US1771464A - Control system - Google Patents

Description

July 29, 1930.

A. PINTO CONTROL SYSTEM Original Filed April 2, 1926 2 Sheets-Sheer. l.

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CONTROL SYSTEM original FiledApril 1926 2 sheets-sheer 2 m2 FIGB www Fidi' mvenron l BY ArToRNEY Patented July 29, 1930 UNlTEDsTATl-:s

PATENT OFFICE ANTHONY PINTO, OFNEW YORK, N..Y., ASSIGNOR TO OTIS ELEVATOB COMPANY, 0F JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY coN'raor. SYSTEM OriginalA application led pril'2, 1926, Serial No. 99,259. Divided and this application filed October 7, 1927. Serial No. 224,652.

The invention relates to control systems, and particularly to control systems for elevators. y

This application is a division of apphcation Serial No. 99,259, liled April 2, 1926.

As theart of elevators has developed, various improvements have greatly increased the efficiency of operation of the elevator systems over those of the earliest types. Among these improvements have been those designed to reduce the time required to etfect the completion of certain operations. One operation in which time is an important factor, particularly in high speed elevator systems, is that of bringing the car to a stop at the landings. Where time is lost in making each stop, it will be seen, upon consideration of the total timelost during a days operation or even during a single round trip, that the operatin efficiency of the system as a whole is consi erably impaired. Self-leveling mechanism, which has been provided in many elevator systems in recent years for bringing the car to a level withthe desired landing in stopping, regardless of whether it underruns or overruns the landing, has for `one of its features a reduction inthe time required to bring the car to an accurate stop at the landing. a

Vhere self-leveling apparatus isemployed in elavator systems wherein a direct current electric motor is used for raising and lowering the car and wherein power is supplied to the motor from a direct current variable voltage generator, the control of the field strength of the generator must be such that the E. M. F.

generated may be rapidly brought to the desired values for obtaining the various leveling operations. Upon the occurrence. ot' an overrun in such systems, it is advantageous to reverse thel polarity of the E. M. F. generated to effect the return of the car to the landing. This is true also in systems wherein the leveling apparatus is omitted, such as those in which the stopping operation is automatic and which are arranged for inching the car back to the floor in the, event that it has run past and those in which the starting, stopping and reversal ofthe car is under manual control. Furthermore, the reversal of the generator E. M. F. is advantageous' for ei'ecting a reversal in the direction of movement of the car at any point in the hatchway. Considerable time may be lost in effecting the reversal of the generator E. M. F.,however, due to the time constant of the generator field.

i One feature of the present invention resides in minimizing the time required to bring the generato-1' E. M. F. from a certain value of one polarity to a certain value of the other polarity. v

AOther features and advantages will become apparent from the following description and appended claims. f e

The invention will be described, by way of illustration, as embodied in a system in which both the starting and stopping of the car under the control of an operator. It is to be understood, however, that it is also applicable to other elevator systems, such as those in which push button control is employed for causing both the starting and stopping of the car or for causing only the stopping of the car, or those in which the starting ot the car is under the control of an operator while the slow down and stopping is automatic. Furthermore, the system in which the invention is embodied will be described, also by way of illustration, as provided with selfleveling mechanism, with the invention applied to the leveling operations. It is to be further understood, however, that the invention is adaptedr for use in other operations, such as the operation of reversing the car at any point and is applicable to systems in which self-leveling apparatus is not employed, such as those in which the accuracy o1"- the stop is made de pendent upon the skillr of the operator and in which, in the event oi' an overrun, the return to the floor is caused by inching, or to those in which the car is caused to stopfauxomatically at the landing and in which means are provided for inching the car back to the ioor in the event oitr an overrun.

The invention involves thepolarity of one portion of the generator separately excited field winding being reversed with respect to that of another portion. This cau-ses the magnetizing forces of these portions to act in 0p position. Then by varying the magnetizing force of either or each of said portions, the net magnetizing force of the winding may be caused to be such that an E. M. F. of either polarity may be obtained, the particular polarity depending upon which one of said portions predominates.

In carrying out the invention, according to the preferred arrangement, certain connections in the generator separately excited field winding circuit are changed for the leveling operation so as to cause the current in a porA tion of the field winding to flow in a reversed direction with the direction of the flow of current through the remainder of' the winding remaining the same. Upon an underrun, the current flowing through said portion is caused to be less than that flowing through the rcmainder of the winding with the result that an M. F. of proper polarity is generated. Upon an overrun, in order to reverse the polarity of the E. M. F. generated so as to effect the return of the carto the landing, the direction of the flow of current through the whole winding is not ieversed but the current flowing through said portion is caused to be greater than that flowing through the reA mainder of the winding.

Other conditions arise, where a variable voltage direct current generator is. employed to supply power to the elevator motor, which tend to cause variations in operation during the leveling period. During this period, the generator is required to operate at low values of' E. M. F. in order to obtain satisfactory operation for bringing the car to a level with a landing. Due to the residual flux of the genT erator field, assuming the generator sepa.-

rately excited field winding connected the.

same for leveling as for operation between floors, the E. M. F, values obtained vfor ay given value of field current during the. leveling period vary considerably, depending onthe magnetic state of the machine prior t-o level'- ing and whether the car is'. being broughtto.

the landing upon an underrun or returned to the landing after an overrun. Such variations in E. M. F. values cause undesirable variations in the operation of the car during the leveling period. The preferred arrangement of the invention also obviates the eliects of the residual flux of the generator and thereby causes more uniform operation dur ing the leveling period. I

A system of control directed to similar subject matter is shownin this inventor"s copending application, Serial No. 60,769, filed October 6, 1925, and division thereof, Serial No. 273,290, filed April 27, 1928.

In the drawings.:

Figure 1 is a diagram of an elevator control svstem embodying the invention;

y Figure 2 is a fragmental schematic view of a `portion of the elevator system, lllustrating particularly the manner 1n which the generator field winding is controlled during the leveling operation; and

Figure 3 is a hysteresis curve employed to illustrate the invention.

No attempt is made in Figure 1 to show the coils and contacts of the various electromagnetic switches in their associated positions, a straight diagram being employed wherein the coils and contacts of the various switches are separated in such manner as to render the .f

circuits involved relatively simple. Also the parts of other switches and apparatus are separated in the interest of simplifying the diagram. For a clearer understanding of the invention, the stationary contacts of the I switches are illustrated in cross section.

The motor generator set comprises a driving motor 11, illustrated for convenience of description as of the direct current type, and a variable voltage direct current generator 12. The armature of the driving motor is designated 13 and its field winding 14. The armature ofthe generator is designated 15, its series field winding 16, its separately excited field winding being divided into two portions 17 and 18. The elevator motor is designated as a whole by the numeral 20, its armature being designated 21 and its field winding An adjustable resistance 23 is arranged in shunt to the generator series field winding. Discharge resistances 24 and 25 are provided for the portions 17 and 18 respectively of the generator separately excited field winding. Discharge resistance 26 is provided for the elevator motor field winding. A. resistance 27 is provided for controlling the strength of the generator field and therefore the voltage applied to the elevator motor armature. A resistancey 28 is provided for controlling the relative values of the current supplied to the generator field winding portions 17 and 18 during leveling. 30 is the release coil for the elevator motor electromagnetic brake. This coil is provided with discharge resistance 31 for controlling the application of the brake during the stopping operation. 32 and 33 are the up slow speed contacts and the down slow speed contacts respectively of the leveling switch, the up and down fast speed leveling switch contacts being designated 34 and 35 respectively. 36 is the armature and 3T is the field winding of the motor 38 for moving the rollers of the leveling switch into position to clear the leveling cams. 40 and 41 are the direct current supply mains. 42 is a double pole knife switch for connecting the system to the supply mains. In order to suit the type of' diagram employed, the blades of this switch are shown separated. The car switch is designated as a whole by the numeral 43. 41 is the safety switch in the car. The various safety, limit, stop and emergency switches anddoor and gate contacts are omitted in order to simplify the description.

The electromagnetic switches have been designated as follows: y

A--potential switch,

B-up direction switch,

C-down direction switch,

F-v-accelerating switch,

(ir-maintaining relay, H-brake switch,

L-'field control switch, l

' M-series field relay,

N--series field switch,

P-leveling switch motor relay,

LU--up leveling direction switch,

-LD-down leveling direction switch,

LR-field control leveling relay,

LIL-fast speed leveling relay,

LI-intermediate speed leveling relay.

- Throughout the description which follows, these letters, in addition to the usual reference numerals, will be applied to the parts ofthe above enumerated switches.` For example, contacts B 66 are contacts on the up direction. switch, while actuating coil A is the coil that operates the potential switch.' The electromagnetic switches are shown in their deenergized positiona/ Inductance coil are similarly designated by the characterk f Upon the closing of the knife switch 42, the driving motor 11elevat0r motor field Winding 22 and potential switch actuating coil A 45 are energized, the circuit for coil A 45 being by way of line 46including safety switchv 44. The driving motor starts in. operation, bringing the generator 12 up to full speed. Starting means for the driving motor are omitted to simplifythe description. The potential switch, upon operation, causes the engagement ofcontacts A and A 51 preparing the circuits for the generator separately excited field winding and the electromagnetic brake release coil and also the control circuits. The condition of the circuits sok far described might be termednormal.

`Assume that the system is designed for an installation of several floors and that the carv is at rest. atthe first floor landing. In order to, start the car in the up direction, the operator moves the car switch into position where its contact kbar 52bridges contacts 53, 54, 55 and 56. Uponthe contact bar 52 engaging contact 54, a circuit is completed for the actuation coil B 57 of the up direction switch and the actuating coil H 58 of the brake switch. This circuit may betraced from the left-hand blade ofk switch 42, by Way of line 79 through contactsA 50, by way of line 60 through coils H 58 and B 57, contacts 54 and 53 of theA car switch. by way of line 61 through contacts C 62, line 63, switch 44, line 46, by way of line 89, to the right-hand blade of switch 42. The engagement of the contact bar 52 and contact 55 prepares a circuit for the `actuating coil F 830i the accelerating switch. The engagement of the It is preferred to provide the direction switches with a mechanical interlock to prez vent their simultaneous operation. Such an interlock may be of the form of a walking beam pivotally mounted for engaging i n catches on the armatures of the direction switches. Upon operation of the up direction switch in response to the energization of its actuating coil B 57, contacts B 65 separate and contacts B 66, B 67 and B 68 engage. The separation of contacts B 65 breaks the circuit leading from the car switch down feed contact 70, contacts B 65 and the corresponding down direction switch contacts C 62 serving as electrical interlocks. The engagementof` contacts B 68 prepares the circuit for the up direction switch holding coil B 71 and the brake switch holding coil H 72. The engagement of contacts B 66 and B 67 coninletes a circuit for the generator separately excited field winding. This circuit may be traced from the left-hand blade of switch 42, by way of line 79 through contacts A 50 and resistance 27, by way of line 73 through contacts B 66, by way of line 74, through field control switch contacts L 120, field winding portion 18, by way of line 121 through contacts L 122, field winding portion 17 and actuating coil G 75 of the maintaining relay, by way of line 89 through contacts 67 and contacts A 51, to the righthand blade of switch 42. Relay G does not operate at this time as insufficient current is supplied to its actuating coil.

The brake switch H operates simultaneously with the direction switch B. Switch H, upon operation, causes the separation of contacts H 77 and the engagement of contacts H 80 and H 81. The separation of contacts H. 77 disconnects the generator separately excited field winding from the generator armature. The purpose of contacts H 77 will be seen from later description. The engagement of contacts H 8O completes the circuit for the brake release coil 30. This circuit may be traced from the left-hand blade of switch 42, by way of line 79 through contacts A 50, by way of line 82 through coil 30 and contacts H 80, by way of line 89 through contacts A 51, to the right-hand blade of switch 42. The engagement of contacts H 81 completes the circuit for the accelerating switch actuating coil F 83. This circuit may be traced from the left-hand blade of switch 42, by way of line 7 9 through contacts A 50, by way of line 84 through contacts H 81, contacts L 47, inductance coil X 85 and coil F 83,

contacts and 53 of the car switch, by way ci line 61 through contacts C 62, line 63, switch le, line 16, line 89, to the right-hand blade of switch 42.

The leveling switch motor relay, upon operation, causes the engagement of contacts P 98, completing the circuit for the leveling switch motor 88. This circuit may be traced from the left-hand blade of switch 42, by way of line T9 through contacts A 50, by way o1 line 9-1 through armature 86 and field winding 8T ot' motor 88 and contacts P 98, by way ot line 89 through contacts A 51., to the right-hand blade or" switch 42. The leveling switch motor acts to move the leveling switch operating rollers so as to clear the leveling cams during the movement of the car. This operation will be explained later.

The brake release coil being energized and current being' Supplied from the generator armature 15 to the elevator' motor armaturc 2l, due to the generator' lield winding portions 1T and 18 being energized, the elevator motor starts. The lield winding portions 1T and 18 as now connected assist each other.

The accelerating switch F docs not operate immediately the circuit for its actuating coil F 83 iscompleted, its action being delayed by the inductance coil X 85. Upon operation, switch F causes the separation of contacts F 8T and the engagement of contacts F 88 and F 90. The separation oi contacts F 8T removes the short-circuit around the holding coil P 91 of the leveling switch motor relay. The engagement ot contacts F 88 completes the circuit for holding coils B 71, P 9'l'and H T2. This circuit may be traced from the left-hand blade ot switch 42, by way of line 79 through contacts A 50, by Way of line 95 through coil B 71 and contacts B 68, by way of line 96 through coils P 91 and H 72 and contacts F 88, by way of line 89 through contacts A 51, to the right-hand blade of switch l2. The purpose of the energization of these holding coils will be seen from later description. The engagement of contacts F short-circuits resistance 2", increasing the voltage applied to generator field winding portions 17 and 18. Thus the generator voltage is brought up to its full value and the motor comes up to full speed. Also sufficient current is now supplied to the coil G 75 to cause the operation of the maintaining relay. Thus contacts G 97 engage, by-passing accelerating switch contacts F 88. It is to be understood that several accelerating switches may be employed to short-circuit successively sections of resistance 2T, all but one, illustrated as Short-circuiting the whole of the resistance, being omitted in order to simplify the description.

The starting of the car in the down direction is accomplished in a similar manner and will be only briefly described. The operator moves the car switch into position where its contact bar 52 bridges contacts 70, 98, 100 and 101. Upon the engagement of the contact bar and Contact 98, a circuit is completed for the down direction switch actuating coil C 102 and coil H 58 which circuit may be traced from the left-hand blade of switch 42, through coil 58, as previously traced, by way of line 103 through coil C 102, car switch contacts 98 and 70, by way of line 63 through contacts B 05, to the right-hand lade of switch 42 as previously traced. The engagement of the contact bar and contact 100 prepares a circuit for coil F 83 and the engagement of the contact bar and contact 101 completes a circuit for the coil P 59 by way of line 104. The down direction switch, upon operation, causes the separation of contacts C 62 and the engagement of cont-acts C 105, C 106 and C 107, these contacts corresponding with up direction switch contacts B 65, B 66, B 67 and B 68 respectively. The holding coil of the down direction switch is designated. C 64. The circuit for coil F 83 is completed by contacts H 81 as before. Further than this, the operation of starting the car in the down direction is the same as described for starting it in the up direction.

Assume that the car is running in the up direction and that the operator centers the car switch between the second and third oors in order to stop at the third floor landing. Upon the disengagement of the contact bar 52 and Contact 56, the circuit for the leveling switch motor relay actuating coil P 59 is broken. The relay remains in operated condition, however, due to its holding coil P 91. The disengagement of contact 55 and the contact bar breaks the circuit for thev accelerating switch actuating coil F 83. The ac` celerating switch, therefore, drops out, causing the separation of contacts F 88 and F 90 and the engagement of contacts F 87. The separation of contacts F 88 is simply' in reparation for the next starting operation, t ie circuit for coils B 71, P 91 and H72 being maintained by contacts G 9T. The separation of contacts F 90 removes the short-circuit for resistance 2T, decreasing the strength of the generator field winding portions 1,7 and 18. Thus the generator' E. M. F. is decreased and the speed of the elevator motor is reduced. Discharge resistances 24 and 25 act to smooth out the retardation. The engagement of contacts F 87 short-circuits the holding coil P 91 of the leveling switch motor relay. The disengagement of contact 54 and contact bar 52 breaks the circuit for actuating coils B 57 and H 58. The up direction switch and brake switch are maintained in operated condition, however, by their holding coils B 71 and H 72 respectively.

The leveling switch motor relay P, dropping out upon lthe short-eircuiting of coil leveling switch are extended vided for each floor.

LR 117. the, left-hand blade of switch 42, by way of P 91, causes the separation of contacts P 93 to deenergize the leveling switch motor 38. In this manner the opcratin rollers of the or engagement by the leveling cams. Referring to Figure 2, the leveling switch motor is operatively connected tothe leveling switch by means of an arm 108 on the motor shaft, a connecting link 110 and a lever 111. In the starting operation., the motor 38 being energized, arm 108 rotates, acting through link 110 and lever 111 to move the leveling switch as a whole about a. pivot.` In this manner the leveling switch operating rollers 112 and 113 are moved into position where they do not engage the leveling cams 114 and 115 during motion ol theA car, a stop being provided to determine the extent of the movement. It is to be understood that leveling cams are pro- Tlie leveling switch is pivoted on a bracket 116 secured to the car frame. In the stopping operation, upon the deenergization of the leveling switch motor, a spring (not shown) moves the lever 111 and ihereforc the leveling switch back into the first described position with the rollers 112 and 113 extended for engagement by the leveling cams. Each pair of leveling contacts 32, 33, 34 and 35 comprises a stationary Contact an-:l a movable contact operated by the engagement of its corresponding roller and leveling cam. `The fast speed contacts 34 and 35 are arranged to separate before their corresponding slow speed contacts 32 and 33 in the leveling operation. Springs (now shown) are provided for causing the selniration'olI the contacts of the pairs asthe leveling operation is effected and stops are provided ifor determining the extent of movement of the rollers as they ride ol` the leveling cams.

It will be assumed that the ear has notv r "ached the landing and that the up leveling switch operating roller 112 moves onto the i vertical surface of up leveling cam 114 before relay7 (if drops out. Referring to Figure 1 and also to Figure 2 where portions of the circuits employed for leveling are illustrated and where the coils and contacts of the par ticular switches included are illustrated in their proper associated relations, the engagement of leveling switch up slow speed contacts lcompletes a circuit for the up leveling direction switch actuating coil LU 78 and the field control leveling relay actuating coil This circuit may be traced from line 79 through contacts A 50, line 124, leveling switch contacts 32, by` way of line 125 through coil LU 78 and coil LR 117, by Way of line 89 through contacts A 51, to the rightliand blade of switch v42.r The engagement of the leveling switch up fast speed contacts 34 completesthe circuit for fast speed leveling relay actuating coil LF 130. This circuit completed.

may be traced from the left-hand blade of switch 42, by way of line 79 through contacts A 50, line 124, leveling switch contacts 32, by way of line 131 through leveling switch contacts 34, by way of line 132 through coil LF 130 and resistance 133, to the right-hand blade of switch 42 as previously traced. It is to be noted that, due to the fact that the circuit for coil LF 130 is through leveling switch slow speed contacts 32, the circuit for coils LU 78 and LR 117 must be made in or: der that'the circuit for coil LF 130 may be The field control leveling relay LR, upon operation, causes the engagement of contacts LR 127, LR y134 and LR 135. The engagement ofcontacts LR 127 completes a discharge circuit around the actuating coil ot the relay, the circuit including dischargeresistance 162 and inductance coil X 126. The engagement of contacts LR 134 completes a circuit forthe up direction switch and brake switch actuating coils B 57 and H 58 respectively, causing their reenergization. This circuit may be traced from the left-hand blade of switch 42, by way of line 79 through contacts A 50, by way of line 60 through coil H 58, coil B 57 and contacts LR 134, by way ofline 89 through contacts A 51, to the righthand blade of switch 42. The reenergization of these coils has no particular eect under the assumed sequence of operation of the switches, however, as the up direction switch and brake switch are being maintained in o perated condition ,by holding coils B 71 and H 72. The engagement'of contacts LR 135 completes the circuit for the actuating coil L 136 of the field control switch. This circuit may be traced from the left-hand blade of switch 42, by way of line 79 through contacts A 50, by way of line 137 through contactsLR 135 and coil L 136,`by way of line 89 through contacts A 51, to the right-hand blade of switch 42.

The field control switch L, upon operation, causes the separation of contacts L 47. L 120 and L 122 and the engagement of contacts L 140. L 141 and L 142. The purpose of contacts L 47 and L 142 willbe seen from later description. The separation of contacts L 120 and L 122 breaks the circuit for portions 17 and 18 of the -generator separately excited field winding. The immediate engagement of contacts L 140 and L 141. however, reconnects these portions to the mains. Thepolaritv of thelatter connection is such that the direction of the flow of current through portion 18 is reversed while the direction of the flow ofV current through winding portion 17 remains the same. As a result of this change of connections, the magnetizing force due to winding portion 18 opposes that'due to wind. ing portionl. .As above set'forth, however, actuating coil LU 78 of the'fup leveling direction switch was energized upon the engagement ot the levelingswitch slow speed contacts 32. This switch, operating along with relai7 LR, causes the engagement of contacts LU 144. Thus, as the field control switch operates to reverse the connections for field winding portion 18, switch LU operates through its contacts LU 144 to connect a portion of resistance 28 in parallel with this winding portion so that the current in portion 18 is less than that in portion 17. The magnetizing torce due to portion 18, therefore, is less than that due to portion17.

As previouslyr set forth, fast speed leveling rela)1 actuating coil LF 130 was energized by the engagement ot up fast speed leveling contacts 34. 'l This relay, upon operation, causes vthe separation ot contacts LF 145 and the engagement ot contacts LF 146. The purpose .oflcontacts LF 145 will be explained later.

The Aengagement of contacts LF 146 shortcircuits a portion ot resistance 28. Thus, under the assumedsequence ot operations. the Afast speed leveling relay is effective to determine the amountof resistance 28 which is connected across field winding portion 18 b v the engagement ot contacts LU 144, this amount ot resistance being indicated as adjustable section 147.

The engagement of lield control switch contacts L 142 short-circuits a portion of resistance 27 tor the generator separatelv excited lield winding, the amount of resistance in this portion being adjusted to give satis- `tactorvoperation for the particular installation. .lVith contacts L 12() and L 122 separated and contacts B 65,13 (i7, L 140, L 141, lL 142, LU 144 and vLF 146 in engagement, an E. M. F. is generated which causes thc elevator motor to run at a suitable fast leveling speed inthe up direction as will be seen from later description.

Discharge resistances 24 and 25 act to smooth out not onlv the change in generator E. M. F. due to the reinsertion of resistance v27 in circuit with the field winding but also that due to the above described change in connections tor effecting the leveling operation.

.t is to he noted that the separation ot contacts L 120 and L also breaks the circuit tor the actuating coil G "Z of theinaintaining relav. Rela: therefore, d ruppe-fl out touseparate contactsy G 97. breakin@- the circuit tor holding coils B 71 and H fr, ot the up direction switch andthe brake switch re- I spectively, These switches were maintained.

in operated condition, however, b v their actuating coils, the engagement ot contacts LR 4184 causing the reenergization of these coils as previously explained. Relai-v G is maintained operated atte-r contacts F 90 separateto remove the short-circuit for resistance 27 because of theiiact that the current through its actuating coil is sustained br the action of ield winding-portion 17 and discharge rcsistance 2l. Thus, even though switch L has not operated to cause the separation of contacts L 120 and L 122, should the current in the maintaining relay actuating coil (lr 75 decrease to a predetermined value, the relay would drop out. Such operation might result from too earl;7 centering of the car switch, i. e., the current in coil G 75 would decrease to this predetermined value before the operation oit the leveling switch to cause the engagement of its slow speed contacts. As a result, contacts G 97 would separate to deenergize the up direction switch and brake switch holding coils B 71 and H 72 respectively. This might permit the direction switch and brake switch to drop ont, their actuating coils having been denergized by the centering' of the car switch. The engagementot' the slow speed leveling contacts however, as roller 112 rode onto the vertical surface of its leveling cani, would cause the engagement ot contacts LR 11S-'L and thus the energization ot coils B 57 and H 58.

The up leveling direction switch LU, upon operation, also caused the engagement of contacts LU 170 and LU 171. The purpose of cont: cts LU 170 will be seen troni later description. The engagement of contacts LU 171 completed the circuit for actuating coil M 128 ot the series field relay. This circuitmav be traced from the lett-hand blade of switch 42, by wav ot line 79 through contacts A 50, by wa)v of line 172 through contacts LU 171` intluctanre coil X 150 and coil M 123, by wav et line 89 through contacts A. 51, to the right-hand blade ot switch 42. The series lield rela 'v M did notI operate immediately upon the completion ot the circuit for actuating coil, its action being delayed bjr thc eliect of inductance coil X 150. Relay M, upon operation, causes the engagement of contacts M 151 to complete the circuit for the series field switch actuating coil N 152. This circuit may be traced troni the lett-hand blade ot switch 42, b v wa;v of line 79 through contacts A 50, by wav ot line through coil N and contacts M 151, hv wav ot line 89 through contacts A, 51, to the right-hand blade ot switch 42. Switch N, upon operation, causes the separation ot contacts N 154, hreal-:ing the circuit including resistance 23 in shunt to the. generator series tield winding lil. The generator series field coils are so wound that, without the parallel resistance 23, they would have too great an ettect for proper operation of the ear. The desired compounding is obtained by employing the low resistance shunt. Upon separation of contacts N 154, the strength of the series field is increased for the leveling operation so as to aid in obtaining the desired stopping operation. The short delay in the action of relay M, and therefore the switch N, upon the initiation of the leveling operation, is desirable iii-order that the current in the generator armature-elevator motor armature circuit may adjust itself to such a value t-hat proper series field strenf'vth during the levelingoperation may be obtained.

As the car nears the third Hoor landing.l roller 112 rides off the vertical surface onto the obli ue surface of cam 114. This results in t e separation yof up fast speed leveling contacts 34, deenergizing actuating coil LF 130 of the fast speed leveling relay. The fast speed leveling relay, upon dropping out, causes the separation of contacts Ll!" 146 and the engagement of contacts LF 145. The separation of contacts LF 146 removes the short-circuit for section 155 of resistance 28, increasing the ohmic value of the resistance shunting generator field winding portion 18. Thus the current now supplied to field Windinr portion 18 is increased and that supplied to Windinr portion 17 is decreased. The generator M. F., therefore, is again lowered and the elevator motor runs at an intermediate leveling speed. T he separation of contacts LF 145, upon the operation of the fast speed leveling relay, prevented the energization of the intermediate speed leveling relay actuating coil LI 156 upon the engagement of up leveling 'direction switch contacts LU 170. Upon the dropping out ofthe fast speed relay, however, the reengagement of contacts LF 145, completes the circuit for coil LI 156. This circuit may be traced from the left-hand blade of switch 42, by way of line 79 through contacts A 50, by way of line 157 through contacts LU 170, inductance coil X 158, coil LI 156 and contacts LF 145, by way of line 89 through contacts A 51, to the right-hand blade yof switchy 42. The relay LI does notgoperate immediately, however, its action bein delayed by the effect of inductance coil 158. It is to be noted that, if the leveling operation is such that the up fastr speed leveling contacts 34 do not engage and therefore the fast speed leveling relay actuating coil is not energized to cause the separation of contacts LF 145, the inductance coil X 158 acts to dew lay the operation of relay LI upon they engagement of contacts LU 170. T ie relay LL upon operation, causes the separationof contacts LI 160 to remove the short-circuit for the remaining section 161 of resistance 28, again increasing the ohmic value of the resistance shunting generator field winding ortion 18. Thus the current supplied to geld winding rtion 18 is increasedand that supplied to winding ortion 17 is decreased. The generator E.`M. lig., therefore, is still further decreased and the elevator motor runs at its slowest speed.

Shortly before the car reaches an exact level with the landing, the roller 112 rides off the oblique surfacey of cam 114, thereby separating the slowv speed leveling, contacts 32. The circuit for coil LU 78 and coil LR 117 is thus broken. The4 up 'leveling direc-- tion switch yLU drops out immediately, separating contacts LU 144, LU 170 and LU-171.

f The separationof contacts LUk 171 breaks ythe circuit for coil M 123, relay M droppinfr outto cause theseparation of contacts `l\- '151, breaking the circuit for series field switchcoil N 152. Switch'` N, therefore, drops out to cause the reengagement of its contacts N 154 to reconnect resistance 23 in shunt to the generator series field Winding. The separation of contacts LU 144 disconnectsr resistance 28 from across field winding portion 18, thereby rendering the opposing magnetizing forces exerted by winding portions'17 and 18 equal. As will be seen as the description proceeds, however, switches B, L and H o erate, asy soon as relay LR drops out, to isconnect the Windingportions from the mains and toreconnect them for cumulative action tothe generator armature.

Relay LR does notdrop out immediately the circuit 4for itsactuating coil LR 117 is broken, itsaction being delayed by the effect of inductance coil X 126 and discharge resistance 162. The purpose of the delay in the dropping out' of relay LR will beL seen from later description treating with the operation of the system yduring an overrun. Relay LR, upon drop ing out, causes the separation of contacts R 127, LR 134 and LR 135. The separation of contacts LR127 breaks the circuit comprising resistance 162 and inductance coil X 126in shunt to coil LR 117. The separation of contacts LR 134 breaks the circuit for coils H 58 and B 57. The separation of contacts LR 135 breaks the circuit for coil L 136.`v Y

`Upon the circuit for its actuating coil being brokemup direction switch B drops out, causing the separation of contacts B 66, `B 67 and B 68-and the reengagement of contacts 65. Switch H drops out along with switch B, causing the separation of contacts H andH `81 and the reengagementof contacts H 77.` Switch L, upon'dropping out, causes the Separation of contacts L 140, L 141 and L 142 and the engagement of contacts L 47, L 120` and L 122. The separation of contacts 4B 68 opens line 95 including holding coil B 71, the circuit for coil B 71 and coil H 72k havingalready been broken, however,

by the separation of contacts Gr 97 as preseparationV of contacts L 140 and L 141 and the engagement of contacts L 120 and L 122 reconnects the field winding portions for cumulative action, the field winding being simultaneously disconnected from the mains and connected to the generator armature, however, by the separation of contacts B 66 and B 67 and the engagement of contacts H 77. The separation or contacts H 80 breaks the circuit for the brake release coil 30, effecting the application of the brake. The polarity ofthe connection of the generator field winding to the generator armature is such that the generator sends current through the whole winding in a direction to oppose the iiux which produces the generator E. M. F., thus tending to destroy the residual fiux of the generator field.

Thus, the brake being applied and the generator separately excited iield winding being disconnected from mains 40-41, the car is brought to restlevel with the third floor landing.

In the event of an overrun, assuming in the above example that the car overruns the third floor to the extent of causing the engagement of down slow speed leveling contacts 33, a circuit is completed for coil LR 117 and actuating coil LD 165 of the down leveling direction switch. This circuit may be traced from the left-hand blade of switch 42, by wa y of line 79 through contacts A 50, line 124, contacts 33, by way of line 166 through coil LD 165, by way of line 125 through coil LR 117, bv way of line 89 through contacts A 51, to the right-hand blade of switch 42. T he down leveling direction switch LD, upon operation, causes the engagement of contacts LD 175, LD 176 and LDv 177. As reviously explained, relay LR is maintaine operated after up slow speed leveling switch contacts 32 separate by the action of inductance coil X 126 and discharge resistance 162. This portion of the system is adjusted so as to maintain relay LR operatedl during an overrun until the circuit for its actuating coil LR 117 is completed by the engagement of the slow speed leveling switch contacts for returning the car to the floor, these contacts being down slow speed leveling switch contacts 33 in the example assumed. Thus, upon an overrun into a slow speed leveling zone, contacts LR 134 and LR 135 remain in engagement maintaining the brake switch H, up direction switch B and field control switch L operated. The engagement of down leveling direction switch contacts LD 175, thereore, connects a portion of resistance 28 across ie'ld winding portion 17 so that the current in winding portion 17 is now less thanthat in winding portion 18. Throughout the leveling operations described for bringing the car to the floor during an underrun, the current supplied to winding portion' 18 from the mainsY was in' a direction such as to tend to cause the generation of an E. M. F. of a polarity for causing the motor to move the car in the opposite direction, namely, downwardly. The current supplied to Winding portion 17, however, was in the same direction as was previously supplied to the whole winding before the leveling mechanism took control, thus tending to cause the generation of an E. M. F. of a polarity for causing the motor to continue to move the car in the same direction. Due to the fact that winding portion 18 was shunted during this operation by varying portions of resistance 28, the magnetizing force of winding portion 17 predominated and the E. M. F generated was of proper polarity for causing the car to continue upwardly toward the third floor landing. Upon an overrun, the current through the field winding portions is not reversed due to the operation of the leveling mechanism to effect the return of thel car to the floor, the direction of the current supplied to winding portion 17 remaining in the direction tending to cause the generation of an EMF. of a polarity for causing the motor to continue to move the car in the same direction (upwardly) and the direction of the current supplied to winding portion 18 remaining in adirection tending to cause the generation of an E. M. F. of a polarity for causing the motor to move the car in the opposite direction (downwardly). As the engagement of contacts LD 175 places the desired portion of resistance 28 in shunt to winding portion 17, however, the magnetizing force due to winding portion 18 predominates, causing the generation of an E. M. F. of proper polarity for causing the elevator motor to start the car in the down direction to return to the floor. As intermediate speed leveling relay contacts LI 160 are in engagement shortcircuitcd section 161 of resistance 28 and as the operation of the relay to separate these contacts, upon the encrgization of its actuating coil Ll 156 by the engagement of contacts LD 176, is delayed by the effect of inductance coil X 158, the generation of suflicient voltage to cause the elevator motor to start the car upon its return movement to the landing is assured.

The engagement of contacts LD 177, arranged in parallel with up leveling direction switch contacts LU 171, completes the circuit for series field relay actuating coil M 123. As before, the operation of relay M is delayed by the effect of inductance coil X 150. Thus contacts N 154, depending for their separation upon the operation of relay M, remain closed momentarily to insure that the current in the generator' armature-motor arma ture circuit has fallen to a low value. Since the current in the series field winding may be flowing in a direction suoli as to cause the generation of an E. which is of proper llif) clarity for operating the car in the down irection, immediate increase in the strengthy of the series ield might result in the car again being carried past the floor. As` the car returns to the floor, it is stopped by the separation of slow speed leveling contacts 33 in a manner similar to that described for approaching the floor in the up direction.

If the overrun is great enough to cause the engagement of the leveling switch down fast speed contacts 35 as `well as the levelin switch down slow speed contacts 33, coil L 130 is energized.v As before, relay LF causes the engagements of contacts LF 146 to shortcircuit sections 155 and 161 of vresistance 28, increasing the generator vvoltage andfcausing the elevator motor to run at its fast leveling speed. Also contacts LF 145 separate to prevent the energization of intermediate speed leveling relay actuatin coil LI 156 by the engagement of contacts D 176. Further than this, the operation on an overrun is as above described.

The operation of the system is somewhat modified in the event that a stop is to be made when the car is moving downwardly. In order to briefly describe the Operation, assume that the sto'ming operation has progressed to the extent that the levelin switch operating rollers have been extende for engagement by the leveling cams and that down roller 113 moves onto the vertical surface of down cam 115 before relay G drops out. The engagement of the leveling switch down slow speed contacts 33 completes the circuit, previously traced, for down leveling direction switch coil LD 165 and field control leveling relay coil LR 117. Relay LR causes the engagement of contacts LR 134 completing the circuit for up direction switch actuatin coil B 57 and brake switch actuating coil 58 and the engagement of contacts LR 135 completing the circuit for `the field control switch coil L 136, these circuits having been previously traced. Theenergization of coil H 58 is to maintain switch H operated upon the deenergization of its holding coil H 72. Down direction switch C being maintained in operated condition by itsliolding coil C 64, the direction switch mechanical interlock acts to prevent the operation of the up direction switch B in res onse to the energization of coil B 57 unti the down direction switch drops out. Switch L, as before, operates to reverse the connections for field winding portion 18, the separation of contacts L 120 and L 122 breaking the circuit for coil G7 5 of the maintaining relay. Relay G, therefore, drops out, separating its contacts G 97 to break thecircuit for the L engagement of contacts B 66 and B 67.

Thus the connection for the whole field wind ing is reversed yso that the net result of the operation of switches L, C and B is that the direction of the flow of current through winding portion 17 is reversed while the iow of current through winding portion 18 remains the same. Thus the lnagnetizing force due to winding portion 17 opposes that due to winding portion 18. As set forth above, however, actuating coil LD 165 of the down leveling direction switch was energized `upon the engagement ofthe leveling switch slow seed contacts 33. This switch, operating speed contacts 33, causes the operation of the n fast speed leveling relay. As previously eX- plained, the fast speed leveling relay, by means of its contacts LF 146, causes all of resistancek 28 except section 147 to be shortcircuited. Also field control switch contacts L 142 short-circuit the selected portion of resistance 27. As in the case where the car wasl brought tothe landing upon an underrun in the up direction, with contacts L 120 and L 122 separated and contacts B 66, B 67, L 140, L 141, L 142, LD 175 and LF 146 in engagement, an E. M. F. is generated which causes the elevator motor to run at a suitable fast leveling speed in the down direction.

It is believed that the remainder of the operation of bringing the car to the landing will be obvious from the description of bringing it to the landing upon an underrun when moving in the up direction. Should the car be carried past the landing, when moving in the down direction, resistance 28 is connected in parallel with field winding portion 18, causing the car to be returned to the landing. It is to be understood that the operator may control both the acceleration and retardation of thecarY by moving the car switch in steps. Should the operator suddenly move the car switch from one position into thek other,kfor example from up into down positionV injury to the system is prevented b vcontacts B 65 which remain separated until the up direction switch drops out. Field control switch contacts L 47, arranged in the circuit for the actuating coil F 83 of the accelerating switch, prevent the operation ofi the accelerating switch during the leveling period.

During the leveling period, in systems such as those in which the generator separately excited lield winding is connected to the source in the same manner during leveling as during car switch operation with the desired `low values of generator E. M. F. for leveling obtained by permitting only a small amount of current to low through the winding, were the same values of current supplied to the winding for bringing the car to the Hoor upon an underrun as for returning the car to the floor after an overrun, variations in operation might 'occur due to the varying eftects of the residual iiuX of the generator ield. As such small values of current effect the production of low values of lux, the residual flux presentwould form a large percentage of the total flux and therefore might atleet the operation of the system very markedly. In order that the effects of the residual tlux may be clearly seen, reference may be had to the assumed hysteresis curve shown in Figure 3. This ligure illustrates the conditions when a small current is supplied to the separately excited held winding of a generator, as during the leveling operation. The magnetizing forces due to this small current are represented as NI and n-NL depending on whether the car is approaching the floor, or returning to the floor after an overrun. Assume that the generator armature E. M. F. has been of a value V1 and that later, in attempting to make a landing, the self-leveling operation takes place with the car approaching the floor. The E. M. F. of the generator during this period will be of a value V2. On the other hand, it the car overruns the floor, the E. M. F. of the generator for returning the car to the floor will be of a value V3, which value is much less than the value V2. Hence the speed of the elevator motor is much less. The values V2 and V3 of the generator E. M. F. may vary during operation of the system depending upon the previous magnetic state of the machine. Obviously, such diilerences in the numerical values of the E. M. F. generated would result in undesirable variations in operation under leveling conditions. These variations cannot be satisfactorily corrected merely by adjusting the amount of resistance in series with the separately excited ield winding. For example, if the amount of resistance were decreased in order to raise the value of V3, the value V2 also would be increased, resulting in an increasing tendency to run past the floor. Similarly. if the amount ot resistance were increased in order to lower the value of V2, the value of V3 also would be lowered, which value might be too low to effect the return of the car to the floor after an overrun. It the effects of residual flux are eliminated for leveling operating conditions, the system may be adjusted so as to obtain more uniform operation. This desired result may be attained by reversing the polarity of certain of the field poles. The

preferred arrangement for effecting this change has already been described in connection with Figures 1 and 2, the particular arrangement of the separatel excited field winding being illustrated in igure 2.

Referring to Figure 2, it is preferred to group the coils for the north and south poles N and S together to form the portion 17 and those for t-he north and south poles hl1 and S1 together to form the portion 18. The coils forming the portion 17 are connected in series relation as are those forming the portion 18. For convenience of explaining the action of portions 17 and 18 of the field winding, assume again that the car is moving in the up direction. With switch L in deenergized position, as during car switch operation, the current flows through the eld coils in such manner as to provide oles of alternate polarity as indicated. pon an underrun in sto ping, the up main direction switch contacts 66 and B 67 remain in engagement and switch L operates to cause the separation of contacts L 120 and L 122 and the engagement of contacts L 140 and L 141. Thus, as previously described, although the direction of the flow of current through the coils for poles N and S (winding portion 17) is not aii'ected, the current through the coils for poles N1 and S1 (Winding portion 18) is reversed. Thus N1 becomes a south pole and S1 becomes a north pole. Similarly, upon an underrun in stopping, where the car has been moving in the down direction during car switch operation, the down main direction switch drops out and the up main direction switch B and field control switch L operate to cause the separation of contacts L 120 and L 122 and the engagement of contacts B 66, B 67, L 140 and L 141. Thus the net result, as previously explained, is to cause the current to flow in the same direction through the coils for poles Nl and S1 (winding portion 18) but to reverse the flow of current through the coils Jfor poles N and S (Winding portion 17 Thus N becomes a south pole and S becomes a north pole. If these poles were excited equally with the winding connected for the leveling operation, the value of the total E. M. F. at the generator brushes 19 would be substantially zero, since the voltage generated in part of the generator armature winding would be balanced out by a voltage of equal value but opposite polarity generated in the remainder of the winding. However, as previously explained, a difference in the values of the magnetizing forces due to the winding portions is obtained by connecting resistance 28 in parallel with one of the Winding portions so that an E. M. F. at the generator brushes is obtained. .By utilizing a large magnetizing force for each pole and by employing a resistance 28 of such ohmic value as will cause a proper difference in the values of these magnetizing forces, an

cuited so that large magnetizing forces arev still emplo ed for the poles, the generation of an E. F. for returning the car to the floor, as previously explained, being obtained by disconnecting resistance 28 from one wind'- ing portion and connecting it in parallel with the other. In this manner, the iron ofthe various'parts'of the magnetic circuit of the generator ield structure is worked on the high ortions ofthe hysteresis loop where the e ect of residual flux is practically nil, and E. M. F.s may be obtained, during leveling operations, the values of which are not affected by residual flux and are practicallyl the same Whether the car underruns or overruns the landing. f

The series field winding 16 acts to assist the separately excited eld Winding portions to obtain the desired conditions during operation. Under normal car switch operation,

when these Winding portions assist each other,

the series field winding acts in the usual manner to compensate for varying load conditions. During leveling conditions, when the elevator motor is lifting a load, the eect of the series field winding is to aid in. bring ing the car to the floor since the` current flow in the series field winding is in `such direction as toproduce a magnetizing vforce which assists thatdue to the field winding portion through which thespredominating current flows and opposes that due to the field winding portion through whichy less current flows. Conversely, wheny the elevator motor is lowering a load, the effect of the series field winding is to aid inl causing the car to stop at the floor since the current flow in the series lield winding is in such direction as to produce a magnetizing force which op,- poses that due to the field winding portion through which the predominatingr current flows and assists that due tothe field winding portion through which less current flows.

As previously explained, upon an overrun,

i the up main directionswitch contacts B 66 and i' to the other to eect the generation of an E. M. F. for returning the car totheiloor.A simply causes a reapportionment ofthe amount of current supplied'to each Winding portion. For convenience of explanation, as.-v sume that the car has been` moving in theup direction vand that it overruns the desired landing in stopping. During the part of the leveling period that the car is below the ioor, resistance 28 is connected in parallel with winding portion 18 causing the current supplied to Winding portion 18 to be less than that supplied to winding portion 17. The transfer of resistance 28 causes the current in winding portiony l8'to be increased and that in winding portion 17 tobe decreased to the extent that current in winding portion 17 becomes less than that inwinding portionv 18. Thus, considering the generator E. M. F. due to the separately excited field winding, the v)Liredominating voltage generated in one portion of the generator armature winding decreases and the opposing voltage generated in the remaining portion of the armature winding increases with the result that the so termed opposing voltage is caused to pre- .i

dominate and an E. M. F. at the generator brushes is obtained for causing thecar to be returned to the ioor.y Due to the fact, however, that the current in one winding portion is. simply decreased while that in the other is increased, the change in the values of the opposing magnetizing forces of the winding portions occurs very quickly. Consequently, the change in the relative values of the opposing voltages generated in the generator armature winding portions and therefore t-he establishment of a generated E. M. F. suitable for returning the car to the {ioor upon an yoverrun also occurs quickly. Thus the time .required to return the car to the desired landing in the event of an overrun is mini mizedy with the result that the overall operating eiiciency ofthe system as a whole is raised considerably.

It is to be understood that the above described arrangement is suitable for use with various types of generators and that these generators may be of other pole numbers. a four pole generator being chosen merely for convenience o description. It is further to be understoodl that the portions of the field Windingmay be arranged in different circuit relations and that the coils may be grouped differently to effect the desired result.

As many changes could be made ink the above construction and many apparenly widely different embodiments of this invention couldy be made without departing from the scope thereof, it isvintended that all matand means for causing the motor to level the 3f car with a desired landing in stopping7 regardless of whether it underruns or overruns said landing, said means comprisin means for connecting said winding to sai source in such manner that the E. M. F. generated due to the flux created by the current flowing in a portion of the winding opposes that generated due to the flux created by the current flowing in the remainder of the winding, means for causing the first mentioned flux to be less than the second mentioned flux to cause the generation of a total E. M. F. f proper polarity for bringing the car to the landing during an underrun in one direction and for returning the car to the landing after an overrun in the other direction, and means for causing the second mentioned flux to be lessl th an the first mentioned flux to cause the gene 'ation of a total E. M. F. of proper polarity for bringing the car to the landing during an underrun in said other direction and returning the car to the landing after an overrun in said one direction.

2. In combination an elevator car; a hoisting motor therefor; a generator for supplying current to said motor, said generator having a field winding; a. source of current; means for connecting the whole of said wind ing to said source to cause the generation of an E. M. F. of certain value for causing the motor to move the car 'between landings; and means for causing the motor to level the car with a desired landing in stopping from one direction, regardless of Whether it underruns or overruns the landing, said last named means comprising means for reversing the connections for a portion of said winding, a resistance, and means for connecting said resistance in parallel with the reversed portion of said winding during an underrun and in parallel with the remaining portion of said winding during the return of the car to the landing after an overrun.

8. In combination; an elevator car; a hoisting motor therefor; a generator for supplying current to said motor, said generator having a field Winding divided into two portions; a source of current; means for connecting the whole of said winding to said source so as to cause said portions to act cumulatively to obtain a terminal E. M. F. of certain value for causing the motor to move the car between landings; and means for causing the motor to level the car with a desired landing in stopping, regardless of whether it underruns or overruns the landing, said last named means comprising means for reconnecting the whole of said winding to said source so as to cause said portionsl to act in opposition, a resistance, means for connecting a portion of said resistance in parallel with one of said winding portions to obtain a terminal E. M. F. of a lower value than said certain ie and of proper polarity for bringing the' to the landing upon an underrun in one n bei direction and for returning the car to the landing after an overrun in the other direction and for connecting said portion of said resistance in parallel with the other winding portion to obtain a terminal E. M. F. of a lower value than said certain value and of proper polarity for bringing the car to the landing upon an underrun in said other direction and for returning the carto the landing after an overrun in said one direction, and means for increasing the amount of said resistance so connected, during underruns in either direction and the returning of the car after overruns in either direction, as the car nears the landing.

4. In combination; an elevator car; a hoisting motor therefor; a generator for supplying current to said motor, said generator having a field Winding; a source of current; and means for causing said motor to bring the car to a stop at a desired landing, said means comprising means for connecting said winding to said source in such manner that the E. M. F. generated due to the flux created by the current supplied to a portion of said winding opposes the E. M. F. generated due to the flux created by the current supplied to the remainder of said winding, means for causing the first mentioned flux to be less than the second mentioned flux to cause the generation of a total E. M. F. of a certain value to cause the motor to run at a certain speed, and means for increasing the first mentioned flux and for decreasing the second mentioned flux as the car nears the landing to decrease the total E. M.F. and therefore the speed of the motor.

5. In combination; an elevator car; a hoisting motor therefor; a generator for supplying current to said motor7 said generator having a field winding; a source of current; means for connecting ysaid winding to said source to cause the motor to run at a certain speed; means for decreasing the speed of said motor, said second named means comprising means for reversing the connections for a portion of said Winding, a resistance, and means for connecting aportion of said resistance in parallel with said reversed por-y tion of the winding; and means for further decreasing the speed of said motor, said last named means comprising means for increasing the amount of said resistance so connected.

6. In combination; an elevator car; leveling mechanism for said car, said mechanism comprising fast speed contacts and slow speed contacts; and means responsive to the engagement of said fast speed contacts for causing the car to run at a fast leveling speed' and responsive to the separation of said fast speed contacts, with the slow speed contacts in engagement, for causing the car to run at a speed which is intermediate the fast and slow leveling speeds and thereafter, upon the expiration of a predetermined time interval after the separation of said fast s d contacts, for causing the car to run at s ow leveling speed.

In combination; an elevator car; a hoisting motor for said car; a source of current for said motor; means adapted to vary the voltage applied to said motor from said source; means for causin Said motor to operate the car between lan ings, said Second named means comprising means for controlling said volt e varying means to control the speed of t e motor; and means for causing the motor to level the car with a desired landing in stop ing, said last named means comprising leve ing mechanism havin fast speed leveling contacts and slow Spee leveling contacts, means responsive to the engagement of the fast speed contacts and the slow speed contacts for controlling said volt-k age varying means to cause the motor to operate the car at a fast levelin speed and responsive to the separation o the fast speed leveling contacts for controlling said voltage varying means to cause the motor to operate the car at an intermediate leveling speed, and means responsive to the separation ings, said means comprising a switch operable from one position to another to cause current to be supplied from said source through said winding in one direction to cause said generator to apply voltage to said motor ofy a polarity to cause movement of said car in a certain direction, and a second switch operable from one position to another to cause current to be supplied from said source through said winding in the other direction to cause said generator to apply voltage to said motor of, opposite po arlty to cause movement of said car in the opposite direction; and means for causing the car to be brought to a level with a landing in stopping, said leveling means `comprising means operable, regardless of whether the car underruns or overruns the landing, to cause the reconnection of said winding to said source in such manner that the current through the winding for only'half of the enerator pole pieces is reversed to cause the rst named switch to be maintained in its other position in the event that the car has been traveling in said certain direction and to cause the return of the second switch to its one position and the operation of the first named switch from its one to its other posif tion in the event that the car has been travelname to this specification.

ANTHONY PINTO.

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