GB2137141A

GB2137141A - Blanket Cylinder for Web Printing Presses

Info

Publication number: GB2137141A
Application number: GB08333526A
Authority: GB
Inventors: Peter Gertsch; Andreas Miescher
Original assignee: Wifag Maschinenfabrik AG
Current assignee: Wifag Maschinenfabrik AG
Priority date: 1983-01-21
Filing date: 1983-12-16
Publication date: 1984-10-03
Also published as: GB8333526D0; SE8300325D0; FR2539673A1; DE3346217C2; DE3346217A1; GB2137141B; SE455848B; CH662782A5; SE8300325L; FR2539673B1

Abstract

On a blanket cylinder 1 equipped with a flexible section 10 adjacent the tensioning gap 2, a rigid supporting element 11 is positioned in front of the flexible section 10 on the tensioning gap side in order to redirect the blanket tensioning force. This prevents the resilience of the section 10 being taken up merely by the tensioning of the blanket. <IMAGE>

Description

SPECIFICATION Blanket Cylinder for Web Printing Presses The invention concerns a web printing press blanket cylinder with a so-called tensioning gap for receiving blanket tensioning means. The circumference of the blanket cylinder is provided, at least in the vicinity of the leading edge of the tensioning gap, with a section capable of strictly limited deflection.

It is a known fact that, when the blanket cylinder operates in conjunction with a backpressure cylinder, so-called gap shocks are caused by the sudden relief and reapplication of the pressing force each time the tensioning gap passes the backpressure cylinder. These gap shocks can cause cylinder vibrations that have a noticeably adverse effect on the printed product.

A method suitable for the reduction of gap shock to an acceptable level on a sheet-fed rotary press has been disclosed in German OffenlegungsschriftDE-A1-16 36312.

The space available for the tensioning gap is so limited in web printing presses that the blanket tensioning means cannot operate in an approximately tangential manner as is the case in sheet-fed rotary presses. Instead, they have to be arranged to operate in a manner that is virtually radial. The ends of a blanket are usually introduced into the tensioning gap under an acute angle so that the necessary tensioning force would already cause complete deformation of the flexible section in the previously disclosed configuration, thus eliminating the desired flexibility effect.

The present invention is based on the provision of means for supporting the bend in the blanket in such a manner that the blanket tension forces have substantially no effect on the flexible section in the blanket cylinder.

In the present invention, the problem is solved by the provision of a rigid supporting element between the gap and the flexible section to redirect the tension forces in the blanket.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary sectional view of a blanket cylinder with a first supporting element configuration; Figure 2 is a greatly enlarged fragmentary sectional view of the edge of the tensioning gap shown in Figure 1; and Figure 3 is a similar sectional view of a second supporting element configuration.

Referring to Figure 1, a blanket cylinder 1 is provided with a tensioning gap 2 in which one of a large number of known blanket tensioning means 3 is installed. The leading gap edge section 4 is formed by a supporting element carrier 7 with a limit stop surface 6 and an insert 8, located in a recess 5 machined in the blanket cylinder 1. The insert 8 is fixed to the carrier 7 and to the cylinder 1 and precisely corresponds to the circumference geomery of the cylinder 1. A slot 9 is provided in the insert 8 to form a resiliently flexible section 10.

The carrier 7 is provided with a rigid supporting element 11 set back from the circumference geometry of the cylinder 1 and located in front of the flexible section 10 to redirect the blanket tensioning force, as well as with the limit stop surface 6 which strictly limits the deflection of the flexible section 10 to an amount that will still permit the transfer of a printed impression.

If technically feasible, the insert 8 can be dispensed with and the slot 9 directly machined into the blanket cylinder 1 to form an integral flexible section 10, the supporting element carrier 7 being retained in a suitably modified configuration. Referring to Figure 3, it is also feasible to dispense with the supporting element 7 and to attach a rigid supporting element 12 as an independent component directly to the blanket cylinder 1 in such a manner that the free end of the element 12 contacts the longitudinal edge of the flexible section 10, the limit stop surface 6 being formed by a strip 13 or similar means inserted in the slot 9.

1. A blanket cylinder for a web printing press, having a tensioning gap for receiving blanket tensioning means, the circumference of said blanket cylinder adjacent the tensioning gap being provided, at least in the vicinity of the leading edge thereof, with a flexible section capable of strictly limited deflection, a rigid supporting element being arranged in front of the flexible section on the tensioning gap side in order to redirect the force in the tensioned blanket.

2. A blanket cylinder as claimed in claim 1, in which the supporting element is part of a supporting element carrier.

3. A blanket cylinder as claimed in claim 1, in which the supporting element is an independent component fastened to a supporting element carrier.

4. A blanket cylinder as claimed in claim 1, in which the supporting element is fastened to the blanket cylinder and is supported tangentially by the flexible section.

5. A blanket cylinder substantially as described with reference to, and as shown in, Figures 1 and 2 or Figure 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Blanket Cylinder for Web Printing Presses The invention concerns a web printing press blanket cylinder with a so-called tensioning gap for receiving blanket tensioning means. The circumference of the blanket cylinder is provided, at least in the vicinity of the leading edge of the tensioning gap, with a section capable of strictly limited deflection. It is a known fact that, when the blanket cylinder operates in conjunction with a backpressure cylinder, so-called gap shocks are caused by the sudden relief and reapplication of the pressing force each time the tensioning gap passes the backpressure cylinder. These gap shocks can cause cylinder vibrations that have a noticeably adverse effect on the printed product. A method suitable for the reduction of gap shock to an acceptable level on a sheet-fed rotary press has been disclosed in German OffenlegungsschriftDE-A1-16 36312. The space available for the tensioning gap is so limited in web printing presses that the blanket tensioning means cannot operate in an approximately tangential manner as is the case in sheet-fed rotary presses. Instead, they have to be arranged to operate in a manner that is virtually radial. The ends of a blanket are usually introduced into the tensioning gap under an acute angle so that the necessary tensioning force would already cause complete deformation of the flexible section in the previously disclosed configuration, thus eliminating the desired flexibility effect. The present invention is based on the provision of means for supporting the bend in the blanket in such a manner that the blanket tension forces have substantially no effect on the flexible section in the blanket cylinder. In the present invention, the problem is solved by the provision of a rigid supporting element between the gap and the flexible section to redirect the tension forces in the blanket. The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary sectional view of a blanket cylinder with a first supporting element configuration; Figure 2 is a greatly enlarged fragmentary sectional view of the edge of the tensioning gap shown in Figure 1; and Figure 3 is a similar sectional view of a second supporting element configuration. Referring to Figure 1, a blanket cylinder 1 is provided with a tensioning gap 2 in which one of a large number of known blanket tensioning means 3 is installed. The leading gap edge section 4 is formed by a supporting element carrier 7 with a limit stop surface 6 and an insert 8, located in a recess 5 machined in the blanket cylinder 1. The insert 8 is fixed to the carrier 7 and to the cylinder 1 and precisely corresponds to the circumference geomery of the cylinder 1. A slot 9 is provided in the insert 8 to form a resiliently flexible section 10. The carrier 7 is provided with a rigid supporting element 11 set back from the circumference geometry of the cylinder 1 and located in front of the flexible section 10 to redirect the blanket tensioning force, as well as with the limit stop surface 6 which strictly limits the deflection of the flexible section 10 to an amount that will still permit the transfer of a printed impression. If technically feasible, the insert 8 can be dispensed with and the slot 9 directly machined into the blanket cylinder 1 to form an integral flexible section 10, the supporting element carrier 7 being retained in a suitably modified configuration. Referring to Figure 3, it is also feasible to dispense with the supporting element 7 and to attach a rigid supporting element 12 as an independent component directly to the blanket cylinder 1 in such a manner that the free end of the element 12 contacts the longitudinal edge of the flexible section 10, the limit stop surface 6 being formed by a strip 13 or similar means inserted in the slot 9. CLAIMS