GB717047A - Improvements in devices for detecting faulty feed of sheets to machines - Google Patents

Abstract

717,047. Feeding sheets. FABER & SCHLEICHER AKT.-GES. Oct. 25, 1951 [Oct. 26, 1950], No. 24948/51. Class 100 (1). [Also in Group XL (b)] Faulty feed control devices.-A device detecting absence or faulty positioning of a sheet in, for example, a printing-machine fed with sheets underlapping each other in a continuous succession comprises two or more detector members one positioned below the sheet and the other moved in timed relation to the feed of sheets from a position below the plane of the sheet to a position above it and in line with the other detector member. Fig. 1 shows an arrangement in which the underneath detector member is in the form of an electrical contact 7 located in a bore in the feed table. The other detector member 6 is carried on a lever 5 mounted on a rocker 3 rotatable on a shaft 1. The detector member 6 is moved towards member 7 for the detecting operation by a push rod 9 displaced against the action of a spring 10 by a lever 8. In the rest position (shown dotted) the rocker 3 is below the plane of the sheet and swings upwardly to the detecting position in timed relation to the sheet feed so that if a sheet is fed too far forward, and lies over the front stops when these move into position. it is lifted by the rocker and the aligned detector members will respond to the absence of a sheet therebetween to trip the printing-machine. After tripping, a plate 12 moves under the push rod 9 to maintain the contacts 6, 7 closed. To detect a smaller movement of the forward edge of the sheet beyond its correct position, detectors as used in Fig. 2 may be used. In this arrangement a second pair of contacts 13, 14 are provided. If the sheet passes between these contacts the printing-machine is tripped. The contacts 13, 14 may be replaced as shown in Fig. 4 by a rocking lever 17 having a sensing pin 16 at one end and at the other a contact 18 co-operating with a fixed contact 19. In the detecting operation the pin 16 enters an opening 15 in the feed tab'e when the sheet is correctly positioned. If the sheet has moved too far and covers the hole the contacts are moved together and cause tripping of the printing machine. In the form of Fig. 6 one of the detector members is a lamp 20 and the other a light-sensitive cell 21, the beam of light shining through a hole in the feed table but being interrupted by the sheet when correctly positioned. In a modification both the lamp and cell are mounted below the feed table and a mirror is moved into such a position above the table that the light can pass from the lamp to the mirror and be reflected to the cell, suitable holes being provided in the table. A. correctly fed sheet will interrupt the light and prevent energization of the cell.