US3903996A

US3903996A - Closure system

Info

Publication number: US3903996A
Application number: US426180A
Authority: US
Inventors: Harry Berkovitz; Lawrence Tosato
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1973-12-18
Filing date: 1973-12-18
Publication date: 1975-09-09
Anticipated expiration: 1992-09-09
Also published as: GB1495392A; BE823497A; BR7410467D0; CA1010585A; JPS5094650A; FR2254710A1; ES433025A1; FR2254710B1; IT1024061B; JPS5437739B2; DE2459677A1; AU7629274A

Abstract

A closure system for an entranceway having a door mounted to open and close the entranceway. A perforated sill, in combination with a source of radiant energy provides a plurality of vertical beams of radiant energy spaced across the entranceway. A detector device is mounted to be responsive to at least one of the beams to detect interruption of radiant energy to the detector device by an object in the entranceway. In a preferred embodiment, the source of radiant energy includes energy having a wavelength in the visible spectrum, highlighting the sill as well as forming an operative portion of the object detection function.

Description

Sept. 9, 1975 United States Patent [1 1 Berkovitz et al.

[ CLOSURE SYSTEM Inventors: Harry Berkovitz, Glen Rock; Primary Examifi1er Ev0n Blunk Lawrence Tosato, Minbum1 both of Assistant Examiner-James L. Rowland NJ.

Attorney, Agent, or FirmD Rv Lackey [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

ABSTRACT [22] Filed: Dec. 18, 1973 A closure system for an entranceway having a door [2] 1 App! 426l8o mounted to open and close the entranceway. A perforated sill, in combination with a source of radiant energy provides a plurality of vertical beams of radiant [52] US. Cl. 187/52; 49/25; 250/22] B66B 13/26; EOSF [5/20 [5 l] Int. energy spaced across the entranceway. A detector de- [58] Field of Search 187/52, 56, 51, 48, DIG. l; vice is mounted to be responsive to at least one of the 250/221; 49/25, 26, 27, 28 beams to detect interruption of radiant energy to the detector device by an object in the entranceway. [n a [56] References Cited preferred embodiment, the source of radiant energy UNITED STATES PATENTS includes energy having a wavelength in the visible spectrum, highlighting the sill as well as forming an 2/1934 Ellis 187/52 9/1960 187/48 operative portion of the object detection functionv Drexler....,.........,...............,..

FOREIGN PATENTS OR APPLICATIONS 1 Claim, 4 Drawing Figures 685,788 5/[964 Canada..,...,...........,....,,........ 187/52 PATENTED SEP 9 75 SHEET 1 BF 2 NQI CLOSURE SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates in general to closure systems, and more specifically to closure systems which include an object detection function.

2. Description of the Prior Art In closure systems of the prior art, especially those used in elevator systems, it is common to provide some means for preventing the closure or door from striking an object in its closing path. One well-known type of door protective device employs a beam of radiant energy which is projected across the elevator car opening. Interruption of the beam by an object disposed substantially in the closing path of the car and hoistway doors results in a modification of the door operation, such as by stopping and reversing the doors.

Another commonly used type of door protective device is the mechanical safety edge. When the mechani cal safety edge, usually disposed on the car door, is depressed, limit switches are actuated which are connected in the door control circuits to effect a predetermined control action. U.S. Pat. No. 2,953,2l9, which is assigned to the same assignee as the present application, discloses a safety edge for the car door which is provided by disposing transmitters of radiant energy and detectors thereof on the car door, such that vertical beams of radiant energy are disposed along the edge of the car door to detect objects having a predetermined relationship with the edge of the door.

As illustrated in U.S. Pat. No. 3,063,516, which is as signed to the same assignee as the present application, it is also known, in a single closure system, to employ both the door edge protection, which is effective when the door contacts or bears a certain predetermined relationship to an object, and protection for modifying the door action when an object is detected in the door opening irrespective of the location of the door relative to the object.

SUMMARY OF THE INVENTION Briefly, the present invention relates to new and improved closure systems, and especially to new and improved closure systems for elevators. An entranceway having a door mounted for movement to open and close the entranceway includes a sill, which in combination with a source of radiant energy, provides a plurality of substantially vertically extending beams of radiant energy spaced across the entranceway. The sill includes a plurality of spaced openings, with the source of radiant energy being disposed below the sill. Thus, a single source of radiant energy may be used to provide a plurality of beams of radiant energy, and this sin gle source is used, as set forth in difierent embodiments of the invention, to provide object detection means without regard to the position of the object relative to the door, and/or object detection means for objects having a predetermined relationship to the edge of the door. In a preferred embodiment, the source of radiant energy emits energy which is visible to the human eye, to provide the additional function of highlighting the sill of the entranceway.

BRIEF DESCRIPTION OF THE DRAWINGS The invention may be better understood and further advantages and uses thereof more readily apparent,

when considered in view of the following detailed description of exemplary embodiments, taken with the accompanying drawings, in which:

FIG. 1 is a view in front elevation, with portions broken away, of an elevator car having a closure system embodying the teachings of the invention;

FIG. 2 is a side elevation of the closure system shown in FIG. 1;

FIG. 3 is a fragmentary, cross-sectional, enlarged view of the closure system shown in FIG. 1; and

FIG. 4 is a schematic diagram of door control appara tus suitable for operating the closure system shown in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS Although aspects of the invention are applicable to closures designed for various applications, the invention is particularly suitable for closures or doors employed in elevator systems. Consequently, the invention will be described with particular relation to elevator closures or doors. Furthermore, aspects of the invention are applicable to doors of various types, such as center-opening or side-opening, double or single, attendant-operated or automatically-operated door assemblies. For the purpose of discussion, however, reference will be made to door assemblies of the horizontally slidable centeropening type as employed in elevator systems.

Specifically, the closure system shown and described in US. Pat. No. 2,992,818, which is assigned to the same assignee as the present application, will be illustrated, and the control circuitry of this patent is shown with the necessary modifications in the present application to illustrate a control system suitable for operating a closure in accordance with the teachings of the invention. Since a detailed description of the door control circuitry is available in U.S. Pat. No. 2,992,818, only the portion of the control circuit associated with the invention will be described in detail.

Referring to the drawings, FIG. 1 illustrates an elevator car having a center-opening door 1 for opening and closing an elevator car entranceway 3 through which load may enter and leave the car. This elevator car may serve any desired number of floors or landings. Since suitable control mechanisms for elevator cars are understood in the art, further discussion thereof is unnecessary for an understanding of the invention.

Car door 1 comprises two sections 5 and A5. In FIG. 1 the door is shown in its fully open position. A number of similar components are employed for the door sections 5 and A5. Insofar as is practicable, a component for the door section A5 which is similar to a component for the door section 5 will be identified by the same reference numeral as is employed for the corresponding component associated with the door section 5 prefixed by the letter A.

The door section 5 is provided with a door hanger 7 on which door hanger wheels 9 are mounted for rotation. The door hanger wheels for the door sections 5 and A5 are positioned for movement along a horizontally-mounted track II in a conventional manner. The track 11 is secured to the elevator car by any suitable means.

Movement of the door section 5 is effected by a lever I3 pivotally mounted on the elevator car by means of a pin 15. The lower end of the lever 13 is pivotally connected to one end of a link 17, the other end of the link being pivotally connected to the door section 5. Lever 13 is coupled to the lever A13 by a link 19, the ends of which are pivotally attached to the levers 13 and A13 by pivots 21 and A21, respectively. Pivot 21 is positioned above the pin 15, whereas the pivot A21 is located below the pin A15. Consequently, rotation of the lever 13 to open the door section moves the link 19 in the proper direction to open the door section A5.

The lever 13 preferably is operated by a suitable door operator 23 which may include a reversible electric motor 25 coupled through suitable gearing to a shaft 27. The shaft 27 carries an arm 29 which is pivotally connected to one end of a link 31, the remaining end of the link 31 being pivotally connected to the lever 13. Consequently, the motor 25 may be energized in a conventional manner for the purpose of opening and closing the door sections 5 and A5. When the door 1 is to be closed, the motor 25 is operated to rotate the arm 29 in a counterclockwise direction as viewed in FIG. 1. in order to open the door, the electric motor is reversed.

A control assembly 33 is mounted on the elevator car adjacent the motor 25. Positive driven contact cams located in the control assembly 33 control the rate of acceleration and deceleration of the door 1. The control assembly also houses control contacts and control resistors. The contact cams are keyed to the gearing associated with the motor 25 and operate the control contacts for predetermined distances of travel of the arm 29 to vary motor armature circuit resistance, thus controlling the doors rate of acceleration and of deceleration. Each cam is symmetrical and operates two spring-closed contacts, one contact being located on each side of the cam. For each direction of door movement, a separate and identical set of contacts is actuated, one for the opening movement of the door, the other for the closing movement of the door. Such arrangement is well known in the art.

The elevator door sections 5 and A5 are each associated with a hoistway door section, which sections are operable for opening and closing a hoistway entrance. FIG. 2 illustrates one of the hoistway door sections 90. Although the hoistway door sections may be operated by any conventional door operator, preferably the hoistway door sections are operated by the door operator 23 on the elevator car through cooperative vane and drive block members (not shown). Thus, operation of the door operator mounted on the elevator car effects movement of both the car and hoistway door sections in unison.

During a closing operation of the car and hoistway door sections it is desirable to provide object detection means which functions without regard to the position of the closing doors, and to also provide door edge object detecting means which functions when the object bears a predetermined relationship to the door edge. FIG. 1 illustrates a new and improved closure system which provides either or both of these functions with a single source of radiant energy. Further, the door edge detector is provided without resorting to a mechanical edge, which must be retracted at the termination of each door closing operation, and which requires periodic maintenance due to its mechanical nature. Still further, the single source of radiant energy is not mounted on the door or doors of the elevator car, and it additionally may be used to highlight the entry sill of the elevator car.

Specifically, the new and improved closure system employs a sill 92 disposed at the entrance of the elevator car 1, which extends substantially across the width dimension of the entrance. The sill 92 includes a plurality of openings 94 in the entrance portion of the sill, which openings may extend in spaced relation across the entranceway in a single row. As illustrated most clearly in FIG. 3, the openings are preferably formed by drilling counterbored holes, and protective transparent or translucent glass or plastic lens 96 are disposed therein, such as with a suitable adhesive. The protective lens need not be of the focusing type. The sill 92 is disposed to cover a recess or compartment in the forward portion of the floor of the elevator car, immediately adjacent the entrance to the car 1. A source 98 of radiant energy is disposed in this recess or compartment, just below the underside of the sill 92 through which the openings 94 are disposed. This arrangement provides a plurality of vertically oriented beams 100 of radiant energy spaced horizontally across the entranceway to the elevator car. The source 98 is preferably an electric lamp, such as an incandescent resistance lamp, or a mercury vapor lamp, such as a fluorescent lamp. The wavelength of the electromagnetic radiation from source 98 may be selected from a wide range, and may be in the visible or invisible spectrums. Radiant energy visible to the human eye has the added advantage of highlighting the sill, and is thus the preferred embodiment, but infrared or ultraviolet wavelengths may be used if desired.

The first type of object detection which may be provided using the source 98 and plurality of beams 100 of radiant energy is the arrangement, once activated during the door open cycle, which is independent of the position of the door. For this arrangement, one or more detecting devices responsive to the radiant energy used are disposed in the ceiling or transom of the elevator car. For purposes of example, for a 42 inch centeropening door two

detector devices

102 and 104, spaced about 12 inches apart, will provide satisfactory object detection. However, any number of devices may be used. The detection devices should be rendered ineffective just prior to their detecting the door as the door closes, in order to prevent false triggering thereof. When two symmetrically located

detectors

102 and 104 are used, as illustrated in FIG. 1, a single cam 106 and limit switch 108 may be used to render

devices

102 and 104 ineffective at av predetermined point in the door close cycle.

The

detector devices

102 and 104 may be of any type responsive to the wavelength of the radiant energy source. For example, they may be of the photoemissive, photoconductive, or photovoltaic type, as desired. The detecting

devices

102 and 104 may be connected to each control a separate relay having a contact which is closed as long as the detector is receiving radiant energy from source 98. Upon interruption of this radiant energy to a detector, the contact of its associated relay would open to effect some predetermined control action, such as stopping or reversing the doors, as will be hereinafter described relative to the control circuitry shown in FIG. 4.

The single source 98 and perforated sill 92 may also be used to provide object detection relative to the leading edge of a closing door panel, by mounting detector means on the door panel, or panels, adjacent the edge or edges thereof which lead upon closure of the door.

The detector means is spaced from the edge of its associated door panel to provide the desired detection zone, and as illustrated in FIGS. 1 and 3 detector means 110 and 112 are provided for car door sections 5 and A5 which preferably have at least two detector devices, such as detector devices 1 14 and 1 16 which form a part of the detector means 1 l0. Detector device 1 14, which is closest to the leading edge of the door panel 5 upon closure therer-", is adjusted such that a hand placed upon the door will interrupt a beam from the source 98 to the detector, and thus functions in a manner similar to the mechanical safety edge. If the detector device 114 is spaced about one-half inch from the edge of the door, it will satisfactorily perform this function. The second detector 116 is spaced from the door edge by a greater dimension. This dimension is preferably selected to enable the detector 116 to detect an object in the closing path of the door and to stop the car door before striking the object. A dimension of about 3 inches has been found to be satisfactory, but it is not critical. Since the detector means 110 moves with the door, it is important that the number of openings 94, the diameter of the openings, the spacing of the openings and thus the horizontal spacing of the resultant vertically oriented beams 100, and the lens on the detector device, all be selected such that the detector lens will span two adjacent beams 100 to maintain continuous contact with the radiant energy, in the absence of an object interrupting the radiant energy, as the door moves from its open to its close position. One-half inch diameter openings disposed on three-fourths inch centers has been found to be satisfactory but other suitable dimensions may be used.

If desired, a detector 118 responsive to the radiant energy provided by source 98 may be disposed in the recess with source 98. This detector may include a relay having contacts connected to render

detectors

102 and 104 ineffective, and to energize auxiliary radiant

energy transmitter devices

120 and 122, should the source 98 fail to provide radiant energy of a predetermined level.

Transmitter devices

120 and 122 are aimed at detectors means 110 and 112, respectively, to continue door edge object detection until source 98 can be serviced.

Thus, the single source 98, in cooperation with the sill 92, provides a plurality of vertical beams 100 spaced across the entranceway to the elevator car 1, which beams are used to: (1) provide detection of an object in the entranceway without regard to the position of the object relative to the doors, (2) provide detection of an object which contacts or bears a predetermined relationship to the leading edges of the doors upon closure thereof, and (3) highlight the door sill when visible radiant energy is used. The detection of objects is effective for both the car and hatch doors, as it will be noted from FIG. 2 that the beams 100 are located in the space between the car and hatch doors. The door edge protection is achieved without mechanically actuable parts, increasing the useful width of the door opening, and reducing maintenance.

In order to illustrate suitable operation of the door controller 33, a schematic control diagram is shown in FIG. 4 which will operate the closure system shown in FIG. 1. In this diagram, the armature 25A and the field winding 25F of the door operating motor 25 (FIG. 1) are illustrated. Electrical energy for the control circuits is derived from a pair of direct-current buses L+ and L-. The motor field winding 25F is connected directly across the buses L+ and L-. In parallel with the field winding 25F is a rectifier 35 of a conventional type, such as silicon. Current flows through the rectifier 35 in the direction indicated by its circuit symbol in FIG. 4. Thus the rectifier 35 provides a path for induced current as a result of the collapse of the motor field windings magnetic field in the event that power is removed from the buses L+ and L-.

The motor 25 is energized to open or to close the car door by operation of a switch SW. Although this may be a manually operated switch, in a preferred embodiment of the invention this switch represents the contacts of a relay or relays employed in any conventional door operating system to initiate an opening or a closing operation of the door. Thus, movement of the operating member of the switch SW up, as viewed in FIG. 4 to close its contacts SW1 completes, with a limit switch 37 and break contacts CL] of a door closing relay CL, circuit connecting a door opening relay OP across the buses L+ and L- for energization. The limit switch 37 is opened as the door arrives at its fully open position by a cam located in the control assembly 33.

Movement of the operating member of the switch SW down results in closure of its contacts SW2 to complete, with a limit switch 39 and break contacts 0P1 of the door opening relay OP, a circuit connecting the door closing relay CL across the buses L+ and L- for energization. The limit switch 39 is opened as the door arrives at its fully closed position by a cam located in the control assembly 33.

The break contacts CLl prevent energization therethrough of the door opening relay 0? when the door closing relay CL is energized. The break contacts 0P1 operate in a similar manner in the circuit of the door closing relay CL. Associated with the relay OP are make contacts 0P2 and 0P4 and break contacts 0P3. Associated with the relay CL are make contacts CL2 and CIA and break contacts CL3. These contacts control energization of the motor armature 25A, the circuits for energization of the armature being located in the lower portion of FIG. 2.

Associated with the armature 25A are a plurality of adjustable resistors and a plurality of cam-operated control contacts for controlling acceleration and deceleration of the motor 25. These resistors and contacts, together with the contact cams for the latter, are located in the control assembly 33.

It will be noted that the adjustable resistor 41 is disposed in series circuit relationship with the armature 25A in the bus L+. The remainder of the adjustable resistors associated with the armature 25A bear identifying symbols which are indicative of their functions. Thus, the adjustable resistor RAC is employed to effect acceleration of the motor during a door closing operation while the adjustable resistor RAO is employed for accelerating the motor during door opening movement. Similarly, the resistor RDCl is used for decelerating the motor and thereby the door during a door closing movement while the adjustable resistor RDO1 effects deceleration of the motor during door opening movement. Likewise, the cam operated control contacts bear identifying symbols which are indicative of their control functions. For example, the contacts AC and A0 are effective for accelerating the door during door closing and door opening movements, respectively. The contacts DCI through DC4 efi'ect deceleration of the door during door closing movement and operate sequentially in the order of their suffix numerals. The contacts D01 through D04 in sequence similarly control door deceleration during a door opening operation.

Make contacts ASC and A80 are disposed in series circuit relationship with the cam operated contacts DC4 and D04, respectively. These contacts are associated with an anti-stall or checkback relay AS. if a pair of

limit switches

43 and 45 both are in closed condition, the relay AS is connected for energization across the buses L+ and L. In parallel with the coil of the relay AS is resistor-capacitor network comprising serially connected

resistors

47 and 49 and a capacitor 51. In parallel with the resistor 47 is a rectifier 53 of a conventional type such as silicon. Current flows through the rectifier 53 in the direction indicated by its circuit symbol in FIG. 4. Thus, when both of the limit switches 43 and 45 are in closed condition, the capacitor 51 charges through the resistor 49 and the rectifier 53, which, in effect, then shorts the resistor 47. When one of the limit switches 43 or 45 is opened, the capacitor 51 discharges through the

resistors

47 and 49 and the coil of the anti-stall relay AS. Since the length of times of change and discharge of the capacitor are dependent upon the RC network time constant, the rectifier 53 effects a fast charge of the capacitor 51 and a relatively slow discharge thereof.

The limit switches 43 and 45 are located in the control assembly 33 and are operated by cams disposed therein. In a preferred embodiment of the invention, the cam associated with the switch 43 operates to open the switch simultaneously with the opening of the control contacts DC4 by its associated contact cam. The limit switch 45 is opened by its cam simultaneously with the opening of the control contacts D04 by its associated contact cam. Each of these limit switches remains in open condition from the time of its opening to the time when the door reaches the same position in a door movement opposite in direction to that in which the door was moving when the respective limit switch was opened by its associated cam.

A door safety relay DR is connected across buses L+ and L via contacts C102 and C104 of

radiant energy detectors

102 and 104 disposed in the transom of the elevator car 1, contacts C114 and C116 of detector means 110 which is mounted for movement with the door panel 5, and contacts C112 and C1 12' of detector means 112 which is mounted for movement with door panel A5. These serially connected contacts are associated with relays (not shown) responsive to

detectors

102 and 104, and to detector means 110 and 112, and these contacts are closed as long as its associated detector device is receiving radiant energy from source 98. Limit switch 108 is disposed to shunt contacts C102 and C104 when it is in its closed position, to render these contacts ineffective just before the radiant energy received by

detectors

102 and 104 would be interrupted by the closing door panels.

The door safety relay DR includes make contacts DRl and break contacts DR2. These contacts are illustrated in the position they would assume in the event buses L+ and L- are not energized, or rclay DR is deenergized due to one of the contacts in series with the energizing coil of relay DR being open.

Contacts DRl are connected in series with the door close relay CL, and contacts DR2 are connected to shunt contacts SW1 of switch SW. Thus, when relay DR is energized contacts DR] will be closed to enable the door close relay CL to be energized, and contacts DR2 will be open and thus will have no circuit effect. Should radiant energy to one of the detectors be interrupted, relay DR will drop out, contacts DRl will open to deenergize the door close relay CL, and contacts DRZ will close to energize the door open relay OP. Should it not be desirable to reverse the doors, contacts DR2 would not be required.

Relay M is a monitor relay responsive to contact C118 of detector 118 shown in FIG. 1, which detector will maintain contact C118 closed and relay m energized as long as the source 98 provides radiant energy. Relay M includes break contacts M1 and M2. Contacts M] are connected across contacts C102 and C104, and contacts M2 are serially connected across buses L+ and L with transmitter devices and 122, which are also shown in FIG. 1. Should source 98 fail to provide radiant energy of the proper level, contacts M1 will close to render the

detectors

102 and 104 ineffective, and contacts M2 will close to energize

radiant energy transmitters

120 and 122, in order to retain the door edge object detection function.

In summary, there has been disclosed a new and improved closure system, especially suitable for elevator systems, which enables a single source of radiant energy to be used to provide an object detection function, which is independent of the position of the car doors, when the car doors are open or in the process of closing, and an object detection function which bears a predetermined relationship to the leading edge of closing doors. Further, this single source of radiant energy, if selected to have a wavelength which is visible to the human eye, will highlight the sill of the entranceway to the elevator car, adding to the appearance and visibility of the entranceway. While a single incandescent tubular type lamp may be used, which would have a relatively low power consumption and thus long life, it is also practical to use a vapor tube, such as fluorescent tube, which has a very long life and low power consumption. A safety edge function is achieved without mechanical parts and need for retracting mechanism, which reduces maintenance cost, and since a mechanical safety edge is not required, it adds usable space to the entranceway. The object detection function which functions without regard to the position of the car doors, includes a transmitter and detector devices which are permanently mounted on stationary portions of the elevator car. Even the object detection function which bears a predetermined relationship to the closing edge of a car door, only mounts detector devices on the car door, with the transmitter device being mounted on a stationary portion of the car.

While only two detector devices have been illustrated in the transom of the elevator car, a particularly wide opening to an elevator car could be divided into zones by using the required number of detectors in the transom. The detectors, in addition to detecting objects for door modification purposes, could also be used to count passengers, and individual detection zones may be used to effect different door operations. For example, a central zone of a wide opening, upon detecting an object, may stop the car doors, while zones closer to the door edge may stop the car door and reverse its direction. While not shown in the drawings, a timer may be used to time the length of time that the doors are held open in response to the object detection means. At

the end of a predetermined period of time, the door of said beams of radiant energy, said detector protective devices may be overriden and the doors means includingafirst detector device mounted to closed at a slow Speed. move with the door and provide an object detec- We claim as our invention:

tion zone adjacent the leading edge thereof upon 1. eievam' y q comprising: closure, and a second detector device mounted on an elevator f" havmg an entranceway, a stationary portion of the entranceway to provide a door for emfanceway a stationary object detection zone in the entrancemeans mountm g said door for movement to open and way ciose Salci entralicewail' said detector means being responsive to an object ina sill associated with said entranceway, said sill ini terrupting the radiant energy received by either the eluding a portion which extends outwardly past the external side of said door when said door closes first or second detector device, for controlling the said entranceway, with this portion of said sill in- P? of f door d eluding a plural), of spaced openings which auxiliary transmitter means mounted on the car oor tend substantially across the entranceway, and at i dance a source of radiant energy disposed below said Si and means responsive to the failure of the source of providing a plurality of beams of radiant energy f energy, for l 'g 531d auxl llary transwhich extend substantially vertically upward mmel means. (0 Provide a beam 0f ra nt nergy through the plurality of spaced openings in said sill, for the first detector device.

detector means positioned to receive at least certain

Claims

1. An elevator system, comprising: an elevator car having an entranceway, a door for said entranceway, means mounting said door for movement to open and close said entranceway, a sill associated with said entranceway, said sill including a portion which extends outwardly past the external side of said door when said door closes said entranceway, with this portion of said sill including a plurality of spaced openings which extend substantially across the entranceway, a source of radiant energy disposed below said sill providing a plurality of beams of radiant energy which extend substantially vertically upward through the plurality of spaced openings in said sill, detector means positioned to receive at least certain of said beams of radiant energy, said detector means including a first detector device mounted to move with the door and provide an object detection zone adjacent the leading edge thereof upon closure, and a second detector device mounted on a stationary portion of the entranceway to provide a stationary object detection zone in the entranceway, said detector means being responsive to an object interrupting the radiant energy received by either the first or second detector device, for controlling the operation of said door, auxiliary transmitter means mounted on the car door and aimed at the first detector device, and means responsive to the failure of the source of radiant energy, for energizing said auxiliary transmitter means, to provide a beam of radiant energy for the first detector device.