US2467726A - Electric winch - Google Patents

Description

April 19, 1949. s. A. BOBE 2,467,726

- ELECTRIC WINCH Filed July 7, 1944 2 Sheets-Sheet l WITNESSES: INVENTOR MW Sfflfl/g/ 14. 5012 6.

W WYW ATTORNEY April 19, 1949. s. A. BOBE ELECTRIC WINCH 2 Sheets-Sheet 2 Filed July 7, 1944 INVENTOR 5700/5 A Babe.

WITNESSES! m rrm BY ma, M

ATTORNEY Patented Apr. 19, 1949 ELECTRIC WINCH Stanley A. Bobe, Atlanta, Ga., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 7, 1944, Serial No. 543,799

3 Claims. 1

My invention relates to electric winch drives, and particularly to an energizin and control system for towing winches.

It has been customary to provide the electric control system of towing winches with a tensiometric device for protecting the winch cable from excessive pull or tension. The known tensiometric devices of this type contain a movable contact member which is spring biased toward a given contact position and connected with the winch drum and the driving motor by means of a planetary gear. The winch motor is normally deenergized and a friction brake set for. operation. As long as the cable pull stays within a given limit, the load is taken up by the brake. When the pull increases to such an extent as to overcome the brake friction and the biasing force of the tensiometer spring, a contact is closed by the movable tensiometer member which causes the brake to be lifted and the motor to be energized so as to pay out or reclaim the cable whichever is necessary to correct the pull and torque conditions.

Tensiometric devices of the mechanical type :just described are usually adjusted to a single value of maximum cable pull or drum torque,

:and do not lend themselves readily for an adjustment by the operator over an appreciable range of control. They represent also a complication of the equipment and are apt to introduce additional frictional losses and other sources of possible failure.

It is an object of my invention to provide an electric control system for winches with tension measuring or tension responsive means which permit an adjustment of the obtainable maximum cable pull or tension over a considerably wider range than afforded by the known mechanical devices.

Another object of the invention is to afford the just mentioned adjustability during a winch operation that is, without requiring an interruption of the towing performance.

Still another object of the invention aims at eliminating the mechanical tension measuring devices and providing instead electrical means for protectin the cable from exceeding a safe maximum value of cable tension.

It is also an object to integrate tension setting and indicating means with the energizing control system of a winch motor so that a single control system performs the control functions required for operating the which as well as a measurement, indication and protective limitation of the pull or tension to which the winch cable may be subjected.

In order to achieve these ends and in accordance with an essential feature of my invention, I provide a winch drive with a motor control system in which a current or resistance magnitude of the motor control circuit is representative of the maximum or standstill torque of the motor and which is provided with exhibiting means for indicating this magnitude as a measure of the maximum cable tension. The essential circuit elements of this system are so designed or rated that the highest obtainable driving torque of the motor stays within such limits, relative to the oppositely acting drum torque caused by the cable pull, that the tension developed in the cable remains always below its safe limit. When speaking of a winch cable in this specification, I include in this term any other flexible elements such as ropes or chains applicable in connection with a drum drive in systems of the type here of interest.

According to another feature of my invention, a winch drive is equipped with an electric direct-current motor energized from a generator whose output voltage is varied by means of a variable field excitation, and this excitation is under control by rheostat means which are adjustable by the operator. The adjustment of the rheostat means is exhibited to the operator by indicating means preferably calibrated in terms of cable tension or representative thereof.

The foregoin and other objects and features of my invention will become apparent from the following description of the embodiment shown in the drawings, in which Figure 1 represents a circuit diagram of a winch control system in accordance with the invention, while the diagrams in Figs. 2, 3, and 4 exemplify operating characteristics relating to the same system.

Referring to Fig. 1, the armature of the winch motor WM is denoted by l and the appertaining field windin by 2. The armature I is connected by its shaft 3 to a gearbox 4 containing a speedreduction gear whose output shaft 5 is connected with the hawser or winch drum 6. A brake B is provided for retarding and stopping the Winch drum. The brake is spring operated and electrically releasable by means of a magnet coil 1. The winch drum 6 is provided with a ratchet gear for engagement by a stop pawl 8 serving to block the drum when the winch is not in operation. The pawl 8 is provided with a contact 9 which is closed only when the pawl is disengaged from the ratchet gear of drum 6.

The gear box 4 is provided with a traveling nut which causes a cam to travel in one or the other direction depending upon the direction of rotation of shafts 3 and 5. A limit switch LS has two contacts, II and I2, cooperating with cam it. Contact l I is opened when cam [0 travels toward the left beyond an adjusted limit position which corresponds to the safe, minimum length of cable paid out by the winch drum. Contact 12 is closed when the traveling cam l0 moves toward the right beyond an adjusted position corresponding to the maximum cable length to be paid out by the drum. The operation of the two contacts has the effect of changing the torque of winch motor WM toward re-establishing a safe cable length as will become apparent hereinafter.

The motor WM is energized by a generator .G whose armature l3 rotates at constant speed when in operation. The generator has a series connected interpole and compensating field winding l4 and derives its main excitation from a separately controlled shunt-type winding l5. Direct current of constant voltage is supplied through a main switch S to the mains X and Y of the motor control system. The shunt field windings of motor WM and generator G are energized from mains X and Y under control by a master switch MS, a set of push buttons denoted by HB, LB and RB, and also under control by the contacts II and I2 of the above mentioned limit switch LS. The control system includes further a number of auxiliary devices to be described presently.

A contactor 'IM with a control coil and two contacts 2| and 22 serves for controlling the coil 7 of the friction brake B and cooperates with resistors 23 and 2m in the field circuit of the motor WM so as to change its field excitation in dependence upon the operating condition of brake B. Two relays denoted by 2M-and 3M are provided mainly for connecting the generator field winding I5 to one or the otherof two adjustable rheostats FR and BR. Contactor 2M has a winding 36 which, when energized, closes three contacts 3i, 32 and 33 while opening an interlock contact 34. Similarly, relay 3M has a control coil 45 whose energization causes three contacts 4!, 42 and 43 to close while an interlock contact 44 is opened. The circuit of coil of relay 2M extends through the inter-lock contact 54 of relay 3M, and the circuit of coil appertaining to relay 3M extends through contact 34 of relay 2M. In this manner the two relays are electrically interlocked so that one of them remains inactive as long as the other is energized.

The above mentioned rheostat BR has a resistor 5| and an appertaining slide contact 52 connected between contacts 82 and 4! in series with an adjusting or calibrating rheostat ll whose setting need not be changed during the normal operation of the system, 'Rheostat FR has a resistor 53 and a slider 54 and is connected to another calibrating resistor 12 whose adjustment remains likewise unchanged during the normal operation of the system. Contact 3! of relay 2M when closed, connects rheostat FR to the generator field circuit, while the closure of contact 4| in relay 3M serves to connect rheos stat BR into the generator field circuit. Due to the interlocking connection of relays 2M and 3M explained in the foregoing, only one of the two rheostats FR and BE is Qperative at a time.

The two slide contacts .52 and 54 are mounted on a common shaft 155 which is connected to the armature 56 of an auxiliary drive motor RM. This motor has two field windings 51' and 58 for operating it in opposite driving directions depending upon which of the two coils is energized. The field winding 51 is connected through a limit switch 60 and the above-mentioned push buttons LB and HB to the master switch MS. The field winding 58 is also connected to these push buttons and the master switch through second limit switch 6|. An arm 59 firmly mounted on shaft serves to open the switch 60 when the sliders 52 and 54 have reached one end of their travel, while the same arm 59 opens the limit switch 61 in the other end position of the sliders.

,, The pointer of an indicating or exhibiting device D is also connected with the motor shaft 55 and cooperates with a stationary scale 63 so as to indicate the angular position of the sliders. As will be explained hereinafter, the scale 63 is so calibrated that the indication effected by the pointer 62 is representative .of the maximum or standstill torque of the winch motor at any in, stant of a winch operation, and hence also repre: sentative of the maximum pull or tension which might possibly occur in the winch cable under the control conditions then prevailing.

Two auxiliary control relays lCR and 20R, each provided with a control coil 45 or 47 and a contact 55 or 48., perform a, cooperative 11110: tion together with the above mentioned relays 2M and The system contains further a pro.- tective low-voltage relay LV whose control coil 65 actuates two contacts 66 and 61. All other relays of the control system are energized by circuits extending through contacts 56 and 61. Consequently these contacts must be closed in order to permit an operation of the winch drive. The closure occurs automatically when the main switch S is closed while the master switch MS is in its off position, provided the voltage of the direct-current excitation remains above a given value. Once the coil 65 of relay LV is energized, the master switch MS may be turned to its manual? or automatic position without deenergization of the relay. However, if 2. volt.- age failure or power interruption occurs when the master switch MS is not in the off position, it must first be returned to off before relay LV can pick up'in order to re-establish the operative condition of the system. The brake B is operative whenever the relay LV is deenergized. Hence, the winch drive is automatically blocked or stopped upon the occurrence of voltage or power failure.

Push button HB, when actuated, serves to en-, ergize the auxiliary motor and causes it to adjust the rheostat BR and PR in the direction which corresponds to a torque increase in motor WM. Push button LB, when depressed, causes the rheostat motor to actuate the rheostats BR and FR in the opposite direction, thereby reduclng the torque .of motor WM. Push button RB is provided for running the winch motor WM in the pay out direction at relatively high speed under no-load or light-load conditions. The pay out button RE is operative when the master switch is in the manual position but ineffective in the oif" and automatic positions of switch MS.

The above described system operates in the following manner.

In order to place the system in operative con.- dition, the main switch S is to be closed. This has the efiect of energ zin the lowlta e relay LY in ircuit MS, 5, Y o that c tacts 66 and 61 are closed. The shunt field winding 2 of the winch motor becomes weakly energized through resistors 23 and 24 but the motor armature I receives no energization from generator G because the generator field winding I5 remains deenergized due to the fact that both relays 2M and 3M are deenergized. Relay IM is also deenergized so that its contacts 2| and 22 remain open. As a result the brake B remains effective and the motor WM stopped.

MS in manual position When now the master switch is placed into manual position, the winch drive is under control by the push buttons. Pressing the reel-out button RB will energize relay 3M provided ratchet pawl 8 is disengaged and contact 9 closed as shown in the drawing. The energizing circuit for relay 3M extends through circuit X, MS, RB, 34, 9, 4! Y. Relay 3M closes its contacts 4!, 42 and 43 and opens contact 44, thus rendering relay 2M inefiective. Due to the closure of contacts 4| and 42, the field circuit of the generator is energized through potentiometer BR in circuit X, 4|, BR, II, I5, 42, Y. As a result, winch motor WM is energized by generator G to run in the pay out direction. The closure of contact 43 energizes coil 20 of brake relay IM which, in turn, releases brake B by closing contact 22 and increases the voltage across motor field winding 2 by closing contact 2 I. These conditions prevail as long as the reelout button RB is kept depressed. When the button is released, the motor WM is stopped and the brake B set. Hence the operation of button RB permits paying out any desired length of cable.

When the raise button H3 is pressed, relay ICE is energized through circuit X, MS, I-IB, LB, coil 45 of ICR, Y. At the same time, rheostat motor RM is energized through X, MS, HB, LB, 6| field coil 58 of RM, 56, Y. Relay lCR energizes contacto-r 2M through X, MS, 66, 61, 46, 44, coil 39 of 2M, Y. Contactor 2M energizes the generator field winding I5 through Y, 32, I5, I2, resistor 53 of rheostat FR, 3|, X; and the rheostat FR, driven by motor RM, increases progressively the excitation of the generator and hence the torque of winch motor WM. Contact 33 of relay 2M also energizes coil 20 of brake relay IM, which releases brake B by closing contact 22 and imposes high excitation on the field winding 2 of the winch motor by shorting resistor 24 at contact ZI. As a result, the winch motor develops torque in the reclaim direction, and this torque increases until the raise button HE is released.

When the lower button LB is actuated, the relay ZCR becomes efiective through X, MS, HB, LB, coil 41, of 2GB, Y. The rheostat motor RM is now connected with its lowering field winding 51 in the circuit Y, 56, 51, 60, LB, HB, MS, X and reduces the generator excitation. Relay 2M comes in through Y, coil 30 of 2M, 44, 48, 61, 66, MS, X, while relay 3M is interlocked by the opening of contact 34 and stays deenergized. Hence, potentiometer BR is now ineffective. The closure of contact 33 in relay 2M energizes coil 20 of relay IM through Y, 20, 33, 61, 66, MS, X. Relay IM closes contact 22, thereby releasing the brake, while contact 2| puts increased voltage on the motor field. The winch motor is now again caused to develop torque in the pull-in direction, but the torque decreases as long as button LB remains depressed.

During the actuation of push button H3 or LB, the rheostat motor RM is in operation only as long as the arm 59 of the rheostat shaft 55 remains within the maximum and minimum limit positions. Upon passing beyond either position, limit switch 60 or 6| will automatically stop the further motion of the rheostat motor.

When, during the actuation of either button H3 or LB, the motor standstill torque corresponding to the then prevailing excitation of the generator G is exceeded by the torque exerted on the motor shaft by the pull of the towing cable, the motor is forced to reverse its direction, and cable will be paid out. This standstill torque at any instant of the operation is determined by the setting of the rheostats BR and FR and hence corresponds to the indication of pointer 62 on scale 63 as set by the operator. The indication is further representative of the pull and tension conditions in the winch cable, provided the frictional losses between the winch drum and the motor are properly taken into consideration. This will be explained in a later place of this specification. As far as described, it will be un derstood that the push buttoms of the system permit a manual control of all steps required for the performance of a towing operation. The cable can be paid out or pulled into any available extent, and the torque of the motor is adjustable so as to satisfy any desired towing conditions.

MS in automatic position When MS is set for automatic operation, the reel-out button RB is disconnected so that the winch is now under control only by buttons HB and LB and limit switch LS, while an inadvertent operation of the reel-out button RB is prevented. The length of cable is then controlled by the operation of the limit switch LS in accordance with the selected torque setting determined by the adjustment of the rheostat FR. This setting can be varied at will before or during the towing operation by operating the buttons HB and LB as described in the foregoing. During this towing operation, relay 2M is permanently energized through circuit X, MS, 44 coil 30 of 2M, Y, so that the circuit of the generator field winding I5 is closed at contacts 32 and 3|, placing rheostat FR in operation, while the closure of contact 33 causes relay IM to impose voltage on the field winding 2 of the winch motor WM by shorting field resistor 24. At the same time, brake B is released by the closure of contact 22 and stays released during the entire towing operation, 1. e. as long as MS is in automatic" position, so that the load is now taken up by the countertorque developed by the winch motor and adjusted by the operator.

When during the towing performance, the cable length reaches the minimum length for which the limit switch LS is adjusted, cam I0 opens the contact II and thereby places the normally shorted resistor I2 in series in the circuit of field winding I5 so that the field of G is weakened for reduced motor torque. As a resuit, the towing pull dominates and causes more rope to be paid out. When, on the other hand, the paid-out length of rope exceeds the desired limit, cam I0 closes the contact I2 and shorts the rheostat resistor 53 so that the field winding I5 receives increased excitation for increased motor torque so that the rope is pulled in.

As apparent from the foregoing, the motor standstill torque, at any time during the towing operation, is determined by the setting of the rheostat. apparatus. While. this settin in the illustrated embodiment, varies during manual operation, it is as a rule at a selected constant value during automatic performances. The control system is so designed and rated that the maximum torque which the winch motor is able to develop for any setting within the entire available range of control remains, below the safe limit value as regards the cable. The maximum torque possible at any selected instant of a towing operation and, hence, the corresponding; maximum cable tension are dependent upon the selected rheostat adjustment. Consequently, the position of pointer 62 relative to scale 63 is. a measure of the maximum cable tension. When this tension is exceeded, the motor, through energized for heaving-in operation, is, overhauled and forced to pay out, thus, preventing a further increase in cable pull and tension. In other words, the electric energizing system of, the winch motor performs also the function of an adjustable tensiometric device and thus obviates the use of mechanical or other separate tensiometric appliances.

It follows from the foregoing that the scale of the indicating device, if desired, may be calibrated in pounds of tension. Then, however, the considerable amount of friction in winch drives of this type must be taken into consideration. The frictional loss in the gear mechanism may amount up to 30% or more of the total power consumption. When the tension of the cable becomes too large while heaving in, the motor will reverse its direction of rotation and pay out although the motor torque remains in the same direction. Due to this change in rotary direction without directional change in torque, the frictional load shifts from the motor to the drum. That is, the friction has to be overcome by the motor when heaving in, and by the cable pull when paying out. If the motor torque remained constant during its change of running direction, the cable pull would increase considerably, for instance to more than twice its value for a frictional loss of 30%, in order to make the motor reverse its direction for paying-out operation, Hence, in order to maintain the same pull, the motor torque has to be lowered considerably. The above described use of a generator shunt field regulated by two difierent rheostats FE. and ER aifords a control of the motor torque in the just mentioned manner. However, the position of pointer 62 continues to correspond to difierent drum torque and tension values depending upon whether the winch drive pays out orheaves in. In order to take this into account, two different scales may be provided. In practice, however, this is unnecessary because the cable tension when paying out is always higher than the reclaiming tension at the same rheostat setting. As a matter of fact, the reclaim tension may be as low as one-half of the corresponding pay out value. Hence, it sufiices to calibrate the indicating deviceonly with reference to the pay out power condition of the system so that one indicating scale is needed showing merely the maximum values of torque, pull or tension obtainable at the setting selected by the operator.

The diagrams of Figs. 2, 3 and l serve to further elucidate the above described operating conditions by way of example.

In Fig. 2, the torque conditions of a winch motor (WM in Fig. 1) are represented by curve 25 in dependence upon the: percentile excitation of the separately excited generator shunt field (15 in Fig. 1). Under the exemplified operating conditions, a reduction in the separate generator excitation by approximately 34% of the normal value reduces the motor torque by about 40% of its normal value.

The diagram of Fig. 3 typifies the relation oi the motor torque to the drum torque (pull or tension) in percentile values. Curve 2' represents the ideal case of a frictionless winch drive. Curve h represents schematically the conditions actually prevailing when the winch motor heaves in while overcoming the winch friction, this friction being assumed as a constant friction torque of 20% of the full load motor torque. Curve p represents the case of operation in which the cable pull overcomes the motor torque as well as the friction in the winch, thereby causing the drum to pay out. A reduction in the motor torque of about 40% is required to shift the char- .acteristic from curve h to curve p when reversing the motor operation from heaving in to paying out. according to this diagram. Such a change in torque is substantially obtained by the above described switching over from one to another rheostat FR and BE. The operating characteristics of these rheostats are represented in Fig. 4.

The ordinate of the diagram in Fig. 4 represents the resistance values of the rheostats RB and RF in ohms while the abscissa represents the rheostat adjustment, i. e. the amount of travel of the rheostat sliders expressed in per cent of the full available travel distance. Curve b relates to rheostat BR, and curve f to rheostat FR. For any given setting of either rheostat, the motor may change from driving to driven condition. As a result, the operating point will shift from the heave-in to the pay out characteristic according to Fig. 3, for instance between points H and P, so that one and the same setting of the indicating device corresponds to a range of pull or tension values whose maximum lies on curve p according to Fig. 4, Hence, the scale of the indicator iscalibrated in relation to these maximum pay out values of curve p as explained previously.

It will be obvious to those skilled in the art, upon a study of this disclosure, that systems of the type described may be modified in various respects without departure from the objects, spirit and essential features of my invention. Therefore, I wish this specification to be mainly illustrative, the scope of the invention being intended to be limited only by the following claims.

I claim as my invention:

1'. A variable voltage winch control systemcomprising, in combination, a cable drum, a winch motor in mutual driving connection with said drum, a generator having an armature connected with said winch motor and a field winding for controlling the voltage of said motor, a field circult connected with said field winding, rheostat means disposed in said circuit for controlling the excitation of said winding, means under control by the operator for adjusting said rheostat means independently of the operation of said drum so as to cause said generator to vary the torque of said motor, indicating means connected with said rheostat means and being calibrated in values indicative of maximum cable tension, and limit switchmeans controlled by said drum and connected' with said field circuit for increasing said excitation upon paying out a maximum length and decreasing said excitation upon reclaiming a. maximum length of cable by said drum.

2. A variable voltage winch control system. comprising, in combination, a cable drum, 2. winch motor in mutual driving connection with said drum, a generator having an armature connected with said winch motor and a field winding for controlling the voltage of said motor, first rheostat means and manually actuable contact means connected with said field winding for controlling its excitation in order to permit reeling out a desired length of cable, second rheostat means and circuit control means connected with said field winding for controlling its excitation during towing performance, an auxiliary motor disposed in driving connection with said first and second rheostat means for varying their resistance adjustment in order to cause said generator to vary the torque of said winch motor, operator-controlled means for causing said auxiliary motor to adjust said rheostat means independently of the operation of said drum, and indicating means connected With said rheostat means and being calibrated in values indicative of maximum cable tension.

3. A variable voltage Winch control system comprising, in combination, a cable drum, a winch motor in mutual driving connection with said drum, a generator having an armature connected with said Winch motor and a field winding for controlling the voltage of said motor, first rheostat means and manually actuable contact means connected with said field winding for controlling its excitation in order to permit reeling out a desired length of cable, second rheostat means and circuit control means connected with said 10 field winding for controlling its excitation during towing performance, said two rheostat means having each a circular resistor and a rotatable slider, and said two sliders having a common drive shaft, an auxiliary reversible motor in driving connection with said shaft for varying the resistance adjustment of said rheostats in order to cause said generator to vary the torque of said win-ch motor, operator-controlled means for causing said auxiliary motor to adjust said rheostat means independently of the operation of said drum, and indicating means connected with said shaft and being calibrated in values indicative of the maximum cable tension obtainable at the adjusted setting of said rheostats.

STANLEY A. BOBE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain Feb. 1920 Number Number

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