Abstract:
An automatic fold-pan assembly for attachment to a sheet folding machine is provided which includes at least one fold-controlling paper stop disposed in the fold-pan assembly in a space between upper and lower plates. The positioning of the paper stop a predetermined distance from the sheet-entrance mouth of the assembly is controlled by a computer in conjunction with stepper motors which are arranged to direct the forward and rearward movement of the paper stop.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to buckle-type sheet folding machines and more particularly to an automatic mechanism for adjusting the position of the paper stops in the fold pan of such buckle-type sheet folding machines. 
     Buckle-type sheet folding machines typically comprise a series of rollers and fold-pan assemblies. A sheet of paper to be folded is inserted between two rotating rollers of a first roller set and is driven by these two rollers into a first fold-pan of a first fold-pan assembly. A forward edge of the sheet eventually strikes a paper stop in the fold pan. However, the two rollers continue to feed the sheet forward. This feeding continues until the sheet buckles, and the bulge of the buckle eventually extends between two rollers of a second roller set. These rollers fold the sheet at the bulge and feed this folded edge into a second fold-pan of a second fold-pan assembly. 
     Upon striking a second paper stop, there is a new buckle formed in the sheet and this buckle is, in turn, inserted between two rollers of a third roller set. This process continues until the sheet is folded a desired number of times. A typical folding machine may fold a sheet several times. In most buckle-type folding machines, the paper stops in the fold-pan assemblies are adjustable so that the positions of the folds on the paper sheets can be controlled. An example of such a fold-pan assembly is taught in Boyer, U.S. Pat. No. 3,856,293. 
     However, problems exist in prior art sheet folding apparatuses. In many such apparatuses, it is difficult to adjust accurately the positions of the paper stops. Some adjustments on the fold-pan assemblies are difficult to get to because of the position of the fold-pan assembly within the folding machine. Moreover, skilled operators are required because of the complexity of setting up the pan-fold assemblies from job to job. 
     Another problem which exists in the art is the need to make folds on sheets which are perpendicular or parallel with the printed matter on such sheets. Normally, paper stops on the fold-pan assemblies are perpendicular with the longitudinal axes of the fold-pans so that the sheet edges registered by paper stops are also perpendicular with longitudinal axes of the fold-pans. the resulting folds of such sheets are parallel with these registered edges. However, it is often the case that printed material on the sheets is not perpendicular or parallel with the sheets edges. Some printing on the sheets may be skewed slightly. Therefore, it is sometimes desirable to cause these sheets to register at slight angles relative to the fold-pan&#39;s longitudinal axes so that the folds may be made square with the printed material. In prior art devices, such skewing is difficult to accomplish. 
     Finally, yet another problem with prior art fold-pan assemblies is that they have no provision to handling sheet material having tabs extending therefrom. Such tabbed sheet material could previously be folded only by the use of special folding machines and, typically, could not be folded in prior art fold-pan assemblies. 
     Accordingly, the need still exists in the art to provide a fold-pan assembly which can be adjusted readily and rapidly by relatively inexperienced operators and which can be adjusted both for skewed printing and for tabbed sheet material. 
     SUMMARY OF THE INVENTION 
     The present invention meets that need by providing an automatic fold-pan assembly for attachment to a sheet folding machine. The automatic fold-pan assembly of the present invention includes at least one upper plate and at least one lower plate defining a space therebetween and having a sheet-entrance mouth at one end thereof. At least one fold-controlling paper stop is disposed in that space and is movable toward and away from the sheet-entrance mouth. Means for positioning the paper stop are provided so that the paper stop may be positioned a pre-determined distance from the sheet-entrance mouth. The positioning means include control means for automatically determining the desired position of the paper stop relative to the sheet-entrance mouth and drive means responsive to the control means for moving the paper stop to the desired position. 
     In a preferred embodiment of the invention, the control means includes a specially programmed general purpose computer which controls a drive means which automatically positions the paper stop in the desired position. The drive means for the fold-pan assembly preferably includes a stepper motor with a drive belt connecting the stepper motor to the paper stop. Preferably, the computer is programmed to control simultaneously a multiplicity of fold-pan assemblies in a folding machine. 
     In a preferred embodiment of the invention, a plurality of paper stops are spaced across the upper and lower plates with the stops being interconnected so that they move in unison toward and away from the sheet-entrance mouth. The paper stops may be interconnected by a suitable means such as a bar assembly which is arranged transversely across the upper plate. 
     To control the plurality of paper stops, the apparatus of the present invention may include dual stepper motors with each individual stepper motor driving opposite ends of the bar assembly. Thus, the computer individually controls the operation of the stepper motors to bias the bar assembly to compensate for printed sheets having printing thereon which is skewed from either a normal or parallel relationship to the edge of the printed sheet. 
     In operation, the computer control initializes the position of the paper stops upon each start-up of the automatic fold-pan assembly. Preferably, limit switches are positioned on the assembly to detect the end of travel of the paper stops during initialization. This provides the computer with position location information which can be utilized to drive the paper stops into their proper position. 
     Additionally, the paper stops of the present invention have curved surfaces facing the sheet-entrance mouth. These curved surfaces can act as sheet deflectors when the paper stops are positioned substantially at the sheet-entrance mouth. Such positioning is desirable when only some of the fold-pan assemblies in the folding machine need to be utilized for a particular job. The curved surface of the paper stops acts to cause the paper to follow the track of the rollers in the folding machine and to deflect the paper sheets away from the sheet-mouth entrance. 
     Finally, one or more of the paper stops in the fold-pan assembly may be removed to accomodate the folding of sheets having tabs extending therefrom. This permits the tabs to be inserted further into the assembly and yet not interfere with the folding of the sheet. 
     Accordingly, it is an object of the present invention to provide an automatic fold-pan assembly which is easily positioned and adjustable and which eliminates the problems of the prior art. This and other objects and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a buckle-type sheet folding machine having several sheet folding sections; 
     FIG. 2 is a perspective view of the fold-pan assembly of the present invention; 
     FIG. 3 is a somewhat enlarged rear perspective view of the stepper motor and gear arrangement on the fold-pan assembly; 
     FIG. 4 is a sectional side view of a paper stop used in the practice of the present invention; and 
     FIG. 5 is a schematic view of the automatic fold-pan assembly of the present invention with computer control means. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, there is shown in schematic form a multi-section sheet folding machine 10 in which a sheet is fed through several folders, with each folder section being positioned at right angles to a preceding fold section. It will be apparent to those skilled in the art that individual fold sections can be arranged in either a tandem configuration or at right angles to one another. 
     In operation, sheets are sequentially fed from a stack and sheet feeder 12 into a first buckle fold parallel fold section 14. After a fold is made in a sheet fold section 14, the sheet is ejected to a conveyor 16 which carries the folded sheet in the direction indicated by the arrow to a second buckle fold section 18. This section is referred to by those skilled in the art as an 8-page fold section because the sheet folded once in each of the first two fold sections can be trimmed to provide an 8-page leaflet. 
     From the 8-page fold section 18, the sheet is carried by a conveyor 20 to a 16-page fold section 22. Finally, the sheet is carried by conveyor 24 to a 32-page fold section 26 from which the folded work is fed into a stacker 28. It will be understood by those skilled in the art that each fold section may include several fold-pan assemblies as further described below. 
     FIG. 2 illustrates in greater detail fold-pan assembly 30. It should be understood that several such fold-pan assemblies 30 are utilized in sheet folding machine 10, and their structures are all essentially the same. Fold-pan assembly 30 comprises a plurality of spaced apart upper plates 32 and lower plates 34 which define a space 36 between them for receiving sheets to be folded. The sheets are received at sheet-entrance mouth 38, which is defined by the open space between the upper and lower plates at the end of fold-pan assembly 30. 
     A plurality of paper stops 40 are movable in gaps 41 between the plurality of spaced upper plates 32. Paper stops 40, best shown in FIG. 4, are positioned such that their respective front facing surfaces 42 extend into open space 36 betwen the upper and lower plates. Surfaces 42 stop the sheets from traveling any further into the fold-pan assembly 30, and are set, as described in further detail below, so that the inserted sheets are folded at the desired location. 
     A bar assembly 44 extends transversely across upper plates 32 so that the paper stops 40 may move in unison toward and away from sheet-entrance mouth 38. Suitable fastening devices such as bolts 46 secure the paper stops 40 to bar assembly 44. 
     Abutment bar 48, located near sheet-entrance mouth 38 secures upper plates 32 together. Abutment bar 48 is located so that when bar assembly 44 is adjacent thereto, the front facing surfaces 42 of paper stops 40 will be substantially at the sheet-entrance mouth 38 of the fold-pan assembly. In this position, the paper stops 40, with curved front facing surfaces 42, act as sheet deflectors. 
     This positioning of the papers stops 40 is desirable when only some of the many fold-pan assemblies in folding machine 10 need to be utilized for a particular job. The curved front facing surfaces 42 on the paper stops 40 act to cause the sheets being fed to follow the track of the rollers in the folding machine and to deflect the sheets away from sheet-entrance mouth 38. 
     At the opposite end of fold-pan assembly 30 is a rear support bar 49. Rear support bar 49 is attached to plates 32 and 34 and supports a number of machine elements including limit switches 66 and 68, as explained in further detail below. 
     Referring now to FIGS. 3 and 4, bar assembly 44, having paper stops 40 secured thereto, is driven toward and away from sheet-mouth entrance 38 by stepper motors 50 and 52 which operate timing belts 54 and 56, respectively. As shown in FIG. 2, bar assembly 44 is secured to timing belts 54 and 56 so that paper stops 40 are driven in unison. 
     As best shown in FIG. 3, stepping motor 52 drives gear 58 which in turn drives gears 59 and 60. Gear 60 is on the same spindle as gear 62 around which timing belt 56 extends. Thus, operation of stepper motor 52 causes movement of timing belt 56 through intervening gears 58, 59, 60 and 62. 
     Provision is also made for manual operation and positioning of bar assembly 44. Adjustment knob 64, best shown in FIG. 3, may be pulled outwardly moving gear 59 out of engagement with gear 60 and into engagement with gear 61. Manual adjustment of knob 64 then causes timing belt 56 to move in response. Similarly, a manual adjustment knob (not shown) associated with the opposite end of pan-fold assembly 30 can provide manual adjustment of timing belt 54. 
     A pair of limit switches 66 and 68, respectively, are mounted on rear stop bar 49 to detect the rearward movement of paper stops 40 against rear stop bar 49. FIG. 3 illustrates the construction of limit switch 68 and its positioning. Corresponding limit switch 66 operates in substantially the same manner. As paper stops 40 move rearwardly toward rear support bar 49, metal plunger 72 is contacted. Plunger 72 is supported in plunger support member 76 and is normally biased by a spring (not shown) outwardly from rear stop bar 49. As plunger 72 moves rearwardly through plunger support member 76, its presence is detected by limit switch 68 which is preferably a proximity switch. This information is relayed to computer control means 80 which, in turn, deactivates stepper motor 52. Limit switches 66 and 68 may be magnetic proximity switches, such as Model No. E2F-X2E2 proximity switches manufactured by Omron Corporation. 
     The computer control means 80 includes a video monitor 82 and a keyboard 84 from which information may be inputted into the computer. In a preferred embodiment of the invention, the computer is a System 3000 manufactured by Tandy Corporation. Software is provided to operate the computer control system to enable automatic operation of the multiple pan-fold assemblies in sheet folding machine 10. A computer listing of the preferred software for computer 80 is appended to the end of this specification. 
     The software operates computer 80 as follows. Upon start up of the system, the program initializes all of the variables in the system and causes position controller 86 and motor drive 88 to move the paper stops to an initial position. The operator is then prompted to enter variables into computer 80 including the number of fold pans to be in operation and the length of paper to be folded. The software program automatically calculates the proper paper stop positions and then activates stepper motors 50 and 52 to position the bar assemblies 44 and 44&#39; to their proper positions relative to the sheet entrance mouth 38. 
     Computer 80, in conjunction with position controller 86 and motor drive 88, operates the stepper motor pairs on individual pan assemblies. In a preferred embodiment of the invention, the motor drive may be a model DPF72 manufactured by Anaheim Automation, the position controller may be model DPF37, also manufactured by Anaheim Automation, and the stepper motors may be model numbers 23PMC401 also manufactured by Anaheim Automation. 
     FIG. 5 illustrates schematically how computer 80 controls the operation of two fold-pan assemblies 30 and 30&#39;. The operator of the sheet folding machine inputs information into computer 80 through keyboard 84. This information relates to the length of the sheets to be fed and the positioning of bar assemblies 44 and 44&#39; in their respective pan-fold assemblies. This, in turn, results in the sheets which travel into the pan-fold assemblies being folded at the desired location. The software also permits the operator to input information which will cause biasing of the bar assembly. 
     Upon start-up of sheet folding machine 10, stepper motors 50, 52, 50&#39; and 52&#39; initialize the location of paper stops 40 adjacent rear support bar 49. The information inputted into computer 80 is then utilized by position controller 86 in conjunction with motor drive 88 to drive the stepper motors and cause the paper stops to be advanced to the desired locations. 
     Stepper motors 50 and 52 and 50&#39; and 52&#39; may be operated independently. This independent operation of the stepper motors permits biasing of the respective bar assemblies to compensate for printed sheets having printing thereon which is skewed somewhat from either a normal or parallel relationship to the edge of the printed sheets. That is, for example, stepper motor 50 may cause the left end of bar assembly 44 to move slightly farther forward than the right end. This compensates for a printed sheet having skewed printing thereon. Such biasing of the bar assembly may be accomplished either automatically by the operator inputting information into computer 80, or may be adjusted manually through the use of manual adjustment knob 64 as explained above. Where a particular pan assembly is not to be utilized for a particular job, computer 80 directs the stepper motors to drive the bar assembly and associated paper stops all the way forward to sheet-entrance mouth 38. There, the curved foward facing surfaces 42 of paper stops 40 act as sheet deflectors causing the sheets to be passed along to the next pan assembly in the system. 
     To accommodate sheets having one or more tabs extending therefrom, one or more of the paper stops 40 can be removed from the bar assembly 44. This permits the tabs on the sheets to be inserted further into the assembly and yet not interfere with the proper positioning of the sheet against the remaining paper stops. ##SPC1## 
     Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.