GB2343886A - Braking device for sheet material in a printing press - Google Patents

Abstract

A braking device for sheet material in an offset sheet fed printing press is described. The device has a plurality of braking units (5) with wear-free suction sealing which permits a noticeably improved braking action. This is provided by providing, on a drive system (4) for rotating a suction ring (19), a collar (35) of the suction ring (19), concentrically to the collar (35) a bearing (31), and concentrically to the bearing (31) a suction body (20, 21) so that between the suction ring (19) and the suction body, a contact-free seal (34) is arranged, while enabling suction (braking) to be applied to a sheet passing over the braking unit (5) as apertures (20) in the suction ring (19) pass across corresponding apertures (33) in the suction body (30) control disc (21).

Description

2343886 - I - BRAKING DEVICE FOR SHEET MATERIALS IN A PRINTING PRESS This

invention relates to a braking device for sheet materials in a printing press. 5 A device of this type is known from DE 34 37 584 Al. Rotating braking rollers are arranged on a cross-member running transversely to the feed direction of the sheet material in front of a delivery pile, wherein separate suction bodies with corresponding suction feeds are fitted to the braking rollers. The suction bodies are neighbouring the exterior end face regions of the braking rollers and the peripheral surface of the braking roller has lateral apertures which project into the end face wherein the suction body has a lateral air outlet opening which stands functionally connected in one region with the braking roller. In order that the braking roller can rotate freely, a small slot is necessarily required between this and he suction body which is fast with respect to the frame. By means of slight positional alteration of the braking rollers (braking rollers can wander in the axial direction of the drive shaft) and/or because of wobbling movement on the drive shaft (with resulting wear on the end faces of the braking rollers), this slot can itself enlarge.

Air losses result from an increase in the slot which act negatively on the braking power of the device as such, as well as on the sheets to be deposited. The braking power can accordingly vary from one sheet to the subsequent sheet.

In a further development, a leaf spring is fitted to this braking roller which presses the suction body as a counterforce, especially its channel body against the braking roller in order thereby to seal the slot. Since between a rotating braking roller and a suction body fast with respect to the frame, a relative movement takes place, friction forces or friction moments arise which provide losses in mechanical work (development of heat). The result is that on at least one component, shape-changing wear (dents, scratches, corrugations, fissures) arise and/or erosive wear (attrition). These types of damage are yet further increased if, for example, paper dust or powder comes in between the touching regions of suction body and braking roller.

The present invention provides a braking device for sheet material in a printing press which is adapted to be arranged below a circulating chain conveyor system and there extend transverse to the feed direction in front of a delivery pile, the unit comprising a guide cross-member movable in or counter to the feed direction of the sheet material, a plurality of braking units mounted on the cross-member, means for subjecting each braking unit to suction and to subject a rotatable member thereof to rotation, each unit comprising a suction ring having a central collar for engagement with the means for subjecting the member to rotation, a bearing arranged concentrically to the collar a suction body which can be fixed to the guide cross-member arranged concentrically to the bearing, that the suction body having a suction channel linked with a pneumatic system, a control bore fitted thereto as well as at least one opening arranged radi-ally in an upper segmental region, the suction ring having peripheral surface for carrying the sheet material and perforated by at least one row of openings, wherein the openings of the rotating suction ring can be functionally connected with at least one opening of the suction body via a contact-free seal around the periphery, the seal being in the form of a narrow axial circular ring slot.

Such a braking device for sheet material in a printing press can avoid the above-noted disadvantages, and, in particular, provide wear-free sealing and permit a noticeably improved braking action.

A first advantage of the braking device of the invention is to be seen in that the it has a contact-free - and accordingly wear-free - circulating seal as an axial, circular ring slot with an essentially constant slot width between a rotating suction ring and a suction body or its control disc fast with respect to the frame. This circulating seal is characterised by a defined extremely small circular ring slot as an air slot which always effects a constant braking power on the braking unit.

It is further of advantage that in the case of a covering (with a sheet material) of the activated openings in the rotating suction ring, a drop in pressure resulting therefrom arises in delayed fashion. A vacuum is not exclusively applied to a control bore, but distributes itself on the peripheral side (with decreasing vacuum) into a circular segment in the circular ring slot (air slot) near the debouching control bore.

This has the advantage that the sheet material in the feed direction around the periphery of the braking device after passing the control bore is guided under friction for a defined path. 5 Likewise advantageous is the fact that a rotatable suction ring and a suction body fast with respect to the frame have a common mounting. Thereby, among other things, the extremely small circular ring slot also defines the contact-free and wear-free sealing.

In addition to all of this, it is advantageous that the suction rings of the braking device can be set for one side printing and also for perfect printing, wherein the contact-free principle of sealing is maintained. For single side printing with an unprinted underside of the sheet material, suction rings can be used with single row and/or multiple rows of openings. For perfect printing with sheets printed on the underside, it is preferred to use suction rings with a single row of openings. This has the advantage that the braking unit can be constructed axially.with very narrow dimensions.

A further advantage is given by the fact that with a two-part construction of fixable suction body with a control disc fitted thereto, this control disc is connected releasably with the suction body and accordingly is easily exchangeable. This is particularly relevant in a changeover from single side printing to perfect printing and vice versa, or with changed printing subject-on the underside.

Finally, it is of advantage that in the feed direction upstream of each braking device, a suction plate is arranged which serves for sucking on the sheet material fed from a gripper system. Thereby the braking action of the braking unit is noticeably improved. The sheet material additionally can be stretched transversely to the feed direction. For this, at least the braking units neighbouring the side frames, starting from the centre of the press, are directed obliquely towards 5 externally adjustable suction plates.

The invention is illustrated by way of example with reference to an embodiment diagrammatically shown in the accompanying drawings in which:

Figure 1 shows a braking unit according to the present invention in side view Figure 2 a braking unit in front view (direction of view counter to the feed direction) Figure 3 a delivery for sheet material, and Figure 4 a suction ring of the braking unit.

Referring to the drawings, a delivery 22 is arranged downstream (as seen in the feed direction 3) of a final printing unit or a treatment station, e.g. a varnishing unit of an offset printing press for multicolour printing. The delivery 22 consists essentially of an endlessly circulating chain conveyor system 25 with gripper systems 2 arranged thereon. The gripper systems 2 transport a sheet material 1 in the feed direction 3 from the last printing unit or the treatment station coming past a fixed modularly constructed sheet guidance unit 23 as well as a flexible sheet guidance unit 24 shiftable in or counter to the feed direction 3 dependent upon the format via a multiple arrangement of braking units 5 set transverse to the feed direction 3 to a delivery pile 29, where they deposit the sheet material 1 against front edge stops 27 and rear edge 6 stops 16.

The braking units 5 are shiftable analogously to the sheet guiding unit 24 in or counter to the feed direction 3 (direction of movement 18) dependent upon the length format by means of guide slots and longitudinal drives, e.g. a threaded spindle. For supporting the deposition process of the sheet material 1, in an area above the delivery pile 29, there is arranged a controllable blowing unit 26. Furthermore, the delivery 22 has an auxiliary pile device 28 for nonstop pile change.

In Fig. 1, a braking unit 5 is shown which has a suction ring 19 arranged on a drive system 4. Upstream in the feed direction 3 relative to each braking device 5 is a suction plate 7 with at least one opening which serves for sucking on (catching) and if desired stretching of the sheet material 1 fed by the gripper system 2.

Braking unit 5 and suction plate 7 have a suction channel 6 wherein a common suction channel 6 can supply the braking unit 5 and the suction plate 7 for example with suction. However preferred is that each braking unit 5 as well as suction plate 7 is linked in each case with its own suction channel 6. The suction channels 6 are functionally connected with one or several suction sources of a pneumatic system and are linked with a suction body 30 (base body) of the braking unit 5. Preferably the suction body 30 of the braking unit 5 and the suction plate 7 are constructed as a unitary component.

A separate air supply for braking unit 5 and suction plate 7 has the advantage that the pressure conditions are individually controllable. Below the braking unit 5 are arranged rear edge stops 16 which, on non-stop pile change, or on raising or lowering the main pile, are 7 movable in the vertical direction 17.

Parallel to the drive system 4, for example a drive shaft or a separate electrically controllable individual 5 drive, there is arranged a guide cross-member 9 (transverse to the feed direction 3). At least the guide cross-member 9 is taken up on the A- and B-side of the side frame in each case in a guide carriage, wherein each guide carriage is shiftable in the direction of movement 18. The guide cross-member 9 carries the braking unit 5, especially the mounted suction bodies 30 and is received in a housing 8. The housing 8 extends between the side frames and is movable in common with drive system 4, guide cross-member 9 and braking units 5 for longitudinal format adjustment in the direction of movement 18. Within the housing 8, there is fixed at each braking unit 5 a drive motor 13 which is linked with a gear block 12. This gear block 12 carries a pinion 11 which is functionally connected with a rack 10 arranged parallel to the guide cross-member 9 on the inner wall of the housing 8. The housing 10 has a housing opening 14 in the feed direction 3 through which the suction bodies 30 of each braking unit 5 project from the guide cross-member 9 in the feed direction 3.

The housing opening 14 extends transverse to the feed direction 3 across the entire width of the housing so that all braking units 5 are adjustable transversely to the feed direction 3. A flexible seal 15, e.g. a brush seal is integrated into the housing opening 14.

The suction ring 19 of the braking unit 5 is fitted to the drive system 4. For this, the suction ring 19 has a preferably integral collar arranged on the drive system 4 which carries a concentric bearing 31, preferably a single or multiple row ball bearing. Arranged concentrically on the mounting 31 is the suction body 30 with a control disc 21 fixable to the guide cross-member 9. The suction body 30 with suction channels 6 is pneumatically functionally connected with the control disc 21, wherein the control disc 21 is connected, for example, releasably with the suction body 30 (two part construction). In Fig. 2, the suction body 30 and the control disc 21 are illustrated in this two part construction. Alternatively, the control disc 21 can be realised as an integrated component in the suction body 30. Arranged concentrically to the control disc 21 (or to the suction body 30) is the peripheral surface of the suction ring 19 carrying the sheet material 1. The suction body 30 has the suction channel 6 which is functionally connected with a control bore 32 of the control disc 21. The control bore 32 is functionally connected with at least one opening 33 arranged on the periphery of the control disc 21. The openings 33 are, taking into account the sheet material 1 which is to be braked, arranged radially spreading in the upper segmental region of the control disc 21. The suction ring 19 has on its periphery at least one row of openings 20 which can be brought into functional connection with at least one row of openings 33 of the control disc 21. Between the inner side of the peripheral surface of the suction ring 19 and the surface of the control disc 21 (or of the suction body 30), an axial, circular ring slot is constructed as a very small air slot which functions as a contact-free seal 34 around the periphery.

In the two part construction of fixable suction body 30 and releasably arranged control disc 21, the control disc 21 is easily exchangeable. On changeover of the mode of operation from single side printing to perfect printing, as well as the other way round or with a changed printing subject on the underside of the sheet material 1, this is particularly relevant.

Thus, for example, a first control disc 21 with at least one two-row adjacent one another radially arranged opening 33 (for single side printing) can be exchanged for a second control disc 21 with at least one radial single row arranged opening 33 (for perfect printing). In this connection, especially also the suction ring 19 (with collar 35) as well as if appropriate the bearing 31 can be exchangeable by pulling off from the drive system 4. Accordingly, the first control disc 21 is functionally connected with at least one two-row arranged opening 33 with a suction ring 19 with on the peripheral side two-row openings 20 arranged, or the second control disc 21 with a single row of at least one arranged opening 33 is functionally connected with a suction ring 19 with openings 20 arranged around the periphery in one row. The suction body 30 is thereby always connected with the guide cross- member 9 and serves at least as a base body for the receipt of the control disc 21 to be fitted.

In a preferred further development, the suction plate 7 is constructed movably adjustably. For this, at least one braking unit 5 in the region of the centre of the press is constructed with a flush arrangement of the openings in the feed direction 3 and in each case depending upon the number of the braking units 5 used, at least the braking units 5 fitted to the side frames can be constructed with movable suction plates 7. For this, the suction plates 7 are movably adjustable with their openings starting from the centre of the press in each case obliquely outwardly towards the neighbouring side frame at an acute angle. Because of the oblique position of the openings of the suction plate 7, a pulling force acts on the sheet material 1 transverse to the feed direction 3 whereby this is stretched taken across the width.

The mode of operation is as follows: in print operation, the sheet material 1 is fed by the gripper systems 2 to the delivery pile 29 and deposited there. During the transport in the feed direction 3, each sheet material 1 is sucked by the suction plate 7 on its underside and guided with the rear edge frictionally across the braking unit 5. Thereby the sheet material is sucked on by the openings 20 of the suction ring 19 which stand in functional connection with the openings 33 of the control disc 21 and is stretched. After opening the gripper system 2, the sheet material 1 is braked in terms of its speed and fed to the front edge stops 27 of the delivery pile 29. Because of the special construction of the seal 34, each sheet material 1 can be braked with a braking action which remains the s ame. In addition to this, the braking power at the suction rings 19 as well as the suction power on the suction plates 7 can be controlled, preferably individually, via the pneumatic system fitted.

Claims (9)

1. A braking device for sheet material in a printing press which is adapted to be arranged below a circulating chain conveyor system and there extend transverse to the feed direction in front of a delivery pile, the unit comprising a guide cross- member movable in or counter to the feed direction of the sheet material, a plurality of braking units mounted on the cross-member, means for subjecting each braking unit to suction and to subject a rotatable member thereof to rotation, each unit comprising a suction ring having a central collar for engagement with the means for subjecting the member to rotation, a bearing arranged concentrically to the collar a suction body which can be fixed to the guide cross-member arranged concentrically to the bearing, that the suction body having a suction channel linked with a pneumatic system, a control bore fitted thereto as well as at least one opening arranged radially in an upper segmental region, the suction ring having peripheral surface for carrying the sheet material and perforated by at least one row of openings, wherein the openings of the rotating suction ring can be functionally connected with at least one opening of the suction body via a contact-free seal around the periphery, the seal being in the form of a narrow axial circular ring slot.

2. A braking device according to Claim 1 wherein the suction body has in the axial direction of the drive system several radial openings in the upper segment region which cooperate with multi- row arranged openings of the rotating suction ring.

3. A braking device according to Claim 1 or 2 and including, arranged prior to the braking unit in the feed direction, a pneumatically subjectable suction - 12 plate with openings.

4. A braking device according to Claim 3 wherein the suction body and suction plate form a single piece base 5 body of each braking unit.

5. A braking device according to Claim 3 or 4 wherein the suction plate is adjustable to lie at an angle starting fromhe centre line of the press and running obliquely outwardly toward the neighbouring side frame, whereby to exert a lateral stretching action on the sheet.

6. A braking device according to any one of Claims 1 to 5 wherein the suction body having the suction channel is connected releasably with a control disc having the control bore.

7. A braking device according to Claim 6 wherein a control disc with at least one single row arranged opening-and a suction ring with single row arranged openings functionally connected therewith are exchangeable against a control disc and a suction ring, each with two- row arranged openings.

8. A braking device according to Claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

9. An offset sheet-fed printing press incorporating a braking device according to any one of the preceding Claims.