Patent Description:
More specifically, the invention relates to an equipment for stacking sheets comprising a stack support for sheets in vertical stacking, input rollers for introducing and feeding sheets along a given direction, a plurality of extended transport belts with lower branches disposed above the stack support, a compensation mechanism for modifying the height of the stack and wherein the transport belts are motorized for shifting entering sheets with the lower branches and depositing the sheets on the stack support or on stacked sheets.

Equipment of this type, for example represented in the <CIT> of Lasermax Roll System, are used for post-treatments of printed sheets.

<CIT> discloses another equipment for stacking paper sheets comprising an arrest member for the entering sheets, a pressing member for a forming stack, a sensor device for the height of a last sheet of the stack and an electronic control unit. The arrest member is designated for arresting and aligning sheets in stacking against a stack alignment surface. The pressing member operates on the last sheet of the stack with stabilization function and comprises a pressing cross member with a lower surface of contrast for the stack, and wherein the compensation mechanism is servoized to the sensor device, on control by the electronic unit, for maintaining constant the height of the last sheet of the stack from the reference surface, as for the introductory portion of claim <NUM>. The pressing cross member is formed by independent wheel units mounted on upper pivots and operating by gravity.

Typically, the transport belts cause the entering sheets to slide onto the last sheet of the forming stack until the arrest. For sheets of large size and of a particular nature, such as coated paper sheets to be superimposed on each other, problems arise due to the difference in smoothness existing between printed sheets and unprinted sheets. This can cause the formation of bulges, in particular in the arrest area, which prevent an orderly stacking and with risk of jamming, especially in the case of stacking equipment at high operating speed, for example of the order of <NUM>/min. Similar problems arise in the case of the use of uncoated sheets having different characteristics from sheet to sheet and/or to be stacked together with sheets of coated paper.

It is an object of the invention to provide a stacking equipment which can be used reliably, at high speed, with sheets of large dimensions and different characteristics of rigidity and smoothness.

According to this object, the lower surface of the pressing cross member defines longitudinal notches of guide for the transport belts and wherein the lower surface of the cross member further operates on the pressing area of the last sheet of the stack as for the characteristic portion of claim <NUM>.

According to another characteristic, the sheet stacking equipment comprises one or more ducts connected to a vacuum source, arranged transversally above the lower branches of the transport belts and with guide areas for the belt branches and a arrest member arranged downstream of the duct or ducts for arresting the entering and stacking sheets. The duct or ducts have openings in correspondence with the guide areas and the transport belts have longitudinal holes for ensuring a suction action on the entering sheets through said holes with traction by adherence of the sheets by the transport belts. In particular, the transport belts comprise a group of belts having a low coefficient of friction and a group of belts having a medium coefficient of friction.

The characteristics of the invention will become clear from the following description, given purely by way of non-limiting example, with reference to the appended drawings in which:.

With reference to <FIG>, <FIG> and <FIG>, the reference numeral <NUM> designates an equipment for stacking paper sheets <NUM> which includes a bodywork <NUM> and a frame with two sides <NUM> and <NUM>, a front with an input gate <NUM> of the bodywork <NUM> and a respective rear with an output gate <NUM>.

The stacking equipment <NUM>, through the gate <NUM>, receives the sheets <NUM> horizontally from an external feeding apparatus along a feed direction "F" and, after stacking, sends a stack <NUM> of superimposed sheets, through the gate <NUM>, to an external user apparatus for subsequent treatments.

According to a typical application, the paper sheets <NUM> are fed by a cutter "CM", while the stack <NUM> is delivered to a conveyor belt "CB" for delivery to the user apparatus.

The sheet stacking equipment <NUM> comprises an alignment section <NUM>, a stacking and delivering section <NUM>, respectively on the front and on the back, an electronic control unit <NUM>, a push-button panel <NUM> and sensor elements, not shown, arranged along the internal path of the sheets. The sensor elements are functionally connected to the electronic unit <NUM> for counting the sheets to be stacked and for detecting some operating conditions and anomalies. The equipment <NUM> further lodges, in a lower part, a vacuum pump <NUM> and, optionally, a compressed air generator <NUM> in case an external compressed air source is not available.

The equipment <NUM> is controlled by the feeding apparatus "CM", and the operating controls are carried out, for example, by means of a touch screen "CD" of the cutter "CM".

The alignment section <NUM> is disposed in an upper part of the bodywork <NUM> and has a front projecting part defining the input gate <NUM> and with a horizontal receiving surface for the sheets <NUM>. A series of alignment rollers <NUM>, mounted on a frame <NUM>, operate above the receiving surface to align, according to predetermined rules, the edges of the sheets <NUM>, and of side by side sheets. The aligned sheets <NUM> are then delivered, coplanar with the receiving surface, by a pair of delivery rollers <NUM> along the fed direction "F" toward the stacking and delivering section <NUM>, with adequate spacing between sheet and sheet.

The frame <NUM> is hinged on the side <NUM> of the equipment and has the possibility of opening for an easy access to the receiving surface. The alignment section <NUM> is functionally of a known type and, for simplicity, the operational description thereof is omitted here.

The stacking and delivering section <NUM> is constituted by a transport and storage group <NUM> adjacent to the alignment section <NUM> and an accumulation and delivery group <NUM> disposed below the group <NUM>. The transport and storage group <NUM> comprises input rollers <NUM> downstream of the delivery rollers <NUM> and transport belts <NUM> for receiving and positioning the entering sheets above the stack <NUM>. The accumulation and delivery group <NUM> includes a stack support <NUM> for receiving the sheets in stacking and a compensation mechanism <NUM> for vertically moving the stack support <NUM>.

In the transport and storage group <NUM> (<FIG>, <FIG>), the input rollers <NUM> are in mutual engagement on a horizontal geometric introduction plane "IP", coplanar with the receiving surface of the alignment section <NUM>. In particular, the input rollers <NUM> are driven through belts and pulleys by an introduction motor <NUM> controlled by the electronic unit <NUM> to advance in the feed direction "F" the sheets <NUM> emerging from the delivery rollers <NUM>.

The transport belts <NUM> are of the flat type, of an extended shape and present respective lower horizontal branches <NUM>, positioned in parallel above the stack support <NUM> and which define with their outer surface a transport surface "TS". The belts <NUM> are motorized for dragging the entering sheets with the lower branches <NUM> and depositing the sheets on the stack support <NUM> or on a last sheet of the stack <NUM> being formed, as will be described below.

According to the invention, the sheet stacking equipment <NUM> comprises in the transport and storage group <NUM> a functional block <NUM> which includes an arrest member <NUM> for the entering sheets <NUM>, a pressing member <NUM> for the stack <NUM> being formed, arranged upstream of the arrest member, and a sensing device <NUM> for the last sheet of the stack.

In particular, the functional block <NUM> (<FIG>, <FIG> and <FIG>) comprises a transversal support plate <NUM>, substantially vertical, on which the arrest member <NUM>, the pressing member <NUM> and the sensing device <NUM> are transversally mounted. The plate <NUM> is provided at the sides with two slides 54r and <NUM> which are coupled, in a sliding manner and possibility of locking, with two lateral guides 56r and <NUM> fixed on the frame of the equipment <NUM>. In this way, the arrest member <NUM> can be positioned according to the length of the sheets <NUM> to be stacked at a convenient distance from the input rollers <NUM>, greater than the length of the sheets <NUM>.

The arrest member <NUM> defines a vertical alignment plane "AP" of the stack <NUM> and it is designated for arresting the moving sheets <NUM> to be stacked. During the stacking process, the sheets <NUM> advance by the combined action of the input rollers <NUM> and the transport belts <NUM>. The sheets <NUM>, however, leave the rollers <NUM> before their leading edges come into contact with the arrest member <NUM>, while the shifting of the sheets before the arrest is ensured only by the transport belts <NUM>.

The pressing member <NUM> operates on the last sheet of the stack <NUM> with stabilizing function. In turn, the sensing device <NUM> is interlocked with the compensation mechanism <NUM> to ensure optimal conditions for stacking regardless of the number of stacked sheets. This, for example and in a conventional manner, by maintaining constant the height, indicated "H", between the introduction plane "IP" and the last sheet of the stack <NUM> or between the introduction plane "IP" and the surface of the stack support <NUM> in absence of sheets.

The input rollers <NUM> comprise in particular a driving roller <NUM> and a contrast roller <NUM>, which are arranged in a tangential condition above and below the plane "IP". The transport belts <NUM> are stretched between the driving roller <NUM>, a rear roller <NUM>, upper deflection rollers <NUM> and <NUM>, respectively front and rear, and a lower front deflection roller <NUM>.

The deflection rollers <NUM> and <NUM> form the upper branches, indicated by <NUM>, of the transport belts <NUM>, while the deflection roller <NUM> and the rear roller <NUM> form the lower branches <NUM> with the transport surface "TS". The branches <NUM> and the branches <NUM> are spaced apart so as to house mechanisms of the transport and storage group <NUM> including the pressing member <NUM> and the arrest member <NUM>. In detail, with respect to the feed direction "F", the deflection rollers <NUM> and <NUM> are arranged downstream of the driving roller <NUM>, while the deflection roller <NUM> is arranged upstream of the rear roller <NUM> and downstream of the arrest member <NUM>.

In operating conditions, the lower branches <NUM> of the transport belts <NUM> are arranged at a distance in height from the plane "IP" lower than the height "H", so as to leave a space "G" between the transport surface "TS" of the branches <NUM> and the stack support <NUM> or between the transport surface "TS" and the last sheet of the stack <NUM>. The space "G" is, for example, included between <NUM> and <NUM>, such as to allow an easy passage of the sheets <NUM> to be stacked. As above reported, in the accumulation and delivery assembly <NUM>, the compensation mechanism <NUM> regulates the height of the support <NUM> between a series of operating positions in which the height "H" is kept substantially constant. Consequently, also the space "G" between the transport surface "TS" and the last sheet of the stack <NUM> or the surface of the stack support, in absence of sheets is maintained constant.

The driving roller <NUM> (see <FIG> and <FIG>) defines, in a transversal direction, engagement seats for the transport belts <NUM>, which are alternated with support seats for driving rings <NUM> of friction dragging for the sheets <NUM>, and in which the engagement seats are for example made of elastomeric material. The contrast roller <NUM> is also made of elastomeric material.

The driving roller <NUM> is driven in rotation trough pulleys and belts by the introduction motor <NUM> for a dragging speed of the transport belts <NUM> slightly higher than the feeding speed of the sheets <NUM> emerging from the delivery rollers <NUM>.

The lower deflection roller <NUM> constitutes an insertion roller for the entering sheets <NUM> and defines in a transversal direction guide seats for the transport belts <NUM> alternated with support seats for elastomeric rings <NUM> of friction dragging for the sheets <NUM>. The deflection roller <NUM> determines belt portions <NUM> of the transport belts <NUM> included between the driving roller <NUM> and the roller <NUM> itself, inclined downwards, for guiding the leading edges of the sheets <NUM> emerging from the input rollers <NUM>. Flexible detachment lugs <NUM> are interposed between the belt portions <NUM> and the end portions, in slight interference with the path of the sheets <NUM>, for facilitating the separation of the trailing edges of the sheets <NUM>, jointly with the leaving of the sheets from the input rollers <NUM>.

In the functional block <NUM>, the pressing member <NUM> (<FIG>, <FIG>) comprises a pressing crossbar <NUM> on which a pneumatic actuator <NUM> operates. The crossbar <NUM> is contiguous to the arrest member <NUM> and extends in cross-section upstream of the member <NUM>. The crossbar <NUM> is slidably mounted vertically on the support plate <NUM> and has a front slanted edge and a lower surface <NUM> for contrasting the stack <NUM> and with longitudinal notches <NUM> for guiding the transport belts <NUM>. The notches <NUM> have a depth slightly less than the thickness of the belts <NUM>, so as to make a section of the belts protrude from the surface <NUM>.

The pressing crossbar <NUM> therefore presses on the portion of the stack <NUM> being formed contiguous to the plane "AP", in a pressure area adjacent to the leading edge of the sheets. This occurs through the sections of the transport belts <NUM> projecting from the longitudinal notches <NUM> and, in a direct manner, through the lower surface <NUM> of the crossbar <NUM>.

In detail, the pressing crossbar <NUM> is connected laterally to the support plate <NUM> by means of compensation springs <NUM> and is slidably guided by vertical guides <NUM> coaxial with the springs <NUM> up to end stops. At the center, the crossbar <NUM> is connected to the pneumatic actuator <NUM> by means of a ball joint <NUM>.

Conveniently, the action exerted by the pressing member <NUM> is adjustable according to the operating conditions of the equipment <NUM>, while the springs <NUM> are adjusted so as to compensate for the weight of the movable parts. Specifically, the actuator <NUM> is connected to the compressed air generator <NUM> by means of a pressure regulator, not shown, which can be set on the basis of one or more of the parameters relating to: the dragging speed of the sheets, the thickness, the weight and the finishing of the sheets used, and the current height of the stack being formed. This in response of an algorithm performed by the electronic control unit <NUM>, on the basis on experimental data under various conditions of use.

As an alternative, the actuator for the pressing crossbar <NUM> may be of an electromechanical type with the possibility of varying the operating pressure and manually setting said operating pressure on the basis of other considerations.

The sheet stacking equipment <NUM> may optionally be configured to form the stack <NUM> with overlapping sheets of regular blocks 79r and staggered blocks 79o. The regular blocks 79r are aligned according to the alignment plane "AP", while the staggered blocks 79o are aligned on a plane "OP" which is offset at the front with respect to the plane "AP". To this end, the transport and storage group <NUM> comprises an offset arrest member <NUM>, which is also mounted on the functional block <NUM>, upstream of the arrest member <NUM>, and which can be actuated as an alternative to the actuation of the member <NUM>.

The arrest member <NUM> is formed by a cross bar <NUM> with a plurality of arrest lugs <NUM> (see FIG. <FIG>) in a lower part, fixed behind the support plate <NUM>. The arrest lugs <NUM> are aligned transversally and project from the lower branches <NUM> of the transport belts <NUM> to define the alignment plane "AP" of the stack <NUM>.

The offset arrest member <NUM> comprises a vertical plate <NUM> with a plurality of offset lugs <NUM> projecting downwardly and also aligned transversally. The plate <NUM> is slidably mounted behind the plate <NUM> between the bar <NUM> and the plate <NUM> and is vertically shiftable by means of a pneumatic actuator <NUM> from a high, inactive position to a lowered, operative position. In the lowered position, the offset lugs <NUM> project from the lower branches <NUM> and define the offset alignment plane "OP" for the blocks 79o of the stack <NUM>.

Conveniently, the crossbar <NUM> of the pressing member <NUM> defines a row of transversal notches <NUM> and a row of transversal windows <NUM>. The arrest lugs <NUM> are freely housed in the transversal notches <NUM>, while the offset lugs <NUM> are slidably guided by the transversal windows <NUM>.

The sensing device <NUM> can be of any type and detects the height of the stack <NUM> by sensing the position of the pressing member <NUM> so as to minimize possible errors due to wrinkles and deformations of the last sheet of the stack. In a preferred embodiment, the device <NUM> comprises a laser illuminator/detector <NUM> mounted through a bracket (not shown) on the support plate <NUM> and a target area <NUM> formed on an upper surface of the pressing crossbar <NUM>.

The transport belts <NUM> have holes <NUM> distributed regularly along a longitudinal axis, while the transport and storage group <NUM> comprises one or more ducts <NUM> arranged transversally above the lower branches <NUM> of the belts <NUM>. The ducts <NUM> each define, in a lower surface <NUM>, longitudinal notches <NUM> (see FIG. <FIG>) for guiding the belts <NUM>.

The duct or ducts <NUM> are connected, via flexible hoses and a manifold <NUM>, to the vacuum pump <NUM> and have suction openings <NUM> at the guide notches <NUM>. This is to cause a suction action on the sheets <NUM> through the holes <NUM> of the transport belts <NUM> with dragging by adherence of the entering sheets <NUM> by the belts <NUM> up to their arrest against the lugs <NUM> or <NUM> and following sliding of the belts after the arrest of the sheets.

In the herein represented embodiment, the equipment <NUM> is designated for stacking sheets of considerable longitudinal extension and includes three ducts <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>: the duct <NUM>-<NUM> is arranged downstream of the deflection roller <NUM>, the duct <NUM>-<NUM> is arranged upstream and at short distance from the pressing member <NUM>, while the duct <NUM>-<NUM> is in an intermediate position between the ducts <NUM>-<NUM> and <NUM>-<NUM>. It is also clear that the equipment <NUM> can provide a greater or lesser number of ducts <NUM> or a single duct depending on the lengths of the sheets to be stacked.

Conveniently, the duct or ducts <NUM> are mounted on slides which can slide along the lateral guides 56r and 56i and can also be positioned at different distances from the input rollers <NUM> depending on the length of the sheets <NUM>.

For effective jamming-free shifting, the sheets <NUM> must adhere to the transport belts <NUM> sufficiently for dragging, but must be able to be easily detached at the time of stacking. Moreover, before the detachment and when the sheets have been arrested by the lugs <NUM> or <NUM>, the sliding of the belts must not cause ripples or jams. The friction coefficient of the belts <NUM> is therefore an important parameter for a reliable stacking of the sheets <NUM>.

The problems of wrinkles or other deformations of the sheets and jamming are serious if the equipment <NUM> should handle sheets of very different characteristics as for weight, rigidity and smoothness, variable for example from a tissue paper to a coated paper. The use of transport belts with a friction coefficient selected for reference papers of a given type may cause drawbacks when the equipment <NUM> handles sheets of types very different from those of the reference papers.

Advantageously, it has been found that the above problems are solved by using together transport belts for the sheet having different friction coefficients.

According to a feature of the invention, the stacking equipment <NUM>, in the transport and storage group <NUM>, employs <NUM> transport belts <NUM>, of which eight belts with a low friction coefficient (grip <NUM> on steel) are alternated with four belts with a medium friction coefficient (grip <NUM> on steel). By virtue of this solution, the equipment <NUM> can reliably and at high speed (<NUM>/mn) stacking sheets of paper with a weight of <NUM> to <NUM>/m<NUM> and finishes including coating.

In the accumulation and delivery group <NUM>, the stack support <NUM> (<FIG>, <FIG> and <FIG>) comprises a frame <NUM> of rectangular outline, a pair of transversal shafts <NUM> and <NUM>, a plurality of support and delivery blocks <NUM>, driving rings <NUM> of the shaft <NUM> and a delivery motor <NUM>.

The frame <NUM> extends below the transport and storage group <NUM> and rotatably supports the shafts <NUM> and <NUM> in respective front and rear sections.

The support and delivery blocks <NUM> have a longitudinally extended parallelepiped shape, and are carried side by side by the frame <NUM> transversally spaced from one another by the driving rings <NUM>. The delivery motor <NUM> is mounted on a lower part of the frame <NUM> and drives the transversal shaft <NUM> through respective pulleys and belts.

The support and delivery blocks <NUM> each comprise a spar <NUM>, a pair of pulleys <NUM> and <NUM> keyed on the shafts <NUM> and <NUM>, sides 106r and <NUM> for the spar <NUM> and the pulleys <NUM>, an extended delivery belt <NUM> with upper and lower branches stretched between the pulleys <NUM> and <NUM> and rollers <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> of guide for the belt <NUM>.

The pulleys <NUM> and <NUM> of each block <NUM> and the driving rings <NUM> present upper sectors in a condition of tangency with an upper surface of the longitudinal members <NUM>. The pulleys <NUM> and the delivery belts <NUM> are toothed for a positive driving by the motor <NUM>. The upper branches of the belts <NUM> rest with internal teeth on a upper surface of the spar <NUM>, while the lower branches are deflected upwards by the rollers <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>.

The set of the upper branches of the delivery belts <NUM> defines a bearing surface "BS" for the stack <NUM> being formed, with contrast on the part of the spars <NUM>. The delivery belts <NUM> are driven by the motor <NUM> in the direction "F", with sliding of the internal teeth on the upper surfaces of the spars in some operating conditions of the equipment <NUM>.

The stack support <NUM> has the possibility of vertical displacement by means of vertical guides <NUM> between a reference position "RP" (<FIG>) and a delivery position "DP" (<FIG>). The reference position "RP" is the highest of the stack support <NUM>, for a sheet-free condition in which the bearing surface "BS" of the delivery belts <NUM> is spaced by the space "G" from the conveying surface "TS". The delivery position "DP" is the lowest of the stack support <NUM> and wherein the surface "BS" is substantially coplanar with a lower edge of the output gate <NUM> and with the conveyor belt "CB".

Conveniently, a panel <NUM> is mounted vertically downward on a rear portion of the frame <NUM>. The output gate <NUM> is shielded by the panel <NUM> when the stack support <NUM> is in the reference position "RP" and is free for the passage of the stack when the support <NUM> is in the delivery position "DP".

As above reported, depending on the number of accumulated sheets, the compensation mechanism <NUM> lowers the stack support <NUM> below the reference position "RP" to keep the space "G" constant. The mechanism <NUM> also moves the stack support between the position reached upon completion of the stack <NUM> and the delivery position "DP". In this "DP" position, the belts <NUM> are moved by the delivery motor <NUM> to forward the stack <NUM>, through the output gate <NUM> toward the conveyor belt "CB" for the subsequent treatments.

The compensation mechanism <NUM> comprises a pair of ball screws with grooved shafts <NUM> and <NUM> and respective nut screws <NUM> and <NUM>. The nut screws <NUM> and <NUM> are fixed to the sides of the frame <NUM>, while the grooved shafts <NUM> and <NUM> are rotatably supported, with a lower end, on a transversal plate <NUM> and are driven in rotation, throughf belts and pulleys by a compensation motor <NUM> also controlled by the electronic unit <NUM>.

The operation of the sheet stacking equipment <NUM> is as follows:
Depending on the longitudinal dimensions of the sheets <NUM> to be stacked, the operator positions the functional block <NUM> and the duct or ducts <NUM> at programmed distances from the input rollers <NUM>. By means of the touch screen "CD" (<FIG>), data are also set on the number of sheets <NUM> to be stacked, the number of sheets of blocks to be staggered in the case of offset stacking, and on the characteristics of the sheet. With these settings, the electronic unit <NUM> also regulates the pressure in the actuator <NUM> to optimize the operating parameters.

In an initial stage of stacking, the stack support <NUM> (<FIG>) is empty and in the reference position "RP", height "H" from the plane "IP" and distance "G" between the bearing surface "BS" and the conveying surface "TS" of the branches <NUM> of the transport belts <NUM>. The arrest lugs <NUM> are interposed in the spaces between the support and delivery blocks <NUM> and the crossbar <NUM> of the pressing member <NUM> presses on the delivery belts <NUM> at the pressure determined by the electronic unit <NUM>. The output gate <NUM> is shielded by the panel <NUM>.

Upon receipt of the first sheet <NUM> from the delivery rollers <NUM>, the electronic unit <NUM> activates the introduction motor <NUM>, rotating the input rollers <NUM> with movement of the transport belts <NUM> at a driving speed slightly higher than the feeding speed of the sheets <NUM>. Moreover, limited to this first sheet, the unit <NUM> also activates the delivery motor <NUM>, moving the upper branches of the delivery belts <NUM> in the feed direction "F" with a speed slightly higher than the speed of the sheets <NUM> emerging from the input rollers <NUM>.

At the exit from the alignment section <NUM>, the input rollers <NUM> advance the sheet on the introduction plane "IP" in the direction "F" and along the inclined belt portions <NUM>. The sheet is flexed and accompanied downwards until its leading edge meets the delivery belts <NUM> which are in movement. This due to the positive thrust action by the rollers <NUM>, also facilitated by the driving rings <NUM>, the inclined portions <NUM> and the deflection roller <NUM> with the driving rings <NUM>.

After the contact with the delivery belts <NUM>, the sheet is flexed and accompanied horizontally again by the action of the input rollers <NUM> and with the contribution of the deflection roller <NUM>, the branches <NUM> of the transport belts <NUM> and now also by the upper branches of the belts <NUM>.

The first sheet <NUM> continues its travel by resting on the delivery belts <NUM>, until its leading edge surpasses the position of the duct <NUM>-<NUM>. Here, the sheet is lifted against the lower branches <NUM> of the transport belts <NUM>. This owing to the suction action of the conduit <NUM>-<NUM> through the openings <NUM> of the guide notches <NUM> and through the holes <NUM> of the belts <NUM>. The sheet <NUM> continues to advance with passage and suction of successive parts of the sheet at the openings <NUM>, through following holes <NUM> of the belts <NUM>, by the combined positive driving action of the input rollers <NUM> and owing to the friction dragging of the upper branches, in motion, of the delivery belts <NUM>.

In the case where the equipment <NUM> also includes the ducts <NUM>-<NUM> and <NUM>-<NUM>, after the lifting of the sheet <NUM> by the duct <NUM>-<NUM>, the adhesion to the transport belts <NUM> is improved by the suction of the ducts <NUM>-<NUM> and <NUM>-<NUM>, when the sheet passes in front of these ducts <NUM>-<NUM> and <NUM>-<NUM>.

After leaving the trailing edge of the sheet from the input rollers <NUM>, the sheet <NUM> continues to be dragged by friction by the sole transport belts <NUM> ensured by the suction action of the duct or ducts <NUM> and causing the sheet to enter completely into the transport and storage group <NUM>. The sheet now tends to resume a flat configuration and to rest with the trailing edge on the delivery belts <NUM>, facilitated by the detachment lugs <NUM>.

Continuing its friction movement by the transport belts <NUM>, the first sheet <NUM> meets with its leading edge the pressing member <NUM>, with downward deviation caused by the slanted edge of the pressing crossbar <NUM>. Through the belts <NUM> and the surface <NUM> of the crossbar <NUM>, the actuator <NUM> further pushes the sheet <NUM> against the delivery belts <NUM> with the set pressure. The sheet is finally arrested when it meets the lugs <NUM> of the arrest member <NUM>, with the belts <NUM> sliding in motion with respect to the sheet. The electronic unit <NUM> arrests the delivery motor <NUM> and consequently the belts <NUM> but keeps the introduction motor <NUM> activated and therefore the input rollers <NUM>, the driving roller <NUM> and the belts <NUM> in motion, waiting for a following sheet <NUM> for stacking.

The complete introduction of the first sheet <NUM> into the transport and storage group <NUM>, on command of the electronic unit <NUM>, causes the compensation motor <NUM> to be actuated, rotating the grooved shafts <NUM> and <NUM> so as to lower the stack support <NUM> by an amount corresponding to the thickness of the sheet. This in response to feedback information from the laser illuminator/detector <NUM> on the position of the pressing crossbar <NUM> as detected in the target area <NUM>. In this way, the space "G" intended for the passage of a new sheet to be stacked is kept constant at its optimum value.

A new sheet <NUM> entering the input rollers <NUM> is also flexed and accompanied downwards by the driving roller <NUM> and the inclined belt portions <NUM>, but its leading edge now meets the preceding sheet. Due to the thrust action of the input rollers <NUM> and the facilitation of the roller <NUM> with the rings <NUM>, the inclined portions <NUM> and the insertion roller <NUM> with the rings <NUM>, the new sheet is flexed and accompanied horizontally and inserting itself between the lower branches <NUM> of the transport belts <NUM> and the parts of a preceding sheet still adhering to the branches <NUM>.

The new sheet <NUM> continues its travel above the preceding sheet, until its leading edge reaches the duct <NUM>-<NUM>, putting itself in contact with the lower surface <NUM>. The part of the preceding sheet, no longer retained by the suction of the duct <NUM>-<NUM> falls on the surface "BS" of the support <NUM>, while the new sheet adheres to the lower branches <NUM> of the transport belts <NUM> and is dragged by it. The new sheet then continues to advance for the passage and suction of successive parts in front of the duct <NUM>-<NUM> and the ducts <NUM>-<NUM> and <NUM>-<NUM>, while the preceding sheet progressively rests on the upper branches of the delivery belts <NUM>, as the first sheet of the stack <NUM>.

The new sheet <NUM> also continues its movement by the transport belts <NUM> alone for the adhesion ensured by the duct or ducts <NUM> after the leaving of its trailing edge from the input rollers <NUM>. The new sheet tends to resume a flat configuration and to rest with the trailing edge on the preceding sheet, facilitated by the detachment lugs <NUM>. In sequence, the new sheet <NUM> is deflected downwards by the pressing crossbar <NUM> of the pressing member <NUM> and pressed against the underlying sheet by the actuator <NUM>. The sheet is finally stopped when its leading edge contacts the arrest lugs <NUM>, with sliding of the sheet with the transport belts <NUM> in motion.

Full introduction of the new sheet <NUM> into the transport and storage group <NUM> causes the compensation motor <NUM> to start again upon control of the electronic unit <NUM> and feedback by the sensing device <NUM> and further loweringof the stack support <NUM> by the amount corresponding to the thickness of the sheet so as to keep the space "G" constant.

The following sheets are stacked sequentially as described above for the second sheet, with progressive formation of the stack <NUM>.

If the offset option is provided, after the setting of the number of sheets constituting each regular block 79r has been stacked, the electronic unit <NUM> activates the offset actuator <NUM>. The offset lugs <NUM> are lowered through the windows <NUM> of the pressing crossbar <NUM> placing the ends below the lower branches <NUM>, whereby determining the offset alignment plane "OP" for the staggered blocks 79o.

During stacking, the pressing member <NUM> exerts its action on a pressure area of the sheets adjacent to the pressing member. This prevents the impact of an entering sheet against the arrest lugs <NUM> or against the offset lugs <NUM> and the thrust of the transport belts <NUM> from causing the leading edge to be lifted and the sheet to curl, resulting in overlapping and jamming upon arrival of the subsequent sheets. In turn, the detection of the position of the sheet previously stacked by means of the target area <NUM> of the pressing crossbar <NUM>, as information for maintaining the best height "H", prevents wrinkles or deformations on the stacked sheet from giving rise to errors in the position of the support <NUM> and space values "G" different from the optimal one, with other risks of jams for the new sheet to be stacked.

Upon reaching the number of sheets <NUM> or the number of blocks 79r and 79o to be stacked, the electronic unit <NUM> again activates the compensation motor <NUM>, moving the stack support <NUM> from the last stacking position to the delivery position "DP", without any servo to the sensing device <NUM>. The bearing surface "BS" of the delivery belts <NUM> (<FIG>) is now coplanar with the conveyor belt "CB" and the panel <NUM> is below the output gate <NUM>, completely discovering it.

The electronic unit <NUM> now activates the delivery motor <NUM>, moving the upper branches of the delivery belts <NUM> in the "F" direction, and consequently dragging the stack <NUM> with the sheets stacked on the conveyor belt "CB" for delivery to the user equipment.

Claim 1:
An equipment (<NUM>) for stacking sheets (<NUM>) comprising a stack support (<NUM>) for sheets in vertical stacking, input rollers (<NUM>) for introducing and feeding sheets along a given direction (F), a plurality of elongated transport belts (<NUM>) with lower branches (<NUM>) arranged above the stack support and a compensation mechanism (<NUM>) for modifying the height of the stack support with respect to a reference surface (IP) and wherein the transport belts are motorized for shifting entering sheets with the lower branches and depositing the sheets on the stack support or on stacked sheets, said equipment further comprises an arrest member (<NUM>) for the entering sheets, a pressing member (<NUM>) for a forming stack (<NUM>), a sensing device (<NUM>) for the height of a last sheet of the stack and an electronic control unit (<NUM>), wherein
the arrest member (<NUM>) is designated for arresting and aligning sheets in stacking against a stack alignment surface (AP);
the pressing member (<NUM>) is contiguous to the arrest member (<NUM>) and operates on the last sheet of the stack on a pressing area adjacent to a leading edge of said last sheet of the stack with stabilization function;
the pressing member (<NUM>) comprises a pressing cross member (<NUM>) having a lower surface (<NUM>) of contrast for the stack, said cross member operates on the pressing area of the last sheet of the stack with its lower surface and wherein
the compensation mechanism (<NUM>) is servoized to the sensing device, on control by the electronic unit, for maintaining constant the height of the last sheet of the stack from the reference surface (IP), the said equipment being characterized in that
the lower surface (<NUM>) of the pressing cross member (<NUM>) defines longitudinal notches (<NUM>) of guide for the transport belts (<NUM>) and wherein
the lower surface of said cross member further operates on the pressing area of the last sheet of the stack (<NUM>) through sections of the said belts (<NUM>) guided by the longitudinal notches (<NUM>).