Abstract:
An improved signature stacker is disclosed which has a drive drum which operates to re-orient the signatures into a vertical stack. The drum has a curvature which is less than the maximum allowable curvature that the signatures can withstand and still recover an initial planar configuration elastically. Also disclosed is a direct drive arrangement having the drum being gear driven from a frequency controlled alternating current motor.

Description:
FIELD OF THE INVENTION 
     The instant invention relates to stackers for printed items (“signatures”) after such signatures have exited a press and/or folder. 
     BACKGROUND OF THE INVENTION 
     The flow of printed items in the modern print shop includes many items of equipment. These items serve to, automate the printing process as well as to provide uniformity to the printed items. To allow of the creation of many advertising items and the like, the modern print shop must not only print the items but also fold and stack the printed items with great uniformity and speed. 
     The instant invention relates to improvements in the technology of signature stackers which receive printed items from an article folder which folds printed items received from a press. These stackers, which comprise the final step in the process of assembly of many printed items have, in the past, been the cause of damage to the printed items. This damage includes crushing the printed items, folding over of the edges of such items or creasing the items. Additionally, previous stackers have required complicated direct current drive systems as well as chain and sprocket assemblies to achieve the speed control required by this particular piece of equipment. These drive assemblies have been the source of problems relating to oil sling onto the printed items from the chain as well as the additional requirement of providing a direct current supply to the drive motor. 
     SUMMARY OF THE INVENTION 
     The instant invention in the presently preferred embodiment thereof operates to receive signatures, arranged imbricate, from a press and stack same into a substantially vertical stack. This is accomplished by means of a feed belt in cooperation with the drive drum wherein the drum is of such radius as to permit the signatures to be carried about the periphery thereof without the signatures having suffered such curvature that the signatures are unable to recover their previously planar configuration; that is to say that the maximum curvature for elastic recovery of the signatures is not exceeded. Additionally, the invention comprehends a direct drive system, wherein the drum is driven and supported by shafting which is connected by gearing directly to the drive motor; thereby obviating the need for chains and the problems associated therewith as mentioned previously. 
     It is therefore a primary object of the invention to provide for a drive drum having a curvature less than the maximum elastic recovery curvature of a signature; 
     It is another object of the invention to provide for a direct drive system which precludes the possibility of oil contamination of the signatures; 
     It is a further object of the invention to provide for an alternating current drive motor for such direct drive system. 
     These and other objects of the instant invention shall become apparent from the Detailed Description of the Preferred Embodiment and Claims directed thereto. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the novel stacker. 
     FIG. 2 is a plan view if the top of the stacker. 
     FIG. 3 is a plan view if the right side of the stacker. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The stacker  10 , shown in FIG. 1, consists of a right frame  12  and a left frame  14 . These frames  12 , 14  serve to support the additional components of the device. Frames  12 , 14  are preferably made of plate steel but other materials which have sufficient stiffness to maintain required tolerances of the device are substitutable. Attached to the frames  12 , 14  are a plurality of crossmembers  16 ,  18 ,  20 ,  22  which serve to fix the relative extension of the frames  12 ,  14  from each other, Additionally, the crossmembers  16 ,  18 ,  20 ,  22  support, as shafts, the various moving parts of the stacker  10 . Starting from the input side of the stacker  10 , input rollers  24 , are supported on crossmember  16 . Input rollers  24  provide the support to the input belts  26  at a position closest to the press feeding the stacker  10 . The input belts  26  receive the imbricately arranged signatures  2  from the press and carry the signatures  2  into the stacker  10 . Following the signatures  2 , as shown in FIG. 3, the input belts  26  carry the signatures  2  to pinch rollers  28 ,  30 . The pinch rollers  28 , 30  are arranged in a fixed set  28  and a floating set  30 . The floating pinch rollers  30  are biased towards the fixed pinch rollers by an adjustable spring  32 . The relative movement between the pinch rollers  28 ,  30  allows for constant force to be applied to compress the signatures  2  while allowing for the variation in thickness of the signature stream due to the imbricate nature of the arrangement of signatures  2  therein. Also by keeping a constant compressive force on the signatures  2  the chance of relative movement of the signatures in the input stream is reduced. Following the input stream, the signatures  2  are now captured between input belts  26  and table top, or outfeed belt  34 . The table top belts  34  have a low coefficient of friction so as to allow the signatures  2  to remain stationary when the signatures  2  are at the end of their travel as shall be subsequently described. Continuing along the path of the signatures  2 , the signatures  2  are now fixed between input belts  26  and table top belts  34 . The signatures  2  are now fed onto drive drum  36 . Drive drum  36  serves a plurality of purposes: first, drive drum  36  is the means of mechanical input to the device, providing motive force to both input belts  26  and table top belts  34 ; and secondly, drive drum  36  reverses the orientation of signatures  2  so that the imbricate input stream may assume the configuration of a vertical stack  40 . The drive drum  36  receives its motive power from a variable speed AC motor  38  through a speed reduction gearbox  42 . The AC motor is controlled by a variable speed drive which controls the speed of the motor by changing the frequency of the alternating current supplied to motor  38 . Gearbox  42  also provides, in this preferred embodiment, a right angle change of direction in power flow so that the stacker  10  is of a compact aspect. Furthermore, gearbox  42  eliminates, when cooperative with drive drum  36 , the previously employed chain drive system with all of the problems attendant therein. 
     Continuing along the input stream of signatures  2 , the stream is brought circumferentially about drive drum  36 . The radius of the drive drum  36  is larger than the minimum radius of curvature for elastic recovery of the signatures  2  to their previous planar configuration in the input stream. As noted in the Summary of the Invention, previous stackers exceeded the elastic recovery limit for the signatures  2  and required the weight of signatures in the vertical stack  40  to flatten out the signatures exiting the drive drum  36  resulting in waste of signatures  2 . The instant embodiment of the drive drum  36  eliminates the “cupping” of signatures  2  by having a radius of curvature which does not exceed the elastic recovery limit for signatures  2  for which the stacker  10  is designed, thereby providing an imbricate stream of planar signatures  2  to the vertical stack  40 . As noted above, the signatures are carried about the periphery of drive drum  36  and exit tangentially therefrom. The imbricately arranged signatures  2  now travel atop table top belts  34  and are intercepted by stop  44  which causes the signatures  2  to be forced under one another, due to their imbricate arrangement, and form vertical stack  40  which is subsequently removed by an operator. 
     The presently preferred embodiment of the instant invention described hereabove is indicative of the preferred structure thereof but is in no way meant to serve to restrict the invention more than the Claims appended hereto.