US1680784A - heart - Google Patents

Description

Aug.'1.4, 192s.

= 1,680,784 H. L. HEART CONTROL SYSTEM FOR ELEVATORS File March 9, 1926 2 Sheets-Sheet 2 Patentedl Aug. 14V, `1928.

i n t1,680,734 PATENT j(31A-"gracia,--k

` HERBERT L. HEART, 0F NEWYonK, N. AssrGNonfTo oTIs ELEvAToRcoMPANY,

' f 0E JERSEY CITY,NEW.JERsEY, A 'CORPORATION or NEW JERSEY.

vooirrnori SYSTEM non ELEvAToRs.

.Applicationruedrivrarcii 9,1326( seria1'Np.,93,453.

The invention relates'fto controlsysteins for relevators and particularly to thosefor.

elevators of the lself-leveling type. n b

lVhere vself-leveling apparatus is employed in elevator systemsto ycause the carto be brought to a desired landing in stopping, regardless of "whether it .underruns or1overruns the landing, and wherein the elevator motor is supplied withcurrent from a varicomplete round b trip is considered, it .V will be seen that the yoperating efficiency ot'the system vas a whole is considerably impaired. One factor to be considered in theoperation of` leveling is theV variation in load on` thev hoisting motor. This yis'iparticularly true where the generator is provided with 4a series field winding. lWhenever the motor is lifting a load and the car is not brought to rest duringtlie stoppingoperati'on until it has passed the landing; the current in the generator armaturamotor armature circuit, upon the initiation of the operation of the leveling apparatus to returnthe carto the landing, may cause the` carto vbe carried or bounced :past thealanding. In"`such a case y an `additional n operation" isy required to bring thecar to a level withY the landing. y Y

Onefieatureof `the present inventionv is to cause more Yunitorm operation of theelevator car during'the leveling `period in the event of anoverrun by minimizing the tendcncyof the Car to be carried pastV the landing in the opposite direction from, that rin which it was traveling Abefore Vthe leveling Other features and advantages will. become apparent from fthe following, description, taken in connection vwith the accompanying drawings `wherein *oneA embodiment of*` the invention is illustrated and in which;` y

Figure 1 is a diagram of an elevatorcontrol system; y

Figure 2 is a schematic representation of the elevator car ata landing, illustrating the arrangement ofthe car switch'and of mechanism suitable tor eecting leveling and car gate and tions hatchway door opening operato Figure 1, of anotherarrangement ot the vcontrol system and l' Figure l is aportionof a diagram, similar to Figure l, ofstill another arrangement of the control system.` l Referring vto Figure A1, no attempt isV made to show the'coils yand 'contacts of the various electromagnetic switches in their vassociated positions7V a straight diagram being em- Figure 3 is a` portion of ay diagram, similar ployedv'lieiein the coils and contactsv of the variousswitchesV are separated insuch manner as torender the circuits 'involved relatively simple. Also the parts of y"other switches -and apparatus are separated in the f interest of simplifying the diagram. "For a clearer understand,mg of the 1nvention,' the stationary contacts 'of the switches are Aillustrated in cross section. It isto be understood that the system in Which'the invention illustrated is chosen merely for convenience of description and' that,kalthou`gh described in conjunction with a car switch controlled system; the invention is equally applicable to other types of elevator systems such as push button control systems and to other systems employing al` work niotor supplied with `currentfromthe generator of a d motor generator set.` f n n The motor generator set comprisesa driving motor 11, illustrated for convenience of description as oft the direct current type, and a variable voltage directY current gener-A ator 12. The armature ot' the driving ino-` tor is designated 13 andvits'tield winding 14. The armature of the generator is designated 15, its series lield winding 16, its main separately excited field winding-'17 and its auxiliary separatelyexcited `lield winding 1S. The elevator motorfis designated 'as a whole by the numeral 20, 'its armature being designated 21 and its field winding 22. fAn Aadjustable resistance 23 is arranged in shunt to the generator series lield winding. Discharge resistances 24 and 25 are provided for the vgenerator separatellyeXcited field windings 17 and 18'respectively. Discharge resistance 26 is provided for 'the elevator motor lield winding`22. A resistance 27 is provided for controlling the strength' ofthe generator field and therefore the voltagel `applied to the elevator motor armature duringear ewitchoneration. l An lfl other resistance 28 is provided for controlling the strength of the generator field during leveling operation. 19 and 39 are the retarding resistances. A resistance 29 controls the strength of' the elevator motor field during different conditions of operation. l0 is the release coil for the elevator motor electromagnetic brake. This coil is provided with discharge resistances 31, 32 and 33 for controlling the application of the brake under different conditions of operation. 34 and 35 are the upslow speed contacts andthe down slowr speed contacts respectively of. the leveling switch, the leveling switch up and down astspeed contacts being designated 36 and 37 respectively. 38

is the armature and 40 is the field winding f ot the motor 4l for moving the rollers of the leveling switch into position to clear the leveling cams. 42 is the armature and 43 is the field winding of the door control motor 44. 45 'and 46 are the direct current supply mains. 47 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 designatedl as a whole by the numeral 48. 50 is the safety switch in the car. The series of door contacts are indicated by a. single set n of contacts 5l. rl`he gate contactsare indicated as 52. The various safety, limit, stop and emergency switches are omitted in,order to simplify the description.

The electromagnetic switches have designated as follows:

A potential switch, B-upy main direction switch, C-down main direction switch, D-Yfirst accelerating switch, E-second accelerating switch, F-series field switch, Gkseries .field relay, H-inain brake and field switch, .ldoor control motor switch, Kdoor control motor maintaining relay, M-maintaining relay, N-sequeuce relay, O-accelerating relay, )e-hard brake switch,

Qload switch, lt-up retarding relay, DR-down retarding relay, LB-up leveling direction switch, LC-down leveling direction switch, LH-leveling brake and field switch, LF-fast speed leveling relay.

been

Throughout the description which fol` lows, these letters, in addition to the usual reference numerals, will be applied to the yparts of the above enumerated switches.

For example, contacts B 111 are contacts on the up main direction switch, while actuating coily A 53 is the coil that operates the potential switch. The electromagnetic switches are shown in their deenergized posit-ions. Reactances are similarly designated by the character X.

Upon the closing of the knife switch 47,

the driving motor 1l, elevator motor field winding 22 and potential switch actuating coil A 53 are ener rized, the circuit for coil A 53 being througli safety switch 5l). The driving motor starts in operation, bringing the generator 12 up to full speed. The series field winding and starting means for the driving motor are omitted to simplify the descri tion. lith the elevator motor at rest, tie current supplied to its field winding 22 is reduced b Y section 54 of resistance 29, providing w at may be termed a standing field. The circuit for the elevator motor field winding may be traced from the left-hand blade of switch 47, line 55, by way of line 56 through field winding 22, resistance section 54, and second accelerating switch contacts E 57, line 58, yto the right-hand blade of vswitch 47. It is not desired to apply full line voltage tothe field winding 22 when the elevator motor is not in operation because of increased power consumption. 0n the other hand, it is not desii-ed to have this field winding deenergized with the elevator motor at rest as a matter of safety and because of the time constant ff involved in building up. The potential switch, upon operation, causes the engagement of contacts A60 and A 61, preparing the circuit for the generator separately excited field winding, the electromagnetic brake release coil and the control circuits. The condition of the circuits so far described might be termed normal.

Referring briefly to Figure 2, the car switch 48 comprises a set of up contacts 62, 63, 64, and 66 and a set of down contacts 67, 68, 69, and 71. A contact segment 72 for bridging the contacts of each set is mounted on the segmental support 73 of insulating material. A'cam 74 is formed on the support above the pivot point 75 The cam is formed with a centrally disposed depression 76 into which the operating roller 77 of the gate and door switch 78 extends with the car switch in neutral or ofi' position. The switch 78 is pivoted at 80 so that movement of thecar switch in either direction causes the engagement of the switch contacts. The car switch is operated by means of a control handle 81. It is reerred to provide centering springs not shown) on the car switch to cause it to be returned Ato off position when released by the operator.

Referring back to Figuie 1, assume. that the system is designed for an installation ot several floors and that the car is at rest at the first floor with the gate and door open. In the starting operation, the operator first gives the car switch a slight initial move- SNI lll)

lao

nient to effect the closure ofthegate'and ldoor switch 78. For convenience of dc- :switch actuating coil J, 82. This circuit may be traced from the left-hand `blade ot switch y47,-by way of line through 'contacts A `60,

by vwayof line83 throughooil .i 82, resistancei84 and switch y78,lii'1e85, switch 50. line 80, line 5,8, to the right-hand blade of switch r47. upon operation, causes the ei'igagemenuof kcontactsJ :87, completing thecircuit for the door control motor 44.*1`h`is circuit may be traced fromthe'left-hand blade of switch 47,by way ofline 55 through contacts n.60,

by way ofy lino 88 throizigh contacts J 87,y

door vcontrol motor held l windingA 4% land armature-42, by way of line 58 tl'uough con- VtactsA 61, to .the right-hand blade r of .switch 47." l'

Referring againator Figure 2, thc motor 44 operates `pneumatic' .ga te yand door operating mechanism, as lor example through linkage y90 tomove valve. 91 for gate engine :92 to gate closed .positionand to `withdraw the retiring cam 93 from engagement with 'the roller provided on ,the .end ofthe (lo-'onengine valve .lever 94.1 The lever `94. operated by a! spring to move valve fori-the door engine 96 to door closed position. The

gate and r door engines `,operatethrough mechanism not `shown toclose rthe car4 gate L99 and hatchway,doorr 10,9. It `is to `beunderstood thata door is provided inthe hatchway. at each landing. 4 ,i e

Referring back to'lligure 1, if kthe operator, after ,he has .closed the gate and door,

` desires kto open` them, vor ifv he kdef-:ircs to arrestytheir movement, he may do yso by releasing the car switclrto return to ,ott position.v YThis causes the openingof thegate and door switch 78 with the conscquentde- `energization of coil J 82 andthe separation of contacts J 87. Inthis manner', thecircuit for the motor 44 is broken'. The spring 97, shown in Figure 2, operates upon the deenergization of motor 44to move valve 9 1 and, through cam 93 and lever94,.valve intoposit-ions to cause the reverse operations of theengines 92 and 90 Yto open the gate and door.` Obviously otheryforins of power operated gate and 'door inoclui-nisms,

suc-h as electricin lieu .of pneumatic, may

kbe employed without departing from the spirit otthe present invention.

Assuniin@ that the (fate i and doors l are closed, the gate contacts 52 and door contacts 51 `are irl-engagement. The operator may Inow move the car switch to full operated position to start theca-r in the up direction.

ltis'to be noted that the gate'andidoor switch 7 8 remainsrin closed positionjso long asithe car Vswitch is moved out of neutral position. Upon the engagement of Contact Tl,1 L f i 1c (oor-contro.` inotoi switch,

relay maybe traced from the'left-handblade 1 thest-arting of the car. ycontacts 52 or any of the door contacts 51 are brake and held switch and B 102 of the up main direction` switch being in the circuit for coil N 100./ `The engagement of the `contact segment and contacts 65 and 66 prepares circuits for the actuating coils of the` accelerating switches.

The circuit for coil N of the sequence of switch 47, by way of line 55- througl'i contacts A 60, by way of line 103 tl'n'ough coil N 98 and resistance 104, contacts 62 and 64 i of the carswitch, by way of line 105 through contacts C 106 ofthe down main direction f switch, line 85, to the `right-hand blade of A,switch 47 as above traced. lThe circuit for coilv N 100 may be tracedfrom the left-hand blade of switch 47, by way ofline 55 through ncontactsiA (30, byway ofline 107 through door contacts 51gate contacts 52, sequence relaypcontacts N108, and .coils N '100, H 101 andll 102, contacts G3 and64 of the car switch, -to' the right-hand blade of switch 47 as above` traced.` The purpose of the sejquence relay 'N is to insure .the closure of the gate andidoors before ystarting the car.

Coils N 98 and N 100, being differentially wound, oppose'each other, when energized simultaneously, toprevent the operation of the relay. ofthe other, .or ifv either coil'alone is energized,.contacts N 108 separate, preventing If either thev gate sepa :ated at the time that car switch seguinent 72 engages contacts 64, coil N 98 alone is energized, Aresulting 1n the separation'of contacts N 108.l The separation ofcontacts `N108.prevents. the energization of coil N 100, `maintaining the sequence relay oper- 'ated,`andof coil B 102preventing the operationoftlie up lmain ydirection switch to elfectrthe starting of the car.v The switch 78, therefore, `is vclosed by the initial movenientv of thecar switch so that the gate and door contacts may be closed before the engagement of.segment,72 and contact 64.

,Howeven if thecaivswitch .is moved into position where segment 72 engages contact 64 before the closure of the door and gate contacts, the sequence relay operates to prevent the starting vofthe car. Thus it is impossible-to start the car on the vdoor or gate contacts, f Y e f Xssuming that the sequence relay" has operated,morder to startr the car, the car switch lisfreturnedto a position with seglment 72 disengagedy from contact G4, deenergizing coilN 98'topermit contacts N 108 to reengage. 1f the fgatea-nd door are closed,

the ,car, switch may be returned immediately to full on position. Qt-herwise, closingof If either coil is energized ahead' the gate and door` must be effected before the car switch is moved into full on position.

It is preferred to provide the main direction switches with a mechanical interlock to prevent their simultaneous operation. Such an interlock may be of the form of a walking beam pivotally mounted for engaging catches on the armatures of these switches. Upon operation of the up main direct-ion switch in response to the energization of its actuating coil B 102, contacts B 110 separate' and contacts B 109, B 111, B 112 and B 113 engage. The separation of contacts B 110 breaks the circuit leading from the car switch down feed contact (59, contacts B 110 and the corresponding down direction switch contacts C 106 serving as electrical interlocks. prepares a circuit for the down retarding relayactuating coill DB 121. The engagement ot' contacts B 113 prepares the clrcuit for the up main direction switch holding coil B 115 and the main brake and field switch holding coil H 116. The engagement of contacts B 111 and B 112 completes a circuit for the generator main tield winding 17. This circuit may be traced from the lefthand blade of switch 47, by way ot' line 55 through contacts A 60, resistance 27 and contacts B 111, by way of. line, 117 through field winding 17, by way of line 58 through contacts B 112 and contacts A 61, to the right-hand blade of switch 47.

The main brake and lield switch H operates simultaneously with the main direction switch B. Switch H, upon operation, causes the separation of contacts H 119, H 122 and H 123 and the engagement of contacts H 124, H 125, H 126 and H 127. The separation ot contacts H 119 disconnects the generator main field winding from the generator armature. The purpose of this arrangement will be explained later. Contacts H 122 are in the circuit for the generator auxiliary field winding 18. The purpose of this arrangement also will be explained later. The sep-l :tration of contacts H 123 disconnects resistanceSB from across the brake release coil 30. Resistance 38 being of low ohmic value, its disconnection before contacts H 124 engage prevents excess power consumption from ina-ins and 46. The engagement of contacts HA 127 establishes a circuit for the door control motor maintaining relay actuating coil K 130. This circuit may be traced from the rlett-hand blade of switch 47, by way of line through contacts A G0, by way ol line 83 through coil J 82, by way of line 131 through up leveling direction switch contacts LB 132, down leveling direction switch contacts LC 133, contacts H 127 and coil K 130, line S5, to the right-hand blade of switch 47 as previously traced. The engagement of contacts H 125 further pre ares the circuits for the actuatingk coils o the ac- The engagement of contacts B 109 celerating switches. The engagement of contacts H 126 short-circuits section 54 of the elevator motor 'field resistancel 29, permitting the motor field to build up to its full strength. The engagement of contacts H 124 completes the circuit for the brake release coil 30. This circuit may bc traced from the left-hand blade of switch 47, by way of line 55 .through contacts A 60, by way of line 134 through contacts 135 operated by t-he brake, brake release coil 30 and contacts H 124, by way of line 58 through contacts A 61, to the right-hand blade of switch 47.

The door control motor maintaining relay coil K 130 in the circuit above traced is subject to the potential drop across resistance 84. The system is arranged so that the voltage thus applied to coil K 130 is sufficient to effect the operation of the relay. Contacts K 136 engage, upon the operation of the relay, to by-pass contacts H 127. The purpose of this arrangement will be seen from later description.

The brake release coil 30 being energized, the elevator motor field being connected directly to the mains 45 and 46 and current being supplied from the generator armature 15 to the elevator motor armature 21, due to the energization of the generator main field winding 17, the elevator motor starts,

As the brake releases, the brake switch contacts 135 separate to insert cooling resistance 137 in series with the brake release coil. These brake switch contacts are preferably arranged to be separated at the end ot' the releasing operation. Separation of contacts 135 also breaks the short circuit around coil O 138, permitting the operation of the accelerating relay O. This relay operates to cause the engagement of contacts O 140, completing the circuit for the first accelerating switch actuating coil D 141. The purpose of this arrangement is to utilize the time constant of the brake for timing the acceleration of the motor, more specifically, for timing the operation of. the first accelerating switch. Although the brake release coil is energized at the same time that power is supplied to the motor, the brake shoes do not lift at once because of the inherent time constant of the brake magnet and because the brake shoes and lever arms represent considerable mass to be set in motion. The circuit for coil D 141 completed by contacts O 140 may he traced from the kleft-hand blade of switch 47 by way of line 55 through contacts A 60, by way ofV line 107 'through the door contacts 51` gate contacts 52 and contacts N 108. by way of line 142 through contacts H 125, contacts O 140 and coil D 141, contacts and 64 of the car switch, to the right-hand blade of switch 47 as previously traced. l f

lon

, 47, by way vof line 55 throughcontacts A 60, u Jl' by way oliline 107 through door contacts 51,

' 150 through coil B115 and contacts :B 113,

The operation of the irst accelerating switch, in response to the`energization of its actuating coil, causes the engagement off contacts D 143, rD 144, D145 and--D '146.

`The engagement oficontacts D 143 completes the circuit for the leveling switclr1notor-41.

yThis circuit may betraced fromr theclefthandjbladc'olf switch 47 ,by wayot1 line 55 through contacts Ay 60, by' way of linei147 through contacts D'1143, 'fieldi winding 40 and armature 38 of `1notor,. 41, by yway ot' line v58 through contacts AI 61, to the righthand blade of switch 47. YThe leveling switch 4fmotor, upon energization, acts to move theA leveling switch operating rollersl so as to clear .the leveling Acams during movement of the car. This operation will be explained later. Thefengagement of contacts D 144 completes the circuit for 'holding coils B 115 and H 116. This circuit may be traced from the left-hand blade of switch 47,l by way ofline 55 through contacts A 60, by way of linev 148 through coil'l H 116 and contacts D- 144, by way of `line' line 151, line 85, to the right-hand blade oi switch 47 as previously traced.` The purposeoif the energization of these holding coils willy be seen `from later description. The engagen'ient ofcontacts D 146 completes the circuit-tor the second accelerating switch .f actuating coil E 152'.A vThis lcircuitkr'nay` be traced trein the lett-hand blade of switch gate contacts 52 and vcontacts N 108, by

way ot line 142 v`through contactsH ,125,

` by wayot line 153through contacts D 146,

' winding.

reactance'X 154 and coil'E 152, car switch contacts 66 and 64, to the right-hand blade removes the shunt circuit arounda portion l' vof resistance160.; The separat-ronof contacts E156 [before contacts'E :15,8 engage prevents excessl power consumption from mains and 46.` Thel engagementfof con-pY tacts E158 completesthetcircuit for the first. accelerating switchholding coil vD 1617 and the maintaining relay actuatingcoil M 162. Thiscircuit may be tracedirornr the lett-hand blade of switch 47, by way of lineV '55 through contacts A60, by way offline 151 through lcontacts, .E158,`reactance Xy "69, v and 71.k Vvpleted for the downmainy direction switch actuating coil'C 168. This circuitl may beA vtraced from the left-hand bladeof'switch n ics, con D ici and @ou M 162, 11n@ 85 m the right-hand blade of switch 47 as 'previously traced. The maintaining relaylconrtacts M 164 are ,thus `caused to oy-pass contacts D144. The purpose ofthisarrangement will be described later. yThe engagement ofcontacts E 157 short-circuits section 165 ot resistance 27-to increase'the voltage applied to the4 generator main field wind#r` ing. -The E. M. F .of the generator, therefore, increases to its full value and the speed tion of contacts E57 removes the short circuit for section 167 of resistance 29 1n the elevator motor-.field winding clrcuit, bring,-

ing the elevator motor up to' full speed. 1

The starting of the car in rthe downdirection is accomplished `in a vsimilar .mannen and will be only briefly described. TheA operator lirst moves thecary switch into position to cause the closure of the gate and door l and then into full lon position where its contacty segment 72 ,bridgesl contacts `67, r68,

Thus the -circuit -is f com- 47, through coil H 101 as previouslytraced,

by kkway offline 170. through .coil C 168, car l s'witclrcontacts 68 and 69, by Wai 0f liner 171 through contactsy B 110, line 85,'t0 the rright-.hand blade of switch 47k as .previously traced. i The circuit for coil N 98 isby way lofline 172. The circuit vfor coil D 141 is by way of line 178. The circuitffor coil E 152 is by way of line 174. The downinain direction switch7 upon operation, causes the separation of contacts C 106 and the'engagement of contact-SJC 169, C175, Cl

176, and C177 these contacts corresponding' with up -ln'ain direction switch contacts B 110,

B 109, B '111,' B 112` andB 1113 respectively.

Contacts C 169 preparea circuitV for` the up retarding relay actuating-coil UR 118. The

holding coil 'o't the dow-n main direction y switch is designated C178. Further than this, the koperation of' starting 'the' carin the down direction is the same kas described" for starting itin the up direction. y

Assume Vthat the car is rui'iningintheup direction and thatthe operator cent-ers thev car switch between the secondy and 'third of the elevator motor increases. The separa y fioo'rs in order to stop at the fthird floor l landing. ThusV thewcontact` segment 72 moves oft contacts 66, y65,64 and`63 andthe circuits for the second acceleratingswitch 'i actuating coil ,E i152, first accelerating switch actuating-coil D 141,'Inain brake and iield switch actuating coill H 101, up main y direction switch actuz'itingc'oil B `102vand seL qnence relay coilsN 98 and-YN 100 are brokenl The second accelerating switch drops out immediately. The first accelerating switch, lnainbrale and e'ld Yswitch and 'upinain direction switch are maintained operated,

however, by holding coils D 161, H 116 and B 115 respectively. The deenergization of coils N 98 and N 100 is in preparation for the next starting operation. It is to be noted that switch 78 is opened by the centering of the car switch. The circuit for coil J 82, however, is maintained through contacts H 127 and K 136 in parallel and coil K 130.

The second accelerating switch, upon dropping out, causes the separation of contacts E 157 and E 158 and the reengagement of contacts E 57 and E 156. The separation of contacts E 157 reinseits section 165 of resistance 27 in series with the generator main field winding to decrease the E. M. F. of the generator.A The engagement of contacts E 57 short-circuits section 167` ever, their action being delayed byy the effect of reactance X 163 in series with the coils and the discharge resistance 160 in parallel with the reactance and the coils. The engagement of contacts E 156 to shortcircuit a portion of resistance 160 is effective to prolong the time element of the switch and relay. The time element may be adjusted to the desired value by changing the amount of the resistance portion short-circuited. Relay M is preferably adjusted to hold in `at. a smaller current value than the accelerating switch D. This may be readily accomplished due to the fact that the relay is much smaller and therefore lighter in construction than the accelerating switch and requires less current` to hold 1n.

The firstaccelerating switch, upon dropping out, causes the separation of contacts D 143, D 144, D 145 and D 146. The separation rof contacts D 144 is in preparation for the next starting operation, contacts M 164 remaining in engagement to maintain holding coils H 116 and B 115 energized. The separation of contacts D 146 also is in preparation for the next starting operation, the circuit for coil E 152 having been broken by the movement of the car switch as above described. The separation of contacts D 145 removes the short circuit for section 155 of resistance 27, decreasing the strength of the generator field. Thus the generator E. M. F. is again decreased and the speed of the elevator motor is reduced. `The separation of contacts D 143 deenergizes theleveling switch motor 41. In this .manner the leveling switch'operating rollers 183 and 184 are moved into position where the do not engage the leveling cams 185 an 186 .during motion 4 ofthe car, a stop beingprovided to determine the extent of the movement. leveling cams are provided for each floor. The leveling switch is pivot/ed on a bracket v 187y secured to the car frame. In the stopping operation, upon the deenergization of the leveling switch motor, a s ring (not shown) moves the lever 182 an therefore the leveling switch back into the first described osition with the rollers 183 and 184 extended for engagement .by the leveling cams. Each pair of leveling switch contacts 34, 35, 36 and 37 comprises a stationary contact and a movable contact o erated by the engagement rof its corresponding roller and leveling cam.l The fast speed contacts 36 and 37 are arranged .to separate before their corres ondingslow speed contacts 34 and 35 in t e leveling operation. Springs (not shown) are provided for causing the separation ofthe contacts of the pairs as the leveling o ration is effected and stops are provided or determinin the extent of movement of the rollers as t ey ride off the leveling cams.

It will be aumed that the car has underrun the landing and that the up leveling switch operating roller 183 moves onto the vertical surface yof up leveling cam 185 before relay M drops out. The engagement of leveling switch up slow speed contacts 34 completes a circuit for the u leveling direction switch actuating coil B 188 and the leveling brake and field switch actuatin coil LH 190. This circuit may be traced from .the left-hand blade of switch 47, by way of line through contacts A 60, line 191, levelingy switch contacts 34, by way of line 192 through coil LB 188 and coil LH 190, line 85, to the yright-hand blade of switch 47 as prevlousl traced. The engagement of ythe leveling switch up fast speed contacts 36 completes the circuit for fast speed leveling relay actuating coil LF 193. This circuit may be traced from the left-hand blade of switch 47,-by way of line ythrough contacts A 60, line 191, leveling switch contacts 34, line 194, leveling switch contacts 36, by way of line 85 through coil LF 193, kto the right-hand blade of switch It is to be understood that.

loo

47 as previously traced. It is to be noted' that, due to the fact that the circuit for ycoil LF 193 is through leveling switch slow speed contacts 34, the circuit for coils LB 188 and LH 190 must be madein order that the circuit foifcoil LF 193 mayk be Completed.

The up leveling direction switch LB, upon operation, causes the separation of contacts LB 132 andthe engagement ot contacts'LB 195, LB 196 and LBv 197. Contacts LB 132 lwillbereferred to later. Contacts LB 195 and LB y196prepare a circuit for the gen'- erator` auxiliary icldwinding 18; The engagenrent of contacts LBr 197 completesthe circuit for up' series icld relay actuating coil G .198 kand up hard brake switch actuating coil 200. This circuit may be traced from the lett-hand `blade* of switch v47, by

Way of line through, contacts A 60, by way of line w1 through contacts LB 197,coil Grk l 198,coil`P 200,r and portion 202 of reactance 0X 203,line 204, by way otline 58 through Switchfl does not drop out.

contacts A 61, to the right-hand blade of switch 47. r

The leveling'brake and field switch, operating simultaneously with the up vleveling direction switclncauses the separation ot contactsLH 205, LH 206k and LH 212 and the engagement of contacts LHf207`and LH` 208. Contacts LH- 205 are in the circuit for resistance 33 across the brake release coil.

Contacts LH 206 are in serieswith'contacts H 119 in the' circuit t'or 4connecting the generator separately excited ield winding to the generatorarmaturef Contacts LH 212 break the shuntlcircuit, comprising rcsistance' 160, for coils D 161 andl M 162. Contacts' LH 207 y ley-pass contacts H 124 in the circuit for the brake release coil. -Con-l taets LH '208 by-'pass contacts H 126in the c'ireuitfor section 54 oit' the motor fieldy resistance 29. The nirpose o1 contacts LHL 205, LH 206,`LH 20 LH 208 and LH 212 willbe seen as the descriptionproceeds.

- The fastispeed leveling relay, .uponoperation,l causes the engagement of contacts LF 213 and LF'214. "The engagement of contacts LF 213 short-circuits resistance 28 employedfduring leveling to reducel the flow of current through the generator auxiliary. field windingtor slow speed operation.` The engagement ot contacts LF 214 fby,

passes-switch 78, as well as contacts LB 132,

Lo isa, n.127 and Kia@ and @on K13@ through resistance 84, in va circuittor .coil

J 82 ofv the door control motor switch.`

Since the engagement otcontacts LFK214l generally occurs substantially simultaneously with the separation of contacts LB 132, the Even it' switch J should drop out, the immediate reenergiza-l tion of coil .l 82-upon the engagement o y contacts LF 214 would prevent jthe operation ot the gate and door ,operating mechanism due Ato the time required for the mechanism to start in operation.l The circuit for thel door control motor maintaining relay coilv K 130, howeveig'lis broken by the separation of contacts LB 132.

The separation f of contacts LH 212 to set forth causes relay -Mto drop out and separate'contacts M 164. As ya result the circuit for holding coils B 115 and H 116is` broken, permitting the up main direction'- switch and kmain brakev and ield switch to drop out. Switch B, upon dropping out, causes the separation o1 contacts B 109, B

V111, B 112 and'B 113 and the engagement ot' contacts B 110. The separation of conbrealr the circuit for resistance 160 as above tacts B 109 and B 113 and the engagement of contacts B 110 V is in preparation for the' next starting operation. It is to bcA notedA that so long as load switch contacts Q 117 remain separated, the actuating coilsDB 121 andUB 11S of the retarding relays are not energized upon the' engagement otcontacts B109 or C 169. lt is being assumed in the present example that contactsQ 117 remain separated. Thus the separation oit contacts B 109 is without effect. The separation ot contacts B 111'and B 112 breaks the circuit for the generator main field However, 4the auxiliary field winding is coiitacts'H 122 ot the main brake and field switch' H as set forth below. he switch H, upon dropping out, causes the separationy oit. contacts H 124, H 125, H. 126 and H 127 andthe engagement of contactsH 119, H

122 and H 123. The separation of contacts H 125 and H 127 in preparation for the next starting operation." The separation of contacts H 124 and .H1126 is without-effect, the circuit vfor the brake release coil 30 bcing maintained by contacts LH 207 and sec-y release coil. 30 comprising resistance 33- is maintained broken by contacts LH 205.

winding. v

ysinlultaneously connectedto the mains by `The engagement of contactsH 122, however,

completes the circuit tor the auxiliary field winding 18., This circuit may be traced from the jlefthand blade of switch 47, by

-way oi line 55through contacts 60, by

way of line 215 through contacts H 122 and n contacts LF 213, by way ot' line 242 through contacts LB and up retarding relay eontactsI UR r240,' through. field winding 18, kback torline 215` through contacts'LB 196,

by way of line 58through contact-s 'A 61, to

f the right-handy blade of (switch 47.:r lVith contacts LF 213 in engagement, shortcircuitingresistance 28,v an E. M. F. isgeneratedl which causes the elevator motor vto run at a suitable fast leveling speed. Discharge resistance Q4 acts not only to smooth out the changes in generator E. M. F. due to the reinsertion of resistance Q7 in circuit with the main field winding in steps but also acts to prevent. a. sudden drop in value of the E. M. F. upon changing over from the main to the auxiliary field winding. It is to be understood that resistance Q7 may be controlled in any number ot steps, two being shown merely for convenience of description.

Relay G and switch P do not operate immediately their actuating coils are energized, their action being delayed by reactance X S203. Switch P, however, is adjusted to operate almost innnediately and, upon operation, causes the separation ot contacts P Q21, disconnecting resistance from across the brake release coil 30. Relay G. upon operation, causes the engagement of contacts G 222. completing the circuit for the series field switch actuating coil F Q23. This circuit may be traced from the lett-hand blade of switch 47, by way ot line through contacts A 60. by *ay of line 221 through contacts G 2:22 and coil F 223. by way of line 58 through contacts A G1. to the right-hand blade ot' switch 47. Switch F, upon operation, causes the separation ot contacts F 2:25, breaking the circuit including resistance 23 in shunt to the generator series field winding 16. The generator series field is so wound that.. without the parallel resistance 23, it would have too great an effect for proper operation of the car. `The desired compounding is obtained by employing the low resistance shunt. Upon separation ofcoutacts F 225. the strength of the series field is increased for the leveling operation so as to aid in bringing the motor 'to a stop. The short delay in the action of relay G, and

therefore switch F, upon the initiation of` the leveling operation, is desirable in order that the current Yin the generator armatureelevator motor armature circuit may adjust itself to such a value that proper series field strength during the leveling operation may be obtained. 1

As the car nears the third floor landing, roller 183 rides oil" the vertical surface onto the oblique surface of cam 185. .This revsults in the separation of leveling switch up tast speed contacts B6, deencrgizing fast speed leveling relay coil LF 193. .Relay LF, upon dropping out. causes the separation of contacts LF 213 and LF 214. The separation of contacts LF 213 removes the short circuit for resistance 28. The generator E. M. F. is thus lowered and the elevator motor runs at its slow leveling speed. The separation of contacts LF 214 breaks the circuit for the door control motor switch coil J 82. Switch J, uponv dropping out. causes the separation of contacts J 87 to deenergize the motor 44, thus efeetingthe automatic gate and door opening operation. The gate and door operating mechanism functions in -the same manner as described for opening the gate and door in response to centering the car switch. In this manner the automatic gate and door opening operation is timed so that the gate and door open as the car stops at the landing. It is to be n0ted,-however, that the automatic gate and door opening operation cannot take place until the' leveling switch fast speed contacts separate.

Shortly before the car reaches the exact level with the landing. the roller 183 rides off the obliqnelsurface of cam 185, thereby separating the leveling switch up slow speed contacts 34. The circuit for coils LB 188 and Lll 190 thus broken. Switch LH drops out, causing the separation of contacts LH :20T and LU Q08 and the reen agementof contacts LH 205, LH 206 and L 212. The engagement of contacts LH 212 is in preparation for the next starting operation. The sepa ration of contacts LH i207 breaks the circuit for the brake release coil 30, effecting the application of the brake. The separation of contacts LH Q07 also breaks the circuit for the accelerating relay coil O 138. The accelerating relay O drops out, separating contacts C) 140 in preparation for the next starting operation. The separation of contacts LH 208 reinserts section 54 of resistance 29 in series with the elevator motor ficld'winding, reducing the current therein to a standing field value. The reengagement of contacts LH 206 reconnects the generator main field winding to the generator armature. The polarity of this connection is such that the generator sends current through the field winding lin such manner as to oppose the .flux which produces the generator F., thus tending to destroy the residualv flux of the `generator field.

Up yleveling direction switch LB, dro ping out simultaneously with switch L l. causes the separation of contacts LB 195.` LB 196 and LB 197 and the engagement of contacts LB 132. The engagement of contacts LB 132 is in preparation for the next starting operation. The separation of contacts LB 195 and LB 196 disconnects the generator auxiliary field winding from the mains, the main field winding being simultaneously connected to the generator armature by contact ILH 206, as set forth above. The separation` ofy contacts LB 197 breaks the circuit for coils (ir 198 and P 200. The relay G drops out immediately but the dropping out of switch P is delayed slightly due to the effect of the reactance X 203 and discharge resistance Q26. It is to be noted that the discharge current for up coil P 200 and the reactance passes through down coil P 227 in such direction as to cause coil P 227 to assist coil P 20() in maintaining switch P iok in operated conditionl A Relay G, 'uponr dropping'out, causes the separation of contacts Gr 222 to de energize coil F v223, switch F 'dropping out inturn to cause the engagement of contactsr F 225. The engagement of ycontacts F 225 recomiectsresietance 23 in parallel with the generator series field winding 16. Switch P, upon dropping out, causes the engagement of contacts P 221. l

Thus t-hebralre being applied and the erator separately excited fieldwindings heing disconnected fromthe mains, the car is brought to .rest level with the thirdfloor landing.

` stopped level with the desired landing with-' out sacrifice of smoothness. However,

should the car switch be centered with the car at a greater distance from the landing, the maintaining relay would hold in' to efi'ect, through its contacts M 164, the retention-of the main direction-switch and main brake and field switch in operated condition.

vShould relay M drop out before the leveling switch contacts engage, the subsequent engagement oi the leveling switchl contacts `as the leveling switch roller rides onto the cam would cause the operation of switches LB and LH and relay LF to bring thecar to a level with the floor. kIn the event that the car switch iscentered late in the stopping operation, kas for example when the leveling switch operating roller strikes the leveling Vcam upon the dropping out of the first ac-A celerating switch D, the immediate separation of contacts LH? 212 forces the dropping out of the main direction switch and the main brake and field switch to permit the yimmediate change of connections for the field windings and thus slow down the Velevator motor more rapidly. In this manner the tendency for the car to overrun the floor is reduced.

Should yan overrun occur, however, the

, system is arranged so that the operationv of the switches is modified. Assuming in the above example that the car overruns the thiil fioor landing to the extent of causing the engagement of leveling vswitch down slow speed contacts 35, a circuit is completed for down leveling direction switch actuating co'l LC 22S and coil LH190. This circuit may be traced from the left-hand blade of switch 47, by way of line 55 through con- '..acts A 60, line 191. contacts 35, by way of line through coil LC 228. by way otline 192 through coil LH' 190, line 85, Ato the right-hand blade of switch 47 as previously 212 insure the dro) Jin@ out of the main y low value.

l traced. Contacts 'LH 205, LH 206 and LH 212 are separated land contacts LH 207 and 1111208" are engaged so that the circuit for resistance `33 across the brake release coil is broken, the generator main field winding' is disconnected from the generator armature, the hralre release coil is energized and re-l sistance section 54for the elevator motor iielld winding is short-circuited. Contacts direction switch. yIhe switch LC operates to cause the sepa-ration of contacts LC 133 and 'the engagement of contacts LG 231, LCy 232`and L@ 233. The,separationA of contacts L@ "133 is without particular effect at this time. i The engagement of contacts LC 231 ,and LC 23,2 connects the auxiliary field winding to the mains through down retarding" relay contacts DR 241. Dueito the reversal of the flow of current through the auxiliary field winding from Ythat during the leveling operation with the car approachingthe iioor in the up direct-ion, the

caris sed to start kin the'down direction. rSince relay LF is not operated, resistance' ,23 'is included inthe vcircuit for the auxiliary ield winding,

causing the motor to run at siow leveling speed.

The engagement of contacts LC 233 coinpleted azcircuit for the down kseries field 'relay actuatingcoil Gr 234 and the down hard brake switchy actuating coilk P 227. This circuit may be traced from the lefty.hand blade of switch 47, by wayof lineV 55 through contacts A 60, by way of line 235 through contacts LCy 233, coil G 234, coil P 227 and portion 236 of reactance X 203, line 204, by way otline 58 through contacts A v 61, to the Vright-hand blade of switch 47. kBel-ay G' and switch P do not operateim- `mediately upon the engagement of contacts L@ 233. lllhen approaching the floor in the lup` direction, the current flowing through reactance portion 202 caused a flux to be built up inthe reactance X 203 in one direction. Upon the separation of contacts LB 197, the current in the reactance and lcoil, P 200discharged into resist-ance`226 'tending to maintain the flux built upland,

as previouslyexplained, switch P in operated condition. Upon the engagement of contacts LC 233 on the overrun, `the current supplied to coils Gr 234'and P227 must reve-rse the flux in the reactance, thus taking a longer time to build up to a value suiicient te cause the operation of relay G and switch P. rihus contacts F 225, depending for their operation upon the operation of rela-y Gf, remain closed momentarily Vto insure that the current in the generator armature-motor armature circuit has yfallen to a As the car is brought to rest upon an overrun .in the up direction, the current inthe series field winding, owing to-y the tact that the motor may be acting as a generator, may be {iowing in a direction Such as to cause the generation of an E. M. F. which is ot properpolarity for operatin the car in the down direction. Under suc i conditions, immediate increase in the strength et the series tielcl might result in an overrun in the down direction. iVith the operation ot switch F delayed, however, the immediate increase in the strength of the series field, and therefore the bouncing back ot the car past the 'l'loor upon its return to the floor, is avoided. As the car returns to the Hoor, it is stopped by the separation of 'the leveling switch slow speed contacts 35 in a manner similar to that described for approaching the door in the up direction.

It' the overrun is great enough to cause the engagement ot the leveling switch down tast speed contacts 37 as well as the leveling switch down slow speed contacts 35, coil LF 193 is energized. As before, relay LF causes the engagement of contacts LF 213 to short-circuit resist-ance 28, increasing the generator voltage and causing the elevator motor to run at its tast leveling speed. Relay LF also causes the engagement of contacts LF 21-1 to energize coil J 82 again in the event that it has become deenergized. Upon such an overrun, the automatic gate and door opening operation does not occur until contacts LF 214 separate, as previously described. Further than this, the operation on an overrun is as above described.

t is to be understood that the operator may control both the acceleration and retardation of the car by moving the car switch in steps. Should the operator suddenly move the car switch from one position into the other, :'or example from up into down position, injury to the system is prevented by contacts B which remain separated until the up direction switch drops out. It is to be noted that, when the car is suddenly reversed or stopped between floors or stopped by opening the safety switch 50, the switch P is not operated. Thus contacts l? 221 are in engagement and a sott application of the brake is obtained.

Load conditions ha rve not been considered inthe description of operation up to this point. When the circuits are completed for returning a fully loaded car to the floor after an overrun in the up direction, certain ,conditions exist which tend to bounce it down past the lioor. Similar conditions are present when circuits are completed for returning an empty car to the floor after an overrun in the down direction. This bouncing tendency is principally the result of the action of the current in the generator armature-motor armature circuit. For convenience of description, it will be assumed that the car in the previous example was uily loaded and was not brought to a standstill until it had passed three or four inches above the third floor landing. The current in the generator armature-motor armature circuit, just as the car is brought to rest is substantially zero.

Also the brake shoes are released. Thus the tendency of the load in the car is t'o return it'to the floor. Upon the operation of the down leveling direction switch LC to complete the circuit for the generator auxiliary iicld winding 18 in the proper direction to return the car to the floor, the action ot the generator auxiliary field Winding, without retarding resistance 39 included in its circuit, would be to cause a rapid rise in the E. M. F. of the generator. .As a result, the current in the generator armature-motor armature circuit would rise very quickly' and would be in such dircctionas to cause the series field winding to assist the auxiliary field winding in causing the generation of an E. M. F. for returning the car to the floor. Although such elfect of the generator series lield winding would bc only momentary, due to the rapid rise in value of the counter E. M. F. of the elevator motor, nevertheless, before the current in the generator armature-motor armature circuit had fallen to a suiliciently low 7alue or had reversed due to regenerative action of the elevator motor, this effect of the generator series field winding would cause the car to a ain overrun or bounce` past the floor. Thls objectionable effectis overcome by means of the resistance. 39 controlled by thek down retardingr relay and the load switch.

The load switch is provided with a current coil Q 250 arranged in the generator armature-motor armature circuit and a voltage coil Q. 251 connected to the generator armature. These coils act .cumulativcly when the elevator motor is lifting a load and are adjusted to cause the operation ot the switch between balanced and full load conditions, depending upon the particular installation.y Upon operation of the load switch, contacts Q 11T engage to complete the circuit for one of the retarding relay actuating coils. Ifthe car is moving upwardly, contacts B 109 are in engagement and contacts Q. 117 complete the circuit for the down retarding relay coil DR 121. This circuit may be traced from the left-hand blade of switch 4.17, by way of line through contacts A 60, by way of line 2:32 through contacts Q 117, contacts B 109, coil DR 121 and portion 253 of reactanceX 254, line 55, by way7 of line 58 through contacts A ($1. to the right-hand blade of switch 1T. The down retarding relay, upon operation, causes the separation of contacts DR 241 to remove the short circuit for down retarding resistance 39. The down retarding resistance performs no function during the leveling operation to bring the car to the floor in the event of an underrun as the circuit for auxiliary iield winding 18 is completed by up leveling direction switch contactsLB 195 and LB 196; down leveling direction switch contacts LC 231 and LC 232 which control the circuit for winding 18 including resistance 39 remaining separated. The circuit for down vretarding relay coil DE 121 is broken by the separation of up main direction switch contacts B109. The lor-.d switch is preterably adjusted to hold contacts Q 117 Ain engagement until a `low value of inagnetizing torce is reached in its inagneticcircuit, thus tending to prevent vthe deenergization of coil DR121ibeitore contacts B 109 separate. The down retarding lrelay does not V-drop out immediately the circuit for coil Dit 121 is broken, however, its action being` delayed by the eiliect ot reactance portion 253 yand* discharge resistance/256. With relay Dit maintained in operated condition, therefore, kcontacts DR 2411 remain separated, so that, continuing the above example of the fully loaded car stopped three or `tour inches above the landing, upon the engagement of contacts LC 231 and LC 232 to eliiect the return of the car to the landing, the circuit for the auxiliary tield winding 18 -is completedy through down retarding resistance Resistancev39 acts to prevent the building up ot' the ,generatorl ield due to the magnetizing 1 force exerted by the auxiliary held winding to such a value as would result in action of the generator series lield kcausing the ycar to be carried past the floor in the down direction. The relay DR isadjusted to maintain the contacts DR 2st-1 separated and resistance v39 inserted in circuit with winding 18 long enoughtorthe current in the generator are mature-motor armature circuit to adjust it vie' self to a suitable value after which itdrops` out permitting the car to finish leveling in the normal manner. y U Similar operation is had in the event that the car is moving downwardly under light load conditions,ji. e., the elevator motor litting the counterweight. The load switch Q operates to complete the circuit for the .up retarding relay f actuating coil UR A118 through contacts C 159. Relay Ulti upon operation, removes the short circuitfor the upretarding resistance 19 for insertion inr the circuit ofthe auxiliary ield winding 18 upon the engagement ot contacts LB 195 and LB 196 to return the car to' the landing after an overrun in the down direction. The delayed action for this relay isA obtained by discharge resistance 257 and portion of reactance X 2511. Resistance 19. as iny lthe case-oic resistance 39, performs no tunetion during anunderrun.' r-

kIt desired, load lswitch contacts Q 117 may be employed to complete a circuit for the actuating coil `oi a relay whichy once operated, is maintained so until the car is ing relays.

brought to final stop andy which is Vprovided with contacts arranged .inthe circuit ytor the coils ot' the. retarding relays UR and DR in lieu of load switch contacts'Qv `117. lVith such an arrangement, the prevention ot the deeneigization of the retard ing relay coil before the main direction switch kdrops out ris assured. A suitable arrangement for this purpose is illustrated in Figure 23. Only such portion ot the con- -trol system as relates to this arrangement is kcontacts Q` 117101l the load switch in the circuit tor tl e actuating coils ot theretard- Contacts Q 117 are ,arranged in .a circuit for the actuating coil QR 262 of kthe load relay to by-pass holding resistance 260. Contacts HR 263 of the holding relay also are` in the circuit for coil QR 262. The actuating coil HR 261 of the holding relay may be arranged in series with the brake release coil 30.

Dui-ing starting, the engagement of contacts H 124C completes the. circuit for `the holding relay actuating coil HR 264 as well as the bralre release coil 30, The holding relay operates to cause the engagement o'l" its contacts HR 263. in the circuit 'for coil QR 262 of the load relay. It is to be understood that the ohmic value of resistance 260 is such as to permit the passage ofsutlicient current through coil QR 262 to maintain the load relay operated but not enough to causek its operation.' Thus, the lload relay does not operate unless the load switch operates to cause the engagement ot its contacts Q 117', by-passing resistance 260.- vThe load relay, once operated, is maintained inoperated condition by the holding relay contacts HR 263 until the car is brought to a inal stop. The holdingrelay is maintained in y operated condition until the car is broughtv to a final stop, even though an overrun occurs, owing to the tact that its actuating coil is cont-rolled by contacts H 4124 and LH 207.' Should there he interval that the brake release coil 3() and coil HR 262 are disconnected from the mainsas an overrun occurs, the holding relay is maintained in operated condition by the brake release coil discharge current. Thus, contacts QR 261, once in engagement, are maintained kso until the car is brought-to a final stop, pre

venting the deenergization of the coil oi' either retarding relay before the main direction switch drops out.

It may be desirable in certain case cause the insertion of the retarding res`^t ances in the field winding circuit `for arf- 'f'erent periods of time for the operation of rcturninor the elevator car to a landing utter an overrun, these periods corresponding in some manner to the load being lifted by the hoist-ing motor prior to the leveling oper tion. That is, if the motor has been full load prior to leveling, the retar resistances are inserted for a certain p of time While, it the motor has been l ning less than full load prior to leveling, the resista-nces are inserted for a shorter period of time` the period of time becoming less as th condition is approached Where the load in the car approaches balanced load. Such operation may be obtained by arranging the load switch Q to cause the breaking of the circuit `for the coils ot' the retardinfr lays by its contacts Q 117 rather t, by main direction switch contacts l l?) or C 169 and by setting the retarding rela and the discharge circuits for their coils so that the period of time during which the retarding resistances are included in the field winding circuit is proper for the operation of effecting the return of the elevator car fo ythe landing after an overrun ivhere the motor has been lifting full load prior to the leveling operation. Then` if the motor has been lifting less than full load prior to leveling, the period oic time that the retarding rcsistances are included in the field Winding circuit Will be less since the load switch drops out sooner in the rstopping operation. This may be readily seen from the fact that when the load which the motor is lifting during running is near balanced load, regeneration may occur during stopping to reverse the current in the generator armature-motor armature circuit and therefore in the current coil Q Q of the load switch to cause the current coil to act in opposition to the voltage coil Q 251. Thus the more nearly the load in the elevator car approaches balanced load the sooner the load switch drops out. during stopping and the shorter the period during which the retarding resistances are included in the field Winding circuit for the operation of effec ing the return of the car to the landing after an overrun. By causing the insertion of the retarding resistances in this manner for ditferent periods of timer` depending on the load being lifted by the hoisting motor prior to leveling, the elevator car is caused to be returned to the landing in av minimum ol time regardless of Whether the eleif'atory motor has been lifting full load or loads between balanced and full load. lt is to be noted that the anti-bounce feature is retained for all such load conditions. This may be seen, by way of example5 from the operation of effecting the return of the elcvator car to the landing after an overrun where the load on the elevator motor prior to leveling was near balanced load. Under such conditions of operation, the tendency of the car to be carried past the landingT upon its return after an overrun is not a; 'treat as vvhere the load on the motor was near full loadx Thus the inclusion of a retardingresistanco in the field Winding circuit for a shorter period of time is sufficient.

Gn the other hand, it. 'may be desirable to have the retarding relays operate directly without any dependency upon the operation of' the load relay Q, i. e., it may be desirable to insert resistance 39 in the circuit ot' the auxiliary field winding fort-he re irn of the car to the landing after an overrun in the up direction, and resistance lf after an overrun in the down direction, regardless of the conditions of load. Such an arrangement is illustrated in Figure l. In such event. the load s witch may be omitted.

Although the retarding rcsistances are illusrated as arranged for inclusion in the auxiliar)- field Winding circuit. it is to be understood that they may be arranged for inclusion in the circuit for the main field Winding when no auxiliary field windingr employed. Y

As many changes could be made in the above arrangement and many zuiparcntly Widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

lVhat is claimed is:

l. In combination, an elevator carl` a hoist-- ing motor therefor, a generator for supplying current to the motor, means for causing the motor to bring the car to a` level with adesired landing in stopping, regardless of Whether it underruns or overruns said landingyand means controlledby the first named means for establishing a field strength for the generator of less value for the operatitm of returning the car to said landing after an overrun than for the operation of bringing the car to said landing upon an underrun.

2. In combination, an elevator car. a hoi ting motor therefor, a generator for supplying current to the motor, said generator having a field winding, means for raus-ing said motor to level the car with a desired landing in stoppinv`r regardless of whether' it underruns or overruns the landing. and means tor rcausing the application of less voltage to said field winding upon the operation of the first named means to cause the motor te return the car to the'landing after an oif'errun than upon its operation to causel car to the landing after an overrun than Jivhen it isy connectedfor effecting the bring-- i ing ofthe car to the landing upon an underrun.

et. ln coinbii'iation, an elevator car, a hoist motor therefor, a generator for supply-- ing current to the motor, said generator hav ing ya field winding, a source of current, a resistance, means forcausing said motor to level the car With a desired landing in stopping, regardless of Whether it underruns or overruns the landing, said means comprising means for connecting said Winding to said source, and means for inserting said resist ance in circuit with said Winding only for the operation of said iirst'nained means to cause the motor to return the car to thelandafter an overrun.

5. ln combination, an elevator car, a hoisting motor ytherefor, a generator for supply current to the motor, said generator hav ing ' ing field Winding, a source of current, a

resistance, means rfor causing said motorto level Jthe ear With a desired landing in stop ping, regardless of Whetherit underruns or overruns said landing, said means vcompris-- ing` means for connecting said Winding to said source in circuit lwith said resistance when the car is to be returned to the landing after -an overrun and4 for connecting said Winding tothe source vWithout said resistance n in circuit when the car is to be brought to thelanding upon an underrun.

.6. ln combination, an elevator ear, amotor for raising and lowering the car, a generator for supplying current to said motor,

means for causingthe motor to level the car with a desired landing in stopping, regardl said landin causing current of a certain value to beL sup-` less of Whether it underruns or overruns g, and means vfor momentarib7 plied to said Winding upon the operation of the first named means to return the ear tothe landing afteran overrun.

'l'. In combination, an elevator car, amotor for raising and lowering the car, agenerator for supplying .current of said motor, means for causing the motor to level the car nination, an elevator car, a hoist- With a desired landing in stopping, regardless of Whether it underruns er. overruns the landing, ineans'for causing lesscurrent to fioivthrougli said Winding during the oper-y ation kof the first namedfmea'ns upon the oar being returned to the landing after an overrunthan upon being brought to thelanding upon an underrun, and means for rendering a the second'named meansinell'ective upon the expiration of `a 'predetermined time interval after the initiation of the operation 'of the first named means. Y y V `8v. In combination, 'an'.elevator car, va motor for raising and lowering the car,la generator for supplying current to said motor, said generator havingv a field Winding, a source of current for said field Wind-y ing, means for causing the motor to level the car with a desired landing in stopping, regardless of Whether itk underruns or overruns the landing, and load responsivemeans yfor vcausing the excitation of' said generator, dueito saidwinding during the operation of Y said first named means to cause the motor to return the car to the landing after an overrun, to be less than that due to said Winding for the operation of the first named means to cause the motor to bring the oar tothe landing upon an underrun.

9. ln combination, an elevator car, a

motor for raising and lowering the ear, a generator for supplying current to said motor, said generator havinga field Winding, a sourceof current for said field Winding, means for causing the motor te level the ear With a desired landing in stopping, regardless ofpivliether it underruns er overruns the landing, and means responsive to the load on the motor for momentarily causing ythe excitation of said generator, due to said rWinding during the operation .of said firstnamed means to Cause the motor to return the car to the landing after overrun, to

'be less than that due to said Ywinding for the operation of the first named means to cause the motor to rbring the'car yto the landing upon an underrun. f l0. In Combination, an elevator oar, a motor for raising and lowering the car, a

generator for supplying lcurrent to said motor, said generatorliaving a field Winding, a source of current for said field Winding, means for causing the motor to ylevel the carwvithva desired landing in stopping, regardless of Whether it underruns or overruns the landing, and means responsive to the load on the motor prior to the operation of Athe first named means for causing the excitation of said generator, duev to said v.Winding during the operationo'f the first nained means to cause theinotor to return the car to the landing after an overrun, to be less'than. that for the operation of the first namedv means to .cause the motor to lOG bring the car to the landing upon an underrun. i

11. 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, a resistance, 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 means comprising means for connectingsaid Winding to said source, and means tor causing said resistance to be momentarily included in circuit with said Winding only during the operation of said first named means to cause the motor to return the car to the landing after an overrun. r

12. In combination, an elevator car, a hoisting motor therefor, a generator for supplying current to said motor, said gcnerator havinga field Winding, a source of current, a resistance, means for causing the motor to level the car with a desired landing in stopping, regardless of Whether it nnderruns or overruns the landing, said means comprising means for connecting said Winding to said source, and means responsive to the load on the motor prior to the operation of the first named means for causing the xnome'ntar inclusion of said sired landing in stopping, regardless of whether it underruns or overruns the landing, said means comprising means for connecting said winding to said source, and meansfor causing one of said resistances to he momentarily included in circuit with said winding during the operation of the first named means to cause the motor to return the car to the landing after an overrun in one direction and for causing the other of said resistances to be momentarily included in circuit with said winding during the pei-ation or" the first named means to cause the motor to return the car to the landing after an overrun in the other direction.

In testimony whereof, I have signed my naine to this specification.

HERBERT L. HEART.

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