US986243A

US986243A - Alternating-current elevator system.

Info

Publication number: US986243A
Application number: US39562707A
Authority: US
Inventors: August Sundh
Original assignee: Otis Elevator Co
Current assignee: Otis Elevator Co
Priority date: 1907-10-02
Filing date: 1907-10-02
Publication date: 1911-03-07
Anticipated expiration: 1928-03-07

Description

A. SUNDH. ALTERNATING CURRENT ELEVATOR SYSTEM, APPLICATION FILED OGT.2, 190T.

986,243 Patented Mar. '7, 1911.

F j 3 SHEETS-SHEET 1.

i/ U .P

A SUNDH,

ALTERNATING 0113mm ELEVATOR SYSTEM, APPLICATION FILED OOT.2,1907.

Patented '7, 1911.

3 SHEETS SHEET 2 Z2972; W 7y A. SUNDH. ALTERNATING CURRENT ELEVATOR SYSTEM.

APPLICATION FILED ()OT, 2, 1907. I 986,243. .Patenmd Mar "2, @911.

3 SHEETS-SHEET 3.

MW A. 4 fi 7 Tm M F LMJ n.

.Be,,it known that I, AUGUST" SUNDH, a

citizenf thei'United States, '-residingin Fig. l are shown by heavy lines, andthe controllin circuits by light lines. A main- Yonkers, in the county of Westchester and 5 stateeof-New York, have invented a new and i'useful Improvement in Alternating- GlirrentvElev ator Systems, of which the folulow-ings-is aspecifi'cation. j -Mydnvention relates; to alternating curie rent :el'evator systems, and one of its objects is thewprovisi'onf of-a simple and efiicient control Lsystem for alternating "current moattors, which system shall be substantially noiseless in its operation.

Although my improved control system is particularly adaptedjto alternating current electric motors connected in elevator sys items, it niay'ha-ve a. general application.

More particularly it -is one'ot' the objects of ny' invcntion to provide means for automatieallycontrolling the speed with which the' inot-or"controlling switch is operated. 'A' fnrther object of the invention is the provision of means to automatically limit thesp'ecd o f movement of a manual switch in one-direction.

A- further' object.is to provide a mechanical'.;device releasable manually and movable automatically atv a predetermined rate'of a0 speed'io' cited a predetermined acceleration of an electric motor. ()theeohjeets of thc inrention will appear hereinafter, the' novel combinations of elemoms being pointed out-in the appended claims.

Referring to the accompanying-drawings in-Wvhich are shown constructhms embodying 'my invention, Figure 1 is a diagrammatic-view or wiring diagram'of a motor '40 .with-its circints. and switches as used in an elevato'rfsy'stem; Fig. 2'lis a front elevation partly-in section of a switch wit-h automatic f -retarding-rneans; Fig. 3 is a sectional side elevation of the same; Fig. 4 is a view simi- 45'.lar"to Fig.2 of a n'lodification'; Fig.5 is a sectional view on an enlarged scale takenon the-line V-V of Fig. 4; Fig. 6 is a detail view of the relief valve for the dashpot'; and Fig. 7 is a detail \ltW of the M swite-l'u handle. In Fig. 1 isshown a motor and system of cireuits a da'pted for use with av three-phase "a-lternating current. It should -be understood, however, that the switch hereinafter Specification of Letters Patent. Applicationjiiled Qctober 2.1907. Seria1 i{o. 395,627, I I

srsdnDrI, ondss s, ,ronxiassranon ro' o'rr's nnnvn roncomramr; r for' EnsEY CITY','.' N EW: JERSEY, nconronarrouor 'nEw JERSEY.

nn'rsniva r'm'e-cunnsnr ELEVATOR sYs'rnM.

Patented; af er. 7, 1911'.

ternating current, intermittent current, or: even direct current. The motor circuitsin line switc 1 S connects 'therr'notor Mto the conductors, w,.y, a, leading jfromthe source of supply- The' -middle-pol'e or blade-of the switch .8 is connected directly to the stator ofthe motor b'yut-he'c'onductor 1, and the outsidepoles on blades are connected to. the stator th-roughuthe potential switch Band tively, which are carried by the core of the prises 'fixedcontacts 9,10 and 11, 1.2, ar-

by the cores of the magnets 17- and 18. The starting resistance in this instance is shown star-connected and in sections, and is designated by the reference character X. This resistance is connected in the rotor circuit by the

conductors

96, 97 and 98. The several sections a 5 ,0, (5 are arrangedto be successivelyshort-circuitcd by the switch a, I), c, (l, operated by the magnets a,- 1 ,0, d, respectively. When the motor controlling apparatus is used in an elevator system the following automatic switches may be placed in the circuit of the potential switch magnet.8:upper and lower limit switches 17 t which effect a stopping of the motor when the ear goes beyond its normallimits of travel; a slack ca'ble switch 18' associated with the drum of the hoisting apparatus on which the hoisting and counterweight cables are wound; and switches'necessitating tric 'motors operated other 'ltinds of 51 the reversing. switch 1 R.= ..l he potential; switch P. maybe of any type desired, and in this instance is shown as comprising,

fixed contacts

2,3 andt which are arrangeditobef engaged-by the eontacts fi, 6.and' 7, -,i espec;-

the closing of the elevator well'doors before the car can be started. In the circuits of the 'reversing'switehmagnets 17 and-1'8 may iii . neoted to-the piston 50 is a lug'51 to which is pivoted a depending rod 52 andcam' plate: 53 composed of vulcanite orotherinsulating'j material is attached to the rod 52 by suitable means, as screws-54. This plate53 which in an elevator system is'usually cated in the car, will now be described.

The casing (see Figs. 2 and'3) which incloses the switch -mechanism comprises. a

back 22 and a removable front or cover 23.. 'WIthJn the casing-and secured to Oriormed integral with the back 22 are lugs 24 to which is attached for'instan'ce by mea us of screws'25, 'a bearing plate 26. Behind the plate 26'isa switch lever'27 having .a pivot pin 28 rigidly securedthereto and extending forwardly througlnthe plate 26 in which it is journaled. The portion of the lever 27 within'thecasing is in the form of a disk with portions ofithe'upper half removed to form a half ring and a center web 29. The lower portion of the disk issolid and thicker than the upper portion so as to be weighted and tend to swing the lever automatically to central position when released. A similar circular flange- 30 is formed on the upper part ofthe lever and fits loosely within the upper curved wall of the casing; A part 31 of the lever 27 extends upwardly through a slotinjthe easing anda handle 32 is connected to'its upper end. The portion of the pivot pin 28.; which extends forwardly beyond the plate 26 is of somewhat reduced diameter, and on this. reduced portion is meansof screws 39, for instance. This contact plateis, however, insulated'froni such extension by means of the inter osed insulation 40. -A plate orblocko insulating material 41 approximatelysemi-circular in shape is securedto-the stationary 'late: 26-' by the screws 42. On the face of t is plate; are connected a plurality, inthis instance..- four, flexible contacts 43, 44, 45'- and 46 in 1 such position as tobe wiped by the are shaped contact plate 38 when the latter 1s ro tated or oscillated. The lower contacts 44-, 45 are electrically connectedto ether .by the i The dash-pot conductor 84, as illustrated diagrammatically in Fig. 1.

D is located in the casing below the plate 26 andisrsecured in position by meansof-flanges 48Iformed integral with the dash-potoylinder, lugs -49 formed on the casing, and connecting screws 47. Conany has recesses 55 and-r 56 on opposite' sideswhich form cam surfaces. Preferably'these recesses are opposite each other, althoughsuch arrangement maybe varied as desired.

Contactcarrying plates 57 are secured to lugs .58 extending'from the back'22 ofv the 1 casing by means of screws 59, the arrangement being such thatthe plates 57. occupy f positions on opposite sides of the camlate 53. Connected to the plates-57 but insu ated therefrom, are four

contact levers

61, 62, 63

and 64 similar in construction and each pivoted by means of the pivot screw 65 to a lug .66 secured to a plate 57. Each lever has a cam roller 68 bearing againstthe plate 53 A and urged to such position by a coil spring 69. On opposite sides of the cam plate 53 are

stationary contacts

70 and 71 secured to the plates 57 but insulated therefrom, and located between the

levers

61, 63 and 62, 64, respectively, and in the path of movement with the .contacts 65 carried by the lever.

The rod52 extendsdownwardly below the cam plate 53 through a slot in a stationary guide 66 secured to the casing, and to its lower cndis attached a block 67. Connected to the switch lever 27 by a'pivot pin 68 is a depending rod 69 which extends downwardly to the block 67. The lower end of c i this rod is provided with'a slot 71 to receive the-pin 70 in the block 67. Theupper end of the dash-pot is provided with a relief valve V which may be such as illustrated in f Fig 6, and comprises an outlet 200, a restricted inlet 201, a ball check 205, an adj usting screw 202, and a locking nut 204. The 1 opening through the tapered slot 203 in the bolt-202 may be restricted to any desired degree by adjusting the latter. which is then locked in position by the nut 204. The ball.-

205 remains seated during the downward .movement of the dash-pot piston 50, the latter being thus retarded to an extent determined by the opening 2-03. The piston'50 may move freely in an upward fdirection, however, as in-such an event the airfabove the througl .--tlie open- 1 fistonj-may escape freely ihg 200 past thecheck valve-205.

extends upwardly from the cover 23 of the casing is formed a recess '74 tor ejceivje the In the upper edge of the fiangef73 which handle '32 and lock it in its central position.-

I preferto use-the type of handle shown in Fig. 7 where the bolt 75 ri 'd'withthe extension 31 of the lever 27 ts loosely in a'ri' to receive the coil spring 77 which bears at 'itsinner, endagainst-a circular shoulder formed by the differences in the'diameter' of the opening- 76.] "Theyiother 'endpfthis' spring 771gbears' againstithei-hendfid. of the bolt'-75.- The recessmi is further enlarged atits outer end to accommodate the bolt head 1'20 i opening 76 of the handle 32. This, open-'- a 1 ing extends'longitudinallythrough the ham tile and is enlarged for a portion of its length 78' and thejhandle to beypulledfoutrwar dly on the bolt beyond the flange 73. It will. th' v efore beseen that when the-ham dle 32j'i's in tl 1epositionshown in Fig. 7"

in the recess 74 the lever 27 cannot bemoved from its central position, being? obstructed by the flange 73. But whenthe' handle 32 i is grasped and pulled outwardly against'the action of thespring' 77 the inner end of such handle "is pulled out of the recess 74= g-.and;. awayjfronr the plane of the flange 73, so.

that thereafter the lever 27- maybe moved freely in either direction; When, the switch has been operated 'in' either direction the handle does: not need to: be brought back: to its.central lockecl position to'cut oil the currentand stop the motor,-; but may be brought up against either of the shoulders" 78, from which position itfn ijay be moved back toaagainstart' the motor in the same direction .as before; YVhen however, it is desired to reverse the motor the handle must be pulled out and nioved tocentralpositio'n and then beyond to the'revcrsed'position;

The handle ;,32 is moved to the leftas viewed in Fig, 2 and the movable contact plate ,38 will befbronght'into'position to bridge the contacts45:and 46. The rod 69will atithe same time be moved downwardly, its lower slotteduend sliding along the 1 pinf70 freely;

. No 'nially when'vt-heswitch lever"?! is incentral position the lower end of the rod 69 supports or holds the plate. 53,-rd 52 an d' piston iirtheir upper positionsas illustrated in Fig.1 Therefore.whenithelet'er 27 is rotated to the left'and therodea 10w;- ered the piston andrcam plate; will be released. The cam-plate and connected parts will therefore move downwardly by their} -'own weight, thismovement beingi retarded 'to any desired extentby the dash-pot: ":As"

the cam plate moves down, the cam roller 68 on thelever 61 is the firstxt-o ride into therecess 55 This permits the-lever 61 to be moved by its spring to bring" the con-:- tactinto engagement with the 'co-ntact'70. The lever 62 next cooperates with the re cess 56to cause the contact 65 ot said'lev'cr to. engage the-contact 71. The lever 61 "is then liftedto disconnect the contacts 65 and 7 O and thelever 63 is permitted to swing to bring its contact "into engagement with the contact 70. Then the lever 62 is brought;

. back to normal'positionand the contacts 65',

71 disconnected. The next step is the move-5 ment of .the lever 64 to bring'into' engagement itsy'c'ontact and the contact-7.1. By this time-thecam plate 53 has reaclled its lowermost] position. Thesuccessive order of operation-of the switches'may be varied as desired, but in this instance the switch levers areshown'mstagger'ed rela'taoaand the cam-recesses substantially opposite v each;

'bth'en WhenLt-he. cont-nollenhimdleuis-moved 90, I switches 18-,

' 0: the slot 71 immediatelylengagesi'tlie pin to'posititzely' lift" the cam plate',-'p 1ston and connecting parts, and-duringthis op.

in; the reverse 'order. This returnopgiiation 7'0 maybe-as rapid as :desired, as the'rod 69 nOW'engages the pin-379 and lifts theicam plate by: a positive movement ,and the relief I il t cl fore be"seen that -the?switch 8 5 and the centering spring'for the-actuating lever-27L ,1 r-fiIn-Figs. 4=-and v.i lfli'ave shown ai-modifi -cation"-of the retardingnmc-h'anism-"for. the I l -roller', in .which the dash-pot is replaced A by a 'fan 210 and connecting gearing. lo-a*-"- 'th'e s g is'- journaled? a.,1spindle 212 to "which. fisf keyed I pinion 21 3. The latter 9 meshes with therack 214,011 the upper 'end- Of r d 52" which carries the cam plate- 7:

mounted loosely t-hereon and geared to a pinion 216 to which. vthe; fan blades are secured. Feathered'looselyon the spindle 212 j teeth 21 8 on its inner face which .mesh] with similar teeth on the gear Wheel 215.

yieldingly in engagementwith each other, permit-ting a'backward rotation of the spin dle 212 independently of the gear wheel 2-15 but permitting a positive driving cnnm c f tion when tl'iespindle is rotated-in a for ll'og ,ward direction. The fan; will itlaa'efore 'aetto'retard; the downward" movement of the upward movement;

" The operation; of the now be described p I -4 The main line switch S being closed, the 1 f held closed by the nagnet'8s'o long as the termined limit ain'd'the circuit through the magnet :8',is 'n'ot b'rol ten. 'lhis circuit" may be traced. as.followsf froin"the main conduct-or a. through wire 88, contacts 3. (1. conthente tln'ougtli (50nd at w 2/ it- 1 1, system illustrated a "single p'l buokfutoward' central position the lower end flow through the magnet 8 to hold the switch 130 eration'the switches are closed anda omned Y valve-of the dash-pot permits free escape of .35'and place it under additional tension;

mechanism} includes the centeringlweight transfersupporting bar -211 secured within 53, The spindle 2l2z-carries a gearwheel 215i 4 i is a small driving disk 2 17 havingiratchet A co'il spring 219 holds the ratchet teeth cam platef53, but. willflnot hindera quick "com-r01" system "will :1 1 5 switch P is closed manually and thereafter" potentialon the "line remains'a'bove a prde 126 d actor '89"; contacts. 4. m m-rs, conductor- .1 t fil jllllt'llfill S6, and

en that the 1 iase current in]! i 50 ment with the contacts .106. 107.

4, I seams P closed. When the switch lever 27 is moved to the right, for example as viewed in Fig. 1,

the movable contact 38 bridges the contacts 45,46 and establishes a circuit through the 5. reversing switch magnet 18. This circuit l from the main or through wire 80, contacts 2,. 5, wire 91, contacts 11, 15, wire 92 to the v lower terminal of the motor, throughthe stator winding tothe middle terminal and through wire 1 to the main y. A circuit is 20, also established from the main 2 through wire 88, contacts 3, 6, wire 93, contacts 12,

' 4 16, wires 94, 95 to the upper terminal of the motor, through the stator of the motor to the"middle terminal, and through wire 1 to the main 3 It should be observed that two of the main conductors are connected directly to

the'fix ed contacts

2 and 3 ofthe potential switch P and the other main conductors connected directly to the motor. Therefore when the potential switch P is opened all current from the motor and the controlling apparatus iscut ofi'. It'will be observed ,that the .three terminals of the rotor of. the motor arecon'nected by the

wires

96,97,98 tothe outer terminals, respectively, of the star-connected resistance As the controller lever 27 is inoved farther to-the right the contact plate 53 moves downwardly and permits the successive operation 40 of the switch levers 61, G2, 63 and (H The lever 61 operates first to close a circuit through the magnet winding a as follows, from the main m'through wire 80, contacts 2, '5, wire 91, contacts 11, 15, wire 92 tojunction 99, wire 100, magnet a, wire 101, lever (31, contact 70,

wires

102,95, 94, contactslti, 12, wire 93, contacts-6. 3, wire 88 to main Thc'magnet a being thus energized the con tacts 104, 105 will belmoved in-to engage- This operation short-circuits the middle section a? of the resistance X by connecting the three terminals a, (a, a. as "foll'o\\'s,a is. connected through the wire 108,,contacts 104,

.55. 106 and wire 109 to a, and a", is connected w to' wire 110, contacts 105, 107 and wire 109. The resistance n being thus reduced allows an increase of current through the rotor winding,' and consequently increased speed of the motor. The lever 62 next operates to close a circuit through the magnet bf This.

circuit. is-the same as. that through the coil anti-pm the-main a: up to.-; the wire 100 where rms a parallel circuit to the magnet b, were 111, contact lever GQTCQIl-t-ilCt 71 to "the "position.

I. wire 102, and from thence in common with the circuit through the magnet a to the main '2'.- The magnet 6 being energized closes the switch band this short-circuits the sections 12 of the star-connected resist-#10 ance by connecting the terminals 6 through the

wires

112, 113, 114, respectively, to the contacts of the switch 6. The start? ing resistance is thus further reduced. The

.contact lever 63 next operates and closesa 75 circuit through the magnet c. This circuit is also in parallel: with that of magnet a" Q 1' rom wire 100 to wire 102, as follows,=from wire 100 through magnet 0 wire 115, contact lever 03, contact 70 to wire 102.- The magnet. 0' now closes the switch 0 and shortci'rcuitsthe sections 0 of the resistance by' connecting the terminals '0 c, 0- through the'wires 116,117, 118, respectively, to the switch. 0. This reduces the resistancestill' further, pcrn'iitting further acceleration of. the motor. Lastly the contact lever op erates and closes a circuit through the magnet cl. This circuit is also in parallel with the circuits of magnets 11, b, c from wire 100 through magnet d. wire 120, contact lever 64:, contact 71 to wire 102. The magnet (Z' closes the switch d and thus connects the terminals (Z (Z (Z with the switch (lthrough the

wires

121, 122, 123, respectively: This :tull speed.

As before explained, when the succeed ing switch lever is operated to closed post-- tion the preceding one is operated to open position such that when the cam plate 53 reaches the limit 'of its movement only the switch lever 64s is held in "circuit closing This operation efi'e'cts thesuces 05 sive deenergi'zationof the magnets'a, b, a, V and therefore only one magnet, viz. (1', consumescurrentwhile the motor is in opera tion and the switch (Zmaintains all of the starting resistance X short-circuited. \Vhen 110.

'the controllerlever is moved back to central position the switch levers G1, 62, 63, 64,

are operated in the'reverseorder, the magnet I a, being first energized, their the magnet d.- detnergized, the magnet b energized, themagnet c deenergized, the magnet a energized, the magnet b de'nergized, and finally the magnet a deenergized. By:-this opera tion the resistance Xis gradually in'traduced back into the rotor circuit, after which the v contacts 38 and 46 are separatthtpfbrealt Y 'the circuit through the reversing switch magnet 18.and thereby cut off the su pl current to the motor' which-will. then. be

stopped by the application of brake apparatus in-any well knownmanner, =W'hen the controller lever" is movedto the left the contact plate 38 bridges the contacts 43, 44, and closes "a circuit through the magnets 17 "of the reversing switch; This circuifiis' as been slowed down sufficiently.

78 are in such position that when the handle followsrfrbm P w through wire 8 (l;

contacts

2, 5,- wi 1 magnet, wi re limit switchltl, wire 126,

contacts

43, 38, 44,

1, the rotati'o If the flatter.v Thswitclr oper 1'0 ated byfthem'a'gnet; 17 connectsthe wires 91 while the switch operatedby the magnet-18 connects thewires 9 1, 93 to the'wires 92 and 95, respectively. The direction of the cur I --arran'g'ements ofparts awithont departing 15. ,i-ent through the stator windings is there? )ent. of the controller lever;

scriptio'n' that theniotoiymaybe started in" e1tl ie r d rection, depending'upon the direc-;

I tion in which, tlte controller lever moved,

and (that the acceleration "niay"be" made as" ,slow asv desired, depending upon the speed i with which t": e controllerley'er'ismoved to release the cam plate 53 'and"allow th'e same" step by step euttiiig;.o'11tof'tlie starting re- But such acceleration cannot ex-,

sistance.

. ceed.a}pre determ1ned limit on'jaccoiint of the" retarded movementof the camfplate 53; which is outof thecontrol of tlie'operator. during normal operation The movement ofthe cam plate '53 in the reverse direction;

however, to insert the resistance may be made as quickly as desired, or the cam plate ofiers an obstruction to the movement of the handle 32'to-central position or past central position and prevents the controller lever frombeing thrownover quickly and reversing the motor circuits before'the motor has The recesses 32 seats itself therein the cam plate 53 holds all the switch levers 61, 62, 63 and 64 in theiropen circuiting positions and the con- .55 tact plate 38 is out of engagement with either of the contacts 43 or 46. In order to start the motor in the same direction as before, the handle may be simply returned to its outermost position. If the motor is to be reversed, however, the handle 32 must be pulled out againstthe spring 77 so that: the obstruction formed by the flange 73 may be avoided.

Although "I have shown the inotor and 65 controlling system applicable particularly;

ore reversed l by; the: reversal jot-{the 'm'oveinvention may havej'a general application.

For instance, the automatically :retarded manualcontroller is alsogfidapted to control other formszofzstarting-resistance, andiother 'arr'a-ngeme'nts. of circuits and connections.

to elevators, it should be understood thatt the wing of a 'series'fof circuitsaother thamthose used in connection with" the li starting resistviousl'y; "those skilled r in the-art; mayj make v tion of the'switch mechanismand in the from "the spirit :and.- scope of, my-linWntion,

and I 'desireitherefom not to begllim ited to, the precise -cOnstructiOn and -.-arrangement disclosed;

'1 4 ';?1 1 1 H: Having thus fully described my -invention,

what-I claim-and'des'ire to have-protected by-Let-ters Patent of the, U;nited States is a motor control systennathe; combination with a motor, .a sectionalstarting resistance, and accelerating; relays,- of a man- "ually'operable -s wi tchy lever carrying a switch ;c0ntact',* stationary conta ctscooperate in'g therewitl a plurality of. fixed ad, 1n

"'inagnets meansl-for operating. said. movable "cont-acts .uccesfsi vely' upon 'tlie.='.o"peration of the switch lever, and a mechanicah idevice for automatically"retarding the operation of said means.- a

2. In a motor control system, the combination with a motor, a reversing switch, a' sectional starting resistance, and accelerating relays, of a master'switch comprising a lever movable from a. central position in either direction, and controlling the circuits of the reversing switch magnet-s, meansoperable upon the movement of said lever in either direction to successively operate the relay magnets, a mechanical device operable to automatically limit the speed with which said means operates when the lever is moved from a. central position, and

- var'ious' changes :in the-details. 10fconst-r-ucpermitting a quick movemehtof said means in the reverse direction.

3. In a controller, the combination with a switch lever,-a contact carried thereby and a stationary contact inthe path'of movement 'of the lever contact, of a pluralityof circuit controlling members, and automatically retarded means. mechanically connected to' the switch lever for. successively operating said memberswhen the lever has been moved R, 4. In-a controller-,the combination with a switch lever, a. contactearried thereby, and a cooperating stationary Contact, of a plurality of-stationary circuit controlling momhers, a device,. -for successively operating said members, connectlon's bet-ween the lever and said device permitting the device to operate when the lever is moved, and means manual actuating-device, ofclectric switch for automatically limiting the speed of operation of said devices.

5. In a controller,the combinationwith a switch lever movable in opposite directions from a vertical central position, of a depending rod pivoted to the lever above the lever pivot, a switch-operating device, and

connections between 'said device and said rod for. holding the dev ce inoperative wlnle the switch lever is in central position.

6. In a controller, the combination with a mechanism, a lostmotion connection between said actuat ng device and said switch mechanism, apparatusfor automatically returning said actuating device from actuated tering mechanism to automatically return said lever tolor near initial or central' position, an additional. switch, a cam actuated.

by gravity to automatically operate said additional switch, a connection comprising a pin-andslotbetween said lever and said cam to effect a release of the. latter when the lever is moved from its initial position a predetermined distance and to positively lift said cam when the lever is.ret'nrned, and

aretarding device out of the control of the operator-to prevent the cam from descending beyond a predetermined rate of speed. 8.";[11 a controller, the combination with a switch lever, ofa contact carried thereby,

stationary contacts in position to be engaged by .the first-named contact, an additional switch located below said lever, adcvice for operating said additional switch, means for normally liolding'said'switch lever in a vertical position and automatically returning it to such position when released after op-" .cration, a rod connected to said lever above its pivot, a lost-motion connection between said rod and said device permitting theoperation of'said device independently of the lever when the latter is moved from its central position, and retarding mechanism located above said device and operatively connected thereto.

' In testimony whereof, I'have signed my name to this specification in the presence of. two subscribing witnesses.

v .AUGUST SUNDH. Witnesses:

CHAS. M. NISSEN,

DA'VID LARSON.