Elevator door restrictor

An elevator is provided with a car and inner and outer doors. The inner door registers with one of the outer doors when the car is disposed within a floor zone. A solenoid on the car has a plunger for blocking the inner door from opening. Power will only be applied to the solenoid to move the plunger to a retracted position to allow the inner door to be fully opened when both the car is disposed within a floor zone and the inner doors are being opened by the main elevator controls. A floor zone sensor is mounted to the car for detecting when the elevator is disposed within one of the floor zones. A door sensor is also mounted to the car for detecting when the inner door is being opened by the main elevator controls. A controller operates the electric solenoid to lift the plunger from the extended position to the retracted position in response to receiving both a door data signal from the door sensor and a floor zone data signal from the floor zone sensor. In the event of a power loss, the plunger will strike a lift clip so that the inner door may close.

FIELD OF THE INVENTION 
The present invention relates in general to controls for elevators, and in 
particular to an elevator door restrictor for preventing elevator doors 
from being opened between floors. 
DESCRIPTION OF THE PRIOR ART 
A new national standard for elevator codes has recently been promulgated by 
the American Society of Mechanical Engineers, and has been widely adopted 
by many local building code authorities. It requires door restrictors for 
blocking the inner doors of elevators from being pushed open more than a 
total of four inches when elevator cars are disposed between floors. The 
code provides a standard that the elevator must be within eighteen inches 
of being perfectly aligned at a floor before the door restrictor allows 
the inner doors to be pushed open. Preferably the inner elevator doors may 
be pushed open a slight distance, not more than a total of four inches, so 
that persons trapped within an elevator car between floors may look out 
into the elevator shaft, call for help and circulate fresh air. Also, in 
the event of a power loss while the door is open, emergency or maintenance 
personnel should be able to manually close the door. 
Prior art elevator door restrictors have been provided by mechanical 
latches which prevent the inner doors of elevator cars from being pushed 
open when the elevator cars are between floors. The prior art mechanical 
latches have mechanical linkages which engage cams located at each floor 
to move the mechanical latches from a latched position to an unlatched 
position when the elevator passes by each floor. These prior art 
mechanical latches do not prevent the inner doors from being pushed open 
while elevator cars are moving past a floor. Additionally, the mechanical 
linkages make noise as the elevator passes each floor. 
SUMMARY OF THE INVENTION 
An elevator is provided with a car, an inner door mounted to the car and 
outer doors mounted to floor openings which define floor zones. The inner 
door registers with the outer doors when the car is disposed within one of 
the floor zones. The elevator includes a door restrictor having an 
electric solenoid mounted to the car so that the inner door cannot be 
opened more than four inches when the elevator is between floor zones. 
The electric solenoid has a plunger which is normally in an extended 
position to block the inner door from opening. Power will only be applied 
to the electric solenoid to lift the plunger from the extended position to 
a retracted position to allow the inner door to be fully opened when both 
the car is disposed within a floor zone and the inner doors are being 
opened by the main elevator controls. A photo sensor is mounted to the car 
to provide a floor zone sensor for detecting when the elevator is disposed 
within one of the floor zones. A photo sensor is mounted to the car to 
provide a door sensor for detecting when the inner door is being opened by 
the main elevator controls. A controller operates the electric solenoid to 
lift the plunger from the extended position to the retracted position in 
response to receiving both a door data signal from the door sensor and a 
floor zone data signal from the floor zone sensor. In the event of a power 
loss, the plunger will strike a lift clip so that the inner door may close 
.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 is perspective view of elevator 11 having car 13 to which inner 
doors 15 are mounted. Car 13 travels between floors at which inner doors 
15 register with outer doors 17. As shown in FIG. 1, inner doors 15 
includes two doors 15a and 15b which open in opposite directions, one to 
the left and the other to the right. The two doors 15 are connected 
together so that one can not be moved without the other moving in an 
opposite direction. Outer doors 17 cover floor openings 19. Floor openings 
19 define floor zones 21, one of which elevator car 13 is shown being 
disposed within. Outer doors 17 are preferably mechanically connected with 
inner doors 15 at each floor so that they will be moved open and closed as 
inner doors 15 are opened and closed. 
FIG. 2 is a side view of elevator 11, taken along line 2--2 of FIG. 1. 
Outer doors 17 are mounted to outer door tracks 23 which extend above 
floor opening 19. Rollers 25 extend into outer door tracks 23 for movably 
supporting outer doors 17. Mounting brackets 27 are used to mount rollers 
25 to outer doors 17. Inner doors 15 are mounted to car 13 by inner door 
track 29. Rollers 31 extend from mounting brackets 33 into inner door 
tracks 29 to movably support inner doors 15. Mounting brackets 33 fasten 
rollers 31 to inner doors 15. A header 63 is mounted to car 13 and 
provides a main support to which inner door track 29 is mounted. 
As shown in FIG. 1, swing arm 35 extends from inner doors 15 to a drive 
motor 37. Drive motor 37 is mounted to header 63. Main elevator control 
39, which is depicted in phantom, is typically located at the top of the 
elevator shaft and is connected to control panel 40, which is mounted 
within car 13 for persons to select the floors to which elevator car 13 is 
moved. Main elevator control 39 controls vertical movement of elevator car 
13 and operation of drive motor 37 to operate swing arm 35 to open inner 
doors 15 and outer doors 17. Wiring trough 41 extends on the top of 
elevator car 13 to provide power to lights which are mounted within car 
13. 
Referring to FIG. 1, elevator door restrictor 42 of the present invention 
includes controller 43, a first photo sensor 45 and a second photo sensor 
49. Photo sensors 45, 49 are commercially available photoelectric sensors. 
First photo sensor 45 is mounted to car 13 to provide a floor zone sensor 
for detecting when one of reflective targets 47 (one shown) is in close 
proximity to sensor 45. Reflective targets 47 are preferably strips of 
tape having an outward facing, reflective surface. In the preferred 
embodiment, reflective targets 47 (one shown) are each 36 inches long and 
mounted to the elevator shaft so that the vertical center of one of the 
reflective targets 47 (one shown) will be detected when car 13 is centered 
within one of floor zones 21. Reflective targets 47 are up to 36 inches 
long so that inner doors 15 may begin to be opened while elevator car 13 
is still moving into position within one of floor zones 21, within 18 
inches of being centered within the floor zone. One of reflective targets 
47 is mounted within each floor zone. 
Second photo sensor 49 provides a door sensor for detecting when reflective 
target 51 has been moved. In FIG. 1, reflective target 51 is shown as 
being mounted to the car side of one of inner doors 15, door 15b. However, 
in other embodiments, reflective target 51 may be mounted to the other 
side of one of inner doors 15, such as on an angle iron mounted facing 
outer doors 17. As shown in FIG. 1, reflective target 51 is preferably 
mounted so that it will not be detected until inner door 15b has been 
opened a short distance, which is preferably not more than two inches. 
Additionally, the opposite end of reflective target 15 should be 
positioned so that second photo sensor 49 will stop detecting the presence 
of reflective target 51 a short distance prior to inner door 15b being 
fully opened. In other embodiments, second photo sensor 49 and reflective 
target 51 may be arranged such that reflective target 51 will only be 
detected both when inner door 15b is fully opened and fully closed. The 
primary purpose for second photo sensor 49 and reflective target 51 is to 
detect when doors 15 are being moved more than two inches toward the open 
position. Doors 15a and 15b are connected together so that one will not 
move without the other being moved. 
Photo sensors 45, 49 are preferably mounted at an angle to reflective 
targets 47, 51, respectively, rather than being mounted to pass light 
along a line of sight which extends directly perpendicular to reflective 
targets 47, 51. The mounting angle between a line which extends 
perpendicular to the flat surface of reflective targets 47, 51 and a line 
of sight along which photo sensors 45, 49 emit light, respectively, should 
be between 10 degrees and 45 degrees. This will help prevent false 
signalling, such as may be occur with shiny surfaces such as stainless 
steel. Additionally, photo sensors 45, 49 should be installed at a minimum 
of 6 inches to a maximum of 6 feet from reflective targets 47, 51, 
respectively. 
Electronic door restrictor 42 of the present invention further includes 
electric solenoid 53 (FIGS. 1 and 2), which acts as a latch. Electric 
solenoid 53 has a plunger 55 (FIG. 2) which provides a blocking member 
which is movable from an extended position to a retracted position. 
Preferably, plunger 55 will be disposed in the lower extended position 
prior to application of power to solenoid 53, and plunger 55 will move up 
to a retracted position after application of power to solenoid 53. 
Electric solenoid 53 is preferably a 12 volt solenoid. 
Referring to FIG. 1, controller 43 controls operation of solenoid 53 in 
response to data signals detected by photo sensors 45, 49. Controller 43 
may be mounted within elevator control panel 40, but preferably is mounted 
within a separate enclosure, as shown in FIG. 1. Controller 43 includes a 
lead acid type of storage battery 69 and a circuit board 71. External 
power is provided by 110 volts AC from wiring trough 41, which is used to 
power the lights inside of elevator car 13. Battery 69 is preferably a 12 
volt DC rated battery, which provides for operation of electronic door 
restrictor 42 when external power is lost. 
Referring to FIGS. 2 and 3, a blocking assembly 57 is mounted to one of 
inner door mounting brackets 33. A blocking plate 59 extends from blocking 
assembly 57 toward outer door 17. A lift clip 60 is mounted to blocking 
plate 59. Lift clip 60 has a surface which extends diagonally downward and 
away from solenoid 53 when inner door 15 is in the closed position (FIG. 
4). Lift clip 60 is a ramp which has a lower edge that is at a lower 
elevation than plunger 55. Although blocking assembly 57 moves 
horizontally with inner door 15 relative to solenoid 53, the vertical 
distance between blocking assembly 57 and solenoid 53 never varies. When 
inner door 15 is in the fully closed position (FIG. 4), plunger 55 is 
horizontally separated from blocking plate 59 by a distance 61. Distance 
61 is preferably not more than two inches when double inner door types are 
used (FIG. 1) wherein the inner doors 15 open in opposite directions. This 
restriction prevents inner doors 15 from being opened more than a total of 
four inches (two inches each) before blocking plate 59 encounters plunger 
55 of electric solenoid 53. If a single inner door 15 is used (FIGS. 4-7), 
then inner door 15 should not move more than four inches before being 
blocked by solenoid 53. This restriction is required to prevent passengers 
from attempting to exit car 13 between floors. 
When car 13 is in a floor zone and inner doors 15 begin to move to the open 
position, power is supplied to solenoid 53. Plunger 55 will recede within 
solenoid 53 (FIG. 6) to permit inner door 15 to move to the opened 
position (to the left). When plunger 55 is recessed, blocking assembly 57 
is unobstructed and inner door 15 is free to move between the open and 
closed positions. In the fully open position, plunger 55 drops back to its 
extended position. When inner door 15 returns from the fully open position 
to the closed position (to the right), power is again supplied to solenoid 
53 to retract plunger 55 until blocking assembly 57 moves to the right 
past solenoid 53 (FIG. 4). At that time solenoid 53 is disengaged and 
gravity drops plunger 55 to its lower position. 
In the event of a power failure, plunger 55 will fall to and remain in its 
lower position. If inner door needs to be closed while plunger 55 is in 
its lower position, plunger 55 will contact blocking assembly 57 (FIG. 7). 
Lift clip 60 will strike the lower end of plunger 55, forcing it to ride 
up the diagonal surface and recede into solenoid 53 so that inner door 15 
may close. This allows inner door 15 to be closed when there is a power 
loss. 
FIGS. 8A and 8B together comprise a schematic diagram depicting circuit 
board 71, showing the control relays mounted to board 71 in their normal 
positions, prior to applying power to actuate the relay coils. Circuit 
board 71 provides a main control for electronic elevator door restrictor 
42 of the present invention. Circuit board 71 has a connector 73 with 
external power terminals 75, 77 which are preferably connected to 110 
volts AC, single phase, found in wiring trough 41 (shown in FIG. 1). A 
positive battery connection 79 and negative battery connection 81 are used 
for connecting circuit board 71 to 12 volt rated battery 69. Ground fuse 
83 is provided for fusing between the negative lead of external battery 69 
and the ground 84 for circuit board 71. 
Terminals 75, 77 connect to transformer 85, which is connected to rectifier 
bridge 87. The rated output of transformer 85 is 16 volts AC, and the 
rated output of rectifier bridge 87 is 18 volts DC. Capacitor 89 is 
provided between the output of bridge 87 and ground 84 of circuit board 
71. Voltage regulator 91 is connected to the output of bridge 87 and 
provides a regulated output voltage of 13.6 volts DC, which provides the 
nominally rated 12 volts DC to power the +12 V nodes of board 71 shown in 
FIGS. 8A and 8B. Capacitors 93, 97, and resistors 98, 99 are connected to 
the voltage regulator 91. 
The output voltage from regulator 91 passes through diode 101 to on/off 
switch 103 and test switch 109. Switch 103 is an on/off switch for 
connecting 12 volt power to node 105, which schematically represents the 
12 volt power supplied to the circuit board. Node 107 is connected 
directly to terminal 79 in connector 73, which is directly connected to 
battery 69. The output from voltage regulator 109 will charge battery 69, 
passing through switch 109 in its normal position. Additionally, if switch 
103 is in the on position (shown in FIG. 8B), and external power fails so 
that it is no longer applied to circuit board 71, battery 69 will pass 
electric current through switches 109 and 103 to node 105 to power circuit 
board 71. If switch 103 is pushed to the off position, power will not be 
supplied to circuit board 71 from either the battery 69 or voltage 
regulator 91. 
Test switch 109, when pushed downward, connects electrical power from 
battery 69 at node 107 to buzzer 111. Buzzer 111 is connected to component 
113 which includes a timing circuit so that buzzer 111 will emit a pulsed 
audible signal. Transistor 115, resistors 117 and capacitors 119 are also 
connected to timing component 113. 
Still referring to FIGS. 8A and 8B, an external power detection relay 121 
is schematically depicted by coil 123, and contacts 125, 127. External 
power detection relay 121 is shown in a normally open position, with power 
not being applied across coil 123. When the output from voltage regulator 
91 is operating at the nominally rated 12 volts DC, power will be applied 
across coil 123 to energize relay 121. Terminals 131, 133 and 135 of 
connector 129 are connected across contact 127 of relay 121. Actuating 
relay 121 will open a normally closed connection across terminals 131 and 
133, of connector 129, and will close a normally open connection across 
terminals 133, 135, of connector 129. 
Terminals 131 and 133, or 133 and 135, are provided for wiring to the door 
open button of the elevator control panel 40 mounted within car 13, which 
is connected to main control panel 39. If external power is no longer 
applied to circuit board 71, such as if a power failure occurs, the 
elevator doors 15, 17 will remain open at the first floor at which the 
elevator stops and the doors open. Since some elevator manufacturers 
require normally open connections to operate the door button and other 
elevator manufacturers require normally closed connections, both types are 
provided by terminals 131, 133 and 135 at connector 129. 
When external 110 voltage AC power is no longer applied to circuit board 
71, contact 125 of relay 121 will move to the normally closed position 
(shown in FIG. 8A) to provide 12 volts DC to operate buzzer 111. The 
battery 69 will then supply 12 volts DC to the +12 volts nodes of circuit 
board 71 to power buzzer 111. Buzzer 111 will then emit the pulsed tone so 
that maintenance personnel may be alerted that there has been a failure of 
external power being applied to the elevator controller, circuit board 71, 
of the elevator door restrictor 42. Diode 139 is connected to coil 123 to 
provide surge protection when the relay 121 is actuated and released. 
Light emitting diode 137 will emit a light signal when external power is 
being applied so that a nominal 12 volt DC is being supplied by the output 
of voltage regulator 91. 
Connector 147 has jumper terminals 149, 151, and 153. In other embodiments 
of the present invention, other types of proximity sensors other than 
photo sensors may be used in place of both photo sensors 45, 49, such as 
magnetic reed switches, microswitches, inductive proximity sensors and the 
like. Connectors 147 are provided for adapting a circuit board 71 for use 
when other types of proximity sensors are being used for a door sensor in 
place of photo sensor 49. When photo sensor 49 is utilized for detecting 
whether inner doors 15 are being moved, a jumper wire is connected across 
terminals 151 and 153 of connector 147. If another type of proximity 
sensor is utilized for a door sensor, other than photo sensor 49, a jumper 
wire is connected between terminals 149 and 151 of connector 147. The 
other types of proximity sensors may still be connected across terminals 
156, 159 of connector 155, with the normally closed contacts of the 
proximity sensors connected to terminals 156, 159 to apply 12 volts DC to 
terminal 159 when not being actuated. These sensors should also be mounted 
to car 13 so that they will actuate when inner doors 15 are fully opened 
and fully closed. 
Photo sensors 45 and 49 (shown in FIG. 1) are connected to circuit board 71 
at connector 155. A plus 12 volt power connection 156 and ground 
connection 157 are provided. The output from photo sensor 45 (shown in 
FIG. 1) is connected to terminal 161. The output from photo sensor 47 
(shown in FIG. 1) is connected to terminal 159 of connector 155, so that 
power will be applied to relay 145 when inner doors 15 are either fully 
opened or fully closed. Photo sensor 45 (shown in FIG. 1) is connected to 
terminal 161 so that terminal 161 will be connected to ground terminal 157 
when a door zone is detected. 
Circuit board 71 includes door zone detection relay 141, door zone output 
signal relay 143 and door limit relay 145. These relays control operation 
of electric solenoid 53 (shown in FIG. 2). When photo sensor 45 detects a 
door zone, terminal 161 will be connected to ground terminal 157, causing 
light emitting diode 163 to be turned on and actuating relays 141, 143. 
Passing power through coil 165 will actuate relay 141, switching contacts 
167, 169 from the normal position (shown in FIG. 8A). Power being applied 
to coil 171 will actuate relay 143, moving contacts 173, 175 from the 
normal position (shown in FIG. 8A). In the normal position, without power 
being applied to relay 145, terminal 185 is connected to terminal 187 of 
connecter 129. When power is applied to actuate relay 145, contacts 173, 
175 are moved from the normal position shown in FIG. 8A, opening the 
electrical connection between terminals 185 and 187 and closing the 
electrical connection between terminals 187 and 189. This provides an 
independent door zone signal, for use with main elevator control circuits, 
such as controls 39 and panel 40 (shown in FIG. 1). Both normally open and 
normally closed sets of terminals are provided, with 187 being a common 
terminal, 185 being a normally closed terminal and 189 being a normally 
open terminal. 
When relay 141 is actuated, by passing current through coil 165 to move 
contacts 167, 169 from the position shown in FIG. 8A, terminal 151 of 
connector 147 will be connected to terminal 181 of connector 129. Terminal 
181 of connector 129 is used for providing power to solenoid 53. A ground 
connection is provided through terminal 183 connector 129. 
When photo sensor 47 is used, a jumper wire is used to connect terminal 151 
to terminal 153 of connector 147. When relay 145 is in the normal 
position, prior to applying power through coil 191, contacts 193, 195 will 
be applying 12 volts DC to terminal 153, which is electrically connected 
to terminal 151 by a jumper wire. This will apply power to terminal 181 
for powering the coil of electric solenoid 53 (shown in FIG. 1). However, 
relay 145 will remain in the actuated position (not shown) until inner 
doors 15 begin to open and reflective strip 51 passes in front of photo 
sensor 49. Terminal 159 is connected to the normally closed contacts of 
photo sensor 49, so that power will not be applied across contacts 193, 
195 until doors 15 begin to open at a particular floor. Prior to photo 
sensor 49 detecting reflective strip 51, contacts 193 and 195 of relay 145 
will be disposed in actuated positions, so that plus 12 volts DC will not 
be connected to terminal 153, but rather terminal 153 will be connected 
across contacts 193, 195 to an open circuit. Thus, inner doors 51 will 
remain latched until car 13 stops at a floor and doors 15 begin to open. 
This prevents solenoid 53 from being actuated at every floor car 13 moves 
past. Rather, solenoid 53 will only actuate as inner doors 15 are being 
opened, thereby extending the service life of solenoid 53. When photo 
sensor 49 detects reflective strip 51, relay 145 returns to the normal 
state, without current passing through coil 191, moving contacts 193, 195 
to the normal position shown in FIG. 8A. This connects 12 volts DC to 
terminal 153 of connector 147, and to terminals 167, 169 of relay 141. 
Light emitting diode 197 is provided to indicate when relay 145 is 
actuated. Diode 199 is a surge suppression diode for coil 191. External 
LED connectors 201, 203 are provide to indicate when 12 volts power is 
applied to circuit board 71. An LED, or other output indicator when 
connected across terminals 201, 203 will be powered when either external 
power or battery power is applied to circuit board 71. on board LED 205 
also provides an indication of whether either battery power or external 
power is applied to circuit board 71. Capacitor 207 is provided for 
connecting between the +12 volt nodes and ground nodes of circuit board 
71. 
Operation of the present invention is now described. When car 13 enters 
within one of floor zones 21 (FIG. 1), photo sensor 45 will detect 
reflective strip 47. This sends a floor zone data signal to controller 43, 
as discussed above in the discussion for circuit board 71. The floor zone 
data signal is provided by connecting terminal 161 of connector 155 to 
ground terminal 157 to actuate relays 141, 143. When car 13 is stopping at 
one of the floors, within one of floor zones 21, inner doors 15 will be 
mechanically coupled to outer doors 17 and doors 15, 17 will begin to open 
in response to the main elevator control. This moves reflective strip 51 
in front of photo sensor 49. When photo sensor 49 detects strip 51, it 
then sends a door data signal to controller 43. The door data signal from 
photo sensor 49 is provided by removing terminal 159 of connector 155 from 
connecting to ground terminal 157 to remove power across coil 191 and move 
relay 145 to a normal state (shown in FIG. 8A). 
When both the door data signal is emitted from photo sensor 49 and the 
floor zone data signal is emitted from photo sensor 45, then controller 43 
will actuate solenoid 53 to pull plunger 55 upwards and out of the path of 
blocking member 59 so that doors 15 may be fully opened (FIG. 6). When 
inner doors 15 are almost fully open, reflective strip 51 will pass from 
in front of photo sensor 49, so that photo sensor 49 no longer passes the 
door data signal. This causes power to be taken off of solenoid 53, and 
plunger 55 falls from the retracted position back into the extended 
position. This will extend the service life of solenoid 53 by not 
continuously applying power as inner doors 15 are held open. For example, 
cleaning crews may frequently leave elevator doors 15, 17 open while they 
are cleaning a floor, taking elevator 11 out of service. 
Once inner doors 15 begin to close again, reflective strip 51 will again 
move in front of photo sensor 49, and is detected by photo sensor 49, 
which then emits the door data signal. With car 13 still in position 
within one of floor zones 21, photo sensor 45 will still be detecting 
reflective strip 47. With both the floor zone and door data signals being 
emitted, solenoid 53 will again be actuated to move plunger 55 from the 
extended position into the retracted position, allowing blocking member 59 
to pass underneath solenoid 53, and doors 15 to fully close. When doors 15 
are fully closed, power is removed from solenoid 53 and plunger 55 drops 
downward to block doors 15 from being fully opened (FIG. 4). Then elevator 
car 13 may be moved to a new floor, at which the door opening sequence may 
begin again. 
If elevator door restrictor 42 fails, then solenoid 53 will remain in the 
extended position, latching elevator inner doors 15 fully closed so that 
they cannot be opened more than four inches (FIG. 5). Also, when switch 
103 (shown in FIG. 8B) is moved to the off position so that voltage is no 
longer applied to node 105, from either the external power supply of 
wiring trough 41 or battery 69 (shown in FIG. 1), plunger 55 will remain 
in the extended position so that blocking member 59 cannot pass beneath 
solenoid 53 and inner doors 15 cannot be opened more than four inches. A 
maintenance technician will have to physically remove plunger 55 or 
solenoid 53 from blocking inner doors 15 from opening more than four 
inches, or return switch 103 to the on position. If inner doors 15 open at 
a floor and the power is off, lift clip 60 allows inner doors 15 to be 
closed. 
The present invention provides several advantages over prior art elevator 
door restrictors. An electronically controlled relay is provided for 
preventing the inner doors of the elevator car from being unlatched as the 
elevator is passing through each floor. This feature provides safer 
operation since the inner doors can not be pushed open as the elevator car 
is moving through a floor zone. This feature also provides quieter 
operation than mechanical latching mechanisms which are unlatched at each 
floor. Additionally, if a power failure occurs, a door open signal is 
provided once the car reaches a floor so that the elevator doors will be 
opened and remain open. A buzzer will sound a pulsed, intermittent, 
audible signal so that persons in the elevator car will evacuate the 
elevator and notify a service technician to repair the system. In 
addition, an independent floor zone signal is provided which may be used 
with the main elevator controls. Finally, the lift clip provided with the 
invention allows the inner doors to be closed at any time, even if the 
power to the elevator is off. 
Although the invention has been described with reference to a specific 
embodiment, this description is not meant to be construed in a limiting 
sense. Various modifications of the disclosed embodiment as well as 
alternative embodiments of the invention will become apparent to persons 
skilled in the art upon reference to the description of the invention. It 
is therefore contemplated that the appended claims will cover any such 
modifications or embodiments that fall within the true scope of the 
invention.