US2493293A - Vertical lift control system - Google Patents

Description

1950 LE ROY H. KIESLING VERTICAL LIFT CONTROL SYSTEM 5 She ets-Sheet 1 Filed Dec. 31, 1947 DOW/V INVENTOR. LEROY H. K/ESL/NG lax p 7 %& ATTORNEY Jan. 3, 1950 LE ROY H. KIESLING VERTICAL LIFT CONTROL SYSTEM 5 Sheets-Sheet 2 Filed Dec. 31, 1947 FIG. 2.

I 3 INVENTOR.

LEROY H. K/ESL/NG fZ/yfi;

M5? ATTORNEY Jan. 3, 1950 LE ROY H. KIESLING VERTICAL LIFT CONTROL SYSTEM 5Sheets-Sheet 3 Filed Dec. 31, 1947 M.MW 2mm E E i Y. W 0 L w )8 4 a w w a a a t z a H H H k M F W W W W I v A rrpRNE Y J 1950 LE ROY H. KIESLING VERTICAL LIFT CONTROL SYSTEM Filed Dec. 51', 1947 5 Sheets-Sheet 4 FIG. 5.

.6 4% N5 5 W 1 N m m m W v: .A a PM Jan. 3, 1950 LE- ROY H. KIESLING VERTICAL LIFT CONTROL SYSTEM Filed Dec. 31, 1947 5 Sheets-Sheet 5 T O MOTOR TO MOTOR DOWN CONTROL UP CONT/POL O/HOU/T Cl Gil/7' 234 t j- 224 L3 230 220; fi Z3 6 225 238 F; 22a 54 L I is 2&5

U IN V EN TOR. 7/ LEROY H. K/ESL/NG Em p 4% ATTORNEY Patented Jan. 3, 1950 UNITED STATES PATENT OFFICE 17 Claims.

The present invention relates to control circuits and apparatus for conveying systems particularly of the type usually referred to as dumbwaiters, and is particularly concerned with improved automatic control features therefor.

Heretofore, dumbwaiter control systems have included push-button switches and motor relay arrangements with holding circuits or devices, organized in such a way that an operator at one of the dumbwaiter control stations could institute movement of the dumbwaiter car from one station to another by momentarily pressing a control button. The dumbwaiter would respond only if, at the time of the momentary depression, the dumbwaiter car or conveyor was at rest at a station and the door interlock switches all were closed. The motor relay holding circuit would be actuated under these conditions, initiating movement of the dumbwaiter car according to the operators signal, and the holding circuit would retain the motor in operation until the dumbwaiter car arrived at the station to which it was directed.

Upon arrival of the dumbwaiter car at the destination, a limit switch would be engaged for causing the release of the holding circuit, and the operation of the dumbwaiter drive motor would accordingly be arrested. The dumbwaiter door at that station could then be opened by an operator, and the car could then be unloaded and/or loaded and the door reclosed.

In these former systems, a depression of a control button at a time when a door interlock switch was open, or at a time when the dumbwaiter car was in motion between stations, was entirely without effect. Hence, if an operator at one station depressed a control button to order the dumbwaiter car to that station, but one of the dumbwaiter doors was open at the time of depression of the control button, then the actuation of the control button was entirely ineffective. Persistent depressions of the control button would then be resorted to by the operator, in the hope that the dumbwaiter door eventually would be closed and a subsequent control button depression could institute its operation. Such dumbwaiter control arrangements suffered by lack of a memory feature, all push button depressions prior to readying of the system for the desired trip being in vain. Much time was wasted by employee vigils at dumbwaiter stations, with repeated depressions of the push buttons in effort to obtain an eventual response of the dumbwaiter system.

It is an object of the present invention to provide a dumbwaiter control system wherein a depression of a control button at the time when the dumbwaiter door is open, or at a time when the dumbwaiter car is travelling between stations, will be ineffective to cause an immediate change in the dumbwaiter operation, but will set up such a condition as to cause the desired operation of the dumbwaiter automatically to ensue subsequently, as when the dumbwaiter system is later placed in readiness for the car to make a trip between stations.

In this objective, it is comprehended that a depression of a down control button at a time when the car is travelling upward will automatically result in a subsequent trip downward, and vice versa, and furthermore, it is comprehended that a depression of a control button calling for movement of the car from the station at which it is then located will be given effect immediately upon the closing of a door which had blocked the system operation.

In the achievement of these memory features of automatic delayed operation, the usefulness of the dumbwaiter system would be substantially impaired if the car would be caused to start a return trip immediately after arrival at the station, e. g. as a result of a depression of the up button during a descent of the car. Therefore, arrangements should be included for insuring that after arrival of the dumbwaiter car at a station it will be compelled to remain there a predetermined reasonable time to afford ample opportunity for an operator to open the door for forestalling premature departure of the car and for unloading and/or loading the car.

Accordingly, a further object of the present invention is to provide dumbwaiter control arrangements permitting a dumbwaiter order signal to be given ultimate effect at a subsequent time when the dumbwaiter system is in readiness for a trip, but insuring that the dumbwaiter car will remain at a station an appreciable time before starting on a previously ordered further trip.

Dumbwaiter control arrangements providing these important features are illustrated in the drawings, wherein:

Fig. 1 is a diagram of a control system embodying the present invention applied to a reversiblemotor driven dumbwaiter;

Figs. 2 and 3 illustrate modifications applicable to the general system of Fig. 1;

Fig. 4 illustrates a version of the invention applied to a uni-directional motor dumbwaiter;

Fig. 5 shows a uni-directional motor control system incorporating restricted memory features; and

Fig. 6 illustrates a further modification of the invention providing for registration of simultaneous momentary depression of up and down order buttons.

Corresponding reference numerals are applied to common features of the invention carried through the several drawings, for convenience in reference thereto.

Referring now to Fig. l, a two-stop dumbwaiter is shown embodying a dumbwaiter car 3| and a reversible motor Ill. A first main relay I I is provided for control of power supplied to the dumbwaiter motor ID for operation of the car upward and a second relay I3 similar in all respects to relay H is provided for control of power supplied to the motor ID for driving the car downward. Relay I I comprises a coil 26, a normally closed switch section 22, and three normally open armature switch sections 24, 2B and 28. Relay I3 comprises a coil 30, a normally closed switch section 32, and three normally open switch sections 36 and 38.

A holding relay I having a coil I2 and a normally open armature switch I4 is connected for holding a circuit to the coil of relay I I, and a second holding relay I! having a coil I5 and a normally open armature switch It is connected for holding a circuit to the coil of relay I3. A switch I9 is provided for actuating relay I5, and a switch 2| is provided for actuating relay I'I. Switches I9 and 2| may comprise up and "down push-button switches for a lower station, and ma be duplicated by parallel-connected up and down switches 23 and 25 at the upper station.

An upper limit switch mechanism '27 is provided with a normally closed switch element arranged to be opened by the dumbwaiter car, as diagrammatically by the top of car 3|, upon arrival of the car at the upper station. A lower limit switch 33 is provided to be similarly opened by the arrival of the car 3| at the lower station.

The dumbwaiter car 3| is schematically illustrated as suspended by a cable 4| passing over a sheave 43 and being wound at the end opposite car 3| upon a winch coupled by speed reduction gears 41 to the motor Ill. The upper station is shown provided with a door 5| illustrated as slidable to the right for opening, and the lower station is similarly provided with a sliding door 53. Safety interlock switches and 51 are provided at the upper and lower doors respectively, and are arranged to be held closed only when the doors 5| and 53 are entirely closed. The details of the dumbwaiter car, station doors and limit switches, and cable and motor connections are merely schematic i11ustrationsthese details are subject to wide variations in actual installations.

A time delay relay 59 having a coil 53 and a normally closed armature switch 52 is provided for preventing immediate reversal of the direction of operation of the dumbwaiter, to insure that a reasonable opportunity be afforded for access to the dumbwaiter car upon its arrival at a station. This relay 59 is illustrated as provided with a dash-pot time lag arrangement 54, but any other of the well known delay mechanisms may be employed.

The power for the dumbwaiter system is illustrated as brought in through conductor mains I and 8. These may be the positive and negative conductors of a direct-current system, or the supply may be an alternating-current supply it desired, single-phase or polyphase with an additional motor supply conductor.

Upper limit switch 21 and switches 23 and IS in series therewith are connected between main 1 and one terminal of the coil I2 of relay I5, the opposite terminal of this coil being connected to the other main 3. The armature switch I of relay I5 is connected in shunt with switches I9 and 23. Conductor 63 between coil I 2 and limit switch 21 is also connected to one terminal of relay switch section 32, and through this normally closed section 32 the circuit is continued to the coil 2!! of relay II.

The connections as thus far described of switch I9 (and parallel-connected switch 23), holding relay I5, limit switch 2'! and relays I3 and I I are so arranged that a momentary depression of an up switch when the car is at the upper station is entirely prevented from being effectual. Such a depression ofone of the up switches when the car 3| is away from the upper station and switch 21 is closed, on the other hand, energizes relay l5 and completes a circuit from conductor l through to switch section 32. If relay 3 is not energized, this passes current to the upper terminal of coil 20. In any event, with switch 2! closed, a holding circuit is established through switch 21 and armature switch I4, retaining relay 5 energized; this corresponding to a self-holding condition in relay I5 by virtue of its armature switch circuit.

The establishment of this holding circuit condition for relay I5 is independent of the condition of relay I3, but the upper coil terminal of relay I I can only be brought to the potential of conductor I if relay I3 is not energized, with armature switch section 32 accordingly closed.

Sections 24 and Y34 of relays II and |3 are connected'to motor Ill and arranged so that section 24, when closed, produces clockwise rotation of the motor as seen in Fig. 1 and consequent lifting of the car 3|, whereas closure of section 34' of relay It results in opposite rotation of the motor I9 and downward car movement. Relays I! and I 3 cannot both be energized at any time, because of the cross connections of the circuits of coils 23 and 35] through switch sections 32 and 22.

Down switches 2| and 25, holding relay I'l, lower limit switch 33 and coil 35 of relay I3 are interconnected in just the same manner as de- 1 scribed above with reference to the corresponding up-control parts, as is plainly shown in Fig. 1.

The lower coil terminals of relays II and I3 are connected together by conductor 65, and this conductor is connected through the normally closed armature switch 52 of delay relay 59 and thence through series-connected door interlock switches 51 and 55 to supply conductor 8. Armature switch sections 26 and 36, in parallel, are connected between the lower terminal of coil 5!] and supply conductor 1, and the upper coil terminal of relay 59 is connected through the door interlock switches 51 and'55 to supply conductor 8. With these connections,.relay 59 will be actuated simultaneously with the actuation of either of relays II and I3, the coil 50 remaining energized coextensively with the energization of one of the motor relays, but the armature switch 52 will remain open an appreciable time afterward due to the action of delay mechanism 54. Armature switch sections 28 and 38 of relays I I and I3 are connected in parallel with armature switch 52, so that the actuation of either of the main relays II and I3, though followed immediately by energization of relay 59, will not be interrupted by the opening of-switch 52 in series with coils 20 and 30.

The energization circuit for relay II is traceable from conductor I through an up button switch and thereafter the up holding relay armaannexes .mentarydepressionof a buttonswitch for the corresponding direction, provided that the car .3! ,isnot-already at theextreme of its travel in thatdirection. Thus, ,with the initialconditions asillustrated in Fig. :1, car ,3 I being at the dipper extreme ,of its travel and holding upper limit switch 421 open, a depression :of an up :button could not establish {a holding condition .in relay l and it could not energize relay I I, buta-depression of la. down button produces immediateenergization of .holdingrelay that thesame time instituting theenergization of relay 13. The closureof the armature switch l8 .of relay ll completes a holdingcircuit to retain its-own coil and -the-.coil-,3D of .relay I 3 energized.

The downward shiftof the armature of relay vl3,-through switchseotioni l, energizes such circuits. of motor .lllas to produce counter-clockwise motor vshaft rotation, with resultant downward movementof the car..3 I. ,Atthe same time, switch section i32 being opened, safeguards against energizationof relay I]; switch section 35, being c1osed,.,comp1etes an energization circuit through the .coil -,50 of relay 58; and switch section 38, being closed, shunts lswitch section 5 2 of. relay 59 as this section is opened by the energization of coil 50.

If the ,dumbwaiter doors .5! and 53 remain closed for a .sufificient time, the dumbwaiter car v3| will be caused to continue its downward journey untilit reaches the lowerstation, where it. opens switch 33 and thus opens the downrelay holding circuit, causing the return of relays l1 and I3 totheir ole-energized.conditions,:andshutting off the power from .motor 1i! and the coil .50 of relay 59. .As ,pointed out heretofore, delay mechanism .54 prevents the immediate returnof thearmature switch 52 to .the closed condition,

so that. even though the armature switch section 32 .of relay il 3 lreclosed immediately upon the arrival ,of the car..3.l rat the lower station, the coil circuit oflrelay .H cannotimmediately be com pleted foran instantaneous return of the car 3| to the .upper station from which it has just-descended. ,At the end of the predetermined delay time .of relay 5.9, however, the armature switch 52 thereof recloses, so that relay [-1 may thereafter be energized to .send car 3| upward, provided that the .dumbwaiter door 53 was left anopened or has been lopenedand .reclosed.

Now, if vno up ordersignal had been given by amomentary depression of one of the up switches 19 and ,23 during thedownwardtripof the dumbwaiter car 3| orduring the predetermined delay time assured by relay 59, thecarBl remains inactive even after the delay .reclosing ofswitchsection "5.2 of relay 58. Asubsequent depression of an upbn'ttonsets the system in operationfor the triip upward, according to the operating principles outlined above and illustrated in reference to a'trip down to the lower station.

As outlined in the introductory paragraphs, however, the present invention goes beyond the modes of operation described above, toprovide a delayed response "to an order signal instituted by a control button depression, the car and motor system being made "to obey the order at a later time when all circuit obstacles are removed from .thezcoil circult'of the-required one of mainrel-ays 11,16. :Aflepressionof: one of the up buttonsl9, 23 during the downward trip previously described, though prevented from causing immediate actuationeofrelay =ll by the opened-circuit condition of switch section 3'2,'momentarily actuates holding relay -l5-and sets upthe armature holding circuit thereof, providing a sustained circuit portion from-conductor to armature section 32,awaiting the time whenrelayw will have returned to its normal condition with section 32 closedand thearmature of relay 59 willhavereturned to .i-tsznormal.restingposition with switch 52 closed. Accordingly, when the predetermined delayinterval haselapsedafter the arrival of the .car3l rat the lower station, the circuit for energization of coil 2 of relay I! automatically is completed, and the motor ill then proceeds to haul .car 3| upward .in obedience to the order instituted by the button depression accomplished during the prior downward trip.

This .delayedioperation feature, with performanceas though the control system were endowed withmemory, likewise applies to operation of the system in response to a depression of an order button at a time when one of thedumbwaitei' doors I53, '55 was open. In this case, as before, the coilcircuits of relays II land i3 are prevented from being energized 'immediatelyybut the appropriate one of holding relays 15,41 is actuated to establish a holding circuit from conductor 1 through the :coil of the desired one of main relays ll, l3 and through armature switch 52 up to .the opened door switch, so that upon -reclosureof the dumbwaiter door, the proper main relay is actuated to cause the desired operation of motor [0 and resultant movement of car 3|.

For example, considering the dumbwaiter sys-- tem again in the conditionsprevailing in'Fig. 1, the door 5| atlthe upper station may be opened for unloading and/or loading car 3|. Meanwhile, an operator at the lower station, requiring the return of the dumbwaiter car, may depress the down button, momentarily closing switch 21 andthereby actuating relay ll. The armature switch thereof, attracted downward, sustains the energization of coil H3, and at the same time retains complete the circuit portion between conductor 7 and the coil 36 of relay l3. This relay 13 remains inactivehowever, until an operator at the upper station recloses the door '51, with consequent closure-of switch 55 and the resulting completion of the coil circuit of relay l'3.

Upon this occurrence, the car3l is set in motion downward in delayed response to the order signalled'by the earlier depression of switch 28, and from this point onward, the operation of the dumbwaiter continues until the .car 3i reaches thelower station and the system is automatically turned oiT,.in the same manner as was described above in the case of .an immediate response to an order signal given when all circuits were in readiness.

Fig, 2 illustrates an alternative arrangement of the holding relays in such a way that they serve as upper and lower limit switches as well as holding circuit devices. These holding relays, designated I5 and H, are positioned at the upper and lower stations, respectively, and are provided with respective projecting portions 1! and 73 for engagement by a cam '85 on car 3!. The separate limit switches '2'! and 3-3 of Fig. 1 are obviated by this arrangement of the holding relays, since the cam '15 is thus made positively to insure that a holding relay armature switch, holding closed and retaining the appropriate main relay energized for the approach of the car 3| toward that holding relay, will be opened upon arrival of the car 3| at the destination.

A still further optional form for the holding arrangements is illustrated in Fig. 3. Here, as in Fig. 2, the limit switches 2'7 and 33 may be dispensed with, the up-movement holding relay I" and the down-movement holding relay (not shown) being placed at the upper and lower stations, respectively, and being provided with camoperated tripping devices as illustrated at I5, TI, I9. Relay I5" is provided with a mechanical latch "I9 on the armature, arranged to rest normally below a receiving projection on the pivoted arm 'I'I.

Upon actuation of the coil I2 of the holding relay I5", the armature thereof is drawn upward, so that the armature switch I4 is closed. At the same time, the latch I9 is brought into engagement with the receiving projection on arm H, which rests on pin 8| and sustains the armature in the attracted position so that it does not return to the normal position after the momentary actuation of the coil circuit. Thus, the relay is mechanically held in the closed-circuit condition, as illustrated in Fig. 3A, while the car 3| is hauled upward in response thereto.

As the car 3| arrives at the upper station, the cam I5 engages the end of the pivoted arm I7, swinging this arm over to the left and disengaging the latch I9, so that the armature switch system falls open. The motor circuit is consequently de-energized, and the dumbwaiter propulsion system is thus brought to rest in generally the same manner as described in reference to Fig. 1.

The choice of the details of a holding arrangement among those illustrated in Figs. 1, Z and 3 will depend upon the details of a particular dumbwaiter system.

Fig. 4 illustrates the application of the control circuits of Fig. 1 to a dumbwaiter system of the endless chain or belt type employing a nonreversing motor drive. The cable 4| by which the dumbwaiter car 3| is suspended is attached at its upper end to a pin IGI fastened to a link of an endless chain I03. This chain passes over an upper sprocket I05 and a lower sprocket I91, the sprockets being spaced apart by a vertical separation of the order of the distance of travel required of the dumbwaiter car between upper and lower stations.

One of the sprockets, e. g. sprocket W5, is coupled as through a speed-reduction gear system I09 to a drive motor III]. This motor is connected in series with shunt-connected armature sections 24 and 34 of relays II and i3, between the mains I and 8. Hence, the motor IIB drives the chain I03 in only one direction (illustrated as the counter-clockwise direction) whether activated through relay II or through relay I3. As is readily apparent, however, such uni-directional operation provides alternate upward and downward trips of the dumbwaiter car 3|.

The upper and lower limit switches are arranged for operation by a cam IEI afiixed to the chain I03, such switches being illustrated at El" and 33'. The push-button switches I9, 2|, 23 and 25, relays I5, I! and 59, and door switches 55 and 51 are connected with relays II and I3 in the same manner as in Fig. 1, and these parts of the system of Fig. 4 operate in just the same manner as in Fig. 1. The system is illustrated in Fig. 4 as bein in operation with the dumbwaiter car rising, approaching the upper station. Relay I5, having been momentarily actuated through one of the up button switches I9, 23, has established a holding circuit retainin the upper terminal of the coil 20 of relay I I in circuit with conductor I, and relay II is energized, providing the rotation of motor III) for drawin the car 3| upward.

When the car 3| reaches the upper station, the cam III will lift the contact bar of upper switch 21', breaking the holding circuit of relay I5 and accordingly restoring relays I5 and II to their normal rest conditions. This will open the supply circuit of motor III], so that the drive chain I93 is brought to rest.

The delayed operation or memory features of Fig. 1 are fully provided in the system in Fig. 4. If, for example, a down order is registered by a momentary depression of one of the down pushbutton switches as the car 3| is being lifted toward the upper station, e. g. at the moment of the conditions illustrated in Fig. 4, such a depression institutes a holding circuit in relay ll. Such a circuit does not cause the car 31 to be carried on through the upper station end of its route and again immediately downward, but instead, provides for completion of the coil energization circuit of relay I 3 only after the predetermined delay interval insured by relay 59. Furthermore, a signal given at a time when a door switch is open is given delayed effect, exactly as with the system of Fig. 1.

Fig. 5 illustrates a version of the present invention capable of providing delayed operation in response to a push-button order signalled while the car 3| is at rest at a station, its immediate response being then prevented either by an open door switch or by an open condition of the switch .52 of delay relay 59 during the predetermined period following arrival of the car 3| at the station. This system, employing a smaller number of control elements with somewhat simplified circuit connections, lacks the feature of delayed operation in response to a push-button order signalled while the system is in motion with the car 3| travelling from one station to the other.

Only one push-button switch is provided at each station, the lower station switch being shown at H9 and the upper station switch being shown at I23. A single holding relay H5 is provided, and a single main control relay IZI is likewise employed. The door switches 55 and 51, the endless chain ||l3 on sprockets I95 and Iill, and the uni-directional drive motor IIU coupled through speed reduction gears I09 are arranged in generally the same manner as shown in Fig. 4. In the system of Fig. 5, two cams III and I I" are provided on the chain I03, and a single stationstop switch I 21 is arranged to beactuated by whichever of these two chain cams next arrives in contact therewith.

The control elements in Fig. 5 all are illustrated as at rest, the car 3| being at the lower station, the doors (which, though not shown, may be considered as slidable to the left to be opened) being closed, the relays 59, H5 and E25 being in their normal conditions, and the lower-stop cam I I I" being in the position just beyond switch I2! to which it is carried by the drive system momentum, so that switch I21 is closed.

Now, a depression of one of the push-button switches I I9, I23 will momentarily energize the holding relay H5, and through the armature switch H4 thereof the holding circuit is thereafter sustained. Through armature switch H4, the energization circuit through coil izil of main relay l2l is established, the coil current momentarily flowing through the armature switch 52 of relay 59. This energization of coil 129 pulls the armature of relay l2! downward, closing switch section I34 and energizing the motor Hi1 therethrough, and producing clockwise rotation of chain 13 so that the car 311, after moving downward slightly, is drawn. upward. toward the upper station. With the energizationoi coil 12c, switch sections I36 and [38 of relay 121 are closed also, the former completing the circuit for energization of the delay relay 59, and the. latter at the same time shunting the armature switch 52 of the delay relay, preventing the circuit to coil. lit from being opened.

The holding circuit of relay H5 now remains complete, with continuedoperation of the system, until the car 34 has been drawn up to the height of the upper station, the cable coupling pin IBI having been drawn to the top of sprocket m5. At this point, cam I l I depresses stop switch i2l, momentarily opening. the holding circuit of relay H5, and through relay i2i, arresting the energization of motor Hi1. Here, again, the cam H l is carried just beyond switch l2? by the momentum of the drive system, so that switch I21 is reclosed in readiness for a further trip of the car. The connections of switches H9 and 123 with relay H5 and relay [2! are such that even if the lowermost one of the cams failed to be carried beyond switch I21, and remained in the position holding this switch open, the motor 1 it is actuated through relay l2| during the depression of one of the push-button switches, so that the offending cam is carried on beyond switch 21 and the holding circuit is then established for insuring the proper completion of the dumbwaiter car trip, to be terminated in the usual manner by the further operation of switch I21.

The time delay relay 59 operates here in just the same manner as in. Figs. 1 and 4, iorestalling the further energization of the main relay I21 until the predetermined time interval has elapsed after the last preceding trip. A depression of one of the push-button switches while the holding circuit through relay H5 is complete and the car 31 isinmotionhas no effect, since these switches are shunted at such times by armature switch H4. A depression of one of the pushbutton switches whie the car Si is at rest at one of the stations is fully effective, however, in the same manner as with the systems oi Figs. 1 and 4. An open door switch at. the moment of depression ofv the push-button switch, or an open condition of armature switch 52 following a very recent trip of the car 3i, can prevent immediate operation of. relay l-2l and motor H0, but a holding circuit is established through relay H5, awaiting the readiness of the circuit through armature switch 52 and door switches 51 and 55* for delayed operation of the system.

The embodiments of the present inventionas thus far described have. in common the requirement that an order fora return toa station cannot be eiiectuallysignalled tothe dumbwaiter system until initiation of the movement of the car away from that station. As heretofore pointed out with respect to Fig. 1', for example, a holding circuit condition for returning the car to a station could only be set up after: the institution of progress oi the car from that station. If the up button. was depressed when the car was at rest at the upper station, for example, such a depression would be entirely inefi'ectual. Only a. depression of the up button continuing until after the commencement of the downward movement, or a depression of the up button initiated after that time, could establish the holding circuit conditi'on required to insure the subsequent automatic return of the car to the upper station.

An embodiment of the invention providing for the establishment of a holding condition for returning the car to a station, in response to a signal; given even before its departure from that station, in addition to all other features or the system of Fig. l, is illustrated in Fig. 6. Up and down holding. relays 2 I 51 and 21 1, respectively are provided for actuation through an associated one of control button switches I 9, 2| 23, 25, through one of the limit switches 21, 33, generally in the same manner as described in connection with Fig. 1. Similarly, a pair of main relays 2H and Z'ii are provided for actuation. of the up and d own propulsion windings of the dumbwaiter drive motor, and are connected to the time delay relay 5 8 as in Fig. 1, for insuring that the car will wait at a station for at least a predetermined intervalto enable an operator at that station togain access to the car and to hold it as long as necessary for unloading and/or loading it.

Two. further relays 2M and 2-03 are provided in 6, connected generally intermediate between the holding relays and the main motor control relays; and car cam-operated switches 2e? and 299 are added in circuit with the coils of these further relays.

Relay 255 comprises coil 2l2 and three norrnal-ly open armature switch sections 2, 2M and 2%; Relay 211' comprises coil 216'- and three normally open. armature switch sections 218 205', and 208. Relay 2M comprises a coil- 243, two normally closed switch sections 241 and 242, and a normally open armature switch section 240. Relay 2.53 similarly comprises a coil 241, two normally closed armature switch sections 245 and 24d, and anormally open. switch section 244. Relay 2H: comprises a. coil 220 and three normally open armature switch sections 224-, 2.26 and 228. similarly, relay 2l3 comprises a coil 230 andthreenormally open armature switch sections ass, 235 and 238'.

Switch sections. 245 and 242' are connected in series with coils 2219' and 230, respectively", so that operation of relay 2| I is blocked when relay 2533: is actuated, and operation of relay H3 is blocked when relay 20| is actuated. Switch section 24! is connected in series with coil 2'41, and switch section 245 is connected in series with coil 243, so that when one of the intermediate relays 2!, 203. is energized, it blocks the energization of the other;

Sections 24d and 244 are connected in parallel with limit switches 2'7: and 33', respectively. Switch section 25 1' is: connected in. series with switch section 24:6 and coil 20 of reiay' 2, so that closure of this section at a time whenrelay 203 is not energized causes the actuation of relay Zit and the consequent upward movement o'f the durnbwaiter car; Similarly, switch section 205 is connected in series with; switch section 242 and the coil 23! of relay 21 3 -With-. the circuit connections as illustrated in Fig;.. 6; a car return holding circuit condition can be: established when the car is at rest at a station. For: example, it the car is at rest at the upper station, an upbutton can be depressedfor the storage of a signal to be given effect after thecar has moved down to the lower station and waited there the predetermined delay interval. When the car is at rest at the upper station, the car cam I holds switch 2%? closed and upper limit switch 21' open. Through switch 201 and switch section 241, the coil 24'! of relay 203 is energized, so that the actuation circuit of relay 2!! .is blocked and switch section 244 is closed. across the upper limit switch 21.

If an up button were depressed under the conditions illustrated, it would momentarily effect the actuation of the coil of holding relay 215 whereupon armature switch section 2M would retain this circuit complete, the relay being thus arranged for self-holding. No current would immediately be permitted to flow through either of switch sections 2214, 296, however, since sections 245 and 246 of relay 293 are held open so long as relay 25313 remains energized, and relays 203 and Zill are so interconnected with car operated switches 27, 33, 2d? and 299 that relay 203 must remain energized until the car has moved to the lower station.

A depression of a down button, on the other hand, not only would result in the establishment of a down order circuit condition in self-holding relay 2 I l but also would result in the down-direction operation of the car drive motor as a result of the actuation of relay 253 through switch sections 295 and 2 52. As the car consequently proceeds downward, the descending cam 15 first allows the upper limit switch 21 to be reclosed, and soon thereafter clears switch 20'! so that the latter is opened. Neither the closing of switch 27 nor the opening of switch 2M has any immediate effect upon the operation of the dumbwaiter system, as closed switch section 244 shunts switch 2! and closed switch section 208 of the actuated holding relay 2!? shunts switch 201.

As the car approaches the lower station, cam 15 first closes switch 2%, thereby providing such a condition that relay 2M will be actuated if the energization of relay 263 is momentarily interrupted. Then, as the car reaches the position desired at the lower station, cam 15 opens the lower limit switch 33, opening the circuit through coil 2 l S of relay 2 l l and thereby bringing its self holding circuit condition to an end. The resultant interruption of current flow through switch section 298 causes the release of the armature of relay 263, and relay 20! is thereupon energized through switch 2%9 and the now reclosed armature switch section 2 55. Furthermore, the opening of switch section 205 of holding relay 2i! at the holding condition interruption breaks the circuit to motor relay 213, arresting the energization of the motor and stopping the descent of the car at this position at the lower station.

As in Fig. 1, relay 59 is energized coextensively with either motor control relay, and at the time of de-energization of relays 2 l3 and 59, the armature switch 52 of relay 5!! remains open the predetermined delay interval to block an immediate return of the car to the upper station whence it has just descended.

If there has been no depression of an up button since the last preceding trip of the car up to the upper station, the holding relays are now both left in non-energized condition, and the system is capable of receivin and holding a down order, or capable of receiving an up order and responding thereto after the predetermined interval required for the reclosing of the time delay relay 59 in the same manner as discussed with reference to Fig. l.

Let it be supposed that an up button was depressed before commencement of the cars descent, as either before the depression of the down button or simultaneously therewith, or that it was depressed during the downward movement of the car. Regardless of the sequence of the depressions of the up and down buttons while the car was away from the lower station, the appropriate holding circuit condition was established in the up holding circuit in addition to the above discussed down holding circuit, and moreover, the interconnections of relays 2M and 203 with relay 2G3 energized insured that the car would be moved downward before it could respond to the up order.

It will be apparent from the above outline of the operation of the arrangement of Fig. 6 that the one of the intermediate relays Elli and 203 which is energized blocks the operation of the motor relay connected therethrough and therefore prevents operation of the motor in one direction; and it will similarly be apparent that a change-over occurs between relays 26! and 203 upon each arrival of the car at one of the terminal stations, and only then. Moreover, these added relays, together with the associated switches 26? and 2539, provide all the features of the system of Fig. l with the added feature that a return trip holding circuit condition can be established even before the commencement of a trip of the car from a station.

Since many changes could be made in the above construction and many apparently 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.

I claim:

1. A dumbwaiter system comprising a dumbwaiter car, means for guiding said car between predetermined stations, means for propelling said car between said stations, control means including an electric actuation circuit for controlling said propelling means, manually operable controller means to be actuated for sig nalling an order for the car to proceed to a station, means actuatable by said manually operable controller for holding a connection to said electric actuation circuit, means for tripping said holding means upon arrival of said car at the station to which ordered, and means for blocking the energization of said actuation circuit but leaving intact said connection held by said holding means; said propelling means comprising an electric motor, said control means comprising an up control relay and a down control relay including armature switch elements connected to said motor, said manually operable controller means comprising an up button switch and a down button switch for selective directional control of said dumbwaiter car, and said holding means comprising a first holding relay and a second holding relay, said first relay being coupled to said up button switch to be initially energized therethrough and having an armature switch coupled to the actuation circuit of said up control relay, and said second holding relay being coupled to said down button switch to be initially energized therethrough and having an armature switch coupled to the actuation circuit of said down control relay, said holding means further comprising means for retaining one of said armature switches set from the time of actu- 13 ation of the respective push button switch until tripped by said tripping means.

2. A dumbwaiter system as defined in claim 1, wherein each one. of said. holding relays comprises an armature switch section connected to the actuation circuit thereof to supply actuation-sustaining energy thereto after a momentary energization through the related button switch.

3. A dumbwaiter system as defined in claim 2, wherein said tripping means comprises means operated upon arrival of said car at a station for interrupting the actuation-sustaining energy fiow through said armature switch section.

4. A dumbwaiter system as defined in claim 3, wherein said tripping means comprises means for blocking the circuit through the up button switch when the car is at the uppermost station and for blocking the circuit through the down button switch when the car is. at the lowermost station.

5. A dumbwaiter system comprising a dumbwaiter car, means for guiding said car between predetermined stations, means for propelling said car between said stations, control means including an electric actuation circuit for controlling said propelling means, manually operable controller means to be actuated for signalling an order for the car to proceed to a. station, means actuatable by said manually operable. controller for holding a connection to. said electric actuation circuit, means for tripping said holding means upon arrival of said car at the. station to which ordered, and means for blocking the energization of said actuation circuit but leaving intact. said connection held by said holding means; said blocking means comprising at least one station door interlock switch for blocking the. actuation of said con trol means. so long as a. station door is open.

6. A dumbwaiter system as defined in claim 5, said actuation circuit comprising an electromagnetic control unit coupled to said propelling means for energizing it. to. propel said car to one or said stations, said means. actuatable by said manually operable controller means comprising a relay having an armature contactorconnected to its coil to sustain energization after initiation thereof through said manually operable. controller means, and said means for tripping said holding means comprising a normally closed cam-operated switch arranged to be opened by arrival of said car at said one station.

7. A dumbwaiter system comprising a. dumbwaiter car, means for guiding said: car between predetermined stations, means for propelling said car between said stations, control means including an electric. actuation circuit for controlling said propelling means, manually operable con. troller means. to be actuated for signalling an order for the car to. proceed to. a station, means ac tuatable by said manually operable. controller for holding a connection to. said electricv actuation circuit, means for tripping said holding means upon arrival of said car at the station towhich ordered, and means for blocking the energization of saidactuation circuit but leaving intact said connec-- tion held by said holding means; said blocking means comprising a time delay relay having a control circuit connected. tosaid control means to be actuated substantially coextensively therewith and to block the actuation of said control means a predetermined time interval after each tripping of said holding means and consequent termination of actuation of said control means.

8. A vertical lift. control system comprising a car, means. for guiding said car between anupper station and a lower station, means for propelling said car between said stations, first. and second. main control relays connected to said propellingmeans for upward propulsion and downward, pros pulsion, respectively, first self-holding. relay means connected to said first main control relay for sustaining actuating current therethrough and second self-holding relay means connected to said second main control relay for sustaining actuating current therethrough, upper station interrupter means for interrupting the holding of said first self-holding relay means when said car reaches said upper station,. lower station interrupter means for interrupting the holding of said second self-holding relay means when said car reaches said lower station, and means connected in circuit with said first and second main control relays for blocking the actuation therethrough of said propelling means until predetermined conditions prevail in the dumbwaiter system, said first and second self-holding relay means being independent of said means for blocking actuation whereby a holding condition can be commenced in one of said self -holding means or continued therein if previously commenced notwithstanding actuation of said propelling means being blocked by said actuation blocking means.

9. A system as defined in claim 8, wherein said upper station interrupter means comprises. means for preventing the establishment. of a self -holding condition in said first. self-holding relay means when said car is at said upper station and lower station interrupter means. comprises means for preventing the establishment: of a self-holding condition in said second self-holding relay means when said car is at said lower station, whereby said upper and lower station interrupter means safeguard against operation of said propelling means to. send said car beyond the normal range of movement between. said stations.

10. A system as defined in claim 9,. wherein each of said self-holding relay means comprises a relay having an actuation coil circuit and a normally open armature switch connected thereto for sustaining actuating current theretov following a momentary attraction of the armature,v and the one of said station interrupter means associated. therewith comprises a. normally closed limit switch connected in series with said normally open armature switch and means for open-ing said switch upon arrival of said car at a station.

11. A system as defined, in claim 8., wherein each of said self-holding relay means comprises: a relay having an actuation coil circuit and a nor" mally open armature switch connected between said actuation coil circuit and the power connections therefor to sustain an. actuated condition therein after momentary actuation of the selfholding relay, and the interrupter means. comprises means coupled to said car for forcing said self-holding relay open.

12. A. system as defined in claim 8,. whereinv said first self-holding relay means. is. capable of receiving and holding a call to said upper station when said car is at rest at said upper station and said second self-holding relay means is. capable of re ceiving and holding a call to said lower station when car is atv rest at said lower station, whereby a signal condition may beinstituted at a station when the car is at that station to insure its return thereto after any departure thereof.

13. A system as defined in claim 8, wherein said first self-holding relay means comprises means for receiving and holding a call tosaid upper station at any time irrespective of position or motion of said car, and saidsecond self-holding relay 15 means comprises means for receiving and holding a call to said lower station at any time irrespective of position or motion of said car.

14. A system as defined in claim 8, wherein said first self-holding relay means comprises means for receiving and holding a call to said upper station when said car is in downward movement or at the lower station, and said second seli-holding relay means comprises means for receiving and holding a call to said lower station when said car is ascending or at said upper station, said first self-holding relay means being prevented from receiving a call when said car is at rest at said upper station and said second self-holding relay means being prevented from receiving a call when said car is at rest at said lower station.

15. A vertical lift system comprising a car, means for propelling said car along a substantially vertical path between an upper station and a lower station, an up order switch button, a down order switch button, means responsive to an actuation of said up order switch button when said car is at rest at either station or in downward transit for holding an up order circuit condition, means responsive to an actuation of said down order switch button when said car is at rest at either station or in upward transit for holding a down order circuit condition, means for actuating said propelling means in response to said up order circuit condition, means for actuating said propelling means in the direction to provide downward progress of said car in response to said down order condition, means for blocking the upward propulsion of said car in response to said up order circuit condition until said car has remained at said lower station a predetermined period of time following its arrival there, means for blocking the downward propulsion of said car until said car has remained at said upper station a predetermined period of time following its arrival there, means for interrupting said up order circuit condition upon arrival of said car at said upper station in response thereto, and means for interrupting said down order circuit condition upon arrival of said car at said lower station in response thereto, each of said holding means being capable of responding to the respective switch button actuation irrespectime whether an order circuit condition is held in the other holding means.

16. A conveying system comprising a car, a hatchway containing said car and having two stations between which said car can be propelled in said hatchway, first electrically operable means for propelling said car toward a first one of said two stations, second electrically operable means for propelling said car toward the second one of said two stations, a first self-holding circuit for receiving and holding a call and for actuating said first electrically operable means, a second selfholding relay circuit for receiving and holding a call and for actuating said second electrically operable means, said first and second electrically operable means being interconnected for each when energized to block the actuation circuit of the other, said first self-holding relay circuit including a normally open relay armature contactor and a first car-operated station-stop switch connected in series in its actuation circuit, the switch being normally closed but being arranged to be opened by arrival of the car at said first station, said second self-holding relay circuit including a normally open relay armature contactor and a second cam-operated station-stop switch connected in series in its actuation circuit, the switch being normally closed but being arranged to be opened by arrival of the car at said second station, at least one manually operable momentary contact switch in shunt with each of said armature contactors for holding circuit initiation when the car is absent from the station for which the call is initiated, first means coupling said first self-holding relay circuit to said first electrically operable means, and second means coupling said second self-holding relay circuit to said electrically operable means, said first and second coupling means including the interconnections therebetween.

17. A control system comprising a car, a hatchway containing said car and having two stations between which said car can be propelled in said hatchway, first electrically operable means for propelling said car toward a first one of said stations, second electrically operable means for propelling said car toward the second one of said two stations, a first self -holding relay for receiving and holding a call for said car to be propelled to said first station, a second self-holding relay for receiving and holding a call for said car to be propelled to said second station, a first intermediate relay connection between said first self holding relay and said first electrically operable means, a second intermediate relay connected between said second self-holding relay and said second electrically operable means, said first and second intermediate relays being interconnected for prevention of concurrent actuations thereof, a first normally closed switch and a first normally open switch arranged for cam operation upon arrival of said car at said first station, a second normally open switch and a second normally closed switch for cam operation upon arrival of said car at said second station, at least one first-station call switch and a normally open armature contactor of said first self-holding relay connected in parallel with each other and in series with said first normally closed switch in the actuation circuit of said first self-holding relay, at least one second-station call switch and a normally open armature contactor of said second self-holding relay connected in parallel with each other and in series with said second normally closed switch in the actuation circuit of said second self-holding relay, said first self-holding relay having a normally open contactor connected in shunt with said second normally open switch and in series with the actuation circuit of said second intermediate relay including the cross-connection through a normally closed contactor of said first intermediate relay, and said second self-holding relay having a normally open contactor connected in shunt with said first normally open switch and in REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,889,312 Gale Nov. 28, 1932 2,240,044 Kramer Apr. 29, 1941 2,250,272 Myers July 22, 1941 2,259,449 I Bartholomew Oct. 21, 1941

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