US2072282A - Lift and like controlling mechanism - Google Patents

Description

March 2, 1937. N. c. SMART El AL LIFT AND LIKE CONTROLLING MECHANISM Filed Oct. 9, 1934 Patented Mar. 2, 1937 UNITED STATES PATENT OFFICE LIFT AND LIKE CONTROLLING MECHANISM Application October 9, 1934, Serial No. 747,540 In Great Britain October 5, 1933 9 Claims.

This invention relates to lift or like controlling systems, and has for its object the cheapening of such systems whilst at the same time improving in certain points on their reliability.

In connection with certain automatic or semiautomatic lift controlling systems, it is necessary that the control mechanism shall possess some indication of the position of the lift at any instant. This indication may be employed to de- 10 termine, for example, the direction in which a lift is to travel when a calling or starting button is pressed, or to give a visual indication of the lifts position, or for like purposes. In this connection it is known to provide facsimile or re- .5 duction gearing operated directly or indirectly from the winding drum of a lift, which gearing drives a multi-contact switch affording the required indications. This method, though fairly certain in action, is costly and requires skilled 20 maintenance.

An alternative known method of affording indication of a lift's position is to cause the said lift to supply current impulses at particular points in its travel to a group of relays the oper- 25 ated ones of which receive current continuously,

the said relays operating and remaining energized in sequence as the lift passes the said points. The objections to this method are that a current of greater or less dimensions is con- 30 tinuously employed in maintaining some or all of the relays energized, and that should this current supply fail, then even if the lift does not move, restoration of the current does not reenergize the relays necessary to afford indica- 35' tion of the lifts position.

A single step-by-step switch has also been employed to afford an indication of the position of a lift, the said switch receiving up or down impulses of momentary character only as the lift 40 is in motion, and maintaining itself in the position to which it was last impulsed without the use of a steady current, being impulsed forwards r backwards in accordance with the direction of travel of the lift.

45 According to the present invention, two singlemotion step-by-step switches are employed, all up impulses being fed to one switch and all down impulses to the other. The switch which at any time is not being impulsed to follow the 50 motion of the lift carriage, is later automatically impulsed to take up an equivalent position to that occupied by the other. When this condition is satisfied, both switches remain at rest until one or the other is again impulsed, when the 55 cycle -of operations is repeated. Indication of CJI the lifts position is obtained from a bank of the switch which is being, or was last, impulsed.

In order that the invention may be clearly understood, one embodiment thereof will now be described with reference to the accompanying drawing which shows, by way of example, the circuit of a system for controlling an electrically operated lift serving six floors.

Referring to the drawing, it will be seen that the lift L is suspended by a cable LC passing over a drum LD and having a counter-weight CW thereon, the drum being driven by the motor DM. The motor driven shaft is provided with a brake drum with which there cooperates a brake shoe BB normally effective but arranged to be released by a brake magnet BR. At each floor, there is located a gate switch JA to JF connected in series by leads 2G and with a positive source of potential at 3G at one end, the switches being in series and connected by lead 3J with a gate relay J connected to the negative. Thus it will be seen that when all the gate switches are closed, the gate relay J is operated and the contact thereof 9'1 will be closed so as to deliver positive potential to the lead 4, for the purpose later described.

At each floor, there is a push button PA to PF provided with contacts arranged to cross connect two main leads 5 and 6, the lead 5 leading back to a connection with a short lead 1 having open contact sit: at one end and closed contact sdi at the other end, the latter contact being normally closed on a short lead 8 connected with closed contact e: from which positive potential at 9 is derived. It will be seen that when one of the push buttons PA to PF is closed positive potential from lead 5 will be delivered through lead 6 to closed contact Shl and lead Ill to a selfoperating contact '0 of a wiper switch stepping magnet C, thence through the lead II and the 40 magnet to negative. The wiper switch stepping magnet C upon being operated steps the wipers of two wiper switches Cl and C2.

The push buttons PA to PF also have contacts closing when a push button is operated to deliver the positive potential from lead 5 through one of the lamps LA to LF, these lamp circuits being connected to individual le'ads I2A to I2F, which as will be seen are connected to the wiper contacts of wiper switch Cl.

It will be noted that from near the lamps LA to LF, ticks ta to tf are shown, which simply indicate that there may be corresponding lamp circuits in the lift L and similarly ticks" th: and thl, shown at the lower ends of the leads 5 and 6, are adapted to connect with corresponding push buttons arranged in the lift car.

It will be seen that the wiper of wiper switch Cl is connected by lead 13 with a call confirming relay SH, which as shown, is connected directly with the negative. Accordingly when call confirming relay SH is operated, its contact shz connects .a lead M with lead I and thence through contact Sdl lead 8 and contact 62 to the positive at 9 to thereby provide a holding circuit for the relay SI-I. Call confirming relay SH also operates contact sin to cut the current from lead 5 to lead 58 and stop the stepping of magnet C, and contact 8713 for the purpose hereinafter described.

Two equalizer switches US, with wiper switches USI, USE and DS, with wiper switches DSl, DSZ are provided, each being adapted to be stepped by the respective stepping magnets US and DS operating self-stepping contacts us and ds as hereinafter explained. It will be seen that the stepping magnet US is connected by lead I5 with the left hand contact at as and the stepping contact us, through lead Hi is connected with the right hand contact at cm and similarly stepping magnet DS is connected through lead I! with the right hand contact at as and its stepping contact (is, through lead IS with the left hand contact at 12. The contacts at as and as are adapted to cooperate with contactors A2 and A3, the contactor A2 being connected by lead l9 through contact 31 to positive potential at 2B; and contactor A3 is connected through lead 2! with a contact n which when closed connects to positive at 22. The contact 1'1 is adapted to be closed by an impulse relay R, arranged to be operated by inductor plates AB, BC, to EF located between floors in the lift shaft so that as the lift travels from floor to floor, a current impulse will be sent to stepping magnet US or DS, as later described.

The contactors A2 and A3, together with a contactor Al, are mechanically connected with the two-position armature of a direction relay A having two magnet coils, one of which is connected by lead 23 with a contact an which closed connects to positive at 24; and the other coil through lead 25 and contact dri, closed, to positive at 26. The two position direction relay A is substantially of the type shown in British specification No. 354,847.

It will be noted that the contacts of wiper switches USI and DSl are connected together by leads 21a to 21 and the wiper of wiper switch DS! is connected to the positive at 28, while the wiper of wiper switch USl is connected by lead 29 with an equalizer relay S, which is operated by being connected to the negative. Also note that a lead 30 connected from positive at contact ea to lead 29 is arranged to supply current for operating the equalizer relay S under certain conditions.

It will be seen further that the wiper contacts of wiper switches U32, DS2 and C2 are connected in parallel by means of interconnecting leads 30a to 391 and with spaced points on a potentiometer P, the latter being connected at one end with the positive potential at 3| and with the negative at 32. The wipers of wiper switches US2 and DSZ, it will be seen, are connected by the respective leads 33 and 34 with the two contacts at (11, which are associated with the contactor Al connected as indicated later and previously referred to as operated by the direction relay A.

The wiper of wiper switch 02, previously referred to, is connected by lead 35, 35a through contact 8713, closed, or (24, closed, and 36, 36a with one coil of a two-coil polarized direction controlling relay B, the two coils of which are connected in series through lead 31 and the second coil being connected by lead 38 with the contactor Ai, previously described as operated by direction relay A. It will be seen that the armature contact arm 39 of the polarized relay B which is normally central is connected with the positive potential at 49 and the arm cooperates with two contacts at In. One of contacts in is connected by lead il with up-call relay UR, the cir cuit of which is continued through lead 42, contact d1"; and lead 43 to brake relay E, which is connected to the negative. The other contact at In is connected by lead 44 with the down-call relay DR, which is connected through lead 45, contact are and the same lead 3 with brake relay E.

An inductor floor relay Q located in the lift car is arranged to be operated by inductor plates QA to QF located in the shaft at each floor. 1

Floor relay Q, is arranged when operated to open contact (11 which supplies positive from 46 through lead 4? to contact Sdz, shown open, but which when closed on an associated contact is arranged to deliver current through lead 48 to operate brake magnet BR, which is connected with the negative. It will be noted that the brake magnet BR may also be operated through lead ii] from contact 61 when closed on the positive from 5%, the latter being normally connected by the associated contact at e1 through lead 5| with brake magnet operated contact bri, which by connection through lead 52 with the upper coil of the isolating relay SD carries positive potential to operate the latter, which is connected to negative. The isolating relay SD is provided with another coil which is connected by lead 53 and through a self-operated contact Sds with a timing circuit TD leading to a timing device BM through the heating coil I-IC, supplying positive potential from D53.

The up-call relay NR, in addition to operating contacts 1m and ms, operates contacts urn to close the positive circuit from lead 4 and contact 7'1 on lead 54 connected to up drive contactor U, which is provided with a holding circuit contact in connected by lead 55 with the positive at brake magnet operated contact Inc; and similarly, down-call relay DR, besides operating contacts dn and dra, operates drz which connects the positive from contact 71 and lead 4, by lead 55 with down drive contactor D having a holding circuit contact 021 connected by lead 51 through brake magnet operated contact b1'2 with positive potential.

The two single-motion follower equalizer switches US and DS, preferably of the type disclosed, for example, in British specification No. 349,180, rotating always in the directions of the arrows, are arranged to follow the motion of the lift carriage L in the shaft, the up equalizer switch US following the upward motion and the down equalizer switch DS following the downward motion of the carriage. The call registering switch C which is provided for storing calls made for the lift carriage also, rotates only in the direction of the arrow on the drawing.

A group of call buttons and associated indicator lamps mounted in the lift carriage is connected to the floor button circuit through leads indicated by the dotted line. The function of each of the buttons and lamps of this group is identical with that of the individual floor buttons and lamps and these are not shown in detail in the drawing.

The system is adapted so that the lift carriage travels to the floor corresponding to the call-button depressed. Thus, if the carriage is at the first floor and a user on the fourth floor wishes to travel to the second floor, he first depresses the call-button PD mounted at that floor. The carriage then travels to the fourth floor and the user enters; finally by depresing the second floor call-button in the carriage, the user is taken to the second fioor.

The two-position direction relay A takes up one of its two positions according as the lift carriage is required to travel upwards or downwards. In the drawing, the relay is shown in the position required for upward travel of the carriage.

The three-position direction controlling relay B which, as previously indicated, is provided for controlling the direction of motion of the carriage is normally in the central position shown, but if the carriage is required to travel upwards it is operated to the right, in the drawing, and if the carriage is required to travel downwards it is operated to the left. The position of the contactor 39 of the direction controlling relay B is dependent on the position of the equalizer switches US and DS since it is connected with wipers U82 and DS2 of the latter through leads 33 and 34 and its operation will be more fully understood from the description of the operation of the system in answering a typical call.

It will be understood that the system is rendered inoperative by release of the gate relay J, the latter being released when one of the gateoperated switches JA--JF is opened at one of the floors. The gate relay J is always operated when all the gate-operated switches are closed. thereby indicating that all the gates are shut and permitting the system to be sarted.

The inductor-type floor relay Q is mounted, together with an intermediate inductor-type impulse relay R, on the lift carriage and these relays are adapted to be operated by indicator plates QAQB and AB-EF, which are mounted in the lift shaft.

The floor-operated relay Q is always in operated position whenever the lift carriage is stationary at any of the fioors,

The intermediate impulse relay R is operated whenever the lift carriage moves between two consecutive floors, the indicator plates AB-EF therefor being arranged midway between the floors, these plates being different from those arranged at each of the floors for operating relay Q.

It will be noted that the call confirming relay SH by operating contactor Shl is arranged to arrest the stepping of call-registering relay C when it steps to the contact corresponding'to the floor to which the lift carriage is to travel and when this occurs, the lamp of the group LA-LF corresponding to that floor is operated through its line l2A-l2F to confirm to the user that his call has been registered.

In the position of the lift carriage shown in the drawing, the lift being at its lower limit of travel, i. e. at floor I, the gate relay J (all gates closed), the equalizer relay S. (DSl-USI and line 29) and the floor relay Q (inductor plate QA) are all operated; the contacts of these three relays are shown, however, on the drawing in an unoperated position to agree with-current practice.

Assume now that the fourth floor call-button PD is depressed, either in the lift car or at floor 4, indicating that the lift is required to travel to floor 4. Depression of this button completes a circuit from positive at e2, via lead 8 contact Sdl, lead 5, the said call-button PD contacts, lead 6 back to contact Shi and then through lead It) contact c, and lead H to the stepping magnet C of the call-registering switch Cl. This switch then steps by self-interruption at its contact in a manner known in the telephone art until the wiper of switch Cl reaches the contact in the bank (fourth) which is connected by lead I 2D, with the contact of call-button PD, through lamp LD, thereby operating the call-confirming relay SH by current via negative through relay SH and lead 13 to the said bank contact (fourth) and by lead IZD to the indicator lamp ID in series with contacts of call-button PD and thence through leads 5, I, contact Sdl, and lead 8 to positive at the closed contactor cz, and indicator lamp LD lights, indicating to the caller that the call has bee-n registered and that the button can be released. Upon operation of callconfirming relay SH the contacts operated thereby operate as follows:

Shl interrupts the stepping of call registering switch C.

Shz locks relay SH operated to positive via lead l4 contact shz, leads I and 8 and contacts Sdl and 62 so that if the call-button PD is released before the brake relay E operates, as described later, call registering switch C is not stepped further by contact Shl.

shz closes the circuit from the wiper of switch C2 between leads 35 and 36 to direction controlling relay B It will be noted that when the stepping magnet C moves its wiper C2 out of agreement with the wipers of equalizer switches USE and D52, certain sections of the potentiometer P are short-- circuited and the direction controlling relay B operates when contact 3113 closes. In the example given the current then passes from the plus at 3| of the potentiometer P through lead 30a to the first contact of U82, then through lead 33 to the left contact (11, then by contactor Al and lead 38 to the direction controlling relay B and through leads 31, 36, contact sha, lead 35 to the wiper and fourth contact of C2, lead 38d to the potentiometer P and negative at 32. The con tact arm 39 is then operated in a direction (to the right contact In in the drawing) to operate up call relay UR and brake relay E, the circuit being completed from the plus at 49 through the contact arm 39 of direction controlling relay B through lead 4| from contact In through UR, lead 42, contact dTs, lead 43 and to minus beyond brake relay E.

With the operation of up-call relay UR and brake relay E, the following contacts are operated by these relays:

61 by closing opens the contact on lead and operates the brake magnet BR from the positive at 50 via lead 49, contact Sdz, (contact sdz being open), and lead 48, thereby removing the brake BB from its drum. It will be noted that closing e1 at the same time opens a circuit from the positive 50 through lead 5|, contact bTl and lead 52 to isolating relay SD which, through opening of its contact Sdl, isolates the call button circuits through leads 1 and 5 from the positive at 9. It will be noted that contacts bTl, DH and bra are operated by the brake magnet BR.

e2 opening deenergizes call confirming relay SH thereby closing contact sin, but 62 opens the push button circuit leads 8, I, 5 etc. and prevents further calls from being made until the lift reaches its destination, the operating positive potential at 9 being removed from the buttons PAPF.

e3 closed on lead as, connected to lead 29, holds equalizer relay S operated to the positive while equaliser wiper switches USI and DSI are stepping.

64 by closing leads 35a and 36a maintains the circuit through the wiper of switch C2 to direction controlling relay B when contact 5713 is opened by deenergization of call confirming relay SH, by the opening of (22 as previously explained.

2/.1'1 closed energizes one coil (left as shown) of direction relay A from positive 2 through lead 23 but does not move the armature as the relay A already its armature in the direction in which it is now attracted.

u'rz closed on lead t and through lead 5 energizes the up drive contactor U from positive on closed contact 9'1 causing the lift to move upwards under the influence of the driving motor DM.

1673 opens between leads 43 and 35 and, being an interlocking contact, by opening prevents accidental operation of down call relay DR through lead l l from contact in. Upon energizing the up drive contactor U, its contact Mr loclts this this contactor operated to contact 177's, now closed as previously explained.

The lift now traverses the shaft towards the required floor (fourth) releasing floor relay Q and closing its contact (11 on lead ll, but since contact SCZz is open there is no cu rent from positive at 3-5, the brake magnet BR being energized from (21 by the positive at 5t? through lead it. Midway between each floor the lift passes an indicator plate AB, BC, CD, in the shaft which momentarily operates the impulse relay R. Upon operation of the impulse relay R its contact in closed. Contact T1 by closing operates the switch magnet US once for every plate passed, the current passing from the positive 22 at 11, via lead 2i, contactor A3, left contact as (the direction relay A standing as shown) lead l5 through the relay to negative so that when the indicator plate Cl) between floors 3 and Q is passed, the wipers of the call registering switch C and up equalizer switch US, USl, USZ, will occupy like positions (fourth contact, corresponding to call button PD) on their respective banks, with the result that the wipers of wiper switch C2 and wiper switch USZ will be connected through lead Bild to the same point on potentiometer P and the direction controlling relay B is short-circuited, thereby permitting its armature to return to the central position; thus opening the circuit at in on lead ll and releasing up call relay UR and brake relay E. Note that in stepping the wiper of equalizer switch US! forward into register with the wiper of call register switch C! it steps out of register with the wiper of equalizer switch D-Sl in so doing removes the latters energizing current from positive 28 through leads 21a and 29 from equalizer relay S, but the latter is held through lead 38 from positive at contact 63.

While direction controlling relay B is deenergized, up call relay UR and brake relay E are deenergized with the following results;

e1 by opening connects the positive at iii! to lead El and permits the current to operate isolating relay SD via contact bTl, the latter still being closed by the brake magnet BR. In the same opening movement of contact c1 the latter opens its circuit through leads 49, 42- to the brake magnet BR but isolating relay SD being operated at the same time its contact sdz closes on lead 48 and holds the brake magnet BR operated from positive 45 on contact (11 through lead ll.

e2 closes to positive at 9 but since contact sdi is opened at the same time, with operation of isolation relay SD, so that push button calls can have no eifect.

63 now opens the positive to lead 3i! and releases equalizer relay S with the result described below.

64 opens, but since the circuit 35, 35c, through direction controlling relay B has been neutralized (wipers C2 and USE in register) nothing happens.

sds locks the isolating relay SD operated to a positive potential D53 derived from the circuit TD of a time relay, comprising a heating coil HC and a bimetallic strip BM and operating in known manner, and this circuit supplies the said potential for a predetermined period after closure of contact Sds.

Equalizer relay S being deenergized as described, contact 81 closes on the positive at 20 and completes a circuit through lead is, con tactor A2, left contact or, lead It, contact ds and to negative through DS which causes equalizer switch magnet DS to step the wiper of wiper switch Bill by self-interruption at contact ds in the direction shown by the arrow until the wiper of switches USi and D51 are in register and cocup-y like positions on their banks, that fourth contact and positive at 28 can then pass from wiper of DB1 through lead lid to wiper of USi and lead which reoperates equalizer relay S and its contact s1 by opening stops the stepping of equalizer switch DS.

The lift now runs to the floor level required. When nearly or substantially at the required position at the fourth floor, in example given, inductor ilooi elay Q is operated by the levelling inductor plate QT.) in the lift shaft, and by the opening of its contact qr deenergizes the brake magnet BR through leads 4? and 8 and contact sciz, (61 being already open) allowing the brake BB to close and stop the lift. Upon deenergizing b e magnet BR, its contacts Z211, 1372 and hrs n, the opening of contact ZJTs cuts the circuit through lead 55, contact in, of the up drive contactor U to stop the motor. After a short interval determined by the timing circuit TD, to allow the gate to be opened, isolating relay SD is released from the positive at D53 by the delay circuits l-IC and EM, and contacts Sdl, sdz and sds are released. Releasing contact sdi closes leads l and on lead 8- and the positive 9 at c2, and the latter closed, allows further calls to be stored by operation of one of the buttons PAPF. In normal idle position as previously indicated, equalizer relay S, gate relay J and floor relay Q remain operated.

Assuming now, as a further example, that the lift is at the fourth floor, as just described and the top floor call button PE is depressed, the call registering switch C will be again operated in the manner previously described to step the wiper of wiper switch C! from the fourth position to the last contact position, where again the circuit from positive 9 at 62, through lead 5, button contacts PF, lead 52F, wiper and lead ii to the isolating relay SH will be completed, since the wiper of stepping switch C2 is now connected by lead with the potentiometer P at the point nearest its negative end, the current will flow from the positive at 3! through lead and the fourth contact of wiper switch U2 through lead 33, left contact or, contactor Al, lead 38 and the direction controlling relay B, leads 36, contact sha, lead 35 wiper of C2 on last contact and lead 30f to negative 32 in the same manner and in the same direction as before and the up call relay UR will be operated. It will thus be seen that the operation previously described will be repeated and the lift will go to the top floor.

Again assuming that the lift is at the fourth floor, as in the first example, and it is desired to go down to the second floor, the call button PB now is depressed and held down and again call registering switch C is operated, this time stepping the wiper of switch Cl from the fourth contact to the second contact (in the direction of the arrow), thereby completing the indicator lamp circuit through the call confirming relay SH, in the manner previously described, and stopping the call registering switch C with its wiper Cl on the second contact. The lift being at the fourth floor, it will be recalled that the wiper switches U82 and DS2 are in register and both standing on the fourth contact while now the wiper of wiper switch G2 has advanced to the second contact. In this position, the positive current from the potentiometer P now passes in the opposite direction, that is, through lead 30b and the second contact of C2 and through lead 35, contact Sh3, lead 36, the direction controlling relay B, through lead 38, contactor Al and left contact (11 and the lead 33 to wiper switch USE, then through the fourth contact of this wiper switch back through lead 30d to the negative end 32 of the potentiometer P, thereby operating the direction controlling relay B armature contactor 39 in the opposite direction to close the plus circuit from 40 through left contact In, lead 44 to down call relay DR, lead 45, contact um, lead 43 and brake relay E. From here on the operation will be substantially as previously described except that now contacts dri, dTz and d1: are operated. Closing contact (in operates the right hand magnet of the direction relay A to change the position of the contactors Al, A2 and A3 on contacts a l, m and as, so that the down equalizer switch magnet DS is operated by operation of impulse relay R as the lift carriage passes the indicator plates CD, BC in the lift shaft and afterward the up equalizer switch US is automatically stepped in the manner previously described to bring the wiper of switch US! into register with the wiper of switch DS I.

It will thus be seen that in the operation of the down call relay DR the contacts dTl, (2T2 and dn operate to perform functions corresponding to those previously described for contacts 'lLTl, um and um, but now for the downward operation of the lift, the down drive contactor D being new operated instead of the up drive contactor U and held by contact d1, through lead 51 and brake magnet operated contact M2. The operation of the other relays and contacts of brake relay E and isolating relay SD will be substantially the same as described previously.

Although we have described certain embodiments of our invention we wish it to be understood that these embodiments do not by any means exhaust the possibilities, and that subject to the scope of the appended claims we wish to claim all such embodiments or variations thereof as would be obvious to those skilled in the art.

We claim:-

1. In a lift for serving a plurality of floors, a push button and indicating lamp with cooperating circuits, for each floor, a stepping call registering wiper switch having contacts corresponding to the floors served, a stepping magnet automatically operated for stepping said wiper switch, the circuit of said magnet being completed by operation of a floor push button, circuit connections from the contacts of said wiper switch arranged to form part of the respective lamp circuits, said circuits being completed by the operated floor push button and a relay in said wiper switch lamp circuit arranged to be operated simultaneously with lighting of the lamp when the stepping wiper switch reaches the contact corresponding to the floor of the operated push button, said relay operating to stop tlze stepping of said wiper switch.

2. In a lift for serving a plurality of floors, as in claim 1, a second wiper switch operated synchronously with the first and by the same stepping magnet, a direction controlling relay, the contacts of said second wiper switch being connected with a potentiometer for controlling current to said direction controlling relay, and call relays arranged to be operated by said direction controlling relay for controlling the up and down movement of the lift.

3. In a lift for serving a plurality of floors, as in claim 1, a pair of stepping equalizer wiper switches, each having wiper contacts corresponding to the floors served, leads connecting corresponding wiper contacts together, stepping magnets for the respective equalizer switches, means including a direction relay for determining operation of the equalizer switches according to whether up or down movement of the lift is required, impulse operated contact means and circuits for operating the stepping magnets of the respective equalizer wiper switches for up or clown movement arranged to be operated as the lift passes from floor to floor, means arranged to become effective when one of said equalizer switches comes into register with the push button operated switch for stopping the lift at the floor corresponding to the button operated and means for automatically stepping the other equalizer switch into register with said impulse operated equalizer switch.

4. In a lift for serving a plurality of floors, a push button for each floor, a stepping wiper switch having contacts corresponding to the floors served, a self stepping magnet for stepping said wiper switch, a circuit common to all floor push buttons for operating said stepping magnet when one of the push buttons is depressed, a relay, the circuit of which is arranged to be completed by said wiper switch when its wiper reaches the contact corresponding to the push button depressed, the operation of said relay in terrupting said push button stepping circuit, an auxiliary wiper switch stepping in unison with the first wiper switch and means controlled by said auxiliary wiper switch for determining the direction of movement of the lift.

5. A lift for serving a plurality of floors as in claim 4, wherein the means controlled by said auxiliary wiper switch comprises a direction controlling relay, the operating circuit of which is controlled by the position of the lift carriage in cooperation with the auxiliary wiper switch, for determining the direction of travel of the lift carriage according to the push button depressed.

6. A lift for serving a plurality of floors as in claim 4, wherein a direction relay controls circuits cooperating with said auxiliary wiper switch which are arranged to control the operation of a direction determining relay according to the position of the lift carriage and the floor button operated when registering a call for the lift carriage.

7. In a lift for serving a plurality of floors, a push button for each floor, a stepping wiper switch having contacts corresponding to the floors, a self stepping magnet for stepping said wiper switch, a circuit common to all the push buttons for operating said stepping magnet when one of the push buttons is depressed, a relay, circuits arranged to be completed by said wiper switch for operating said relay to interrupt said push button stepping circuit when the wiper switch reaches the contact corresponding to the push button depressed, an auxiliary wiper switch stepping in unison with the first wiper switch, a direction controlling relay controlling up and down movement of the lift and circuits controlled by said auxiliary wiper switch for operating said direction controlling relay.

8. In a lift for serving a plurality of floors, up and down equalizer wiper switches and a call registering wiper switch having contacts corresponding in number with the floors to be served, circuits interconnecting the corresponding contacts of all of said wiper switches with spaced tappings of a potentiometer provided at opposite ends with plus and minus potential, a stepping magnet for said call registering wiper switch having a circuit arranged to be closed by a floor push button for self stepping said call registering wiper switch, means for stopping stepping advance of said call registering Wiper switch when it reaches a point corresponding to the floor button operated, a relay arranged to be operated by potential from said potentiometer for controlling the direction of travel of the lift, stepping magnets for stepping the respective equalizer wiper switches, impulse means operated by the lift in passing from floor to floor for stepping one of said equalizer wiper switches into register with the call registering wiper switch, the equalizer switch so operated depending on the direction the lift is required to travel as determined by the call registering wiper switch in cooperation with said direction controlling relay.

9. In a lift for serving a plurality of floors, a potentiometer having a corresponding plurality of tappings, a call stepping wiper switch, the contacts of which are connected to said tappings, push buttons for the respective floors, a circuit including a stepping magnet for stepping said call wiper switch when a floor button is depressed, means for stopping the stepping of said call operated switch on a contact corresponding to the floor button depressed, a. three-position relay arranged to be operated by current from the potentiometer accordingly as said call wiper switch is positioned for determining up or down movement of the lift, a twoavay relay arranged to be operated in one direction when up movement is determined and the other direction with down movement, a pair of stepping equalizer wiper switches, the stepping of which is controlled by the position of said two-way relay, the contacts of said equalizer switches being connected the same as the call wiper switch to corresponding tappings of said potentiometer, means operated by the lift in passing from floor to floor for stepping one of said equalizer switches until its wiper engages a contact corresponding to the floor selected by the push button depressed, said three position relay being deenergized to stop movement of the lift when the Wipers of the call and equalizer switches are on corresponding contacts, and means for automatically stepping the other equalizer switch into register with the lift operated equalizer switch.

N. C. SMART. B. F. MOSS.

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