Patent Publication Number: US-7588238-B2

Title: Method and device for gathering sheets

Description:
BACKGROUND OF THE INVENTION 
     The invention pertains to a method and a device for gathering printed sheets, particularly signatures and/or individual sheets. 
     During the gathering process in a book binding system, an individual signature is respectively withdrawn from several collections of identical signatures, wherein the various decollated signatures are delivered to a collecting conveyor in order to form stacks. 
     Known gathering machines feature feeder stations that are arranged in a row and respectively consist of a magazine for accommodating a signature stack, a withdrawal drum with a gripper mechanism for taking hold of and withdrawing the respective bottom signature that is tilted away from the signature stack, and an intermediate support for temporarily depositing the decollated signature. The collecting conveyor features a collecting channel that is oriented perpendicular to the signature withdrawal direction, wherein pushers of a transport chain moving in said collecting channel strip the decollated signatures off the individual intermediate supports and gather the signatures into a book block on the collecting channel. 
     Such a gathering machine that operates with a change of direction is described in DE 14 86 744 B. This machine furthermore features reciprocating intermediate tables for pre-accelerating the decollated signatures for the transport by the pushers of the collecting conveyor. Acceleration systems require further costly structural measures and also impair the functional reliability. 
     A gathering machine with feed stations according to the longitudinal withdrawal principle is known from DE 196 16 047 A1, wherein this gathering machine comprises a conveyor belt that carries a signature stack in a magazine such that a region of the folded edge remains exposed and respectively advances the bottom signature in a correspondingly cyclic fashion, as well as a withdrawal conveyor system that serves for receiving and additionally transporting the advanced signatures and is composed of acceleration rollers. A clamping conveyor consisting of an upper and a lower conveyor belt is arranged downstream of the withdrawal conveyor system and inclined toward the collecting conveyor, wherein this clamping conveyor deposits the decollated signatures on the stack being formed with a synchronous transport movement upstream of a pusher of the collecting conveyor. The signatures decollated by the feeder stations are delivered to the collecting conveyor without a change of direction. 
     Withdrawal systems operating in accordance with the longitudinal withdrawal principle are suitable for higher capacity ranges. However, since this frequently requires a labor-intensive replenishing of signatures in the magazines, bundle feeders that create a stream feed from the signatures stacked into (sheet) bundles are increasingly utilized for filling the magazines, wherein the signatures are quasi decollated. The stream feed is deposited in the form of a stack once again when the magazines are filled such that the signatures are decollated anew in the feeder stations. There also exist signature rolls with signatures that are wound up in a coil in a shingled arrangement. The stream feeds are unwound in unrolling stations and transferred into the magazines of the gathering machine. The regular arrangement of the signatures in the stream feed is lost when the magazines are filled such that the complex decollating process described above needs to be carried out. 
     US 2005 077 670 A1 describes a feeder station that consists of a bundle feeder and a transfer device, wherein the signatures decollated from the (sheet) bundle in the form of a stream feed are placed into a horizontal buffer station realized similar to a magazine in a waterfall-like fashion, and wherein the signatures are then withdrawn from the buffer station again in order to be perpendicularly delivered to the collecting conveyor by the transfer device. The thusly decollated signatures are ultimately deflected with a transfer device and delivered to the collecting conveyor. The signatures consequently are decollated twice in this case. 
     Decollating processes on stack magazines represent functionally critical process steps, particularly if a subsequent decollating process can only be initiated once the preceding signature is completely withdrawn from the magazine as is the case with the aforementioned feeder stations with transverse and longitudinal sheet withdrawal. Due to the parallel arrangement of several feeder stations on a gathering machine, a few malfunctions of individual feeder stations can already result in a substantial reduction of the net gathering capacity. 
     DE 33 15 489 A1 describes a method, in which a stream feed is divided into partial streams of signatures that are uniformly spaced apart from one another, wherein the partial streams are delivered to decollating devices, e.g., gripper drums, without magazining the signatures. The leading edges of the signatures lie on top of one another toward the front and need to reach the gripper drum synchronous with the gripping cycle. Another disadvantage can be seen in that the signatures are delivered into the collecting channel transverse to the collecting transport direction by the gripper drum such that a change of direction with correspondingly jerky transport movements takes place. 
     SUMMARY OF THE INVENTION 
     The present invention is based on the objective of developing a method and a device for gathering printed sheets, particularly signatures and/or individual sheets, which allow the reliable and careful processing of sheets supplied in the form of stream feeds without intermediately storing the sheets in magazines and therefore without decollating the sheets from stacks. 
     The sheets supplied in the form of a stream feed are delivered to the collecting conveyor in order to form stacks without intermediate magazining. The respective front sheet of the stream feed supplied transverse to the transport direction of the collecting conveyor is taken hold of such that it is prevented from turning and transferred to a withdrawal conveyor system for the additional transfer to the collecting conveyor by displacing the sheet in the collecting transport direction. The stream feed is quasi pulled apart in the transport direction of the collecting conveyor such that individual sheets are synchronously delivered to the collecting conveyor in the corresponding cycle. While the displaced front sheet is withdrawn, the ensuing sheet is already transported into the deflection conveyor, wherein a relatively large time window is available for the ensuing sheet in order to reach the deflecting position for the displacement in the corresponding cycle. Therefore, sheets that are irregularly arranged in the stream feed can also be reliably processed to a certain extent. Complicated decollating devices as they can be found in conventional feeder stations for gathering machines are not required. The invention is based on the notion that stream feeds are also supplied in the form of sheets that are completely separated from one another, i.e., sheets that also do not lie on top of one another in a partially identical fashion, wherein this is the case, for example, in the technique of wound-up stream feeds that are rotationally withdrawn. 
     It proved advantageous to supply the sheets in the stream feed such that they lie on top of one another toward the front in a shingled fashion. The respective front sheet lies on the ensuing sheet, i.e., it is withdrawn from the top and does not have to be pulled out of the coherent stream feed. According to one preferred additional development, the arriving stream feed of sheets is pulled apart in several accelerations stages, namely by initially displacing the respective front sheet such that it is deflected in the transport direction of the collecting conveyor with a slower transport speed and then additionally transported by the withdrawal conveyor system with a higher transport speed. This makes it possible to minimize the occurring accelerations such that a careful transport is achieved. The transport speed of the withdrawal conveyor system is preferably slower than the transport speed of the collecting conveyor such that the stream feed is pulled apart in three acceleration stages, wherein the third acceleration stage takes place during the transfer of the sheets to the collecting conveyor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Characteristics of the present invention are described in greater detail below with reference to preferred embodiments of the invention that are illustrated in the enclosed figures. The individual figures show: 
         FIG. 1 , a schematic sectional representation of a gathering machine with an upstream bundle feeder for signature bundles; 
         FIG. 2 , a top view along the line of section II-II in  FIG. 1 ; 
         FIG. 3 , a schematic section through a gathering machine with an upstream unrolling station for signature rolls, and 
         FIG. 4 , a schematic section through an alternative embodiment of the stream feed to the collecting channel of the gathering machine. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The gathering machine  1  has a plurality of feeder stations that are arranged in a row, wherein only a single feeder station realized in accordance with the invention is respectively illustrated in the figures. One individual signature  3  is respectively withdrawn from a collection of identical signatures in each of these feeder stations and delivered to a collecting conveyor  10  of the gathering machine  1  in order to form stacks. The collecting conveyor  10  is formed by a transport channel  11  with a vertical channel wall  11   a  and an inclined channel bottom  11   b , as well as a transport chain  12  with pushers  13  that are uniformly spaced apart from one another and advance the book blocks  2  being formed in the transport channel  11 . 
     In the first embodiment that is illustrated in  FIG. 1 , the signatures  3  are made available in the form of signature bundles  5 , wherein a bundle feeder  20  forms a stream feed  4  from the signatures bundles  5 . In order to form a stream feed of signatures  3  from a signature bundle  5 , the signature bundle is pushed against a separating conveyor  22  that extends obliquely upward while it lies on a conveyor belt  21 , wherein the transport speed of the separating conveyor is higher than the advancing speed of the conveyor belt  21 . This results in the formation of a stream feed  4  with signatures  3  that lie on top of one another toward the rear in a shingled fashion. The gutterstick  3   a  of the signatures  3  points forward in this case. 
     In order to loosen up the signatures  3  in the signature bundle  5 , lateral chain conveyors  23  are provided that constrict the transport width relative to one another approximately in the center of their transport path such that the signatures  3  bulge therebetween. In the front region of the conveyor belt  21 , an upper belt  24  that transports the signatures  3  forward against the oblique separating conveyor  22  is arranged above the signatures  3 . A synchronously driven upper belt  25  is also assigned to the separating conveyor  22  in the first transport section and directed obliquely upward in order to safely transport away the signatures  3 . 
     The additional transport is realized with a conveyor belt  26 , wherein a standardizing device  27  is provided that displaces the signatures  3  of the stream feed such that they are mutually spaced apart by the same distances. The conveyor belt  26  is followed by a turning drum  28  that changes the stream feed  4  into a formation, in which the signatures  3  lie on top of one another toward the front in a shingled fashion and the gutterstick  3   a  points forward. 
     The thusly formed stream feed  4  is then delivered to the collecting conveyor  10  transverse to the collecting transport direction F with the transport speed v 0  by a delivery conveyor  40  that is realized in the form of a conveyor belt with descending incline, wherein a lateral alignment is realized with the aid of guide rails  49 . The left side referred to the transport direction is stationary while the right guide rail  49  is adjustable with respect to the format height of the signatures  3  as symbolized with a double arrow S FH  drawn with broken lines in  FIG. 2 . 
     The respective front signature  3  contacts a stop rail  47  with its gutterstick  3   a  that points forward while the ensuing signatures  3  lying thereunder are additionally transported. The conveyor belt of the delivery conveyor  40  features openings  41  that can be acted upon with suction air in order to hold and additionally transport ensuing signatures  3  on the delivery conveyor  40  in their shingled arrangement while the front signature  3  is braced on the stop rail  47 . 
     According to the invention, the front signature  3  is taken hold of by a deflection conveyor  42  and moved in the collecting transport direction F. The deflection conveyor  42  is formed by driven upper transport rollers  43  that have a conical face and assigned lower inching rollers  44  that can be closed and opened in the corresponding cycle, wherein the signature  3  is clamped at its leading section. The clamping width extends over nearly the entire height of the signature  3  such that it is prevented from turning during the transport by the deflection conveyor. The inching rollers  44  are arranged on a lever that is controlled by a cam plate  46  that, in turn, is driven synchronous with the cycle of the gathering machine  1  by a main drive shaft  14 . 
     The deflection conveyor  42  transports the front signature  3  to the withdrawal conveyor system  50  with a slow transport speed v 1 , wherein the withdrawal conveyor system is formed by a continuously driven acceleration roller  51  and assigned pressing rollers  52 . The withdrawal conveyor system  50  receives the signatures  3  with a higher transport speed v 2  and withdraws the signatures  3  from the stream feed  4 . The inching rollers  44  of the deflection conveyor  42  are pivoted downward in this case and not only allow the accelerated withdrawal of the displaced signature  3 , but also the infeed of the next following signature  3  into the deflection conveyor  42 . 
     A clamping belt conveyor  53  with assigned supporting plate  54  is arranged downstream of the withdrawal conveyor system  50  and inclined toward the collecting conveyor  10 , wherein the clamping belt conveyor transports the signature  3  in front of the respective pusher  13  of the collecting conveyor  10  with the same transport speed v 2 . In this case, the transport speed v 2  is slower than the transport speed v 3  such that another increase in the transport speed takes place during the transfer to the pusher  13 . 
     The front signature  3  therefore is accelerated to the transport speed v 3  of the collecting conveyor  10  in three acceleration stages  0 →v 1 , v 1 →v 2  and v 2 →v 3  such that the front signature  3  is reliably and carefully decollated from the stream feed  4  and delivered to the collecting conveyor  10  in order to form stacks. In this case, preferred transport speeds are v 1 =0.25*v 3  and v 2 =0.8*v 3 . 
     In order to monitor and control the withdrawal of the signatures  3  from the stream feed  4 , a light barrier  48  is provided above the delivery conveyor. Its distance from the stop rail  47  is slightly shorter than the shingle spacing of the signatures  3  such that the light barrier is briefly uncovered during each withdrawal of the respective front signature  3 . The detection of the leading edge of the ensuing signature  3  quasi determines the position of the stream feed  4  relative to the cycle of the collecting conveyor  10  or the deflection conveyor  42  that can be opened and closed, respectively. A control unit that is not illustrated in detail synchronizes the delivered stream feed  4  relative to the collecting conveyor  10  by increasing or decreasing the delivery speed v 0  accordingly. 
     In a second embodiment that is illustrated in  FIG. 3 , the signatures  3  are made available on signature rolls  6 . The signatures  3  are wound up such that they lie on top of one another in a shingled fashion and fixed with a band  34  that is wound up with the signatures. The respective signature roll  6  is unwound while received on an arbor  31  in an unrolling station  30 , wherein a conveyor belt  32  placed against the circumference of the signature roll  32  receives and transfers the stream feed  4  to said delivery conveyor  40  with the aid of another conveyor belt  35 . The band  34  is deflected away from the stream feed  4  and wound up on a roll  33 . 
     In this embodiment, the signatures  3  of the stream feed  4  unwound from the signature roll  6  lie on top of one another toward the front such that their gutterstick  3   a  points forward and the stream feed  4  does not have to be turned, for example, with the aid of a turning drum. The arrangement of the signatures  3  in the stream feed  4  is highly uniform because it was conventionally formed during the withdrawal of the signatures  3  from a rotary printing press. Signature rolls  6  are also particularly suitable for the method according to the invention. 
       FIG. 4  shows an alternative embodiment of the stream feed to the collecting channel  11  of the gathering machine  1 . This embodiment is suitable for processing a stream feed  4  with signatures  3  that lie on top of one another toward the front such that their gutterstick  3  a points rearward. The device is essentially realized in the form of a mirror image of the delivery conveyor  40  and has an ascending incline in order to counteract the incline of the collecting channel  11 . The deflection conveyor  42  takes hold of the leading open edge of the signature  3  and displaces the signature  3  in the transport direction F of the collecting conveyor  10  in order to transfer the signature  3  to the withdrawal conveyor system. 
     The deflection conveyor  42  with the stop rail  47  as well as the delivery conveyor  40  can be adjusted with respect to the format width of the signature  3  transverse to the transport direction F of the collecting conveyor  10  as symbolized with the double arrow S FB  drawn with broken lines in  FIG. 4  such that the signature  3  with its gutterstick  3   a  can always be transferred to the collecting conveyor  10  near the stationary vertical channel wall  11   a  of the collecting channel  11 .