Apparatus for conveying sheets through a printing machine

Abstract

An apparatus for conveying sheets through a printing machine allows driving a sheet transport belt obliquely with respect to the conveying direction with a simple configuration. At least one deflection roller has a conical running surface (with or without a crowned face). At least one belt travels over deflection rollers, including the at least one deflection roller, and the belt running direction is oblique with respect to the sheet transport direction.

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The invention relates to an apparatus for conveying sheets through a printing machine. The apparatus has at least one belt which is laid over deflection rollers, the belt running direction being oblique with respect to the sheet transport direction. The apparatus can be used, in particular, during the conveying of sheets onto a stack in a printing machine.

German published patent application DE 39 39 212 A1 describes a sheet guiding and braking device in the delivery of printing presses, in which sheet guide rods are arranged lying next to one another in the conveying direction in the region of printfree corridors. The guide rods have longitudinal grooves which are arranged obliquely and have vacuum applied to them. Furthermore, the device comprises suction rolls with suction rings which have a common drive shaft perpendicular to the conveying direction. Like the longitudinal grooves, the suction rings are arranged obliquely with respect to the conveying direction. The sheets are subjected to a tensile force transversely with respect to the conveying direction by the oblique positioning of the longitudinal grooves and the suction rings, as a result of which the sheets are tautened.

It is disadvantageous that special and therefore material-intensive and expensive bearings and couplings have to be provided on the driving drive shaft as a result of the oblique positioning.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide an apparatus for conveying sheets through a printing machine which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which makes it possible to drive a sheet transport belt using simple means, in an oblique position with respect to the conveying direction.

With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for conveying sheets in a printing machine, comprising:

• • a plurality of deflection rollers;
  • at least one belt laid over the deflection rollers and disposed to run in a running direction oblique with respect to a sheet transport direction in the apparatus;
  • wherein at least one of the deflection rollers is a substantially conical deflection roller.

In other words, a belt is laid over at least one deflection roller which is of conical configuration. When two deflection rollers are used, a first driven deflection roller is advantageously of conical and cambered configuration and a second deflection roller lying downstream is of cylindrical and cambered configuration. Here, the rotational axis of the conical deflection roller is exactly perpendicular with respect to the sheet transport direction, while the rotational axis of the second deflection roller assumes an angle which deviates from 90° with respect to the sheet transport direction. If a plurality of belts are provided, the conical deflection rollers can be arranged coaxially on a common drive shaft. Because the rotational axis of the conical deflection rollers and that of the drive shaft do not intersect, the result is simple, standardized bearing designs.

The term “conical” as used herein encompasses shapes of a barrel type. That is, the rolling surface of the corresponding pulley or deflection roller may be crowned so that an axial section would be bounded by convex surfaces. In a preferred embodiment, then, the center deflection roller would resemble a symmetrical barrel, while the lateral deflection rollers would resemble a bottom portion and a top portion of such a barrel, respectively.

In accordance with an added feature of the invention, the deflection rollers include a first deflection roller having a conical configuration and a second deflection roller having a crown-face configuration.

In accordance with an additional feature of the invention, the conical deflection roller has a crown-face running surface.

In accordance with another feature of the invention, the deflection rollers are rotatably supported about respective axes enclosing an acute angle with respect to one another.

In accordance with again another feature of the invention, at least one belt is formed with vacuum openings and laid over the deflection rollers, for conveying the sheets in the printing press, and a vacuum device is operatively associated with the at least one belt.

In accordance with a further feature of the invention, there are provided two or more belts each running over respective deflection rollers, and the belts define running directions diverging symmetrically with respect to the sheet transport direction.

In accordance with again a further feature of the invention, the deflection rollers lying upstream as seen in the sheet transport direction are conical and have mutually aligned axles.

In accordance with a concomitant feature of the invention, a common drive is provided that can be coupled to the conical deflection rollers.

When a plurality of suction belts are used as the sheet brake in the delivery of a sheet-fed printing press, the suction belts are positioned in pairs obliquely with regard to the sheet center, it being possible for a suction belt which lies on the center of the belt to lie in the sheet transport direction. The suction belts which run obliquely outward are each guided on conical deflection rollers. The conical design of the deflection rollers has the effect that a suction belt tracks on the deflection rollers without additional lateral guides. In this arrangement of the suction belts, the sheets are tautened transversely with respect to the sheet paper running direction, with the result that no corrugations are formed on the sheet between the suction belt modules. As a result, the stack formation in the delivery of a sheet-fed printing press is stabilized.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in an apparatus for conveying sheets through a printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevational view of a braking station according to the invention in the delivery of an offset printing press;

FIG. 2 is a schematic perspective view of the braking station according to FIG. 1; and

FIG. 3 is a plan view onto the braking station of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a printing unit 2 which operates according to the offset method and has an impression cylinder 2.1. The latter guides a respective sheet in a processing direction which is indicated by means of the rotational direction arrow 5 through a roller nip between the impression cylinder 2.1 and a blanket cylinder 2.2 which interacts with the impression cylinder 2.1, and transfers it subsequently, in the present example, to a row of grippers of a single revolution transfer drum 2.3. A row of grippers disposed on the impression cylinder 2.1 for gripping the sheet 3 at a gripper edge at the leading end of the sheet 3 are opened during the transfer. Subsequently, the sheet 3 is transferred accordingly from the single revolution transfer drum 2.3 to a further transfer drum 2.4 which is of the half revolution type in the present example and transfers the sheet 3 to a chain conveyor 4 of the delivery 1.

The chain conveyor 4 comprises two endless conveying chains 6, of which each one circulates during operation along a closed chain path in the vicinity of a respective side wall of the chain delivery 1. Each conveying chain 6 wraps around a respective one of two synchronously driven drive sprockets 7 whose axes are aligned with one another, and, in the present example, is guided over a respective deflection sprocket 8 which is situated downstream of the drive sprockets 7 with regard to the processing direction. As a result, each of the conveying chains 6 runs through a closed chain path. Gripper systems 9 which are carried by the two conveying chains 6 extend between the latter and have grippers which pass through gaps between the grippers disposed on the transfer drum 2.4 and in the process receive a respective sheet 3 by gripping with the above-mentioned gripper edge on the leading end of the sheet 3 immediately before the opening of the grippers arranged on the transfer drum 2.4, transport it past a sheet guiding apparatus 10 to a braking station 11 and are opened after the sheet 3 has been transferred to the braking station 11.

In the braking station 11, the sheets are braked to a depositing speed which is reduced with regard to the processing speed and are released finally after reaching the depositing speed, with the result that a respective sheet 3 which is then decelerated finally comes into contact with front edge stops 12 and, while being aligned on the front edge stops 12 and rear edge stops 13 lying opposite them, forms a stack 14 together with preceding and following sheets 3. The stack 14 can be lowered by means of a lifting unit at the same rate as the stack 14 grows. In FIG. 1, only a platform 15 which carries the stack 14 and lifting chains 16 which bear the platform 15 and are illustrated with dash dotted lines are shown of the lifting unit. The conveying chains 6 are guided along their paths between the drive sprockets 7 at one end and the deflection sprockets 8 at the other end by way of chain guiding rails which determine the chain paths of the chain runs.

In the present example, the sheets 3 are transported by the lower chain run in FIG. 1. The section of the chain path which is passed through by the lower chain run is followed by a sheet guiding face 17 which faces that section and is formed on the sheet guiding apparatus 10. A supporting air cushion is preferably formed during operation between the sheet guiding face 17 and the sheet 3 which is respectively guided over it. For this purpose, the sheet guiding apparatus 10 is equipped with compressed or blowing air nozzles which open into the sheet guiding face 17 and of which only one is shown in FIG. 1 as representative of all of them, and in a symbolic illustration in the form of the connection piece 18.

In order to prevent the printed sheets from adhering to one another in the stack 14, a dryer 19 and a dusting apparatus 20 are provided on the path of the sheets 3 from the drive sprockets 7 to the braking station 11. In order to avoid excessive heating of the sheet guiding face 17 by the dryer, a coolant circuit is integrated into the sheet guiding face 10.

The coolant circuit is indicated symbolically in FIG. 1 by an inlet connection piece 21 and an outlet connection piece 22 on a coolant trough 23 which is assigned to the sheet guiding face 17. An illustration of the above-mentioned chain guiding rails is omitted in FIG. 1. The course of the latter in the present example can be seen, however, from that of the chain runs.

The braking station 11 is shown in greater detail in FIG. 2. The braking station 11 comprises five suction belt modules 24.1 to 24.5 in a parallel arrangement with respect to the conveying direction 25 of the sheets 3. The suction belt modules 24 can be positioned individually transversely with respect to the conveying direction 25 on print-free regions of the sheet 3. For this purpose, the suction belt modules 24 are mounted on a guide rod 26 which is fastened in a frame 27.1, 27.2. Stepping motors 28.1 to 28.5 which are coupled to the suction belt modules 24.1 to 24.5 are provided as positioning drives. Pinions 29 are in each case arranged fixedly on the motor shafts of the stepping motors 28 so as to rotate with them, which pinions 29 engage in a chain 30 whose ends are fastened in the frame 27.1, 27.2 and which is aligned parallel to the guide rod 26. The suction belt modules 24 comprise suction belts 31 which are guided over deflection rollers. The suction belts 31 are driven synchronously, in that in each case a deflection roller is coupled to a shaft 32 which is mounted rotatably in the frame 27.1, 27.2. The shaft 32 is coupled to a gear mechanism 33 and a motor 34. Under the suction belts 31 there are suction ducts which are connected to a vacuum source via lines 35. The lines 35 are laid in a hose duct 36 such that they can move. The rear edge stops 13 are fastened to the suction belt modules 24. In order to adapt to different length formats of the sheets 3, the entire braking station 11 described in FIG. 2, including the suction belt modules 24, can be positioned in the conveying direction 25 in the delivery 1.

FIG. 3 shows a plan view of the suction belt modules 24.1 to 24.5. Each suction belt module 24.1 to 24.5 comprises deflection rollers 37.1 to 37.5 which are driven with the shaft 32 and deflection rollers 38.1 to 38.5 which are driven with the suction belts 31.1 to 31.5. The axes of the deflection rollers 37.1 to 37.5 lie coaxially with respect to the axis 39 of the shaft 32. The axis 39 lies perpendicular with respect to the conveying direction of the sheet 3. The deflection rollers 37.3, 38.3 (the central rollers) are cylindrical with a cambered running surface for the suction belt 31.3 or, in other words, they are rotationally and longitudinal-sectionally symmetrical barrel bodies, or crown-face pulleys. The axis 40 of the deflection roller 38.3 lies parallel to the axis 40. The suction belt 31.3 lies on the sheet center 41 and extends parallel to the conveying direction 25. The deflection rollers 37.1, 37.2 and 37.4, 37.5 are of conical configuration with the cone angle γ and with a cambered running surface for the suction belts 31.1, 31.2, and 31.4, 31.5. The radii of the deflection rollers 37.1, 37.2 and 37.4, 37.5 increase in the direction of the sheet center 41. The deflection rollers 38.1, 38.2 and 38.4, 38.5 are of cylindrical configuration with a cambered running surface for the suction belts 31.1, 31.2 and 31.4, 31.5. The deflection rollers 38.1, 38.2 and 38.4, 38.5 are offset outward with respect to the deflection rollers 37.1, 37.2 and 37.4, 37.5 in the perpendicular direction with respect to the conveying direction 25 and are arranged so as to be inclined by an angle α, with the result that the suction belts 31.1, 31.2 and 31.4, 31.5 run obliquely outward symmetrically with respect to the sheet center 41 at an angle β. The sheet 3 is laterally tautened as it is advanced in the conveying direction 25 by the oblique positioning of the suction belts 31.1, 31.2 and 31.4, 31.5, with the result that no corrugations are formed between the suction belt modules 24.1 to 24.4. As a result, the stack 14 can be formed more quickly and exactly.

As a result of the conical configuration of the driving deflection rollers 37.1, 37.2 and 37.4, 37.5, it is not necessary to position their axes obliquely with respect to the axis 39 of the shaft 32. The suction belts 31.1, 31.2 and 31.4, 31.5 with vacuum openings 42 run through the conical circumferential surfaces of the deflection rollers 37.1, 37.2 and 37.4, 37.5 at an angle to the rotational axis 39 of the respective deflection roller 37.1, 37.2 and 37.4, 37.5, without leaving the running surfaces of the deflection rollers 37.1, 37.2 and 37.4, 37.5; 38.1, 38.2 and 38.4, 38.5 in the lateral direction.

This application claims the priority, under 35 U.S.C. § 119, of German patent application No. 10 2004 021 598.7, filed May 3, 2004; the entire disclosure of the prior application is herewith incorporated by reference.

Claims

1. An apparatus for conveying sheets in a printing machine, comprising: a plurality of deflection rollers; at least one belt laid over said deflection rollers and disposed to run in a running direction oblique with respect to a sheet transport direction in the apparatus; wherein at least one of said deflection rollers is a substantially conical deflection roller.

2. The apparatus according to claim 1, wherein said deflection rollers include a first deflection roller having a substantially conical configuration and a second deflection roller having a crown-face configuration.

3. The apparatus according to claim 1, wherein said conical deflection roller has a symmetrical crown-face running surface.

4. The apparatus according to claim 1, wherein said deflection rollers are rotatably supported about respective axes enclosing an acute angle with respect to one another.

5. The apparatus according to claim 1, which comprises at least one belt formed with vacuum openings and laid over said deflection rollers, for conveying the sheets in the printing press, and a vacuum device operatively associated with said at least one belt.

6. The apparatus according to claim 1, wherein said at least one belt is one of at least two belts each running over two said deflection rollers, and said two belts defining running directions diverging symmetrically with respect to the sheet transport direction.

7. The apparatus according to claim 1, wherein said deflection rollers lying upstream as seen in the sheet transport direction are conical and having mutually aligned axles.

8. The apparatus according to claim 1, which comprises a common drive selectively coupled to said conical deflection rollers.