US2186113A - System of control fob feinting - Google Patents

Description

Jan. 9, 1940. E. H. LAABS 2,186,113

SYSTEM OF CONTROL FOR PRINTING PRESSES AND OTHER MACHINERY Filed Feb. 9, 1939 2 sheets-sheet 1 Jan. 9, 1940. E, H, A s 2,186,113

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Patented Jan. 9, 1940 UNITED STATES SYSTEM or common ron rnnvrmo masses AND OTHER. momma! Eric H. Laabs, Milwaukee, Wis., calm to Cutler-Hammer, Inc., Milwaukee, Win, a corporation of Delaware Application February 9,

20 Claims.

This invention relates to systems of control for printing presses and other machinery.

Newspaper presses commonly have been provided with all electric drives comprising a small 8 motor for starting, inching and threading speed and a large motor for printing speeds. Such drives have proven very successful for printing presses and other machines. On the other hand, a more recently developed hydraulic drive comprising an electrically driven hydraulic generator supplying a hydraulic motor has been used for printing press drive with some degree of success, the single hydraulic motor being used for starting, inching and running. However, the only outstanding operating advantage of the hydraulic motor drive over the two-motor electric drive lies in the intermediate speeds obtainable with the former, certain of the commonly employed types of electric motors presenting difliculties in Q obtaining the desired intermediate speeds. As against this advantage the hydraulic motor drive has numerous disadvantages, especially when used in connection with printing presses. As is well known, the starting torque of such a press is very much greater than its running torque, and thus the hydraulic motor to be successful must be much larger than it need be for driving the press at speed. Again there is a delay involved in starting the hydraulic motor, and this is undesir- 30 able particularly in inching where it should be possible to gauge the motion of the press from the length of time the inching button is held depressed, beginning the calculation at the moment the button is depressed. Furthermore, the 35 period of preparation of the press during which only inching and threading operations are required may run into hours, and where the hydraulic motor drive is used for inching and threading the motor operating the hydraulic generator must be always in operation to avoid further delays in starting, and this involves a great waste of electrical energy.

The present invention has among its objects 45 to provide a system enabling use of the hydraulic type of drive free from the aforementioned and other disadvantages. v

Another object is to provide a system which in part is hydraulic and in part electric to obtain the aforementioned and other advantages of both hereinbefore discussed types of drives.

Another object is to provide such a composite system which will afford control of the press or other driven machine in substantially the same manner as that afforded by an all electric system.

1939, Serial No. 255,555

Other objects and advantages of the invention will hereinafter appear.

Oneembodiment of the invention is illustrated in the accompanying drawings which will now be described, it being understood that the embodi- 6 ment selected for illustration is susceptible of various modifications without departing from the scope of the appended claims.

' In the drawings,

Figure 1 is a schematic view showing the driven and driving elements of the system.

Fig. 2 shows power connections for the electric motor driving the hydraulic generator employed.

Fig. 3 shows the power circuits for a separate electric motor which is employed.

Fig. 4 shows the power connections for the electric pilot motor of the hydraulic generator unit.

Fig. 5 shows the control instrumentalities and the control circuits in an across-the-line form, and

Fig. 6 is a chart showing the windings and contacts of the various switches or relays of Fig. 5 coordinated by vertical alignment and aligned horizontally with Fig. 5 to indicate their respec- 2s tive positions therein.

Referring to Fig. 1, there is schematically shown a press I having a drive shaft 2 to which is connected an electric motor I and a hydraulic motor 4. In practice the motor I preferably is connected to the shaft 2 by a V-belt or silent chain 5, although any other suitable connections might be employed. It is contemplated to employ the hydraulic motor 4 only for printing speeds and to utilize the electric motor 3 for a starting, inching and threading. Thus it may be assumed that the motor 3 is of the type and size usually employed for starting, inching and threading, said motor preferably being connected to shaft 3 through an over-running clutch 6, pro- 40 vided for freeing the shaft 2 from the electric motor drive when the hydraulic motor takes over the drive. The overrunning clutch 6 could of course be replaced by a suitably controlled electromagnetic clutch. As shown the overrunning a clutch 8 is mounted on shaft 2 and may be connected to motor 3 by gearing as shown or by a V-belt or by a silent chain.

For supplying the hydraulic motor there is shown schematically a commercial form of unit comprising hydraulic generator ll driven by an electric motor H and suitably piped to the hydraulic motor through a valve I! having an operating solenoid I l. The piping also includes a relief valve ll. This unit provides for regulation 3 having a suitably operated limit switch l6.

of the speed of the motor 4 through regulation at the generator' it, this regulation being accomplished through the medium of a pilot motor l6 As will be understood, the limit switch I6 stops the pilotwmotor when the generator regulator has been driven to either of two extreme limits. In addition to the contacts required for such limits the limit switch i6 is provided with contacts hereinafter set forth to be operated in intermediate positions of said switch. Also as will be understood, the valve I2 is to be operated by its solenoid whenever the press is set in motion. The system illustrated being as aforestated of a well known type and its specific form being immaterial to the present invention further description thereof appears needless. 7

Referring to Fig. 2, the motor ll employed to drive the hydraulic generator is shown as of the three phase alternating current type connected to supply lines L L, L through a suitable panel which preferably includes an overload device comprising contacts ill and a trip winding 22. This trip winding 22 is shown as connected in series with its contacts 2| across supply lines L --L through a double pole knife switch 23, a normally closed stop switch 24 and normally closed contacts 26' of a relay 26. Thus opening of the "stop" switch 24 or relay 26 will have the same effect as response of the overload, and as will be understood operation of any one of these instrumentalities would be utilized in one of the well known ways to effect disconnection of motor Ii. A relay 26 has its winding connected across the leads from lines L and L said relay having normally open contacts 26' and serving a purpose hereinafter explained. The relay 23, as will be apparent, is energized to close its contacts 26 while motor I I is running and to release said cTontacts when said motor is disconnected from circuit.

Referring to Fig. 3, the starting and inching motor 3 is shown as comprising a 3 phase alternating current motor supplied from lines L, U, L hrough a triple pole knife switch 33, fuses 3| and an electromagnetic main switch 32 having normally open contacts in each phase of the circuit. Two phases of the motor circuit include overload windings 33. Assuming the knife switch to be closed the motor 3 may be started and stopped for inching the press by energizing and deenergizing the electromagnetic main switch 32.

Referring to Fig. 4, the pilot motor l6 for the hydraulic generator is shown ascomprising a 3 phase alternating current motor supplied from lines L L and L through fuses 36, a triple pole knife switch 34 and on" and o electromagnetic switches 36 and 31, respectively. Each of switches 36 and 31 is of the triple pole type having normally open contacts in each of the three phases of the motor circuit, and these switches have different line connections whereby they afford operation of the motor l6 in reverse directions, selectively. As will be understood, when it is desired to operate the pilot motor for increasing the speed of the hydraulic motor the on switch is energized until the desired speed has been obtained, whereupon it is deenergized, the speed change being governed by the duration of the pilot motor. On the other hand, when it is desired to decrease the speed of the hydraulic motor the o switch is energized to effect operation of the pilot motor in a reverse direction until the desired speed change has been effected whereupon the ofl switch is to be deenergized.

Two phases of the pilot motor circuit are preferably provided with overload coils 46 and II, respectively, and preferably the pilot motor is provided with an electrically controlled brake 42 shown as connected-to all three phases of the motor circuit.

Further referring to Fig. 4, the same also shows the power connections for the solenoid l3 of the valve l2. More specifically it shows this solenoid connected across lines L and L through normally open contacts 63 of an electroresponsive relay 63.

Referring now to Fig. 6, the same shows at the bottom thereof the winding of relay 26 of Fig. 2, and near the middle the winding of switch 32 of Fig. 3. Also at the top of this figure are shown the windings of electromagnetic on and fofl' switches 36 and 31 of Fig. 4, and below these the winding of relay 63 of Fig. 4. The windings 36 and 31 have in circuit therewith contacts 46 and ll to be actuated by the overload coils l3 and 4| of Fig.4.

The additional relays shown in Fig. 6 will best be understood by first referring to Fig. 6. These relays include an of! relay 60 having normally open contacts 6i] and normally closed contacts 60' and an on relay 6| having normally open contacts 6|, 6i and 6l. These relays control the windings of the "off and on switches 36 and 31, respectively. The relays also include a stop relay 52 having normally closed contacts 62 and normally open contacts 62 62 and 62, an inch" relay 63 having normally open contacts 63*, 63 and 63 and normally closed contacts 63, a safe after inch" relay 64 having normally open contacts 64 and 64 and normally closed contacts 64, a run relay 66 having normally open contacts 66*, 66 and 66, a reset relay 66 having normally open contacts 66* and a safe relay 61 having normally closed contacts 6''. Relay 63 is here shown as having normally open contacts 66 and normally closed contacts 68', whereas as shown in Fig. 4 it additionally has normally open contacts 63. A relay 69 having normally-open contacts 63* and a relay 60 having normally open contacts 66* and 6|) are also included.

Fig. 5 additionally shows an of! push button switch 6|, a stop push button switch 62, an inch push button switch 63, an on push button switch 64, a "preset push button switch 66, a reset push button switch 66, a safe-run push button switch 61 and an emergency stop push button switch 63.

Fig. 5 additionally shows contacts l6 and Il of limit switch I6 (Fig. 1) to be opened in extreme positions respectively of said limit switch, l6 being the on limit contacts in circuit with relay windings 6| and 63, and i6 being the of! limit contacts in circuit with relay windings 63 and 69. Also it shows contacts l6 of said limit switch connected in circuit with relay winding 32, said contacts being arranged to be opened shortly after the pilot motor i6, Fig. 1, starts the limit switch I 6 away from of! position. Further Fig. 5 shows contacts l6 of limit switch i6 connected in circuit with relay winding 6|, these contacts being arranged for opening slightly in advance of contacts 16 and to be short-circuited by contacts 26 of relay 26 (Fig. 2) upon energization of said relay. The contacts 33'' shown in circuit with relay winding 62 are adapted to be operated by either of the overload windings 33 (Fig. 3).

The control is such that before the press or other driven machine may be started by pressing either the "inc or the on buttons the reset" push button switch 55 must first be depressed. when push button switch 55 is depressed the winding of relay 55 is connected across lines L L through said push button switch and normally closed contacts 51 of relay 51. Relay 55 thereupon responds to connect through its contacts 55' the winding of relay 52, across lines L and 11. through the overload switch 33 and resistance r. Relay 52 then responds and through its contacts 52 establishes a maintaining circuit for itself and through its contacts 52 establishes a connection between line L and certain of therelay windings. Furthermore relay 52 in responding completes through its contacts 52' a maintaining circuit for the winding of relay 55, said maintaining circuit including normally closed contacts 54 of relay 54 and shuntingpuslr button switch 55.

N With relays 52 and 55 energized the usually employed signal system would indicate and depression of the inch push button switch 53 then is effective for inching. Depression of this push button switch connects the winding of inch" relay 53 across lines L, L through the normally closed contacts 51' of relay 51, subject to disconnection upon release of said push button switch.

Relay 53 in responding establishes a connection from line L throughits contacts 53 to and through the winding of the starting switch 32 of the inching motor, to and through limit switch IS to and through the now closed contacts 52 to line L Switch 32 thus responds. to start the small motor 3 for inching subject to termination of the inching operation by release of the push button switch 53 to deenergize the inching relay 53 which in turn deenergizes the switch 32.

. In themeantime during the inching operation the solenoid operated valve i2, Fig. l, is energized. The inching relay 53 upon responding acts through its contacts 53 to establish a connection from line L to and through the winding of relay 58 to and through the now closed contacts 52 to line L This relay completes the circuit of the solenoid l3 shown in Fig. 4. When the inch push button is released then the relay 58 is deenergized through deenergization of the inching relay-to disconnect the valve solenoid from circuit.

During the inching operation the relay 55 also is energized and this effects restoration of circuits following release of the inc push button switch, such as to necessitate repeating of the reset cycle first described above prior to a further inching operation or to starting through operation of the "on button. The energizing circuit of relay 54 is completed by contacts 53 of the inch relay and relay 54 in responding establishes through its contacts 54 a maintaining circuit shunting the contacts 53. Also relay 54 in responding closes its contacts 54 connected in a shunt around the winding of. relay 52. This shunt includes a resistance r, and normally closed contacts 53 and'58 of relays 53 and 55. Thus when relays 53 and 55 are deenergized following release of the inch" push button switch the relay 52is deenergized by shunting of its winding, and releases to disengage its contacts 52 restoring the circuits to the condition shown.

Assuming repetition of the resetting cycle followed by depression of the on" push button switch instead of the inch push button switch the "on relay 5| is energized. The circuit of the on" relay may be traced from line L through on" push buton switch 54 and normally closed contacts 55'' of the ofP' relay to and through winding II to andthrough limit switches l5 and II in series to and through normally closed contacts 51' of relay 5! to line L. The on" relay remains energized only so long as the on" push button switch is held depressed. The on" relay 5| upon responding connects in parallel with its 55 and 5| complete the energizing circuit of the on" switch 35 of Fig.4. This, assuming that the hydraulic generator 'is in operation, provides for starting and accelerating the hydraulic motor to take over the press drive, the degree of accelera- I tion being determined by the length of time the on push button is held depressed. As will be understood, when the on push button is released the pilot motor |5 controlling the hydraulic generator is arrested for continued operation of the press at the selected speed until stopping or a speed change is directed. A further increase in speed may of course be obtained by again depressing the on push button switch 54. If, on the other hand, a speed reduction is desired, then the "oflP push button switch Si is depressed to connect across lines L and L the winding of off" relay 50. Off relay in responding acts through its contacts 50* to energize the oif switch 31. of Fig. 4 to operate the pilot motor in a reverse direction subject to arrest when the off push button switch is released.

If when the on relay 5| is energized to start the pilot motor awayfrom off limit the hydraulic system is not in operation then shortly the limit switch contacts I5 open to deenergize on relay 5| to stop the pilot motor. The slow speed drive continues and when the hydraulic system is started relay 25 responds to short-circuit limit switch contacts ii for reenergization of the on. relay when the on push button switch is closed. When the drive is taken over by the hydraulic motor the limit switch contacts l5 open to deenergize relay 32 for disconnection of the electric starting motor 3.

With the press in operation as the result of depression of the on push button switch stopping may be effected by depressing the stop push button switch 52. The push button switch 62 when depressed alone shunts the winding of stop relay 52 through resistance r causing.

deenergization of said stop" relay with consequent restoration of circuit connections, such as to necessitate repetition of. the first described reset cycle before the press can be restarted.

Stopping automatically is provided for by a paper break switch 10 which when closing while the press is in operation establishes a shunt for the winding of stop" switch 52 which extends through said paper break switch, the normally closed contacts 53 of the inch relay and the-- contacts 54 of relay 54 which is closed during running operation.

- Throughout the time that oilP' limit switch I6 is closed the winding of relay 59 is connected across lines L and L and this relay in responding parallels through its contacts 59 the circuit including contacts 53' and 54 of relays 53 and 55, respectively. Thus prior to restarting while the paper break switch is closed the pilot motor must be operated to of! position to open contacts It for deenergization of relay I9, thereby confining operation to a threading speed until the paper break is repaired to restore the paper break switch to open position.

In some instances it is desirable to bring the press to a preset speed by momentary depression of a push button, and this can be accomplished by so depressing push button switch 65. This establishes circuit from line L to and through the winding of relay 80, to andthrough the limit switch IE", to and through contacts 51 of relay 51 to line L Relay 60 upon responding completes through its contacts 60 a maintaining circuit for itself and through said contacts and contacts 60' in series a circuit for the on relay 5|. Accordingly response of relay 80 provides for continued energization of on relay 5i until it is deenergized by operation of the limit switch it when the desired speed has been attained.

The safe run switch 61 when closed provides for connection across lines L and L of the winding of relay 51 which upon responding opens its contacts 51, thus disconnecting from line L the windings of the relays controlled by the various push button switches other than the off push button switch.

Depression of the emergency push button 6 connects across line L the winding of relay 25 of Fig. 2, thus providing for shut-down of the motor operated generator set.

What I claim as new and desire to secure by Letters Patent is:

1. For printing presses and other machines, the combination with an hydraulic type drive comprising a generator and motor supplied thereby, of an electric drive comprising a motor capable of starting the driven machine, and control means for said drives insuring starting of the driven machine always by said electric drive and afiording thereafter transfer of drive to said hydraulic drive.

2. For printing presses and other machines, the combination with an hydraulic type drive comprising a generator and motor supplied thereby, of an electric drive comprising a motor capable of starting the driven machine, and control means for said drives insuring starting of the driven machine always by said electric drive, af-

fording slow speed operation of the driven machine by said electric drive and affording transfer of drive to said hydraulic drive for higher speed operation of the driven machine.

3. For printing presses and other machines, the combination with an hydraulic drive comprising a generator and a motor supplied thereby, of an electric drive comprising a motor capable of starting the driven machine, and control means for said drives insuring starting of the driven machine always by said electric drive, affording slow speed operation of the driven machine by said electric drive and affording transfer of drive to said hydraulic drive for higher speed operation of the driven machine, said control means including means affording regulation at will and in small increments or decrements of the speed of the driven machine when operated by said hydraulic drive.

4. For printing presses and other machines, the combination with an hydraulic type drive comprising a generator and motor supplied thereby, of an electric drive comprising a motor capable of starting the driven machine, and control means for said drives insuring starting of the driven machine always by said electric drive and affording thereafter transfer of drive to said hydraulic drive and regulation of the speed of said hydraulic drive, said control means affording a speed of said hydraulic drive closely approximating that of said electric drive for such transfer.

5. For printing presses and other machines, the combination with an hydraulic type drive comprising a'generator and motor supplied thereby, of an electric drive comprising a motor capable of starting the driven machine, and control means for said drives insuring starting of the driven machine always by said electric drive and affording thereafter transfer of drive to said hydraulic drive, said control means including means rendering such transfer of drive dependent upon establishment of certain operating conditions of said hydraulic drive.

6. For printing presses and other machines, the combination with an hydraulic type drive comprising a generator and motor supplied thereby, of an electric drive comprising a motor capable of starting the driven machine,. and control means for said drives insuring starting of the driven machine always by said electric drive and affording thereafter transfer of drive to said hydraulic drive, said control means including means whereby if such transfer of drive is attempted when said hydraulic drive is not in operation said electric drive will be maintained effective until said hydraulic drive is started or until stopping of said electric drive is directed.

7. For printing presses and other machines, the combination with an electric drive comprising a motor capable of starting the driven machine and operating it at slow speed, of an hydraulic type drive comprising a generator and a motor supplied thereby capable of operating the driven machine at a speed approximating the aforementioned slow speed and at higher speeds, and control means to start the first mentioned motor and thereafter start the second mentioned motor for transfer of drive from the electric drive to the hydraulic drive when the two drives have substantially like speeds, said control means after such transfer affording regulation of the speed of said hydraulic drive in small increments and decrements.

8. For printing presses and other machines, the combination with an electric drive comprising a motor capable of starting the driven machine and operating it at slow speed, of an hydraulic type drive comprising a generator and a motor supplied thereby capable of operating the driven machine at a speed approximating the aforementioned slow speed and at higher speeds, and control means to start the first mentioned motor and thereafter start the second mentioned motor for transfer of drive from the electric drive to the hydraulic drive when the two drives have substantially like speeds, said control means after such transfer affording regulation of the speed of said hydraulic drive in small increments and decrements and said control means affording disconnection from circuit of said electric drive after transfer to the hydraulic drive.

9. For printing presses and other machines, the combination with an electric drive comprising a motor capable of starting the driven machine and of operating it at slow speed and an over-running clutch through which said motor drives, of an hydraulic type drive comprisinga generator and a motor supplied thereby capable of operating the driven machine at a speed approximating the aforementioned slow speed and at higher speeds,

and control means to start the first mentioned motor and thereafter start the second mentioned motor for transfer of drive from said electric drive to said hydraulic drive at a speed of the latter only slightly above that of the former, said control means following such transfer aflordlng regulation of the speed of said hydrauliis drive in small increments and decrements.

10. For printing presses and other machines, the combination with an electric drive comprising a motor capable of starting the driven machine and of operating it at slow speed and an over-running clutch through which said motor drives, of an hydraulic type drive comprising a generator and a motor supplied thereby capable of operating the driven machine at a speed approximating the aforementioned slow speed and at higher speeds, and control means to start the first mentioned motor and thereafter start the second mentioned motor for transfer of drive from said electric drive to said hydraulic drive at a speed of the latter only slightly above that of the former, said control means following such transfer affording regulation of the speed of said hydraulic drive in small increments and decrements, and said control means insuring use of said electric drive in starting the driven machine for protection of said hydraulic drive against overloads incident to starting.

11. For printing presses and other machines, the combination with an electric drive comprising a motor capable of starting the driven machine and operating it at slow speed, of an hydraulic type drive comprising 'a generator and a motor supplied thereby capable of operating said machine at a speed approximating the aforementioned slow speed and at higher speeds, and control means for said drives to start the same progressively for starting of the driven machine by said electric drive and for continued operation by said hydraulic drive or optionally to start only said electric drive for operation of the driven machine at slow speed only, said control means including means to guard against use of said hydraulic drive for starting.

12. For printing presses and other machines, the combination with an electric drive comprising a motor capable of starting the driven machine and operating it at slow speed, of an hydraulic type drive comprising a generator and a motor supplied thereby capable of operating said machine at a speed approximating the aforementioned slow speed and at higher speeds, and control means for said drives to start the same progressively for starting of the driven machine by the electric drive and for continued operation by the hydraulic drive or optionally to start only the electric drive for operation of the driven machine at slow speed only, said control means including means to guard against use of the hydraulic drive for starting and preventing starting of the hydraulic drive except when the electric drive is operating.

13. For printing presses and other machines,

an electric drive comprising a motor capable of,

starting the driven machine and operating it at slow speed and an over-running clutch through which said drive operates the driven machine, of an hydraulic type drive comprising a generator and a motor supplied thereby capable of operating said machine at a speed only slightly above the aforementioned slow speed and at higher speeds, and control means for said drives to start said electric drive alone or to start b'oth drives, said control means rendering starting of said hydraulic drive dependent upon prior starting and continued operation of said electric drive.

14. For printing presses and other machines. an electric drive comprising a motor capable of starting the driven machine and operating it at slow speed and an over-running clutch through which said drive operates the driven machine, of an hydraulic type drive comprising a generator and a motor supplied thereby capable of operating said machine at a speed only slightly above the aforementioned slow speed and at higher speds, and control means for said drives to start said electric drive alone or to start both drives,.

said control means rendering starting of said hydraulic drive dependent upon prior starting and continued operation of said electric drive and stopping said electric drive automatically after transfer from said electric drive to said hydraulic drive.

15. For printing presses and other machines, the combination with an electric motor drive for starting and for slow speed operation of the driven machine, of an hydraulic type motor drive for substantially like slow speed and also higher speed operation of the driven machine and control means for said drives to effect operation of said electric drive alone or operation of said hydraulic drive alone, said control means including means insuring against starting of said hydraulic drive except when said electric drive is operating and said control means having a cycle of operation for safety purposes and including means necessitating its operation through such cycle for restarting whenever the driven machine is stopped following operation by either of said drives.

16. For printing presses and other machines, the combination with an electric motor drive for starting and for slow speed operation of the driven machine, of an hydraulic type motor drive for substantially like slow speed and also higher speed operation of the driven machine and control means for said drives affording inching or continuous operation of the driven machine by said electric drive alone or continuous operation by said hydraulic drive alone, said control means including means insuring against starting of said hydraulic drive except when said electric drive is operating and said control means having a cycle of operation for safety purposes and including means necessitating its operation through such cycle for restarting after each inching operation and after continuous operation of the driven machine by either of said drives.

17. For printing presses andother machines, the combination with an electric motor drive for starting the driven machine and operating it at slow speed, of an hydraulic type drive comprising a power driven generator and a motor supplied thereby for operating the driven machine through an increased speed range, and control means for said drives including means to render the motor of said hydraulic drive idle while its generator operates and means to start said electric drive and thereafter start said hydraulic drive but only if operation of said electric drive is continued through the starting period of said hydraulic drive.

18. For printing presses and other machines, the combination with an electric motor drive for starting the driven machine and operating it at slow speed, of an hydraulic type drive comprising a power driven generator and a motor supplied thereby for operating the driven machine through an'increased speed range, and control means for said. drives including means to render the motor of said hydraulic drive idle while its generator operates and to render starting of said hydraulic drive dependent upon prior starting or said electric drive and operation thereof at the time starting 01' said hydraulic drive is directed and said control means also including means tending to continue operation of said electric drive if the generator of said hydraulic drive is not in operation when starting of said motor to be supplied thereby is directed.

19. For printing presses and other machines, the combination with an electric motor drive for starting the driven machine and operating it at slow speed, of an hydraulic type drive comprising a power driven generator and a motor supplied thereby for operating the driven machine through an increased speed range, and control means for said drives including means to render the motor of said hydraulic drive idle while its generator operates, and means to start said electric drive and thereafter start and accelerate said hydraulic drive and means effective to restrict accelerating operation of the last mentioned means in the event starting of said hydraulic drive is directed while its generator is not in operation.

20. For printing presses and other machines, the combination with an electric motor drive for starting the driven machine and operating it at slow speed, of an hydraulic type drive comprising a power driven generator and a motor supplied thereby for operating the driven machine through an increased speed range, and control means for said drives including means to render the motor 01' said hydraulic drive idle while its generator operates, means to start said electric drive and thereafter start and accelerate said hydraulic drive, the last mentioned means having a motor driven device to effect a gradual increase in speed of said hydraulic drive, and means arrestingthe operation of said motor driven device when starting and acceleration of said hydraulic drive is directed at a time that its generator is not in operation.

ERIC H. LAABS.

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