Air Controlled Paper Stacker

1. Field of the Invention

The present invention relates to paper stackers, more particularly it relates to continuous forms paper stackers which are used in conjunction with printers.

2. Description of the Prior Art

Generally, prior art stackers were used for folding a free-falling, continuous stream of paper. One known prior art stacker used with high speed computer printers utilized spinning beaters or flappers. A movable tray was provided to maintain an optimum distance between the top of a paper stack and pair of feeder rollers. The spinning beaters were placed on a rotating axle and comprise deformable plastic extensions that extend from a hub permanently positioned on the rotating axle. The flappers were located on the tray on which the continuous paper form was received after printing, such that they were in juxtaposition to the crease as they were about to fold. In effect, the flappers beat on the seams of the refolded stack and thereby aid in maintaining a substantially flat stack.

A shortcoming of this prior art is that, due to its reliance on free-falling action of the paper it has limitations handling the wide variety of paper forms which are used. Thus, when stacking is not performed properly, the stacker must be stopped and the operator must provide manual assistance.

Another difficulty with prior art techniques occurred in the case of high speed laser printers. In these printers, heat and pressure are used in the process of fusing the toner to the paper. The heat and pressure cause the creases or seams of the continuous form to be ironed-out so that re-stacking is even more difficult.

Previous attempts to overcome these problems in the higher speed printers have been either overly complex or unsatisfactory.

The foregoing illustrates limitations of known prior art. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations as set forth above. Accordingly, a suitable alternative is to provide an air controlled paper stacker including features more fully disclosed hereinafter.

In one aspect of the invention this is accomplished by providing a paper stacker for the refolding of a substantially continuous unfolded paper form including a first and a second forced air supply, a first and second curved surface closely positioned to one another in a facing relationship, means for controlling forced air including an input and an output, the input coupled to movement of the paper form to receive information therefrom, and the output coupled to the first and second forced air supplies.

The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. It is to be expressly understood, however, that the drawings are not intended as a definition of the invention but are for the purpose of illustration only.

In the drawings:

FIG. 1 illustrates a pictorial isometric view of an embodiment of the air-controlled paper stacker;

FIG. 2 is an enlarged cross-sectional view of an embodiment of the air controls and the curved surfaces of the stacker;

FIG. 3 is a pictorial view of an embodiment of the air flow mechanism showing the air flow being directed toward a curved surface;

FIG. 4 is again a pictorial view of an embodiment of the air flow mechanism, however showing the air flow being exhausted through redirection;

FIG. 5 is a block diagram of control circuit used herein; and

FIG. 6-14 comprise the flow chart of control system utilized by the circuit of FIG. 5 to operate the mechanism of FIG. 1.

FIGS. 1 and 2 illustrate generally the entire paper stacker. The paper 10 is received between a first 12 and a second 14 plurality of stacker rollers. It is thereafter directed between a pair of diverging paper guides 16 and 18. By diverging is meant that, a space between the guides 16, 18 is not the same at one end as at an opposite end. The paper 10 then passes a photo-optic sensor 20 and a photo-optic light 22 which indicates to the control mechanism that paper is in the stacker. A pair of air supply tubes 24 and 26 direct an air supply to a pair of air control valves 54, 56 located on opposite sides of the paper 10.

A pair of sheet supply rollers; which are called herein window shade rollers 34, 36 provide a first and second plastic sheet 38, 40 which is pulled around a first and second hollow cylinder 30, 32 and attached to a pair of adjustable fences 42, 44. As the paper 10 passes elongated air control valves 54, 56, a film of air emanates either from valve 54 or 56. The valves are operated by a pair of rotary solenoids 62, 64 which are connected to valves 54, 56 by rods 66. Solenoid 64 is behind the paper 10 and is therefore not shown in FIG. 1, however it is identical to solenoid 62. A stack height sensor 46 is coupled to adjust platform 48 to a desired level for maintaining an optimum distance between the top of the stack of folded paper 10 and the lower extremities of the cylinders 30, 32 at point P.

A more detailed illustration of this stacker is shown cross-sectionally in FIG. 2. The paper 10 is again shown passing between stacker rollers 12, 14 down through paper guides 16, 18 past between the photocell light 22 and sensor 20 along the curved surface of the hollow cylinder 30 which is covered by the poly plastic sheet 38. It should be noted here that the rollers 34, 36 operate in the identical fashion to window shades (and are so-called) because they supply the poly plastic sheets 38, 40 which are adjustable in accordance with the position of the adjustable fences 42, 44.

In the position shown in FIGS. 1 and 2 the air is supplied by valve 54, and is directed around the curved surface of hollow cylinder 30. At this time, the air supply valve 56 is positioned to exhaust the air out of a discharge ort 57 as indicated by directional arrows.

As air is directed onto the curved surface of cylinder 30 (covered by plastic sheet 38) an air film or stream becomes attached thereto (Coanda effect). The resultant air film 39 passing over that surface follows the contour of the curve and because of the negative pressure (Bernoulli effect) on the outer edge of the air film, the paper 10 is attracted to the air film and it also follows the curved surface. Thus, the paper is forced to refold in the proper direction in accordance with the original perforated fold point of the paper forms.

There are two curved surfaces 30, 32 opposite each other, and the air is directed to one of these surfaces at a time, so the paper 10 is forced to refold in the proper direction.

FIGS. 3 and 4 pictorially illustrates the air flow control as it passes through one of the air control valves 54, 56.

In FIG. 3, the air flow is shown being directed onto the curved surface of cylinder 32. The air from tubing 26 enters the inlet 70 passes into manifold 72 and is directed by air direction guide 76 (which is controlled by rod 66) onto the cylinder 32 surface.

FIG. 4 shows the opposite situation. Here, air from tubing 26 enters inlet 70 passes through manifold 72 but is blocked by air direction guide 76 from passing onto the cylinder 32. In this case, the air is exhausted through top air discharge outlet 57.

The air film is directed onto the cylinder surface or blocked in accordance with control signals which electrically operate the pneumatic valves 54, 56. The timing for these valves is controlled by the electronic circuitry as shown in block diagram form in FIG. 5.

This invention is more fully understood when referring to the code edit appearing in the appendix and in conjunction with the flow diagrams of FIGS. 6-14. Line numbers of the code edit are coordinated with the flow diagrams where appropriate.

The circuitry of FIG. 5 is essentially that of a microprocessor 82 driven controller, the function of which is to operate on input signals so as generate output signals from output means 84 to switch the solenoids 62 and 64 at the proper time. Two of the input signals, namely the line pulse and 8LPI (lines per inch) are derived from an attached printer. The line pulse signal occurs with every increment of paper movement and the 8 LPI signal indicates whether printing is at 8 or 6 lines per inch. The remaining signals to the input means 80 are derived from additional components of the stacker mechanism.

After completion of an initialization process, interrupts are enabled and the program then operates in an interrupt driven mode. That is, the program is in an idle loop waiting for an occurrence of any one of the three signals; line pulse from the printer, internal timer completion, or reset switch signal. These signals are directed to the micro processor 82 through OR gate 86.

The normal conditions for starting operation is with the forms not yet between the power driven rollers. It is the operator's responsibility to set the outfold/infold switch in the proper position to indicate the direction of the first fold and to feed the forms into the power driven rollers. This first feeding of forms is performed at a slow stepping rate. This slow stepping rate will be maintained until the first two forms have passed under the curved surfaces of cylinders 30, 32. As the leading edge of the forms passes sensor 20 the leading edge photocell signal is developed. Up until this time, the interrupts generated by the line pulse signals have essentially been ignored. Once the leading edge photocell signal has been generated the next line pulse signal causes the program to examine the condition of the page length switches and the 8 LPI (lines per inch) signal. Appropriate counts, which will be used to control the switching of the air depending on the length of the form and the velocity of paper movement, are then stored in the program. Also at this time, the outfold/infold switch is examined and either the front solenoid signal or back solenoid signal is generated so as to energize the correct solenoid 62 or 64 in order to direct the first form in the proper direction. After this, a special sequence of switching the air off and on is used until the first two forms are loaded. This is to insure that the first page of the forms does not get mispositioned when the air is switched from one curved surface to the other. Upon completion of loading the first two forms, the forms loaded output signal is sent to an indicator (not shown) to indicate that forms have been loaded. After the first two forms have been loaded air will continuously be directed to either the front or back curved surface and switching will take place, back and forth, as the end of each page is detected by the program.

Also, after the first two forms are loaded, each line pulse received will cause an internal timer 84 (part of the output circuitry) to be triggered. Timer 84 will be set to count off a time interval greater than the normal time between lines when the associated printer is printing at it's normal rate. For example, if a printer normally prints at 1200 LPM, the time between line pulses will be 50 milliseconds and timer 84 will be set to some convenient time interval above 50 milliseconds. In the present program this time interval is set for 127 milliseconds. Thus, if the printer is printing at full speed, timer 84 will never expire and will be reset on the occurrence of each line pulse. Prior to being reset, however, the time remaining in the counter can be obtained, and from this value, the actual velocity of paper movement can be calculated. This has little consequence during normal printing, however, since the paper through-put rate of the above mentioned hypothetical 1200 LPM printer is roughly three inches per second when printing at six lines per inch. This rate is considered to be slow and switching takes place at the normal end of a page. But this hypothetical printer is also capable of slewing paper at a maximum rate of 50 inches per second. So the actual velocity can be in the range of 3 to 50 inches per second depending on the duty cycle of printing and slewing. For each line pulse received, the program calculates the average velocity of the forms for the preceeding one-half inch of movement, and causes solenoids 62, 64 to switch early if the velocity is above a certain value and a particular position of the form has been reached. Speeds of 10, 20, 30, 40 and 50 inches per second have been chosen as the velocities that will cause switching to occur early. Switching of solenoids 62, 64 is performed sooner, by a factor equal to one-half inch of form movement, for each of the five velocities.

When printing stops and there are no more line pulses being received, timer 84 will expire and an interrupt will be generated from the timer. This timer interrupt will then cause the velocity calculating subroutine to revert to a condition of slow speed. Also, if the end of this page has not yet been reached and solenoids 62, 64 have already been switched (because of prior high velocity forms movement), the solenoids will be switched back again. This is to insure that the air will be directed to the proper curved surface before starting form movement again.

After completion of a printing operation, the operator presses the unload switch which causes both solenoids 62, 64 to turn off so that the paper can fall freely into the stacker. Also, at this time, interrupts from the line pulse signals are inhibited. Then, three seconds after the trailing edge of the forms have passed the photo-electric sensor, the forms loaded signal is removed and the program returns to the starting point. After performing the initialization process the program is again ready for the start of a new printing operation.

Pressing the reset switch at any time causes the program to return to the initialization process.

The foregoing has described an air controlled, paper stacker which can provide accurate stacking of paper forms as they exit from a printer. Controlled air pressure is used to control the stacking of the paper forms, and the forms are forced to fold at the desired location and then settle in the desired orientation. This is decidedly advantageous when compared to known forms stackers which do not utilize forced folding but function only by the free-falling action of the forms.

It is anticipated that aspects of the present invention, other than those specifically defined in the appended claims, can be obtained from the foregoing description and the drawings. ##SPC1## ##SPC2## ##SPC3## ##SPC4## ##SPC5##