Abstract:
A modular placement device for a feed station of a mail processing apparatus, wherein the feed station includes an ejection roller, has a housing that is separate for the modular placement device located upstream, in terms of the mail flow, of the feed station. The housing has a cavity therein to receive a stack of mail items, and a pressure element mounted so as to be pivotable and so as to be plugged into the cavity. The pressure element exerts a pressure force on the stack of mail items in the cavity, with a bottommost item of mail being pressed against the ejection roller so that the bottommost item of mail is propelled in the mail flow direction. The weight loss of the stack due to removal of the bottommost item of mail therefrom is counteracted by the pressure element.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention concerns a modular placement device of a feed station. Such a feed station is an apparatus within a mail processing system that is equipped to feed mail pieces or flat goods to a printing apparatus. The invention is designed to simplify the feed station that is arranged upstream (in terms of the mail flow) of a peripheral apparatus (enveloping station, moistening/closing station, dynamic scale) or a printing apparatus. The modular placement device is required upstream (in terms of the mail flow) of a feed station without a placement region, and is suitable for use in a mail franking station in connection with a franking machine arranged downstream (in terms of the mail flow) of the feed station. 
     2. Description of the Prior Art 
     A system to frank mail shipments is known from DE 27 17 721. A stack of mail pieces that are stacked atop one another in an arbitrary order is placed in a magazine in the placement region. The stack is placed to the rear of a guide wall of the feed station, such that the edges of the mail pieces lie flush with the front side and rear side of the stack. The stack is situated at the start of a transport path and presses the lowermost mail piece against a feed deck. The lowermost mail piece forms the start of the stack and should first be isolated in the transport direction. To assist with the isolation, a wedge is applied to the stack from the left (upstream side). The surface of the wedge forms a sloped plane with an angle of inclination relative to the horizontal plane of the feed deck. A downhill slope force (grade) that is dependent on the cosine of the angle of inclination and the weight of the stack acts in the transport direction along the sloped plane. It is disadvantageous that the angle of inclination must be large enough and the letter length must be adjusted accordingly, or that the downhill slope force must be set dependent on the length of the mail piece. This hinders the feed for what is known as mixed mail, i.e. a mail stack with mail pieces of respectively different formats and thicknesses. An interference-free effect of the wedge also requires a defined minimum weight of the stack or of the mail pieces as well as a certain rigidity of the mail pieces so that their curvature is slight. Given an interference-free effect of the wedge at the right side of the stack, the edge of the lowermost mail piece projects the farthest, is thus engaged first and is pulled from the stack. 
     A device to isolate flat articles of different thickness and size from a stack is known from the German Utility Model DE 29823055 U1. The device is essentially subdivided into a placement region and into an ejection region, which follows the placement region to the right in the transport direction. Adjoining the placement region to the left is a wedge-shaped stack receptacle, and to the right a stack stop. A removal device in the ejection region has a height-adjustable retaining means and ejection rollers. A stack of flat goods (mail pieces) to be printed presses the lowermost mail piece in the placement region at the start of the transport path against the feed deck. If the stack is inclined and high enough, the contact pressure force exerted by the weight of the upper mail pieces on the lowermost mail piece contributes to an isolation (separation) of the lowermost mail piece. Interruptions in the isolation can occur, however, if the contact pressure is too high or if, in spite of a suitable stack height, the mail piece is only insufficiently pressed against the feed deck. Such disruption of the passage of the flat goods should be avoided or be simple to remedy. 
     In the German Patent DE 196 05 017 C2, an arrangement to pre-isolate print media is disclosed that breaks up the stack by means of projections at a drive roller its rotation. Since the arrangement also has a spring-biased pressure hoop that presses the stack of mail pieces against a guide plate, due to the spring pressure between the mail pieces a stiction (static friction) occurs that counteracts relative motion between the mail pieces. Upon reaching the maximum retention force, the relative motion is prevented. This retention forces:
 
 F   Rmax =μ H   ·F   (1)
 
with an elastic force F and with a coefficient of friction μ H  that depends on the material properties or the surface condition of the mail pieces. The elastic force of a spring is proportional to its deflection. The stiction therefore increases with the height of the stack, i.e. the more that the pressure clip is deflected, thus is spaced from the guide plate. The maximum retention force is achieved even before the pressure clip is maximally deflected. By loosening the stack, the stiction is temporarily overcome so that the individual mail pieces can easily be drawn from the stack. Loosening of the stack is superfluous given a low stack height of mail pieces of the same format. The cost for an actively operating device, which requires an actuator for a pre-isolation via drive rollers, is disadvantageous. However, a pressing on the stack is required if mixed mail, or even bulky or twisted mail pieces are included in the stack. The non-uniform pressure force is disadvantageous during the processing of the stack by the isolation of the mail pieces, in which case the pressure force increases with the stack height.
 
     In a franking system with the Ultimail franking machine that is commercially available from Francotyp-Postalia, an automatic feed station is used for stacks of mail pieces lying on their back sides. The recommended maximum stack height is 50 mm. Given a higher stack level, a stiction can occur between the mail pieces, which in individual cases prevents an isolation. 30 to 40 mail pieces per stack can be anticipated. For example, the mail pieces are enveloped letters with the C6 envelope format in terms of length and with an average weight of 20 g per piece. A total weight of 600 g to 800 g therefore results for a stack with maximum stack height. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a modular placement device of a feed station that acts passively. The placement device should exert a pressure force on the stack at the transition to the ejection region of the feed station, which pressure force acts independently of the length of the item (mail piece) to be isolated, with the pressure force decreasing with growing stack height. The feed station should also enable a manual placement. 
     The modular placement device in accordance with the invention is stationed upstream (in terms of the mail flow) of the feed station in order to place a stack of items to be isolated at the feed station, which feed station isolates the items and transports them further in a transport direction. For this purpose, in a known manner the feed station has a draw device in the ejection region and a retention device for the stack. The draw device has at least one driven ejection roller that has a rotation axis oriented orthogonally to the transport direction. A stack of flat items to be printed presses the lowermost item in the placement region at the start of the transport path against a feed deck of the modular placement device. A higher weight of the stack is normally assumed in the case of a high stack compared to a lower stack. Rollers that reduce the friction resistance are provided in the feed deck. The modular placement device has a separate housing and a pressure element, mounted so that it can pivot, that can be inserted into a cavity of the housing near the rear wall of the modular placement device. This pressure element exerts a pressure force on the stack at the transition to the ejection region; causing the lowermost item to be pressed with such a force against at least one driven ejection roller of the feed station so that a propulsion of the item is achieved; with the weight loss of the stack due to the removal of the items for isolation of the stack being counteracted. In the case of similar items—for example mail pieces of the same format—the aforementioned force can be in the range from a minimum height of the stack to a maximum height of the stack, nearly independent of the stack height, or it can at least be within a predetermined force range. Defined conditions thereby exist for the removal of the lowermost item from the stack. The effect of the weight of the stack (this weight being reduced upon the removal) on the at least one driven ejection roller is at least partially compensated by the pressure element because its pressure force increases with decreasing stack height. Virtually no disruptions in the processing of the stack occur in a range between a maximum height of the stack and a minimum height of the stack, the flat items (mail pieces) of which that are to be isolated have an average weight. A stack with flat items to be isolated can now be processed without interruption, and therefore quickly. 
     The pressure element has a pendulum that can be attached to a pendulum support and a bearing shell that is designed so that it can be plugged into a cavity of the housing near the rear wall of the modular placement device. The pendulum support is mounted so that it can pivot on the bearing shell. The pendulum of the pressure element has two pendulum arms that are arranged at an angle δ&lt;180° (advantageously in a range from 110° to 140°) relative to one another. The aforementioned angle is an internal angle at the lower pendulum part. One of the two pendulum arms is longer than the other and is designed to push the stack down. Both pendulum arms are connected with another by a middle part and are antiparallel to one another. The pendulum is designed as a two-part pendulum body with a lower pendulum part and an upper pendulum part, so that it can be assembled. The possibility exists to accommodate a material with a high specific weight in the pendulum body. The pendulum can be attached to or permanently connected with the pendulum support at the lower pendulum part, on the side of the short pendulum arm. 
     The feed deck of the modular placement device can be placed on a ramp. Moreover, to align the stack the modular placement device has an extendable slider mounted on the feed deck at the front side of the housing. This slider can subsequently be pressed against the stack, and a guide plate opposite the slider, the guide plate being permanently connected with the housing. 
     Given a manual placement of individual goods (mail pieces) at the feed station, no placement device is required. The aforementioned modular placement device can therefore be designed so as to be coupled and uncoupled from the feed station. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a feed station with a modular placement device in accordance with the invention. 
         FIG. 2  shows an angle lever used in accordance with the invention. 
         FIG. 3   a  shows a small stack upon isolation in accordance with the invention. 
         FIG. 3   b  shows a large stack upon isolation in accordance with the invention. 
         FIG. 4   a  is a plan view of a pendulum in accordance with the invention. 
         FIG. 4   b  is a view of the pressure element from the front, in accordance with the invention. 
         FIG. 4   c  is a view of the pressure element and a bearing shell from the left, in accordance with the invention. 
         FIG. 5  is a plan view of the housing of the placement device without pendulum, in accordance with the invention. 
         FIG. 6   a  is a front view of the placement device with pendulum but without slider, in accordance with the invention. 
         FIG. 6   b  is a front view of the placement device with pendulum and a feed deck set up as a ramp, without slider, in accordance with the invention. 
         FIG. 6   c  is a front view of the placement device with slider in accordance with the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a perspective view of a feed station with a modular placement device. The modular placement device  1  has a housing  10  with a feed deck  11  and a placement element  14 . The placement element  14  is realized as a pendulum that is angled towards a stack (not shown) lying on the feed deck  11  and thus can exert a pressure on said stack. The rollers  111  in the feed deck  11  reduce the friction of the goods (mail pieces) with the feed deck. A slider  16  mounted so as to be able to slide on the feed deck  11  has a first slider wall part  161  and a second slider wall part  162  and a shaft  160  via which the slider wall part  161  can be screwed on opposite the slider wall part  161  when the feed deck is set up at a ramp ( FIG. 6   b ). With the slider a stack can be manually pressed with its lateral edges onto the guide plate of the housing. The housing comprises an upper shell and a lower shell that is covered by the upper shell. A slit-shaped opening is molded in the upper shell, which opening is covered by the slider. The slider  16  is mounted on the feed deck together with a damping mechanism (not shown). Some of the goods to be isolated can be buckled, bent or compressed by the pressure, which is however gradually, automatically reversed after the manual operation via the damping mechanism arranged within the placement device. The modular placement device also has a coupling mechanism and an additional, passively acting mechanism (not shown) under the feed deck in order to arrest the feed deck (which can be set up at a ramp) at a desired angle or to release it again (not visible). 
     The feed station  2  follows the modular placement device  1  in the transport direction (direction x). The feed deck  21  of the feed station  2  has a width (extending in the y-direction from the front to a rear stop) and lies parallel to the x/y-plane, which forms a base surface. The superstructures of the feed station  2  extends perpendicularly to the base surface, i.e. in the z-direction. The mail piece width is determined by the widest mail piece and the height of the superstructures is determined by the maximum height of a mail piece that can presently still be isolated and transported. A container for sealing fluid, a moistener for flaps of envelopes and a closing device for envelopes can be included in the superstructures. The height of the feed deck  21  above the base surface is determined by the height of a transport device (not shown) for mail pieces that is installed in the feed station. 
       FIG. 2  shows a basic illustration of an angle lever that can be constructed from two similar triangles with the points A 1 , C 1 , D and D, C 1 , B 1  and has a pivot D. The distance A 1 -D thereby forms a lever arm with the radius r, and the distance B 1 -D forms a lever arm with radius d around the pivot D. The distance A 1 -C 1  has a length a and is realized as a shorter pendulum arm  141  of a pendulum  140 . The distance B 1 -C 1  has a length b and is realized as a longer pendulum arm  142  of the pendulum  140 . The distance C 1 -D has a length c and is realized as a pendulum support  144  that adjoins the internal angle δ of the pendulum  140  and reaches at least to the pivot D. The pivot D lies at a vertical distance above the feed deck  11  on a rotation axis that proceeds in a bearing or a bearing shell  12 . A rotation axis  13  that is situated orthogonal to a vertical (z-direction) and orthogonal to a horizontal (transport direction x) travels through the pivot D. The angle (designated with a point) between the sides r and c or, respectively, c and b of the triangle can be a right angle or can be greater than 90°, up to approximately 110°. The sides a and c or, respectively, d and b of the triangle enclose an acute angle γ, for example γ=30°. After a leftward rotation of the pendulum  140  around the pivot D, the lever arm with the radius d reaches an angle β 1  (for example β 1 =20°) while the lever arm with the radius r reaches an angle α 1  (for example α 1 =25°). Weights (not shown) that exert respective forces F A1  and F B1  on the respective lever arms in the direction of gravity act at the ends A 1  and B 1  of the lever arms. A plot of the lever arm r on the horizontal yields a length l A1 =r·cos α 1  that is effective for the gravitational force is shown in the upper part of  FIG. 2 . A plot of the lever arm on the horizontal yields a length l B1 =d·cos β 1  that is effective for the gravitational force and is likewise shown in the upper part of  FIG. 2 . If both arms of the pendulum  14  are at equilibrium, Hooke&#39;s Law applies:
 
 F   A1   ·l   A1   =F   B1   ·l   B1   (2)
 
     Beyond the equilibrium, the pendulum tips in the direction of the arrow drawn with a dash-dot line. After a rightward rotation of the pendulum  140  around the pivot D, the lever arm with the radius d reaches an angle β 2  (for example β 2 =−20°) while the lever arm with the radius r reaches an angle α 2  (for example α 2 =50°). The weights (not shown) again act at the ends A 2  and B 2  of the lever arms r and d. A plot of the lever arm r on the horizontal yields a length l A2 =r·cos α2 that is effective for the gravitational force is shown in the upper part of  FIG. 2 . A plot of the lever arm r on the horizontal yields a length l B2 =d·cos β 2  that is effective for the gravitational force is likewise shown in the upper part of  FIG. 2 . 
     The effective length l B2 =d·cos β 2  is equal to the effective length l B1 =d·cos β 1 . Although the weights have not changed, however, equilibrium no longer exists because the effective lengths have changed at the side of the pendulum arm  141 , such that now:
 
 r ·cos α2 =l   A2   &lt;l   A1   =r ·cos α1  (3)
 
     A small stack  32  upon isolation is presented in principle in  FIG. 3   a . The stack  32  with a height h 2  lies on rollers  111  of the feed deck  11  and on an ejection roller  22 . The lowermost mail piece is pulled via a rotation of the driven ejection roller  22  around the rotation axis  21 . The rotation direction is identified with a black arrow, and the ejection direction is identified with a white arrow. The longer pendulum arm (not shown) presses on the stack  32  with a weight G 2 . The sum of the weight G 2  and the weight of the stack add up to a force F 2 . The force F 2  acts on the ejection roller  22 . 
     A large stack  31  upon isolation is presented in principle in  FIG. 3   b . If the weight of the longer pendulum arm is greater, such that both arms of the pendulum  140  are not in equilibrium, a weight G 1  likewise acts on a stack  31  that rests on the feed deck and thus on the ejection roller. The sum of the weight G 2  and the weight of the stack add to a force F 1 . The force F 1  acts on the ejection roller, but with the difference that the weight G 1  is smaller than the weight G 2 , and that the stack  31  with the height h 1  is higher than the height h 2  of the stack  32 . 
       FIG. 4   a  shows a plan view on a pendulum  140  with the shorter lever arm  141  of the length a and with the longer pendulum arm  142  of the length b, as well as with a middle part  143  of the pendulum. The shorter pendulum arm  141  has the width u and the longer pendulum arm  141  has the width v. Both pendulum arms are situated antiparallel to one another and are separated in width by the middle part  143  of the pendulum, wherein the distance w is smaller than the width u or the width v. 
       FIG. 4   b  shows a view of the pressure element from the front. The surface of the pendulum support  144  lies parallel to the x/z-plane and, to the left of the center, has a circular opening  1440  around a pivot  13 . A catch  145  is molded toward the bottom on the pendulum support  144 . The pendulum arm  142  strikes the pendulum arm  141  at an angle at an impact point. A diagonal between the pivot  13  and the impact point has a length c. The shorter pendulum arm  141  of length a lies parallel to the x-direction, and the longer pendulum arm  142  of length b lies at an angle to the x-direction. 
     A view from the left of the pressure element and of a bearing shell is shown in  FIG. 4   c , wherein the bearing shell  12  is designed to bear the pendulum support  144  and is provided to be plugged into the bearing shell  12  in a shaft-shaped cavity (not shown) of the housing of the placement device. The bearing shell  12  has bearing pins  121 ,  122  molded on both sides so as to be elastic to support the pendulum support, and has elastically formed detents  123 ,  123  for insertion into the shaft-shaped cavity. The pendulum support  144  is molded on the lower part of the pendulum arm  141 . The pendulum arm  142  is molded at an angle on the pendulum arm  141 . The pendulum support  144  has circular openings  1440  with a diameter correspondingly matched to the diameter of the bearing pins  121 ,  122  and a catch  145 . The pendulum support  144  is mounted on the bearing shell  12  so that the bearing pins  121 ,  122  and openings  1440  lie on a rotation axis  130 . 
       FIG. 5  shows a plan view of the top shell  101  of the housing of the placement device  1  without the pendulum. In its upper shell  101  the housing has a shaft-shaped cavity  15  extending in the x-direction, near the right side wall and the rear wall. A guide wall  17  is provided parallel to the rear wall of the upper housing shell  101 , the distance of which guide wall  17  from the rear wall is co-determined corresponding to the width (extending in the y-direction) of the shaft-shaped cavity  15 . A feed deck  11  is arranged at a distance from a base plate, which feed deck  11  includes rollers  111  in order to reduce the friction resistance caused by stiction. A slider  16  arranged so that it can be displaced in the y-direction on the feed deck  11  has a slider plate  163  that is molded on the slider wall part  161 . This allows a stack to be displaced up to a stop on the guide wall  17 . The front view of the placement device  1  that is shown in  FIG. 6   a  includes the pendulum  140  moved away from the operating position and the upper housing shell  101 , which—together with the feed deck  11 —is placed back in the horizontal plane. The slider has been removed in order to enable a view of the guide wall  17  at the housing  10 . A slit-shaped opening  18  on the front side is provided for the insertion of the slider. The guide wall  17  is drawn in section in order to enable a view of the bearing shell  12  mounted in the housing. The cavity is drawn in section in order to show the shaft wall  151 , the pendulum support  144  inserted into the bearing shell  12 , and the pivot  13  of the pivot  140 . The pendulum rotation to the left is stopped in that the catch of the pendulum support  144  stops at the inner bearing shell wall. This pendulum setting stably persists, which is advantageously usable for insertion of a stack into the placement device. 
     A front view of the placement device with a pendulum  140  in the operating position and a feed deck  11  set up as a ramp is shown in  FIG. 6   b . The feed deck  11  can be set up together with the upper housing shell  101  up to an angle of ψ max =10°. The pivot  103  of the upper housing shell  101  lies on a horizontal line H on the right size. The lower housing shell  102  lies below the horizontal line H. A stack  3  of mail pieces lies on the feed deck. The weight G of the stack  3  or mail piece acts near the center of gravity and—due to the gravitation—orthogonal to the ramp. The value of a normal force component F N  and a downhill slope force component F K  is dependent on the weight G of the stack  3  or mail piece, wherein said normal force component F N  is situated orthogonal to the surface of the ramp, and wherein said downhill slope force component F K  lies on the surface of the ramp and is directed downward in terms of the slope. The friction force F R  increases with the normal force component F N . The downhill slope force component is usable to propel the goods to be isolated. Given an increasing slope—i.e. an angle ψ of the surface of the ramp relative to the horizontal—the normal force component F N  decreases and the downhill slope force component F K  increases, wherein the formulas apply:
 
 F   N   =G· sin(90°−ψ)  (4)
 
 F   K   =G ·cos(90°−ψ)  (5)
 
     The pendulum  140  presses on the stack  3  with a force F B  with the end of the longer pendulum arm in the transition region to the feed station. 
       FIG. 6   c  shows a front view of the placement device with slider  16  and with a pendulum  140  that is moved away from the stack covered by the slider, as well as with a coupling mechanism  19  to couple the placement device with a feed station (not shown) that follows downstream (in terms of the flow) in a franking machine. 
     Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contributions to the art.