METHOD AND APPARATUS FOR FOLDING AN ELONGATE BAG

Abstract: The apparatus comprises an assembly of three linearly positioned frames, namely a folding frame (4), a backing frame (3), and a holding frame (5). Each of the folding and holding frames comprises a circular array of spaced rods, which array can be advanced and retracted longitudinally, and expanded and contracted radially. The backing frame comprises a circular array of spaced rods which are fixed. The folding frame operates within the plastic storage bag to be folded. The folding frame is adapted to expand to grip and stretch a length of "section" of the bag. This section then can be advanced over the backing frame to bring it into register with the latter. The frame can then be contracted to deposit the section of bag on the backing frame and the stack of bag sections already folded and carried thereon and to clamp the stack to the backing frame. The folding frame can then be retracted to withdraw it from the stack. The holding frame is adapted to be advanced over the backing frame, contracted to clamp the stack to the backing frame, and retracted to withdraw it from the frame. The rods of the arrays are spaced so that the stack of folds may be clamped in a sawtooth fashion to hold them tight to the backing frame. The holding frame rods, when clamped on the stack, serve as a template for the next following section of bag to be folded over.

Description: FIELD OF THE INVENTION The present invention relates to a method and apparatus for folding an elongate storage bag, such as the type of bag used to hold silage. More particularly, the invention concerns a method and apparatus for pleasing an elongate cylindrical bag into radial pleats gathered into a plurality of superposed annular layers. BACKGROUND OF THE INVENTION During recent years, the use of agricultural storage bags as a replacement for more conventional silage storage systems has become common. By utilizing such bags, in the place of pits or silos, it is possible to reduce spoilage and high constructions costs. Such bags are manufactured from thin gauge plastics, such as polyethylene and the like. The material is slippery and without rigidity. The bag are generally cylindrical, having diameters in the order of 8 - 9 feet (2,4 - 2,7 m) and lenghts of up to about 150 feet (45.7m). Typically, such bags weigh in the order of 180 to 260 lbs (82 to 118 kg). Specialized machinery, termed a silage bag filler, is used to compressively load the silage into the storage bag. The design of these silage bag fillers requires that the storage bags be supplied thereto folded in an annular gathered accordion-like fashion. The mounth of the bag is positionned onto the end of the filler. A net-like device is used to hold the free end of the bag against movement in a direction away from the filler. As the silage is fed into the bag, the machine moves away from the filled fixed end of the bag, longitudinally expanding the gathered portion of the bag and thus causing it to be sequentially filled. When the storage bag is received from the plastics manufacturer, it comes in the form of a roll. The bag has usually been folded in half longitudinally and then wrapped onto a cardboard spool. There is one bag per spool. In preparing the bag for use with the filler, it is necessary to unfold and open the bag into its desired cylindrical form an then convert it into an annular pleated form. Folding machines for converting silage bags into the ′accordion- stack′ form are known; for example, see U.S. Patent 4,424,051. However, the purchase cost of bags folded utilizing prior art machines is high, presumably because the machines are complex and costly. The present invention was developed through a series of evolving prototypes. This work was undertaken in an effort to develop a simpler and less expensive folding machine. SUMMARY OF THE INVENTION Applicant's initial attempt to provide a means for folding the bags involved a manual process using a horizontally disposed backing frame. The fundamental process steps involved unrolling the spooled bag, opening the bag from its folded, flattened form into its cylindrical form, and pleating the stock into superposed annular layers over the backing frame. More particularly, this was accomplished by providing a horizontal hollow rectangular backing frame. The rectangular backing frame comprised four boards standing vertically on edge and having an outwardly projecting horizontal flange along the bottom edges thereof. The bag was suspended on its spool above the backing frame. Two men would be positioned within the rectangle. They would begin by pulling the mouth of the bag down over the outside surface of the backing frame. Two more men, positioned outside the backing frame, would then place four plyboards in register against the backing frame boards, to clamp the mouth section of the bag against the backing frame. The inside men would then pull or force another length of bag down over the plyboards, to form the first fold or pleat. The outside men would then pull the playboards down and out of the formed fold. They would then replace the plyboards in clamping fashion over the fold now in place. And this procedure would be repeated until the entire bag had been converted to an annular pleated form. The bag would then be tied, to hold it together, and removed from the frame. The horizontal flange acted to support the vertically extending pleated portion of the bag, during the folding operation. From this prototype, several conceptual fundamentals emerged. The evolving system utilized: a central backing frame for forming the mouth section of the bag (and subsequent sections as well), when pulled thereover, into a fully open tubular condition; a means for clamping the outermost section of the bag drawn over the backing frame to said frame, said clamping means being operative to move from the outside in, relative to the frame, said clamping means being operative to function as a templet or plyboard when in the clamping position to cause a new bag section drawn down thereover to take the position of the outermost fold in the developing annular superposed stack, said means being retractable from the stack; and a means for opening a discrete bag section, extending between the supply roll and the backing frame, and drawing it over the backing frame and any prior bag sections positioned on the frame and clamped thereto, and depositing said section thereon in a fully open tubular state. Whilst the above-described system was generally satisfactory, some drawbacks therewith existed. More particularly, the process was found to be both labour-intensive and slow. Typically, it took the four men approximately forty-five minutes to fold a single bag. The next embodiment attempted to replicate the folding action of the manual workers, but in an automated fashion. In this unit, the functions of the four workers were replaced by two sets of movable frames. More particularly, there was now provided three horizontal frames mounted on a central vertical support shaft. The bag supply roll was suspended above the frames/shaft assembly. The central frame on the shaft was the backing frame - it was stationary on the shaft, but could be contracted inwardly. A "folding" frame was positioned on the top, above the backing frame; a "holding" frame was positioned on the bottom. The folding and holding frames were substantially the same. Each comprised four discrete on-edge boards arranged in a rectangular pattern. Each such rectangle was expandable and contractable in a horizontal plane and could be moved up or down. Air cylinders were used to bias the boards of the folding and holding boards through the needed movements. The movements of this embodiment are shown in Figures 5a - 5l. In operation, the mounth of the bag would be manually pulled down over both the folding and backing frames. The holding frame would then be expanded out, moved up to register with the backing frame, and moved in to clamp the mouth section against the backing frame and act as a templet for the next step. The folding frame would then be expanded out beyond the lower frames, stretching the plastic as it did so, and moved down to fold a section of the bag over the holding frame. The holding frame would then be expanded out and retracted down. The backing frame would then be contracted slightly, to keep the location of the outer perimeter of the frame plus its load substantially constant and the folding frame would be contracted inwardly to clamp the formed fold to the backing frame. The holding frame would then be expanded outwardly, raised back into register with the backing plate, and contracted to clamp the newly formed fold to the backing frame. And the folding frame would be raised free of the stack, preparatory to being expanded to grasp a new section of bag. This routine would be repeated until the bag was completely pleated. At this point, the evolving system further utilized: a linear train of components comprising supply roll, folding frame, backing frame, and holding frame; and each of said folding and holding frames had the capacity to expand and contract radially and advance and retract longitudinally, to carry out the desired functions. However, because the backing frame was still horizontally disposed with its boards extending vertically, and the support flange could no longer be provided, as it would interfere with the action of the holding frame, there was missing a means for supporting the folded material; the latter displayed a tendency to slip down off the frame during the folding operation due to its slippery nature and increasing weight. Additionally, the folds lacked uniformity of width and the inner folds exhibited a tendency to wrinkling, caused when the backing frame was reduced in perimeter to thereby accommodate successive folds. At this point in the evolution of the invention it was decided as a preferred feature to rotate the apparatus through 90° from the vertical to the horizontal, to thereby alleviate the slippage problem. Additionally, as another preferred feature, it was decided to alter the configuration of the frames from generally rectangular to circular, and to replace the four flat wooden boards comprising each frame with a ring or array of circumferentially spaced apart "fingers" or rods. Fingers of each of the holding and forming frames were positioned to fall between or intermesh with the fingers of the backing frame. Thus they could be contracted in the clamping mode to stretch the pleated material into a sawtooth configuration, as explained below. These modifications were effective to eliminate wrinkling and improve uniformity of fold width. This preferred form of the invention is now capable of pleating a bag in about 15 minutes with a 2 man crew. According to one broad aspect of the invention, there is provided an apparatus for pleating sequential annular sections of an elongate tubular plastic storage bag, which is not sufficiently rigid to be self-supporting, said apparatus being operative to form the bag into a stack of superposed annular folds. The apparatus comprises: (a) a stationary generally tubular backing frame means for supporting each fold of the stack, when placed about the frame, in an open generally tubular state; (b) a movable generally tubular folding frame means, axially aligned with the backing frame means on one side thereof and being adapted to expand and contract about its longitudinal axis and to advance and withdraw along said axis,for opening and gripping a section of the bag, for drawing said section over and into register with the backing frame means and any bag folds already on the backing frame means, for depositing said section on the backing frame means and its stack to form a fold, for clamping the stack against the backing frame means, and for withdrawing from the backing frame means and its stack, when actuated to do so; and (c) a movable-generally tubular holding frame means, axially aligned with the backing frame means on the side remote from the folding frame means and being adapted to expand and contract about its longitudinal axis and to advance and withdraw along said axis, for clamping the stack against the backing frame means, for functioning as a templet when in the clamping mode to assist the folding frame means to form a fold, said holding frame means being operative to withdraw from the stack when actuated to do so. According to another broad aspect, there is provided a method for pleating an elongate tubular plastic storage bag to form said bag into a stack of superposed annular folds, comprising: (a) providing an assembly comprising three aligned tubular frames having a common longitudinal axis, said frames comprising a central backing frame, a folding frame on the side of the backing frame adjacent the bag to be pleated, and a holding frame on the other side of the backing frame said folding and holding frames being operative to expand outwardly and contract inwardly and to advance and withdraw along the longitudinal axis: (b) opening the mouth section of the bag and drawing it over the folding and backing frames and into register with the latter: (c) positioning the holding frame over the backing frame and contracting it to clamp the mouth section of the bag to the backing frame: (d) expanding the folding frame to outwardly stretch a section of the bag, which section is spaced from the clamped mouth section a distance approximately equal to the length of the fold to be made: (e) drawing the stretched section of the bag over the holding frame which is in the clamping mode and into register with the backing frame to form a fold: (f) contracting the folding frame to clamp the fold stack to the backing frame: (g) withdrawing the holding frame from the stack: (h) expanding the holding frame and advancing it over and into register with the backing frame; (i) contracting the holding frame to clamp the fold stack to the backing frame and withdrawing the folding frame: and (j) repeating the sequence of steps (d) to (i) inclusive to complete forming the bag into a stack of superposed annular folds. According to another broad aspect, there is provided a further method for pleating an elongate tubular plastic storage bag to form said bag into a stack of superposed annular folds, comprising: (a) providing an assembly comprising three aligned frames having a common horizontal longitudinal axis, said frames comprising a central backing frame, a folding frame on the side of the backing frame adjacent the bag to be pleated, and a holding frame on the other side of the backing frame, said frames each comprising a ring of spaced apart horizontally extending rods, said folding and holding frames being operative to expand and contract radially and to advance and withdraw along the longitudinal axis, the rods of the folding and holding frames being disposed to intermesh with those of the backing frame when positioned in register therewith: (b) opening the mouth section of the bag and drawing it over the folding and backing frames and into register with the latter; (c)positioning the holding frame over the backing frame and contracting its ring of rods to clamp the mouth section of the bag to the backing frame ring in sawtooth fashion; (d) expanding the folding frame ring of rods to outwardly stretch a section of the bag, which section is spaced from the clamped mouth section a distance approximately equal to the length of the fold to be made; (e) drawing the stretched section of the bag over the holding frame, which is in the clamping mode, and into register with the backing frame, to form a fold; (f) contracting the folding frame ring of rods to clamp the fold stack to the backing frame ring in sawtooth fashion; (g) withdrawing the holding frame from the stack; (h) expanding the holding frame ring of rods and advancing it over and into register with the backing frame; (i) contracting the holding frame ring of rods to clamp the fold stack to the backing frame ring in sawtooth fashion and withdrawing the folding frame; and (j) repeating the sequence of steps (d) to (i) inclusive to complete forming the bag into a stack of superposed annular folds. DESCRIPTION OF THE DRAWINGS Figure 1 is a simplified schematic side view showing the bag roll, the opened mouth of the bag and the pleating apparatus with the folding frame in the expanded or gripping mode; Figure 2 is a perspective view from the rear of the pleating apparatus; Figure 3 is a front view of part of the folding frame, showing the means for contracting and expanding the circular array of rods; Figure 4 is a plan view from the rear showing the holding frame in the clamping mode, a stack of folds on the backing frame, and the folding frame in the expanded mode; Figure 5 is a schematic diagram showing the movements of the frames of the first moving-boards prototype of the apparatus; Figure 6 is a schematic diagram showing the movements in perspective of the frames of the preferred staggered-rods version of the apparatus during the course of one cycle; and Figures 7 - 11 are partly sectional side views of the pleating apparatus showing the frames in their various positions during selected actions of one cycle. DESCRIPTION OF THE PREFERRED EMBODIMENT Having reference to the drawings, the pleating apparatus 1 comprises, in general, a support assembly 2, a central backing frame 3, a folding frame 4, and a holding frame 5. This apparatus functions to pleat annular sections 6 of an elongate plastic storage bag 7, supplied in the form of a roll 8 on a spool 9, to thereby form the bag into a stack 10 of superposed annular folds 11. As shown, the backing frame 3 is centrally positioned relative to the other frames 4, 5. The folding frame 4 is positioned in front of the backing frame 3 and operates within that portion 12 of the bag 7 extending between the roll 8 and said backing frame. The holding frame 5 is positioned behind the backing frame. The three frames 3, 4, 5 are generally annular and tubular in configuration. They are each positioned on edge, so as to extend up in a vertical plane. Their central longitudinal axes are horizontal and coincident. The roll 8 is positioned at the front end of the train of components and the pleating process is carried out in a horizontal plane. The support assembly 2 comprises an upstanding T-shaped member 13 comprising a base plate 14, a vertical member 15, and a horizontally extending tubular member 16 mounted on the vertical member. The backing frame 3 is fixedly mounted on the tubular member 16. The holding frame 5 is slidably mounted on said tubular member 16, for movement therealong. And a tubular shaft 17 extends through the tubular member 16, for sliding reciprocation therein. At its forward end, the shaft 17 carries the folding frame 4 affixed thereto, whereby said frame may be moved in the direction of its longitudinal axis. A double-acting cylinder 18 is secured at its ends to the tubular member 16 and the shaft 17. Contraction of the cylinder 18 will therefore move the folding frame 4 toward the roll 8 and away from the backing frame 3; expansion of the cylinder 18 will move the folding frame 4 over and into register with the backing frame 3. Rollers 19, 20, mounted on the tubular member 16, facilitate the sliding movement of the shaft 17. A second double-acting cylinder 21 has its ends connected with the holding frame 5 and the tubular member 16. Expansion of the cylinder 21 will advance the holding frame 5 over and into register with the backing frame 3. Contraction of the cylinder 21 will retract or withdraw the holding frame 5 out of register with said backing frame 3. Rollers 42, 43, mounted on the holding frame 5, facilitate its sliding movement along the tubular member 16. The backing frame 3 comprises a circular plate 24 welded to the tubular member 16 and extending in a vertical plane. Attached to the plate's peripheral margin and extending outwardly radially is a plurality of vertical rods 25. A horizontally extending rod 26 is secured to each such vertical rod 25. Each horizontal rod 26 is of sufficient length to fully support the stack 10 of folds 11 to be deposited thereon. The radius of the circular array 27 of rods 26 is such that, when the bag sections 6 are deposited thereon, they are maintained in an open, generally tubular, circular state. The folding frame 4 comprises a central hub 28 secured to the forward end of the shaft 17. A plurality of radially extending spokes 29 are secured to and project outwardly from the hub 28. Each spoke 29 comprises a tubular bushing 30 and a telescoping member 31 extendable outwardly from the bushing. As shown in Figure 3, an actuator ring assembly 32 is mounted on the folding frame 4 for biasing the telescoping members 31 in or out as required. More particularly, the actuator ring assembly 32 comprises a ring 33 mounted to rotate on rollers 34 mounted on and projecting horizontally from the hub 28. The ring 33 is connected with the telescoping members 31 by pivotally attached tangential links 34a. A pair of cylinders 35 are pivotally connected to the ring 33 and hub 28. Extension or contraction of the cylinders 35 will rotate the actuator ring 33 and cause the links 34a to extend or contract the telescoping members 31, as needed. Eath telescoping member 31 of the folding frame 4 has attached to its outer end a finger assembly 36. The finger assembly 36 comprises a crosspiece 37, extending transversely of the telescoping member 31, and a pair of horizontal "fingers" or rods 38 secured to the crosspiece and extending parallel to the central longitudinal axis of the folding frame 4. The rods 38 are formed with an inwardly bent forward portion 38a, to reduce snagging of the bag 7. The horizontal portions 38b are of sufficient length to support the bag section 6 which is to form one leaf of the fold 11. From the foregoing, it will be noted that the folding frame 4 provides a circular array 39 of circumferentially spaced apart rods 38. The array 39 may be expanded or contracted radially and advanced or withdrawn longitudinally. The holding frame 5 is virtually identical to the folding frame 4. It comprises a hub 40 having a sleeve 41 mounted on the tubing member 16 for sliding movement therealong. The rollers 42, 43 carried by the sleeve 41 facilitate such movement. Spokes 44 extend outwardly and radially from the hub 40. The spokes 44 comprise bushings 45 and telescoping members 46. The telescoping members 46 have finger assemblies 47 mounted thereon to provide an array 48 of horizontally extending, circumferentially spaced rods 49. While not shown, an actuator ring/link/cylinder assembly, identical to that described and shown for the folding frame, is provided to bias the telescoping members 46 in or out. Thus the holding frame 5 provides a circular array 48 of circumferentially spaced apart rods - the array may be expanded or contracted radially and advanced or withdrawn longitudinally. As illustrated in Figures 2 and 4, rods of each of the arrays 27, 39, 48 are arranged in staggered relation so that when one or both of the folding and holding frame arrays 39, 48 is interacting with the backing frame array 27 in a clamping operation, the stack 10 of folds 11 is stretched in a sawtooth fashion. The operation of the pleating apparatus 1 is shown in Figures 6a - 61 and 7 - 11. In the first step, the mouth section 50 of the bag 7 is drawn over the contracted folding frame 4 and onto the backing frame array 27. The holding frame array 48 is expanded and advanced into register with the backing frame array 27 and then contracted to clamp the mouth section 50 onto the backing frame array 27 in an open stretched state in a sawtooth configuration. The folding frame array 39 is then expanded at its most advanced location, to stretch a bag section 6 spaced forwardly of the edge of the clamped mouth section 50. The bag section 51, extending between the front edge of the clamped mouth section 50 and the rear edge of the section 6, has a length equal to the length of fold to be made. The folding frame array 39 is then retracted to bring it into register with the backing frame 27 and contracted to deposit the sections 51 and 6 on the layered structure consisting of the backing frame array 27, the mouth section 50, and the clamping holding frame array 48. The folding frame array 39 is further contracted to clamp the stack of sections 50, 51 onto the backing frame array 27. The holding frame array 48 is simultaneously expanded and then withdrawn rearwardly from the stack 10. The holding frame array 48 is then expanded, advanced into register again with the stack 10, and contracted to clamp the outermost surface of the stack 10. The folding frame array 39 is simultaneously expanded and then is withdrawn forwardly from the stack and the sequence of steps e to 1 (Figure 6) is repeated until the bag 7 is fully converted to the annular stack form. The bag can then be tied and removed. It will be noted from the foregoing that the pleating apparatus comprises folding and holding frames that bracket the stationary backing frame and that have the capability to expand and contract radially and to advance and withdraw longitudinally. The folding and holding frames alternate at cooperating with the backing frame to hold the stack clamped at all times during the pleating operation. The array rods of each of the folding and holding frames are adapted to intermesh with or fall between the array rods of the backing frame, when in register therewith, so as to clamp the stack in a ′sawtoothed′, slightly stretched state. These features combine to ensure that the slippery non-rigid stack of folds remains constrained and supported in a tightly bound together, stretched, and uniform annular form. Thus snagging, air entrapment, and fold wrinkling are minimal. Control of the strokes, timing and sequence of the biasing means (the cylinders) can be carried out in any suitable manner which will be readily apparent to one of skill in the art. In simplest form, the control means can comprise manually operated valves. The specific form of such control means does not form part of the present invention and thus is not more specifically described. The invention is characterized by a number of advantages, including: relatively rapid folding of the bag; uniformity of the fold length; the folds are relatively wrinkle-free; the apparatus is relatively inexpensive and simple to build and operate; and its lend itself to automatic controls. The foregoing description sets forth the best mode of the invention currently known to applicant. The scope of the invention is defined in the claims now following.

Claims: 1. Apparatus (1) for pleating sequential annular sections of an elongate tubular plastic storage bag (7), which is not sufficiently rigid to be self-supporting, said apparatus being operative to form the bag into a stack (10) of superposed annular folds (11), said apparatus comprising: (a) a stationary generally tubular backing frame means (3) for supporting each fold (11) of the stack (10), when place about the frame (3), in an open generally tubular state; (b) a movable generally tubular folding frame means (4), axially aligned with the backing frame means (3) on one side thereof and being adapted to expand and contract about its longitudinal axis and to advance and withdraw along said axis, for opening and gripping a section of the bag (7), for drawing said section over and into register with the backing frame means (3) and any bag folds (11) already on the backing frame means (3), for depositing said section on the backing frame means (3) and its stack (10) to form a fold, form clamping the stack (10) against the backing frame means (3), and for withdrawing from the backing frame means (3) and its stack (10), when actuated to do so; and (c) a movable generally tubular holding frame means (5), axially aligned with the backing frame means (3) on the side remote from the folding frame means (4) and being adapted to expand and contract about its longitudinal axis and to advance and withdraw along said axis, for clamping the stack (10) against the backing frame means (3), for functioning as a templet when in the clamping mode to assist the folding frame means (4) to form a fold, said holding frame means (5) being operative to withdraw from the stack (10) when actuated to do so. 2. The apparatus as set forth in claim 1 wherein: the axes of the three frame means (3,4,5) are substantially coincident and lie in a substantially horizontal plane; the backing frame means (3) comprises an array (27) of spaced apart and substantially horizontally extending rods (26), of sufficient length to support a fold along substantially its length, and means (24,25) for supporting the array; the folding frame means (4) comprises an array (39) of spaced apart and substantially horizontally extending rods (38), of sufficient length to support a fold section along substantially its length, and means (29,32,17,18) for supporting the array (39) and expanding, contracting, advancing and withdrawing it; the holding frame means (5) comprises an array (48) of spaced apart and substantially horizontally extending rods (49), of sufficient length to clamp a fold section along substantially its lenght, and means (44,17,18) for supporting the array (48) and expanding, contracting, advancing and withdrawing it; the rods (38,49) of each of the folding and holding frame means (4,5) being positioned to intermesh with the rods (26) of the backing frame (3). 3. The apparatus as set forth in claim 2 wherein: the arrays (27,39,48) are each generally circular. 4. A method for pleating an elongate tubular plastic storage bag (7) to form said bag (7) into a stack (10) of superposed annular folds (11), comprising: (a) providing an assembly (1) comprising three aligned tubular frames (3,4,5) having a common longitudinal axis, said frames (3,4,5) comprising a central backing frame (3), a folding frame (4) on the side of the backing frame (3) adjacent the bag (7) to be pleated, and a holding frame (5) on the other side of the backing frame (3), said folding and holding frames (4,5) being operative to expand outwardly and contract inwardly and to advance and withdraw along the longitudinal axis; (b) opening the mouth section of the bag (7) and drawing it over the folding and backing frames (4,3) and into register with the latter; (c) positioning the holding frame (5) over the backing frame (3) and contracting it to clamp the mouth section of the bag (7) to the backing frame (3); (d) expanding the folding frame (4) to outwardly stretch a section of the bag (7), which section is spaced from the clamped mouth section a distance approximately equal to the length of the fold to be made; (e) drawing the stretched section of the bag over the holding frame (5) which is in the clamping mode and into register with the backing frame (3) to form a fold; (f) contracting the folding frame (4) to clamp the fold stack (10) to the backing frame (3); (g) withdrawing the holding frame (5) from the stack (10); (h) expanding the holding frame (5) and advancing it over and into register with the backing frame (3); (i) contracting the holding frame (5) to clamp the fold stack (10) to the backing frame (3) and withdrawing the folding frame (4); and (j) repeating the sequence of steps (d) to (i) inclusive to complete forming the bag (7) into a stack (10) of superposed annular folds. 5. A method for pleating an elongate tubular plastic storage bag (7) to form said bag (7) into a stack (10) of superposed annular folds (11), comprising: (a) providing an assembly comprising three aligned frames (3,4,5) having a common horizontal longitudinal axis, said frames (3,4,5) comprising a central backing frame (3), a folding frame (4) on the side of the backing frame (3) adjacent the bag (7) to be pleated, and a holding frame (5) on the other side of the backing frame (3), said frame (3,4,5) each comprising a ring of spaced apart horizontally extending rods (26,38,49), said folding and holding frames (4,5) being operative to expand and contract radially and to advance and withdraw along the longitudinal axis, the rods (38,49) of the folding and holding frames (4,5) being disposed to intermesh with those of the backing frame (3) when positioned in register therewith; (b) opening the mouth section of the bag (7) and drawing it over the folding and backing frames (4,3) and into register with the latter; (c) positioning the holding frame (5) over the backing frame (3) and contracting its ring of rods (26) to clamp the mouth section of the bag (7) to the backing frame ring in sawtooth fashion; (d) expanding the folding frame ring of rods (38) to outwardly stretch a section of the bag (7), which section is spaced from the clamped mouth section a distance approximately equal to the length of the fold to be made; (e) drawing the stretched section of the bag over the holding frame (5), which is in the clamping mode, and into register with the backing frame (3), to form a fold; (f) contracting the folding frame ring of rods (38) to clamp the fold stack (10) to the backing frame ring (26) in sawtooth fashion; (g) withdrawing the holding frame (5) from the stack (10); (h) expanding the holding frame ring of rods (26) and advancing it over and into register with the backing frame (3); (i) contracting the holding frame ring of rods (26) to clamp the fold stack (10) to the backing frame ring (26) in sawtooth fashion and withdrawing the folding frame (4); and (j) repeating the sequence of steps (d) to (i) inclusive to complete forming the bag (7) into a stack (10) of superposed annular folds (11).

Inventors: SMITH-GANDER, DWIGHT
Applicants: ALBERTA AG-INDUSTRIES LIMITED
Application year: 1988
Main classification: B31B41
IPC codes: B31B19, B65H45