GB1094863A - Detecting devices for sheet printing presses - Google Patents

Abstract

1,094,863. Feeding sheets. ROLAND OFFSETMASCHINENFABRIK FABER & SCHLEICHER A.G. March 18, 1965 [April 23, 1964], No. 11457/65. Heading B6B. In apparatus in which a conveyer 4 feeds an overlapping stream of sheets 1 to front stops 6 and then to a printing press, devices are provided to stop or otherwise control the press if sheets become doubled up, or are absent, such devices comprising two detectors detecting the thickness of sheets passing them, the detectors being spaced along the direction of sheet travel a distance A equal to the spacing of the trailing edges of adjacent sheets or a multiple thereof, and producing an electric signal to control the press if the thickness detected by each detector is not the same. Each detector may comprise a pair of coacting rollers or the two plates of a capacitor. Further, the second detector along the line of sheet travel may comprise two pairs of coating rollers. In one embodiment, Fig. 1, the detectors comprise respectively a fixed axis roller 8, 14 and a coacting roller 9, 15 mounted on a spring-urged bell-crank lever 10, 16. To the arm 10b of lever 10 is connected a link 18 slotted at 19 to engage a pin on the arm 16a of lever 16. Mounted on the link 18 are two adjustable switches 21, 22 between which is situated an extension 20 of arm 16a. If the same thickness of sheets is passing through both detectors, the extension 20 does not contact either switch 21, 22. Should a doubled-up sheet pass under roller 9, the link 18 is moved leftwards relatively to the arm 16a and switch 22 is operated to close the circuit of a solenoid (104, Fig. 5) operating the machine control. If a sheet is absent at the roller 9, the link 18 moves rightward to operate the switch 21 and the solenoid (104). The roller 9 is intermittently raised, by a cam 11 acting on an arm 10a attached to lever 10, to allow a free run-in of the leading edges of the sheets, and during this operation the arm 10a operates a switch 23 to open the circuit of the solenoid 104 and thus prevent actuation of the machine control. If capacitors (110, 108 and 109, 11, Fig. 13) are used as detectors, they are connected on a bridge circuit (Fig. 14), unbalance of which, due to different thicknesses of sheets passing through the detectors, causing operation of a machinecontrol solenoid (119). In another construction (Fig. 15), the movable roller (121) of each pair of rollers constituting a detector is connected to a conical core (123) of a coil (122). The coils are connected in a bridge circuit similar to that employed for capacitor detectors and which operates in a similar manner. Due to the shape of the core (123), a greater variation in the signals supplied by the coils is necessary to cause unbalance in the bridge when thicker gauge sheets are being fed than when thin sheets are being fed. As shown in Fig. 6, the second detector comprises two pairs of rollers 25, 26 and 27, 28, the distance A from the midpoint between the pairs to the first detector 8, 9 being equal to the spacing of the trailing edges of the sheets. The rollers 9, 28, 26 are carried by spring-urged levers 29, 34, 33 respectively. A beam 31 is carried by the lever 29 and a pivoted link 32, and has mounted thereon switches 38, 39, 38a, 39a which can be closed by adjustable projections 36, 37, 36a, 37a on the levers 33, 34. The switches are in a circuit (Fig. 9), such that closing of both switches 38, 38a or 39, 39a is necessary to actuate the machine control solenoid, thus preventing a false signal being generated if an inaccurately cut sheet passes the detector. The projections 36 ... 37a are adjusted according to the gauge of the sheets being fed. A cam 11 and switch 23a corresponding to cam 11 and switch 23, Fig. 1, are also provided. In a further construction (Figs. 10 to 12), operating in a similar manner to that shown in Fig. 6, the three movable rollers (43) (first detector), (44 and 46) (second detector) are carried by levers (48, 49, 50) respectively, these levers having coacting projections (55 ... 58) and switches (51 ... 54) which cause actuation of the machine control solenoid as described in connection with Fig. 6. All the rollers are lifted together intermittently, to allow a free run-in of the sheets, by rods (67, 68) with rollers (69, 70) engaging beneath the levers (48 ... 50) and raised by a cam (62). The apparatus operates so that a greater thickness difference has to be sensed by the two detectors to produce a press-controlling signal when thick sheets are being fed than when thin sheets are used.