US974238A - Motor control. - Google Patents

Description

A. M. GOYLE. MOTOR CONTROL. APPLIGATION FILED JAN. 30, 1908.

Patented Nv.1,1910.

3 SHEETS-SHEET 1.

A. M. COYLE. MOTOR GONTROU.

AYPLIOATION FILED JAN. so, 190s.

Patelltd NOV. 1, 1910.

974,238. f figg.

MMI JQ um* M all-rouw..

Patented Nov. 1, 1910.

3 SHEETS-SHEET 3 0 2 w m I2 k u? W1 .l 1 L n .r la, N w f 7 Y n L f mq u .Y ,#0 Q r W M UNITED STATES PATENT OFFICE.

ANDREW M. COYLE, OF NEW YORK, N. Y., ASSIGNOR T0 OTIS ELEVATOR CQMPANY, 0F JERSEY CITY, NEW JERSEY, A. CORPORATION OF NEW JERSEY.

MOTOR CONTROL.

Specification of Letters Patent.

.Patentes Nov. 1, 1910.

Application filed January 30, 1908. Serial No. 413,473.

To all whom 'it may concern:

Be it known that I, ANDREW M.- CoYLE, a citizen of the United States, residing in New York, in the county of New York and State of New York, have invented a new and useful Improvement iny Motor Controls, of which the following is a specification.

My invention relates to a system of control for electric motors, partlcularly those used for hoisting and lowering theater curtains, but it may have a' general application.

An object of my invention is the provision of improved means for controlling the speed of operation of the respective units of a multiple curtain hoisting apparatus which lifts `and lowers curtains at the same time. A further object is the provision of means for controlling the operation of electric motors, wherein one mot-or is used for hoisting and another motor is used for lowering, also means for varying the relative speeds of the hoisting and lowering motors.

Other objects of my invention will appear hereinafter, the novel combinations ofI elements being set forth in the appended claims.

In the accompanyingdrawings, Figure 1 represents a wiring diagram of my control system, wherein a single motor is used for both hoisting and lowering; Fig. 2 is a wiring diagram in which there are two motors, one for hoisting and one for lowering. Figs. 3 and 4 represent the hoisting apparatus adapted to the systems of control shown in Figs. 1 and 2 respectively; Figs. 5 and 6 illustrate a preferred form of stopmotion apparatus shown'in 4-plan and side' views respectively.

Similar reference characters designate similar parts in both/figures.

The principal features of the particular form of'hoisting mechanism to which my improved system of motor control is especially adapted are disclosed in my co-pending application, Serial No. 397,310, tiled October 14, 1907 Patent No. 959,999, May .31, 1910, for an 4improvement in 'curtain hoisting apparatus.

Briefiy described, the hoisting apparatus to which .my invention is particularly' adapted, is illustrated in Figs. 3 and 4, and

comprises a motor 80 upon whose shaft 93 is secured, at regular intervalswa series of friction driving members ork ditks, such as 94 adapted to coperate with jother frictional driven members, such as 95, which latter aregeared to suitable hoisting drums as 96. Each friction driving disk and cooperating driven mechanism and hoisting drum comprises a single unit of a multiple hoisting apparatus. While the number of such units may be as many as desired, for purposes of illustration I show in Figs. 1 and 2 of the present drawings controlling systems for a 4multiple hoisting apparatus having six hoisting drums or units, and adapted to control the hoisting and lowering of siXl theater curtains or other apparatus. The friction wheels 94 and 95 which are geared to their respective hoisting drums, are pivotally mounted so that they may be independently raised out of or lowered into engagement with their respective friction driving disks upon the motor shaft. Each hoisting unit is provided with a brake shoe 99 which coperates with the friction wheel 95 driven by the disk 94 upon the mo-l tor shaft, and this brakek shoe is so arranged that thebrake is applied and the friction wheel is raised out of engagement with the driving means simultaneously. This operation is effected by means of a separate `that when the same is properly ener ized and the brake magnet is also energizel the parts are in proper position to effect a raising of the load. If, however, the brake magnet is energized and the tripping magnet is denergized or does not receive current, the brake will be released, but the tripping apparatus controlled by the tripping magnet Will prevent the friction driving wheel from engagin the driving disk `upon the motor shaft, an the hoisting drum is in a position to be turned backward by means -of the unbalanced load. f The apparatus to which the controlling system shown in Fig. 1 is especially applicable has, furthermore, a number of gear wheels such as g 100; one foreach hoisting unit, each'of which is gearedl directly t-o its'` respective hoisting4 drum and which is connected through a clutch mechanism to a sprocket wheel 101 which in turn is connected by a sprocket cha-in 102 to a smaller sprocket wheel 103 rigidly mounted upon the motor 5 shaft. This clutch mechanism is so arranged that when the hoisting drum is raising a load, or when the brake is applied and the drum at'rest, it does not come into operation, but as soon as the unbalanced load tends to drive the hoisting drum backward, the clutch at once operates and operatively connects the hoisting drum to the motor shaft and the speed of descent of the load depends upon the speed of rotation of the motor. Thus, while the motor always runs in one direction, the speeds of hoisting and lowering are both dependent upon the motor speed.

The apparatus particularly adapted to the controlling system shown in Fig. 2, is illustrated in Fig. 4 and is similar in every respect to the foregoing description, but with this one exception: The gear 100 meshing with the hoisting drum and connected through a clutch mechanism to the hoisting motor, is in this instance designated by 100 and is connected through a similar clutch mechanism to the shaft 93 of an additional motor 80 which is only used for lowering. Each motor therefore, performs its separate function ofl hoisting and lowering, and as the relative speeds of these motors may be varied at will, the relative speeds of hoisting and lowering may be adjusted to any desired speed, and thus, in the particular case of theater curtain control, manyand varied scenic effects may readily be produced with facility and despatch.

Each hoisting drum is provided with a limit switch or stop -motion apparatus which is operated by the hoisting drum through gearing and serves automatically toy slow down and stop any of the hoisting drums at either the upper or lower limit of curtain travel. g

The stop-motion apparatus maybe mounted in a housing 104 onftop of the machine and operated by gear wheels 105 respectively in mesh with the gear wheels 106 of the hoisting units. The purpose of the stop-mo` tion apparatus is to operate circuit-breakers so as to denergize the electro-magnet 62, and to also slow down the motor a short time l prior to the denergization of the brake electro-magnet. It is to be understood that for each unit of the' multiple hoisting apparatus there is a corresponding unit of the stop-motion apparatus, and that when a stop-motion unit operates to open its circuitcloser only the corresponding unit of the multiple hoisting apparatus will be effected. This operation is automatic, as will be more fully explained hereinafter.

Referring now more particularly to Figs. 5 and 6 where is shown a preferred form of my improved stop-motion apparatus adapted to a hoisting machine having any desired number of units, it will be seen that I have provided a base 107 for the stop-motion apparatus, which base may be bolted to the frame 108 of the hoisting apparatus shown in Figs. 3 and 4. A rectangular frame 109 is secured to the base 107 and projecting upwardly from its opposite rear corners are integral bracket arms or bearing standards 110 and 110 which support a rod 111 upon which are loosely mounted swinging arms 112 and 112. Between these arms is a bushing 113 on the rod 111; the purpose of said bushing being to hold the arms 112 and 112 8O spaced apart and in their proper positions. The gear wheel 105 which is driven by the gear 106 of a hoisting unit is secured to a shaft 114 which carries a small pinion 115. The latter extends the entire length of the shaft 114. Mounted on the frame 109 and parallel with the shaft 114 is a screw threaded shaft 116 which is held stationary by its supports. Mounted on the shaft 116 are two gear wheels 117 and 117 whose hubs are 90 screw-threaded to correspond with the threads on the shaft 116. On the hub of the gear wheel 117 are two cams 11S and 119, and on the hub of the gear wheel 117 are two similar cams 118 and 119. A rock- 95 shaft 120 is journaled on the base 107 and rigidly secured thereto are rock-arms 121 and 122 which have at their outer extremities lateral projections 121 and 122 respectively, which are arranged to be engaged hy the cams 118 and 118, respectively. The cams 119 and 119 are arranged to engage the detents or trips 123 which are carried by the arms 112 and 112; the latter each carry bridging members 57 and 58 to electrically 105 connect the contacts 59 and 61.

The operation of the construction shown in Figs. 5 and 6 is as follows: Vhen the hoisting mechanism shown in Figs. 3 and 4 is in operation, the gear wheels 117 and 117 110 of the stopmotion device are rotated by means of the gear connections above described. This rotation will impart to the gears 117 and 117 alateral movement, owing to their threaded engagement with the shaft 116. If it be assumed that the gear wheel 117 is rotated in a counter-clockwise direc- `tion when looking at it from the right, then l contact plate 57 and breaking the electrical engaged connection between the contacts 59 and 59.

It will be observed that the lateral surfaces of the cams 118 and 119 are inclined or spiral in form and of the same pitch as the threads on the shaft 116. This is` for the purpose of preventing any lateralA or side thrust of the cams against the parts they engage. This inclination of the cams corresponds to the pitch of the threads on the shaft 116, so that the forward movement of the cam 119,-for example, as it approaches the lug 123, is just equal "to the receding movement due to the inclined surface of the cam, and the lug 123 will therefore not be until the end vof the cam rides under it, lifting the arm 112. The slow-down switch 46 is arranged to be operated by the rotation of the rock-shaft 120 every time one of the hoisting drums approaches its limit of movement in either direction.

Referring to Fig. 1, 80 designates the motor which is usedffor both hoisting and lowering, and which always runs in' one direction. The motor receives current from the positive and negative mains (designated and respectively) connected to a suitable source of current supply. 1 and 2 are the magnets which operate, when energized, to close a circuit to the motor 80. 8, 9, 10 and 11 are sections of the motor starting resistance, which sections are controlled by the electro-magnets l12, 13, 14 and 15, re-v is the fast speedmagnet, and 29 is a magnet' which operates to prevent the brake being raised when the motor 80 is at rest. The switch 45 is for the purpose of rendering the speedA controlling switch 33 inoperative whenever desired. 62, 62', etc., designate brake magnets for the various hoisting units, while 63, 63, etc., are the CQrresponding trip magnets. .57 and 58 are the mechanically operated limit stops, 57 being the up limit and 58 the down limit for a single unit: The other units have similar limit. switches, sis/57', 58, etc. 64 and 65 each designate a series of selective push-buttons, six up buttons and sixy down buttons, and all of these buttons are what are known as self-holding buttons, in that when pressed they are held.

in this position against the action of a spring or equivalent means by an electro-magnet. In the system shown there are six up buttons and six down buttons, and the operation of these buttons determines the particular hoisting unit which is to be operated either to raise or lower its load, depending uponl the particular button operated.

The operation of the system of electrical control is as follows Any one of the buttons 64 or 65, or more than one, may be pushed, but for the purpose of illustration we will assume that the right hand button 65 is pushed against the action of the spring 66. It will be observed that the upper magnet windings 69, etc., of both the up and down buttons are all connected in series, and, furthermore, they are directly connected by the wire 60 to the main, and are also connected through the normally closed contacts 55 directly to the -j main. These pushbutton magnet coils therefore receive current directly from the main line through the contacts 55 and are thus energized, and, while the magnet coil of any one button is not of sufficient strength to automatically operate the push-button, it has the necessary power to hold the push-button in closed position after the same has been manually pushed. This button having been pushed,

the contacts 72 are brought into electrical4 engagement with eachother and are held in this positionagainst the action of the spring 66. The hoisting drum corresponding to the button just operated is now in proper relation to hoist its load. The next operation is to move the lever 34 of the manually operated speed switch 33 to the right until the switch lever 34 electrically connects the fixed segmental contacts 43, 42 and 35, the position of slow speed. This operation closes a circuit which is as follows From the main at the junction point 7 7 to and through the magnet 1, wire 81, magnet coil 2, magnet coils 29 and 31, wirev 82, contact 42, switch lever 34, contact 43, switch 45, and by wire 6() to the main at the junction 79. A parallel circuit is also closed 'atY the same time from the contact 42, switch lever 34, contact 35, contact 51, the bridging contact 50, and by the wire 83, to the main at the junction 78. By thus closing a circuit through the magnet coils 1, 2, 29 and 31 in Series, the same become energized and operate to close the contacts associated therewith, namely, tliecontacts 6, 7, 30 and 32, respectively. A circuit is now closed to the motor armature through the contacts 6 and 7 including the sectional starting resistances 8, 9, 10 and 11. At the same time a circuit is closed to the motor field winding 4, this circuit being from the -lmain at the junction 84, magnet winding 54, motor.lield 4, wire 85, contacts 32, wire 86, and so to the main by way of contacts 7. The motor 80is now enabled to start, the current flowino' to the armature being limited by the sectional starting resistances 8, 9, 10 and 11 in series therewith. Upon closing the contacts 6 and 7 a circuit is established through the 'slow-down limit switch 46 and the magnet coil 48, and the latter becomes energized to raise the contact plate 52 into electrical engagement with the stationary contacts 53, also the contact plate 50 out of engagement with the fixed contacts 49 and 51. circuit vbefore mentioned through the magnet coils l, 2, 29 and 31 from the contact 42, switch lever 34, contacts 51, 50, and wire 83 to the main. The circuit to these magnets remains completed, however, through the contacts 42 and 43 as before pointed out.

The magnets 26, 27 and 28 are connected in series, and at this time are connected across the motor armature, the circuit being as follows :-From the motor brush 3, wire 87 and normally closed contacts 56, through the magnets 28, 27 and 26 to the contact 35 of switch 33, contact 43, switch 45, wire 60, contacts 7 to the motor brush 3. At the moment of starting the motor from a position of rest,

the voltage across the motor brushes 3 and 3 is at a minimum, which voltage increases as the motor increases in speed, due to the C. E. M. F. of the revolving armature, and,

Vsince the magnets 26, 27 and 28 are connected across the motor brushes, the current flowing in these magnets is proportional to the brush voltage of the motor. If the` motor is heavily loaded upon starting, the voltage across the armature brushes Ywill remain relatively low, due to the fact that the motor will run at a low speed with consequent low C. E. M. F., the greater part of the drop of potential taking place across the starting resistances 8, 9, 10 and 11. With the present conditions, however, since but a single unit is hoisting, the load is comparatively light and the voltage across the motor armature soon rises to a point sufliciently great to effect the operation of the magnets 26, 27 and 28. The operation of the magnet 28 closes the contacts 25, which connects the resistances 20, 21 and 22 in parallel to the motor armature. The magnet 27 operates to shortcircuit the resistance 22, leaving the resistances 20 and 21 in parallel to the armature; while the magnet 26 short-circuits the resistance 21, thereby leaving'the resistance 20 alone across the armature, and under no conditions in this resistance 20 ever short-circuited. The conditions at this time are for slowest speed, that is, the resistance in series with the motor armature is at a maximum, the field strength is also at a maximum, and the resistance in parallel with the armature is at a minimum.

At substantially the same time that the motor receives current by the operation of the magnets 1 and 2, the magnet 29y which is included in the circuit of these magnets closes a circuit from the main through This opens the parallelV ing the push-button in operative position.y

The brake magnet and tripping magnet being both energized at this time, the hoisting apparatus is in properV condition to eifect the raising of the load as before pointed out. The magnet 54, it will be remembered, is included in the circuit of the motor eld winding 4, and the same current passes through both. Since the current in the motor ield 4 does not instantaneously rise toits full value as soon as its circuit is closed, due to the selfinduction of the field winding, the magnet 54 does not immediately operate to separate the contacts 55 -and thus break the circuit through the upper magnet windings 69 of the series of push buttons. This arrangement insures that the lower magnet winding 71 of the operated push-buttons will become fully energized by the operation of the magnet 29 before the magnet 54 has operated to open the circuit of the upper push-button windings, and the push-button remains in its operative or closed position.

The switch lever 34 is next moved until it passes onto contact 36 and o of contact 35. The circuit to the magnet 26 -is now opened at the contact 35, but the circuit to the magnets 27 and 28 is still closed through the contact 36. The magnet 26 therefore becomes denergized and opens the contacts 23, inserting the resistance 21 in the parallel circuit to the motor armature. This increase in resistance across the armature circuit results in an increase in motor` speed. Upon further movement of the switch arm 34 onto contact 37, the circuit to the magnet '27. is opened at the contact 36, while the magnet 28 alone remains energized. The circuit across the armature now includes the resistances 20, 21 and 22 andthe motol` further increases its speed. The lever 34is now moved onto contact 38 and oi of contact 37. This opens the circuit to the magnet 28 at,y the contact 37, causing the same to open its contacts and thereby opening' the parallel circuit to the armature at the contacts 25 and themotor further increases its speed. Since the switch arm 34 now rests upon the contact 38, the magnet 12 including the'resistance 74 is connected across the motor armature, this circuit being traced as follows :-From the motor brush 3, wire 87, contacts 53 (these latter being in electrical engagement with each other/at this time), through the magnet winding 12, wire 68, resistance 74, contacts 38 and 43, switch 45, wire 60, contacts 7, and to the armature brush 3. l The magnet 12 now receives curl a short circuit across the sectional starting resistance 8. The motor now runs still faster with but one-half of the starting resistance in circuit.'

When the magnet 13 operated to close the contacts 17, the'contacts 56 were separated at substantially the same time, thus preventing any possible circuit to the magnets 26, 27 and 28 through the wire 70 as long as the magnet 13 is energized. The switch arm 34 next moves onto contact 40, thereby energizing the magnet 14 through the resistance 76, thereby cutting out or short-circuiting the sectional resistance 10. The switch arm is now moved onto contact 41 which completes a circuit through the magnet 15 which operates to short-circuit the' remaining starting resistance 11. The ohmic resistance of each of lthe resistances 74, 7 5 land 76 is so proportioned that the current strength in any one of the magnets 12, 13, 14 or 15 is the same for the same motor potential whether one magnet alone is in circuit or all of the magnets; that is to say, the ohmicvresistance ot the resistance 74 is equivalent to three times that of any one of these magnets, that of the resistance 75 to twice the mao'net resistance, while that of resistance 76 is the same as the resistance of one of the magnets. These magnets 12, 13, 14 and 15 are preferably so arranged that should the switch arm 34 be rapidly moved from its initial position to the contact 41, the magnets will respond to the rise of motor potential as the same speeds up and will operate successively in prearranged order so as tofsh'ort-circuit the sectional starting resistances in proper order. This may be accomplished in one of several ways well known in the art and needs lno further description. The motor now receives current at full line potential with maximum field strength and assumes a speed to correspond therewith. The switch arm is next moved until it rests upon the segmental contacts 4l, 44 and 43. The circuit to the magnets 12, 13, 14 and 15 remains unbroken, but a circuit to the magnet 31 isopened through the wire 82 at the contact 42. The circuit including the magnet 29 is not interrupted, however, since an additional circuit is closed through the contact 44 and resistance 73, which resistance is now substituted for the magnet 31. The magnet 31 nowbecomes denergized and the contacts 32 controlled thereby move out of electrical engagement with each other. This results in placing the resistance 5 in series with the motor field winding 4, since the short-circuit heretofore maintained across the resistance 5 by the contacts 32 and wires 85 and 86 is now opened through the separating of these contacts. By thus inserting the resistance 5 into the motor field circuit, the cur- Y rent flow in the latter is reduced, the field strength is therefore weakened, and the motor and connected hoisting unit run at full speed. As the load carried by this hoisting unit approaches its upper limit of travel, the mechanically operated slow-down switch 46 which is operated every time one of the hoisting drums approaches its limit of movement in either direction, opens the circuit to the magnet 48 at the contacts 47. This magnet at once becomes denergized, causing the contact plate 52 to move out of engagement with the contacts 53, and the Contact plate 50 to electrically engage the contacts 49 and 51. This operation opens the circuit to thema ets 12, 13,- 14 and 15 at theV contacts 53 an 'the entire starting resistance is re-inserted into the armature circuit, while the contacts 56 are once more placed in electrical contact .with each other. The denergization of the magnet 48 also connects the contacts 49, 50 and 51 together, thereby closing two circuits, one of which is from the motor brush 3, wire 87, contacts 56, wire 7 O, magnets 28, 27 and 26, wire 91, contacts 51 and 50, wires 83 and 92, contacts 7, to the motor brush 3'; the other circuit is from the right-hand terminal of the motor field winding, wires 85 and 90, contacts 49 and 50, wires 83 and 9,2, to the main. The first-named circuit effects the operation of the magnets 26, 27 and 28 which will operate to connect the resistance 20 across the armature. The second-named circuit effects the shortcircuiting of the resistance 5, both terminals of which are now connected to the main and the motor field Y,strength is again at a maximum. The effect of these operations is to slow the motor down to extreme slow speed. The hoisting unit has at this time raised the -load tol its upper limit and the mechanically operated limit switch 57 automaticallyoperates to open the circuit through the'brake magnet 62, tripping magnet 63, and push -button magnet 71. The hoisting drum of the unit corresponding to the push-button operated now comes to rest and the spring 66 returns the button to its initial position as shown on the drawing. The motor continues to run, however, at reduced speed until the slow-down mechanism operates to electrically connect the contacts 47, thereupon the magnet 48 1s '1'30 established to the magnets 12, 13, 14 and 15 and the circuit through the magnets 26, 27 and 28 is opened, while the short-circuit around the field resistance is removed and the motor automatically runs up to full speed.

Should it be desired to operate two or more hoisting units at t-he same time, the push-buttons corresponding to the desired hoisting units may be pressed, after which the motor is started and run up to speed by the switch 33. The slow-down switch 16 operates automatically to slow the motor as any one of the hoisting units nears its limit of travel, afterwhich the limit stop corresponding to such hoisting unit which has reached its limit of travel operates to bring such unit to rest. The slow-down switch again operates so as to speed up the motor, and, as another hoisting unit nears its limit of travel, the motor is again automatically slowed down until such hoisting unit reaches its limit of travel and the same is brought to rest, after which the motor again speeds up. This operation continues as long as there are any hoisting units operatively connected to the driving motor.

When it is required that any oneor more hoisting units shall operate to lower their load, the corresponding down buttons are pushed. The various operations of different parts are similar to the operations already described in connection with raising one or more loads, with this eXceptiom-when a down button is operated and the switch 33 is moved so as to start the motor, the circuit closed through the lower magnet winding of the push-button includes the magnet winding of the corresponding brake and down limit switch, but does not include the corresponding tripping magnet and the latter is not energized, consequently, while the brake will be released, the tripping mechanism will not ermit the hoisting drum to be operative y connected to the friction driving disk on the motor shaft. The unbalanced load will, however, since the brake is released, cause the hoisting drum to turn backward, thereupon operatively connecting the hoisting drum through its corresponding clutch mechanism and sprocket to the cooperating sprocket mounted upon the motor shaft, and in this manner the lowering, as well as the raising, of the load is dependent upon the motor speed which may be varied within wide limits by means of the manually operated switch 33.

rlhe operation of the slow-down and limit devices is similar,.whether the load is being raised or lowered, and while a single switch is used to controll the slowing down of the motor, whether the same is hoisting or lowering, aseparate limit switch is used for the up and down motions. It is not necessary first to operate the push-buttons aQnd then start and accelerate the motor, but, if desired, the motor may be started and run at any desired speed within the capacity of the machine, and then any desired up or down button may be pressed, the hoisting unit corresponding thereto will raise or lower its load and automatically slow down, and inally stop at its limit of travel.

In the system of electrical control just described where the different hoisting units ar'e hoisting and lowering at the same time, it is not possible to change the speed of hoisting without changing the speed of lowering as well. The system of electrical circuits illustrated in Fig. 2, in which two motors are used, one for hoisting and one for lowering, makes it possible to vary the hoisting or lowering speeds at will independently of each other.

Referring to Fig. 2, 80. designates the hoisting motor and 80 the lowering motor. The motor 80 is preferably of greater power than that of motor 80', for the reason that the unbalanced load upon any hoisting unit, when the same is operating to raise or lower its load, has to be raised against gravity in the case of hoisting, but assists the lowering motor .80 when it is being lowered.V In actual practice it is found that the motor 80 is driven by thennbalanced descending load, and thus the motor acts as a generator, sending current back into the line and thereby providing an electro-dynamic brake of variable retardation.

The operation of the electrical system of control is substantially the same in Fig. 2 as in Fig. l. It will be noticed that the starting resistance for the hoisting motor 80 comprises tive sections controlled by five magnets 12, 13, 14, 15 and 15', also the armature parallel resistance has but two sections controlled by a corresponding number of magnets 26 and 27. The speed ofthis motor 80 is controlled by the switch 33 in a manner similar to that pointed out in connection with Fig. 1. The up limit switches 57, 57, etc., and the down- limit switches 58, 58, etc., operate in like manner to bring any particular hoisting unit or number of units to rest as soon as each individual hoisting unit has reached its limit of travel. The same main line switch 93 supplies current to both motor controlling systems from a suitable source of electrical supply indicated by the and signs. It will be further noticed that in Fig. 2 there is no slow-down magnet for the hoisting motor. A slowdown magnet is, however, provided for the lowering motor 80 and is operatedautomatically by the slow- down switches4 46, 46, etc., whenever any one of the hoisting units has operated to lower its load by means of the motor 80 almost to its lower limit of travel, shortly after which the corresponding limit switch comes into action and brings the load to rest. The motor 80 is immediately'speeded up automatically until another curtam approacheslits lower limit of travel and the same cycle of operations is repeated as long as there are any hoisting units actively engaged in lowering. The speed of the hoisting and lowering motors 80 and 80 is controlled independently controlling switches 33 and 33, respectively. In this manner when the hoisting apparatus is used to operate theaterI curtains, certain curtains may be rapidly raisedv while at the same time other curtains may slowly descend, or the Jreverse may be the case, and in this manner many -beautiful scenic effects ma bewproduced at will: The slowing down an consequent stopping of all of the curtains upon reaching their. limitv of travel is accm lished automatically.

' Whi e I have illustrated and described the preferred 'form of my invention, I do not wish to be limited to the precise construction and arrangement of parts shown,`since it is obvious that various changes could readily be made in the constructlon and arrangement of parts by lthose skilled in the art without departing from the spirit and scope of my invention.

What I claim as new and desire to protect by Letters Patent of the United States is 1. In a system of electrical control, the combination withv a source of current supl ply, of an electric, motor, controlling 'devices'for the motor, a plurality of electromagnets, and selective devices operative respectively to effect the energization of one or both of said electro-magnets.

2. In a system of electrical control, the combination with a source of current supply, of an electric motor, motor controlling l `nrechanism', a brake magnet, a` trip magnet,

andgmeans for effecting the energlzation of either the brakemagnet alone or both the brakemagnet and trip magnet when current 3. In a system of electrical control, `the Acombination with Aa motor, of a source of -current sup ly, motor controlling mechanism, a-pllira ity of electro-magnets, and. de- Vices -for effecting the energization of said' magnets when current isv supplied to the motor, one of said devicescontrolling one of said magnetsand the other of said devices controlling both of said magnets.

'4. In a system of eleb 'cal "control,the

l combination with a source f current supply, -of an electric motor, controlling mechanism for. the motor, a brake magnet coil, a trip y, bsma'gnet coil, a circuit for the brake magnet l K therefor, a brake magnet coil, a tripmagnet coil, circuits for said coils each open at a plurality of points, selective devices for manually closing each'circu/it at one point, and means for automatically com leting said circuits when current is supp ied to the motor.

6. In a system of electrical control, the combination with a source of current supply, of an electric motor, controllin mec anism therefor, a brake magnet coi a circuit therefor normally open at a plurality of points, a manual device for closlng the circuit at one point, and means for automatically completing said circuit when current is supplied to the motor.

7. In an electrical System of control, the combination with a source of current supply, of an electric motor, a manual con= trolling switch therefor, a brake magnet coil, a manually operable switch in the circuit of said coil, an electro-magnetic switch in said circuit, and means for operating said `electro-.magnetic switch when the controlling switch for the motor is operated.

8. In an electrical system of control, the combination with a source of current supply, of a motor, controlling ineans therefor, a plurality of brake magnet coils, atrip magnet coil associated with each brake magnet coil, selective devices controlling the circuits of the brake magnet coils alone,-and selective devices controlling the circuits of the brake and trip coils together.

9. In a system of electrical control, the combination with a motor, of controlling apparatus therefor, a bank of pushbutton switches comprising a double series of electro-magnets, a series of devices controlled by said switches, a normally closed circuit for one series of said electro-magnets, means for opening said circuit when the motor circuits are closed, an additional circuit for said second series of electro-'magnets open when the motor circuits are open, and means for closing saidY second circuity when the motor circuits are closed.

In testimony whereof, I have signed my name to this specification in ,the presence of t`wo subscribing witnesses.

f ANDREW M. COYLE. Witnesses:

' ,SAMUEL D. CoLLErr,

ANNA-ASHT0N.

Images