US1817797A - Motor control - Google Patents

Description

Aug. 4, 1931.

I. F. BAKERv MOTOR CONTROL Filed July 27, 1927 FLgJ.

Patented Aug. 4, 1931 UNITED STATES PATENT OFFICE ISAAC I. BAKER, OF EAST ORANGE, NEW JERSEY, ASSIGNOB TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK MOTOR CONTROL Application filed July 27,

My invention relates to improvements in systems of control for electric motors,"and in particular to such systems intended for the control of motor driven hoists.

Among the objects of the invention, as applied to motor driven hoists, for example, are the following: i

1. To rovide an improved arrangement for limiting the extent of movement of the hoisting device. 7

2. To provide an improved system. in

, which the hoisting and lowering operations are governed by separately operable manuall operated switches, such as push button switches or the like. v

3.To provide a system in which when either an up or a down push button switch is momentarily operated the hoist is caused to proceed in the corresponding direction at low s eed and the speed thereof may be increase by operating a fast'push button, the arrangement being such that the fast speed is maintained (within the limits ofoperation of the hoist) as long as the fast push button is maintained operated and when the fast button is released the speed of the hoist is automatically reduced to the. said low speed.

4. To provide a s stem in which in case the hoist is proceeding in either direction and the push button for the other direction of operation is operated, the hoist will be automatically stopped and cannot be restarted until after the stop push button switch is first operated.

For an understanding of the features of construction and mode of operation of a present referred embodiment of the invention, re erence is had to the accompanying drawings in which Fig. 1 shows in simplified diagram a system of control for an electric motor connected to operate a hoist Fig. 2 is a detail of the arrangement of Fig. 1 for the purpose of showing the circuit arrangement andother features of the switch mechanism whereby the extent of operation of the hoist is limited, and Fig. 8

is a diagrammatic representation of the system of control showing Figs. 1 and 2.

Referring tothe drawings, the hoist is in- -of the invention.

1927.. Serial no. 205,014;

dicated as having two drums 10 and 11 on which the cable 12 is wound and unwound.

\tric' motor 14 which is indicated ,as of the series'type having a series field winding 15 led by the controlling means to be presently described and the controlling means has rovision for accomplishing the stated obJects The controlling means comprises a pair of directional electroma netic switches or contactors, one of which 15 designated U, indicating that this contactor is provided for effecting rotation of the motor ,14 to raise thehoisting block 13 and the other contactor'is designated D to indicate that this contactor isprovided for effecting connections of the motor 14 toproduce a lowering of the hoisting block 13. These contactors are each prov ded with a set of main contacts which are closed when and an armature 16. This motor is controlthe contactor is in the deenergized position and another set ofmain contacts which are closed when the contactor is in the energized or attracted position. The arrangement is such that whene ither the U or D contactor is closed, the motor 14 is caused to operate at low s ed, the resistor R1 being connected in mu tiple relation-with the motor armature and the resistor R2 being connected in series relation with the motor armature.

The contactor designated F i is provided for effecting high speed connections for the motor. In the deenergized position of this 1 The upper push button switch is designated 8 and performs the function of a stop cone resistor R2 in series relation there- 7 for controlling the up contactor trolling switch. The next lower push button switch is designated a and is rovi ggd e next lower push button switch is designated by d and 1s provided for controlling the down contactor D. The bottom push button switch is designated f and this push button is provided for controlling the fast or speed up contactor F.

Oneof the features of my invention is an improved arran ement whereby the limits of movement 0 the hoisting block 13 are accurately determined. This limit or travel protection is provided by means of the push button switches '17, 18, 19 and 20. These switches are each carried by an associated hoisting drum and are mounted on the periphery of the associated drum so as to be engaged by the hoisting cable 12 to effect operation thereof. In other words, each push button switch will be assembled as a unit and mounted in a suitable aperture in the outer periphery of the associated hoisting drum, with the button of the switch projecting from the periphery of the drum so as to be engaged by the hoisting cable as the cable is wound upon the associated drum. The switches 17 and 20 form one, pair of swltches and the switches 18 and 19 form another alr.

p The circuit connections of the switches 17, 18, 19 and 20 will be better understood from a description of Fig. 2. It .will be seen from this figure that each push button switch is provided with a compression spring which tends to maintain the push button switch contacts in a definite position. Thus, the switches 17 and 20 are of the normally 0 en type, and the switches 18 and 19 are 0? the normall closed type. By reference to Fig. 1, it Wlll be seen that the cable 12 is wound upon the drums 10 and 11 to such an extent that theswitches 17 and 20 which are provided for limiting the downward movement of the hoisting block 13 have their respective contacts closed against the tension of the respective biasing springs, whereas the switches 18 and 19 which are rovided for limiting the upward travel of t e hoisting block have their respective contacts opened, due to the action of the cable 12 pressing on the operating button of these I respective switches; The switches 17, 18,

19 and 20 are interconnected in the manner shown in Fig. 2, the sets 21 and 22 of conducting rings and brushes being provided for establishing electrical connections to the push button switches carried by the ,respec-' tive drums.

As thus constructed and arranged and with the parts in their respective positions indicated in the drawing, the operation of my invention is as follows :The hoisting block 13 hasbeen raised to its upper limit of travel and further movement in this direction is prevented so that the only movement of the hoistin block which is permitted is in the down irection. To cause the block 13 to move downwardly, the down push button (3 is momentarily depressed, thereby completing a circuit from.

the lower conductor of the source 23, wind ing of directional contactor D through the corresponding conducting ring of the set 22, the contacts of limit switch 20 through the right-hand conducting ring of the set 21, the contacts of limit switch 17 through the winding of electromagnetic brake 24 to the upper supply conductor. The current through the winding of the electromagnetic brake will not be sufficient to efi'ect release of this brake and the brake will not be released until after the contactor D is closed in response to the energization thereof. When this contactor closes, an auxiliary switch 25 associated therewith establishes a holding circuit for the winding of the contactor D, through the stop push button 8 so that the down push button may be re leased.

lVith the main switch member of contactor D in its upper position, a circuit is made which may be traced as follows :--from the lower conductor ofithe source 23, through the upper main stationary contact of contactor D, movable switch member of this contactor, through the motor series field 15, through the lower main contacts of con,- tactor U, through the motor armature 16 and the resistor R2, with the resistor R1 included in multiple relation with the motor armature, throu h the winding of the electromagnetic braIze 24 to the upper supply conductor. The electromagnetic friction brake 24 will be released and the motor 14 will be energized in such a direction as to cause downward movement of the hoisting block 13. After this motion has proceeded for a small distance, the cable 12 will be unwound from the drums 10 and 11 to such an extent that the limit switches 18 and 19 will be permitted to close their respective contacts in accordance with the bias produced by their respective compression sprin s. This will produce no result at this time but will make it possible to effect 9.

raising of the hoisting block 13 in case that the upper supply contactor.

tacts of the contactor F are closed, the motor armature is included in a dynamic brake circuit. The motor is thus stopped by being disconnected from the source of supply and by being connected in a dynamic braking circuit. If instead of depressing the stop push button a momentarily, the oper-' ator had momentarily depressed the up push button u, the motor would likewise have been disconnected from the source of supply and be included in a dynamic brake circuit. Thus with the down contactor D energized, the momentary depression of the up push button it will effect the energization of the up contactor U through, acircuit which inc udes the stop push utton a, the up push button contacts M, winding of up contactor U, through the limit switches 19 and 18, to

The n eonductor U will open its lower set 0 main contacts, thereby disconnecti the motor from the source of supply an the circuit established through the upper main contacts of this contactor connects the series field 15 in a local circuit. The armature of the motor is included in a local dynamic brake circuit as was previously the case when the stop push button a was depressed. When "the motor is thus disconnected from the lowering of the hoist bloc opens the circuit. thro tacts an source of sup 1 the winding of the electromagnetic bra e 24 is simultaneously deenergized and this brake is caused to apply and thereby hold the hoisting drums and the hoisting block in position, as is common in equipments of this character.

When the hoist is thus stopped by the depression of the up push button u, it is necessary for the operator to momentarily depress the stop pus button a prior to being able to again start the hoist in either direction. That is because of the fact that when the up contactor is energized, it closes its upper auxiliary contacts and establishes a holding circuit for the winding of this contactor. This holding circuit-1s maintained as long as the stop push button .9 remains closed. After the stop push button a has been momentarily depressed, the equipment may be started and stopped in the customary manner.

Assume that after. the hoist had been started, as previously ex lained, for the 13, an increase of the wering s is desined. -This is effected by depressing the fast push button f, thereby energizing the winding of contactor F throu h a'circuit whichma be readily traeed.- en the contactor is thus ener d, it opens itslower main concloses its upper main contacts. The opening of the lower main .contacts h the armature shunting resistor R1 and the closing of-the upper main contacts efiects the shun of thear'mature series resistor R2. The otor is thus connected directly to the source of supply and hoist will continue (within the limits of hoist travel as determined by the limit switches 17 and 20) as long as the fast ush. button is maintained depressed.

en this pus button is released, the connections for the motor armature revert to those previously explained for the slow speed down direction of movement of the hoistin block. If the cable 12 is unwound from t e hoisting drums 10 and 11 to such an extent that the limit switches 17 and 20 are released to open in accordance with their bias, the controlling circuit for the down contactor D is opened and the motor is thus disconnected from the source of supply and included in a dynamic brake circuit and at the same time the electromagnetic brake 24 is applied to hold the hoist.

It is believed that those skilled in the art will readily understand the operation of the manually operable push. button switches. to effect movement of the hoisting block from either limit of movement thereof to the other, as well as to efl'ect movement of the hoisting block between its limits of operation in such a direction and at such a speed as the operator desires, without a further detailed description of the arrangement.

Among the features of advantage of my invention is that by reason of the fact that the limit switches ai e carried by the hoisting drums and are operated directly by the cable as the cable is wound upon and unwound from the hoisting drums, a certainty of operation of these limit switches is had which is desirable. Another feature of advantage is that no complicated electrical interlocking or expensive mechanical interlocking between the directional conh speed operation of the tactors U and D is necessary to prevent both these contactors being closed at a time, as is the case in other systems with which I am familiar, since in case either contactor is closed to efl'ect movement of the hoisting block in the selected direction, if-the other contactor for 'the other direction of operation is closed, the hoist will merely stop. "Another feature of advan is that mere y a momentary operation of t e push buttons through which a control of the hoist is efiected is necessary to eflect either slow speed operation of the hoist in either direction or the stopping of the hoist from either direction of movement, so that in case the operator desires to speed up the hoist, he need merely depress the fast push button f.

As long as this fast push button is depressed,

the fast speed will be maintained (within the limits of operation of the ho sting block). I would have it understood that n actice, the push buttons 0, u, d and f will mounted in a common bly and for Q stopped by the subsequent operation of sai general construction well known and understood by those skilled in the art. It will further be observed that the wiring connections are very simple and willreadily be understood by electricians whose duty it is to maintain the operation of equipments of this nature.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In a system of motor control, an electric motor, and controlling means therefor including a pair of directional switches, means including a air of separately operable manually-opera le controlling switches and connections controlled thereby for effecting operation of the motor in either direction when the corresponding one of said controlling switches is momentarily operated and the stopping of the motor when the other controlling switch is subsequently operated, and switchin means for controlling the stopping of said motor at the will of the operator, said switching means being connected so that the 'motor after bein other switch cannot be restarted until said switching means is operated.

2. In a system of motor control, an electric motor, and controlling means therefor including a pair of directional contactors, a separate manuall 0 switch for each 0 sai contactors, a separate manually-operated switch for controlling the stopping of the motor at the will of the operator, and electrical connections through which when either one of said first mentioned controlling switches is'molnentarily operated operation of the motor in the selected direction is effected and the stopping of the motor is effected when the other of said first mentioned controlling switchesis momentarily operated, the said connections beingsuch that after the stopping of the motor is thus effected, the motor cannot be restarted until after said stop controlling switch is operated.

3. In a system of motor control, an electric motor and controlling means therefor comprising a pair of directional contactors', a resistance normall included in the motor armature circuit, a ast speed contactor for controllin said resistance, a separate manually-opera le controlling switch for each of said contactors and electrical connections controlled thereby through which a momentary operation of a corresponding one of said controlling switches efl'ects operation of a corresponding one of said directional conrated controlling switch which is operated, and a subsequent operation of the controlling switch for said fast speed contactor disconnects said resistance so as to effect an increase in the motor speed irrespectively of the direction of rotation and biasing means for automatically causing said last mentioned switch to reconnect said resistance to reduce the speed of the motor to its former value at the termination of said subsequent operation.

4. In a system of motor control, an electric motor and controlling means therefor including a pair of directional contactors, a resistance normally included in series with the motor armature, and a second resistance normally connected in arallel therewith, a fast speed contactor ibr controlling said resistances, a separate manually operable controlling switch for each of said contactors, electrical connections through whicha momentary operation of a corresponding one of said controlling switches efiects operation of a corresponding one of said directional contactors to cause slow speed operation of said motor in a direction correspondin to the controlling switch which is operate and a subsequent operation of the controlling switch for said fast speed contactor causes said fast speed contactor to disconnect said resistances so as to effect an increase in the motor speed irrespectively of the direction of rotation, and biasing means for causing said last mentioned switch to reconnect said resistances so as to efiect slow speed operation of the motor at the termination of said subsequent operation.

In vwitness whereof, I have hereunto set my hand this 25th da of July, 1927.

. ISA C F. BAKER.

tactors to cause operation of said motor in a direction corresponding to the controlling

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