Abstract:
A feeding machine for feeding envelopes into a station for further individual handling. A stack of envelopes is held in a downwardly inclined feed channel. The stack of envelopes is transformed into a layered stream by an upward inclined discharge channel including a conveyor unit that carries a stream of envelopes through a gap formed by an imbricator strip and a low friction circulation belt. The layered stream is conveyed to a removal point where a removal device removes individual envelopes for further processing. The conveyance of the layered stream is controlled in such a manner that the removal device can remove individual envelopes at regular time intervals.

Description:
TECHNICAL FIELD 
     The invention relates to a feeding machine for feeding flat, flexible conveyed items which are input in stacks, in particular envelopes, into a station for further individual handling. 
     BACKGROUND ART 
     Feeding machines in which the conveyed items are input, as stacks of conveyed items, into magazines from which the conveyed items are pulled out individually, for example by means of suction rolls or grippers, and transferred into a station for further individual handling are generally known. 
     In modern mail-processing machines which operate at very high clock speeds it is necessary for the magazines of the feeding machines to be frequently filled manually with stacks of conveyed items because the stacks in the magazines are not supposed to exceed a specific height in order to keep the pressure caused by the weight of the stack at its lower end within such limits that the devices for pulling off the individual conveyed items can operate reliably there. 
     The problem of frequent refilling of stacks of conveyed items into magazines of known feeding machines has already been countered by placing before said devices an automatic feeding unit which, as a function of a signal which reports lowering of the stack located in the magazine below a certain level, fed conveyed items out of an elongated stack of upright conveyed items which is conveyed forwards approximately horizontally in a feed channel, by means of obliquely upwardly feeding conveyor belts which have a high degree of friction with respect to the conveyed items, initially upwards and then past an imbricator strip to the magazine in an approximately horizontal direction, without however in the process separating the conveyed items. The feeding of the automatic feeding unit which is placed upstream was continued until a further detector signalled a sufficient degree of filling of the magazine. 
     DISCLOSURE OF THE INVENTION 
     The object of the present invention is to design a feeding machine for feeding flat, flexible conveyed items which are input in stacks, in particular envelopes, into a station for further individual handling in such a way that the number of conveyed items which are input in stacks does not have to be severely limited, and intermediate storage of the conveyed items in a magazine is avoided. 
     This object is achieved according to the invention by means of the features of the appended Patent Claim  1 . Advantageous refinements and developments are the subject-matter of the patent claims subordinate to Patent Claim  1 , to whose content reference is made here expressly without repeating the wording of which at this point. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments are described below with reference to the drawing, in which: 
     FIG. 1 shows a schematic, perspective view of a feeding machine of the type specified here, 
     FIG. 2 shows a schematic side view of the feeding machine according to FIG. 1, with details of a part of the station for further individual handling of the conveyed items being indicated, 
     FIG. 3 shows a perspective view of a detail of the feeding machine according to FIG. 1 in which an imbricator strip is active, and 
     FIG. 4 shows a schematic side view, drawn partially in section, of a modified form of the removal device of a feeding machine according to FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The feeding machine of the type proposed here contains, as is clear from FIG. 1, an obliquely downwardly extending feed channel  1  for holding stacks  2  of conveyed items  3 , which stacks are placed in the feed channel  1  in the way which is shown in FIG.  2 . 
     A discharge channel  4  leads obliquely upwards from the lower end of the feed channel  1 . The negative gradient of the feed channel  1  is selected to be sufficiently large to allow large stacks of conveyed items which are contained in it to slip downwards in the direction of the discharge channel  4 , but at the same time sufficiently small to limit the pressure of the stack on the bottom most item to be conveyed. 
     The feed channel  1  and the discharge channel  4  have a common, viewed in the conveying direction, right-hand angular side wall  5 , a common angular base  6  and a common, viewed in the conveying direction, left-hand angular side wall  7 . The side wall  7  can be adjusted to specific formats of the conveyed items, in the direction transverse to the conveying direction in the manner shown in FIG. 1 by means of angular elements which are attached to said side wall  7  and are provided with elongated holes on the free limb. 
     The base  6  of the feed channel  1  and of the discharge channel  4  is cut out at the junction between the two channels in the way which can be seen in FIG. 1, in such a way that the upper strands  8  of three conveyor belts  9  of a first conveyor belt unit  10  can be guided over the base of the discharge channel  4 . The upper strands of the conveyor belts  9  therefore follow the profile of the discharge channel  4  obliquely downwards and then merge at its upper end, supported by deflection rollers  11 , with a horizontal profile parallel to the plane of a transfer table  12 . The transfer table  12  is provided with longitudinal slots from which the upper strands for the conveyor belts  9  protrude, in their horizontally extending section, somewhat above the level of the table. 
     The lower strands of the conveyor belts  9  are led back over suitably positioned rollers underneath the transport table  12  and underneath the base of the discharge channel  4  to the start of the conveyor belt near to the junction between the feed channel and the discharge channel. 
     Above the upper strands  8  of the conveyor belts  9  of the first conveyor belt unit  10  a second conveyor belt unit  13  whose lower strands lie opposite the upper strands of the first conveyor belt unit from a region before the change of direction of the upper strands  8  to the horizontal profile as far as a region above the first conveyor belt unit  10  in the horizontal section. This profile of the conveyor belts  14  of the second conveyor belt unit  13  can be seen readily in FIGS. 1 and 2. As is indicated symbolically by the dot-dashed line  15  in FIG. 2, the conveyor belts  9  of the first conveyor belt unit  10 , and the conveyor belts  14  of the second conveyor belt unit  13  circulate synchronously. They are made to rotate by a drive device which is indicated by  16  in FIG.  2 . 
     The base of the discharge channel  4  is provided with a portion  17  which is oriented in the conveying direction, in a region between two conveyor belts  9  of the first conveyor belt unit  10 , the upper strand  18  of a circulating belt  19  (see FIG. 2) protruding out of said portion  17  somewhat above the level of the base of the discharge channel  4 , the surface of which belt  19  is low in friction. The circulating belt  19  is, as is indicated symbolically in FIG. 2 by the dot-dashed line  20 , driven in synchronism with and in the same direction as the conveyor belts  9  of the first conveyor belt unit  10 . 
     An imbricator strip  21  interacts with the smooth surface of the circulating belt  19  as opposite surface, the design of said imbricator strip being shown in detail in FIG.  3 . Arranged fixed to the frame to the side of the discharge channel  4  is a guide rail  22  in which a carriage  23  is adjustably held in a direction parallel to the conveying direction of the discharge channel  4 . The carriage  23  bears by means of an arm  24  an imbricator strip block  25  which holds in its lower part an approximately wedge-shaped imbricator strip  26  made of rubber or plastic. The imbricator strip  26  has a front strip  27  mounted before it. The distance between the lower edge of the imbricator strip  26  and the surface of the upper strand  18  of the circulating belt  19  can be adjusted by means of an adjustment knob  28 . By adjusting the carriage  23  in the direction of the guide rail  22  it is possible to set the position of the setting block  25  of the imbricator strip  21  in order to allow for the dimensions of the conveyed items in the conveying direction along the upper strand  18  of the circulating belt  19 . 
     If a stack  2  of conveyed items  3  conveyed is inserted into the feed channel  1  in the way shown in FIG. 2, the conveyed items which are at the bottom are conveyed upwards by the upper strands  8  of the conveyor belts  9  of the conveyor belt unit  10  along the discharge channel  4 , conveyed items  3  which are located higher up being held back by the front strip  7 , and ultimately the imbricator strip  6  initially allowing only the front part of an individual conveyed item to follow the movement of the conveyor belts  9  owing to the set distance from the surface of the upper strand  18  of the circulating belt  19 , with the result that this part of the conveyed item which is conveyed on passes between the lower strands of the conveyor belts  14  of the conveyor belt unit  13  and the upper strands of the conveyor belts  9  of the conveyor belt unit  10  and is reliably conveyed on. A deflection plate  29  which extends over the entire width of the conveyor belt units, and is indicated in FIG. 2, prevents corners or clips or the like which project laterally from the items to be conveyed from running up against parts of the system and leading to incorrect conveying. 
     The imbricator strip  21  which interacts with the upper strand  18  of the circulating belt  19  as an opposite face, and the upper strands  18  of the conveyor belts  9 , thus have the effect that an imbricated or separated stream of conveyed items  3  runs in between the conveyor belt units  10  and  13 , the imbrication distance or separation distance of which is set up at the imbricator strip  21 . This imbricated or separated stream of conveyed items  3  emerges onto the transfer table  12  on the delivery side between the conveyor belt units  10  and  13 , which transfer table  12  leads onto a removal device  30  which is positioned at a certain distance from the delivery side of the first and second conveyor belt units and serves to grasp the front edge of the respective front-most conveyed item  3  of the imbricated stream of conveyed items and to pull off in a clocked fashion the respective conveyed item in order to feed it to further handling or processing means. In the embodiment shown in FIG. 2, the removal device  30  can take the form of a conveying chain  31  which is activated in clocked fashion by a drive  32  as soon as gripper tongs  33  which are attached to the conveying chain  31  have taken hold of the front edge of a conveyed item  3 . The upper claw of the gripper tongs  33  is prestressed against the lower gripper claw in the closed position by spring means, and as soon as the conveying chain  31  has moved the gripper tongs  33  into the pick-up position, it is opened by a cam of the upper gripper claw running up against a cam plate  34 . The cam plate  34  can be lowered by means of a drive  35  in order to close the gripper tongs. Detectors, for example proximity detectors or photoelectric barriers (not shown in the drawing) signal the respective operating position of the conveying chain  31  and of the gripper tongs  33 . 
     If the conveying chain  31  is in the operating position which is indicated in FIG.  2  and in which the gripper tongs  33  are opened and ready to pick up, a control signal, which is derived from the drive or a rotary sensor of said drive, of a control unit  36  outputs a request signal which, via a control line  37 , causes the drive  16  to activate the conveyor belt units  10  and  13  and the circulating belt  19 , and ultimately an imbricated stream of conveyed items emerges on the transfer table  12  on the delivery side of the conveyor belt units  10  and  13  in the manner described above. 
     As soon as the first conveyed item of this imbricated stream of conveyed items interrupts the photoelectric barrier forming a first detector  38 , the output signal of this detector  38  causes the control unit  36  to change the drive  16  into a prepositioning mode, for which purpose, assuming a constant drive speed of the drive  16 , timing means of the control unit  36  activate the drive  16  for a period which is sufficient to move the leading edge of the first conveyed item from the detector  38  as far as the gripper tongs  33 . 
     A second detector  39  which follows the detector  38  in the conveying direction and which can in turn be formed by a photoelectric barrier which is mounted in the transfer table  12  then causes the drive  16  to be fine-controlled by the control unit  36  in such a way that the leading edge of the first conveyed item of the imbricated stream of conveyed items is moved in completely between the gripper claws of the gripper tongs  33 , and the upper gripper claws of the gripper tongs  33  are then closed by the cam plate  34  being activated by means of the drive  35 , after which the drive  32  is switched on and the conveying chain  31  draws off to the left the first conveyed item at its leading edge with respect to the position and setting of the components shown in FIG.  2 . 
     The distance between the photoelectric barrier forming the detector  39  and the base of the gripper tongs  33  is selected such that, after the respective first conveyed item is pulled out of the imbricated stream of conveyed items, the photoelectric barrier or the detector  39  is enabled again and is available for the fine-positioning procedure of the, then, first further conveyed item. The aforesaid distance is therefore in all cases smaller than the minimum separation distance or imbrication distance between the conveyed items. 
     It is also to be noted that the distance between the gripper tongs  33  located in the pick-up position and the output side of the gap between the conveyor belt units  10  and  13  is selected such that a conveyed item which is held by its leading edge by the gripper tongs  33  is still held by its rear edge between the conveyor belt units  10  and  13 . When the conveyor chain  31  is activated, this conveyed item which is grasped by the tongues  33  is then pulled between the conveyor belt units  10  and  13 . In order to set the system to different formats of the conveyed items with respect to the conveying direction, as indicated in FIG. 1, the removal device  30  and the transfer table  12  are designed as one unit and can be moved and adjusted in the conveying direction on a trolley or carriage  40  so that the distance between the gripper tongs  33  located in the pick-up position and the output side of the conveyor belt units  10  and  13  can be changed in accordance with the format of the conveyed items. Furthermore it is to be noted that, in order to support the conveyor belts of the conveyor belt unit  13 , the rollers are mounted on a common frame which can itself be pivoted about a horizontal axis parallel to the bearing axes of the rollers in such a way that the common conveyor belt unit  13  can be pivoted upwards for maintenance purposes or for dealing with faults in the conveyor belt unit  10 . In order to simplify the representation in the drawing, the relevant designs here, which are known to the person skilled in the art, and also means for holding down the conveyed items in the region above the transfer table  12  are omitted. 
     According to the modified embodiment shown in FIG. 4, the removal device  30  can also contain pairs of removal conveyor belts or rollers  41  and  42  which face one another and which also form a conveyor gap, it being possible for the removal conveyor rollers  42  either to be raised into a position of rest, or lowered into a conveying position against the removal conveyor belts  41 , by means of a drive  43 . In this form of removal device  30 , the conveyor belts  41  can circulate continuously. As soon as the leading edge of a conveyed item  3  has been moved between the removal conveyor belts  41  and the removal conveyor rollers  42  after the detector  39  has responded, the drive  43  presses the removal conveyor rollers downwards, as a result of which the front-most conveyed item  3  is moved out of the imbricated stream of conveyed items and is pulled out with its trailing edge between the conveyor belt units  10  and  13  and the processes explained in conjunction with FIGS. 1 and 2 are repeated. 
     The design of the imbricator strip  21  which is shown principally in FIG. 3 is independently significant in that, owing to the hard smooth surface of the circulating belt  19  interacting with the front strip  27  and the edge of the imbricator strip  26 , a very precise setting of the imbrication event, and, to this extent, of the separation of items as they are conveyed by the conveyor belts  9  is given and also as a result of the circulating belt  19  being provided it is also possible to set the format by moving the carriage  23  in the guide rail  22 . It may be expedient here to provide, underneath the upper strand  18  of the circulating belt  19 , a retaining and supporting face of the upper strand  18 , for example by means of part of the base  6  in that area of the upper strand  18  over which the imbricator strip  21  can be adjusted in the conveying direction of the belts  9  in order to adjust the format. 
     In terms of the control device  36 , it is to be noted that by means of rotary sensor output signals of the drive  32  for the conveying chain  31  it is determined when, and over which periods or drive path sections, the drive  16  for the conveyor belt units  10  and  13  is activated. The detectors  38  and  39  determine, as a control means which are arranged downstream, the conveying of the imbricated stream of conveyed items into the gripper tongs  33  or into the conveyor gap between the conveyor belts  41  and the contact rollers  42  (FIG.  4 ). 
     However, in the description above, the imbrication or separation is also to be understood to mean a state of the conveyed items in which they no longer overlap one another but are instead conveyed onto the transfer table  12  in a completely separated state.