Apparatus for separating printed media

An apparatus separates printed media, especially letters or envelopes, which are disposed as stacks between a spring-mounted curved pressure plate and drive rolls as well as a guide plate inclined slightly to the rear. Cylindrical envelope surfaces of the drive rolls project through openings in the guide plate. The printed media are transported away to the side. Such an apparatus is used in mail processing systems for reliably pre-separating and separating the printed media with the lowest possible technical outlay and space requirement. The apparatus includes a pre-separating area with drive-roll combinations having different coefficients of friction and a common, separate drive with freewheeling as well as a separating area with separating elements, a sensor for detecting printed media, an ejection-roll pair on the outlet side and a common, separate drive. The sensor is disposed in the vicinity of the separating elements and is linked electrically to the drive for the drive-roll combinations, in such a way that the drive is switched to freewheeling when the start of a printed medium is detected and is switched on when the end of a printed medium is detected. In this way, a jam upstream of the separating area is effectively avoided.

BACKGROUND OF THE INVENTION
 Field of the Invention
 The invention relates to an apparatus for separating printed media, in
 particular letters or envelopes, which are fed in a stack.
 The letters or envelopes may have different thicknesses and permissible
 formats in an irregular sequence. The processing of letters or envelopes
 which occur in such a manner is referred to as a mixed-mail operation.
 Mail processing systems usually include a mail separating apparatus in
 which the letters or envelopes are fed successively in a stack, are
 separated and, if required, are closed, a franking and/or addressing
 machine with an optional balance, and a depositing apparatus, as is seen
 in German Utility Model DE-M 96 09 167.3.
 The apparatus according to the invention is a component of a letter
 separating apparatus.
 A configuration for pre-separating the printed media is known from German
 Published, Non-Prosecuted Patent Application DE 196 05 017 A1, in which
 the letters or envelopes are fed as a stack, vertically one behind another
 on one edge, and the letters or envelopes are fed laterally away from the
 stack to a separating apparatus. In that case, the letters or envelopes
 are disposed between a spring-mounted curved pressure plate and at least
 one drive roll, as well as a slightly rearwardly inclined guide plate. The
 standing area for the letters or envelopes and the guide plate are
 orthogonal to each other.
 The drive roll has an external contour with at least one projection which
 extends over the length of the roll and is parallel to the axis of
 rotation. The envelope curve of the drive roll projects through an opening
 in the guide plate to such an extent that at least one projection
 protrudes from the opening. As a result of the projecting external
 contour, the stack of letters or envelopes is jogged sufficiently, and the
 frictional and adhesive forces counteracting the transport are overcome.
 The force to be introduced is set through the stroke of the drive roll. As
 a result of the inclination of the guide plate, a stable preferred
 position of the stack of letters or envelopes is achieved. The axis of the
 drive roll in that case is parallel to the guide plate. In that case, the
 problem of separation remains unsolved.
 An input device for an appliance for processing sheets, such as paper money
 or postcards, is also known from German Published, Non-Prosecuted Patent
 Application DE 27 25 947 A1. That device includes at least one transport
 belt and at least one backing roller. The backing roller is driven in the
 opposite direction in relation to the transport belt. The sheets are
 transported from a sheet stacking point to a sheet processing point
 through the use of the transport belt. The backing roller is disposed in
 such a way that there is a gap between the cylindrical outer surface of
 the roller and the outer surface of the transport belt, which allows at
 least one of the sheets to pass.
 That configuration assumes that the transport belt reaches from the region
 of the sheet stacking point as far as the region of the sheet processing
 point. The sheets are transported horizontally on the transport belt and
 thus sheets are continuously pushed against the backing roller. As a
 consequence, however, there is additionally a risk that a jam will build
 up at that point and, as a result, sheets can be damaged, particularly
 since measures for overcoming the adhesion between the letters are
 lacking.
 The relationships are similar in a document separating apparatus according
 to European Patent 0 598 571 B1. As a distinction from the solution
 previously described, belts are used in that case instead of the backing
 rollers.
 Finally, equipment for separating mail items is known from U.S. Pat. No.
 4,615,519, in which vertically oriented letters or envelopes are deposited
 one behind another as a stack of letters or envelopes in a holding area.
 The stack of letters or envelopes is pressed against a pull-off device
 through the use of spring force by a thrust element guided on a carrier.
 The pull-off device includes a drive roll made of rubber disks disposed at
 a distance one above another on a shaft. The rubber disks project partly
 through a guide plate located opposite the holding area and rest on the
 broad side surface of the front letter or envelope of the stack, with the
 guide plate engaging like teeth in the gaps between the rubber disks.
 Due to the spring force, there is an approximately constant force between
 the stack of letters and the drive roll. On one hand, viewed alone, that
 is advantageous. On the other hand, however, it is a problem to introduce
 a force between the drive roll and the front letter or envelope which
 overcomes the adhesion and friction between the latter and the rest of the
 stack and the guide plate, particularly since the adhesive capacity may
 exhibit very great differences because of different weights,
 adhesive-surface size and paper finish. Once the drive roll begins to
 slip, the result is disruption to the automatic operation.
 The letters or envelopes which are pulled off pass from the pull-off device
 to a cylindrical roll and a backing belt located opposite the latter and,
 following that, to the same combination once more. The drive roll and the
 two cylindrical rolls are driven jointly by a motor through a toothed
 belt, which also drives the backing belts through a further toothed belt.
 The stacked configuration of two separating pairs requires a
 correspondingly large amount of space and complication.
 SUMMARY OF THE INVENTION
 It is accordingly an object of the invention to provide an apparatus for
 separating printed media, which overcomes the hereinafore-mentioned
 disadvantages of the heretofore-known devices of this general type, which
 improves properties of use, which permits printed media from a stack to be
 pre-separated and separated reliably and in which engineering outlay and
 space requirements are as low as possible.
 With the foregoing and other objects in view there is provided, in
 accordance with the invention, an apparatus for separating printed media,
 such as letters or envelopes, comprising a pre-separating area and a
 separating area; a spring-mounted curved pressure plate; a guide plate
 having openings formed therein; drive-roll combinations in the
 pre-separating area, the drive-roll combinations including drive rolls
 having different coefficients of friction and cylindrical envelope
 surfaces projecting through the openings for individually laterally
 transporting away stacked printed media disposed between the pressure
 plate and the drive rolls; a drive for the drive-roll combinations;
 separating elements disposed in the separating area; and a sensor disposed
 in the separating area in the vicinity of the separating elements for
 detecting printed media, the sensor linked electrically to the drive for
 the drive-roll combinations for switching the drive to freewheeling upon
 detecting a start of a printed medium and for switching on the drive upon
 detecting an end of a printed medium.
 In accordance with another feature of the invention, the drive for the
 drive-roll combinations is a common, separate drive with freewheeling.
 In accordance with a further feature of the invention, there is provided an
 outlet side, an ejection-roll pair on the outlet side, and a common,
 separate drive for the separating elements and the ejection-roll pair.
 In accordance with an added feature of the invention, the separating
 elements include a drive-belt combination, a driven backing-roller
 combination matched to the drive-belt combination and a sliding-lever
 combination matched to and mounted upstream of the drive-belt combination,
 the sensor disposed in the vicinity of the backing-roller combination.
 In accordance with an additional feature of the invention, the guide plate
 is a rear guide plate; a first of the drive-roll combinations includes a
 common shaft; the drive rolls of the first drive-roll combination include
 a first drive roll and a second drive roll spaced apart one above another
 on the common shaft and each projecting through a respective one of the
 openings in the rear guide plate; the first drive roll is a bottom drive
 roll disposed below the second drive roll and has a length matched to a
 smallest usual printed media format height; the second drive roll is a top
 drive roll shorter than and disposed at distance from the bottom drive
 roll matching a largest usual printed media format height; and the first
 and second drive rolls each have external contours with at least one
 identical projection extending over the length of the drive roll, parallel
 to an axis of rotation and formed of identical material.
 In accordance with yet another feature of the invention, a second of the
 drive-roll combinations includes a common shaft; the drive rolls of the
 second drive-roll combination include a first drive roll and a second
 drive roll spaced apart one above another on the common shaft and each
 projecting through a respective one of the openings in the rear guide
 plate; the first drive roll is a bottom drive roll disposed below the
 second drive roll and has a length matched to a smallest printed media
 format height; the second drive roll is a top drive roll shorter than and
 disposed at distance from the bottom drive roll matching a largest usual
 printed media format height; the first drive roll has a given envelope
 circle and an external contour with at least one projection extending over
 the length of the drive roll and parallel to an axis of rotation; and the
 second drive roll is a smooth spacer roll with an envelope circle
 identical to the given envelope circle.
 In accordance with yet a further feature of the invention, the projections
 in the first drive-roll combination are formed of replaceable moldings of
 identical material with the same given coefficient of friction, preferably
 polyurethane; and the at least one projection on the first drive roll of
 the second drive roll combination is also formed of a replaceable molding,
 preferably of polyurethane, and has a coefficient of friction lower than
 the given coefficient of friction.
 In accordance with yet an added feature of the invention, the second drive
 roll is formed of a relatively hard commercial plastic, such as
 polyoxymethylene.
 In accordance with yet an additional feature of the invention, the
 drive-roll combination s have parallel contours.
 In accordance with again another feature of the invention, the guide plate
 is a rear guide plate, and the drive-belt combination has identical drive
 belts disposed equidistantly one above another and projecting through
 associated openings formed in the rear guide plate.
 In accordance with again a further feature of the invention, the
 backing-roll combination is disposed opposite the drive-belt combination
 and has identical backing rollers disposed equidistantly one above another
 on a rotatable shaft.
 In accordance with again an added feature of the invention, the
 sliding-lever combination includes a two-armed lever.
 In accordance with again an additional feature of the invention, the
 backing-roll combination is disposed opposite the drive-belt combination
 and has identical backing rollers, the backing rollers are disposed
 equidistantly one above another on a rotatable shaft, and the backing
 rollers are disposed opposite gaps between the drive belts and outside the
 gaps; and the sliding-lever combination is disposed opposite the gaps
 between the drive belts, upstream of the backing rollers, and the
 sliding-lever combination includes a two-armed lever with free arms
 pointing in a direction opposite to a printed media transport direction.
 In accordance with still another feature of the invention, there is
 provided a drive-wheel combination having drive wheels, an axially
 parallel deflection-wheel combination having deflection wheels, the drive
 belts disposed equidistantly on the drive wheels and the deflection
 wheels, and, if required, smooth, freewheeling supporting wheels for the
 drive belts disposed between the drive-wheel combination and the
 deflection-wheel combination.
 In accordance with still a further feature of the invention, the drive
 belts are toothed belts and the drive wheels and the deflection wheels are
 toothed wheels; the drive wheels are fixed to a rotatable shaft; and the
 deflection wheels are fastened to a rotatable shaft.
 In accordance with still an added feature of the invention, there is
 provided a dual support lever having free ends, fixed ends and a shaft,
 the shaft with the backing rollers firmly seated thereon being rotatably
 mounted on the free ends, the fixed ends being spring-mounted on the shaft
 of the dual support lever for rotation toward and away from the drive-belt
 combination, and the fixed ends having a tab in a pivoting range of a cam
 for pivoting away and locking the dual support lever; and the
 sliding-lever combination disposed on the shaft with the dual support
 lever and pivoted in the direction of the drive-belt combination by a
 sliding-friction clutch.
 In accordance with still an additional feature of the invention, there is
 provided a locking device having the cam, a lever for manually operating
 the locking device, and a rotatable shaft to which the lever and the cam
 are fixed.
 In accordance with another feature of the invention, the backing-roll
 combination is disposed opposite the drive-belt combination and has
 identical backing rollers disposed equidistantly one above another on a
 rotatable shaft; and including an ejection-roll pair having rotatable
 shafts, a driven ejection roll fixed to one of the rotatable shafts, an
 indirectly driven ejection roll fixed to another of the rotatable shafts,
 a rotatable spring-mounted support lever on which the other rotatable
 shaft is mounted, and a coupling rod articulatingly connecting the
 rotatable spring-mounted support lever to the locking device for achieving
 simultaneous deactivation and locking together with the backing rollers.
 In accordance with a further feature of the invention, the indirectly
 driven ejection roll is shorter, by more than a largest envelope flap
 height of the printed media, than the driven ejection roll, and the
 indirectly driven ejection roll is flush with the driven ejection roll at
 the top.
 In accordance with an added feature of the invention, the sensor is
 disposed directly downstream of the backing-roller combination in a
 printed-medium transporting direction.
 In accordance with an additional feature of the invention, the common drive
 for the drive-roll combinations includes a motor having a motor shaft with
 a first pinion thereon, a rigid shaft, an intermediate wheel rotatable on
 the rigid shaft, and a first toothed belt coupling the first pinion to the
 intermediate wheel; a second freewheeling pinion fixed on the common
 rotatable shaft of the second drive-roll combination, and a second toothed
 belt coupling the intermediate wheel to the second pinion; and a third
 freewheeling pinion firmly fixed to the common rotatable shaft of the
 first drive-roll combination, and a third toothed belt coupling the second
 pinion to the third pinion.
 In accordance with a concomitant feature of the invention, the common drive
 for the drive-belt combination, the backing-roller combination, the
 sliding-lever combination and the ejection roll pair has a second motor
 with a motor shaft, a pinion on the motor shaft, an intermediate wheel
 fixed to the rotatable shaft for the drive wheels, and a toothed belt
 coupling the pinion to the intermediate wheel. A fixed shaft has a drive
 pinion rotatably disposed thereon, and a toothed belt coupling the
 intermediate wheel to the drive pinion. A drive pinion is fixed on the
 rotatable shaft for the dual support lever for the backing-roller
 combination and the sliding-lever combination and a toothed belt couples
 the drive pinions together. A pinion is fixed together with the driven
 ejection roll to a rotatable shaft and a toothed belt couples the drive
 pinion to the pinion. The dual support lever is mounted on the shaft for
 rotation counter to the force of spring. The rotatable shaft is disposed
 on the free ends of the dual support lever, and a pinion and the backing
 rollers are fixed on the rotatable shaft. The sliding-lever combination is
 a two-armed lever mounted on the shaft for rotation counter to the force
 of a spring through the sliding-friction clutch. A transmission pinion is
 fixed to the shaft and coupled through a toothed belt to the pinion. The
 drive wheels are rigidly fixed to the rotatable shaft and connected
 through the associated drive belts to the deflection wheels. A rotatable
 shaft is provided to which the supporting wheels are fixed between the
 drive wheels and the deflection wheels.
 The three rotatable shafts are mounted in a U-shaped supporting frame.
 The apparatus provides drive rolls with jogging properties, separate drives
 in the pre-separating and separating area, a structure of the drive in the
 pre-separating area with freewheeling and of the drive rolls with
 different coefficients of friction and the placement of a sensor for
 detecting printed media in the pre-separated area, with the sensor being
 electrically coupled to the drive in the pre-separating area. As a result,
 no jam upstream of the pre-separating area is produced by the drive rolls
 in the pre-separating area, and in each case only one printed medium is
 transported to the subsequent equipment.
 The subdivision and configuration of the drive-roll combinations in the
 pre-separating area permits reliable processing both of the smallest and
 of the largest usual letter or envelope formats.
 An economical solution and good service properties are achieved due to the
 use of a common drive in the separating and ejection area, and coupling
 the two through functional levers in order to set the operating mode.
 The sliding-lever combination ensures that the last printed medium in a
 stack is reliably gripped. The device is suitable for printed media
 standing on edge one behind the other on one edge as well as disposed
 lying flat on top of each other.
 Other features which are considered as characteristic for the invention are
 set forth in the appended claims.
 Although the invention is illustrated and described herein as embodied in
 an apparatus for separating printed media, it is nevertheless not intended
 to be limited to the details shown, since various modifications and
 structural changes may be made therein without departing from the spirit
 of the invention and within the scope and range of equivalents of the
 claims.
 The construction and method of operation of the invention, however,
 together with additional objects and advantages thereof will be best
 understood from the following description of specific embodiments when
 read in connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring now in detail to the figures of the drawings, which are in
 diagrammatic form for ease of understanding and in which the term "letter"
 or "envelope" is used instead of "printed medium" for brevity, and first,
 particularly, to FIG. 1 thereof, there is seen a letter separating
 apparatus B which is subdivided functionally into a pre-separating area I
 and a separating area II. A rear guide plate 1, which is inclined slightly
 rearward, and a lower guide plate 2, which is orthogonal thereto, are
 provided for the purpose of guiding letters or envelopes A.
 The letters A are disposed vertically as a stack with the edge of their
 envelope flap on the lower guide plate 2, in a force-locking manner
 between a curved pressure plate 21 and the rear guide plate 1. A
 force-locking connection is one which connects two elements together by
 force external to the elements, as opposed to a form-locking connection
 which is provided by the shapes of the elements themselves.
 The curved pressure plate 21 is disposed in such a way that it can be
 pivoted from an operating position into a rest position and vice versa and
 locked. In the operating position illustrated herein, the curved pressure
 plate 21 assumes an orthogonal position in relation to the lower guide
 plate 2, and is disposed in such a way that it can be displaced toward the
 rear guide plate 1 under the influence of a non-illustrated spring and
 away from the latter. In the rest position, the curved pressure plate 21
 assumes a horizontal position in a matching recess in the lower guide
 plate 2 and terminates flush with the latter. In this position, the curved
 pressure plate 21 is locked, as is seen in FIG. 2.
 The letters A are pushed one after another, sliding along on the rear guide
 plate 1, from the pre-separating area I into the separating-area II,
 through the use of first and second drive-roll combinations 3, 4. The
 drive-roll combinations 3, 4 are disposed in such a way that their
 contours are parallel to each other and at the same height in relation to
 the lower guide plate 2. Due to their specific shaping, as will be
 described below, the drive-roll combinations 3, 4 have the effect of
 jogging the stack of letters.
 According to FIG. 2, the first drive-roll combination 3 includes a first
 lower drive roll 31 with projections 311 and a second upper drive roll 32
 with projections 321. The two drive rolls 31, 32 have identical contours
 in plan view and are disposed at a distance from each other on a common
 shaft 33, as is also seen in FIGS. 3 and 4. The drive roll 31 projects
 through an opening 11 and the drive roll 32 projects through an opening 12
 in the rear guide plate 1.
 The second drive-roll combination 4 includes a first lower drive roll 41
 with projections 411 and a second upper drive roll 42 without projections,
 which is constructed as a smooth spacer roll. The two drive rolls 41, 42
 are likewise disposed on a common shaft 43 at a distance from each other.
 An external contour of the second drive roll 42 coincides with an envelope
 circle of the first drive roll 41 in plan view. The drive roll 41 projects
 through an opening 13 and the drive roll 42 projects through an opening 14
 in the rear guide plate 1.
 The length of the lower drive rolls 31, 41 is matched to the height of the
 smallest usual letter formats. The lower drive rolls 31, 41 are longer
 than the upper drive rolls 32, 42. The distance between the lower and
 upper drive rolls 31, 41, 32, 42, is selected in such a way that the
 largest usual letter formats are still gripped in the upper portion.
 The projections 311, 321, 411 extend over the entire length of the roll,
 parallel to the axis of rotation, and are formed of replaceable
 cylindrical moldings, preferably made of polyurethane. The projections 311
 and 321 of the drive rolls 31, 32 of the first drive-roll combination 3
 are made of identical materials, in particular they have the same
 coefficient of friction. The material for the projections 411 of the lower
 drive roll 41 of the second drive-roll combination 4 is selected in such a
 way that the coefficient of friction is lower than that of its precursors.
 The upper drive roll 42, which is constructed as a smooth spacer roll, is
 formed of a relatively hard commercial or engineering plastic, for example
 polyoxymethylene, which is expediently used for the other basic roll
 bodies as well.
 When the drive-roll combinations 3, 4 rotate, firstly the stack of letters
 is jogged by the projections 311, 321, 411 of the drive rolls 31, 32, 41,
 and secondly the letters A are individually pushed away laterally in
 accordance with the coefficient of friction. Since the projections 311,
 321 have a greater coefficient of friction than those following, the
 initial tempo of the lateral movement is also determined by the former.
 The projections 411 on the lower drive roll 41 only have a supporting
 effect for the movement, and the upper drive roll 42 serves primarily to
 reduce friction and maintain spacing.
 In the separating area II, an individual letter A is led, through the use
 of a drive-belt combination 6 and a driven backing-roller combination 7
 matched to the latter, as well as a sliding-lever combination 77 which is
 mounted upstream in the opposite direction to the letter-transporting
 direction, past a sensor 10 for letter detection, to an ejection-roll pair
 9, as is also seen in FIGS. 3, 5, 6A and 6B. The sensor 10 is disposed
 directly downstream of the backing-roller combination 7 in the
 printed-medium transport direction.
 When the start of a letter is detected by the sensor 10, the latter
 produces a signal which is used to change over the drive-roll combinations
 3, 4 from driving to idling. At the end of a letter, the sensor 10
 correspondingly produces a signal to change over from idling to driving.
 In this way, the next letter A is pushed out of the feeding or
 pre-separating area I into the separating area II only when the current
 letter A has left the latter. This rules out the formation of a jam.
 The drive-belt combination 6 has three identical drive belts 61, 62, 63
 shown in FIG. 5, which are disposed equidistantly above one another and
 project through associated openings 15 in the rear guide plate 1 seen in
 FIG. 2.
 The backing-roller combination 7 has three backing rollers 71, 72, 73 as a
 counterpart to the drive-belt combination 6, which are similarly disposed
 equidistantly on a fourth shaft 75 as is seen in FIG. 6A. The top backing
 roller 71 is located above the level of the top drive belt 61, and the
 remaining two backing rollers 72, 73 are located opposite associated gaps
 between the drive belts 61, 62, 63 as is seen in FIG. 2.
 The shaft 75 with the backing rollers 71, 72, 73 firmly seated thereon is
 rotatably mounted on free ends 762 of an appropriately shaped dual support
 lever 76. The dual support lever 76 is in turn spring-rotatably mounted at
 its other ends 763 on a driven fifth shaft 761, as is seen in FIG. 6A. In
 this way, the dual support lever 76 with its free ends 762 can be pivoted
 toward the drive-belt combination 6 and away from the latter again.
 In addition, the ends 763 of the dual support lever 76, which are on
 mounted on the shaft 761, are provided with a tab 7631 that is located in
 a pivoting range of a cam 781. The cam 781 is a component of a locking
 device 78, which can be actuated manually through the use of a lever 782.
 The cam 781, together with the lever 782, is fixed to a sixth rotatable
 shaft 783. The locking device 78 is used to pivot out and lock the dual
 support lever 76 in the pivoted-out state.
 The ejection roll pair 9 includes a driven ejection roll 91 and an
 indirectly driven ejection roll 92. The driven ejection roll 91 is
 fastened to one seventh rotatable shaft 911 behind the rear guide plate 1
 and its periphery projects through an associated opening 16 in the guide
 plate 1, as is seen in FIGS. 2, 3 and 4.
 The indirectly driven ejection roll 92 is likewise fastened to another
 seventh rotatable shaft 921, which is in turn mounted on a rotatable,
 spring-mounted support lever 93. The support lever 93 is mounted on a
 shaft 931 and is connected in an articulated manner, through a coupling
 rod 784, to the shaft 783 of the locking device 78. This achieves
 simultaneous deactivation and locking together with the backing rollers
 71, 72, 73 when the lever 782 is operated appropriately, as is seen in
 FIGS. 3 and 4.
 The indirectly driven ejection roll 92 is shorter, by more than the
 greatest height of the envelope flaps of the letters A, than the driven
 ejection roll 91 and is disposed to be flush with the latter at the top.
 As a result, premature closure of the letters by the ejection-roll pair 9,
 with the risk of forming bulges on the envelope flaps, is avoided.
 In the plan view according to FIG. 3, it is possible to see a first motor
 54 for driving the drive-roll combinations 3, 4 and a second motor 84 for
 driving the drive-belt combination 6, the backing-roller combination 7 as
 well as the ejection-roll pair 9 and the sliding-lever combination 77.
 FIG. 4 illustrates connections between the motors 54, 84 and the drive
 devices for the letters A. For this purpose, a perspective view from below
 has been selected and rotated through 90.degree. to the rear.
 In a common drive 5 for the drive-roll combinations 3, 4, a first pinion
 541 on a motor shaft of the first motor 54 is coupled, through a toothed
 belt 57, to an intermediate wheel 56 which is rotatably disposed on a
 rigid shaft 561. The intermediate wheel 56 is further connected, through a
 toothed belt 55, to a second pinion 52 which is disposed to be fixed on
 the common, rotatable shaft 43 of the second drive-roll combination 4. The
 pinion 52 is connected, through a toothed belt 53, to a third pinion 51,
 which is likewise disposed to be fixed on the common, rotatable shaft 33
 of the first drive-roll combination 3.
 The pinion 51 and the pinion 52 are equipped with a freewheel, in such a
 way that rotation of the drive-roll combinations 3, 4 is still possible
 when the motor 54 is switched off, if friction between the letter A and
 the drive rolls 31, 32, 41, 42 is sufficient. This case could arise when a
 letter has just been gripped by the drive-belt combination 6 and the
 backing-roller combination 7 and is still resting on at least one roll
 combination 3, 4. The next letter A can only be moved when the motor 54 is
 switched on again.
 The second motor 84 is provided for a common drive 8 of the drive-belt
 combination 6, the backing-roller combination 7, the sliding-lever
 combination 77 and the driven ejection roll 91. The second motor 84 has a
 motor shaft on which a pinion 841 is seated. The pinion 841 is coupled,
 through a toothed belt 871, to an intermediate wheel 87. The intermediate
 wheel 87 and a drive-wheel combination 64 are disposed to be fixed on a
 first rotatable shaft 644, as is seen in FIG. 5. The intermediate wheel 87
 is further connected, through a toothed belt 831, to a drive pinion 83,
 which is rotatably disposed on a fixed shaft 832.
 In addition, the drive pinion 83 is firstly coupled, through a toothed belt
 86, to a drive pinion 82 and is secondly coupled, through a toothed belt
 89, to a pinion 88. The drive pinion 82 is disposed to be fixed on a
 rotatable shaft 761, together with the backing-roller combination 7, as is
 also seen in FIGS. 6A and 6B. The pinion 88 is disposed to be fixed on the
 rotatable shaft 911, together with the driven ejection roll 91.
 According to FIG. 5, the drive-belt combination 6 has the three drive belts
 61, 62, 63 as well as a U-shaped support frame 67, in which the first
 shaft 644, a second shaft 654 and a third shaft 68 are rotatably mounted.
 Drive wheels 641, 642, 643 assigned to the drive belts 61, 62, 63 are
 fastened to the shaft 644. Corresponding deflection wheels 651, 652, 653
 are fastened to the shaft 654. Three supporting wheels 66, which are
 intended to ensure uniform contact between the drive belts 61, 62, 63 and
 the letter A, are correspondingly fixed to the shaft 68. All of the
 above-mentioned wheels are toothed, as counterparts to the drive belts 61,
 62, 63.
 According to FIGS. 6A and 6B, the dual support lever 76 for the backing
 rollers 71, 72, 73 is rotatably mounted on the shaft 761 in such a way
 that it can rotate counter to the force of a spring 79. In addition, the
 sliding-lever combination 77, in the form of a two-armed lever, is mounted
 on the shaft 761 and biased counter to a spring 771 through a
 sliding-friction clutch. Finally, a transmission pinion 821 is further
 fixed to the shaft 761 and is driven by the drive pinion 82 through the
 shaft 761. The rotational movement of the transmission pinion 821 is
 transmitted, through a toothed belt 85, to a pinion 81 which is fixed to
 the rotatable shaft 75, together with the backing rollers 71, 72, 73. The
 shaft 75 is rotatably mounted on the free ends 762 of the dual support
 lever 76.
 As can be easily seen, only a corresponding rotation of the above-described
 device is necessary for the flat printing media transport.