BENCH FOR INSERTING CORRUGATED CARDBOARD SHEETS INTO A TRANSFORMING LINE

Abstract: An inserting bench for corrugated cardboard sheets into a transforming line is disclosed, substantially comprising: a sheet-accelerating station (1) equipped with a plurality of sheet-accelerating wheels (7) arranged on at least two parallel rows; and a sheet-advancing station (25) located downstream of the accelerating station (1) to insert the sheets being accelerated into a downstream printing station (21). The bench allows improving the mechanical characteristics of the sheets at a reduced cost because the accelerating wheels (7) are equipped with friction means (23) to accelerate the sheets to the speed of the following station, and the sheet-advancing station (25) is composed of as many rows of dragging wheels (27) as the number of rows of sheet-accelerating wheels (7).

Description: BENCH FOR INSERTING CORRUGATED CARDBOARD SHEETS INTO A TRANSFORMING LINE The present invention refers to an inserting bench for corrugated cardboard sheets into a transforming line. Various types of benches are known in the art in order to insert sheets upstream of a transforming line, starting from a series of stacked sheets. These benches approximately all operate according to the same principle, that will be shown with reference to Figure 1. In such Figure, there is shown a traditional bench comprising a sucked accelerating station for cardboard sheets equipped with loading means 3 for the stacks of sheets 5 and with a plurality of sheet-accelerating wheels 7 arranged on three parallel rows. The first sheet of the stack 5, once having been accelerated up to the peripheral speed of the cylinders 17, 19 of the line, is lifted in a known way by a series of battens 9 driven into a lifting and lowering movement by two arms 11 supported by linkages 13 actuated by cams (not shown) . The sheet then goes out of the opening 15 and is inserted into the gap between the pair of inserting cylinders 17, 19 that make the sheet advance to the following printing station 21, the sheet having a speed that is equal to the one required by the printing station 21 itself. This system has a major drawback: the inserting cylinders 17, 19, in order to be able to advance the sheet, squash it, thereby reducing its mechanical characteristics (compressive strength) and providing a finished box-shaped product that is not completely satisfactory. Object of the present invention is solving the above prior art problem, by providing a sheet- inserting bench that allows removing the pair of inserting cylinders 17, 19 located downstream of the accelerating wheels 7, thereby allowing to produce cardboard sheets that are provided with the same compressive strength with a lower thickness, or with a higher compressive strength with the same thickness. This obviously implies a very high saving of costs for the end user. Moreover, the provision of wheels 7 equipped with special arrangements allows realizing the inserting bench without impairing the operating capabilities of the machine with respect to the minimum formats. The above and other objects and advantages of the invention, as will appear from the following description, are obtained with a sheet-inserting bench like the one disclosed in Claim 1 or 11. Preferred embodiments and non-trivial variations of the present invention are disclosed in the dependent Claims . The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which: Figure 1 is a sectional side view of a sheet- inserting bench according to the prior art; Figure 2 is a sectional side view of an embodiment of the sheet-inserting bench according to the present invention; Figure 3 is a top view of the bench of Fig. 1; and Figure 4 is a side view of the bench in Fig. 1 that points out the sheet-lifting device. Fig. 1 has been previously described with reference to the prior art. With reference to Fig. 2 to 4, there is shown a preferred embodiment of the sheet-inserting bench according to the present invention. According to such embodiment, the inserting bench comprises a sucked sheet-accelerating station 1 (for ease of reference, where possible, the same numerals already shown in Fig. 1 will be used) equipped with sheet-loading means 3 and with a plurality of sheet-accelerating wheels 7 arranged on at least two parallel rows (in the embodiment shown, the rows are three) . The accelerating wheels 7 are equipped with respective friction means 23 adapted to accelerate each one of the sheets from a null speed to the speed of the following station 21. The friction means 23 are particularly composed of a coating made of plastic material placed on the external circumference of each one of the wheels 7; moreover, the plastic coating covers the circumference of the accelerating wheels 7 partially, that is not completely, leaving on each wheel 7 of each row a free sector of circumference, and variably, in compliance with the following formulae (Fig. 2) : Al = m i n — X A 2 = Ai + H = L rain - X + H A 3 = A 2 + H = L mιn - X + 2H where : Ai, A 2 , A 3 = sector widths L m i n = minimum sheet dimension X = distance between an axis A of a first row and a front reference beam 37 for the sheets H = center distance between the rows of sectors provided that: A x = L mιn - X ≥ Y, where Y is the distance between a rotation axis of a cylinder 19 and the front beam 37. The inventive bench further comprises a sheet- advancing station 25 located downstream of the accelerating station 1 to insert the sheets being accelerated by the acceleration station 1 into the downstream printing station 21 at the speed required by the printing station 21. The sheet- advancing station 25 is composed of as many rows of dragging wheels 27 as the number of rows of accelerating wheels 7 of the accelerating station 1. As already seen, each one of the stations 1 and 25 of the inserting bench of the present invention is sucked, that is equipped with vacuum- creating means (not shown) , for example centrifugal aspirators like the fans, adapted to keep downwards-sucked the sheet to be moved during the acceleration and advancement steps thereof. Various arrangements are possible for the provided fans, in that, by always keeping one of them, as well known, in the accelerating station 1, it is possible to provide a different number of them in the advancing station 25. In fact, where working reasons so require, the advancing station 25 can be equipped with a single fan, or with as many fans as the number of rows of wheels 27 composing it (three in Fig.s 2 to 4). The advancing station 25, for this purpose, can be divided into separate sections (29', 29'', 29'") to which a different suction force can be applied by a different fan. In fact, the traction force that the advancing station 25 must exert on the sheet must exceed the advancement-resisting forces, that are proportional to the weight of the stack 5 that still partly rests on the sheet, to the vacuum created by the fans and to the friction coefficients between cardboard and cardboard and between cardboard and plate. Therefore, the traction force must be relatively high and must be kept approximately constant while the sheet position changes with respect to the two stations 1 and 25. Each one of the stations 1 and 25 is further composed of a plate box 30 being open on its upper face and being kept under vacuum through the above centrifugal aspirator. On the upper face the wheels 7 and 27 tangentially project and exert on the sheets the necessary forces for the advancement. The accelerating station 1 is completed on its upper face by a plate 31 with a plurality of slots through which the wheels 7 project; the plate 31 can perform a vertical movement (of about 3 ÷ 4 mm) in order to let the wheels 7 project or in order to hide them under its plane. Such vertical movement is realized by the lifting means 11 and 13 driven by the piston 33 and is controlled by an oscillator (not shown) phased with the machine cycle and with the movement of the wheels that are in turn driven by an intermitter. The advancing station 25 is also equipped with a slotted plate 35, with the difference that such plate 35 is fixed and the wheels 27 projecting therefrom have a peripheral speed that is equal to the speed of the other cylinders on the line. Alternatively, the accelerating station can be equipped, instead of the plate 31, with a plurality of battens 9 (like those in Fig. 1) adapted to lift each on of the sheets in an outgoing position when such sheet has been accelerated at the final speed. The operation of the inserting bench according to the invention will now be described. A stack 5 of overlapped sheets is abutted against the slotted plate 31 of the accelerating station 1 with the plate 31 in the high position. The stack 5 is frontally delimited by a beam 37 that is able to be vertically registered and that allows the passage therebelow of a single sheet only. When the machine is running, the wheels 7 of the accelerating station 1 intermittently rotate without producing any effect on the sheet since this latter one is kept away from the high plate 31. When the sheet insertion is commanded, the plate 31 starts its vertical swinging movement and, when it is lowered, the wheels 7 are stopped. When the plate 31 reaches the low position, the wheels 7 start rotating thereby advancing the sheet. The sheet is accelerated up to the speed of the cylinders of the transforming line before coming in contact with the first row of wheels 27 of the advancing station 25. The plate 31 must go back to its high position before the rotating wheels 7 can get in contact with the sheet that is immediately above the one that is entering. After having lifted the plate 31 from the accelerating station 1, the wheels 27 of the advancing station 25 must guarantee the sheet advancement at a constant speed. So that the advancing station 25 can exert on the sheet the necessary force to guarantee the advancement by exceeding the above resistances, it is necessary that the station 25 is completely covered by the sheet and therefore the accelerating station 1 must guarantee the traction for a stroke that is at least equal to the depth, in the advancement direction, of the station 25. In a conventional wheeled inserting device, this condition would be met if the dimension along the longitudinal direction of the minimum workable sheet is greater than or equal to the overall longitudinal dimension of the two paired stations. This would limit the minimum workable format, thereby limiting the operating machine capabilities to medium-big sized sheets. In order to overcome such limit, the wheels 7 have been realized, in the advancing station 1, with wheel sectors with different angular width in the following rows so that the contact between sheet and wheel 7 does not depend only on the lifting and lowering cycle of the slotted plate 31, but also on the sector widths . This width is computed in such a way that, when a sheet, of the minimum workable format, gets to uncover the axis A of the first row, the sector ends too so that such row cannot exert any action on the sheet immediately above. The width of the sectors in the second row (from right to left in the Figures) will be greater than the one of the first row in order to continue the traction till the second axis A' will also be uncovered, and similarly the sectors on the third row (always from right to left in the Figures) will in turn be greater . When the tail of the interested sheet gets to uncover the third axis A' ' , the plate 31 will be lifted to avoid the contact betwen upper sheet and sectors on all three rows that will appear again on the upper face of the box of the accelerating station 1. Briefly summarizing, the width of the sectors of the three following rows, measured on the external arc, is, as already seen, as follows: l = m m ~ X A 2 = Ai + H = L mιn - X + H A 3 = A 2 + H = L mιn - X + 2H where : i, A 2 , A 3 = sector widths L mm = minimum sheet dimension X = distance between an axis A of a first row and a front reference beam 37 for the sheets H = center distance between the rows of sectors provided that: Ai = L mιn - X Y, where Y is the distance between a rotation axis of a cylinder 19 and the front beam 37. This arrangement into sectors instead of into wheels allows successively excluding the contact between wheels 7 and sheet, always exploiting the maximum number of gripping wheels 7, and since the center distances between the rows of wheels 7, 27 in the two stations 1, 25 are such that every time a row of wheels 7 in the station 1 goes out of the operating condition, it is replaced by the corresponding row of wheels 27 of the station 25, a transport is performed that is always guaranteed by at least three rows of wheels (in the embodiment shown) . Some preferred embodiments of the invention have been described, but obviously they are subjected to further modifications and variations within the same inventive idea. For example, it is possible to realize an inserting bench that combines the teachings of the benches in Fig. 1 and in Fig.s 2 to 4. This bench, not shown, allows obtaining the above-mentioned benefits also with a pair of inserting cylinders 17, 19 like those in Fig. 1, since the squashing that such cylinders exert on the sheets can be highly reduced taking advantage from the fact that the sheets have already been suitably accelerated by station 1.

Claims: CLAIMS 1. Inserting bench for corrugated cardboard sheets into a transforming line, substantially comprising: a sheet-accelerating station (1) equipped with sheet-loading means (3) and with a plurality of sheet-accelerating wheels (7) arranged on at least two parallel rows; a sheet-advancing station (25) located downstream of said sheet-accelerating station (1) to insert the sheets being accelerated by said sheet-accelerating station (1) into a downstream printing station (21) at a speed required by said printing station (21) ; characterized in that: said sheet-accelerating wheels (7) are equipped with respective friction means (23) adapted to accelerate each one of said sheets from a null speed to a speed of the following downstream station; and in that : said sheet-advancing station (25) is composed of as many rows of dragging wheels (27) as the number of rows of sheet-accelerating wheels (7) of said sheet-accelerating station (1). 2. Sheet-inserting bench according to Claim 1, characterized in that said friction means (23) are composed of a coating made of plastic material that is placed on the external circumference of each one of said sheet- accelerating wheels (7). 3. Sheet-inserting bench according to Claim 2, characterized in that the plastic coating covers the circumference of the sheet-accelerating wheels (7 ) : partially, that is not completely, leaving on each wheel (7) of each row a free sector of circumference; and variably according to the distance between the rotation axis (A, A' , A' ' ) of each row and the outlet point (15, 37) of the sheets from said sheet-accelerating station (1). 4. Sheet-inserting bench according to Claim 3, characterized in that the development according to which the plastic coating covers each one of the wheels (7) is in compliance with the following formulae: A l = m i n - X A 2 = Ai + H = L mιn - X + H A 3 = A 2 + H = L mιn - X + 2H where : Ai, A 2 , A 3 = sector widths L mm = minimum sheet dimension X = distance between an axis A of a first row and a front reference beam (37) for the sheets H = center distance between the rows of sectors provided that: A x = L mιn - X ≥ Y, where Y is the distance between a rotation axis of a cylinder (19) and the front beam (37) . 5. Sheet-inserting bench according to any of the previous Claims, characterized in that the sheet- accelerating station (1) and the sheet-advancing station (25) are equipped with vacuum-creating means adapted to keep the sheet to be moved sucked downwards during acceleration and advancement steps of said sheet. 6. Sheet-inserting bench according to Claim 5, characterized in that said vacuum-creating means are composed of a centrifugal aspirator both for the sheet-accelerating station (1) and for the sheet-advancing station (25). 7. Sheet-inserting bench according to Claim 5, characterized in that said vacuum-creating means are composed of a centrifugal aspirator for the sheet-accelerating station (1) and of a centrifugal aspirator for each one of said rows of wheels (27) for the sheet-advancing station (25) . 8. Sheet-inserting bench according to any of the previous Claims, characterized in that the rows of wheels (7) of the sheet-accelerating station (1) and the rows of wheels (27) of the sheet- advancing station (25) are three. 9. Sheet-inserting bench according to any of the previous Claims, characterized in that the sheet- accelerating station (1) is equipped with a sheet-lifting plate (31) adapted to lift each one of the sheets in an outgoing position when said sheet has been accelerated at a final speed. 10. Sheet-inserting bench according to any of Claims 1 to 8, characterized in that the sheet- accelerating station (1) is equipped with a plurality of battens (9) adapted to lift each one of the sheets into an outgoing position when said sheet has been accelerated at a final speed. 11. Inserting bench for corrugated cardboard sheets into a transforming line, substantially comprising: a sheet-accelerating station (1) equipped with sheet-loading means (3) and with a plurality of sheet-accelerating wheels (7) arranged on at least two parallel rows; a sheet-advancing station (25) located downstream of said sheet-accelerating station (1) to insert the sheets being accelerated by said sheet-accelerating station (1) into a downstream printing station (21) at a speed required by said printing station (21) ; characterized, in combination, in that: said sheet-accelerating wheels (7) are equipped with respective friction means (23) adapted to accelerate each one of said sheets from a null speed to a speed of the following downstream station; and said sheet-advancing station (25) is composed of a pair of overlapped inserting cylinders (17, 19) for the passage therethrough of each of the sheets to be moved. 12. Sheet-inserting bench according to Claim 11, characterized in that said friction means (23) are composed of a coating made of plastic material that is placed on the external circumference of each one of said sheet- accelerating wheels (7). 13. Sheet-inserting bench according to Claim 12, characterized in that the plastic coating covers the circumference of the sheet-accelerating wheels (7 ) : partially, that is not completely, leaving on each wheel (7) of each row a free sector of circumference; and variably according to the distance between the rotation axis (A, A' , A' ' ) of each row and the outlet point (15) of the sheets from said sheet- accelerating station (1). 14. Sheet-inserting bench according to Claim 13, characterized in that the development according to which the plastic coating covers each one of the wheels (7) is in compliance with the following formulae: Ai = L m m ~~ X A 2 = Ai + H = L mιn - X + H A 3 = A 2 + H = L mn - X + 2H where : Ai, A , A 3 = sector widths L mm = minimum sheet dimension X = distance between an axis A of a first row and a front reference beam (37) for the sheets H = center distance between the rows of sectors provided that: Ai = L min - X ≥ Y, where Y is the distance between a rotation axis of a cylinder (19) and the front beam (37) . 15. Sheet-inserting bench according to any of Claims 11 to 14, characterized in that the sheet- accelerating station (1) is equipped with vacuum- creating means adapted to keep the sheet to be moved sucked downwards during an acceleration steps thereof. 16. Sheet-inserting bench according to Claim 15, characterized in that said vacuum-creating means are composed of a centrifugal aspirator. 17. Sheet-inserting bench according to any of Claims 11 to 16, characterized in that the rows of wheels (7) of the sheet-accelerating station (1) are three. 18. Sheet-inserting bench according to any of Claims 11 to 17, characterized in that the sheet- accelerating station (1) is equipped with a sheet-lifting plate (31) adapted to lift each one of the sheets in an outgoing position when said sheet has been accelerated at a final speed and has reached the downstream sheet-advancing station (25) . 19. Sheet-inserting bench according to any of Claims 11 to 17, characterized in that the sheet- accelerating station (1) is equipped with a plurality of battens (9) adapted to lift each one of the sheets into an outgoing position when said sheet has been accelerated at a final speed and has reached the downstream sheet-advancing station (25) .

Inventors: DE STEFANIS SERGIO, DE STEFANIS, SERGIO
Applicants: STEFANIS SERGIO DE, TEXO SRL, DE STEFANIS, SERGIO, TEXO S.R.L.
Application year: 1999
Main classification: B65H3
IPC codes: B65H3, B65H27