STACKING DEVICE FOR FANFOLDED WEB

Abstract: Apparatus for stacking a fanfolded paper web (10) from a printer. The mechanism positively guides the web (10) to a point of release (15) located away from the rear wall of the stacker (31) and includes a pair of guide surfaces (16, 44) at the point of release that urge the web (10) into a transverse bend to re-establish previous outfolds and maintain a natural flexibility in the web. The distance between the top of the stacked web on the stacker (31) and the point of release (15) is less than the distance between successive infold and outfold edges of the web. The stacker (31) is tilted and includes two levels (40, 41) of different distance to the point of release (15).

Description: STACKING DEVICE FOR FANFOLDED WEB The invention relates generally to high speed stacking devices for fanfolded paper and more particularly to such devices that maintain more positive control over the paper and its path from a printing station to the stacker and that urge restoration of previous folds in the web. One of the primary problems with the high speed stacking of fanfolded paper is that of urging the paper to refold along the creases previously formed during manufacture. The movement of paper from a supply stack through the printing station and over the forms tractors tends to straighten the paper at the folds and nullify the "memory" the paper has for its original creases when later left to free-fall from its discharge point toward the stack receiving tray. The problem is aggravated when paper is incrementally fed since it is stopped for printing and then moved for the next new line or block of printing. Friction and static electricity also tend to produce additional detrimental effects on the paper motion causing sporadic delay and consequent paper jams. Many efforts have been made in the past to provide stacking mechanisms in which the paper is urged to refold along the already formed creases. Some devices have used extended free-fall paths between the point of discharge to the stack receiving tray. Other devices have used powered flipper devices to alternately direct the paper to either the infolds or outfolds. In addition, various deflector forms have been used to initiate the refolding. Some examples of these attempts are shown in U. S. Patents 4,054,283 and 1,856,972 which show flipping devices;patents 3,460,825 and 2,906,527 which show the use of beaded chains for catching previous creases to encourage refolding;and patents 3,514,096 and 3,255,662 which show deflectors along the stacking walls. With the exception of the devices using flippers, each of the stackers relies on the free-fall of the paper to reform on the stacking tray. The flipping devices are quite accurate in stacking but become expensive due to the increased mechanism required and have a limited speed because of their inertia. It is accordingly a primary object of this invention to provide apparatus for stacking continuous fanfold paper at high speed which provides more positive control of the paper web by limiting its freedom as it enters the stacking tray. Another object of this invention is to provide apparatus for high speed stacking of fanfold paper which hastens restoration of the web "memory" of previous folds by making use of the paper inertia to add impetus to the refolding of both infolds and outfolds at the stacker tray. A still further object of this invention is to provide stacking apparatus for continuous fanfold paper webs which maintains transverse bends in the paper to retain its flexibility during folding allowing more reliable formation of infolds and outfolds. The foregoing objects are attained in accordance with the invention as claimed in the claims by providing a pair of guide surfaces at a point of release from the drive tractors that encourage the reformation of original infolds and outfolds in fanfold paper webs and providing means to concurrently maintain the receiving surface for the forming stack at a distance less than that between successive fold lines in the web. Release of the paper from its guided path occurs over the receiving surface such that alternate infolds and outfolds are urged to restore and the momentum of the incoming paper tends to roll the folds to their respective stack edges. The receiving tray for the stack is formed such that the infold edge is at a level further from the point of release than the midpoint of the stack, and the stack receiving tray and its guide for the infold edge are canted to urge the infold edge into position along a vertical guide means. By maintaining the surface of the stack a distance less than that between successive fold lines, the force of the incoming paper is used to urge the infold against the back plate of the stacker and to in effect roll the outfold down onto the stack into position without allowing the paper to float into position. An elevation motor is controlled by stack top sensors to maintain the receiving surface of the stack within the desired limits during stacking operation. The main advantage offered by the invention is the provision of an apparatus for properly stacking fanfolded paper webs after leaving a printer in a safe, effective and simple manner. The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawing, in which FIG. 1 is a perspective view of a stacking me chanism for fanfolded paper constructed in accordance with the principles of the invention, and FIG. 2 is a view partially in section taken along the line 2-2 in FIG. 1. In the following description, the terms 1,infold" and "outfold" are used frequently. The term "infold" is intended to mean the folded edge of a fanfold web adjacent to the stack aligning surface in the stacker and the term "outfold" is intended to mean the folded edge of the web opposite the infold edge at the open side of the stack. Referring to the figures, fanfolded paper 10 in the form of a web is carried from a source, not shown, between a reciprocating print head 11 and platen 12 by a pair of forms tractors 13 and 14, and is discharged at a point of release 15 between a deflector plate 16 and tractor door 17. Pins 18 at the periphery of each tractor wheel engage marginal perforations in the web to move the paper. Auxiliary stationary arches 19 support the web intermediate the tractor wheels and ramps 20 divert folds from the top edge of deflector 16. Tractors 13, 14 are movably secured to square shaft 21 by means of release clamps 22 for adjustment to the width of the web. Shaft 21 is driven by a suitable motor or power source, not shown. Arched supports 19 can likewise be added or removed necessary for the web support. Paper web 10 is discharged into a stacker that comprises generally a stack aligner panel 30 and stacker tray 31 The aligner panel is supported on frame 32 and is tilted approximately 150 with respect to the vertical. It extends from the frame to the deflector plate 16 and serves as a support against which the incoming infold edges can rest as they accumulate into a stack. Aligner plate 30 has ribs 33 formed thereon which engage the web. The tilt of the aligner may vary from 5 to 250 but has been found preferable at a slope at about 150. Although the aligner surface is shown as formed with ribs 33, it may be alternately made up of a plurality of rods, strips or slots. It is desirable to keep friction to a minimum between the edges and aligning surface during free-fall of the accumulating paper. Aligner panel 30 has mounted therewith a lead screw 34 which is directly coupled to motor 37 and rotatable in guides-35 and 36 at the rear of the aligner plate. The lead screw is rotated in either direction by motor 37 mounted on the underside of frame 32 by an adapter bracket 38. Attached to the lead screw by means of a traveling nut, not shown, is stacker tray 31. The tray has a complex surface of first and second tray portions 40, 41 that form surfaces normal to the back plate and a transitional curve portion 42 joining the two flat portions. Surface portion 40 is lower than the remaining surface of the tray to accommodate the build-up of infold edges. The transverse transitional portion 42 limits the build-up to infold and outfold edges preventing additional build-up at the stack corners. Buildup occurs because the paper creases do not immediately refold to their former thicknesses. Tray 31 is guided during changes in levels by rods 43 attached to frame 32. The distance between the top surface of tray 31 or of the accumulated stack of paper and the point of release 15 is important in attaining reliable stacking. Therefore, motor 37 is controlled through a height control circuit 45 and a stack height sensor to maintain the required distance within an acceptable range of approximately 1 to 3 cm. The sensor shown comprises a light source 46 and light detector 47 arranged to sense obliquely across the receiving surface Other sensing devices and arrangements can also be used. Height control circuit 45 employs a delay in the output of detector 47 to prevent the momentary blocking of the light beam by properly stacking incoming paper from actuating the motor to lower the tray. When the delay is exceeded, however, the motor operates to lower the stacking tray. When the printer is stopped, the tray may be lowered by an override switch. When printing resumes or after a stop, motor 37 acts to raise the tray until light is blocked and then again reverses to lower tray 31 a fixed increment. This action allows for recovery due to possible forms removal or stack attention during a stop condition. When the paper is carried by tractors 13, 14 to the point of discharge 15, the web is then being directed downwardly toward tray 31. The tray height is adjusted so that the receiving surface for the paper is less than a form length but greater than half a form length from the point of discharge. Sufficient paper is fed through by the tractors to allow the leading form to be manually oriented on the tray so that the paper will fold in its original directions and thus properly orient succeeding infolds and outfolds. Thereafter, the stacker will operate independently. Tray height can be adjusted to accommodate forms of different lengths by changing the location of the stack height sensor 47 and light source 46 at the sides of the aligner panel 30. Any adjustment should insure that the distance from the stack surface to the point of release is less than a form length and thereby maintain a more positive drilling force on the form. As the forms enter the stacker from the point of release, the paper follows from the outfold toward the infold without difficulty, since the outfolds were not contorted by the reverse bending. The infolds, on the other hand, have received reverse bending during their traversal over the tractor wheels. This action has, in effect, removed the "memory" so that the form following an infold tends to not want to deflect toward the outfold. By keeping the receiving surface of the tray or stack top sufficiently close to the tractor wheels 13, 14 and tractor doors 17, the form is held against deflector plate 16 which initiates an outbend in the form. As the tractors continue to push the form, the outward bend in the paper is then forced toward the outfold edge. A radius of the tractor doors along the lower edge 44 allows the web to bend outward in a transverse radius and maintain its flexibility without letting longitudinal bends develop. Continued push by the tractor on the next form causes the preceding form to roll smoothly onto the already preceding stacked form. As soon as the outfold has reached its resting place, the following form begins to roll toward the infold edge. The process for the next outfold is then repeated. Deflector plate 16 in conjunction with mainaining the control of a form by the tractors 13, 14 and tractor doors 17 provide a significant combination of guiding effects to restore the fold memory and initiate a transverse bend in the paper to insure a rolling flexibility as additional paper is pushed toward the stack. If the stacker tray did not have the two levels as shown, fold edges on either side tend to build higher than the center so that the stacked surface becomes dished with both the infold and outfold edges higher than the center. The disclosed stacker may be modified in several aspects. Such modifications might include movement of the tray by different means, for example, by pneumatic means or by use of a belt or chain drive. Further, the input drive for the paper could be pressure or friction rolls instead of the tractor wheels. The form aligner plate could be coated with a low friction material in lieu of being ribbed.

Claims: CLAIMS 1. Apparatus for stacking fandolded paper (10) having alternate infold and outfold edges, the paper being urges by drive means (13, 14) along a path toward said paper receiving surface to a point of release (15), characterized by stack aligning means (30) for aligning said infold edges as a stack of said fan fold paper is formed, receiving tray means (31) ad jacent said stack aligning means and being movable relative thereto, said tray means (31) having a paper receiving surface of at least two levels (40, 41) with the lower (40) of said levels being adjacent to said stack aligning means (30), station ary guide means (17, 44) at said point of release (15) having a curved surface extending in the di rection of said outfold edge, deflector means (16) between said point of release (15) and said receiv ing surface means (31) for engaging said paper to initiate movement of said paper (10) toward said outfold edge away from said stack aligning means (30), said deflector means extending from said stack aligning means (30) toward said outfold edge over a portion of said receiving tray surface, and means for maintaining the distance (34, 37, 45, 46, 47) from the top of the stacked paper on said tray means (31) to said point of release (15) less than the distance between successive infold and outfold edges of said paper. 2. Apparatus as claimed in claim 1, characterized in that the two levels (40, 41) of the tray receiving means (31) are each normal to said stack aligning means (30). 3. Apparatus as claimed in claim 21 characterized in that, the edge aligning means (30) is tilted with respect to the vertical, especially by an angle between 5 and 250 4. Apparatus as claimed in claim 1, 2 or 3,characterized in that the deflector means (16) extends from said edge aligning means (30) a distance greater than the width of the lower (40) of said levels. 5. Apparatus as claimed in one of the preceding claims, characterized in that the deflector means (16) has a convex paper engaging surface. 6. Apparatus as claimed in claim 1 or one of the claims 1 to 5, characterized in that the paper receiving means (31) has a curved transitional portion (42) interconnect ing said two levels (40, 41). 7. Apparatus as claimed in claim 1 or one of the claims 2 to 6, characterized in that the stack aligner means (30) has ribs (33) for supporting the infold edges. 8. Apparatus as described in one of the preceding claims, characterized in that the means for maintaining the distance (34, 37, 45, 46, 47) from the top of stacked paper on said tray means (31) to the release point (15) includes optical sensing means (46, 47) for determining the height of stacked paper on said surface (31). 9. Apparatus as described in one of the preceding claims, characterized in that the paper receiving means (31) is moved by a rotatable lead screw (34).

Inventors: GREGORY, FLOYD ARTHUR, RYAN, ROBERT ALLAN, SINGER, FREDERICK WILLIAM
Applicants: INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1981
Main classification: B65H45
IPC codes: B65H45, B41J11