Patent Abstract:
A transfer device for mail items with a transfer unit which has an ejection point for transferring individualized mail items to an item carrier is provided. Further, the transfer device includes a transport device for transporting the mail items to the ejection point in a direction of transport. The transport device includes two belts for holding the mail items on both sides and for transporting the mail items and further has means for adapting a space between the belts to the thickness of a mail item. The means for adapting is a belt tilt means which is pivotal about an axis of rotation, the pivotal movement pivoting one of the belts and therefore a distance between the belts is variable.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuing application of U.S. patent application Ser. No. 12/507,380 filed Jul. 22, 2009, which claims priority of German patent application no. 10 2008 034 179.7 DE filed Jul. 22, 2008. All of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention relates to a transfer device for mail items, having a transfer unit which has an ejection point for transferring the individualized mail items to an item carrier and a transport device for transporting the mail items to the ejection point in a direction of transport, which includes two belts, for holding the mail items on both sides and transporting them, and a means for adapting the spacing between the belts to the thickness of a mail item. 
       BACKGROUND OF INVENTION 
       [0003]    Mail items, such as letters, large letters, postcards, wrapped journals, flat packets and the like, are sorted by their address in mail centers or large post offices in very large numbers and are deposited in a plurality of containers. For this, DE 10 2005 059 601 B3 discloses a sorting installation in which the mail items are transported, standing upright on their longitudinal edge, in a direction of transport to a ring of pigeonholes moving past transversely to the direction of transport. The mail items are shot one after the other into the pigeonholes, which move past horizontally, with the high cycle rate and the high density of the stream of items supplied having the effect that a very small time window is available each time for shooting a mail item into a pigeonhole as it moves past. 
         [0004]    To increase the size of this time window somewhat, the stream of items is transported to the pigeonhole ring in a loading arm, it being possible for the ejection point thereof at which the mail items are transferred from the loading aim to the individual pigeonholes to be entrained horizontally with the moving pigeonholes. Once a mail item has been shot into a pigeonhole the loading arm is retracted and the ejection point aligned with a succeeding pigeonhole. 
       SUMMARY OF INVENTION 
       [0005]    It is an object of the present invention to provide a transfer device by means of which mail items of differing thickness can be reliably transferred to moving pigeonholes of an item carrier. 
         [0006]    This object is achieved by a transfer device of the type mentioned in the introduction, in which the means for adapting the spacing between the belts is a belt tilt means which is pivotal about an axis of rotation and whereof the pivotal movement pivots one of the belts and so makes its distance from the other belt variable. It is a simple matter to press in controlled manner against the belt tilt means, this controlled contact pressure being a crucial parameter for achieving satisfactory quality of transport of the mail items through the transport device with at most a low level of slip. 
         [0007]    Adapting the spacing between the belts to the thickness of a mail item which is currently being transported may be achieved by adjusting the pivot angle from the outside, for example using a processing means, or a self-adjustment mechanism of the belt tilt means. The belt tilt means may have a deflection roller, preferably directly at the ejection point, which deflects the pivotal belt, in particular at the outermost position of the belt—that is to say where the belt is guided the furthest toward the item carrier. The deflection roller may, together with the deflected belt, be pivotal about the axis of rotation of the belt tilt means arranged outside the deflection roller. The ejection point may be a location on the transfer unit at which the mail items leave the transfer unit, for example by way of a chute or to guided transfer to the adjacent item carrier. The belts are preferably motorized endless belts. For further guidance of the mail items, the transfer unit may have an additional underlying belt on which the mail items stand on their longitudinal edge as they are transported by the two belts. The mail items may be mailings of all kinds. The item carrier may take the form of a pigeonhole ring with revolving pigeonholes. 
         [0008]    So that the ejection point can be entrained in a manner adapted to movement of the item carrier, the transfer unit advantageously includes an entraining drive which is controlled by a processing means. The ejection point may be entrained, temporarily synchronized with a movement of the item carrier which is in particular transverse in relation to the direction of transport, where “transverse” is understood below to mean an angle of between 70° and  110°. After a synchronized entrainment of this kind, the transfer unit can be pivoted back, with the high cycle rate of the transported mail items making it possible for a high moment of acceleration to act on the transfer unit and hence also on the entrained belt tilt means.    
         [0009]    The transport device should be capable of transporting mail items of the greatest variety of thicknesses in a manner at least substantially free of slip even under considerable lateral acceleration, in particular of up to 6 g. To this end, in a preferred embodiment of the invention, the belt tilt means includes a compensation means which, in the event of acceleration of the ejection point both in the direction of and in opposition to a movement of the item carrier, acts to counter any closing or opening of the belts caused by inertia. By compensating fully or at least to a large extent for any movement of the belt tilt means and hence one of the belts caused by inertia, it is possible to prevent the belts from closing or opening—that is to say moving toward one another or away from one another—if the transfer unit is forcefully accelerated. Depending on the construction of the compensation means or transfer unit, any relationship between closing and opening and the direction of acceleration is possible. 
         [0010]    The compensation means may be electronically controlled or self-regulating, for example with the aid of a sensor. A particularly simple and reliable means is a counterweight which acts to counter any movement of inertia by the other components of the belt tilt means as a result of its own inertia. The counterweight may be a counterweight to the mass of the belt tilt means on the ejection side, and be mounted opposite the ejection point in relation to the axis of rotation. Advantageously, it is connected to the ejection point with the aid of a rigid aim, with the result that dynamic movements are kept small. 
         [0011]    The belt tilt means is advantageously arranged with its axis of rotation such that any movement of the belt tilt means caused by acceleration in the direction of acceleration of the ejection point is fully or partly compensated in the direction transverse to the direction of transport. The transfer unit, which may take the faun of a loading arm, may be moved transverse to the direction of transport without any disadvantage, as a result of which a considerable degree of freedom of movement in relation to the item carrier can be achieved. 
         [0012]    Particularly good compensation of movements of the belt tilt means caused by acceleration can be achieved if the center of gravity of the belt tilt means lies on the axis of rotation. 
         [0013]    To keep transport of a mail item between the belts as free of slip as possible, the two belts have to be pressed toward one another and toward the mail item by a contact pressure force so that the mail item is held securely between them. This contact pressure force may be applied by one or more spring elements. The occurrence of wear associated with the contact pressure force may be countered if the form of the belt run of the belt of the belt tilt means gives rise to the contact pressure force on the belt tilt means. The belt run of the belt of the belt tilt means is advantageously formed such that the resultants of the force of the belt gear form a force component which imparts a moment of contact pressure to the belt tilt means. To this end, a tension force of one of the belts, in particular the belt associated with the belt tilt means, may exert a closing force on the belt tilt means. An additional contact pressure on the tilt means may be applied by a spring construction. 
         [0014]    Rarely, and for a vast variety of reasons, it may occur that proper transfer of a mail item from the transport device to the item carrier does not proceed smoothly and the mail item remains stuck in the region of the ejection point, between the item carrier and the transfer unit. As a result of continued movement by the item carrier, which it may not be possible to stop abruptly because of its weight, the mail item is pulled further and may possibly pull the entire transfer unit with it, with the result that there is a risk of damage to the mail item and the transfer unit. To prevent this, the transfer device advantageously includes a release means for opening the belt tilt means wide enough for a mail item between the belts to be released at the ejection point. The mail item may be transported further by the item carrier without the transfer unit being pulled with it. When the belt tilt means is opened at the ejection point, the belts are advantageously spaced from one another by at least 10 cm. 
         [0015]    When the belt tilt means is opened, the contact pressure force provided for holding the mail item in the transport device has to be overcome. So that this act of overcoming the pressure is not left to the mail item, the release means advantageously has a gear for opening the belt tilt means to such an extent that a mail item is fully released in a region extending from the ejection point by at least 30 cm in opposition to the direction of transport, in a direction of acceleration of the ejection point. The direction of acceleration is advantageously the direction of transport of the item carrier. The transfer unit and the ejection point thereof may be accelerated, for example in order to position the ejection point at a succeeding pigeonhole of the item carrier, without a mail item that is jammed in the item carrier striking against the belt tilt means. 
         [0016]    Advantageously, the opening is wide enough for it to be possible to move the mail item by a distance of at least 50 cm in the direction of acceleration without coming into contact with the belt tilt means. 
         [0017]    Advantageously, the release means includes a motorized drive for opening the belt tilt means. A considerable force can be introduced at high speed and the belt tilt means can be particularly rapidly and widely opened. 
         [0018]    To ensure rapid introduction of force to the belt tilt means, during opening advantageously the release means is connected to the belt tilt means without the use of a spring, with the result that the belt tilt means is opened without the use of a spring. To make a certain spring action of the belt tilt means still possible when the belt tilt means is in normal operation, advantageously the belt tilt means is pivotal somewhat in a spring means when the release means is at rest, in particular at a point where the release means acts on the belt tilt means. A spring contact pressure can have the effect that opening of the belt tilt means is resisted, in opposition to the spring contact pressure, in the first phase of jamming of a mail item, until the belt tilt means is opened beyond the initial deflection angle by actuator. 
         [0019]    Advantageously, the belt tilt means includes a spring element for pressing the belts toward one another, for example to aid a contact pressure by the belts. Should the belt tilt means be opened by a safety function, the direction of this opening movement is in opposition to the spring pressure, with the result that in some cases the contact pressure is in opposition to the spring force and hence becomes more difficult. To avoid this, the spring advantageously acts on the transfer unit such that an opening movement of the release means has the effect of relaxing the spring. This can help the belt tilt means to open for the purpose of the safety function. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The invention will be explained in more detail by means of an exemplary embodiment, which is illustrated in the drawings. 
           [0021]    In the drawings: 
           [0022]      FIG. 1  shows a transfer device having a movable transfer unit, in a diagrammatic plan view, 
           [0023]      FIG. 2  shows the transfer unit in a more detailed plan view, and 
           [0024]      FIG. 3  shows the transfer unit from  FIG. 2 , with a belt tilt means fully open. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0025]      FIG. 1  shows a transfer device  2  in a diagrammatic plan view. It includes a transfer unit  4  in the form of a loading aim which is movable, in particular pivotal, in relation to a stationary unit  6 . The mobility is indicated by a broken line in which the transfer unit  4  is indicated pivoted by 6° in relation to a starting position. In its starting position, mail items  8  are transported by a transport device  10  which has two revolving belts  12 ,  14 , in a straight line in the direction of transport  16  from the stationary unit  6  to the loading arm or transfer unit  4 . Depending on the angle of pivoting of the loading aim, the path of transport is angled somewhat in the region between the stationary unit  6  and the loading arm. 
         [0026]    At a small spacing from the transfer unit  4 , there is arranged an item carrier  18  in the form of a pigeonhole ring which includes a plurality of pigeonholes or item containers  20  that are arranged one behind the other, in the form of a train, and are secured such that they are movable in relation to one another. When the transfer device  2  is in operation, the item carrier  18  moves in a carrier direction  22 , which extends perpendicular to the transport direction  16  when the transfer unit  4  is untilted. Mail items  8  that are transported in the transfer unit  4  are shot one after the other into a respective pigeonhole  20 , with the frontmost end of the transfer unit  4  being entrained in a manner synchronized in speed and position with the respective item container  20  into which the next mail item  8  is to be inserted. 
         [0027]    When a mail item  8  is transferred from the transfer unit  4  to the item carrier  18 , the mail item  8  leaves the transfer unit  4  at an ejection point  24  that is formed by the frontmost elements of the transfer unit  4 . These elements may for example be two rollers  26 ,  28  with the two belts  12 ,  14 . Once the mail item  8  is deposited fully in the desired item container  20 , the transfer unit  4  is pivoted back somewhat in the clockwise direction until the ejection point  24  is positioned opposite a succeeding item container  20 , so that a mail item  8  can be inserted into the latter. 
         [0028]    The mail items  8  are transported in the direction of transport  16  by the transport device  10 , at a speed of 2.5 m/s, and are inserted into the item containers  20 , which move at a speed of 0.5 m/s perpendicular to the direction of transport  16 . Between the individual mail items  8  there are small gaps which make it possible to align the transfer unit  4  in its new position in front of a succeeding item container  20 . This re-positioning is carried out at a frequency of approximately 3 Hz. Here, in particular the front part of the transfer unit  4 , together with the ejection point  24 , is accelerated powerfully in a direction of acceleration that is substantially parallel or antiparallel to the carrier direction  22 . 
         [0029]    So that transport of mail items  8  of differing thickness is possible between the belts  12 ,  14  and in particular between the rollers  26 ,  28 , the roller  26  and with it the front part of the belt  14  are mounted to be movable in relation to the roller  28  and the belt  12 . When the transfer unit  4  is accelerated, forces of inertia act on the movable mounting, the roller  26  and the front part of the belt  14 , as a result of which a contact pressure force of the belt  14  exerted on the mail item  8  that is currently being transported would vary were it not for a corresponding counter-action. This would result in too strong or too weak a contact pressure and hence in damage to the item or slipping of the mail item  8  between the belts  12 ,  14 . 
         [0030]    To prevent this, the front roller  26  is part of a belt tilt means  32 , by means of which part of the belt  14  is mounted to be pivotal about an axis of rotation  34 . The front roller  26  is secured to a rigid tilt arm  36 , which is mounted on the axis of rotation  34  and carries a counterweight  38  at its end in opposition to the roller  26 . The distribution of mass of the belt tilt means  32  is in this case set such that its center of gravity comes to lie on the axis of rotation  34 . 
         [0031]    In the event of the transfer unit  4  moving pivotally about its axis of rotation  30  and acceleration in or in opposition to the pivotal movement, the belt tilt means  32  is dynamically counterbalanced thereby, with the result that the forces of inertia of the individual elements of the belt tilt means  32  counteract one another and the belt tilt means  32  remains at rest even if there is considerable acceleration in relation to the other parts of the transfer unit  4 , for example the roller  28 . This means that a contact pressure force which presses the belt tilt means  32  and with it the belt  14  in the direction of the belt  12  remains at least substantially unaffected by the acceleration. 
         [0032]    A contact force pressing the belt tilt means  32  in the direction of the belt  12  is created by an advantageous form of the belt run of the belt  14 . The belt  14  is tensioned at a force of approximately 300 N. This force pulls the front roller  26  backward as indicated by the arrow  40 . The direction of the arrow  40  is the direction of the bisector of the angle formed by the belt  14  as it is deflected by the roller  26 . The alignment of the tilt arm  36 , that is to say the direction of the line between the axis of rotation  34  and the axis of rotation of the roller  26 , is selected such that an angle is produced between the tilt arm  36 , or the line connecting the axes of rotation, and the force resultant indicated by the arrow  40 . Because the line connecting the axes of rotation does not coincide with the force resultant, a torque is exerted on the belt tilt means  32 , in the direction of the force resultant. This torque has the effect of exerting a contact pressure force on the belt tilt means  32 , in the direction of the belt  12 . The contact pressure force is for example between 10 and 20 N, depending on the angular position of the belt tilt means  32 . This depends on the thickness of the mail item  8  that is currently being transported between the belts  12 ,  14 . Closing of the belt tilt means  32 , brought about by the contact pressure force, and hence clamping of the mail item  8  between the belts  12 ,  14 , may be further reinforced by a spring element. 
         [0033]    Arranged in the region of the axis of rotation  34  is a roller  42  which deflects the belt  14  and whereof the axis of rotation is the axis of rotation  34 . As a result of this, the path of the belt  14  between the rollers  26 ,  42  remains the same regardless of the angular position of the belt tilt means  32 . As a result of the angle between the tilt arm  36  and the direction of transport  16 , when the belt tilt means  32  closes, however, the spacing between the front roller  26  and a rear roller (not illustrated) or the axis of rotation  30  becomes smaller. This means that the tension force of the belt  14  is reduced somewhat when the belt tilt means  32  closes, which has the effect of reducing the tension force of the belt  14  and hence the contact pressure force or closing force of the belt tilt means  32 . This is countered by an increase in the angle between the force resultant (represented by the arrow  40 ) and the tilt arm  36  when the belt tilt means  32  closes, which reinforces a contact pressure force or closing force of the belt tilt means  32 . Depending on the direction of the angle or the elasticity of the belt  14 , these two mutually opposing effects can be balanced so that the closing force is independent of the closing angle of the belt tilt means  32  or can be adjusted to another advantageous form. 
         [0034]      FIG. 2  shows the transfer unit  4  in a more detailed view from above. The belt tilt means  32  is illustrated with its tilt arm  36 , the counterweight  38 , its roller  26  at the ejection point  24  and its contact pressure belt  14 . Also illustrated is a release means  44  with a motorized drive  46  and a gear  48  that is connected at a point of action  50  to a mounting  52  on which the tilt arm  36  is secured. 
         [0035]    The tilt arm  36  may be pivoted slightly in relation to the mounting  52 , as indicated at a pin  54  in a slot  56 . When the drive  46  is at rest, the mounting  52  is mounted rigidly in relation to the drive  46 , it being possible for the tilt arm  36  to pivot somewhat in order to adapt its open position to mail items  8  of differing thickness. With the aid of a spring  58 , which is visible in  FIG. 3 , the belt tilt means  32  is pressed in the direction of its closed position, in its position illustrated in  FIG. 2 . 
         [0036]      FIG. 3  shows the transfer unit  4  with the belt tilt means  32  fully open. In this position, the belt tilt means  32  is turned by more than 90° relative to the position shown closed in  FIG. 2 , with the contact pressure belt  14  pivoted by 90° in its region facing the mail item  8  relative to its closed position shown in  FIG. 2 . The spring  58  that is illustrated in  FIG. 3  takes the form of a torsion spring and is wound in a spiral about the axis of rotation  34 , with the end of the spring  58  that projects to the left and is visible in  FIG. 3  being illustrated as pointing to the left only for the sake of the illustration to make the spring visible. In a correct illustration, the end illustrated would be secured below a mounting  60  and not visible in plan view. 
         [0037]      FIG. 3  shows the belt tilt means  32  with the safety function actuated. The front end of a mail item  8  has left the ejection point  24  and has partly entered the interior  62  of an item container  20 . There the mail item  8  has for example jammed, with the result that it is not inserted any further into the interior  62  despite a feed force effected by the belts  12 ,  14 , which acts in the direction of the ejection point  24  and hence into the item container  20 . In the meantime, the entire item carrier  18  has moved on in the carrier direction  22 , entraining the ejection point  24  in synchronized manner, with the result that there is no or only a small relative movement between the interior  62  and the ejection point  24 . 
         [0038]    With the aid of a sensor  64 , for example an optical sensor  64 , the gap between the ejection point  24  and the item carrier  18  is scanned, the sensor  64  being connected to a processing means  66  and the processing means  66  monitoring the gap and hence the insertion of the mail item  8  into the interior  62 . The processing means  66  recognizes that the for example optical measuring beam generated by the sensor  64  is still interrupted, so the mail item  8  has not yet been fully inserted into the relevant item container  20 . 
         [0039]    At a later point in time, the transfer unit  4  reaches a position in which synchronized entrainment with the item carrier  18  is normally stopped. This would have the effect that the front end of the mail item  8  would be transported further in the carrier direction  22 , while the ejection point  24  is at rest or is even guided back in the opposing direction. To prevent damage caused in this way to the mail item  8  and the transfer unit  4 , the processing means  66  triggers the drive  46 , with the result that the latter moves the gear  48  as indicated by an arrow  68 . The gear  48  acts on the mounting  52 , which is form-fittingly connected to the tilt arm  36  and pulls the latter into its open position, which is shown in  FIG. 3 . The belt tilt means  32  is now opened, by the angle of opening  70  in relation to the closed position. 
         [0040]    The mail item  8 , which is for example 35 cm long, is fully released by this and can now be guided further in the carrier direction  22  without coming into contact with the contact pressure belt  14  or another element of the belt tilt means  32  or the transfer unit  4 . This drastically reduces the risk of damage to the mail item  8  or the transfer unit  4 . There is now enough time to stop the item carrier  18  and to remove the backlog of items without affecting elements of the transfer device  2 . 
         [0041]    When the belt tilt means  32  is opened to its open position, as illustrated in  FIG. 3 , the gear  48  moves the tilt arm  36  in opposition to the spring force of the spring  58 , which is tensioned more as the angle of opening  70  increases. In another embodiment, the spring  58 , which is provided to apply a contact pressure force of the belt tilt means  32  to the mail item  8  that is being transported between the belts  12 ,  14 , may be applied by another or an alternative spring  72  which in  FIG. 3  is shown diagrammatically in the form of a square between the tilt arm  36  and the mounting  52 . The spring  72  presses the tilt arm  36  away from the mounting  52 , with the result that in the closed position of the belt tilt means  32  a contact pressure force is exerted on the mail item  8  between the belts  12 ,  14  by way of the tilt arm  36  and the contact pressure belt  14 . 
         [0042]    When the drive  46  is actuated to open the belt tilt means  32 , the mounting  52  can turn counter-clockwise somewhat without the form-fitting connection acting on the tilt arm  36 . This turning initially relaxes the spring  72 , with the result that the mutual contact pressure force on the two belts  12 ,  14  is reduced. During this, the spring  72  moreover helps to actuate the gear  48 , since it urges in the direction of its open position. As the mounting  52  is pivoted further, the form-fitting connection acts between the mounting  52  and the tilt arm  36 , with the result that the tilt arm  36  is pulled into its open position. During this the spring  72  can remain pre-tensioned somewhat so that the tilt arm  36  is guided without play.

Technology Classification (CPC): 1