 at both sides of the roller 10 and counter-pressure roller 12 as well as
 of a lower, continuous guide plate 18. The upper guide plates 16, which
 are pivotably mounted at 16a to the device, can be pivoted out in the
 direction of the arrows P1, P2 in order to be able to remove the single
 sheet or, respectively, sheets in case of a paper jam. The lower guide
 plate 18 has a window-like recess 30 with lateral webs 32. The aperture 30
 accommodates the driving section 1 Oa of the roller 10. Recesses in the
 roller 10 are shown at 10b, 10c. The lateral webs 32 proceed within the
 channels 20, 22 of the pressure roller 10. The continuous guide plate 18
 has two guide elements 34, 36 within the window-shaped recess 30 whose
 leading edges 34a, 36a are bent off in the direction of the longitudinal
 axis 38 of the roller 10. Given delivery of single sheets, the leading
 edge runs onto the bent-over section of the respective guide elements 34,
 36 and is thus conveyed further along the guide plate 18--a threading of
 the leading edge of the single sheet into the gap between the guide
 elements 34, 36 and the roller 10 is thus avoided. Due to the symmetrical
 arrangement of the guide elements 34, 36, a reliable conveying in both
 conveying directions is assured.
 From the above description, it is apparent that the objects of the present
 invention have been achieved. While only certain embodiments have been set
 forth, alternative embodiments and various modifications will be apparent
 from the above description to those skilled in the art. These and other
 alternatives are considered equivalents and within the spirit and scope of
 the present invention.