Suction bar system for converters

Abstract

The present invention relates to a suction bar system for a converter (10), the suction bar system comprising at least one suction bar assembly (31) comprising a suction plate (36) mounted on a cross beam having an internal air supply passage (34). The suction plate (36) comprises a plurality of main air passages (48), each of which has a first suction opening (46a) and a second suction opening (46b). The main air passages (48) comprise a constricted section (S2) having a first connecting duct (50) configured to create a pressure drop across the first suction openings (46a).

Description

[Technical Field]

[0001] The present invention relates to converting machines for producing box and packaging blanks, and more particularly to a suction bar system configured to hold the blanks in the converting machine. [Background technology]

[0002] Converting machines are used in the manufacture of packaging items, such as paperboard and corrugated boxes. Platen presses are converting machines that can be configured to process blanks, such as paperboard and corrugated sheets. Specifically, platen presses are configured to die-cut blanks for boxes and packaging elements from sheets. Platen presses are also sometimes referred to as "die-cutting machines."

[0003] Platen printing presses include multiple processing units or stations, and conveyor systems are provided in such machines to hold and transport blanks from one processing unit to the next.

[0004] The conveyor system helps position the sheet so that the converting operation occurs at the correct location on the blank. The conveyor system can include gripper bars configured to grip the leading edge of the blank. The gripper bars hold the blank in the correct longitudinal and lateral position and transport the blank according to preset register timing.

[0005] However, it is also desirable to hold the trailing edge in place with a suction plate to prevent the sheet from bowing or deforming.When the speed of the gripper bars changes, the blank tends to bow during deceleration.

[0006] WO20245116 discloses a suction plate that holds the trailing edge of a sheet as it is transported through a platen printing press. The suction plate includes a line of air openings arranged side by side. However, the suction plate must be positioned a specific vertical distance from the blank to hold the blank in place. Problems arise when the blank size and thickness vary, increasing the distance from the blank to the suction plate. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 20245116 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above-mentioned problems, it is an object of the present invention to provide a suction bar assembly having an improved ability to grip and hold the trailing edge of a sheet, where the suction force is adapted to hold sheets of various sizes. [Means for solving the problem]

[0009] This object is solved by a suction bar system according to claim 1 and a positioning system according to claim 14.

[0010] According to a first aspect of the present invention, there is provided a suction bar system for a converter machine, the suction bar system comprising at least one suction bar assembly comprising a suction plate mounted on a cross beam having an internal air supply channel.

[0011] the suction plate has a suction surface configured to apply a suction force to blanks conveyed in a conveying direction through the converting machine; the suction plate includes a plurality of main air flow paths, each of the main air flow paths including an air inlet connected to the air supply flow path and an air outlet, the flow direction extending between the air inlet and the air outlet; Each of the main air flow paths comprises a first suction opening and a second suction opening, the suction openings being provided on the suction surface, and the main air flow paths comprise a constricted section having a first connecting duct connected to the first suction opening, the constricted section being configured to generate a pressure drop across the first suction opening.

[0012] The invention is based on the realization that gripping of the blank by the suction plate can be improved and accelerated by first reducing the air volume present between the suction plate and the blank and then applying a strong localized suction force to the trailing edge of the blank.

[0013] In one embodiment, the main air flow path has a cross-sectional area in the flow direction upstream of the second suction opening that is larger than the cross-sectional area of the constricted section. The suction bar system is designed to generate an air flow from the combined inlet air flow and the air flow from the first suction opening, such that a large air volume is injected through the main air flow path at the second air flow opening. This combined air flow then passes through the connection section to the second air opening, generating a high suction volume through the second air opening.

[0014] In one embodiment, the first and second suction openings are arranged in separate lines perpendicular to the conveying direction T. The lines are therefore arranged in the longitudinal direction of the cross beam.

[0015] In one embodiment, the constricted section of the main airflow path is a venturi section.

[0016] Preferably, the second suction opening is connected to the main air flow path via a second connecting duct. Preferably, the connecting duct to the first suction opening is located upstream of the connecting duct to the second suction opening in the flow direction.

[0017] In one embodiment, the first suction opening is located further downstream in the conveying direction than the second suction opening.

[0018] The internal air supply channel may have an inlet end connected to the air flow generator and may include a plurality of distribution outlet openings configured to align with the air inlet openings in the suction plate.

[0019] Preferably, the suction plate is a separate component and is removably attached to the cross beam.

[0020] In one embodiment, the first suction opening is located a predetermined distance from the second suction opening, the distance being less than 10 times the diameter of the main air flow path at the second suction opening.

[0021] The distance between the first and second suction openings may vary between the main channels.

[0022] For example, the suction openings may be staggered so that the suction surface has a regular arrangement of suction openings, which means that the lengths of the distance sections may differ for parts of the main flow path.

[0023] In one embodiment, the suction bar system may further comprise a deflection flange, the outlet opening of the main air flow path being located below the deflection flange.

[0024] In one embodiment, the suction bar system can further include a displacement mechanism comprising first and second slide rails, the suction plate being slidably mounted on the slide rails.

[0025] According to a second aspect of the present invention, there is provided a positioning system comprising a suction bar system and a gripping unit, the gripping unit being configured to grip and position a front leading edge of a blank, the suction bar system being positioned such that a first suction opening is located further upstream in the conveying direction than a second suction opening.

[0026] In one embodiment, the positioning system comprises a plurality of suction bar assemblies arranged along the conveying direction, such that a suction bar assembly is located at each workstation and configured to hold the trailing edge of the blank.

[0027] The present invention will now be described with reference to the accompanying drawings, in which like features are given the same reference numerals, and in which: [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a schematic cross-sectional view of a converter in a platen printing press configuration. [Figure 2] 1 is a schematic perspective view of a suction bar assembly according to one embodiment of the present invention; [Figure 3] FIG. 3 is a schematic perspective view with cutaway showing a suction plate for the suction bar assembly of FIG. 2. [Figure 4A] FIG. 1 is a schematic perspective view of a suction bar assembly attached to a converter. [Figure 4B] FIG. 10 is a detailed cross-sectional view of a suction plate coupled to an air flow duct. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be described in connection with a platen press converter, however, the present invention can be incorporated into other types of printing and folding modules for converters and used to stabilize sheets and blanks during transport.

[0030] 1, there is shown a converting machine 10 in the form of a platen press. The platen press 10 is configured to convert a sheet 12 into a blank 12. As the sheet 12 is conveyed through the converting machine 10, it is converted into the final blank 12. In the context of this application, the term "blank" is used to refer to the initial sheet 12 that is attached to the converting machine 10, the intermediate blank 12 in the converting machine 10, and the final blank 12 produced by the converting machine 10.

[0031] The converting machine 10 is made up of a number of workstations or units, each performing a specific task on the blanks 12. In the conveying direction T of the blanks 12, the converting machine 10 comprises a supply unit 10a, a platen printing unit 10b, a removal unit 10c, a blanking unit 10d, and a waste discharge unit 10e.

[0032] The blanks 12 can then be retrieved from the platen press 10 and introduced into a folding and gluing conversion machine where the blanks 12 are automatically glued and folded to form a folding box. Alternatively, the blanks 12 from the platen press 10 can be used as flat-packed boxes and folded manually.

[0033] The supply unit 10a is configured to receive a stack of blanks 12 and supply them one by one to the platen printing unit 10b. The blanks 12 may be pre-printed with text or decoration, or alternatively, the blanks 12 may have no printed features. The platen printing unit 10b includes a die-cutting tool with cutting and creasing rules configured to cut and crease the sheets 12.

[0034] The removal unit 10c is configured to remove certain waste elements from the cut sheets 12. The blanking unit 10d is arranged after the removal unit in the conveying direction T and is configured to separate the blanks 12 from the cut waste and to arrange the blanks 12 in a stack.

[0035] After the blanking unit 10d, a waste discharge unit 10e is configured to remove further waste elements of the cut sheets 12. The waste discharge unit 10e may comprise a conveyor that moves the waste away from the platen printing press.

[0036] The blanks 12 are transported through the converting machine 10 by a conveyor system 18 including a conveyor belt 20 to which a plurality of gripping units 22 are attached. The gripping units 22 may also be referred to as "gripping bars." The gripping units 22 are configured to grip the leading edges 12' of the blanks 12 and transport the blanks 12 through the converting machine 10 in a guided manner. The gripping units 22 release the formed blanks 12 at the blanking unit 10d. The gripping units 22 are spaced apart by a fixed distance, such that the distance between the leading edges 12' of the blanks 12 is also fixed. The conveyor belt 20 is positioned above the blanks 12 and follows a trajectory above the transport path of the blanks 12. The gripping units 22 transport the blanks 12 between different work stations while momentarily stopping the blanks 12 when the platen printing unit 10b strikes the blanks 12.

[0037] The trailing edge 12'' of the blank 12 is held by a suction bar system 30 comprising at least one suction bar assembly 31. The suction bar system 30 may comprise multiple suction bar assemblies 31. Preferably, the suction bar system 30 is located on the opposite side of the conveyor belt 20 from the gripping unit 22. In this way, interference and space constraints between the two systems 18, 30 can be reduced. In the illustrated embodiment, the suction bar system 30 is located below the blank 12.

[0038] Thus, the converting machine 10 may include a suction bar assembly 31 at each of the platen printing unit 10b, the removal unit 10c, and the blanking unit 10d. Each suction bar assembly 31 is positioned to hold the trailing edge 12'' of the blank 12 at its respective work station. Thus, the trailing edge 12'' of each blank 12 moving through the converting machine 10 is held by the suction bar assembly 31 as converting operations are performed on the blank 12.

[0039] The gripper unit 22 moves through the different work stations and performs a return path from the blanking unit 10d back to the platen printing unit 10b. A suction bar assembly 31 is fixed and located at a position upstream of each of the work stations 10b, 10c, 10d.

[0040] As can be best seen in Figure 4a, the position of the suction bar assembly 31 is preferably adjustable in the conveying direction T. In this way, the position of the suction bar assembly 31 can be adapted to the longitudinal length L1 of the blank 12. A displacement mechanism 35 in the form of a first slide rail 35a and a second slide rail 35b can be arranged at the distal ends 31a, 31b of the suction bar assembly 31 and can engage cooperating connecting parts on the suction bar assembly 31.

[0041] The blank 12 is therefore held firmly and uniformly between the gripping unit 22 and the suction bar assembly 31. This ensures that the punching action performed by the platen printing unit 10b results in cut and crease lines in the correct locations, resulting in accurate geometry of the cut blank 12.

[0042] The combination of the gripping unit 22 and the suction bar assembly 31 forms a positioning system.

[0043] As shown in FIG. 2, each suction bar assembly 31 includes an elongated cross beam 32 having an internal air supply conduit 34 and a suction plate 36 having a suction surface S.

[0044] The suction surface S of the suction plate 36 is configured to apply a suction force to the blank 12 such that the trailing edge 12'' adheres thereto. The suction surface S on the suction plate 36 includes a plurality of suction openings 46 configured to apply a suction force to the blank 12.

[0045] Preferably, only a portion of the longitudinal length L1 of the blank 12 contacts the suction surface S. A rear portion of the blank 12, such as approximately 75% of the longitudinal length L1 of the blank 12 in the conveying direction T, can contact the suction surface S during deceleration of the blank 12. Therefore, a front portion of the blank 12, such as approximately 25% of the longitudinal length L1, does not contact the suction surface S.

[0046] This causes the blank 12 to block the first suction opening 46a of the suction surface S, allowing the rear of the blank 12 to be gripped. Thus, the blank 12 is decelerated and straightened as the suction surface S grips the blank 12. The first suction opening 46a is located at the trailing edge of the blank, near the position where the blank 12 is momentarily stopped. In one embodiment, the first suction opening 46a is located between 0 mm and 50 mm from the trailing edge of the blank 12, where the blank 12 is momentarily stopped.

[0047] The blank 12 is positioned at a predetermined vertical distance relative to the suction surface S of the suction plate 36. This vertical distance is measured between the suction surface S and the blank 12 at its attachment position to the gripping unit 22. The distance between the suction surface S and the blank 12 can be up to 16 mm. The suction force by which the blank 12 is attached to the suction bar assembly 31 is selected to be sufficient to hold the blank 12 flat.

[0048] The suction plate 36 is attached to the elongated cross beam 32. The connection between the suction plate 36 and the elongated cross beam 32 may be made by fasteners 38, such as screws, bolts, or rivets 38. The suction plate 36 may be removably attached to the elongated cross beam 32.

[0049] The suction plate 36 can be manufactured by an additive manufacturing process, i.e., a 3D printing process, which allows for the creation of complex internal air passages within the suction plate 36. Alternatively, the suction plate 36 can be manufactured by other conventional manufacturing methods, including forming sheet metal or machining metal with tooling.

[0050] 2, a plurality of suction plates 36 are mounted on the upper surface of the elongated cross beam 32. However, it is also possible to provide a single suction plate 36 extending the length of the elongated cross beam 32 in the longitudinal direction L. The longitudinal direction L and the longitudinal extension of the suction bar assembly 31 are perpendicular to the conveying direction T.

[0051] The air supply conduit 34 has an air inlet 33 connected to an air flow generating device (not shown). A plurality of air outlet openings 40 are disposed on the upper surface of the elongated cross beam 32. The air outlet openings 40 from the air supply conduit 34 are configured to align with adjacent air inlet openings 42 (see FIG. 3) in the suction plate 36. Preferably, a seal 44 is disposed between the air supply conduit 34 and the suction plate 36. The seal 44 has an opening at a position where the air outlet openings 40 align with the air inlet openings 42.

[0052] The suction openings 46 include a first group of suction openings 46 a and a second group of suction openings 46 b. The first and second groups of suction openings 46 a, 46 b may be arranged with a linear extension that coincides with the longitudinal extension of the suction bar assembly 31.

[0053] Alternatively, the first suction openings 46a can be staggered along the longitudinal extension of the suction bar assembly 31. In this manner, the suction surface S comprises a regular array of suction openings 46a, 46b. This can be achieved by providing a varying distance d1 (see FIG. 3) between the first suction openings 46a and the second suction openings 46b. The second suction openings 46b can also be arranged in a staggered pattern.

[0054] The first and second groups of suction openings 46a, 46b can be positioned upstream of each workstation, allowing the gripping unit 22 to position the leading edge of the blank 12 at the exit of each workstation while the suction openings 46a, 46b apply suction to grip the trailing edge of the blank 12. The first group of suction openings 46a is configured to apply suction to the blank 12 so that the blank 12 adheres to the suction surface S of the suction bar assembly 31. The first group of suction openings 46a is preferably positioned further downstream in the conveying direction T than the second group of suction openings 46b. The suction force is selected to keep the blank 12 flat and prevent the trailing edge of the blank 12 from lifting up.

[0055] The second group of suction openings 46b are configured to create a mass air draw so as to reduce the amount of air located between the blank 12 and the suction bar assembly 31 by suction.

[0056] The pressure in the first group of suction openings 46a is lower than the pressure in the second group of suction openings 46b. In one embodiment, the pressure in the first suction openings 46a can be between 0 mbar and -600 mbar, preferably between -40 mbar and -200 mbar. The pressure in the second suction openings 46b is between 0 mbar and -150 mbar, preferably between 0 mbar and -40 mbar.

[0057] This pressure differential is achieved by the particular flow path design of the suction plate 36. As best seen in Figure 3, the suction plate 36 includes a plurality of main air flow paths 48 extending from inlet openings 42 to outlet openings 43. The inlet openings 42 are connected to the central air supply conduit 34 as described above. The outlet openings 43 may be located below a flange 47 of the suction bar assembly 31. The flange 47 may be in the form of a plate element and may be configured to divert the outlet air flow away from the main air flow paths 48.

[0058] The air flow rate through the first suction opening 46a and the second suction opening 46b can be up to 3000 liters / minute.

[0059] Each main air flow path 48 has multiple sections S1 to S6 having different shapes in the air flow direction F. In the direction from the inlet opening 42 to the outlet opening 43, the main air flow path 48 includes an inlet section S1, a narrowing section S2, a first connection section S3, a distance section S4, a second connection section S5, and an outlet section S6.

[0060] The inlet section S1 can be curved to align the inlet opening 42 perpendicular to the air supply opening 40 of the suction bar assembly 31. The inlet section S1 can direct the inlet air flow Q1 into the main air flow path 48. The inlet section S1 receives the inlet air flow Q1. The pressure in the inlet section S1 is similar to the pressure in the air supply flow path 34, and the velocity v1 of the air flow is selected for the cross-sectional area of the inlet section S1.

[0061] The constriction section S2 is a venturi section configured to accelerate the airflow so that the airflow velocity increases. The constriction section S2 is funnel-shaped so that the cross-sectional area of the main airflow passage 48 gradually decreases in the airflow direction F. The airflow velocity v2 in the constriction section S2 is higher than the airflow velocity v1 in the inlet section S1, while the pressure in the constriction section S2 is reduced to be lower than that in the inlet section S1. The flow rate Q2 through the constriction section S2 is equal to the flow rate Q1 in the inlet section S1.

[0062] The first connection section S3 comprises a connecting duct 50 extending from the main air flow path 48 to the first suction opening 46a. The inlet of the first connection section S3 is located at the outlet of the constricted section S2. The first suction opening 46a is therefore connected to the outlet of the constricted section S2. The reduced pressure at the outlet of the constricted section S2 causes a pressure drop in the first connection duct 50. This generates a suction force through the first suction opening 46a.

[0063] As a result, additional air flow Q2 is drawn into the main air flow path 48 through the first suction opening 46a. This results in an increase in air flow in the connection section S3. The air flow Q3 through the first connection section S3 is equal to the sum of Q1 and Q2. Also, the connection section S3 has a larger cross-sectional area than the constricted section.

[0064] The distance section S4 has a substantially constant cross-sectional area, ensuring that the first suction opening 46a is spaced a distance d1 from the second suction opening 46b. The distance d1 can be selected to be long enough to reduce airflow turbulence at the end of the distance section S4. The distance d1 is preferably less than 10 times the diameter d2 of the main air flow path 48 at the second suction opening 46b.

[0065] The second connection section S5 to the second suction opening 46b is located at the exit of the distance section S4. The cross-sectional area of the distance section S4 is larger than that of the inlet section S1, and the air flow Q5 through the second connection section S5 is larger than the inlet air flow Q1. This causes a high air intake volume Q4 through the second suction opening 46b. In one embodiment, there can be multiple second suction openings 46b connected to each main air flow path 48.

[0066] The outlet section S6 is configured to divert the air flow through the outlet opening 43. The air flow Q5 at the outlet section S6 is the sum of the inlet air flow Q1 and the air flows Q2 and Q4 supplied through the first and second inlets 46a, 46b. [Explanation of symbols]

[0067] 10 Converter 12 Blank material 30 Suction Bar System 31 Suction bar assembly 32 Crossbeam 34 Internal air supply channel 36 Suction Plate 48 Main air flow path 42 Air inlet 43 Air outlet 46a First suction opening 46b Second suction opening 50 First connecting duct F Flow direction S suction surface S2 stenotic section

Claims

1. A suction bar system (30) for a converter (10), comprising: The suction bar system comprises at least one suction bar assembly (31) including a suction plate (36) mounted on a cross beam (32) having an internal air supply channel (34); the suction plate has a suction surface (S) configured to apply a suction force to blanks (12) conveyed in a conveying direction (T) through the converter (10); the suction plate (36) comprises a plurality of main air flow paths (48), each of which comprises an air inlet (42) connected to the air supply path (34) and an air outlet (43), a flow direction (F) extending between the air inlet (42) and the air outlet (43), each of the main air flow paths (48) comprising a first suction opening (46 a) and a second suction opening (46 b), the suction openings (46 a, 46 b) being provided on the suction surface (S), the main air flow path (48) comprising a constricted section (S2) having a first connecting duct (50) connected to the first suction opening (46 a), the constricted section being configured to generate a pressure drop across the first suction opening (46 a).

2. 2. The suction bar system of claim 1, wherein the main air flow path has a cross-sectional area (A2) upstream of the second suction opening (46b) in a flow direction (F) that is greater than the cross-sectional area (A1) of the constricted section (S2).

3. 3. A suction bar system according to claim 1 or 2, wherein the first and second suction openings (46a, 46b) are arranged in separate lines perpendicular to the conveying direction (T).

4. 4. A suction bar system according to any one of claims 1 to 3, wherein the constricted section (S2) of the main air flow path is a venturi section.

5. 5. A suction bar system according to any one of claims 1 to 4, wherein the second suction openings (46b) are connected to the main air flow path via second connecting ducts (51).

6. 6. A suction bar system according to claim 5, wherein the connecting duct (50) to the first suction opening is located upstream of the connecting duct (51) to the second suction opening in the flow direction (F).

7. 7. A suction bar system according to claim 1, wherein the first suction opening (46a) is located further downstream in the conveying direction (T) than the second suction opening (46b).

8. 8. The suction bar system of claim 1, wherein the internal air supply channel (34) has an inlet end (33) connected to an air flow generator and comprises a plurality of distribution outlet openings (40) configured to align with air inlet openings (42) on the suction plate.

9. 9. The suction bar system of claim 1, wherein the suction plate is a separate component and is removably attached to the cross beam.

10. 10. The suction bar system of claim 1, wherein the first suction opening is located at a distance (d1) from the second suction opening, the distance being less than 10 times the diameter (d2) of the main air flow path at the second suction opening.

11. 11. A suction bar system according to any preceding claim, wherein the distance (d1) between the first and second suction openings varies between the main air flow paths.

12. 12. The suction bar system of any of claims 1 to 11, further comprising a deflection flange (47), the outlet opening of the main air flow path being located below the deflection flange.

13. 13. The suction bar system of claim 1, further comprising a displacement mechanism (35) including first and second slide rails (35a, 35b), the suction plate being slidably mounted on the slide rails.

14. 14. A positioning system comprising a suction bar system according to any one of claims 1 to 13 and a gripping unit, wherein the gripping unit (22) is configured to grip and position a front leading edge of a blank, and the suction bar system is positioned such that the first suction opening (46a) is located further downstream in the conveying direction than the second suction opening (46b).

15. 15. The positioning system according to claim 14, wherein a plurality of suction bar assemblies (31) are arranged along the conveying direction (T).

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