Sheet stacking equipment

Abstract

Equipment for stacking sheets comprises a stack support and a plurality of motor-driven conveyor belts having lower branches above the stack support for dragging incoming sheets by suction and depositing the sheets onto the stack support or already stacked sheets. The equipment includes a stopping member, a sensing device for sensing the height of the stacked sheets, a compensation mechanism for adjusting the height of the stack support, and an electronic control unit. The sensing device comprises sensing rollers arranged between the conveyor belts and cooperating with the sheets in sensing areas, sensing supports rotatably supporting the sensing rollers and being individually movable, intermediate elements associated with the sensing supports, and a rotatable common shaft. The sensing rollers lift according to the sheets’ thickness, causing displacement of the intermediate elements and rotation of the common shaft. The sensing device informs the electronic control unit for controlling the compensation mechanism.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Italian Application No. 102025000006120 filed on March 25, 2025, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The present invention generally to sheet processing systems and, more particularly, to a sheet stacking equipment employing suction-driven conveying belts for high-speed sheet handling and alignment.

[0003] More specifically, the invention relates to an equipment for stacking sheets comprising a stack support for vertically stacked sheets, a plurality of elongated conveyor belts having lower branches arranged above the stack support. The conveyor belts are motor driven for dragging incoming sheets by suction via said lower branches and for depositing the sheets onto the stack support or onto already stacked sheets. The equipment further comprises a stopping member for the incoming sheets, a sensing device for sensing the height of the stacked sheets, and a compensation mechanism for adjusting the height of the stack support as a function of the stacked sheets and an electronic control unit.BACKGROUND

[0004] Equipment of this type is disclosed in the European Patent EP4 363234 of the Applicant TECNAU S.r.l., of which the present invention represents a substantial improvement.

[0005] In the TECNAU patent, the compensation mechanism for adjusting the height of the stack support includes a pressure beam that acts on the stack being formed, providing stabilization and enabling the measurement of the stack height required by the compensation mechanism.

[0006] Stacking equipment using the structure described above is fast and reliable, and is capable of handling large sheets having different stiffness and smoothness characteristics, particularly sheets of medium-high weights. Conversely, when very light sheets or certain types of sheets are processed, reliability and stack quality issues may arise due to the action of the pressure beam and to the adjustment and operation of the compensation mechanism.SUMMARY

[0007] An object of the present invention is therefore to provide stacking equipment with suction conveyor belts that can be used reliably at high speed with sheets having widely varying characteristics, including sheets of medium or low weight.

[0008] According to this object, the sheet stacking equipment further comprises a series of sensing rollers interposed between the lower branches of the conveyor belts close to the stopping member, configured for cooperating with the stacking sheets in corresponding sensing areas; a series of sensing supports rotatably supporting said sensing rollers, said sensing supports being individually movable; a series of intermediate elements, arranged above the sensing rollers and configured for cooperating with said sensing supports; a common shaft angularly fixing the intermediate supports and being rotatable; and spring means configured for applying a tensioning action to the sensing supports via the common shaft and the intermediate elements so as to enable sensing of the sensing areas by the sensing rollers. The sensing rollers and the respective sensing supports are liftable from the stacking sheet according to the thicknesses of the sheets in the sensing area; the intermediate elements are displaceable by the sensing supports with rotation of the common shaft in response to the lifting of the sensing rollers; and the sensing device provides the electronic control unit with information for controlling the compensation mechanism in response to rotation of the common shaft determined by greater lifting of the sensing rollers.DESCRIPTION OF THE DRAWINGS

[0009] The features of the invention will become clear from the following description, given by way of non-limiting example with the aid of the attached drawings, in which:

[0010] FIG. 1 represents a schematic perspective view, conventionally front, of sheet stacking equipment according to the invention;

[0011] FIG. 2 is a partial side section of the equipment of FIG. 1;

[0012] FIG. 2a shows some details, on an enlarged scale, of components of FIG. 2;

[0013] FIG. 3 represents a schematic top perspective view of some functional units of the equipment of FIG. 1;

[0014] FIG. 4 is a schematic bottom perspective view of the functional units of FIG. 3;

[0015] FIGS. 5a and 5b show some parts of FIG. 2, on an enlarged scale;

[0016] FIG. 6 is a schematic exploded view of some components of FIG. 3;

[0017] FIGS. 6a, 6b and 6c show some details of the components of FIG. 6;

[0018] FIGS. 7 and 7a are further schematic views of some components of FIG. 3;

[0019] FIG. 7b is a schematic bottom view of some components of FIG. 4;

[0020] FIGS. 8, 8a, 8b and 8c show some components of the equipment of FIG. 2, on an enlarged scale;

[0021] FIG. 9 represents parts of FIG. 8 during a calibration phase;

[0022] FIG. 10 represents a schematic top perspective view of further functional units of the equipment of FIG. 1 in a given operating condition;

[0023] FIG. 11 shows the units of FIG. 10 in another operating condition; and

[0024] FIG. 12 shows components of FIG. 2 in another operating condition.GENERAL DESCRIPTION

[0025] With reference to FIGS. 1 and 2, a sheet stacking equipment, indicated as 31, receives paper sheets 32 at the front from external apparatus along a direction “F”. The stacked sheets are sent, as a stack or pack 33, through an output gate “OG” at the rear to an external processing apparatus by means of a conveyor belt “CB”.

[0026] The stacking equipment 31 is of the type indicated as 21 in the aforementioned patent EP 4 363 234, hereinafter “Patent”, which is incorporated herein by reference.

[0027] In summary, the stacking equipment 31 includes, at the front, an alignment section 34, at the rear a stacking and delivery section 36, and comprises an electronic control unit 37, a push-button panel 38, a control panel “CP”, a compressed-air generator 39 and sensor elements (not shown) arranged along the sheet path.

[0028] The alignment section 34, similar to the section 31 of the Patent, aligns the sheets 32 on a respective receiving surface and forwards them toward the stacking and delivery section 36.

[0029] The stacking and delivery section 36 consists of a transport and deposition unit 41, similar to unit 41 of the Patent, adjacent to the alignment section 34, and an accumulation and delivery unit 42, similar to unit 42 of the Patent, arranged below the unit 41.

[0030] As regards the present invention, the alignment section 34 comprises a series of alignment rollers 43 that align the edges of the sheets 32, even when side-by-side. The incoming sheets are then forwarded along the direction “F”, with suitable spacing between sheets, on a receiving surface, horizontal in use, toward the stacking and delivery section 36.

[0031] The transport and deposition unit 41 comprises input rollers 51 and conveying belts 52 for receiving and positioning incoming sheets above the stack 33 along a transport surface “TS”. The accumulation and delivery unit 42 in turn comprises a stack support 53 and a compensation mechanism 54, similar to stack support 46 and compensation mechanism 47 of the Patent.

[0032] The stack support 53 as the stack support of the Patent receives the sheets being stacked and forwards the stack 33 toward the conveyor belt “CB”, while the compensation mechanism 54 vertically moves the support 53 depending on the stacked sheets. The accumulation and delivery unit 42 may also forward the received sheets 32, without stacking, through a rear service opening “DTG”, substantially aligned with the transport surface “TS”.

[0033] In the transport and deposition unit 41, the input rollers 51 (FIGS. 2, 5a and 5b) include a driving roller 56 and a pressure roller 57 engaging each other on an introduction surface coplanar with the receiving surface of the alignment section 34.

[0034] The driving roller 56 and the pressure roller 57 are rotatably mounted on a frame 58 of the unit 41 and are driven through belts and pulleys by a feed motor 59 controlled by the electronic unit 37 to advance the sheets 32 in the direction “F”.

[0035] The conveying belts 52 extend horizontally and have respective upper branches 61 and lower branches generally indicated as 62. The lower branches are positioned above the stack support 53 and define, with their outer surface, the transport surface “TS” for the incoming sheets 32, horizontal in use and located below the introduction surface between the rollers 56 and 57.

[0036] The conveying belts 52 are longitudinally holed and coupled with one or more transverse ducts 69 arranged above the lower branches 62. Each duct 69 is connected at its upper portion to a series of suction fans 71. On their lower surfaces the ducts 69 have belt-guiding slots with suction openings adapted to exert a suction action on the sheets 32.

[0037] The conveying belts 52 are tensioned, through suitable guides, by the driving roller 56, by front rollers 72 and 73 respectively upper and lower, and by rear rollers 74 and 76 respectively upper and lower, rotatably mounted on the frame 58. The front rollers 72 and 73 deviate upward and downward the belts 52 engaged by roller 56, while rollers 74 together with rollers 72 define the upper branches 61 horizontally.

[0038] In particular, the belt stretches between the input rollers 51 and the front rollers 72 are inclined downward and guide the sheets 32 emerging from rollers 51 toward the transport surface “TS”. The rear rollers 76 together with the front rollers 73 define the lower branches 62 forming the conveying surface “TS”. Return rollers 77 are also provided for tensioning the belts 52, rotatable on the frame 58 in an intermediate position between the rollers 74 and 76.

[0039] The upper branches 61 and lower branches 62 of the belts 52 are vertically spaced sufficiently to accommodate the ducts 69 with fans 71 and other components of the transport and deposition unit 41.

[0040] Conveniently, downstream of the input rollers 51 spring leaves 78 and a compressed-air nozzle 79 connected, via a corresponding solenoid valve, to the compressed-air generator 39 are provided. The spring leaves 78 and the nozzle 79, when activated with air jets, act on the downward inclined stretches of belts 52 to facilitate detachment of incoming sheets from the belts together with their release from the input rollers 51.

[0041] In a known manner, the guides for conveying the belts 52 are formed on the lateral surface of hollow cylinders corresponding to the numbering indicated. The hollow cylinders are rotatable through bearings on corresponding shafts mounted on the frame 58. These guides have a slightly convex (crowned) profile producing a self-centering effect on the moving belts 52.

[0042] By action of the feed motor 59 and through the driving roller 56, the conveying belts 52 drag the incoming sheets 32 by adhesion due to suction along the lower branches 62 and deposit them onto the stack support 53 or onto the last sheet of the forming stack 33.Functional Block and Stopping Member

[0043] The stacking equipment 31 comprises, in the transport and deposition unit 41, a functional block 81 similar to the functional block 50 of the Patent, on which a corresponding stopping member 82 for the incoming sheets 32 is mounted.

[0044] The functional block 81 also supports a sensing device 83 for the last deposited sheet of the stack, including a series of sensing rollers 84 and an electronic sensor 85.

[0045] The block 81 (FIGS. 2, 3, 5b and 7) comprises a transverse flat bar 86, two side members 87r and 87l at the sides of the bar 86, and a transverse profile 88.

[0046] The bar 86 supports the stopping member 82, while the profile 88 supports the sensing rollers 84 and is mounted in front of the bar 86.

[0047] The side members 87r and 87l are slidably coupled and lockable with two lateral guides 89r and 89l, allowing the stopping member 82 to be positioned at a distance from the input rollers 51 that exceeds the length of the sheets 32.

[0048] One or more ducts (69), the number of which depends on the length of the sheets to be stacked, are mounted on sides that slide along the lateral guides (89r, 89l) and are selectively positionable at varying distances from the input rollers (51) based on said sheet length.

[0049] The positioning of the block 81, and the ducts 69 may be performed manually or by means of motors, optionally controlled based on the sensed length of the sheets.

[0050] To avoid the problems of known stacking equipment, the equipment 31 adopts innovative and effective solutions for the stopping member 82 and for control of the compensation mechanism 54.

[0051] Conveniently, the stacking equipment 31 provides a continuous stop profile for the stopping member 82 and deviation means 90 for the lower branches of the belts carried by the functional block 81 so as to form, above the conveying surface “TS”, an accommodating space for the stopping member 82.

[0052] Specifically, the deviation means 90 comprise intermediate rollers 91 (FIGS. 2, 5b, 8), deviation rollers 92 and realignment rollers 93 guiding the lower branches 62 of the belts 52. The rollers 91, 92 and 93 are rotatably mounted between the side members 87r and 87l of the functional block 81 and form a loop in the belts 52 creating an accommodating space 94 for the stopping member 82.

[0053] The front lower rollers 73 (fixed) and the intermediate rollers 91 (movable) guide an active section 95 of the lower branches 62 along the conveying surface “TS” for sheet dragging. The deviation rollers 92 are arranged above the intermediate rollers 91 and guide, together with the rollers 91, an upward deviated section 96 of the lower branches forming downstream and near rollers 91 the accommodating space 94 above the stack support 53.

[0054] The realignment rollers 93 are arranged at the same height as the intermediate rollers 91 and guide, together with the deviation rollers 92, a downward deviated section 97 of the lower branches. Finally, the realignment rollers 93 together with the rear rollers 76 guide a terminal section 98 of the lower branches 62 along the conveying surface “TS”. In detail, the deviation rollers 92 are positioned in a median area between the intermediate rollers 91 and the realignment rollers 93, determining a substantially inverted-U section of the loop delimiting the accommodating space 94.

[0055] The stopping member 82 comprises a plate 99 with a transverse section 101 arranged adjacent and downstream of the intermediate guide rollers 91, inside the accommodating space 94, upstream of the bar 86 and projecting downward from the conveying surface “TS”. The section 101 is intended to stop the moving sheets 32 and define a vertical alignment surface “AS” for the forming stack 33.

[0056] During the stacking process, the sheets 32 advance by combined action of the input rollers 51 and the conveying belts 52. However, the sheets leave the rollers 51 before their leading edges contact the transverse section 101, and movement up to the stop is ensured solely by the conveying belts 52 through adhesion.

[0057] Advantageously, the transverse section 101 has a continuous profile acting as an abutment for the leading edge of the sheets 32 being stacked.

[0058] The continuous stop profile solution avoids the problems associated with the comb-type stop structure of the Patent. In particular frontal damage, especially at high operating speeds, and the impossibility of handling light or very light paper (<60 gsm) due to stacking jams even at low speeds.

[0059] The intermediate guide rollers 91 (FIGS. 7, 7a, 7b, 8, and 8a) consist of pulleys 102, which support the belts 52 and project from a shaft 103 rotatable between the side members 87r and 87l of the functional block 81. In turn, the transverse profile 88 has a substantially “L”-shaped section and features a lower surface with a rounded front edge, which serves as a sliding surface for the lower branches of the belts, and longitudinal extensions 104, comb-shaped, at the sides of the pulleys 102.

[0060] The longitudinal extensions 104 function as guides for the leading edges of incoming sheets and, when abutting, up to the cross-section 101 of the stopping member 82. Conveniently, the longitudinal extensions 104 are inclined downward to gradually bring the leading edges of the sheets being stacked closer to the stack 33 near the stop.

[0061] Analogous to the equipment 21 of the Patent, the sheet-stacking equipment 31 also allows the formation of bundles with both regular blocks and staggered blocks.

[0062] To this end, the equipment 31 includes an offset stop 111, mounted in the accommodating space 94, and an offset actuator 112, for example of the electro-pneumatic type. The offset stop 111 has a cross-section 113, also with a substantially continuous profile, positioned behind the cross-section 101 of the stopping member 82 along direction “F”. The stopping member 82, with its cross-section 101, can be lifted by the offset actuator 112 to stop the sheets being stacked against the cross-section 113 of the offset stop 111 for a staggered stack surface relative to the alignment surface “AP”.

[0063] In detail, the plate 99 of the stopping member 82 is slidably mounted via guides 114 (FIGS. 6, 7 and 8), vertical in use, fixed to a front surface of the transverse bar 86. The offset stop 111 includes a crossbeam positioned behind the bar 86 and can be lifted by a lever 116 when the equipment 31 is set to transfer sheets 32 without stacking.

[0064] Conveniently, the cross-section 101 of the stopping member 82 has an inclined lower surface. This surface can be aligned with the lower surfaces of the longitudinal extensions 104 when the stopping member 82 is lifted by the offset actuator 112, enabling smooth stacking even for the formation of staggered blocks.

[0065] In the stacking equipment 31, the sensor device 83 (FIGS. 2, 5b, and 8c) is linked to the compensation mechanism 54 to ensure optimal conditions for stacking sheets regardless of the number of sheets already stacked. Specifically, the distance between the transport surface “TS” and the last sheet of the forming stack 33 is maintained constant in an optimized manner.Stack Height Compensation

[0066] According to another feature of the invention, in the sensor device 83, the sensing rollers 84 (FIGS. 5b, 6, 6b, 8, 8a) are arranged transversely between the lower branches 62 of the belts and are rotatably mounted on inverted U-shaped bridge supports 121. The bridge supports 121 are pivoted on pins 122 mounted via sensing blocks 123 on the transverse profile 88 and feature an upper part 124 above the rollers 84.

[0067] The sensing rollers 84 protrude with their lower sectors through corresponding windows 126 from the lower surface of the profile 88 (FIGS. 6b, 7b and 8a,) and face corresponding sheet sensing areas in the stack. A series of sensing springs, constituted by torsion springs 127 mounted on the pins 122 act on the bridge supports 121 to apply individual sensing pressure of the rollers 84 on the stack, and at rest, against end-of-travel stops 128.

[0068] A series of counter rollers 129, rotatable on intermediate supports 131, are arranged above the sensing rollers 84. The supports 131 are fixed but adjustable in angle via grub screws 132 on a common shaft 133. The shaft 133 is rotatably mounted on the profile 88 via supports 134 and serves as a mounting for two torsion springs 136 that push the counter rollers 129 against the upper part 124 of the bridge supports 121.

[0069] The transverse profile 88, together with the sensing rollers 84, the counter rollers 129, the common shaft 133, and associated parts, constitutes a sensing assembly that can be easily removed from the functional block 81 for maintenance via right and left knobs 137r and 137l securing the ends of the profile 88 to the side members 87r and 87l of the functional block 81.

[0070] On a setup phase of the stacking equipment 31, by means of a specific tool, the end-of-travel stops 1281 are adjusted so that the sensing rollers 84 are all aligned. Furthemore, the angular positions of the intermediate supports 131 is adjusted so that the counter rollers 129 are in contact with the upper parts 124 of the bridge supports 121.

[0071] During stacking, the sensing rollers 84 can be displaced upward by the sheet being stacked depending on its thickness (0.07–0.5 mm) in the sensing area. This displacement is transmitted to the counter-rollers 129 via the upper part 124 of the bridge supports 121, triggering the rotation of the common shaft 133 through the intermediate supports 131 and the upward lifting of the vane 141. Should a sheet 32 have a greater thickness in a specific sensing area, the rotation of the common shaft 133 is driven by the maximum lifting of the sensing rollers 84 operating on that thicker area.

[0072] The sensing action of the sensing rollers 84 on the sheets being stacked is performed by the combined force of the torsion springs 127 on the sensing rollers 84 and the torsion spring 136 on the common shaft 133, acting via the counter-rollers 129. The torsion springs 127 serve two functions: first, they maintain stable contact between the sensing rollers 84 and the sheets 32 in the thinner areas; second, they hold the rollers 84 against their respective end-of-travel stops 128 in the absence of sheets or their spacing.

[0073] In practice, the sheets 32 may exhibit imperfections (swelling, creases, ink variations, etc.) which the sensing rollers 84 detect by lifting. The sensing roller 84 that encounters the maximum imperfection lifts higher than the other and, via upper part 124 of the bridge supports 121, further rises the overlying counter-roller 129. This causes a further rotation of the shaft 133 and the lifting of the vane 141. Meanwhile, the other counter-rollers detach from the bridge parts 124 that remain lower, while the respective sensing rollers 84 are kept in contact with the sheets by the action of the springs 127.

[0074] In the sensor device 83, the electronic sensor 85 (FIG. 8c) is a laser illuminator / detector similar to that of the Patent. In the stacking equipment 31, the target area of the sensor device includes a vane 141 fixed on the shaft 133, which oscillates horizontally in response to movements of the sensing rollers 84 caused by incoming sheets and the corresponding movements of the counter rollers 129.

[0075] Advantageously, the accumulation and delivery assembly 42, in addition to the stack support 53 (FIGS. 2, 10, 11 and 12), includes a starting support 151 to ensure optimal stacking of the first sheets of the stack 33 and to accelerate transitions between the delivery of the completed pack and subsequent stacking.

[0076] The stack support 53 comprises, in summary, a frame 152 beneath the transport and deposit assembly 41, two transverse shafts 153 and 154, respectively front and rear, rotatably supported by the frame 152, a plurality of functional and delivery blocks 156 carried by the frame 152, and a delivery motor 157 for the shafts 153 and 154.

[0077] The functional and delivery blocks 156 (FIG. 2a) have an elongated parallelepiped shape, spaced transversely from one another, and each comprises a spar 158, two terminal pulleys 159 and 160 keyed on the shafts 153 and 154, intermediate idler rollers 161, and an elongated delivery belt 162 stretched between the pulleys 159 and 160. The pulleys 159 and 160 of each block 156 have upper sectors tangent to the upper surfaces of the spar 158. The upper run of the belt 162 rests on the upper surface of the spar 158, while the lower run is deflected upward by the idler rollers 161.

[0078] The assembly of the upper runs of the delivery belts 162 forms a supporting surface “BS” for the forming stack 33, with support by the spars 158. The belts 162 are driven by the motor 157 in direction “F”, sliding over the upper surfaces of the spars 158 during delivery by the stacking equipment 31.

[0079] The stack support 53 can move vertically via a pair of vertical guides 163l and 163r between a reference position “RP” and a delivery position “DP” (FIG. 9). The reference position “RP”, high, corresponds to an operational condition following an initial phase of no sheets. The delivery position “DP” is the lowest position of the stack support 53, where the surface “BS” is substantially coplanar with the lower edge of the output gate “OG” and with the conveyor belt “CB”.

[0080] A panel 164 is mounted vertically downward on a rear part of the frame 152. The output gate “OG” is shielded by the panel 164 when the stack support 53 is in the reference position “RP” and is clear when the support 53 is in the delivery position “DP”.

[0081] For the condition of sheet transfer without stacking, the stack support 53 can also be moved to a high extra-stroke position where the supporting surface “BS” is tangent to the lower branches 62 of the conveyor belts, coplanar with the “TS” surface in correspondence of the rear service opening “DTG”.

[0082] As previously reported, depending on the number of sheets stacked, the compensation mechanism 54 lowers the stack support 53 from the reached position to the delivery position “DP” upon completion of the stack 33. In this position “DP”, the upper runs of the delivery belts 162 are moved by the delivery motor 157 to forward the stack 33, through the output gate “OG”, onto the conveyor belt “CB” for subsequent processing.

[0083] The compensation mechanism 54 comprises a pair of ball-screw assemblies with splined shafts 166 and 167 and corresponding nuts 168 and 169. The nuts 168 and 169 are fixed to the sides of the frame 152, while the splined shafts 166 and 167 are rotatably supported, with a lower end, on a transverse plate 171 and are driven in rotation, via belts and pulleys, by a compensation motor 172, which is also controlled by the electronic unit 37.

[0084] The starting support 151 includes a frame 179 positioned beneath the alignment section 34, a multi-fork support 181 mounted for sliding on the frame 179, a series of forks 182 mounted on the multi-fork support, an actuation mechanism 183 for the multi-fork support, and a starting compensation mechanism 184 for the frame 179.

[0085] The forks 182 can be inserted between the functional and delivery blocks 156 and are actuated by the fork actuation mechanism 183, activated by the electronic unit 37, to move the forks 182 from a retracted configuration to an inserted configuration. In the retracted configuration, the forks are closed on the frame 179 below the alignment section 34. In the inserted configuration, the forks protrude from the frame 179 and can be inserted between the functional and delivery blocks 156 of the stack support 53.

[0086] In summary, the fork actuation mechanism 183 comprises two pulleys 187 and 188 rotatably supported, centrally, at the front and rear of the frame 179, a displacement belt 189 stretched between pulleys 187 and 188, and a fork actuation motor 191. The multi-fork support 181 is engaged with the upper run of the displacement belt 189 for moving the forks 182 between the retracted and inserted configurations.

[0087] The starting compensation mechanism 184 is provided to adjust the height of the frame 179 with the multi-fork support according to the height of the sheets being stacked. This mechanism 184, similar to the compensation mechanism 54 and comprising a starting compensation motor 192 and a screw-and-nut conversion mechanism, is not described here for the sake of brevity.

[0088] During a startup phase, the stack support 53 is in the reference position “RP” and the forks 182 are in the inserted configuration, above the upper runs of the delivery belts 162. The forks 182 thus form a temporary support replacing the belts 162, with a surface optimized for stacking the first sheets of the stack.

[0089] For a predetermined stack height, e.g., 10 sheets, the forks 182 are slightly lower than the supporting surface “BS” and the forming stack 33 rests on the delivery belts 162. The electronic unit 37 can activate the actuation mechanism 183 to move the forks 182 to the retracted configuration and can activate the starting compensation mechanism 184 to adjust the height of the stack support 53 during operation based on the number of sheets stacked beyond the predetermined height.

[0090] According to a feature of the invention, the stacking equipment 31 provides for the stacking of the sheets a fixed reference represented by a “machine zero” level and software-based control for the height compensation of the stack support 53 or the starting support 151. The “machine zero” level corresponds to the one of a transport surface “TS” of the sheets 32 in the area of tangency with the conveyor belts 52 guided by the intermediate rollers 91. The software control, in turn, allows adjustment of the height compensation of the stack support 53 or the starting support 151 based on operational experience of the equipment 31.

[0091] Upon request, the sensor device 83 can be calibrated using a calibration tool (master) 196 (FIG. 9) to correctly set the initial reading value for the “machine zero” level.

[0092] The calibration tool 196 comprises an L-shaped profile in which a vertical part 197 is comb-like and a base part 198 is flat. The vertical part 197 can be inserted between the conveyor belts 52 and coupled with the front part of the profile 88, while the base part 198 lifts the sensing rollers 84 to the “machine zero” level, allowing the operator to correctly set the sensor zero. Once the calibration tool 196 is removed, the sensing rollers 84 return to their initial position against the end-of-travel stops 128, performing a displacement “X” that will correspond to the initial reading value of the sensor device 83.

[0093] The electronic sensor 85, reading the target area constituted by the vane 141, will therefore measure a deviation value “X” relative to another previously measured value. The measured values are then used to correct, via software, the descent of the support on which the stack is being formed, thus closing the process control loop.

[0094] More specifically, by means of a parameter that can be set from the panel “CP”, depending on the paper thickness, the operator sets the “theoretical pitch” for the descent of the stack support 53 and starting support 151, for example, 0.15 mm. The operator also sets the “theoretical reference position” for the sensor reading: “zero”, “negative”, or “positive” values. For instance, if the set value is “zero”, the support will descend so that the sensor 85 consistently measures values near zero, thus keeping the stack composition close to “machine zero” for an average compression of the stack 33 being formed.

[0095] If the set value is greater than zero, the support will descend while attempting to maintain the sensor measurement at this value, resulting in a more compressed stack (position of the sensing rollers 84 higher than “machine zero”). If the set value is less than zero, the support will descend while attempting to maintain the sensor measurement at this value, resulting in a less compressed stack (position of the sensing rollers 84 lower than “machine zero”).

[0096] During stacking, the software also performs a sampling every “n” values measured by the sensor 85 and calculates an average. The average value is then used to correct the “theoretical pitch” set by the operator. The resulting “average corrected pitch” will allow for an optimal descent of the stack support or starting support to keep the sensor reading close to the set value. Consequently, this descent will be the one expected for the last incoming sheet on the stack being formed.

[0097] The “average corrected pitch” is also displayed on the panel for the operator, who can thus have visual feedback of the actual pitch currently being applied by the equipment 31.

[0098] To accommodate the multiple types of paper and formats processable, the values set by the operator can be saved in reusable recipes to ensure repeatability of the operations.

[0099] The operation of the equipment 31 for sheet stacking is as follows:

[0100] Depending on the longitudinal dimensions of the sheets 32 to be stacked (FIGS. 1 and 2), the operator positions the functional block 81 and the duct or ducts 69 at programmed distances from the input rollers 51. Through the control panel “CP”, the operator also sets data on the number of sheets 32 to stack, the number of sheets per block for offset stacking (if required), the characteristics of the sheets, the “theoretical pitch” and the “average corrected pitch”. The operator can also set the number of sheets to stack on the forks 182 during the start phase and thus the reference position “RP”.

[0101] In an initial phase, the stack support 53 (FIG. 3) is empty and in the reference position “RP”, and the output gate “OG” is blocked by the panel 164. The starting support 151 is in a high position, at the “machine zero” condition, with the forks 182 in the inserted configuration, interposed between the blocks 156 of the stack support 53, to receive the incoming sheets in stacking.

[0102] The electronic unit 37 activates the feed motor 59, rotating the input rollers 51 with movement of the belts 52 at a conveying speed slightly higher than the sheet feed speed.

[0103] At the exit from the alignment section 34, the input rollers 51 advance the sheet 32 positively along the inclined belt sections. The sheet is bent and guided downward until its leading edge meets the forks 182 of the starting support 151. The sheet is then bent again and guided horizontally by the action of the input rollers 51 and with the contribution of the lower branches 62 of the belts 52.

[0104] The first sheet 32 continues its travel until its leading edge passes the position of the duct or first duct 69. Here, the sheet is lifted against the branches 62 of the belts 52 by suction from the duct 69 through the openings in the guide notches and through the holes in the belts 52. The sheet continues to advance through the passage and suction of successive parts in front of the openings and the combined positive drag action of the input rollers 51.

[0105] If the equipment 31 includes multiple ducts 69, after the first duct lifts the sheet 32, adhesion to the belts 52 is perfected as the sheet passes in front of the other ducts.

[0106] After the trailing edge leaves the rollers 51, the sheet 32 continues to be dragged solely by the belts 52, with adhesion ensured by the duct or ducts 69, and tends to return to a flat configuration, facilitated by the elastic separating tabs 69 and compressed air jets from the nozzle 79.

[0107] As it moves along the belts 52, the first sheet 32 encounters its leading edge with the sensing rollers 84, which are raised depending on the sheet thickness, lifting the vane 141. The sheet is finally stopped when it meets the cross-section 101 of the stopping member 82, with slippage of the belts 52 on the sheet. While waiting for another sheet 32 to be stacked, the feed motor 59 remains activated, keeping the input rollers 51 and the belts 52 in motion.

[0108] The introduction of the first sheet 32 into the transport and deposit group 41 triggers, by command of the electronic unit 37, the start compensation motor 192 to lower the starting support 151 by an amount corresponding to the “theoretical pitch” and the “theoretical position”, in response to feedback from the laser illuminator / detector 85 on the position of the target area 141.

[0109] A new sheet 32 entering from the input rollers 51 is also bent and guided downward by the input rollers 51 and the inclined belt sections, but its leading edge now meets the previous sheet. Due to the pushing action from the input rollers 51, the inclined belt sections, and the insertion roller 73, the new sheet is bent and guided horizontally, inserting itself between the lower branches 62 of the belts and the portions of the previous sheet still adhering to the branches 62.

[0110] The new sheet 32 continues its travel above the previous sheet until its leading edge reaches the duct or the first duct 69, coming into contact with its lower surface. The portion of the previous sheet, no longer held by the suction of the duct falls onto the surface of the forks 182, while the new sheet adheres to the branches 62 of the belts and is dragged by them. The new sheet then continues to advance due to the passage and suction of successive parts in front of other ducts 69, while the previous sheet progressively settles onto the forks 182 as the first sheet of the stack 33.

[0111] The new sheet 32 continues its movement solely by means of the conveyor belts 52 due to adhesion ensured by the duct or ducts 69 after its trailing edge leaves the rollers 51. The new sheet tends to return to a flat configuration and rests its trailing edge on the previous sheet, facilitated by the spring leaves 78 and compressed air jets. In sequence, the new sheet lifts the sensing rollers 84 depending on its thickness, with the consequent lifting of the vane 141. The sheet is finally stopped when its leading edge contacts the cross-section 101 of the stopping member 82, with the moving belts 52 slipping on the sheet.

[0112] The completion of the introduction of the new sheet 32 into the transport and deposition unit 41 triggers again the compensation motor 192, under the control of the electronic unit 37 and feedback from the sensor device 83, lowering the starting support 151 by an amount corresponding to the set data..

[0113] Stacking of subsequent sheets occurs sequentially as previously described for the second sheet, with the progressive formation of the stack 33 and any corrections to the lowering of the starting support 151 based on the “average corrected pitch”.

[0114] Upon reaching the number of sheets planned for the stack height at start-up, the forks 182 are positioned to a level slightly lower than the surface “BS”, and the forming stack 33 rests on the delivery belts 162. The electronic unit 37 then activates the fork actuation motor 191 to move the forks into their retracted configuration, thereby leaving the stack support 53 free to receive further sheets being stacked.

[0115] The forming stack 33 now rests on the supporting surface “BS” constituted by the delivery belts 162, and the stacking process of sheets 32 continues as previously described for the support on the forks 182, but with the height compensation of the stack support 53 entrusted to the compensation mechanism 54. Specifically, for the new incoming sheets 32, the electronic unit 37 activates the compensation motor 172, lowering the stack support 53 according to the set data and corrections based on the “average corrected pitch”.

[0116] In the event that the offset option is provided, after the set number of sheets forming each block has been stacked, the electronic unit 37 activates the offset actuator 112, lifting the stopping member 82. The offset stop 111 replaces the transverse section 101, thereby determining the alignment plane for the staggered blocks.

[0117] During the stacking process, the continuous profiles of the transverse sections 101 or 113 of the stopping members 82 prevent the impact of incoming sheets 32 and the thrusts of the conveyor belt 52 from causing deformations of the leading edges or sheet curling, which could lead to overlapping and jamming upon the arrival of subsequent sheets.

[0118] In turn, the accurate detection of the thickness and imperfections of the sheet 32 being stacked prevents any undulations in the stacked sheet from causing errors in the height position of the starting support 151, avoiding other jamming risks for the new sheet to be stacked. Furthermore, the accurate detection of thicknesses and imperfections of the sheets being stacked prevents any undulations on the stacked sheet from causing height positioning errors of the starting support 151, thus avoiding further risks of jamming for the new sheet to be stacked.

[0119] Upon reaching the total number of sheets 32 to be stacked, the electronic unit 37 temporarily disables the input of new sheets and activates the compensation motor 172, moving the stack support 53 from the last stacking position to the delivery position “DP”. The supporting surface “BS” of the delivery belts 162 is coplanar with the conveyor belt “CB”, and the panel 164 is located below the output gate “OG”, uncovering it completely.

[0120] The electronic unit 37 then activates the delivery motor 157, moving the upper branches of the delivery belts 162 in the direction “F”, resulting in the subsequent conveyance of the stack 33 (FIG. 12) with the stacked sheets onto the conveyor belt “CB” for dispatch to the user equipment.

[0121] During this delivery phase, the electronic unit 37 activates the starting compensation mechanism 184 and the fork actuation mechanism 183, moving the starting support 151 to the “machine zero” condition, high, with the forks 182 in the retracted configuration, and re-enables the intake of new sheets for forming a new stack, thereby reducing dwell times.

[0122] Once the delivery of the stack 33 is completed, the electronic unit 37 stops the motor 157 and activates the compensation motor 172, with the rotation of the splined shafts (166 and 167) in the direction opposite to the lowering direction, lifting the stack support 53 to the reference position “RP” of FIG. 3 for the start of a new stacking operation, with the surface “BS” positioned below the forks 182.

[0123] In the specific condition of sheet forwarding without any stacking, the operator lifts the stopping member 82 and the offset stop 111 using the lifting lever 116 and inputs an exclusion command, via the control panel, to the electronic unit 37, with the activation of the compensation mechanism 54 and the delivery motor 157. The starting support remains high, but with the forks 182 in the retracted configuration, below the alignment section 34.

[0124] The compensation mechanism 54 lifts the stack support 53 to the extra-stroke position, with the supporting surface “BS” in a condition of tangency with the lower branches 62 of the conveyor belts 52 in correspondence of the rear service opening, while the delivery motor 157 moves the delivery belts 162.

[0125] The incoming sheets, after being deflected downward by the input rollers 51, are guided along the surface “TS” through the sequential action of the active section 95 (also with suction) and of the terminal section 98 of the lower branches 62 of the conveyor belts and by the upper branches of the delivery belts 162, up to the service opening “DTG”.

[0126] Naturally, without departing from the principle of the invention, the actuation forms and construction details of the sheet stacking equipment may be widely varied with respect to what has been described and illustrated by way of non-limiting example, without thereby departing from the scope of the present invention.

[0127] For instance, the accommodating space for the stopping member and for the offset stop can be realized by deflection means other than the intermediate rollers and the deviation rollers.

[0128] In the event that the forwarding without stacking is not required, the structure of the functional block and the path of the conveying belts can be simplified by providing only intermediate rollers and deviation rollers for the formation of the accommodating space. In this variant, the terminal section of the lower branches of the belts will be guided by rear rollers at the level of the upper part of the deviation rollers, without the possibility of forwarding sheets for transfer.

[0129] According to a variant, the sheet thickness control utilizes an equivalent structure where the torsion springs 127 are omitted, and the sensing action of sensing rollers 84 on sheets 32 is performed solely by the force of the torsion springs 136 or different springs acting on the common shaft 133.

[0130] In a further variant, the intermediate element for movement transmission between the sensing supports 121 and the common shaft 133 is achieved for example via a single rocker arm, featuring angular adjustment capability on the common shaft and a rounded terminal that cooperates with the upper part 124 of the corresponding sensing support 134.

Claims

1. An equipment for stacking sheets comprising a stack support for vertically stacked sheets, a plurality of elongated conveyor belts having lower branches arranged above the stack support, wherein the conveyor belts are motor driven for dragging incoming sheets by suction via said lower branches and for depositing the sheets onto the stack support or onto already stacked sheets, and wherein the equipment further comprises a stopping member for the incoming sheets, a sensing device for sensing the height of the stacked sheets, a compensation mechanism for adjusting the height of the stack support as a function of the stacked sheets and an electronic control unit, and wherein the sensing device comprises:a series of sensing rollers interposed between the lower branches of the conveyor belts close to the stopping member, configured for cooperating with the stacking sheets in corresponding sensing areas;a series of sensing supports rotatably supporting said sensing rollers, said sensing supports being individually movable;a series of intermediate elements, arranged above the sensing rollers and configured for cooperating with said sensing supports;a common shaft angularly fixing the intermediate supports and being rotatable; andspring means configured for applying a tensioning action to the sensing supports via the common shaft and the intermediate elements so as to enable sensing of the sensing areas by the sensing rollers, whereinthe sensing rollers and the respective sensing supports are liftable from the stacking sheet according to the thicknesses of the sheets in the sensing area,the intermediate elements are displaceable by the sensing supports with rotation of the common shaft in response to the lifting of the sensing rollers; and the sensing device provides the electronic control unit with information for controlling the compensation mechanism in response to rotation of the common shaft determined by greater lifting of the sensing rollers.

2. Equipment for stacking sheets according to claim 1, wherein the intermediate elements are angularly adjustable with respect to the common shaft to be, at rest, all in contact with an upper part of the sensing supports under the action of said spring means.

3. Equipment for stacking sheets according to claim 1, wherein the intermediate elements each comprise counter rollers with respective intermediate supports, wherein the counter rollers are rotatably supported by the intermediate supports while the intermediate supports are fixed on the common shaft.

4. Equipment for stacking sheets according to claim 1, further comprising sensing springs operating on said sensing support.

5. Equipment according to claim 4,wherein the sensing supports include inverted “U” shaped bridge supports, said bridge supports are pivotable on corresponding pins,wherein said sensing springs are constituted by torsion springs mounted on said pins, the intermediate elements comprise counter rollers with respective intermediate supports, andwherein the counter rollers are rotatably supported by the intermediate supports while the intermediate supports are fixed on the common shaft and are configured for cooperating with an upper part of said bridge supports.

6. Equipment for stacking sheets according to claim 1, wherein said spring means comprise torsion springs mounted on said common shaft.

7. Equipment for stacking sheets according to claim 1, further comprising a transverse profile supporting the sensing supports, the intermediate elements and the common shaft, forming a sensing assembly, wherein said sensing assembly is configured to be removable.

8. Equipment for stacking sheets according to claim 1,wherein said equipment provides a fixed reference for stacking the sheets as a “machine zero” level and a software control for the height compensation of the stack support;wherein the “machine zero” level corresponds to the one of a transport surface “TS” for the incoming sheets and the software control allows the height compensation of the stack support to be modified; andwherein the sensing device can be calibrated by means of a calibration tool for correctly setting an initial reading value for the “machine zero” level.

9. Equipment for stacking sheets according to claim 8, wherein a descent of the stack support for each incoming sheet is determined by a reference value which can be set according to the thickness of the sheets and by additive or subtractive correction values, resulting in a corresponding change in the compression degree of the stack.

10. Equipment for stacking sheets according to claim 9, wherein the current descent value is monitored to obtain an average value and wherein said average value is used to update the reference value.

11. Equipment according to claim 1, wherein the sensing device comprises a laser illuminator / detector and a target area, and the target area includes a vane rotationally connected with said common shaft.

12. Equipment for stacking sheets according to claim 1, further comprising input rollers for the incoming sheets to be stacked, a functional block for the stopping member and the sensing device, wherein said functional block is longitudinally movable for positioning the stopping member at a distance from the input rollers depending on the length of the sheets to be stacked.

13. Equipment for stacking sheets according to claim 12, further comprising deviation means for the lower branches of the belts carried by the functional block, wherein said deviation means are configured to form an accommodating space above a transport surface “TS” for the incoming sheets, upstream and adjacent to the stopping member, the stopping member is arranged in the accommodating space and has a cross-section projecting below a transport surface “TS” of the sheets for stopping the stacking sheets dragged by the belts and defining a vertical alignment surface of the stack, and wherein the cross-section of the stopping member has a continuous profile for contrasting a leading edge of the stacking sheets.

14. Equipment for stacking sheets according to claim 12, further comprising a transverse profile supporting the sensing rollers, the intermediate elements and the common shaft, forming a sensing assembly and wherein said sensing assembly is removably mounted on the functional block.

15. Stacking equipment according to claim 1, wherein the stack support comprises a plurality of elongated delivery belts supporting the stacking sheets and supports for said delivery belts, said equipment further comprising a multi-fork support, an actuation mechanism for said multi-fork support, and a starting compensation mechanism, wherein:the multi-fork support comprises a series of forks insertable between the supports of the delivery belts of the stack support;the actuation mechanism and the starting compensation mechanism are controlled by the electronic unit, in a start-up phase, for positioning said forks above and between the upper branches of the delivery belts so as to constitute a temporary support for the forming stack in place of the delivery belts;the starting compensation mechanism is provided for adjusting the height of the multi-fork support according to the stacked sheets until a predetermined stack height is reached wherein the forks are below the delivery belts; andupon reaching a predetermined stack height, with the forks below the delivery belts, the electronic unit controls the actuation mechanism for extracting the forks from the delivery belts and restores the control of the compensation mechanism for modifying the height of the stack support according to the stacked sheets beyond the predetermined stack height.

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