GB2049993A - Printing machines - Google Patents

Abstract

A device for controlling a printing machine, in which the machine has a drive motor and a sheet feed system, has a first read-only memory (11) which is arranged to be controlled upon conditions or states at its inputs in such a manner that control switches (2-6) of the device are illuminated either by a continuous light or a flashing light in dependence upon the operation or readiness of the machine. A feature of the invention is to provide a further read-only memory (10) which is arranged to control machine functions in dependence upon conditions or states at the inputs of the read-only memory to thereby generate signals to control the first read-only memory (11). <IMAGE>

Description

SPECIFICATION Printing machines This invention relates to a printing machine and in particular to a device for controlling such machines.

Printing machines, for example offset printing machines, are known which are operated by a control desk having separate operating elements.

Such a control desk is provided, for example, with an ON button for switching on the machine, an OFF button for switching off the machine, a sheet FEED button for starting the sheet feed and a sheet STOP button for stopping the sheet feed.

However, with such an arrangement it is possible for an operator, who is not specially trained, to make mistakes by wrongly operating individual buttons.

It is an object of this invention, to provide a device for controlling a printing machine, to mitigate operator error in operating individual elements arranged on the control desk.

According to this invention there is provided a.

device for controlling a printing machine having a drive motor and a sheet feed system, the device comprising at least one read-only memory, operating elements for controlling the drive motor and sheet feed system, and each operating element being associated in an illuminating element, wherein the illuinating elements are arranged to be controlled by the read-only memory in accordance with predetermined conditions or states at its inputs in such a manner that an operating element illuminated by its associated illuminating element in a first manner indicates its operational readiness and that the operating element illuminated by its associated illuminating element in a second manner indicates a further state of its operational readiness.

The device is advantageously constructed in such a manner that a continuously illuminated operating element indicates its functional readiness whereas a flashing operating element always indicates an error source.

A further essential advantage of the invention consists in that the present invention enables an operator to recognize and to eliminate any faults by himself thereby eliminating costly service.

Any more complicated fault can advantageously be eliminated even if the operator is not able to do this himself. Such a fault is then eliminated in such a manner that, for example, a service station which has previously been told by telephone which of the operating elements are illuminated in which way and which operating elements are not illuminated, provides the operator with an instruction or information which makes it possible for the operator to eliminate the fault. This can also eliminate costly service.

The invention makes it possible to increase safety during the operation of a printing machine advantageously in that it is possible to operate a handwheel only at a particular speed which is arranged to be not too high.

The present invention can advantageously be adapted quite easily to different printing machines and used in conjunction with different printing machines, due to the use of programmed read only memories (PROM's).

A further advantage of the invention results from the long service life of the electronic components used. The failure rate of components can be considerably reduced, in comparison with conventional control systems.

The invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 shows a control desk of a printing machine with individual operating elements, and Figure 2 shows a circuit diagram of an embodiment of the control device in accordance with this invention.

In connection with the present invention, socalled PROM's (Programmable Read-Only Memories) are used. These are read-only memories which are programmed or programmable by the manufacturer and which can only be read. For example, a single PROM (for example, type SN 74S287) contains 1024 memory locations. Such a component can be programmed without difficulty, individually, for each case in accordance with the user's specification, or, as in the present case, that of the manufacturer of the printing machine, in such a manner that it generates a predetermined combination of predetermined output signals in response to certain input signals present at its inputs.

In this invention, read-only memories of the type described above, are used, on the one hand, in order to execute machine functions in accordance with certain predetermined conditions or states and, on the other hand, in order to illuminate the operating elements in a very special way for the purpose of facilitating machine operation and of indicating faults. In this arrangement, continuously illuminated operating elements indicate their operational readiness.

Operating elements which are illuminated in a flashing manner always indicate certain error sources.

Figure 1 shows the control desk 1 of a printing machine, and particularly that of an offset printing machine. This control desk contains the operating elements or buttons 2 to 6, the functions of which are to be explained in detail hereafter. The operating element 2, which is preferably constructed as a variable resistor, can be used to preselect the speed of the machine and the variable resistor 2 can be used to vary the speed of the machine continuously within a range of 3000 to 7000 revolutions per hour. A certain desired speed can also be preselected while the machine is standing still. For this purpose the variable resistor 2 is provided, for example, with a dial which is calibrated in a suitable manner. The machine is switched on by operating the ON button 4 and then runs up to the speed preselected by means of the variable resistor.

After this preselected speed has been reached, the machine remains at this speed until the run of the machine is interrupted, for example by operating the OFF button 3.

Operating the sheet FEED button 5 starts the sheet feed. This means that the machine is fed successively with individual sheets of paper for printing. If the sheet STOP button 6 is operated the sheet feed is stopped or interrupted.

The OFF button 3, the ON button 4, the sheet FEED button 5 and the sheet STOP button 6 are buttons which can be illuminated electrically. They are preferably illuminated by means of an incandescent lamp arranged in each case behind the translucent surface of the buttons 3 to 6. The ON button 4 may have a green surface and the OFF button 3 a red surface. The sheet FEED button 5 and the sheet STOP button 6 are preferably white. On the surfaces of the buttons 3 to 6 individual symbols may be arranged which indicate the respective function of the button.

In addition to the buttons 2-6, an adjustable run counter 7 can be arranged on the control desk 1. The individual digits of this counter can be set by hand. After each printing operation the counter value is incremented by the value of 1. The control desk 1 may be provided with further buttons such as for example, a switch button for run preselection or a switch button for a sheet counter.

Figure 2 shows the electric circuit provided for control purposes. This circuit contains a first readonly memory 10 and a second read-only memory 11 which generate certain output signals in response to input signals which are present at their inputs in predetermined combinations. In this arrangement the first read-only memory 10 preferably generates output signals for controlling machine functions. The second read-only memory 11 preferably generates output signals which are used to illuminate the individual buttons of the control desk in a continuous or interrupted manner. Details features of Figure 2 which have already been explained in conjunction with Figure 1, are provided with corresponding reference designations.

In order to decouple the electronic circuits serving the read-only memories from the input and output circuits, so-called optical couplers 12 to 1 6 are provided. Each input of an optical coupler is associated with a light-emitting diode 8 which is excited in response to a signal at its input and then switches a photo-transistor 9 into a conducting state. This transistor then generates an output signal at the output of the optical coupler.

The operative steps will now be described, for the purpose of which it is assumed that before the machine is switched on, the initial conditions have first been fulfilled correctly. This means, for example, that the covers are properly closed to generate a signal and that the 'TIP' signal is present at input 83. These two signals will be explained later in detail. The lamp 80 associated with the ON button 4 will then be illuminated. This lamp is connected between a voltage of +30 V and the output 1 7 of an output amplifier 1 8. The input 1 9, associated with the output 17, of the output amplifier 1 8 is connected to the output 20 of the read-only memory 11. The read-only memory 11 provides an output signal at its output 20 if there are no signals at its inputs.

Switching On The illuminated button 4 can now be operated to switch on the machine. When the ON button 4 is operated a potential of +30 V is applied to the input 21 of the optical coupler 12. The result of this is that the diode associated with this input 21 is placed between earth potential and +30 V and is thus excited. This switches the photo-transistor connected to the output 22 of the optical coupler 12-.into'a conducting state and applies an input signal 'START' to the input 88 of the read-only memory 10. In response to this 'START' signal at its input 88 the read-only memory 10 generates a 'VOR' signal at its output 210 if there is no 'STOP' signal at the input 87, no 'COSTA' signal at the input 86, no 'SAFE' signal at the input 45, no 'TIVOR' or 'TIRUCK' signal at the inputs 84 and 85 and the 'TIP' signal is at the input 83.The abovementioned signals which are present or not present at the inputs 45, 83, 84, 85, 86, 87, of the read-only memory 10, are explained later in detail.

The 'VOR' signal present at the output 210 of the read-only memory 10 is applied to an input 221 of the output amplifier 1 8. In response, the amplifier 18 generates at its output 23 an amplified signal which is fed to the optical coupler 14. In the optical coupler 14 the diode 8 is excited which puts the transistor 9 of the optical coupler into the conducting state which in turn renders a switching element 24, which is preferably a triac element, into the conducting state. The triac element 24 is a part of an exciter circuit for a contactor 230, with the excitation of which the machine begins to rotate in the forward direction. The exciter circuit for the contactor 230 is fed from a terminal 25 of the supply voltage source, via the contactor 230, the triac element 24 and switches 27 and 28 to a terminal 29 of the supply voltage source.The switch 27 is a switch which is closed if all cover parts are properly closed. The switch 28 is an emergency stop switch which is normally also closed. If one of these switches is opened the exciter circuit, which has just been described, for the contactor 230 is also opened.

The 'VOR' signal present at the output 210 of the read-only memory 10 is also applied to the first input of an OR gate 30. The output of this OR gate 30 is connected to an input 31 of the readonly memory 11. In response to the 'VOR' signal, the read-only memory 11 causes no more signal to be present at its output 20 and thus the lamp 80, associated with the ON button 4, to be extinguished. Simultaneously, the read-only memory 11 generates an output signal at its output 35 connected to the input 34 of the output amplifier 1 8. This output signal is amplified by the output amplifier 1 8 and fed from output 33 of the output amplifier 18, to a lamp 32 associated with the OFF button 3. This lamp 32, therefore, begins to glow. This means that the OFF button 3 can now be operated at any time in order to stop the machine.

Switching Off When the OFF button 3 is operated, a potential is applied to the intput 32 of the optical coupler 12 which excites the diode 8 associated with the input 32. The photo-transistor 9 associated with this diode is switched into a conducting state and generates a 'STOP' signal at the output 33 of the optical coupler 12. This 'STOP' signal is applied to the first input of an OR gate 350, the output of which is connected to the second input of an AND gate 34. The first input of the AND gate 34 is connected to the output 210 of the read-only memory 10. The output signal of the AND gate 34 sets the flip-flop 351 which stores the state in which the OFF button 3 was operated after the ON button 4 had been operated. At the output 36 of the flip flop 351 there is a signal which is fed via an OR gate 37 to an input 38 of the read-only memory 11.Simultaneously, this 'STOSTA' signal is fed via an inverter 39 to a terminal 40. The signal present at the terminal 40 and hereafter called 'HALT' signal causes the voltage regulating transformer, which sets the speed of the machine, to be driven toward its zero position.

The 'STOSTA' signal present at the input 38 of the read-only memory causes the signal present at the output 35 to be switched off. In this way the red lamp 32 is switched off. The extinguishing of the red lamp 32, which is associated with the OFF button 3, indicates to the operator that operating of the OFF button 3 has been recognized and accepted by the system.

The flip flop 351 stores the 'STOSTA' signal until the voltage regulating transformer, due to the 'HALT' signal present at the terminal 40, has been brought into its zero position, and therefore, generates, via a transistor 41, a 'NULL' signal at an input 89 of the read-only memory 10. This causes the 'VOR' signal present at the output 21 of the read-only memory 10 to be switched off.

Simultaneously, the flip flop 351 is reset.

If the On button 4 and the OFF button 3 are accidentally operated simultaneously, the 'START' signal is applied to the input 88 of the read-only memory 10 and the 'STOP' signal to the input 87 of the read-only memory 10. These signals, which are simultaneously present at the inputs 87 and 88 of the read-only memory 10, cause the 'START' signal generated by operating the ON button 4 to be disabled or blocked.

Opening the Cover during Machine Operation For safety reasons all covers or cover parts which can be opened, of the printing machine, are provided with switches which are put into their opened position if a cover part is accidentally opened. These switches are connected in series with one another. In Figure 2 these series connected switches are represented by the symbol designated by 220. If one switch of these switches 220 is opened, an input signal is applied to the input 41 of the optical coupler 12 which excites the photo-diode 8 associated with this input 41. This causes a 'SAFE' signal to be generated via the photo-transistor 9 at the output 42 of the optical coupler 12 and to be fed via the OR gate 43 to the input 45 of the read-only memory 10. This causes the 'VOR' signal present at the output 21 of the read-only memory 10 to be switched off.The triac element 24 subsequently interrupts the exciter circuit for the contactor 23 and the machine is immediately brought to a standstill.

The 'SAFE' signal at the input 45 of the readonly memory 10 is applied in time to the input 47 of the read-only memory 11. The read-only memory 11 causes the 'CLK' clock present at its input 48 to cycle the lamp 32, associated with the OFF button 3, via the output 35 of the read-only memory 11. The flashing lamp 32 informs the operator that the machine has been stopped because at least one cover part has been accidentally opened.

A second safeguard against accidents due to the cover being accidentally opened consists in that second switches 27, 28, associated with each cover part and also connected in series, are arranged in the exciter circuit of the contactors 230 and 93. If one of the series-connected further switches is opened the exciter circuit is immediately interrupted and the contactor 230 is switched off directly.

A further safeguard against accidental opening is achieved by the fact that, if a switch 27 or 28 which is arranged in the exciter circuit is opened, the diode 8 in the optical coupler 16 is excited.

This causes the 'NSTO' signal to be generated at the connection 49 if the photo-transistor 9 is conducting. This signal is fed to the second input of the above-mentioned OR gate 43 and has the same effect there as the signal generated by the switches 220 at the first input 42 of the OR gate 43.

When the accidentally opened cover is closed, the 'VOR' signal is not generated again automatically at the output 210 of the read-only memory 10. Rather, for this signal to be generated the ON button 4 must be operated again after the cover has been closed and after the flashing lamp 32 has been extinguished. This means that the conditions mentioned initially ('NULL' signal for a short period at the zero input of the read-only memory 10 and 'TIP' signal at input 3 of the readonly memory 10) must be present which lead to the lamp 80 associated with the ON button being illuminated.

Excess Current In the case of an excess current the speed of the machine is regulated down by the voltage regulating transformer. The excess current condition is picked up by the fact that, for example, the transistor 50 is switched into conduction. The signal generated by this is fed to a timing section 51 which is preferably resistancecapacitance (RC) section. The excess current signal generated by this timing section is applied to the second input of the OR gate 350. As described previously in connection with the generation of the 'STOSTA' signal, this causes the 'HALT' signal to be generated at the terminal 40, which 'HALT' signal causes the voltage regulating transformer to be regulated down.

Simultaneously, the excess current signal generated by the timing section 51 is applied to a flip flop 52 the output 53 which is connected to the input 54 of the read-only memory 11. The flip flop 52 stores the occurrence of the excess current signal and 'USTR' signal applied by the flip flop 52 to the input 54 of the read-only memory 11 causes an output signal, timed by the clock applied to the input 48 of the read-only memory 11, to be generated at the output 35 of the readonly memory 11, which output signal causes the lamp 32, associated with the OFF button 3, to flash.

Sheet Feed In the test which follows, the operation of the sheet feed button 5 and of the sheet stop button 6, which had already been mentioned in connection with Figure 1, is explained. The sheet feed can be started only if the sheet feed button is illuminated by the lamp 55. For this purpose an AND gate 57 is provided, the output of which is connected to an input 58 af the output amplifier 18 and the output 59, associated with the input 58, of the output amplifier is connected to the lamp 55. The first input of the AND gate 57 is connected to an output 56 of the read-only memory 11.At this output 56 a signal is present if the 'VOR' signal is present at the input 31 of the read-only memory 11 and if the 'TISTA' signal is not present at the input 60 of the read-only memory 11 and if, in addition, a 'PAP' signal is not present at the input 62 of the read-only memory 11. The 'TISTA' and 'PAP' signals will be explained later in detail. The second input of the AND gate 57 is connected to the terminal 61 (bottom left, Figure 2). At this terminal 61 the running-up signal 'HL' is present if the machine is just being run up to speed, that is to say when the regulating transformer is just being operated. Thus the sheet feed button 5 is illuminated if the 'HL' signal is not present at the AND gate 57, if the ON button 4 has been operated and if the 'TISTA' signal is not present at the input 60 and the 'PAP' signal is present at the input 62.This means that in this case the sheet feed button may be operated.

The 'PAP' signal is generated automatically at the input 62 of the read-only memory 11 if a check signal indicates that there is no paper. This check signal is applied, for example, by the switch 621 to the input 63 of the optical coupler 13. This causes the photo-diode 8 associated with this input 63 to be excited. This results in the 'PAP' signal being generated by the photo-transistor 9 at the output 64 of the optical coupler 13. This signal is also applied to the terminal 65 and causes the machine to run slowly.

If the 'PAP' signal is generated at the input 62 of the read-only memory 11 the lamp 55 is switched off in the above-mentioned manner.

Simultaneously, the lamp 80 associated with the ON button 4 is made to flash via the output 20 of the read-only memory 11 in conjunction with the 'CLK' clock present at the input 48 of the readonly memory 11.

After the ON-button 4 has been operated, the 'START' signal is generated at the input 88 of the read-only memory 10. This signal also causes the 'slow' command to be cancelled so that the machine works at the preselected speed and the green flashing lamp 80 is extinguished. After the preselected machine speed has been reached, the absence of the 'HL' and 'TISTA' signals, as mentioned above, causes the lamp 55 in the sheet feed button 5 to be switched on and the button 5 to be activated. After the sheet feed button 5 has been operated the sheet feed is enabled. The paper running through the machine generates the 'PAP' signal via a switch 621 and the optical coupler 13.This change of the address at the input 62 of the read-only memory 11 causes the lamp 56 in the sheet feed button 5 to be switched off via the output of this PROM and the output amplifier 18, and the lamp 66 in the sheet stop button to be switched on. If the paper does not start running, the 'TISTA' signal is generated after a period, which is predetermined by an RC section, has elapsed, and the running speed of the machine is reduced.

If the sheet stop button 6 is operated, a suction valve (not shown) is switched off which interrupts the paper feed. This, again, results in the 'PAP' signal being generated via the switch 621 and in the above-mentioned condition occurring. The lamp 66, which is associated with the sheet stop button, is connected to the input 67 of the output amplifier 1 8. The input 68, associated with this output 67, of the output amplifier 18 is connected to the output 69 of the read-only memory 11.

There is a signal at the output 69 if the 'PAP' signal is not present at the input 62 of the readonly memory 11. In this way the lamp 66 associated with the sheet stop button 6 is switched on whenever there is paper running through the machine.

Handwheel Advantageously, the printing machine used in connection with the present invention is provided with a so-called handwheel. As described in greater detail in West German Patent Application P 27 24 135.6-27 and the associated additional application P 28 35 915.1-27, the machine may also be moved manually, by operating the handwheel, at a reduced speed in both directions for purposes of adjustment, cleaning and so on.

A so-called tipping magnet 94 is provided which is energized whenever the voltage regulating transformer is in its tipping position and the machine is ready to be tipped. When the machine is started, that is to say when the ON button 4 is operated, this tipping magnet is de-energized. If now the handwheel is operated, during the printing operation, clockwise or anticlockwise, there is no signal being fed to the control logic since the tipping magnet is de-energized.

After the voltage regulating transformer has been driven into its zero position by operating the stop button 3, the address, which is now changed by the 'NULL' signal being applied to the second input 89, causes the read-only memory 10 to form the 'TISTA' signal at the output 61 of this readonly memory 10. This 'TISTA' signal enables the energization of the tipping magnet 94 via the output amplifier 1 8 (input 96---output 95). The operation of the tipping magnet 94 first causes a signal to be applied via the switch 76 to the input 77 of the optical coupler 13. The excitation of the diode 8 associated with this input 77 causes the photo-transistor 9, switched into conduction as a result of this excitation, to apply a 'TIP' signal to the output 78 of the optical coupler 13.This output 78 is connected to the input 83 of the read-only memory 10. The 'TIP' signal is applied to the terminal 40 and causes the voltage regulating transformer of the machine to be regulated up again up to the so-called tipping voltage. if now the handwheel is turned clockwise, that is to say in the forward direction, a signal is applied via the switch 70 to the input 71 of the optical coupler 1 3. The diode 8 associated with this input 71 switches the transistor 9 associated with it into the conducting state and the latter applies an output signal to the output 74 of the optical coupler 1 3. This output signal 'TIVOR' is applied to the input 85 of the read-only memory 10.In conjunction with the 'TIP' signal, appearing simultaneously at the input 83 of the read-only memory 10, this causes the 'VOR' signal to appear at the output 210 of the read-only memory 10. In the manner already described in connection with the switching-on process, this 'VOR' signal is applied to the input 221 of the output amplifier 1 8. In this manner the triac element 24 in the exciter circuit for the contactor 230 is rendered conductive and the machine starts to turn forward at a reduced speed.

If the handwheel is turned in the opposite direction, or the reverse direction, the switch 72 is actuated and a signal applied to the input 73 of the optical coupler 1 3. The diode 8 associated with this input 73 switches the photo-transistor 9 into the conducting state and a 'TIRUCK' signal is applied to the output 75. Since the output 75 is connected to the input 84 of the read-only memory 10 the 'TIRUCK' signal is simultaneously present at the input 84. If simultaneously the 'TIRUCK' signal is applied to the input 84 of the read-only memory 10 and the 'TIP' signal to the input 83 of the read-only memory 10, a 'RUCK' signal is generated at the output 89 of the readonly memory 10. This signal is applied to the input 90 of the output amplifier 80. The output 91, associated with the input 90, of the output amplifier 18 is connected to an optical coupler 1 5.

Due to the signal occurring at the output 91 of the output amplifier 1 8 a diode 8 is excited which renders a photo-transistor 9 conductive. This photo-transistor 9 of the optical coupler 1 5 switches the triac element 92 into the conductive state. This triac element 92 is arranged in an exciter circuit for the contactor 93 which, if activated, causes the machine to be turned backward at a reduced speed. The exciter circuit for the contactor 93 runs from the terminal 25 of the supply voltage source via the contactor 93, the triac element 92 and the switches 27 and 28 to the terminal 29 of the supply voltage source.

Claims (14)

1. A device for controlling a printing machine having a drive motor and a sheet feed system, the device comprising at least one read-only memory, operating elements for controlling the drive motor and sheet feed system, and each operating element being asociated with an illuminating element, wherein the illuminating elements are arranged to be controlled by the read-only memory in accordance with predetermined conditions or states at its inputs in such a manner that an operating element illuminated by its associated illuminating element, in a first manner indicates its operational readiness and that the operating element illuminated by its asociated illuminating element in a second manner indicates a further state of its operational readiness.

2. A device according to Claim 1, wherein a further read-only memory is provided which is arranged to control machine functions in accordance with predetermined conditions or states at its inputs and to generate input signals for said one read-only memory.

3. A device according to either of Claims 1 or 2, wherein an on button (4) is provided for switching on the drive motor, the illuminating element (80) associated with the on button (4) is illuminated in the first manner if no 'SAFE' signal (as herein described), indicating that a cover of the machine has been accidentally opened or that an emergency stop switch (28) has been operated, is applied to a first input (45) of the further read-only memory (10), if previously a 'NULL' signal (as herein described), indicating that a voltage regulating transformer has been reset which is provided for regulating the speed of the drive motor, was present for a short period at a second input (89) of the further read-only memory (10), and if at input seven (83) of the further read-only memory (10) the 'TIP' signal (as herein described) is present.

4. A device according to any of Claims 1 to 3, wherein when the on button (4) is operated which is illuminated in the first manner, a 'START' signal (as herein described) is generated at input three (88) of the further read-only memory; and the further read-only memory (10) generates a 'VOR' signal (as herein described) at its output one (210) if simultaneously there is no 'STOP' signal (as herein described), indicating that an OFF button (3) has been operated, present at its input four (87), no 'SAFE' signal at input one (45) of the further read-only memory (10), no 'TIVOR' signal (as herein described), indicating that a handwheel which is provided has been operated in the forward direction, at input five (85) of the further read-only memory (10), no 'TIRUCK' signal (as herein described), indicating that the handwheel has been operated in the reverse direction, at input six (84) of the further read-only memory, or a 'TIP' signal, indicating that a tipping magnet has been energized, at input seven (83), said tipping magnet being energized whenever the voltage regulating transformer is in its tipping position; and whereby the 'VOR' signal of output one (210) of the further read-only memory (10) is applied to input one (31) of the read-only memory (11), to thereby generate at output one (20) of the readonly memory (11) a signal which causes the illuminating element (80) associated with the ON button (4) to be switched off, and the 'VOR' signal closes an exciter circuit for a contactor (23) which excites the drive motor, and simultaneously at output two (35) of the read-only memory (11) a signal switches on an illuminating element (32) associated with the OFF button (3).

5. A device according to any of Claims 1 to 4, wherein when the OFF button (3) is operated after first having operated the ON button, at an input two (38) of the read-only memory (11) a 'STOSTA' signal (as herein described) is generated by virtue of the previously generated 'VOR' signal and the 'STOP' signal generated by operating the OFF button (3) being applied to one input each of an AND gate (37) the output of which is connected to input two (38) of the read-only memory (11), the read-only memory (11) then switching off the signal present at its output two (35) which causes the illuminating element (32) associated with the OFF button (3) to be switched off, and the 'SOSTA' signal causes the voltage regulating transformer to be driven to its zero position.

6. A device according to any of Claims 1 to 5, wherein when a cover of the machine is opened, the 'SAFE' signal is generated at input one (45) of the further read-only memory (10), the further read-only memory (10) then switches off the 'VOR' signal present at its output one (210) and in this manner interrupts the exciter circuit for a contactor (230) which switches on the machine, the 'SAFE' signal being applied to input three (47) of the read-only memory (11), the read-only memory (11) subsequently generating the possibility for the illuminating element (32) associated with the OFF button (3) to be switched on in a flashing manner by a 'CLK' clock signal (as herein described) present at input four (48) of the read-only memory, and when the cover is closed the 'VOR' signal can be generated again at output one of the further read-only memory only if first, on operating the ON button (4) again, the 'NULL' signal is present for a short period at input two (89) of the further read-only memory (10) and the 'TIP' signal is present at input seven of the further read-only memory (10).

7. A device according to any of Claims 1 to 6, wherein, where exccess current is applied to the drive motor, at a fifth input (54) of the read-only memory (11) an 'USTR' signal (as herein described) is generated, that subsequently at output two (35) of the read-only memory (11) produces a signal which is timed by the 'CLK' clock signal present at input four (48) of the readonly memory (11) and which illuminates the illuminating element (32), associated with the OFF button (3), in a flashing manner, and that the voltage regulating transformer is regulated down by the 'USTR' signal, and, in the zero position of the transformer, the 'VOR' signal, and thus also the motor is switched off by virtue of the 'NULL' signal generated at input two (89) of the further read-only memory (10).

8. A device according to Claim 7, wherein a timing section (51) is provided for delaying the 'USTR' signal.

9. A device according to any of Claims 1 to 8, wherein an illuminating element (55) associated with a sheet feed button (5) is switched off by virtue of a third output (56), which is connected to the first input of an AND gate (57), of the readonly memory having a signal generated if at input one (31) of the read-only memory (11) the 'VOR' signal is present, at input six (60) of the read-only memory (11) the 'TISTA' signal is not present, at input seven (62) of the read-only memory (11) a 'PAP' signal, which indicates that there is no paper, is not present, and if at the second input of the AND gate (57) an 'HL' signal, which indicates that the voltage regulating transformer is just running up, is not present.

10. A device according to Claim 9, wherein the illuminating element (55) associated with the sheet feed button (5) is switched off if at input seven (62) of the read-only memory (11) the 'PAP' signal is present and that simultaneously the illuminating element (80) associated with the ON button (4) can be switched on in a flashing manner via output one (20) of the read-only memory (11) in conjunction with the 'CLK' clock applied to input four (48) of the read-only memory (11) to indicate the absence of sheet feed.

11. A device according to Claim 10, wherein after the missing paper has been replenished, the 'PAP' signal is switched off at an input seven (62) of the read-only memory (11), that such renders it possible to switch off the signal causing, at output one (20), the flashing of the illuminating element (8) associated with the ON button (4), and that the signal which switches on the illuminating element (55) of the sheet feed button (5) is applied to output three (56) of the read-only memory (11).

12 A device according to any of Claims 9 to 11, wherein when the sheet stop button (6) is pressed, the paper feed is interrupted and the 'PAP' signal is generated at input seven (62) of the read-only memory (11), and the illuminating element (66) associated with the sheet stop button (6) is illuminated by a signal at output four (69) of the read-only memory (11) whenever there is no 'PAP' signal present at input seven (62) and the 'VOR' signal is present at the input (31).

1 3. A device according to any of Claims 1 to 12, wherein when the handwheel is operated in one direction, a 'TIVOR' signal is generated at input five (85) of the further read-only memory (10) and, when the handwheel is operated in the other direction, a 'TIRUCK' signal is generated at input six (84) of the further read-only memory (10), and simultaneously a 'TIP' signal is applied to input seven (83) of the further read-only memory (10), which causes the speed of the drive motor to be reduced for the operation of the handwheel, whereby the 'TIVOR' signal or the TIRUCK' signal and the TIP' signal cause the 'VOR' signal to be applied to output one (210) of the further read-only memory (10) or the 'RUCK' signal to be applied to output three (89) of the further read-only memory (10) and either the 'VOR' signal or the 'RUCK' signal at input one (31) of the read-only memory (11) causes the signal, which switches on the illuminating element (8) of the ON button (4), to be switched off at output one (210) of the further read-only memory (10), a 'TISTA' signal being generated at output two (61) of the further readonly memory (10), which is applied to input six (60) of the read-only memory (11) to cause the illuminating element (8) of the ON button (4), which had previously been switched off during the reduction of the speed, to be switched on again.

14. A device substantially as herein described with reference to, and as shown in, the accompanying drawings.