US2248393A

US2248393A - Controlling means for hoisting mechanisms

Info

Publication number: US2248393A
Application number: US339655A
Authority: US
Inventors: Ernst L Schwarz
Original assignee: Whiting Corp
Current assignee: Whiting Corp
Priority date: 1940-06-10
Filing date: 1940-06-10
Publication date: 1941-07-08
Anticipated expiration: 1958-07-08

Description

y 1941- a L. scHwARz 2,

CONTROLLING MEANS FOR HOISTING MECHANISMS Filed June 10, 1940 s Sheets-Shani L0 WEE/Ni &

WTII

July 8, 1941. E. L. SCHWARZ CONTROLLING MEANS FOR HOISTING MECHANISMS Filed June 10, 1940 3 Sheets-Sheet 2 y 1941 E. L. scHwARz 2.248 393 CO NTROLLING MEANS FOR HQISTING MECHANISMS v Filed June 10, 1940 5 Sheets-Sheet 5 h ereior mNG ham. i v v 30 Patented Juli 8, 1941 sMs Ernst L. Schwarz, Chicago, 111., asslgnor to Whiting Corporation, Harvey, Ill., 1; corporation of Illinois Application June 10, 1940, Serial No. 339,655

Claims.

The invention relates to controlling means for hoisting mechanism.

The objects of the invention'are to provide hoisting mechanism which comprises an induction motor, winding mechanism operable by the motor, and an electrically-controlled brake adapted to be appliedt'o control the operation of the winding mechanism by'the load, with improved controlling mechanism whereby: the lowering of theload may be selectively controlled by oversynchronous operation of the motor or accurate brake-regulation according to the character of the work or for accurate brake control in lowering varying loads; in which the controller is unsymmetrical to produce different regulating conditions for hoisting and lowering; in which the controller is provided with a plurality of sta tions for initial lowering with smooth retardation from high speed to low speed; in which resistances in the motor of the lifting motor during oversynchronous lowering are so dimensioned that the lowering speed for the heaviest predetermined load has. a higher than rated normal speed but limited value for safe and fast lowering for all loads; which includes a. reversing switch for selective brake regulation or oversynchronous lowering if no brake-regulation is ,desired; in which the controlling mechanism is normally set for lowering under brake-regulation and with readily operable switch-means for oversynchronous lowering; in which the controller is provided with a plurality of starting stations for lifting and resistance in the rotor of the lifting motor is dimensioned so that loads up to 80% of the full load will start under brake-regulation and at the second station 100%01' the load will start slowly in hoisting so that brake-regulation will not be necessary at the second station; in which, during initial brake-regulated lowering, the resistance in the rotorof the lifting motor is eliminated in lowering by the overhauling load and the brake-regulating motor is operated responsively to the variations in frequency and voltage produced by the rotor of the lifting motor so that it is only necessary for the regulating-hrake to dissipate the energy of the lowering load, thereby effecting economical use of the regulating-brake and a lower regulated speed; and other objects which will appear from the detailed description.

The invention consists in the several novel features which are hereinafter set forth and which are more particularly defined by claims at the conclusion hereof.

In the drawings: Fig. l is a diagrammatic view of mechanism for controlling the hoisting mechanism embodying the invention. Fig. 2 is a plan of the hoisting mechanism. Fig. 3 is a side elevation of the regulating-brake and the electrohydraulic mechanism tor'controlling the application of the brake. Fig. 41s a section on line 4-4 of Fig. 3. Fig. 5 is a diagram of a modified form of theinven'tion for-selectively controlling lowering by brake-regulation or oversynchronous lowering. l r

The invention is exemplified with hoisting mechanism which comprises a drum Rfor winding and unwinding a cable for raising and lowering leads; an electric motor M for operating the hoisting mechanism and connected to drive the drum N through suitable speed reducing gearing n of anysuitable construction; a brake 0 adapted to be applied to the shaft oi motor M for retarding said shaft and comprising a brake-drum o and brake-shoes o electro-divdraulic brake-controllmg device comprising a I squirrel-cage, electric motor C and an impeller oil-pump P operable by motor C to regulate the application of the brake-shoes to drum 0. The motor M is of the thrce-phaseinduction asynchronous type and comprises a stator M and is adapted to be connected by a three-pole line switch F to a source of high voltage current, for example 440 volts, and a rotor M wound for low voltage, for example 140 volts.

The improved controlling mechanism-comprises a drum-type electric controller A ior manually controlling the operation of the hoisting mech-- anism in raising and lowering loads; a three phase transformer G including a low voltage (140 volts) coil 0' connected to rotor 1% for operating motor C responsively to variations in the voltage and frequency produced by the rctor M of motor M, and a high voltage ciao volts) coil 0 adapted to be connected to the stator of motor C; resistors R R R in the circuits for rotor M a relay D comprising magnets D D for controlling switches to altemat-elzr connect the motor C to the stator M of the motor M and to the coil 9' of the transformer G; and a switch E comprising poles e, e e for selectively con- M of motor M. The armatures of magnets D, D are electrically interlocked and may also be mechanically interlocked (not shown) so that when one set of switches is closed the other will be open.

The controller A comprises a drum or and is illustrated as rotatable from a neutral position, indicated at zero, through seven lowering stations and seven lifting stations which are indicated by lines correspondingly numbered.

The controller A also comprises a series of contact-fingers 23, 24, 25, 25, 21 and 28 for controlling circuits through the stator M of motor M and segmental contacts 2|, 25', 21, 28 on drum a adapted to engage fingers 24, 25, 21, 28, respectively, for raisingloads and contacts 29, 24 26 2'! on the drum for engaging fingers 23, 2t, 26, 21, respectively, for lowering loads. Contacts 28, 21 21 and 26 are electrically connected. Contacts 21 26 are electrically connected. Contacts 23, 24' are electrically con- I press spring to release the brake-shoe from nected. Contacts 24, 25 are electrically connected. The controller is also provided with fingets 35, 36 and 31 engageable by segmental contacts 35', 36 and 31 on the drum a, respectively, in raising loads and engageable by. segmental contacts 35", 18 and 2?", respectively, in lowering loads. The controller is also provided with contact-fingers 46, 41, 48, 49, 50, SI, 52, 53 and 54 for connecting resistors R R, and R to, and short-circuiting them from, the circuits for the rotor W of the motor M. The drum a is provided with segmental contacts 48, I1,

48, 49', 50, Si, 525,52, 54* engageable by contact-fingers 43, 41, l8, I9, 50, Si, 52, 53, 54, respectively, in raising loads and by segmental contacts 46 41, 48 49 50 51 52 53 54, respectively, in lowering loads. The segmental contacts on drum 0 are relatively positioned and of the relative length shown in Fig. 1. g

The controller is electrically connected to the line switch F, the rotor M, the resistors R, R, R the stator of motor C, the transformer G, the relay switches and the switch E, as illustrated in Fig. 1 and as will more clearly appear from the description of the control mechanism. A high-limit switch H is provided in the circuits between the controller and the stator M as shown.

The impeller pump P comprises a cylinder 12 a piston p slidably mounted therein, and a rotary impeller p adapted to force oil from the upper side of the piston to its lower side to release the brake when the impeller is driven by motor C. The impeller is mounted in the piston and has a sliding driving connection with the shaft of the rotor C of motor C. The stator C of motor C is mounted on the upper end of the pump. When the impeller is stopped the oil flows through the openings in the piston from its lower side to its upper side to apply the brake- .shoes 0 to drum 0 The piston is provided with a by-pass duct 9 so that the speed of the liftring of the piston will vary proportionately to the speed of the impeller.

The brake-shoes are carried by pivoted levers 0". Piston p is connected to shift the brakeshoes 0 by rods p, a lever o pivotally connected to the upper end or a crosshead p on rods 11 and pivotally connected, as at 0, to one of the levers o. A spring o is applied to normally force the brake-shoes against the drum. Spring 0 surrounds a rod 0 which is pivotally connected, as at o", to one oi the brake-shoe levers and extends through a stirrup-link 0'. which is pivotally the drum. The degree of movement of lever 0 is responsive to the movements of piston p to graduate the force of the spring 0 and apply the brake-shoes to the drum with varying force for regulating the braking torque.

When switch E is set in the position shown by full lines in Fig. l, the operator, through controller A, controls the operation of brake-motor C for complete release of the regulation-brake and oversynchronous lowering of loads. When switch E is set into position indicated by dotted lines in Fig. l, the operation of motor C for brake-regulation is controlled on the first lifting station and the first lowering station responsively to the variation in voltage and frequency in the circuits of rotor M.

This controlling mechanism is adapted for lifting the load with brake-regulation at the first station for accurate placement of the loads; for

lifting the loads with-out brake-regulation; for lowering the loads with brake-regulation at the first two lowering stations; and for lowering the loads without brake-regulation. When switch E is set in its full line position and the controllerdrum a is shifted to close switches :1 d", d, the stator of motor C will be connected to the stator M of motor M. In lowering loads, the load overhauls the motor and drives rotor M of motor M. This motor then operates as an asynchronous generator and develops energy into the main line, and the stator of motor C has full voltage and completely releases the brake. When the stator of motor C is disconnected from the stator M at switches d", d, d and magnet D closes switches (1, d d, the stator of motor C will be connected to the rotor M of the lifting motor through transformer G and the operation of the motor C to regulate the release of the brake will be controlled by variation in voltage and frequency in the circuits of rotor M.

The stator windings of motor C, when switches 11'', d, d are closed, are connected to terminals of the stator M of the hoisting motor M. The brake is designed to regulate slipping in response to the variations in the pressure'of oil in the pump P which is automatically controlled by the speed of motor C. This regulation is utilized for speed regulation in lowering and in lifting. The frequency and voltage of the current produced in the circuits of rotor M diminish with increasing speed and as the frequency. drops the speed of motor C drops proportionately while it is connected to the rotor M through switches d", d, and d. Variations in the speed of motor C produce variations in the oil pressure in the impeller pump P and in the braking torque so that the brake can be regulated almost independently of the load. As a result, the brake is caused to slip and eifects regulation to approximately, say, 20% of the speeds for all loads when lifting and lowering with brake-regulation. I

' The operation will be as follows: when the drum a is in its neutral position the drum-fingers will be disconnected from all contacts on the.

drum, the hoisting motor M will be idle, the brake-controlling motor C will be idle, the piston p of the impeller pump will be lowered, and

the brake-shoes will be applied to hold the drum on the shaft of the hoisting motor M and hold the load suspended therefrom. In practice, if desired, a. mechanical load-brake may be used to lock the drum against lowering by the load, as well understood in the art.

Oversynchronous lowering.-The switch E is set in the position shown by full lines in Fig. 1. When the controller drum is moved to lowering station I, a circuit for energizing magnet D to close switches d", d, d and open switch 11 will be established as follows: pole f of switch F, conductor is, pole e of switch E, conductors g, 9 switch (1, magnet D conductors g 9 contactor-finger 23, contacts 23, 24 finger 24, and conductor f and pole f Magnet D will close switches d (i a? and connect the stator C of motor C to stator M of motor M through said switches and conductors 0 g and c Resistors R R R will be included through switch E in the circuits of rotor M Rotor M at m is connected toresistor R by conductor 54 and said resistor is connected by conductor 65 to pole e of switch E; and said pole is connected by conductor 66 to resistor R which is connected by conductor 69 to m of rotor M The resistor R is included in a circuit from m on rotor M through conductor 60, resistor R conductor 58, pole e .of switch E, conductor 55, resistor R and conductor 68 to m on rotor M The maximum resistance permitted for this purpose is now included in the circuits for rotor M? to provide safety for lowering. During this lowering of the load at station I the stator M is connected to the line. Pole of switch F is connected through conductor 0, finger 21, contacts 21 26 finger t6 and conductor c to m. m of stator M? is connected to pole of switch F by conductor o finger 23, contacts 23 24 finger 24 and conductor f At m the stator is directly connected by conductor f to pole l of switch F. Fingers 23, engage contacts 23*, 24 to establish a circuit to connect the motor C and the stator M to cause motor C to release the brake. Said circuit will be as follows: m on stator M conductors 0', c switch d conductor 0 m on stator M conductors F, a, switch d conductor 0 m on stator M conductors c 0 switch d conductor The overhauling load rotates the rotor M so the motor operates as an asynchronous generator and develops power back into the main line. The full voltage causes the motor 0 to completely release the brake. The ohmic value of the resistors is such that the lowering speed of the heaviest load is not too high, which would endanger the motor M and, on the other hand,

. is sufiiciently high to allow the load to drop with sufiicient speed for expeditiously handling the loads.

At station I, the resistors provide the highest degree of safety for lowering. As the controller is shifted to succeeding stations, an increase of lowering speed will not occur. The load can be lowered at any desired increase of speed according to the value of the resistance used. The degree of permissible increase depends on the winding of the rotor M and its permissible overspeed.

At lowering

stations

2 and 3, all of the resistors remain connected to the rotor M as occurs at station I, and the brake remains released.

At stations I, 2 and 3, the overhauling load at tains its highest lowering speed. At lowering station 4, a portion of the resistor R is shortcircuited across conductor 55, finger 49, contact 49', contact finger 45, conductors 62, 65 and switch E. At lowering station 5, a portion of the resistor R will be additionally short-circuited across m of rotor M, conductor 50, finger 50, contact contact 45, conductors 62, and switch E. At station 5, a portion of resistor R will be additionally short-circuited from m of rotor M, through conductor 54, 63 finger 5I, contact 5| across to contact 48, conductors 63, and switch E.

At lowering station I, fingers 48, 49, 50, 5|, 52, 53, 54 will engage contacts 48 49 50, 5|", 52 53 54. All of the resistors will be shortcircuited. Resistor R will be short-circuited through conductor 84, finger 54, contacts 54', 52 contactor-finger 52 to conductors G3, 69. Resistor R will be short-circuited through conductor 50, finger 53, contacts 53 52 finger 52 and conductors 53, 59. Resistor R will be shortcircuited through conductors 59, 63, finger 52, contacts 52 53 finger 53 and conductor 50. At station I, thespeed is some per cent. above synchronous,

Lowering with brake-regulation.-Switch E will be set in the position indicated by dotted lines in Fig. 1. In regulated-brake lowering, station I is used for the lowest lowering speed and station 2 for a slightly higher lowering speed.

At lowering station I, fingers 35 and 31 will engage contacts 35 and 31', respectively, for energizing magnet D through a circuit which includes: conductor 1 pole e of switch E, conductor g finger 31, contact 31* across contact 36 to contact 35", finger 35, conductor, a, switch d magnet D conductors g g finger 23, contacts 23*, 24 finger 24, conductor f and pole f Switch a. will then be opened andswitches d, d and d will be closed to connect the stator of motor C to the rotor M through the transformer G.

Theoretically, the rotor voltage and frequency are zero when the motor runs synchronously and when the lifting motor is stalled the rotor has full voltage and frequency. Resultantly, the speed of the motor C is proportional to the speed and consequent variations in frequency in the I, without resistance in the .rotor circuit and withoutmotor torque in the lifting motor, and with some resistance in the rotor circuit andmotor torque in lowering at station 2.

At station I, the low voltage coil 9 of the transformer G is connected through conductors m, m and m to the rotor M of motor M. The resistors are then all out of the circuits of the rotor M Coil g is connected to rotor M through conductors m, 63, 69; W, 60; and m 84, respectively. The stator of motor C is connected to the high voltage coil 9 of the trans former. At lowering station I, the stator M is connected to the line at m directlyconnected to pole i by conductor f finger 24, contacts 24*, 23 finger 23 and conductor c. M is connected to pole f bycon- The stator is tact 35 pole and conductor direct to the terminal m pole f conductor a, finger 21, contacts 21*, 28, finger 28, one pole of limit-switch H, conductor 0 to terminal m pole l conductor I,

finger 24, contacts 24*, 25, finger 25, the other pole of limit-switch H, conductor 0 to terminal W. This will cause the stator M to drive the rotor M At this station the following circuit torque for the regulation of he speed of motor M so that motor C will regulate the release of I the brake and so that the load will be lowered at a very slow speed which is accurately controllable and substantially independent of the weight of the load. This brake-regulation is important for close manipulation of loads such as is necessary in assembly work or in accurately positioning the load with respect to other elements. At station I there is no resistance in the circuit of rotorM. Therefore the torque of motor M is almost zero and the regulatingbrake has to dissipate the energy of the lowering load to minimize wear on the brake-shoes.

When the drum 0 is turned to lowering station 2, the brake-regulation is retained, switches 11', d and at will remain closed, but the lowering of the load will be at a slightly higher speed. Fingers 46, 41, 26, 21, 23, 24 will then engage contacts 46', 41', 26 21 23 24', respectively, and the following circuit will be established to for rotor M will be established to energize magnet D to connect the stator of motor C to the rotor M viz: pole f conductor 1 pole e of switch E, conductor 9 finger 31, contacts 31, 36, 35, finger 35, conductor 9 switch (1, conductor g magnet D conductors 9 g and 0*,

one pole of switch H, finger 25, contacts 25, 24*, finger 24, conductor 1, pole f Switches (1 d (1 will then be closed to connect the stator of motor C through the transformer G and coninclude some resistance in the circuit of rotor slightly greaterspeed than at station I. The

speed increase at this station is dependent on the value of the resistance then included which is selected for the increase desired.

When the drum is rotated to station}, the circuit through magnet D will be interrupted at finger 35 and contact 35 so that said magnet will be deenergized to open switches d d (1 and close swit'ch (2, when finger 35 leaves con- A circuit from finger 31 through contacts 31 36 finger 36, conductors g switch d, magnet D conductors g g finger 23, contacts 23, 24 finger 24 and conductors 1 I will onergize magnet D-, close switches 11", d and d and open switch d and connect the stator C of motor C to stator M for releasing the brake by oversynchronous lowering. All three of the resistors R R ,-R are then included in the circuits of rotor M the same as theyar'e at stations i, 2 and 3 during oversynchronous lowering with switch E in full line position hereinbefore described. At this station the lowering will be efiected at the highest speed desired Between

stations

3 and 1 the control of thelowering of the load will be the same as in oversynchronous lowering at said stations, already described.

Liftino.-Lifting of the load may be selectively effected with or without brake-regulation at the initial lifting station, by means of switch E.

When it is desired to regulate the application of the-brake in lifting loads, switch E is positioned as indicated by dotted lines in Fig. l. Atlifting station I, the stator M of the lifting motor M will be connected to the line as follows:

ductors m, m and m .t0 the rotor M The operation of the impeller pump P will then be controlled responsively to the frequency and voltage in the circuits of rotor M to regulate the releasing of the brake. Resistors R. and R will then be included in the following circuit of rotor M viz: terminal m conductor 69, resistor R conductor 62, finger 46, contacts 46, 41 finger 41, conductor 6|, resistor R and conductor 60 to terminal m The circuit through resistor R will be open at pole e of switch E. The resistance at station I is dimensioned so that light loads will start slowly under brake-regulation. At lifting station 2, the circuit through magnet D will be opened at finger 35 and contact 35 and the following circuit will be established for energizing magnet D viz: conductor pole e of switch E, conductor 9 finger 31, contacts 31 36 finger 36, conductor 9 switch d, magnet D conductors g, g and c one pole of switch H, finger 25, contacts 25, 24 finger 24, conductor 1 pole I. At station 2, the resistors R, R remain in the rotor circuit but the brake is released. At station 3, the resistors R and R remain included in the circuit for rotor M and resistor R is also included and the brake is released. Resistor R is then included in the following circuit: terminal m conductor 64, resistor R conductor 63, finger 48, contacts 48, 41, finger 41, conductor 6|, resistor R. and conductor 60 to terminal in. At station 4, a portion of resistor R is short-circuited across conductor 66, finger 49, contacts 49, 41 and conductor 6|. At lifting station 5, a portion of resistor R will be additionally short-circuited across finger 50, contacts 50, 49, finger 49. At lowering station 6, a part of resistor R is short-circuited across conductor 63 finger 5|, contacts 5|, 5|), finger 50, resistor R At lowering station 1, all of the resistors will be short-circuited. As the resistors are progressively short-circuited, the lifting speed will be gradually increased.

When lifting is to be done without brake-regulation, the switch E will be positioned as shown in full lines in Pig. 1. At lifting station I, a circuit will be established through conductor i pole e of switch E, conductors g, 9 switch d, magnet D conductors g", g and 0 one pole of switch H, finger 25, contacts 25', 24', finger 24, conductor 1, pole i to close switches d", d, d. The resistors R and R will then be included in the circuits for rotor M and the stator of motor C will be connected to the stator M The motor C will release the brake. From lowering stations I to 1 inclusive the resistors are progressively short-circuited as before described with regumagnet- 8 5.

lated brake starting and the lifting speed is gradually increased.

For some work it is desired to normally maintain brake-regulation and to occasionally dispense with it. Fig. 5 illustrates a modification in which the control mechanism normally effects brake-regulation and includes a pedal or pushbutton for temporarily eliminating brake-regulation when desired. In this modification the controlling mechanism includes all of the elements illustrated in Fig. i, such as the drumcontroller and relay D but, in lieu of a switch E, devices are provided for normally maintaining brake-regulation at all times except when the operator holds a switch closed by a pedal or push-button 84. This mechanism comprises a switch 80 operable by an electromagnet 8| and provided with contacts for controlling lines to fingers 36 and 37 which control the circuits for operating magnetslD 13, before described. This mechanism also includes a switch- 82 which is operable by magnet 83 and is connected to the circuits for resistors R R, R as illustrated. Switch-button or pedal 8% is held normally open by a spring 85 and controls switch 80 through Resistors R R, R are connected to the rotor M and contactor-iingers, as illustrated, and are adapted to be progressively shortcircuited, in the same manner as before described, by the controller A during the lifting or lowering of loads. pedal 84 is in its open position, the circuit for operating magnet D to connect the stator of motor to the circuits of rotor M will be maintained closed for brake-regulation in lowering and lifting the loads, as before described. Said circuit will :beas follows: pole j of switch F, conductors f 1 switch 86, conductor g finger 31, contacts 3?, 35, conductor g switch d conductor g", magnet D conductors g g finger 23, conductor one pole of switch H, finger 25,

contacts M finger M, conductor 1, pole 1 In lowering, at stations I and 2 or lifting, at

When the push-button or I the contacts for lifting and, as a result, brakestation i, the brake will be regulated as before described, and at subsequent stations the resistors will be controlled by drum a, as before described. r

When brake-regulation is not momentarily desired, the operator will depress the push-button or pedal 84, which will interrupt the last described circuit at switch by the following circuit, viz: pole f, conductors f f magnet 8|, conductor ,1, push-button or pedal, conductor f" and pole P. The circuit for the operation of magnet D will then be interrupted at switch 80 and a circuit will be established from conductor f through switch 80 and its upper contacts and conductor 9 for operating magnet N, as hereinbefore described, to close switches d", d, d for connecting the stator of motor C to the statorM Simultaneously, current will pass from conductor 1 through magnet 83 to conductor 1 and energize said magnet. This will close switch 82 and close the circuits of the rotor M and connect the resistors R R, R in the rotor circuit for controlling the lifting mechanism, as hereinbefore described, in lifting and lowering.

When, during lifting, the load reaches its high limit, switch H may be opened by any suitable means, as well understood in the art, tointerrupt the current from the line to the stator M regulation may be maintained during a. plurality of stations in lowering and a single station in lifting loads.

Another characteristic is that in regulated lowering no resistance is included at station I and some resistance will be included at station 2, while the brake-motor C is connected to the circuits of rotor M.

The invention is not to be understood as restricted to the details set forth, since these may be modified within the scope of the appended claims, without departing from the spirit and scope of the invention.

Having thus described the invention, what I ent is:

1. In a control system for hoisting mechanism,

the combination of a power-supply line, an electric induction hoisting motor comprising a stator and a rotor subject to an overhauling load, a brake normally applied to the hoisting motor, an electric motor for releasing'the'brake, hydraulic brake-releasing means responsive to the speed of the brake-releasing motor for regulating the release of the brake, resistors for varying the speed of the hoisting motor, a controller comprising switches at a series of stations for establishing circuits for controlling the operation and speed of the hoisting motor, means responsive to the controller at one lowering station for connecting the stator of the hoisting motor to the power-supply line, means responsive to the controller at the same station for operating the hoisting motor as a frequency and voltage converter when its rotor is driven by an overhauling load, and electromagnetic switch means responsive to the controller at the same station for connecting the brake-motor to the rotor of the hoisting-motor for the operation of the brakeand voltage produced by the overhauling load,

for regulating the release of the brake.

2. In a control system for hoisting mechanism, the combination of a power-supply line, an electric induction hoisting motor comprising a stator and a rotor subject to an overhauling load, a brake normally applied to the hoisting-motor, an electric motor for releasing the brake, hydraulic brake-releasing means responsive to the speed of the brake-releasing motor for regulating the release of the brake, resistors for varying the speed of the hoisting-motor, a controller comprising switches at a series of stations for establishing circuits for controlling the operation and speed of the hoisting'motor, means responsive to the controller at one lowering station for connecting the stator of the hoisting-motor to the power-supply line, means responsive to the controller at the same station for operating the hoisting-motor as a frequency and voltage converter when its rotor is driven by an overhauling load, electromagnetic switch means responsive to the controller at the same station for connecting .the brake-motor to the rotor of the hoisting motor for the operation of the brake-motor at a speed responsive to the frequency and voltage produced by the overhauling load for regulating the release of the brake, and means responsive to the controller at the same station for selectively establishing circuits for operating the hoisting-motor as an asynchronous generator and connecting the brake-motor to the stator of the hoisting motor for over-synchronous lowering of loads.

3. In a control system for hoisting mechanism, the combination of a power-supply line, an electric induction hoisting-motor comprising a stator and a rotor subject to an overhauling load, a brake normally applied to the hoisting-motor, an electric motor for releasing the brake, hydraulic brake-releasing means responsive to the speed of the brake-releasing motor for regulating the release of the brake, resistors for varying the speed of the hoisting-motor, a controller comprising switches at a series of stations for establishing circuits for controlling the operation and speed of the hoisting-motor, means responsive to the controller at one lowering station for connecting the stator of the hoisting-motor to the powersupply line, means responsive to the controller at the same station for operating the hoistingmotor as a frequency and voltage converter when its rotor is driven by an overhauling load, electromagnetic switch means responsive to the controller at the same station for connecting the brake-motor to the rotor of the hoisting-motor for the operation of the brake-motor at a speed responsive to the frequency and voltage produced by the overhauling load for regulating the release of the brake, and means for including re-- sistance in the circuit of said rotor responsively to the controller at the second lowering station for increasing the speed of the brake-motor for an increase of the lowering speed of the overhauling load.

4. In a control system for hoisting mechanism, the combination of a power-supply line, an electric induction hoisting motor comprising a stator and a rotor subject to an overhauling load, a brake normally applied to the hoisting motor, an electric motor for releasing the brake, hydraulic brake-releasing means responsive to the speed of the brake-releasing motor for regulating the release of the brake, resistors for varying the speed of the hoisting-motor, a controller comprising switches at a series of stations for establishing circuits for controlling the operation and speed of the hoisting-motor, means responsive to the controller at one lowering station for connecting the stator of the hoisting motor to the power-supply line, means responsive to the controller at the same station for operating the hoisting-motor as a frequency and voltage converter when its rotor is driven by an overhauling load, electromagnetic switch means responsive to the controller at the same station for connecting the brake-motor to the rotor of the hoistingmotor for the operation of the brake-motor at a speed responsive to the frequency and voltage produced by the overhauling load for regulating the release of the brake, means for including resistance in the circuit of said rotor responsively to the controHeI at the second lowering station for increasing the speed of the brake-motor for an increase of the lowering speed of the overhauling load, and means responsive to the controller at the third lowering station for including additional resistance in the circuit of said rotor and establishing circuits for operating the hoisting-motor as an asynchronous generator and operating the brake-motor to release the brake for over-synchronous lowering of the loads,

5. In a control system for hoisting-mechanism, the combination of a power-supply line, an electric induction hoistingmotor comprising a stator and a rotor subject to an overhauling load, a brake normally applied to the hoisting-motor, an electric motor for releasing the brake, hydraulic brake-releasing means responsive to the speed of the brake-releasing motor for regulating the release of the brake, resistors for varying the speed of the hoisting-motor, a controller comprising switches at a series of stations for establishing circuits for controlling the operation and speed of the hoisting-motor, means responsive to the controller at the first lifting station for connecting the stator of the hoisting-motor to the power-supply line for the operation of the rotor, electromagnetic means responsive to the controller at the same station for connecting the rotor to the brake-releasing motor for the operation of the brake-motor responsively to the frequency and voltage in the rotor circuit, and electromagnetic switch-means responsive to the controller at the second lifting station for connecting the brake-motor to the stator of the hoisting motor for the release of the brake.

6. In a control system for hoisting mechanism, the combination of a power-supply line, an electric induction hoisting-motor comprising a stator and a rotor subject to an overhauling load, a brake normally applied to the hoisting-motor, an electric motor for releasing the brake, hydraulic brake-releasing means responsive to the speed of the brake-releasing motor for regulating the release of the brake, resistors for varying the speed of the hoisting motor, a controller comprising switches at a series of stations for establishing circuits for controlling the operation and speed of the hoisting-motor, means responsive to the controller at the first lifting station for connecting the stator of the hoisting-motor to the power supply-line for the operation of the rotor, electromagnetic means responsive to the controller at the same station for connecting the rotor to the brake-releasing motor responsively to the frequency and voltage in the rotor circuit, electromagnetic switch-means responsive to the controller at the second lifting station for connecting the brake-releasing motor to the stator of the hoisting-motor for the release of the brake, and means for selectively establishing circuits for operating the hoisting-motor as an asynchronous generator and connecting the brake-motor to the stator of the hoisting motor for over-synchronous lowering of loads, when the controller is at the first lifting station.

7. In a control system for hoisting mechanism, the combination of a power-supply line, an electric induction hoisting motor comprising a stator and a rotor subject to an overhauling load, a brake normally applied to the hoisting-motor, an electric motor for releasing the brake, hydraulic mechanism responsive to the speed of the brake-releasing motor for regulating the release of the brake, resistors for varying the speed of the hoisting motor, a controller comprising switches at a series of lowering and lifting stations for establishing circuits for controlling the operation and speed of the hoistingmotor, means responsive to the controller at the first lowering station for connecting the stator of the hoisting-motor to the power-supply line, means responsive to the controller at the first lowering station for operating the hoisting-motor as a frequency and voltage converter when its rotor is driven by an overhauling load, electromagnetic switch-means responsive to the controller at the first lowering station for connecting the brake-motor to the rotor of the hoisting-motor for the operation of the brakemotor at a speed responsive to the frequency and voltage produced by the overhauling load for regulating the release of the brake, means responsive to the controller at the first lifting station for connecting the stator of the hoistingmotor to the power-supply line for the operation of the rotor, electromagnetic means responsive to the controller at the same station for connecting the rotor to the brake-releasing means for the operation of the brake-motor responsively to the frequency and voltage in the rotor circuit, and means for selectively establishing circuits for operating the hoisting-motor as an asynchronous generator and connecting the brake-motor to the stator of the hoisting-motor for over-synchronous lowering of loads when the controller is at the first lifting and the first lowering station.

8. In a control system for hoisting mechanism, the combination -oi a power-supply line, an electric induction hoisting motor comprising a stator and a rotor subject to an overhauling load, a brake normally applied to the hoisting-motor, an electric motor for releasing the brake, hydraulic mechanism responsive to the speed of the brake-releasing motor for regulating the release of the brake, resistors for varyingthe speed of the hoisting-motor, a controller comprising switches at a series of lowering and lifting stations for establishing circuits for controlling the operation and speed of the hoisting motor, means responsive to the controller at the first lowering station for connecting the stator of the hoisting-motor to the power-supply line, means responsive to the controller at the first lowering station for operating the hoistingmotor as a frequency and voltage converter when its rotor is driven by an overhauling load, electromagnetic switch-means responsive to the controller at the first lowering station for con meeting the brake-motor to the rotor of the hoisting-motor for the operation of the brakemotor at a speed responsive to the frequency and voltage produced by the overhauling load for regulating the release of the brake, means responsive to the controller at the first lifting stationfor connecting the stator of the hoistlug-motor to the power-supply line for the operation of the rotor, and electromagnetic means responsive to the controller at the first lifting station for connecting the rotor to the brakereleasing means for the operation of the brakemotor responsively to the frequency and voltage in the rotor circuit.

9. In a. control system for hoisting-mechanism, the combination of a power-supply line,

an electric induction hoisting-motor comprising a stator and a rotor subject to an overhauling load, a brake normally applied to the hoisting motor, an electric motor for releasing the brake, hydraulic mechanism responsive to the speed of the hrake-releasing motor for readlating the release of the brake, resistors for varying the speed of the hoisting-motor, a-controller comprising switches at a series of lowering and lifting stations for establishing circuits for controlling the operation and speed of the hoisting-motor, means responsive to the controller at the first lowering station for connect ing the stator of the hoisting-motor to the powerupply line, means responsive to the con troller at the first lowering station for operating the hoistingmotor as a frequency and voltage converter when its rotor is driven by an overhauling load, electromagnetic switch means responsive to the controller at the first lowering station for connecting the brake-motor to the rotor of the hoisting-motor for the operation of the brake-motor at a speed responsive to the frequency and voltage produced by the overhauling load for regulating the release of the brake. means for including resistance in the circuit of said rotor responsively to the controller at the second lowering station for increasing the speed of the brake-motor for an increase of the lowering speed of the overhauling load, means responsive to the controller at the third lowering station for including additional resistance in the circuit of said rotor and establishing circults for operating the hoisting-motor as an asynchronous generator, and operating the brake-motor to release the brake for over-syn.- chronous lowering of the loads, means responsive to the controller at the-first lifting station for connecting the stator of the hoisting-motor to the power-supply line for the operation of the rotor, electromagnetic means responsive to the controller at the same station for connecting the rotor to the brake-releasing means for the operation of the brake-motor rcsponsively to the frequency and voltage in the rotor circuit, and electromagnetic switch-means responsive to the controller at the second lifting station for connecting the brake-motor to the stator of I the hoisting-motor for the release of the brake.

10. In a control system for hoisting mechanism, the combination of a power-supply line, an electric induction hoisting-motor comprising a statorand a rotor subject to an overhauling load, a brake normally applied to the hoistingmotor, an electric motor for releasing the brake, hydraulic mechanism responsive to the speed of the brake-releasing motor for regulating the release of the brake, resistors for varying the speed of 'the hoisting-motor, a controller com.- prising switches at a series of lowering and lifting stations for establishing circuits for controlling the operation and speed of the hoistingrnotor, means responsive to the controller at the first lowering station for connecting the stator of the hoisting-motor to the power-supply line, means responsive to the controller at the first lowering station for operating the hoistingmotor as a frequency and voltage converter when its rotor is driven by an overhauling load, electromagnetic switch-means responsive to the controller at the first lowering station for connecting the brake-motor to the rotor of the hoisting-motor for the operationcf the brakemotor at a speed responsive to the frequency and voltage produced by the overhauling load for regulating the release of the brake, means for includ ng resistance in the circuit of said rotor responsively to the controller at the sec-=- ond lowering station for increasing the speed of the brake-motor for an increase of the lowering speed of the overhauling load, means responsive to the controller at the third lowering station for including additional resistance in the circuit of said rotor and establishing circuits for operating the hoisting-motor as an asynchronous generator, and operating the 'brakeunotor to release the brake rm: over-synchronous lowering of the loads, means respon= sive to the controller at the first lifting station for connecting the stator of the hcistingunotor to the power-supply line for the operation of the rotor, electromagnetic means responsive to the controller at the same station for corn necting the rotor to the brake-regulating means for the operation of the brake-motor responsively to the frequency and voltage in the rotor circuit, electromagnetic switch-means responas an asynchronous generator and connecting sive to the controller at the second lifting sta- U the brake-motor to the stator 01 the hoistingtion for connecting the brake-motor to the -motor for over-synchronous lowering of loads stator of the hoisting-motor for the release of when the controller is at the first lifting and the the brake, and means for selectively establish- 5 first lowering station.

ing circuits for operating the hoisting-motor ERNST L. SCHWARZ.