Claims
- 1. In a rotary printing press having an assembly of at least two printing units and a sheet transfer cylinder located between the printing units and having a plurality of gripper rows arranged symmetrically at the circumference of the cylinder, the sheet transfer cylinder comprising means for defining closed and continuous guide surfaces disposed between the gripper rows within the circumference of the cylinder and extending at least approximately as secants to the circumference of the cylinder across the width of the cylinder, said guide surfaces being disposed so as to support a trailing edge of a stiff sheet and so as to define therewith a wedgeshaped hollow space forming an air pocket after take-over of the sheet by an impression cylinder following the sheet transfer cylinder.
- 2. Assembly according to claim 1, including a blow tube located outside the sheet transfer cylinder for directing an air flow towards the sheet, said guide surfaces and into said hollow space.
- 3. Assembly according to claim 1, wherein said guide surfaces comprise air paddles for applying the sheet at an unprinted face thereof to a sheet guiding device disposed outside the sheet transfer cylinder at a slight spacing from an outer cylindrical surface of the cylinder.
- 4. Assembly according to claim 1, wherein said guide surface are on guide plates adjustably fastened by screws to a support body of the sheet transfer cylinder.
- 5. Assembly according to claim 1, wherein said guide surface are on guide plates formed with air slits having openings adjustable for controlling pressure of the air pocket.
- 6. Assembly according to claim 1, wherein sheet-supporting elements forming the circumference of the cylinder are hangingly fastened between the gripper rows and are mounted on supports by snap closures.
- 7. In a rotary printing press having an assembly of at least two printing units and a sheet transfer cylinder located between the printing units and having a plurality of gripper rows arranged symmetrically at the circumference of the cylinder, the sheet transfer cylinder comprising a cylinder body formed with closed and continuous guide surfaces disposed between the gripper rows within the circumference of the cylinder and extending at least approximately as secants to the circumference of the cylinder across the width of the cylinder, said guide surfaces being formed with a bend towards the middle of the cylinder and being disposed so as to support a trailing edge of a stiff sheet and to define therewith a wedge-shaped space forming an air pocket after take-over of the sheet by an impression cylinder following the sheet transfer cylinder.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 3602084 |
Jan 1986 |
DEX |
|
Parent Case Info
The invention relates to an assembly of a sheet transfer cylinder between printing units of a rotary printing machine, the sheet transfer cylinder having a plurality of gripper rows arranged symmetrically at the circumference of the cylinder.
The cylindrical casing of such a sheet transfer cylinder is either formed of closed plate-shaped segment elements which are provided between the gripper rows or of web-shaped segment elements which also have the purpose of carrying and conveying the rather nonstiff i.e. soft, sheet (German Pat. No. 34 47 596 6-27). If print is applied to stiffer material in such a sheet-fed printing machine, a possibility of providing the sheet transfer cylinder with a greater diameter arises so that e.g. three sheet carrying surfaces with gripper rows are provided. This measure does not suffice, however, when printing stiff cardboard, because the end of the cardboard sheet extends away stiffly from the surface of the cylinder casing so that there is a risk of the printed image being smeared, especially when the cardboard sheet is being transferred from a sheet transfer cylinder to an impression cylinder. Presuming that such stiff sheets receive top quality printing, as is required, for example, for producing packaging, a damaged printed sheet is not acceptable.
Proceeding from the foregoing, it is an object of the invention to provide a sheet transfer cylinder which permits smear-free and mackling-free processing of a range of regular paper thicknesses up to thick cardboard.
With the foregoing and other objects in view, there is provided, in accordance with the invention, in a rotary printing press having an assembly of at least two printing units and a sheet transfer cylinder located between the printing units and having a plurality of gripper rows arranged symmetrically at the circumference of the cylinder, a sheet transfer cylinder comprising means for defining guide surfaces disposed between the gripper rows within the circumference of the cylinder and extending at least approximately as secants to the circumference of the cylinder.
Due to the use of guide surfaces provided between the gripper rows in the cylinder body, a free space is formed in which the trailing end of a stiff sheet can relax without damage to the printed sheet side. The trailing edge of the sheet is thereby purposefully passed along the guide plates after its transfer to the next cylinder. Thus, the construction of the sheet transfer cylinder according to the invention also permits the printing of stiff cardboard sheets without running the risk of damaging the printed image.
In accordance with another feature of the invention, the means for defining the guide surfaces are guide plates bent radially inwardly towards the center of the cylinder, the bent guide plates being disposed so as to support a trailing edge of a stiff sheet after take-over of the sheet by an impression cylinder following the sheet transfer cylinder, the bent guide plates forming with the trailing edge portion a wedge-shaped hollow space for producing an air pocket therein.
In accordance with an added feature of the invention, the means for defining the guide surfaces are part of a cylinder body of the sheet transfer cylinder, the guide surfaces being bent radially inwardly towards the center of the cylinder, the guide surfaces being disposed so as to support a trailing edge of a stiff sheet after take-over of the sheet by an impression cylinder following the sheet transfer cylinder, the guide surfaces forming together with the trailing edge portion a wedge-shaped hollow space for producing an air pocket therein.
In accordance with a further feature of the invention, there is provided a blow tube located outside the sheet transfer cylinder for directing an air flow towards the sheet, the guide surfaces and into the hollow space.
In accordance with an additional feature of the invention, the means for defining the guide surfaces comprise air paddles for applying the sheet to a sheet guiding device disposed outside the sheet transfer cylinder at a slight spacing from an outer cylindrical surface of the cylinder.
In accordance with still another feature of the invention, the guide plates are adjustably fastened by screws to a support body of the sheet transfer cylinder.
In accordance with still an added feature of the invention, the guide plates are formed with air slits having openings adjustable for controlling pressure of the air pocket.
In accordance with still a further feature of the invention, the guide plates are formed as guide stirrups
In accordance with still an additional feature of the invention, the guide plates are formed as guide tongues
In accordance with a concomitant feature of the invention, sheet-supporting elements forming the circumference of the cylinder are hangingly fastened between the gripper rows and are mounted on supports by snap closures.
Handling and operation of the assembly according to the invention is simplified and transport or conveyance of the sheets, is improved. The guide plates thus act as air paddles or vanes which, in combination with the air accumulated in the wedge-like hollow space, keep the printed sheet side away from the guide plates.
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 a sheet transfer cylinder between printing units of a rotary 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.
US Referenced Citations (9)
Foreign Referenced Citations (4)
| Number |
Date |
Country |
| 724129 |
Aug 1942 |
DE2 |
| 1174801 |
Jul 1964 |
DEX |
| 961106 |
Nov 1949 |
FRX |
| 527397 |
Oct 1940 |
GBX |
Patent Grant
4815379
