CA2066613A1

CA2066613A1 - Obstruction detection apparatus

Info

Publication number: CA2066613A1
Application number: CA 2066613
Authority: CA
Inventors: John Trett
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-10-13
Filing date: 1990-10-09
Publication date: 1991-04-14
Also published as: JPH05501304A; GB2238379A; AU6614290A; GB8923141D0; EP0494976A1; WO1991006018A1

Abstract

2066613 9106018 PCTABS00005 An obstruction detection apparatus for use on a movable door, for example, comprises an array of transmitter/receiver pairs (4), each pair comprising a transmitter and receiver in proximity and sharing substantially a common field of view, respective pairs being mounted in spaced apart relationship (d) along the leading edge of a door; a reflection means (6) mounted, adjacent the surface upon which the door closes to lie, within at least part of the field of view (R) of each transmitter/receiver pair, the reflection means having a substantially higher reflection coefficient than any other surface which normally lies within said field of view;
and means (20) for detecting a reduction in the signal received by one or more receivers to indicate the presence of an object (7) interposing the door and the reflection means. Furthermore, if the reflection means (6) lies within only a part of the field of view then an increase in the signal received can indicate the entry of an object in the part of the field of view other than that in which the reflection means lies. Thus, two zones can be independently monitored.

Description

W091/06018 ~ 3 PCT/GB90/01549 ..
:., -- 1 _ OBSTRUCTIO~ DETECTION APPARATUS
. __ This invention relates to obstruction ~` detection apparatus and in particular it relates to apparatus for the detection of obstructions in the path of moving bodies such as moving doors on lifts (elevators) or trains.
Such doors arG often controlled automatically and should be able to detec~, the presence of an obstruction such as a boà~ ir. their path and cease their motion. It is imporuant with a lift door to ensure that the door closes ~eforc the lift is raised or lowered, but also to ersure that - the door does not hlt or even frighten a ?assenger when closing. I~ is also useful tha~ a~ leas~, two 1, independent protection devices are inc'uded i.^ the door mechanism, both of which fail to safet~J. .e.
with the doors open. mypically one mecha~ism may use light beams whilst the other monitors the tor~ue on the door.
It is preferable to monito.r two aif~Qrer.t zones of the doorway area, as shown in ~igure a.
- Zone A i`s a thin zone across the opening and following tha door closing path. An o'cs~ruct cn to this path causes the doors to be 'hel ' so tha~ a person can enter o. leave the lift. ~on? ~ is immediatel~ in front of the door and is broade- than zone A. It extends for a distance greater tr.an ~he , stopping distance of the door and prevents the door from hitting a person going through the entrance.
- 30 According to the present invention there is ' provided an obstruction detection apparatus comprising a transmitter and a receiver mounted on one side of a zone to be monitored and having substantially a commor. ~ield of view ar.d a re~lector mounted on the other side of the zone and arranged to ...... .............. ............ ~ ~, . . .
- .

W091/060t8 PCT/GB90/01549 6~L3 ,~, ; lie within at least a part of the said field of view to reflect a signal from the transmitter back to the receiver, said reflector being endowed with a reflectivity substantially highe- than any other body at which the transmitter is normally directed. and means for detecting a reduction in the signal received by the receiver to ind cate the presence of an object interposing the path from the transmitter ~ to the receiver via the rerlector.
Preferably, the reflector lies within only a part of the ield of view and the apparatus includes means for detec~ing an incraase in the signal received by the receiver. whlch increase is indicative of the entry of an object re'~ive'y close to the receive. and in the portion of the field o~
view other 'han that in which the reflecto. lies.
According to the present invention there is - further provided movable door apparatus comprising an array of transmi~ter/receiver pairs, each pair comprising a transmitter and receiver in pro~imity and sharing substantially a common field of view, respective pairs being mounted in spaced apart relationship along the leading edge of a door a re~lection means mounted, ~djacent the surface upon which the door closes to lie, within at leas~ part of ; the field of view o4 each ~.ansmitter/receiver pair, tne reflection means having a substantially higher reflection coefficient than any other surface which normally lies within said field of view and means : 30 for detecting a reduction in the signal received by one or more receivers to indicate the presence of an object interposing the door and the re41ection means.
Preferably, the reflection means lies within only a part o~ the field of view and means are , :.

. . . . . . .

2 ~ fi ~ 613 PCT/GB90/01549

- 3 _ -provided for detecting an increase in the signal received by one or more receivers to indicate the entry of an object in the part of the field of view other than that in which the reflection means lies.
The respective transmitter/receiver pairs -~
may be actuated and monitored in turn by multiplexing.
Preferably, the reflector or reflection means is a retroreflecto- but any other r-flector, such as a plane mi,ror, may be used provided care is taken to avoid unwanted reflections reaching tne receiver. Advantageously the retroreflector is in the form of a screen of spherica' be~ds or appropriately faceted bodies.
Advantageously, the ~ield of vle~ of ~r- o-each pair is arranged so that a greate. portion of iv lies on a chosen side of the doorwa~.
Fmbodiments of the invention wi l now be described, by way of example only, with reference to the accompanying diagr~mmatic drawings, in which:
~igure 1 shows a plan view o~ a schematic lift door apparatus:
?igure 2 shows a front view of tne door apparatus:
Figure 3 shows a plan view of a further embodiment of the presen' invention: and ~igure a shows the zones in a doorway which it is desirable to monitor.
Refer.ing to Figures 1 and 2 a lift door I
is mounted adJacent a lift frame 2. Further doors 3 are provided at each landing and, in use, both a respective landing door 3 and the lift door 1 must be open before a passenger can enter or leave the lif~.
Mounted in vertically spaced apart relationship on the door are a plurality of transmitter/receiver . .

.
:: .
`:

. i ~ . .

~6~ 4 pairs 4. These may be of any suitable type such as infra-red, ultra-sonic, etc., but are arranged such ; that each transmitter and receiver are proximate or - integrated in one unit and share substantially a common field of view ~. The transmitter and receiver are therefore not focussed. On the other side o~ the door in ~igures 1 and 2 a fixed slam post 5 is shown.
Alterna~ively, this could be another door for a system which uses two doors in a bi-parting system.
Vertically mounted on the sla~ post 5 is a long thin ret.oreflective strip 6 approximately paralle' to the edge of door 1. ~his may com?rise for e~ample a plurality of corner cubes or could have a coa~ing of retroreflective paint, of the type commonl~ used for road signs. An~ other type Or retroreflective medium may be applied, for example a screen with tr~nslucen~ spherica beads embedded to orm an outer edge. Alterna~ively, a reflector such as a plane mirror may be used. It is desirable that the re~lector or retroreflector be a substan~ially better reflector than any other surface in the surrounding area. The retrore~lector has the effect of reflecting any radiation back in the direction ~rom which il came. Thus, substan~ial'y all radiation e~i~ted in the plan (horizontal) angular region R of ~igure 1 is reflected back onto itself and hence onto the receiver par~ of transmitter/
; receiver 4. Similarly, any radiation in the vertical angular region S for transmitter/receiver 4a of ~igure 2 is re lected back onto itself. When an obstruction such as a hand 7 is placed within the zone between t-ansmitter/receiver a and ret~oreflector 6, less radiation is reflected back.
Accordingly, the signal re^eived a~ t.ansmitter/
receiver 4 is reduced. ~his reduction in signal can WO91/06018 PCT/GBsO/01549 2Q6~613, be detected by standard and known techniques such as ` thresholding or by using comparators or delays for example, and used to provide a signal to instruct the door either not to close or, if it is already closing, to sto~ closing and o?en. Hence any obstruction in the direct closing path of the door will immediately inhibit closure of the door.
A thresholding unit 20 is shown in ~ig.l, which unit receives a signa' from the tr~nsmitter/
receiver pair 4 and, if the signal is less than ~
predetermined threshold and/or greater than a second predetermined threshold ! outputs a contro' si~na' ~o inhibit closure, or begin opening the door, ~s appropriate. Such uni~s are we'l ~nown. OthP- sig-.a' dPtecting a?paratuses may, of course. be used.
~he transmitte./receiver pairs ~ ar= spa^Pd by a distance d down the side o door ,.
Advantageously, this distance is around 50 mm which , i3 approximately the diamete. of a child's wrist so that any part of a body will normal'y al~ays be in the field of vision if that body strays within the closing path of the door. The transmitte./receiver ai-s are unfocussed and, as showr. in ~i~ure ~.
ove-la? each other. Hence if an object is placed in f.ont of the retroreflector 6 i~ will usually cause a reduction in the signals received by a+ leas' two receivers ~. A hand placed at posi~ion 7b in ~igure 2 will cause a reduction in part o~ the signa' from transmitter/ receiver 4a and also in part of the signal from transmitte.!receiver 4b directly above 4a. By measuring the output of each receiver in each respective transmitter/receiver pair 4 and noting the relative changes between them, the position of an obstruction can be detected to a high deg-Pe o accuracy. ~or instance, if the si~nal a~ receiver 4a ,, ~ . , : .
, ': ' WO 91/OfiO18 PCI/CB90/01549 ~,QC~6~3 - 6 -is reduced by half, and that at receiver ~b by one quarter, then the object must be between 4a and 4b, but nearer 4a.
The transmitter/receiver pairs 4 may preferably be activated in turn, i.e. multi~lexed, and the received signals compared with each other.
This is especially desirable if reflectors other than retroreflectors are used, to prevent unwanted radiation being received.
Although the retroreflective strip i3 shown - mounted on a slam post i~ may alternativel~ be ~rovided on the edge o~ a door in a bi-~a-+ing system.
Any radia+ior. from tr~nsmitters 4 which falls outside the zon~ defined ~y th- ret.orQ~lQcvi~
strip ~ will be either rerlected away by the s~rface upon which i~ eventually falls or, more typically, absorbed or greatly attenuated. Thus, if an object is placed within this region outside the zone defined ~-by strip 5, the object will, if it is close enough to the transmitter/receiver pair, reflect radiation back and will have the effect of increasing the signal received. Accordingl~, in a zone close to tne ; transmitter/reCeivQr pair and determined b~ the powe-o the system and the reflec~ivity o~ any obstruction, the monitored field of view is wider than that further ~rom the pair and an obstruction will make its presence felt by an increase in the signal. Hence, the system according to the invention automatically monitors two di~ferent zones simultaneously but independently, avoiding the need 40r two or more different types of sensor. The zones can correspond to desired zones A and ~ in ~igure ~.
~his bi-æone monitoring is des rabie because the closing o, a door may be alarming to a passenge-, :

" ....

WO91/06018 PCT/~B90/01549 _ 7 _ 2~6~3 particularly if it is a very young or very old passenger who is close to the door, but not directly in its closing path.
If a li4t is to be used during busy periods it will often be ~illed to capacity. In such cases it will usually be necessary for one or more persons to stand very close to the edge in a corner o3 the li t. It is undesirable in such circumstances for the obstruction sensing apparatus to sense such a person. ~igure 3 shows an embodiment of the invention in which such detection is avoided by rotating the field of view of the t.ansmitter/
receiver pairs about a ver+ical axis such thav the central plane o3 the fle'd of vie~ is a' an angle O
to the closing directior. of the door. mhe angle ^ is such that the area of devection in which an increase in signal occurs when an object is placed in tne field of vie~ is just in front of the car door 1 and landing door 3. The transmitter/ receiver pairs are still able to "see" the slam post or second door 5 ?
and hence the retroreflector, and to detect a reduction in signal indicative of an obstruction in tne direct closing path. If an objec+ to be detected enters the detection zone outside that de~.ned by retroflective strip ~ then an increase in signal is seen.
A reference transmitter/receiver pair may - preferably be provided outside the detection zone to ac+ as a comparison reference for the remaining pairs. Alternavively, a re~erence signal can be generated by averaging a'l the received signals.
The present invention avoids the need for careful focusing of transmitter/receiver pairs since all the pairs are unfocused and have a conical volume o vision directed at a ?ar~icular angle. In some ,~

.. .. . . .
.. . ..
-~ ,:

WO91/06018 ~9j PCTJGB90/01549 applications it is possible to restrict the angle of vision. This may be achieved by using partially focused transmitters and receivers or by the use of shutters for restricting the angle of vision.
Since only a passive retroreflector is required on the right side of the door in the ~igures considerable cos' savings are achieved since active circuits need only be provided on one side of the door opening. ~hus wires linking the two sides of the opening are obviated and a reduction in power supply consumption is achieved.
It is further preferable tha~ the retroreflector ~ is housed in an identical enclosure to the transmitte./recelve. circuits. These cir^uits are often housed in an elongate channe' shaped member which extends down the length o~ the door. By also mounting the retrore~lective means in a similar member, cost is greatly reduced and the appearance of ,; the system improved. A guarding channel-shaped member also serves to protect both the transmitter/
receiver pairs and the retroreflective means.
The invention is also applicable in control or monitoring systems, or with robots, machine guards and other applications related to conveying or material handling. The invention can also be used in intruder detection systems.

, ,,,~ ,.
.. . : .......... : ', i. : . ~ ,:
~, . . .

Claims

1. An obstruction detection apparatus comprising a transmitter and a receiver mounted on one side of a zone to be monitored and having substantially a common field of view and a reflector mounted on the other side of the zone and arranged to lie within at least a part of the said field of view to reflect a signal from the transmitter back to the receiver, said reflector being endowed with a reflectivity substantially higher than any other body at which the transmitter is normally directed, and means for detecting a reduction in the signal received by the receiver to indicate the presence of an object interposing the path from the transmitter to the receiver via the reflector.

2. An obstruction detector as claimed in claim 1 wherein the reflector lies within only a part of the field of view and means are provided for detecting an increase in the signal received by the receiver, which increase is indicative of the entry of an object relatively close to the receiver and in the portion of the field of view other than that in which the reflector lies.

3. An obstruction detector as claimed in claim 1 or claim 2 including a plurality of spaced-apart transmitter/receiver pairs.

4. An obstruction detector as claimed in claim 3 including means for comparing the signals received by each of the receivers.

5. An obstruction detector as claimed in claim a including means for using the compared signals to detect the approximate position of an obstruction.

6. An obstruction detector as claimed in any preceding claim wherein the reflector is a retroreflector.

7. Movable door apparatus comprising an array of transmitter/receiver pairs, each pair comprising a transmitter and receiver in proximity and sharing substantially a common field of view, respective pairs being mounted in spaced apart relationship along the leading edge of a door a reflection means mounted, adjacent the surface upon which the door closes to lie, within at least part of the field of view of each transmitter/receiver pair, the reflection means having a substantially higher reflection coefficient than any other surface which normally lies within said field of view and means for detecting a reduction in the signal received by one or more receivers to indicate the presence of an object interposing the door and the reflection means.

8. A movable door apparatus as claimed in claim 7 wherein the reflection means lies within only a part of the field of view and means are provided for detecting an increase in the signal received by one or more receivers to indicate the entry of an object in the part of the field of view other than that in which the reflection means lies.

9. A movable door apparatus as claimed in claim 7 or claim 8 wherein the respective transmitter/receiver pairs may be actuated and monitored in turn by multiplexing.

10. A movable door apparatus as claimed in any of claims 7 to 9 including means for comparing the signals received by each of the receivers.

11. A movable door apparatus as claimed in claim 10 including means for using the compared signals to detect the approximate position of the object.

12. A movable door apparatus as claimed in any of claims 7 to 11 wherein the reflector means is retroreflective.

13. A movable door apparatus as claimed in any of claims 7 to 12 wherein the field of view of one or more pairs is arranged so that a greater portion of it lies on a chosen side of the doorway.