Device for braking sheets in a delivery of a sheet-processing machine

Abstract

Device for braking sheets in a delivery of a sheet-processing machine, comprising several suction stations which are slidably arranged and axially spaced apart from one another on a traverse extending across the width of the machine, and comprising a positioning means for the sequential positioning of the suction stations, which includes a drive and an access station displaceable by means of the drive, which carries a coupling or coupling part by means of which the access station can be selectively coupled to any of the suction stations, wherein the drive comprises a hollow cylinder and a piston slidably guided in the hollow cylinder, which is connected to the access station, wherein at least one fluid supply means is assigned to the hollow cylinder, which sets alternating fluid pressures in the hollow cylinder for displacing the piston, such that the respective fluid pressure applied to one side of the piston is not equal to the respective,The fluid pressure is applied on the other side of the piston.

Description

[0001] The invention relates to a device for braking sheets in a delivery of a sheet-processing machine.

[0002] From DE 103 61 204 A1 a device for the axial adjustment of brake stations is known, in which a guide traverse is designed as a hollow cylinder and accommodates in its interior the actuating elements for the brake stations driven by threaded spindles.

[0003] From DE 198 35 003 A1, a bow brake with a brake element that can be exchanged for a support element is known. A support strip can be used at the brake stations instead of the normal perforated strip. However, only a specified width of brake elements or support elements can be used here.

[0004] A sheet brake is known from DE 10 2005 016 783 A1, in which sheet supports are arranged between the brake elements. The sheet supports comprise a first and a second nozzle array, with the nozzle arrays generating different airflow volumes. A disadvantage of this solution is that the sheet supports must be removed when adjusting the format due to the risk of collision. Furthermore, scratches can occur because, unlike sheet guide plates, there is no larger, closed surface. Sealing the space between the sheet brakes also prevents the unimpeded flow of air from the sheet guide plates and the blowing frame. This reduces the processing speed. The constant airflow is also a disadvantage, hindering sheet start-up.

[0005] From DE 10 2010 002 500 A1, a device for handling, namely for guiding and / or braking, sheets in a sheet-processing machine is known, in which an adapter module can be assigned to a basic module of a sheet brake. Differently designed suction fins can be assigned to the adapter module, which can be operated with blown air instead of suction air. The suction fins supplied with suction air have a friction-enhancing coating and are intended to have a braking effect on the sheet.

[0006] From DE 10 2011 080 196 A1, a delivery unit of a sheet-processing machine with a sheet brake is known, which has adjustable braking stations. Each braking station has a support element whose connecting surface can be interchangeably assigned a functional unit with a pneumatic or mechanical support element.

[0007] From DE 40 35 035 A1, a device for the axial adjustment of suction rings in the delivery units of printing presses is known, comprising an access station that is slidably arranged on an adjusting rod designed as a linear bearing unit. The access station can be coupled to the suction rings via a guide carriage for positioning them transversely to the sheet transport direction. The positioning movement of the access station or the guide carriage is transmitted to the respective selected suction ring.

[0008] The disadvantage of the devices mentioned is that the devices intended for adjusting the brake bodies are elaborately designed, because either separate drive elements are assigned to each brake body or the common drive consists of many individual parts.

[0009] The invention is based on the objective of creating an alternative device for braking sheets in a delivery system. In particular, the device should be cost-effective and less prone to malfunctions.

[0010] According to the invention, the problem is solved by a device with the features of the independent device claim. Advantageous embodiments are described in the dependent claims.

[0011] The invention has the advantage that a large number of suction stations can be positioned with a simple drive system. Positioning the suction stations is simplified. The device for braking sheets is integrated into a delivery unit and can be part of a sheet-processing machine, for example, a printing press, in particular a sheetfed offset rotary printing press or a die-cutting machine.

[0012] The invention will be explained below by way of example.

[0013] The device for braking sheets is integrated into the delivery unit of a sheet-fed printing machine, particularly a sheet-fed offset rotary printing press, preferably in a modular or in-line configuration. The delivery unit contains a sheet-carrying conveyor system that transports the sheets printed, varnished, finished, etc., in the printing press to a delivery stack. This sheet-carrying system is preferably designed as a chain conveyor system with two delivery chains, each guided laterally on the delivery frame, between which gripper carriages are arranged. The gripper carriages have sheet-holding systems with which the sheets to be transported are gripped at the leading edge. The gripper carriages are guided by the delivery chains along a track in the sheet-feed direction until they reach the delivery stack, where the gripper carriages release the sheets for placement.On the sheet conveying path to the delivery stack, at least one mechanical sheet guide element, preferably one or more sheet guide plates, is arranged in the delivery area below the sheet transport level. This guide element guides the sheets on their way to the delivery stack. The sheet guide plate has an at least approximately closed surface for sliding and / or floating guidance of the sheets. The sheet guide plate may be provided with a paint-repellent coating. Furthermore, nozzle openings for pneumatically guiding the sheets may be assigned to the sheet guide element, in particular the sheet guide plate.

[0014] In the delivery unit, a braking device is positioned upstream of the delivery stack in the sheet-travel direction. This device takes the sheets to be deposited from the gripper carriages and, after their release, decelerates them from machine speed to the depositing speed. Following deceleration by the braking device, the sheets are aligned against front, rear, and / or side edge stops and neatly deposited onto the delivery stack. The delivery stack is preferably lowered by a stack lift drive during the sheet depositing process such that the surface of the delivery stack forms an at least approximately constant depositing level for the incoming sheets. The braking device comprises at least two suction stations, which are arranged to be axially displaceable, i.e., transverse to the sheet-travel direction. However, several such suction stations can also be used, for example, at least three, or exactly three, four, five, or even more depending on the format.The suction stations are preferably placed on a lateral, usually unprinted, edge of the sheet, on unprinted corridors, and / or on sufficiently dried ink areas. Unneeded suction stations can be deactivated and / or moved out of the sheet area. The suction stations are arranged in a sliding manner along a crossbeam extending across the width of the machine and are axially spaced from one another.

[0015] At least one, preferably several or all, suction stations can each accommodate at least one braking element, preferably a suction belt, which is mounted circumferentially around one or more axes of rotation. Such braking elements can also be designed as suction rings. The braking element, in particular the suction belt, preferably interacts pneumatically with the sheets transported by the braking device. In particular, the sheets are brought into contact with the braking element, in particular the suction belt, and / or held in contact by suction air, so that contact is established between the braking element, in particular the suction belt, and the respective sheet. The braking element, in particular the suction belt, moves at least temporarily at a lower speed than the machine speed and decelerates each sheet released by the gripper carriage accordingly.The braking element, in particular a suction belt, can be assigned at least one drive that drives or decelerates it at a constant or variable speed reduced compared to the machine speed. Preferably, however, the braking element, in particular a suction belt, is operated dynamically and / or periodically between at least approximately the machine speed and a lower depositing speed. With multiple braking elements, in particular suction belts, the drive can also drive or decelerate several or all of the braking elements, in particular suction belts. Alternatively, each braking element, in particular a suction belt, can be assigned a separate drive.In a further development, the braking element, for example a suction ring or suction band, acts in conjunction with another braking element, for example a suction ring or suction band, at a further suction station, through an arrangement diverging with respect to the sheet travel direction, exerting a transverse tension on the respective sheet to be laid down. The braking elements, in particular the suction rings or suction bands, can be assigned to the suction stations in an interchangeable manner.

[0016] The braking device is in particular housed in a separate frame and is designed to be movable in and against the direction of sheet travel in order to adjust to different sheet formats.

[0017] The braking device comprises a positioning means for the sequential positioning of the suction stations, which includes a drive and an access station that can be moved by means of the drive. The access station carries a coupling or coupling component by means of which the access station can be selectively coupled to any of the suction stations.

[0018] The drive comprises a hollow cylinder and a piston slidably guided within the hollow cylinder, which is connected to the access station. The hollow cylinder is associated with at least one fluid supply element that establishes varying fluid pressures within the hollow cylinder to move the piston. The fluid supply element is designed to establish a fluid pressure on one side of the piston that differs from the fluid pressure on the other side. The fluid supply element can be configured to establish the fluid pressure on one or both sides of the piston. In the case of establishment on both sides, the adjustment is made either alternately, with one side always in contact with the environment, or simultaneously, for example, by applying positive pressure to one side and negative pressure to the other.

[0019] The hollow cylinder can be pressurized with fluid, in particular compressed air or suction air, on one or both sides and can accordingly be designed as a single-acting or double-acting cylinder.

[0020] The coupling is preferably designed as a magnetic coupling or includes a magnetic coupling element. The coupling can also be designed as a mechanical coupling and include a pin or a lever.

[0021] The braking device can include a fixing device designed as a common fixing device for all suction stations, with which all suction stations can be fixed to or released from the traverse via a single adjustment action. Such a clamping device can have a clamping element extending across the machine width or the width of the maximum sheet format that can be processed by the sheet-processing machine.

[0022] Preferably, each suction station has a unique, and in particular one-to-one, code that enables identification of the respective suction station. Identification may be necessary, for example, during initial commissioning or in the event of system crashes. The possibility of identification also proves advantageous for monitoring purposes. To enable identification, a reader is preferably designed or arranged on the access station, which can be moved with the access station.

[0023] The braking device preferably includes a linear measuring device for detecting the positions of the suction stations.

[0024] A shaft drive can be used to drive the braking elements, the drive element of which consists of a rotaryally driven square shaft extending across the width of the sheet-processing machine. Preferably, all braking elements assigned to the suction stations, in particular suction belts, are driven together by a rotational movement of the drive shaft, in particular a square shaft, arranged across the machine width. The square shaft of the square shaft drive is arranged parallel to the crossbeam. The square shaft is in contact, in particular, with the surfaces of the output elements on the base body of each suction station that receive the square shaft. The surfaces of the output elements of the suction stations slide accordingly on the outer contour of the square shaft during its axial adjustment.

[0025] Each suction station of the device for braking arcs is associated with a pneumatic connection, preferably designed as a suction air connection, which is connected to at least one, for example, adjustable vacuum generator. The suction air connection can also be designed as a compressed air connection for generating a vacuum at the suction station according to the ejector principle.