Abstract:
A slack box for accumulating continuous web material having a plurality of vertically spaced sections separated by movable members. When the amount of web material in a selected one of the sections reaches a predetermined amount, the movable members, starting with the lowest, are sequentially moved from an operative position separating the slack box into sections to an inoperative position thereby allowing web material stored in an upward section to pass or dump into a lower section. After the web material in the uppermost section has been dumped into the adjacent lower section, a web feeding mechanism is actuated to feed a predetermined amount of web material into the uppermost section.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to web handling mechanisms, and more specifically to a web slack box having a plurality of sections. 
     2. Description of the Prior Art 
     It is known in the prior art to provide slack boxes for storing web material at the feed and take-off ends of a continuously operating machine such as a photographic film processing device. This permits intermittently stopping film transport into or out of the device for short periods of time for some purpose such as inspection, splicing, or the like without affecting the continuous operation of the processing device. One type of slack box for such a machine is shown in German Pat. No. 138,821 comprising one or more solution-filled tanks into which the film is freely randomly fed in serpentine or looped fashion. Such a slack box is not usable in applications in which a dry web is stored or accumulated. Another slack box of this general type receives a freely falling dry web in serpentine or looped fashion, but it is incapable of accumulating a sufficient length of film without crushing the bottom or lower loops of web due to the weight of the upper web loops or convolutions. Another type of slack box, having a rotatable accumulator, is disclosed in U.S. Pat. No.  3,693,859. The slack box comprises a rotatable hub and a plurality of radially extending partitions rotatable therewith and cooperating with a pair of spaced side plates or discs to form a plurality of angularly spaced compartments open at the periphery. The film is fed by a film-feeding mechanism into each of the film compartments in succession as the hub and partitions are rotated by a hub drive mechanism past the film feeding mechanism. The rate of film feed into each compartment and the rotational speed of the hub are selected such that each compartment is substantially filled with film convolutions such as coils and loops of film before the film enters the next succeeding compartment. 
     Another well-known type of slack box comprises a film supporting elevator mechanism for normally accumulating the film on rollers rotatably mounted on upper and lower spaced apart, parallel shafts. The upper shaft is fixed, and the lower shaft and rollers form a part of a vertically, reciprocally movable elevator mechanism. Accordingly, when the film feed into the processing device is stopped to permit a splicing operation or the like, the elevator mechanism begins to move upwardly as the film continues to be withdrawn from the slack box, and when it reaches a predetermined height, a switch is activated by any suitable means for enabling or actuating the film-feeding mechanism. Since the film is fed into the slack box at a faster rate than it is withdrawn therefrom, the elevator mechanism will then move downwardly as it accumulates film, and when it reaches a predetermined point where sufficient film has been accumulated, it will actuate another switch disabling or deactuating the film-feeding mechanism. Although the elevator slack box operates in a satisfactory manner, it is of relatively complicated construction comprising many parts that greatly increases problems of assembly, operability and repair. Accordingly, such slack boxes are expensive to manufacture, and in addition take up a considerable amount of space. Furthermore, in view of the larger number of rollers and loops involved, the force required to pull the film through the slack box is relatively high. 
     Still another known type of slack box is disclosed in U.S. Pat. Nos. 2,855,196 and 2,889,491, and in an article entitled &#34;Operational Experience with Seac&#34; by Ernest F. Ainsworth in &#34;The Review of Input and Output Equipment Used in Computing Systems&#34; published by AIEE, Mar. 1953. In this slack box, one or both of the walls of the box is provided with laterally protruding fixed projections extending partially into the box chamber for releasably catching upper web convolutions, thereby preventing crushing of the bottom web convolutions. A disadvantage of this type of slack box is that the projections are fixed and the web convolutions have to be pulled past the projections as the web is fed from the slack box. This results in increasing the inertia of the system and possible web damage due to web deformation or creasing. 
     SUMMARY OF THE INVENTION 
     This invention, broadly speaking, concerns a slack box having a plurality of sections for storing continuous web material such as film or the like. The slack box comprises a plurality of vertically spaced sections. Each section is separated from the adjacent sections by a divider comprised of a group or plurality of fingers extending through the back of the slack box. Each group of fingers is pivotally mounted on a common shaft for movement into and out of the slack box. Rotation of the shaft removes the fingers from the slack box allowing web material stored in a section above the group of fingers to pass or drop into a section below the group of fingers. The web material is removed from the bottommost section by any suitable film drive mechanism. In one embodiment, one or more sensors is provided that detects when a predetermined amount of film remains in one of the sections such as the bottommost section and upon detecting this condition, initiates a dumping cycle that provides for sequentially dumping of each section to the next lower section. After the top section has dumped, a web-feeding mechanism is actuated to feed a predetermined amount of web material into the top section. By dividing the slack box into a plurality of sections, it is possible to store a large amount of web material, particularly thin base material, in a given vertical area without causing crushing of bottom web convolutions or loops stored in the slack box, since the load in each section is kept below that which would cause crushing of the bottom loops. Accordingly, slack boxes can be constructed which are of substantially greater capacity than heretofore was possible. 
     The invention and its features and advantages will be set forth and become more apparent in the detailed description of the preferred embodiment presented below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the detailed description of the preferred embodiment of the invention presented below reference is made to the accompanying drawings, in which: 
     FIG. 1 is a front perspective view, partially cutaway, of one embodiment of a slack box constructed in accordance with this invention; 
     FIG. 2 is an enlarged perspective view of a portion of the back of the slack box of FIG. 1 showing the components of the movable member that divides the slack box into sections. 
     FIG. 3 is an enlarged sectional view taken along the section line 3--3 of FIG. 2 showing the connection between two components of the movable member; and 
     FIG. 4 is a schematic electrical wiring diagram for the slack box of FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Because slack boxes are well known, the present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. 
     Referring now to FIG. 1, the components of a slack box constructed in accordance with the present invention are shown. A slack box, generally designated 10, is comprised of a vertical web storage chamber 11 surrounded by a back 12, a front 14, sides 16, a top 18, and a bottom 20. The storage chamber 11 is divided into a plurality of sections 22. The bottom or lowermost section has been designated A, the middle sections have been designated B, C, and D, and the top or uppermost section has been designated E. The size and number of sections 22 is determined by the stiffness of the web material stored in box 10 and the desired storage capacity. Each of the sections 22 is separated from the adjacent sections by a plurality of members, such as hemispherical-tipped fingers 24. The fingers 24, extend through openings 25 in back 12 of box 10. Each finger 24, as shown in FIG. 2, is attached to one end of a generally L-shaped lever arm 26. Each set of lever arms 26 is freely mounted on a common shaft 28 affixed to back 12 for rotational movement around the axis defined by shaft 28. Rotation of shaft 28 moves fingers 24 by virtue of a lost motion connection to be described hereinafter between a normal operative position where they extend into chamber 11 of box 10 and prevent web material in one section to pass into an adjacent lower section, and an inoperative position where they are at least partially removed from chamber 11 and web material in one section is free to pass into the adjacent lower section. 
     Referring now to FIG. 3, the arrangement including the lost motion connection for mounting lever arms 26 on shaft 28 is shown. Two collars secured to shaft 28, designated 30 and 32 respectively, prevent sideway movement of lever arm 26 on shaft 28. The collar 30 has a laterally extending pin 34 attached thereto which extends parallel to and is spaced apart from shaft 28 and which extends into an oversized hole 36 in lever arm 26. The difference in size between pin 34 and hole 36 allows for lost motion such as a small amount of rotation of shaft 28 without movement of lever arm 26. This small amount of rotation allows one of a group of fingers 24 to remain in an inoperative position when web material is between the end or tip of the finger and the front 14 of box 10. Such lost motion also allows a web convolution, which remains above a finger 24 following a dumping operation to be explained hereinafter, to move the finger to its inoperative position when the web convolution is pulled so that the web convolution can freely pass into the section below the finger. 
     Pivotal upward movement of a lever arm 40 (secured to shaft 28) in the direction of arrow A, as shown in FIG. 2, rotates shaft 28 and collars 30 and 32 attached in the same direction. As lever arm 40 moves, for instance, under the influence of a solenoid 42, collars 30 rotate and pins 34 attached thereto engage one side of holes 36 causing rotation of lever arms 26. The rotation of lever arms 26 moves fingers 24 from normal operative positions to inoperative positions. Web material retained in one section 22 by fingers 24 is then able to pass by the fingers into the adjacent lower section. After the stored web material has passed into the lower section, shaft 28 is rotated in a direction opposite arrow A to return fingers 24 to their operative positions. Rotation of shaft 28 is accomplished by pivotal downward movement of lever arm 40, spring means (not shown) attached to shaft 28, and/or one or more weights 38 attached to lever arms 26. If the front end or tip of a finger 24 encounters web material as it moves from its inoperative to its operative position, the aforementioned interplay or lost motion between pin 34 and hole 36 allows a momentary halt of movement of finger 24 thereby minimizing damage to the web material. After the web material has passed, the finger 24 moves by virtue of gravity and weight 38 to its operative position. Fingers 24 which do not encounter web material move without interruption from their inoperative positions to their operative positions. Also, such lost motion allows a web convolution, which remains above a finger 24 (between sections A and B for example) following a dumping cycle from section B to section A, to move the finger to its inoperative position when the convolution is pulled so that the convolution can pass into section A without web damage. 
     A web material feeding mechanism comprising, for example, drive and pinch rollers 43, 44 respectively is rotatably mounted adjacent top 18 of box 10 in spaced relationship to an opening, generally designated 45, in top 18. The mechanism includes a drive motor, not shown, which upon energization by the closure of a switch or other means, generally designated 46, (FIG. 4) feeds a specified or predetermined amount of web material into section E. The amount of web material fed into section E is controlled either by timing the length of time the mechanism is actuated, using a mechanical or photoelectric sensor that detects the amount of web material in section E, or by using other means well known to those skilled in the art. Web material is withdrawn from box 10 by conventional means (not shown) through an opening, generally designated 48, in bottom 20 of box 10. A pair of sensors 50, such as, for example, one or more fluidic or infrared sensors or a mechanical weight-sensitive switch, is mounted within section A near opening 48 and preferably within walls 51 of box 10. The sensors 50 sense the presence or absence of convolutions of web material within section A and generate a signal when the convolutions are absent, which occurs when the amount of web material in section A falls below a predetermined minimum amount. As shown in FIG. 4, the signal generated by sensor 50 energizes a sequencer 52 comprising known integrated circuit timer and position integrated circuit counters which starts a dumping cycle. The dumping cycle comprises energization of sequencer 52 for sequential energization of the solenoids 42 between the various sections. Energization of solenoid 42A-B positioned between sections A and B for a predetermined time period allows dumping of web material from section B into section A and sequential energization of the solenoids 42 between the higher sections designated 42B-C, 42C-D, and 42D-E respectively, sequentially dump each higher section to the next lower section. After the top section has dumped, switch means 46 or the like is activated to energize the web feeding mechanism to feed the predetermined amount of web material into section E. 
     In operation, sensor 50 senses the absence of a predetermined minimum amount of web material, for example by sensing an empty condition such as the absence of web convolutions in section A and generates a signal to energize sequencer 52. The energization of sequencer 52, as previously explained, starts the dumping cycle. The dumping cycle ends after the predetermined amount of web material has been fed into section E. Since the dumping cycle is started whenever the sensor 50 detects the lack of the predetermined minimum amount of web material in section A, more than one dumping cycle can be in progress at any given time. It should be noted that the rate of the feeding of web material into section E is faster than the rate of withdrawal of web material from section A in order to allow accumulation of web material within box 10. Also, the dumping cycle, once started, continues to completion whether or not web material is still being withdrawn from box 10. 
     In accordance with an alternative embodiment of the present invention, one or both sensors 50 in section A are replaced with one or more sensors (not shown) in section E. With such an apparatus, web material is continuously fed into section E until the section is full, at which time the sensor(s) generates a signal to actuate a sequencer similar to sequencer 52. The sequencer, starting with section B, sequentially dumps each higher section to a lower section. By providing sensing means in each section 22 or providing logic within the sequencer, dumping of a full upper section to a full lower section is prevented. The web material is intermittently withdrawn from section A at a sufficient rate to prevent overfilling or emptying of slack box 10. Any suitable interlocks may be provided to stop the web being fed into section E in the event of inadvertent overfilling of slack box 10, or to stop the web being withdrawn from the box in the event of inadvertent emptying of the box. Thus, with the slack box of the present invention, web material can be continuously fed and intermittently withdrawn or intermittently fed and continuously withdrawn. 
     The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.