Lifting suction cup with a pneumatically controllable suction cup

Abstract

Suction cup for separating a sheet from a stack of sheets, wherein the lifting suction device has a suction cup (26) made of flexible material, wherein the suction cup (26) has a suction opening (43) which is enclosed by a double-walled bellows (30) and the bellows (30) has at least one suction chamber (46), characterized by that a piston (29) carries a support plate (32) on which the suction cup (26) is arranged.

Description

[0001] The invention relates to a suction lifter with a pneumatically controllable suction cup. Such suction lifters are primarily used in sheet-processing machines, such as printing presses or die-cutting machines, for separating sheets from a stack of sheets.

[0002] US 7,014,185 B2 discloses a lifting suction device which essentially consists of a cylinder and a tubular piston coaxially surrounding it. The tubular piston has suction nozzles at one end for sucking a sheet from a stack of sheets. The sheet is sucked in when the tubular piston is in an extended position. When the nozzles are covered, a negative pressure increases in the cylinder, which causes the piston to be lifted together with the sheet. Ventilation of the cylinder causes the sheet to be released. The ambient air now sucked in through the nozzle reduces the negative pressure in the cylinder, so that the piston is extended to suck in the next sheet and rests on the stack of sheets.

[0003] From DE 19628943 C2 it is known to design a suction cup of a separating suction cup as an elastic bellows suction cup.

[0004] DE 19752491 C2 shows a suction cup in which a variable suction chamber for lifting the suction cup is delimited by a bellows.

[0005] The invention is based on the object of creating a lifting suction device whose suction cup is pneumatically controllable.

[0006] The object is achieved according to the invention by the features of claims 1 to 3.

[0007] A particular advantage of the invention is that the suction cup can be controlled separately, independent of the lifting movement of the suction device. This allows the suction cup to be gently placed on the sheet to be lifted. This prevents marks on the sheet and also prevents suction through the sheet, which would otherwise result in the simultaneous suction of a second sheet underneath.

[0008] The subclaims describe further advantageous embodiments of the suction cup, which make it possible for it to be adapted to arches that are inclined to the horizontal or to curved arches.

[0009] Embodiments of the invention are illustrated in the drawings and are described below. Fig. 1 a sheet processing machine in section in a schematic representation, Fig. 2 a vacuum cleaner in section in a schematic representation, Fig. 2a-c the suction cup in different working positions, Fig. 3 a suction cup of the lifting suction device in section in a schematic representation, Fig. 4 a section through the suction cup with two bellows suction chambers Fig. 4a a cross-section through the suction cup with two bellows suction chambers Fig. 5 a cross-section through a suction cup with several bellows suction chambers

[0010] A sheet processing machine 7, e.g., a die cutter or printing press 1, has a feeder 2 and a delivery 6. In a printing press, the sheets 7 are removed from a sheet stack 8 and fed singly or in batches via a feed table 9 to printing units 3 and 4. In a printing press 1, these each contain a plate cylinder 11, 12 in a known manner. The plate cylinders 11 and 12 each have a device 13, 14 for attaching flexible printing plates. Furthermore, each plate cylinder 11, 12 is assigned a device 16, 17 for semi- or fully automatic printing plate changing.

[0011] The sheet stack 8 rests on a stacking plate 10 that can be lifted in a controlled manner. The sheets 7 are removed from the top of the sheet stack 8 by means of a suction head 18, which, among other things, has a number of lifting and dragging suction devices 19, 21 for separating the sheets 7. Furthermore, blowing devices 22 are provided for loosening the upper sheet layers of the scanning elements 23 for stack tracking. A number of lateral and rear stops 24 are provided for aligning the sheet stack 8, in particular the upper sheets 7 of the sheet stack 8.

[0012] The suction cup 19 is designed according to Fig. 2-2c is designed as a so-called spring suction device, i.e., the vacuum level required for lifting a suction cup 26 is only generated by covering a suction opening 43 or nozzle 27 by the sheet 7. These are arranged on the suction cup 26 and act on a surface of the sheet 7.

[0013] The suction cup 19 consists as in Fig. 2, consists of a cylinder 28, which serves to guide a cylindrical piston 29, which coaxially surrounds the cylinder 28 from the outside. The piston 29 carries a support plate 32 at its lower end 31 facing the bend 7, on which the suction cup 26 is arranged. The piston 29 thus has, together with the cylinder 28, a rotation axis 33. In a suction chamber 34 formed jointly by the cylinder 28 and the piston 29, a compression spring 36 is arranged, which has the task of extending the piston 29 downwards towards the bend 7. A stop 37 with a damper 38 limits the stroke of the piston 29 in an extended end position. A suction air connection 39 connects the suction chamber 34 to a suction air source 41 via a rotary valve 40.

[0014] The support plate 32 has a first connecting bore 42, which connects the suction chamber 34 to a suction opening 43 of the suction cup 26. The suction cup 26 is designed as a double-walled bellows suction cup 30. This measure surrounds the suction opening 43 by a suction chamber 46. A second connecting bore 44 in the support plate 32 connects the suction chamber 46 of the double-walled bellows suction cup 30 to controlled suction air from the rotary valve 40. The second connecting bore 44 has a tube 48 arranged on the rotation axis 33, which is fastened to the support plate 32. The tube 48 is coaxially surrounded by a tube 49, which is arranged on the cylinder 28. The tube 48, together with the piston 29, is longitudinally displaceable relative to the tube 48, so that the two tubes 48 and 49 are mounted telescopically displaceable within each other.

[0015] Fig. 2 shows the lifting suction device 19 in an upper position in which both the suction chamber 34 and the chamber 46 are subjected to negative pressure.

[0016] In a next step, the raised sheet 7 is removed from the suction cup 26, so that the suction chamber 34 is ventilated. Suitable mechanical, magnetic, or pneumatic means hold the piston 29 in the upper position. An example is shown in DE 4234184 C2. After releasing the holding means, the piston is moved downwards by its own weight and the force of the compression spring 36 until a collar 51 of the piston 49 is released from the stop 37, as shown in Fig. 2a. The rotary valve 40 now ventilates the suction chamber 46 of the suction cup 26, so that the latter extends due to the tensioning force of the chamber walls and the suction cup 26 as shown in Fig. 2b, is placed on the sheet 2. Any excess pressure that may arise in the chamber 46 can escape via a throttle with a check valve 52.

[0017] In order to suck in the new sheet 7, the rotary valve 40 supplies the suction chamber 46 and the suction space 34 with negative pressure, so that they are Fig. 2c shown and the suction cup 26 and the piston 29 are raised to the upper position.

[0018] In an embodiment according to Fig. 4, Fig. 4a, it is provided that the double-walled bellows 30 has at least two suction chambers 53, 54, each with a suction opening 56; 57.

[0019] Suction chambers 53, 54 can be supplied with suction air independently of suction opening 27. This measure allows a suction cup 26 placed obliquely on a sheet to exert a suction effect on sheet 7 via one of suction openings 56 or 57, even if the main suction opening 27 is not yet completely covered. When one of the suction openings 56 or 57 is covered, the bellows in the area of suction opening 56 or 57 simultaneously contracts, thus lifting the sheet.

[0020] In an embodiment according to Fig. 5, it is provided that the double-walled bellows 30 has a plurality of suction chambers 53, 54 with suction openings 56, 57 and closed suction chambers 61, which are arranged alternately around the main suction opening 27. The suction chambers 53, 54 with suction openings 56, 57 serve to suck in the sheet without leakage, while the closed suction chambers 61 can be supplied with control air, i.e., either blowing or suction air, in order to influence a stroke of the bellows suction device 30.

[0021] In an arrangement of several closed suction chambers 61, it can be provided that these are controlled one after the other via the rotary valve 40, for example in time with the sheet processing machine, so that a targeted inclination of the suction cup 26 is possible.

[0022] In the embodiment according to Fig. 5 can the Fig.The working cylinders 28, 29 shown in Figures 2-2c are omitted since the lifting movement is controlled by the pneumatic actuation of the closed suction chambers 61. List of reference symbols 1 printing press 2 investors 3 printing unit 4 printing unit 5 . / . 6 booms 7 sheets 8 sheet stacks 9 Feed table 10 stacking plates 11 plate cylinders 12 plate cylinders 13 Pressure plate fastening 14 Pressure plate fastening 15 . / . 16 printing plate changers 17 printing plate changers 18 Suction head 19 lifting suction cups 20 . / . 21 trailing vacuum cleaners 22 Blowing device 23 Touch element 24 stops 25 . / . 26 suction cup 27 nozzles (26) 28 cylinders (19) 29 pistons (19) 30 bellows suction cups 31 End (29) 32 support plate 33 Rotation axis (28, 29) 34 Suction chamber (28, 29) 35 . / . 36 compression spring 37 stop 38 dampers 39 Suction air connection 40 Rotary valve 41 . / . 42 first connecting hole (32) 43 Suction opening 44 second connecting hole (32) 45 . / . 46 Suction chamber 47 Suction air source 48 pipe 49 pipe 50 . / . 51 collars (29) 52 throttle with check valve

Claims

[1] Suction cup for separating a sheet from a stack of sheets, wherein the lifting suction device has a suction cup (26) made of flexible material, wherein the suction cup (26) has a suction opening (43) which is enclosed by a double-walled bellows (30) and the bellows (30) has at least one suction chamber (46), characterized by , that a piston (29) carries a support plate (32) on which the suction cup (26) is arranged. [2] Suction cup for separating a sheet from a stack of sheets, wherein the lifting suction device has a suction cup made of flexible material, wherein the suction cup (26) has a suction opening (43) which is enclosed by a double-walled bellows (30), and the bellows (30) has at least one suction chamber (53, 54), characterized by , that the suction chamber (53, 54) has at least one additional suction opening (56, 57) and a piston (29) carries a support plate (32) on which the suction cup (26) is arranged. [3] Suction cup for separating a sheet from a stack of sheets, wherein the lifting suction device has a suction cup made of flexible material, wherein the suction cup (26) has a suction opening (43) which is coaxially enclosed by a double-walled bellows (30), characterized by , that the bellows (30) is divided into several suction chambers (53, 54) with additional suction openings (56, 57) and at least one closed suction chamber (61, 62). [4] Lifting suction device according to claim 3, characterized by that several closed suction chambers (61, 62) are arranged alternately with the suction chambers (53, 54) coaxially around the suction opening (27) and can be successively supplied with suction air from a common rotary valve (40). [5] Lifting suction device according to claim 3, characterized by that several closed suction chambers (61, 62) are arranged alternately with the suction chambers (53, 54) coaxially around the suction opening (27) and can be jointly supplied with suction air. [6] Lifting suction device according to one of the preceding claims, characterized by that the suction chamber (46) has a check valve (52). [7] Punch with a suction cup according to one of claims 1 to 6. [8] Sheet-fed rotary printing machine with a lifting suction device according to one of claims 1 to 6.

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