GB2092996A

GB2092996A - Three sensors monitoring correct sheet positioning

Info

Publication number: GB2092996A
Application number: GB8204349A
Authority: GB
Original assignee: ZVS VYZKUMNEVYVOJOVY USTAV KONCERNOVA UCELOVA ORGANIZACE
Current assignee: ZVS VYZKUMNEVYVOJOVY USTAV KONCERNOVA UCELOVA ORGANIZACE
Priority date: 1981-02-16
Filing date: 1982-02-15
Publication date: 1982-08-25
Also published as: GB2092996B; DE3151380A1; JPS57189854A; CS219747B1

Abstract

A sheet position scanning mechanism comprises three scanners (3a, 3b, 3c) mounted with a guide (1) at the end of a sheet transport path. The first scanner (3a) is mounted upstream from the guide (1) at distance between distances (a) and (b) from the guide, distance (a) being from the upstream end of the maximum length of sheet to be withdrawn from the guide at the moment of scanning, distance (b) being a distance equivalent to the shortest sheet length taken from guide (1). The second scanner (3b) is downstream from scanner 3a and is located at a distance closer to the guide than distance (c) from guide (1), distance (c) being the longitudinal separation distance between successive sheets. The third scanner (c) is mounted approximately level with guide (1) and may receive reflected light from an auxiliary guide, see Figure 2. The scanner signals are correlated with a transport engagement signal to check whether the sheets (4) are correctly positioned and ready for withdrawal into an offset printing machine. <IMAGE>

Description

SPECIFICATION Sheet position scanning mechanism The present invention relates to a sheet position scanning mechanism, suitable for scanning, feeding and laying sheets in printing machines with stream feeding.

Devices processing paper, particularly devices processing cut paper, such as offset machines with stream feeding, are equipped for the purpose of securing the correct position of separate sheets in the operating space of the device, with sheet position scanners. These scanners form part of the mechanism for scanning the sheet position, which checks the correct position thereof.

In printing machines with stream feeding, in some cases sheet position scanning can be required at a certain moment, or possibly at an operating phase of the printing machine, at which the levelled sheet is still covered by a part of the sheet to be withdrawn.

For the purpose of scanning the position of the levelled sheet in printing machines with stream feeding, usually scanner systems and scanning mechanisms are used, for scanning the position of the levelled sheet at that time, at which said sheet is not covered by the sheet to be withdrawn.

The disadvantage of this scanning mechanism is that it is impossible to check the position of a sheet covered by the sheet to be withdrawn, or that their signal indicating the sheet position at the moment of scanning is not unambiguously true.

A sheet position scanning mechanism according to the present invention for scanning, feeding and laying streamfed sheets comprises a front guide, a transporting path and at least three sheet position scanners, wherein the transporting path are successively mounted, in the direction of advancement of sheets, sheet position scanners, the distance of the first scanner thereof from the front guide being longer than the distance between the upstream end of the maximum size sheet to be withdrawn from the guide to the guide at the moment of scanning, but shorter than length of the minimum size sheet, the distance of the second scanner from the front guide being shorter than the longitudinal separation of successive streamed sheets, the third scanner being situated substantially level with front guides.

The advantage of the sheet position scanning mechanism according to the present invention is that it is possible to scan the position of sheets also at that moment, or possibly at that phase of operation of the machine, at which the levelled sheet is still covered by the end of the sheet to be withdrawn.

An embodiment of the sheet position scanning mechanism according to the present invention by way of example is shown in the accompanying drawings, in which: Figure lisa diagram of the overall arrangement of the scanning mechanism of the invention, Figure 2 is a side elevation of the third scanner of the mechanism of Figure 1, and Figure 3 is an end elevation of the third scanner of Figures 1 and 2.

The sheet position scanning mechanism according to the present invention, particularly for scanning the feeding and laying of sheets in a printing machine, including a front guide or guides 1, sheet transporting path 2 and at least three scanners 3a, 3b, 3c, has these scanners successively arranged in the transporting path 2 in the direction of advancement of sheets 4. The scanners 3a, 3b, 3c can be of a known kind, that is a capacitance or optical scanner, and are arranged in the transporting path 2 in such manner, that the distance of the first scanner 3a from the front guide(s) 1 is longer than the distance a between the end of the maximum size sheet 4' to be withdrawn and the front guide(s) 1 at the moment of scanning and evaluating the position of sheet 4.

However distance a is shorter than length b of the minimum size of sheet 4 used. The distance of the second sheet position scanner 3b from the front guide(s) 1 is shorter than the separation distance c of neighbouring sheets 4 in the stream. The third sheet position scanner 3c is approximately level with the front guide(s) 1.

It is advantageous, when at least the third sheet position scanner 3c is of the optical type - see Figures 2 and 3 - that there is provided a reflecting surface 5 for reflecting a light beam 8 which is emitted from a not represented light souce, and this reflecting surface 5 is mounted on an auxiliary guide 6. The auxiliary guide 6 is mounted on a common mounting means 7 for the front guide(s) 1. Suitably the mounting means is a rod.

For the purpose of simplification of the mechanism, it is advantageous to mount the reflecting surface 5 directly on the front guide(s) 1, thus eliminating the necessity of using auxiliary guide 6.

In certain cases, it is also advantageous to provide auxiliary guide 6, or possibly front guide(s) 1, with an opening 9, and to arrange the reflecting surface 5 on the upper surface, of the opening as is shown, or possibly at the bottom of the opening 9.

A true signal about feeding sheet 4 is obtained by the conjunction of the signals from both the first and the second scanner 3a, 3b, and the signal of engaging the transport of sheets 4. When x1 denotes the signal from the first scanner 3a, x2 the signal from the second scanner 3b, XTR the signal of engagement of the transport of sheets 4, and yp the resulting signal, then the connection between scanners 3a, 3b operates according to the relationship Vp Xs . X2 . XTRv This connection between scanners 3a, 3b gives a true signal about the feeding of sheets 4 at any possible combination thereof.

When at the moment of scanning and checking, sheet 4 is not present on the transport path 2, then no sheet 4 is above the first scanner 3a; . the end of sheet 4' to be withdrawn is above the second scanner 3b, and the transport of sheets 4 is engaged.

In that case Vp 0, since yp= 0.1.1 = 0.

When a stream of sheets 4 is on the transporting path 2, transporting is engaged, however, the stream does not advance yet. The, Vp 0, since yp = 1.0.1.

When the end of the last sheet 4 of the stream passes above scanners 3a, 3b, and no further sheets 4 of the stream arrive, although transporting is engaged, yp = 0 again, since yp = 0.1.1 = 0.

The third scanner 3c, mounted at level with guides 1, emits a true signal about laying sheet 4, as the sheet 4' to be withdrawn in separated from the scanned sheet 4 by front guide(s) 1, or possibly auxiliary guide 6.

Figure 1 represents the mechanism according to the present invention, in which the stream of sheets 4 is shown at the moment of scanning, i.e. checking.

The sheet 4' to be withdrawn is withdrawn and if the following, i.e. the levelled sheet 4 should be missing, the second scanner 3b issues a signal denoting the presence of the sheet, as by this scanner the sheet 4' to be withdrawn is scanned. However, the first scanner 3a issues the "0" signal, and thus the indication yp= 0 on feeding is true, since the following sheet 4 is not yet present above the first scanner 3a.

An embodiment of the third scanner 3c by way of example, i.e. the scanner for laying sheet 4, is represented in Figures 2, 3.

The actual third scanner3c passes through opening 9 in the auxiliary guide 6, which is mounted on the common mounting means 7 of front guide(s) 1, the mounting means being in this case a rod. The upper surface of opening 9 is provided with reflecting surface 5. The light beam 8 is emitted onto the third scanner 3c at a point, at which the edge of sheet 4 cannot arrive, and is directed in such manner, then incidence belowthe levelled sheet 4 is prevented.

The light beam 8 is reflected by reflecting surface 5 to a point, at which it is unambiguously interrupted by the correctly levelled sheet 4.

Claims

1. Asheetposition scanning mechanism, for scanning, feeding and laying streamfed sheets comprising a front guide, a transporting path and at least three sheet position scanners, wherein along the transporting path are successively mounted, in the direction of advancement of sheets, the sheet position scanners, the distance of the first scanner thereof from the front guide being longer than the distance between the upstream end of the maximum size sheet to be withdrawn from the guide to the guide at the moment of scanning, but shorter than length of the minimum size sheet, the distance of the second scanner from the front guide being shorter than the longitudinal separation of successive streamed sheets, the third scanner being situated substantially level with front guides.

2. A mechanism as claimed in Claim 1, wherein at least the third scanner is an optical scanner and includes a reflecting surface mounted on an auxiliary guide, which in turn is mounted on a common guide mounting means.

3. A mechanism as claimed in Claim 2, wherein the reflecting surface is mounted on the guide.

4. A sheet position scanning mechanism sub stantially as decribed with reference to the accompanying drawings.