US2493005A - Electric winch control system - Google Patents

Description

Jan. 3, 1950 K. MAHNKE ET AL. 2,493,005

ELECTRIC WINCH CONTROL SYSTEM Filed Nov. 29, 1947 Hoist 19 fi Lair g Q '-O WITNESSES: INVENTORS I a Kari- Mahnke and Z M Bari B.Hnkenman.

z w. 1 A, r a,

ATTRNEY Patented Jan. 3, 1950 UNITED STATES PATENT OFFICE ELECTRIC WINCH CONTROL SYSTEM! Kurt Mahnke, Pittsburgh, Pa.,

and. Earl 13..

ApplicationNovember 29, 1947-, Serial No; 788,950

8 Claims. 1 Our inventionrelates to electric systems for controlling winches and, in particular, to control systems for operating the cargo winch booms of boom topping winches.

t is an object of our invention to devise a control system which permits the operator to raise and lower the boom merely by actuating the electric master control means, i. e., without necessitating the additional" manipulation of a warping-drum handline, and which secures, under all operating conditions, a positive and reliable setting and release 'of the winch pawl without danger.

of shocks or overstress. Another object of the invention, in conjunction with. the foregoing, is to safeguard the controlsystem from causing pumping; movements: due to motor-stalling load conditions.

According to one feature of our invention, we provide an electric control system which, when set for lowering the boom, produces a limited hoisting motion; in order to release the ratchet pawl of the winch. before the lowering motion is started, and we equip this system with timing means which delay the setting of thepawl after lowering operations and. first apply braking means which retard or stop the motor before the pawl is permitted to set.

According to still another feature of the invention, We equip the control system with an. overload relay and provide the. latter with a loclc-out coil which, when the relay has responded to overloadand has disconnected. the motor from its energizing circuit, prevents the relay from falling out as long. as the master control means are held in run position. and thus prevents. pumping which may otherwise occur under excessive, motor-stalling overload conditions.

These and other objects and features will be apparent from. the following description of the embodiment of. our invention exemplified in the drawing, in which:

Figure 1 shows a circuit diagram of an: electric control system for a boom topping winch; while Fig. 2 shows'schematica-lly the design principles of one of thecontactors appertaining'to the same system.

In Fig. l the-boom. structure of the winch is schematically illustrated at A. The structure has a tiltable winch boom i. The boom cablezis operated by a winch drum 2. The drum is equipped with locking means which comprise a ratchet gear 3 engageableby a ratchet pawl 4. The pawl must be released; from. gear. 3' in order to permit lowering of the boom. 1.

The winch drum 2' is r further equipped with a spring-set friction brake 5. Theappertaining magnetic control coil 6 must be energized in order to release the brake 5;

Thewinchdrum. Zis connected. to the armature l of a winchmotor M. by a mechanical transmission', here schematically represented. by a broken line 8. The motor M has a shunt field winding 9. and a mainfield winding Ht. Winding I0 is series connected with the armature 1 during hoisting operation and. shunt-connected. duringlowering operatiomaswillbe explained. more in detail in alater place.

The motor and. the electric auxiliaries of the appertaining control. system are energized from direct current mains H- and I2. through a main switch [-3. The energization oi. the motor is con-- trolled by a hoisting contactor H and by a lowering contactor Lof which. only one is in. pickedup condition at a: time. The coil I4 of contactor I-I controls four contactsdenoted by 15 through l8, and is connected across'mains H and 2in series with a normally open contact t9. Contact l9 forms part of the master control means of the system. Contactor H hasa lock-out coil 2 0 which is connected across the motor armature 'i'. The lock-out coil 20, even it energized, is ineffective after contactor H is picked up by coil l4. Coil 23 comes into effect only when it is sufiiciently energized after contactor H has dropped out.

action, the contactor in its actual: design, may

have an armature of the type denoted by H in Fig. 2. When the main coil l4, according to Fig. 2, is energized, it moves armature H" and closes contact l5 while opening contact I 6. As a result, the air gap at coil 20 becomes so large that the subsequent energization of coil' 20 has no effect on the armature. However, when thereafter coil I4 is deenergized and armature H dropped back into the illustrated position, the energization of coil 20 holds contact l6 safely closed and locks the contactor in the dropped-off position. The lowering relay L has a control coil 21 for'actuating two'contacts 22 and2-3; 00112! is energized under control by a normally open contact 2d" which forms also part of the abovementioned master control means. The circuit of coil 2'! includes a pawl limit switch 25 of a ratchet control assembly S which has another limit switch 25 Assembly S serves to release 3 the ratchet pawl 4 and is actuated by a solenoid 26.

The system is further equipped with an overload relay whose contact 21 is controlled by an overload responsive control coil 21 disposed in the energizing circuit connections of the motor armature I. Overload relay 0 has a lock-out coil 28 connected in parallel to the control coil M of hoist relay H. Coil 28 prevents relay 0, when the latter is picked up, from dropping out as long as contact I!) is held closed by the operator.

The energizing circuit connections for motor M are controlled by a main contactor C whose control coil 29 actuates five contacts denoted by 30 through 34. The main contactor C has a lock-out coil connected in parallel to the lockout coil 20 of hoist contactor H across the motor armature l. Coil 35 is ineffective relative to the movable armature structure of contactor C as long as the coil 29 is energized and holds the contactor in picked-up position. However, when the lock-out coil 35 is sufficiently energized while the contactor C is dropped off, it secures a sufficient contact pressure at contact 30 and prevents the coil 29 from moving the armature as" sembly. In this respect, the design and function of the double-coil contactor C is similar to the contactor H as explained above with reference to Fig. 2.

A timing relay T, which forms also part of the control system has a main control coil 36, a neutralizing coil 31 and two contacts 38 and 39. A short-circuited winding 40 in relay T provides the desired delay of the dropping out performance, and the delay period is also dependent upon the degreeof excitation of the neutralizing coil 31.

Numerals 4| through denote resistors. Resistor 43 is a starting resistor and serves to secure a desired acceleration of motor M. Resistor 44 permits adjusting the excitation of the neutralizing coil 31 in timing relay T and is connected with fixed resistor 45. Another resistor 46 is series connected with the brake release coil 6.

While the contacts l9 and 24, for the sake of convenience, are represented as pushbutton switches, it should be understood that these contacts may form part of a drum type master controller which is spring-biased to normally remain in the off position and can be held by the operator, against the spring bias, in either the hoist or the lowering position. Details of such a master controller or of other applicable types of master control means are not illustrated because their particular design is not essential to the invention proper, and the intended functions can be satisfactorily performed with the aid of the illustrated pushbutton contacts.

The system operates in the following manner:

As long as main switch 13 is open, the hoist motor and all other elements of the system are deenergized, brake 5 is set to prevent drum 2 from revolving, and the drum is also locked by the ratchet pawl 4. In order to start the system, the operator closes main switch I 3 and then closes contact ill or 24, depending upon whether the winch boom is to be hoisted or lowered. The selected contact must be held closed as long as the hoisting or lowering performance is to continue, and the release of the contact has the.

effect of stopping the winch and resetting the system into deenergized and locked position.

More in detail, a hoisting performance involves the following operations. The closing of contact I9 has the effect of energizing coil M of hoisting 4 contactor H, lock-out coil 28 of overload relay 0, and main coil 36 of timing relay T. Contactor H and relay T pick up. Contact is of contactor H and contact 39 of relay T close and energize coil 2c of main contactor C in the circuit so that contactor C picks up. Contact 39 of relay T also energizes the solenoid 26 in the circuit The neutralizing @011 Ill of timing relay T is also energized through contact 39 in the circuit Contacts Eli and 32 of main contactor C connect the motor M to the energizing mains, with resistor series-connected to motor armature 7, in the circuit This energizing circuit includes the motor field Winding H3 in series connection with the armature '5 so that the motor operates with a series characteristic. The interlock contact 34 of the main contactor C bypasses the contact 39 of timing relay T and thus establishes for coil 29 of contactor C the holding circuit Contact 33 of contactor C energizes the coil 6 so that brake 5 is released. Solenoid 26 actuates the assembly S thus closing limit switch 25 while opening limit switch 25 and releasing the pawl 4 from the drum ratchet 3. Consequently, the motor M now operates the winch drum 2 for lifting the boom l. The limit switch 25' of assembly S opens the circuit of main coil 35 in timing relay T. Consequently, after a timed delay, relay T drops out and, at contact 38, connects the motor M to full line voltage in the circuit The desired accelerating period for motor M can be adjusted by displacing the sliding tap of resistor 44.

The motor stops when the operator releases contact IQ of the master switch. This causes all energized contactors to trip with the effect of resetting the system.

It will be recognized from the foregoing that the resistor 43 is inserted in the motor circuit only during the accelerating period, and that the illustrated example of a system according to our invention operates with only one accelerating step for the motor. If desired, however, two or more accelerating resistors and corresponding accelerating steps may be provided in accordance with Well known practice and depending upon the requirements and desiderata of each particular application. The provision of more than one accelerating step requires, of course, the addition of one or more timing relays for securing the desired sequence of accelerating performance.

In order to lower the boom, the contact 24 is held by the operator in closed position. The closing of contact 24 causes the hoisting contactor H to pick up because its coil 14 is now energized in the circuit Lock-out coil 28 of relay 0 and main coil 35 of timing relay T are also energized in parallel connection to coil E4 of contactor H.

meteor 5 Timing relay T picks up and, at contact -39, energizes for coil 29 of contactor C, the abovementioned circuit (1 so that =contaotor 0 picks up. Contact 39 also closes the above-menti'o'ne'd circuit 2) for the solenoid coil 26 and the circuit (-3) of the neutralizing *coil 4-! in til-hing relay T.

Con'tactor "C now connects the motor M to the energizing mains by establishing the abovementioned circuit (4'). Consequently, although the master control means are set for lowering operation, the motor M is the first started in the hoisting direction with resistor 43 connected in series with the motor armature. The holding contact 34 in the -above-mentioned circuit (5) maintains the contactor -'C in picked-up condition, and contact 33*energizes coil 6 to release the brake 5. The solenoid 26 releases the pawl 4, but the pawl limit switch 25' then *deene'rgizes coil 14 of hoist contactor H, as well 'as the look-out coil 28 of relay "0. Conta'ctcr l-I drops out, and the i pawl limit switch '25 now energizes coil 2| of the lowering contactor L in the circuit The timing relay T remains energized through i the contact.

During the just-mentioned automatic transfer "from hoist contactor H to lowering cbntactor 'L, the main Contact 0 may momentarily drop out due to the switching-over of its coil circuit from i The motor is stopped by permitting the contact '24 to return to its on position.

The motor field winding 9 is shunt-connected to the armature during hoisting as well as during lowering performance. It serves mainly 'as a speed limiting winding and may beomitted with out otherwise affecting the operation of the system.

In order to prevent the pawl 4 from suddenly;--

dropping into the ratchet gear 3 at the end :of .a lowering operation, the solenoid 255 of the assembly S is kept energized for a short additional interval of time by contact 39 of timing relay 'I,

The .en'erbecause relay T does not drop out immediatelydifl when being deenergized by the control contacts 24. The other contactors, however, drop out immediately and establish through armature I, resistor 44, and series field winding I0, the dynamic braking :circuit.

This braking circuit as well as the friction brake 5 are efiective during the timing interval to stop the motor M before the pawl 4 is permitted to If during a hoisting performance an overload occurs, the coil 2 1 of relay '0 is sufiiciently energized to open the contact :21. This has the effect of opening the coil =circuit -('1) of contactor C. As a result, the brake-coil 6 isdeenergized at contact :33, and the solenoid 26 is dee'nergized so that the brake is set and the pawl moved into locking engagement. However, in order to avoid the occurrence of pumping action under motor-stallihg overloads, the relay 0 is held picked up by the look-out coil 28 until the master contact 19 is released. "This performance of lock-out coil 28 will be understood from the following:

When moderate overloads occur during the accelerating periods of the motor, while the motor is permitted to reach some speed and su'flicient time is available for the accelerating relay T to drop out, no pumping effect can occur because the seal-in contact 34 of contactor C and the auxiliary contact 39 of relay T are then open. Consequently, when such moderate overloads cause tripping of the relay 0, the contactor C is prevented from coming in again since the r'eclo'sing of :contact 21 in relay '0 does not complete an energizing circuit for coil 29 of contactor C. If the overload relay 0 is set to pick up ata-n overload value above the initial starting peak that occurs during the "normal acceleration of motor the overload relay "0 will not trip the cont'actor C even under stalled motor conditions before the end of the accelerating interval determined by the timing relay T. In order to obtain optimum operating conditions andfsatisfactory overload protection, however, the last-mentioned setting or the overload relay '0 is not recommendable. The overload relay 0 should be set to respond to a current value a little below the initial stalled current, i. e., the maximum current that may flow through the motor circuit under normal starting conditions before the starting 'resistorf43 has been shorted. There is a small delay or a fraction of a second in the action of the overload relay so that normally the starting peak current is reduced to below the setting of the relay if the motor accelerates. Hence, under normal conditions, the overload relay will not respond despite the fact that it is set for a current slightly below the initial stalled current. However, if the conditions are such that the motor is stalled during the accelerating period,

then the relay 0 will respond and the conditions of the other relays in the system are then such that the overload relay and the contactor C may pick up and drop out alternately thus causing the above-mentioned undesirable pumping. Due to the look-out action or vcoil 28., however, this possibiility of pumping under excessive overloads is safely prevented and it is .necessary to first release the master contact 19 before .a new attempt of starting themotor -is permitted.

During lowering performance, the decreased motor torque as well as the resistors in the motor energizing connections prevent the occurrence of excessive currents so that contact M of relay 0 will not open. v It will .be understood from the foregoing by those skilled in the art that control systems according to the invention may be altered and modified as regards various circuit elements and interconnections and may be embodied by designs other than that specifically illustrated and described, without departing from the essence and features of the invention and within the scope of the claims annexed hereto.

We claim as our invention:

1. A winch control system, comprising winch locking means disposed for preventing lowering operation when set and having an electromagnetic releasing coil and limit switch means, a reversible winch motor, an energizing circuit for said motor, a hoist contactor for controlling said circuit to energize said motor for hoisting, a lowering contactor for controlling said circuit to energize said motor for lowering, master control means having selectively actuable first and second contacts respectively, said first contact being connected with said hoist contactor to render the latter operative when said first contact is actuated, a timing relay having contact means connected with said contactors and having a control coil connected with said second contact and said releasing coil and said limit switch means so that, when said control coil is energized through said second contact, said hoist contactor is tem porarily operated for an interval timed by said timing relay before said lowering contactor is operated.

2. A winch control system, comprising winch locking means disposed for preventing lowering operation when set and having an electromagnetic releasing coil, a reversible winch motor, control means for said motor having a hoist contactor and a lowering contactor for energizing, when operative, said motor to run in hoisting and lowering directions respectively, said control means including two selectively actuable control contacts, one of said control contacts being connected to said hoist contactor for causing the latter to operate, a timing relay having a coil connected with said other control contact and having relay contacts connected with said two contactors so as to temporarily operate said hoist contactor and thereafter operate said lowering contactor when said other contact is actuated, and circuit means forming part of said control means and being connected to said releasing coil for releasing said locking means when either contactor is operative, said circuit means including a contact controlled by said timing relay so that, due to said latter contact, said locking means stays released during the change from operation of said hoist contactor to operation of said lowering contactor.

3. A winch control system, comprising winch locking means disposed for preventing lowering operation when set and having an electromagnetic releasing coil, a reversible winch motor having an armature and a field winding, energizing mains, control means disposed for connecting said motor to said mains and including a hoist contactor connecting, when operative, said armature and said field winding in series relation to each other across said mains for hoisting performance of said motor, said control means including a lowering contactor connecting, when operative, said armature and said field winding in parallel relation across said mains for lowering performance of said motor, said control means including selectively actuable control contacts, one of said control contacts being connected to said hoist contactor for causing the latter to operate, and timing means associated with another one of said control contacts and with said two contactors so as to temporarily operate said hoist contactor and thereafter operate said lowering contactor when said other contact is actuated, said control means being connected with said releasing coil for releasing said locking means when either contactor is operative.

4. A winch control system, comprising winch locking means disposed for preventing lowering operation when set and having an electromagnetic releasing coil, a reversible winch motor, energizing circuit means for said motor, first control means disposed to connect, when actuated, said motor to said circuit means for hoisting, second control means disposed to connect, when actuated, said motor to said circuit means for lowering, winch braking means controlled by said second control means to brake said motor after actuation of said second control means, a timing relay controlled by said second control means and connected with said releasing coil for energizing the latter during actuation of said second control means and during an additional interval after said actuation of said second control means to secure braking of said motor before permitting said locking means to set.

5, A winch control system, comprising winch locking means disposed for preventing lowering operation when set and having an electromagnetic releasing coil, a reversible winch motor, energizing circuit means for said motor, first control-means disposed to connect, when actuated, said motor to said circuit means for hoisting, second control means disposed to connect, when actuated, said motor to said circuit means for lowering, a timing relay controlled by said second control means to be picked up during actuation oisaid second control means and during an additonal timed interval, said timing relay being connected with said releasing coil so as to maintain said locking means released during the pickup period of said timing relay, and a dynamic braking resistor controlled by said first control means and said second control means to be ef fective across said motor only when said two control means are unactuated so that said motor is braked by said resistor during said additional interval before said timing relay permits said locking means to set.

6. A winch control system, comprising winch locking means disposed for preventing lowering operation when set and having an electromagnetic releasing coil, a reversible winch motor, energizing circuit means for said motor, selectively operable control means for connecting said motor to said circuit means for operation in hoisting and lowering directions respectively, said control means having a contact movable between ofi and on positions for operating said motor in hoisting direction when in said on position, a timing relay having a coil connected to said contact so as to pick up when said contact is moved to said on position and drop out upon elapse of a timing period after said contact is returned to said on position, braking means associated with said motor and controlled by said control means to brake said motor when said contact is moved from said on position to said off position, said releasing coil being connected to said control means and to said timing relay so as to be energized for releasing said locking means when said contact is moved to said on position and deenergized after elapse of said timing period to then permit said braking means to set, a load relay having a coil connected with said circuit means so as to pick-up when the motor energizing current exceeds a limit value and having a lock-out means for preventing said picked-up relay from dropping out as long as said contact is in said on position, said load relay having contact means electrically associated with said control means, and said timing relay for causing said mo- 5 tor to be braked and locked when said load relay is in picked up condition.

'7. A control system for a winch with locking means for preventing lowering operation when set and an electromagnetic release coil for releasing said locking means, comprising a reversible winch motor, power supply leads, a hoist contactor and a lowering contactor of substantially immediate pick-up and drop-out performance, said contactors having respective contactor coils and having main contacts connecting said motor to said leads for hoisting and lowering respectively when said respective contactors are picked up, control means having two selectively actuable control contacts of which one is connected with said hoist contactor coil, a timing relay of delayed drop-out performance having a relay contact and a relay coil, limit switch means actuable by the release coil and movable between first and second positions corresponding to the set and released conditions respectively of the locking means, an energizing circuit controlled by said other control contact and being connected through said limit switch means with said hoist contactor coil and with said relay coil when said limit switch means is in said first position and with said lowering contactor coil when said limit switch means is in said second position, and a circuit for energizing said release coil having contact means connected with said respective contactors and being connected with said relay contact for releasing the winch locking means when any one of said contactors and relay is picked up.

8. A control system for a winch with locking means for preventing lowering when set and an electromagnetic release coil for releasing said locking means, comprising a reversible winch motor, a power circuit connected to said motor, a hoist contactor and a lowering contactor for controlling said circuit to run said motor in hoisting and lowering directions respectively, a timing relay of delayed drop-out having a relay contact and a relay coil, an energizing circuit for the release coil connected with said relay contact to release the locking means when said timing relay is picked up, switch means controllable by said release coil and movable between a first position and a second position corresponding to the set and released conditions respectively of the looking means, operator-actuable control means having two selectively operable control contacts, one of said control contacts being connected with said hoist contactor and being also connected through said switch means with said timing relay for causing said timing relay to temporarily pick up when said motor starts running in the hoisting direction, a resistor connected in said power circuit and connected with said hoist contactor and said relay to be controlled thereby to be effective in said power circuit only when said hoist contactor and relay are both picked up, said other control contact being connected through said switch means with said hoist contactor in said first position of said switch means only and being connected through said switch means with said lowering contactor in said second position only, and said other control contact being also connected with said timing relay for causing it to remain picked up until after the actuation of said other control contact.

KURT MAHNKE. EARL B. ANKENMAN.

REFERENCES CITED UNITED STATES PATENTS Name Date Cutler Apr. 22, 1902 Number

Images