Patent GB-885098-A (GB)
Title: Improvements in or relating to a pile lifting device for pneumatic sheet feeders
IPC: B65H1/30
Filed: 1958-04-30
Abstract: 885,098. Feeding sheets. MABEG MASCHINENBAU G.m.b.H. April 30, 1958 [Sept. 6, 1957], No. 13739/58. Class 100(1) Pile tables. A pile lifting device for a pneumatic sheet feeder which separates sheets from the top of a pile without interruption during pile replenishment, has two separate motor-operated means for lifting a main table and an auxiliary table, and in one form the main table is raised step-by-step under the control of a pile height feeler through pawl and ratchet means, and the auxiliary table is raised stepwise by a motor supplied with current through an adjustable time constant circuit which is re-charged during each sheet feeding cycle, and in another form each table is raised stepwise by a motor controlled through the same adjustable time constant circuit. The time constant circuit may comprise a condenser which is arranged to be discharged, when pile lift is required, through a relay in series with an adjustable resistance. In the first form, when a new pile 17 is first introduced, it is placed on a main table 16 which is raised by a main motor 3 and chains 13 until the top of the pile meets a limit switch 28, 29, whereupon the motor is cut out, and the pile is raised step-by-step by a pawl 4, driven from an independent source, acting on a ratchet-wheel 6. The pawl 4 is controlled by a lever 5 coupled by a Bowden wire 50 to a reciprocating pile feeler 47. When the pile is so depleted that the main pile table 16 has been raised above the level of the starting position of an auxiliary table 41 and its supports 39, 40, the table 41 is inserted by hand between the base of the residual pile (denoted 42) and the main table 16. A switch 38 is now depressed manually to close the circuit of a high-speed winding 44 of the auxiliary motor 43 which raises the supports 39, 40 through chains 24 and a chain drive 62, 63. The support 39 incorporates a safety rail device 52-55, described in Specification 885,099 which stops the motor 43 when the rising supports 39, 40 take the weight of the depleted pile 42. A lever 30 is operated to raise the pawl 4, and a switch 46 is moved to bring into circuit a low-speed winding 45 of the motor 43. The pile feeler 47 now controls the motor 43, as described below, to raise the pile step-by-step. The main table 16 is lowered by the motor 3 on depression of a switch 37, and the table is raised with the new pile 17 on operating the switch 38. The current to the low-speed winding of the motor 43 to raise the residual pile stepwise is controlled by the time constant circuit, Fig. 7, which is connected by joint operation of the lever 30 and switch 46, and subsequently by switches 51, 66 operated by the feeler 47. As shown, the current path exists from phase wire W via 46, 35, 66, a rectifier 69, and an adjustable resistance 90 to a condenser 65, and from there to the neutral lead X via the connection x. When the feeler 47 falls below a predetermined level, it closes switch 51 and opens switch 66, so that the condenser 65 is discharged through a relay 67 and resistance 90. Operation of the relay 67 closes the contacts 68 and establishes a current path through a limit switch 27a to contactor IIIa, which then switches in the low-speed winding 45 of motor 43. When the condenser 65 is discharged to the extent that the current through relay 67 cannot retain contacts 68 closed, the contactor IIIa falls off and the motor stops. The duration of power supply to the motor winding 45 is thus dependent on the time constant of the condenser discharge circuit, which may be altered by the adjustment of the resistance 90. The resistance 90 may be wired in the position 90<SP>1</SP>. In a modified arrangement (Fig. 6, not shown) the adjustable time constant circuit arrangement is used, not only for the step-by-step raising of the residual pile, but also for the stepby-step raising of the main pile. In this case, the main motor is similar to the auxiliary motor 43 and has high and low speed windings, and the ratchet wheel 6 and its associated components are eliminated. An additional switch is used to place the relay contacts 68 alternatively in the low-speed circuit of the main or of the auxiliary motor.