Patent Publication Number: US-6712354-B1

Title: Accumulator apparatus and method having improved sheet registration

Description:
TECHNICAL FIELD 
     The present invention relates generally to accumulator apparatuses and methods for accumulating sheet articles. More particularly, the present invention relates to an improved non-marking accumulator apparatus and method for reducing or eliminating mis-registration of sheet articles processed therethrough so that accumulated sheets are fed properly. 
     RELATED ART 
     Various accumulator apparatuses and methods have been employed in the past for accumulating sheet material or articles such as paper sheets, documents, and the like into stacks for subsequent advancement. Such accumulator apparatuses and methods have particular use in high-speed mail processing where preparation and processing of mailable articles often requires a plurality of sheet articles to be assembled into a packet for further handling which can include, for example, folding, inserting, collating, etc. 
     As just one example of such an accumulator apparatus, U.S. Pat. No. 5,244,200 to Manzke, commonly assigned herewith, discloses a retractable-ramp accumulator and method comprising driven endless elastic belts that feed sheets therebetween along a sheet-feeding path. A series of operatively connected and selectively retractable ramps are utilized for selectively deflecting sheets out of the sheet-feeding path for accumulating the sheets in a stack after they pass the ramps in a stacking location between the ramps and selectively releasable stop gates. 
     Another example of an accumulator apparatus and method is found is U.S. Pat. No. 5,775,689 to Moser et al, commonly assigned herewith. 
     As illustrated in the two exemplary patents identified above, it is common for prior art accumulators and methods to employ endless upper belts and lower belts for seriatim feeding of sheet articles therebetween. Both of these patents outline the basic operational, structural, and control features common to this type of machinery and well known to those skilled in the art. 
     A problem that exists with such prior art accumulator apparatuses and methods, however, is shown in somewhat exaggerated fashion in FIG. 1 herein. When more than two sheets S are stacked in the accumulator and the accumulator drive begins to feed the paper out of the accumulator in feed direction F, some sheets may and typically tend to shingle back and trail the accumulated set. This results in the accumulated set of sheets not being registered or “squared” as shown in FIGS. 3A and 3B. When the mis-registered set is sent to downstream machinery for further processing, this could result in, for example, bad folds and, even worse, machine jamming, machine stopping, and damaged paper. 
     In light of the prior art accumulator apparatuses and methods as described above and their deficiencies, there remains much room for improvement in the art for an accumulator apparatus and method which reduces or eliminates mis-registration of sheet articles processed therethrough so that the accumulated sheets are fed properly and are properly “squared” as shown in FIGS. 2A and 2B. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an accumulator apparatus that reduces mis-registration of sheet articles processed therethrough. 
     It is another object of the present invention to provide an accumulator apparatus that by reducing mis-registration of sheet articles processed therethrough, also reduces bad folds, machine jamming, machine stopping, and damaged paper. 
     It is a further object of the present invention to provide an accumulator method that reduces mis-registration of sheet articles as it is carried out. 
     It is a still further object of the present invention to provide an accumulator method that by reducing mis-registration of sheet articles as it is carried out, also reduces bad folds, machine jamming, machine stopping, and damaged paper. 
     Some of the objects of the invention having been stated, other objects will become evident as the description proceeds, when taken in connection with the accompanying drawings described below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 of the drawings is an exaggerated side view depicting a deficiency with prior art accumulators; 
     FIGS. 2A and 2B of the drawings are plan and side views respectively of a properly registered stack of sheet material; 
     FIGS. 3A and 3B of the drawings are plan and side views respectively of a mis-registered stack of sheet material; 
     FIG. 4 of the drawings is a simplified schematic top view of an accumulator according to the invention; 
     FIG. 5 of the drawings is a simplified schematic side view of an accumulator according to the invention; 
     FIG. 6 of the drawings show a ramp structure with sheet support for use with the accumulator according to the invention; 
     FIG. 7 of the drawings show a ramp structure with biasing element for use with the accumulator according to the invention; and 
     FIG. 8 of the drawings shows an alternative ramp structure for use with the accumulator according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with the present invention, an accumulator apparatus generally designated  10  is provided and shown schematically in FIGS. 4 and 5. The basic operation, structure, and control features of such accumulator apparatuses are well known to those skilled in the art. 
     Accumulator apparatus  10  comprises upper belt means and lower belt means adapted for advancement of sheet articles there between. The upper belt means comprises a plurality of spaced-apart belts illustrated in the preferred embodiment at least partially in FIGS. 4 and 5 as driven upper endless elastic polycord belts UB. Similarly, the lower belt means also comprises a plurality of spaced-apart belts illustrated in a preferred embodiment at least partially in FIGS. 4 and 5 as driven lower endless elastic polycord belts LB. Upper belts UB include lower reaches  20 , and lower belts LB include upper reaches  22 . Upper belts UB and lower belts LB are driven, usually continuously, such that lower reaches  20  and upper reaches  22  move at substantially the same speed in a common direction in which sheet articles can be processed through accumulator apparatus  10  as indicated by entry arrow  12  and exit arrow  14  of FIG.  5 . Upper belts UB and lower belts LB are supported by guide rollers, as will be described below. Any suitable conventional drive system (not shown) can be utilized to drive upper belts UB and lower belts LB and their guide roller such as an operative interconnection of shafts and the utilization of a conventional clutch/brake system (not shown in the instant application but described in the prior art). Lower reaches  20  of upper belts UB and upper reaches  22  of lower belts LB are substantially disposed in and thereby define a generally horizontal feeding plane for sheet articles processed through accumulator apparatus  10 . 
     Accumulator apparatus  10  is preferably modular in design so as to be easily interchangeable in line with other sheet article processing components. Accumulator apparatus  10  also comprises frame portions, as generally described in any of U.S. Pat. No. 5,755,689 or 5,244,200, commonly assigned herewith, and whose contents are incorporated by reference herein. 
     At the entry end  12  of accumulator apparatus  10  where sheet articles can advance into accumulator apparatus  10  between upper belts UB and lower belts LB, entry roller guide means generally designated  40  is provided and comprises a plurality of upper guide rollers  42  fixedly attached in a spaced-apart relationship to shaft  44 . Entry roller guide means  40  additionally comprises a plurality of lower guide rollers  46  fixedly attached in a spaced-apart relationship to shaft  48 . Shafts  44  and  48  are fixedly but rotatably attached to and between side plates  32 A and  32 B. Upper belt UB extends around upper guide rollers  42 , and lower belt LB extends around lower guide rollers  46  as shown in FIGS. 4 and 5 of the drawings. 
     In accordance with this invention, upper guide rollers  42  and lower guide rollers  46  are vertically misaligned along the centerline such that a gap or space exists therebetween. In a preferred embodiment, a space of approximately ¼ of an inch exists between the lowest portions of upper guide rollers  42  and the highest portions of lower guide rollers  46 . Also in the preferred embodiment, upper guide rollers  42  and lower guide rollers  46  are positioned on shafts  44  and  48 , respectively, in an alternating manner where they intentionally are not vertically aligned such that upper guide rollers  42  and lower guide rollers  46  cannot pinch together sheet articles positioned therebetween. In this manner, upper guide rollers  42  and lower guide rollers  46 , in operative association with upper belts UB and lower belts LB, respectively, provide a guide for sheet articles advancing therebetween without pinching or marking the sheet articles. 
     While it is envisioned that accumulator apparatus  10  can be operatively attached downstream of any suitable component for processing sheet articles, accumulator apparatus  10  has particularly advantageous application when directly attached downstream of a device such as a cutter apparatus C, as shown and described in more detail in U.S. Pat. No. 5,775,689, whose contents are incorporated by reference herein, without the use or need of a cutter interface. When so attached, sheet articles exiting cutter apparatus C can enter accumulator apparatus  10  and be guided thereinto by upper guide rollers  42  and lower guide rollers  46  without pinching of the entering sheet articles. As will be apparent to those of skill in the art, a cutter interface can still be necessary in certain circumstances such as, for example, with connection to Right Angle and Turnover Sequencer modules. 
     Downstream from entry roller guide means  40 , accumulator apparatus  10  comprises ramp means generally designated  80  in FIG. 5 for deflecting sheet articles processed between upper belt means UB and lower belt means LB from the horizontal feeding plane. As will be apparent to those of skill in the art of sheet material processing, ramp means  80  can include a plurality of suitable ramp members, such as a pair of side ramp members  82 , a pair of intermediate ramp members  82 A, and a centrally located ramp member  82 B, which holds the novel aspect of this invention. All ramp members can be fixedly positioned. Ramp members  82 ,  82 A, and  82 B can also be selectively retractable for selective diversion of processed sheet articles as will be recognized by those of skill in the art and additionally in accordance with the disclosure of U.S. Pat. No. 5,244,200 to Manzke. 
     As shown in FIGS. 4 and 5, ramp members  82 ,  82 A, and  82 B are operatively interconnected by one or more shafts such as front shaft  84 A, to which ramp members  82 ,  82 A, and  82 B can be fixedly or pivotably attached as described hereinabove, as well as second shaft  84 B. Referring particularly to FIGS. 4-8, ramp members  82 ,  82 A, and  82 B comprise deflecting surfaces generally designated  86  with slots  88  parallel to polycord path (see FIG. 6) defined therein for extension there through of lower reaches  20  of upper belt UB. Ramp members  82  and  82 A are in alignment with the lower reaches  20  of upper belt UB and have the belts passing through their belt slot  88 , whereas ramp member  82 B does not have a belt passing through its belt slot  88 . Deflecting surfaces  86  terminate on the upper ends thereof at upper edges  96 . It is to be understood therefore that deflecting surfaces  86  and upper edges  96  of ramp members  82 ,  82 A, and  82 B extend in an interposed position across the horizontal feeding plane for sheet articles (see FIG.  5 ). 
     Sheet articles advancing through accumulator apparatus  10  between upper belts UB and lower belts LB and past entry nip roller means  40  will therefore contact and be deflected by ramp members  82 ,  82 A, and  82 B out of the horizontal feeding plane and over upper edges  96 . Due to their elasticity, lower reaches  20  of upper belts UB can also be diverted upwardly by sheets deflecting up ramp members  82 ,  82 A, and  82 B as will be appreciated by those of skill in the art. Downstream of upper edges  96 , a deflected sheet article is urged back toward the horizontal feeding plane by resilient action of lower reaches  20  of upper belts UB due to their tension and/or diversion. Accumulator apparatus  10  can include a plurality of rollers  130  attached to shaft  84   a  below upper reaches  22  of lower belts LB to assist in maintenance of tension of upper reaches  22  of lower belts LB for facilitating resilient action by upper reaches  22  against diverted sheet articles. Similarly, accumulator apparatus  10  can include a plurality of rollers  130   a  attached to shaft  135  above lower reaches  20  of upper belts UB to assist in maintenance of tension of lower reaches  20  of upper belts UB for facilitating resilient action by lower reaches  20  against diverted sheet articles. Progressive seriatim feeding of sheet articles in the horizontal feeding plane where the sheet articles are deflected by ramp members  82 ,  82 A, and  82 B causes over-accumulation of sheet articles in a stack or accumulation location past upper edges  96  of ramp members  82 ,  82 A, and  82 B. 
     To further support sheet articles accumulated in the accumulation location, accumulator apparatus  10  can further include support means which can comprise in one embodiment a plurality of spaced-apart supports  98  which can extend from side ramp members  82  and intermediate ramp members  82 A at an elevation slightly higher than upper reaches  22  of lower belts LB. As illustrated schematically in FIG. 6, sheet articles advanced past upper edges  96  of ramp members  82 ,  82 A, and  82 B are accumulated in a stack S which is supported on supports  98 . 
     The leading edges of sheet articles accumulated in stack S are positioned against and stopped by selectively operable stop means generally designated  150  and located downstream from ramp means  80  and supports  98 . While it is envisioned according to this invention that stop means  150  could comprise any suitable means for selectively stopping and advancing accumulated sheet articles, stop means  150  comprises in the preferred embodiment the nip formed by a plurality of spaced-apart upper stop rollers  152  attached to shaft  154  and a plurality of spaced-apart lower stop rollers  156  attached to shaft  158 . In the accumulated position, the leading edges of the sheet articles in stack S collect within this nip and the trailing edges of the sheet articles in stack S are preferably spaced apart a small predetermined distance from vertical edges  92  of ramp members  82  and  82 A, although it is envisioned that they could be in contact with vertical edges  92 . Stack S is therefore contained between vertical edges  92  and stop means  150 . Conventionally, upon receipt of a “feed” signal, rollers  152  and  156  are rotated by a drive means (not shown) and the stack of sheets in the nip are fed downstream and the accumulator emptied. 
     Referring to FIG. 7, in accordance with a novel aspect of this invention, biasing element  200  is provided to reduce or eliminate sheet mis-registration or shingling back as described with respect to deficiencies of the prior art. Biasing element  200 , typically foreseen to be in the form of leaf spring  210  made of stainless steel (or spring steel or equivalent) and is affixed to ramp member  82 B, but other affixture options are possible. In a preferred embodiment, the steel member is approximately 0.010″ thick and ½″ wide by 3.5″ long. The spring is bent as follows: 1.62″ long horizontal lower surface  212  bent at 90 degrees upwardly to 1.5″ high vertical portion  213 , then bent back 90 degrees to 0.19″ and then bent downwardly at 30 degrees for 0.19″. This shape contours to the shape of the lower horizontal and downstream vertical edge  92  of ramp  82 B. A typical method for affixing leaf spring  210  to ramp member  82  comprises the use of fastener  220 , such as a screw, for clamping a lower surface  212  of leaf spring  210  to a lower portion of ramp member  82 B. Substantially vertical portion  213  of leaf spring  210  is positioned after member  82 B, in relation to the direction of sheet travel, leaving a ⅛″ to {fraction (5/32)}″ gap between the vertical edge  92  of the ramp  82 B and the spring  210 . “Substantially vertical”, as used herein means that the portion of the leaf spring is positioned with respect to the horizontal in such a way that the rear edge of a top sheet in a stack is within a small tolerance of (if not directly over) the rear edge of the bottom sheet of a stack, rendering the stack leaning there against “squared”. The upper surface  215  of spring  210  is bent toward ramp member  82 B, resting in belt slot  88 , to eliminate a surface on which the sheet might catch, and not settle properly as part of an accumulated set. 
     The function of biasing element  200  is to urge all the accumulating sheet articles from behind towards and into the nip formed by the upper  152  and lower  156  stop rollers. As the paper clears the ramp  82 B, the spring  210  flexes back keeping pressure on the back edge of the accumulating sheet articles. Therefore, when the exit nip rollers act to empty the accumulator and feed the stack downstream, biasing element  200  urges the entire stack of accumulated articles towards the exit nip to insure that no sheets are left behind (i.e., “shingle back”) in the accumulator. Additionally, since substantially vertical portion  213  will also act as a rear registration member, the stack of accumulated articles will be squarely fed downstream, resulting in cleaner folds, no jamming, and minimal sheet stoppage and paper damage. 
     While it might seem that biasing element  200  can be eliminated by merely moving ramp member  82  and  82 A slightly further downstream towards stop means  150 , this might not be a completely satisfactory solution. The rigidity of ramp member  82  and  82 A, coupled with the smaller sheet accumulation area poses a higher sheet jamming risk. However, though the sheet accumulation area is smaller with biasing element  200 , the fact that biasing element  200  is not rigid and will move with respect to the ramp (i.e. give with the force of the moving and settling paper) will not pose higher sheet jamming risk. 
     FIG. 8 of the drawings also shows an alternative ramp structure for use with the accumulator according to the invention. In this embodiment, because substantially vertical portion  213  of biasing element  200  is used to register the back of the sheets and not ramp members  82 ,  82 A, and  82 B, the rearmost portion of ramp members  82 ,  82 A, and  82 B can be cut-out, removed, or eliminated, thus reducing material costs. 
     While the invention has been shown and described in a preferred embodiment exemplified by an accumulator configured for over-accumulation, the invention can be equally applied to an accumulation configured for under-accumulation. 
     It can therefore be seen that the present invention provides a novel accumulator apparatus and method. It is also seen that the present invention provides an accumulator apparatus and method that reduces or eliminates sheet mis-registration and provides for clean folds, no jamming, and minimal machine stoppages and paper damage. 
     It will be understood that various details of the invention may be changed without departing from the scope of the invention. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation, as the invention is defined by the following appended claims.