U.S. patent number RE30,719 [Application Number 05/930,656] was granted by the patent office on 1981-08-25 for doorway safety device.
Invention is credited to Gerald W. Mills.
United States Patent |
RE30,719 |
Mills |
August 25, 1981 |
Doorway safety device
Abstract
A safety system for automatically operated sliding panel doors,
specifically elevator doors, having acoustic wave transmitters and
receivers arranged in a row along the moving door's leading edge.
Short bursts of acoustic energy are projected both in front of the
door and to one or both sides so as to "sweep" a three-dimensional
space, in and near the door's path, representing a zone of
potential danger to persons or objects therein. Reflected energy
from persons or objects in the danger zone is usable if it is
received, following each transmitted burst, during a prescribed
time interval representing combinations of the doorway opening
distance and other selected parameters, and usable reflections are
converted to a control signal to stop and re-open the doors before
they strike the endangered person or object.
Inventors: |
Mills; Gerald W. (Ramsey,
NJ) |
Family
ID: |
25459581 |
Appl.
No.: |
05/930,656 |
Filed: |
August 2, 1978 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
619731 |
Oct 6, 1975 |
04029176 |
Jun 14, 1977 |
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Current U.S.
Class: |
187/317; 187/319;
367/96; 49/25 |
Current CPC
Class: |
B66B
13/26 (20130101); E05F 15/70 (20150115); E05Y
2900/104 (20130101) |
Current International
Class: |
B66B
13/26 (20060101); B66B 13/24 (20060101); E05F
15/20 (20060101); B66B 013/26 () |
Field of
Search: |
;187/1R,48,51,52R,52LC,56,58,DIG.1 ;49/25,26,27,28 ;340/545
;367/93,96 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rowland; James L.
Attorney, Agent or Firm: Larson and Taylor
Claims
What I claim is:
1. In an elevator system, a structure including a hoistway having
one or more landings, a hoistway door for each landing, an elevator
car arranged for movement in said hoistway from one to another of
said landings, said car having a door movable from an open position
to a closed position against a strikepost, means for opening and
closing said car door, mechanical means for coupling said hoistway
door to said car door so that both doors move concurrently from an
open position to a closed position or vice versa, the improvement
which comprises electrical means for sensing and being responsive
to objects in a predetermined zone at any position of the car door,
whereby upon detecting an object in said zone said opening and
closing means is energized to prevent further closure of said car
door, said sensing means including transmitting and receiving means
for locating a leading edge of the car door relative to the strike
post, and second transmitting and receiving means positioned at a
predetermined angle on the leading edge of the car door in
cooperation with said locating means for detecting objects at an
angle with respect to an outside surface of the car door during
movement of the car door.
2. In an elevator system according to claim 1, including third
transmitting and receiving means in cooperation with said
.[.distance measuring.]. .Iadd.locating .Iaddend.means and said
object detecting means for detecting objects substantially in
direct line of movement of the car door.
3. In an elevator system according to claim 2, wherein all of said
transmitting and receiving means are carried by said car door, each
of said transmitting and receiving means constituting at least a
single pair and each of said pairs being spaced along a leading
edge of said car door.
4. In an elevator system according to claim 2, wherein all of said
transmitting and receiving means are carried by said strike post,
each of said transmitting and receiving means constituting at least
a single pair and each of said pairs being spaced along a meeting
edge with said car door.
5. In an elevator system according to claim 2, wherein said car
door and strike post are constituted by two panels moving toward
each other to a closed position and away from each other to an open
position, wherein all of said transmitting and receiving means are
carried by one of said panels, wherein the other of said panels
carries a reflecting element, each of said transmitting and
receiving means constituting at least a single pair and each of
said pairs being spaced along a meeting edge of said one panel.
6. In an elevator system according to claim .[.3.].
.Iadd.1.Iaddend., including means for providing each of said
transmitting means with acoustic wave energy, and means for each of
said receiving means for receiving reflection of said transmitted
acoustic energy.
7. In an elevator system according to claim 6, wherein said
acoustic wave energy is constituted by a series of short bursts of
acoustic wave pulses of a single predetermined frequency with
comparatively large time gaps between bursts.
8. In an elevator system according to claim 7, wherein said wave
energy of said second transmitting means travels along a diverging
pattern. .[.9. In an elevator system according to claim 7,
including means for establishing said time gap between bursts
provided by said first transmitting means..].
0. In an elevator system according to claim .[.9,.]. .Iadd.7,
including means for establishing as a timing signal said time gap
between bursts provided to said first transmitting means; and
.Iaddend.including means for rendering said second transmitting and
receiving means effective upon detection of an object in its path
in preventing closure of said car door when signal received from
said preceding object occurs before expiration
of said time gap and said timing signal. 11. In an elevator system
according to claim 10, including means for varying said
predetermined zone
for operation of said second transmitting and receiving means. 12.
In an elevator system accordng to claim .[.9,.]. .Iadd.7, including
means for establishing as a timing signal said time gap between
bursts provided to said first transmitting means; and
.Iaddend.including means for rendering said third transmitting and
receiving means effective upon detection of an object in its path
in preventing closure of said car door when signal from said
preceding object occurs before expiration of said time gap of
said
timing signal. 13. In an elevator system according to claim 12,
including means for varying said predetermined zone for operation
of said third
transmitting and receiving means. 14. The method of detecting
presence of an object positioned in the path of an elevator door
which comprises the steps of transmitting short bursts of acoustic
wave energy from a leading edge of a moving car door towards a
strike post and receiving reflections of said acoustic energy from
said strike post or said object in said door path, the first step
of which consists in transmitting and receiving said acoustic
energy in a straight path as a timing signal, that is, the time
taken for passage of the energy from the car door to the strike
post and then back to the car door, the second step of which
consists in transmitting and receiving said acoustic energy in a
straight path for detection of an object in its path, and the third
step of which consists in transmitting and receiving said acoustic
energy at an angle with respect to line of movement of the car door
for detection of an object in its angular path, whereby should the
reflected acoustic energy of either the second step or third step
be received prior to the duration of the timing signal of the first
step, as indicative of detection of an object, the moving car door
will be stopped and returned to its fully open position in
accordance with accepted elevator practice. .Iadd. 15. A safety
system for preventing the full closure of an automatically operated
sliding door, the door being movable from an open position to a
closed position against a strike post and having a leading edge,
said safety system comprising:
electrical means for sensing and being responsive to objects in a
predetermined zone at any position of the door, whereby upon
detecting an object in said zone said electrical means generates a
signal for preventing further closure of the door, said electrical
means comprising:
locating means for locating a leading edge of the door relative to
the strike post; and
first transmitting and receiving means positioned at a
predetermined angle on the leading edge of the door in cooperation
with said locating means for detecting objects in said
predetermined zone. .Iaddend..Iadd. 16. A safety system as claimed
in claim 15, wherein said predetermined angle is an angle measured
between the object and an outside surface of the car door during
movement of the car door, said angle being substantially greater
than zero. .Iaddend..Iadd. 17. A safety system as claimed in claim
16 and further including a second transmitting and receiving means
in cooperation with said locating means; and wherein said second
transmitting and receiving means is for detecting objects
substantially in direct line of movement of the door.
.Iaddend..Iadd. 18. A safety system as claimed in claim 15,
including means for providing each of said transmitting means with
acoustic wave energy that is constituted by a series of short
bursts of acoustic wave pulses with comparatively large time gaps
between bursts, and means for each of said receiving means for
receiving reflection of said transmitted acoustic energy.
.Iaddend..Iadd. 19. A safety system as claimed in claim 18, wherein
said wave energy of said first transmitting means travels along a
diverging pattern. .Iaddend..Iadd. 20. A safety system as claimed
in claim 18 and further including means for rendering said first
transmitting and receiving means effective upon detection of an
object in its path in preventing closure of the door only when the
signal received from that object occurs before expiration of a time
interval determined by said locating means such that said time
interval is the time necessary for said acoustical energy to travel
twice the distance between said door leading edge and said strike
post. .Iaddend..Iadd. 21. A safety system as claimed in claim 20
and further including means for varying said predetermined zone for
operation of said first transmitting and receiving means.
.Iaddend..Iadd. 22. A safety system as claimed in claim 21 wherein
said predetermined angle is an angle measured between the object
and an outside surface of the car door during movement of the car
door, said angle being substantially greater than zero;
and further including a second transmitting and receiving means in
cooperation with said locating means; and wherein said second
transmitting and receiving means is for detecting objects
substantially in direct line of movement of the door, said
rendering means also rendering said second transmitting and
receiving means effective when the signal received thereby from a
detected object occurs before expiration of said time interval.
.Iaddend..Iadd. 23. A safety system as claimed in claim 15 wherein
said predetermined angle is determined such that said first
transmitting and receiving means detects objects substantially in
direct line of movement of the door. .Iaddend..Iadd. 24. A safety
system as claimed in claim 15 wherein said locating means includes
a further transmitting and receiving means. .Iaddend. .Iadd. 25. In
an elevator system, a structure including a hoistway having one or
more landings, a hoistway door for each landing, an elevator car
arranged for movement in said hoistway from one to another of said
landings, said car having a door movable from an open position to a
closed position against a strike post, means for opening and
closing said car door, mechanical means for coupling said hoistway
door to said car door so that both doors move concurrently from an
open position to a closed position or vice versa, the improvement
which comprises electrical means for sensing and being responsive
to objects in a predetermined zone at any position of the car door,
whereby upon detecting an object in said zone said opening and
closing means is energized to prevent further closure of said car
door, said sensing means comprising locating means for locating a
leading edge of the door relative to the strike post; and first
transmitting and receiving means positioned at a predetermined
angle in the leading edge of the car door in cooperation with said
locating means for detecting objects in said predetermined zone.
.Iaddend..Iadd. 26. In an elevator system as claimed in claim 25
wherein said locating means is for detecting objects at an angle
substantially greater than zero with respect to an outside surface
of the car door during movement of the car door. .Iaddend..Iadd.
27. In an elevator system as claimed in claim 26 and further
including a second transmitting and receiving means in cooperation
with said locating means; and wherein said second transmitting and
receiving means is for detecting objects substantially in direct
line of movement of the door. .Iaddend..Iadd. 28. In an elevator
system as claimed in claim 26 and further including means for
providing each of said transmitting means with acoustic wave energy
that is constituted by a series of short bursts of acoustic wave
pulses with comparatively large time gaps between bursts, and means
for each of said receiving means for receiving reflection of said
transmitted acoustic energy. .Iaddend..Iadd. 29. In an elevator
system as claimed in claim 28 and further including means for
rendering said first transmitting and receiving means effective
upon detection of an object in its path in preventing closure of
the door only when the signal received from that object occurs
before expiration of a time interval determined by said locating
means such that said time interval is the time necessary for said
acoustical energy to travel twice the distance between said door
leading edge and said strike post. .Iaddend..Iadd. 30. In an
elevator system as claimed in claim 29 and further including means
for varying said predetermined zone for operation of said first
transmitting and receiving means. .Iaddend..Iadd. 31. In an
elevator system as claimed in claim 30 and further including a
second transmitting and receiving means in cooperation with said
locating means; and wherein said second transmitting and receiving
means is for detecting objects substantially in direct line of
movement of the door, said rendering means also rendering said
second transmitting and receiving means effective when the signal
received thereby from a detected object occurs before expiration of
said time interval. .Iaddend..Iadd. 32. In an elevator system as
claimed in claim 25 wherein said predetermined angle is determined
such that said first transmitting and receiving means detects
objects substantially in direct line of movement of the door.
.Iaddend..Iadd. 33. In an elevator system as claimed in claim 32
and further including means for providing each of said transmitting
means with acoustic wave energy that is constituted by a series of
short bursts of acoustic wave pulses with comparatively large time
gaps between bursts, and means for each of said receiving means for
receiving reflection of said transmitted acoustic energy.
.Iaddend..Iadd. 34. In an elevator system as claimed in claim 33
and further including means for rendering said first transmitting
and receiving means effective upon detection of an object in its
path in preventing closure of the door only when the signal
received from that object occurs before expiration of a time
interval determined by said locating means such that said time
interval is the time necessary for said acoustical energy to travel
twice the distance between said door leading edge and said strike
post. .Iaddend..Iadd. 35. In an elevator system as claimed in claim
34 and further including means for varying said predetermined zone
for operation of said first transmitting and receiving means.
.Iaddend..Iadd. 36. A safety system for preventing the full closure
of an automatically operated sliding door, the door being movable
from an open position to a closed position against a strike post
and having a leading edge, said safety system comprising:
electrical means for sensing and being responsive to objects in a
predetermined zone at any position of the door, whereby upon
detecting an object in said zone said electrical means generates a
signal for preventing further closure of the door, said sensing
means including
first transmitting and receiving means for locating a leading edge
of the door relative to the strike post; and
second transmitting and receiving means positioned at a
predetermined angle on the leading edge of the door in cooperation
with said locating means for detecting objects at an angle
substantially greater than zero with respect to an outside surface
of the car door during movement of the car door. .Iaddend. .Iadd.
37. A safety system as claimed in claim 36 and further including
means for providing each of said transmitting means with acoustic
wave energy, and means for each of said receiving means for
receiving reflection of said transmitted acoustic energy.
.Iaddend..Iadd. 38. A safety system as claimed in claim 36 wherein
said acoustic wave energy is constituted by a series of short
bursts of acoustic wave pulses of a single predetermined frequency
with comparatively large time gaps between bursts. .Iaddend..Iadd.
39. A safety system as claimed in claim 38 and further including
means for establishing as a timing signal said time gap between
bursts provided to said first transmitting means; and including
means for rendering said second transmitting and receiving means
effective upon detection of an object in its path in preventing
closure of said car door when signal received from said preceding
object occurs before expiration of said time gap of said timing
signal. .Iaddend..Iadd. 40. A safety system as claimed in claim 39
and further including means for varying said predetermined zone for
operation of said second transmitting and receiving means.
.Iaddend..Iadd. 41. The method of detecting presence of an
intervening object positioned in the path of a moving door that has
a leading edge and which moves towards a strike post, the method
comprising:
transmitting short bursts of acoustic wave energy from the leading
edge of the door;
monitoring for the reception of reflections of said acoustic
energy;
locating the leading edge of the door relative to the strike post
by determining a time interval that is equal to the time necessary
for said acoustical energy to travel twice the distance between the
leading edge of the door and the strike post; and
determining whether any received reflections were received during
said time interval, which is indicative of detection of an
intervening object. .Iaddend..Iadd. 42. The method as claimed in
claim 41 wherein said acoustic wave energy is transmitted in a
straight path between the leading edge of the door and the strike
post for detection of an intervening object in said path.
.Iaddend..Iadd. 43. The method as claimed in claim 41 wherein said
acoustic wave energy is transmitted in an angular path with respect
to line of movement of the door for detection of an intervening
object in said path. .Iaddend..Iadd. 44. The method as claimed in
claim 43 and further including transmitting further short bursts of
acoustic wave energy in a straight path from the leading edge of
the door toward the strike post for detection of a further
intervening object in said straight path; monitoring for the
reception of reflections of said further acoustic energy; and
determining whether any received reflections of said further
acoustic energy were received during said time interval which is
indicative of an intervening object. .Iaddend..Iadd. 45. The method
as claimed in claim 44 and further including stopping the movement
of the door whenever an intervening object is determined.
.Iaddend..Iadd. 46. The method as claimed in claim 41 and further
including rendering said determining step effective to stop the
movement of the door only when the reflected signal is received at
least a predetermined amount of time before the expiration of said
time interval. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates broadly to a safety system for protection of
persons or objects from injury by being struck by power operated
sliding doors. More specifically, it is particularly suitable for
use with elevator doors and is presented accordingly.
2. The Prior Art
Protective devices have been proposed from time to time to minimize
the danger inherent in automatically operated power sliding doors,
where no attendant is present to act as a guard against persons
being struck by the doors. The simplest and least effective of
these is found on subways and city buses, and consists only of a
collapsible rubber bumper along the door edge to cushion the impact
when a person is struck or caught. Beyond this non-preventive
approach are devices which attempt to prevent injuries by
minimizing or eliminating contact between the doors and persons
using them.
One such device has commonly been used on elevators in many forms,
the so called retractable safety edge. It consists of a strip of
rigid material, usually metal, covered at times with rubber or
plastic, mounted adjacent to the elevator car door on pivot arms
which allow its movement relative to the door. Through various
arrangements of mechanical coupling, the safety edge is caused to
precede the door edge by a small distance while the door is
closing. Subsequent pressure against the device opposite to the
direction of closing causes one to two inches of movement relative
to the car door, and actuates a switch to effect stoppage and
reversal of the door. Variations of the device have sought to
refine it (see U.S. Pat. No. 2,687,455) but in substantially all
cases the retractable safety edge requires contact with an object
in its path in order to work, is easily damaged because it precedes
the car door, and is generally poor because the combined inertia of
the car door and the hoistway, or bulding, door coupled to it is
often sufficient to carry both doors forward many inches after
first contact with the safety edge. Further, the hoistway door is
not normally supplied with a safety device, is located 5 to 6
inches apart from the car door, and consequently can strike a
person in its own path before that person can engage the safety
edge on the car door.
In order to improve the efficacy of the retractable safety edge,
various forms of photoelectric light beam controls have been
employed along with it, patterned after the methods of U.S. Pat.
No. 1,947,079. Persons or objects using the doorway must interrupt
a beam of light aimed horizontally across the doorway at some
specific height, thus producing an additional control signal to
that of the retractable safety edge. It has been the usual practice
to position the one or two narrow light beams of this method to
operate just outside the car door or, in certain case, just inside.
In either situation only moderate improvements in safety have been
evident. It has still remained possible for persons or objects to
miss the light beams completely, whereupon arms, legs or briefcases
are then caught by the door at some height other than that of the
light beams. As before, the hoistway door in this situation has
remained unprotected.
In recent years several versions of an "electronic" device have
been proposed to replace both the retractable safety edge and
photoelectric controls. U.S. Pat. No. 2,601,250 and later patents
trace the evolution of this device, which employs an
antenna-to-ground circuit. The capacitance of the circuit is
altered by the influence of some significantly large electrically
conductive object brought into close proximity thereto. In theory
these devices can be adjusted to respond to a variety of sizes and
characteristics of the objects they are to detect, or can be
adjusted in sensitivity to control their detection range, or can be
adjusted and compensated to nullify effects from variations in
hoistway doors, spacing, humidity and similar detrimental
factors.
A study of related art covering these "electronic" devices exposes
the difficulty of developing a single configuration capable of
handling effectively all of the environmental factors necessary for
proper operation. The predictable result has been complex and
costly mechanisms which require undue care during and after
installation and which usually demand extensive changes in existing
elevator installations before they can be used to replace older
existing safety devices. Further, extending the application of
these "electronic" devices to provide protection for the hoistway
doors requires fitting out each hoistway door at every building
landing with its own additional apparatus. Clearly such systems are
not well suited to the majority of situations where protection is
needed.
A recent invention covered by U.S. Pat. No. 3,367,450 addresses the
problem obliquely by using the Doppler shift in frequency principle
to detect whether persons might be moving toward or away from the
doorway opening, then using that information to hasten or delay
door closing. Unfortunately, the requirement for fairly rapid
motion of the person being protected does not cover stationary or
slow moving feeble persons, or objects directly within the door
opening, and that invention accordingly specifies additional use of
some other standard protective device such as the retractable
safety edge or one of the "electronic" variety.
In order to improve the general safety of persons using doorways
served by powered sliding doors, and specifically to improve both
the safety of elevator passengers and other load without undue
complexity of equipment or delay in elevator service speed,
information must be generated concering the position of persons or
objects in or near the doorway path including the path of the
associated hoistway door, without regard to whether those persons
be moving or still, leaving or entering, electrically conductive or
not, but with due regard to whether or not at any point in the door
travel they are endangered. Such information is enhanced if the
actual distance from the advancing door or doors to the person or
object is known, for a person directly in line with the door may
not actually be considered as endangered until it moves
sufficiently close to him. In commercial office buildings, where
speed of service is important and where passengers are
predominantly able-bodied adults, this is particularly true and it
is important to put the door into motion to herald imminent
departure of the car. However, in nursing homes and hospitals the
definition of total safety may well require the doors to remain
open and unmoving if a person is anywhere within the general
doorway, for example, a situation where a feeble person using a
walker or crutches timidly approaches the elevator car, or where a
stretcher is being moved.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide an improved
device for preventing injury to persons and objects using a doorway
serviced by powered sliding doors.
It is also an object of the invention to provide a means for
detecting persons or objects which, by their position in or near
the path of a powered sliding door, are endangered by the door.
It is a further object of this invention to provide a means for
defining the nature and extent of a zone of danger created in or
near the path of a powered sliding door and to exclude from
protective consideration persons or objects not within that
zone.
It is yet another object of this invention to provide an improved
apparatus for detecting substantial objects of any nature without
regard to their electrical or physical properties, texture,
temperature, color, shape or motion.
Other and further objects will be obvious upon an understanding of
the illustrative embodiment about to be described, or will be
indicated in the appended claims, and various advantages not
referred to herein will occur to one skilled in the art upon
employment of the invention in practice.
In accordance with the invention, distance from the car door
leading edge to any person or object located in or near the path of
either the car door or the hoistway door is continually measured as
the doors travel, using the principle of determining distance by
measuring time required for acoustic echoes to return to their
source from a reflection surface. In a preferred embodiment of the
invention ultrasonic acoustic wave energy is projected in short
bursts from the leading edge of the car door into a controlled
corridor of space embracing the paths of both doors and throughout
their vertical height, so as to describe a volume of space defining
the danger zone. Following each burst, echoes from objects within
the volume are measured against elapsed time and are compared to
selected fixed parameters and to the open width of the doorway as
the latter changes. Persons or objects that reflect energy within
specified time durations are considered to be in the defined danger
zone, and the shape and range of this danger zone may be controlled
to suit the greater need for speed or the greater need for safety
as desired. Pertinent art relating to a somewhat similar echo
ranging system using non-moving elements and surfaces, a fixed
range, and non-qualitative determinations can be found in U.S. Pat.
No. 3,412,390.
The invention contemplates elimination of all other forms of door
safety devices discussed previously in that is provides equal or
superior safety protection without sacrificing the utility of the
elevator car or requiring undue preparations for its use. The
invention further contemplates use on vertically sliding panel
doors, as might be found on freight elevators, or in non-elevator
applications such as supermarkets, terminals and airports.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention has been chosen for
purposes of illustration and description and is shown in the
accompanying drawings, forming a part of the specification,
wherein:
FIG. 1 is a downward isometric view, partly in section, of an
elevator doorway showing one portion of the protective features of
the invention;
FIG. 2 is a view similar to FIG. 1 but showing the remaining
protective features of the invention, presented separately for
clarity;
FIG. 3 is a plan view, partly in section, showing the elements of
FIG. 1;
FIG. 4 is a plan view, partly in section, showing the elements of
FIG. 1 following their displacement from the starting door-open
position;
FIG. 5 is a plan view, partly in section, of the elements of FIG. 1
showing the effects of range control;
FIG. 6 is a logical schematic diagram showing functional circuit
arrangements of one embodiment of the invention.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to the drawings, there is shown in FIG. 1 portions of
an elevator doorway pertinent to the present invention. The
observer is assumed to be looking downward from a vantage point
outside an elevator so as to view a platform 10 of the elevator
car, level with a building landing and a space 11 separated from
it. The car, constructed on platform 10, has a sliding door 12
suitably arranged to move along a line parallel to the platform
front edge and come to rest when fully closed against a strike post
13. Opposite car door 12 is a building, or hoistway, door 14
arranged to move parallel with the car door. On the hoistway door
14 are vanes or clutch plates 16 which interleave with a vane 17 on
the car door 12. With this arrangement the elevator car can move
vertically without affecting the hoistway door 14. However, any
horizontal motion of the car door 12 at a landing results in
corresponding motion of the hoistway door 14, and in this way it is
possible for the mechanism that opens and closes car door 12 to
likewise move hoistway door 14.
It is assumed that the motive means for the car door has some
control means which is responsive to input control signals of the
type generated by the invention, and that the door motion may be
caused to stop, reverse, or go forward, according to standard
practices known to the trade, as a result of said input cntrol
signals.
To further clarify the invention, dashed lines 18 depict the
outlines of portions of the building masonry which form the
vertical approachway to the elevator. The nearer of these to the
observer also forms a door stop for hoistway door 14, and dashed
lines 19 show hoistway door 14 in its closed position.
It will be shown that the purpose of the invention is to detect
objects located in or near the path of both door 12 and door 14 and
to cause the door operator control means to stop or reverse the
door closing process if said objects are endangered by either
door.
When both doors are fully closed, pressed tight against their
respective strike posts or door stops, they represent no danger to
persons or objects. If even a slight opening remains during the
closing process, however a hand, foot or small object can become
caught between either door and its strike post. Thus, the range of
distance through which a protective device should function extends
from a mere inch or so to the full opening of the doorway.
Certain variables must be considered in selecting a maximum
detection range, beyond merely the size of the door opening. One
variable might be, for example, the time required for a
floor-to-floor trip by the elevator car. Another variable would be
wear and tear on the equipment, which would understandably increase
from repeated unnecessary door motion reversals. In view of these
types of variables the protective device desirably should not
detect objects or persons in the doorway until danger is imminent,
allowing the doors to close partway so as to herald the departure
of the elevator car and to suggest the speeding up of entry or
exit. A detection range of the order of 8 or 10 inches would
fulfill the safety goals of the device while keeping things
moving.
On the other hand managers of certain buildings such as hospitals
and nursing homes or homes for the aged are far more concerned with
the total safety and peace of mind of elevator users, without
regard to speed or wear and tear, and here the full range of the
open doorway desirably would be used to prevent any motion of the
doors as long as someone or something was in their path.
Thus the full purpose of the invention is to provide safety
protection for persons and objects endangered by the car door or
hoistway door in variable situations of its use, requiring in some
cases shorter detection range and in other cases longer detection
range.
With these goals in mind and referring to FIG. 1, there is shown a
columnar element 20 attached to the side of the door 12 flush with
its leading edge. As seen thereon, a pair of acoustic wave
transducers 21 and 22, designated as distance measuring transmitter
and distance measuring receiver, respectively, occupy the uppermost
portion of the columnar element 20, substantially higher than a
majority of the traffic through the doorway. Transducer 21 is shown
above transducer 22, however, the reverse is equally acceptable or
a side-by-side arrangement may be used. In a preferred embodiment
of the invention both transducers operate most efficiently at 26
KHz. However, there is no specific best frequency for the
invention.
Distance measuring transmitter 21 is caused to emit energy in the
form of acoustic waves at 26 KHz in short bursts with relatively
large time gaps between bursts. The waves travel, or propagate, in
air at approximately 1100 feet per second, of 1.1 feet in each
millisecond. If this wave energy travelled for 4 milliseconds, for
example, struck a reflective surface, and was reflected back to its
source, the total time would be 8 milliseconds representing 8.8
feet for the round trip. By transmitting only a short burst of
energy and then "listening" for a time thereafter for echoes to
return, it is possible to decide the distance of some reflecting
object from the transmitter. There is no point in "listening"
beyond a certain time limit representing the maximum range of
interest, and so a subsequent burst may then be transmitted and the
process repeated continually. Whether the transmitter is fixed and
the reflecting object moving, or vice versa, or both moving
relative to each other, the above principle repeatedly and
continually indicates distance to the nearest significant "target"
in this way.
The purpose of distance measuring transmitter 21 and distance
measuring receiver 22 is to measure the distance to strike post 13
by sending energy along a path 23 to be reflected from the vertical
surface of post 13 along path 24 to impinge on receiver 22, by the
above method. The farthest possible distance travelled by this
energy is equivalent to the maximum door opening width, so that
this distance becomes the limiting range of interest for a given
doorway. It should be understood that in order to shorten this
range of interest, or lengthen it, the time duration allowed for
echoes to return is merely shortened or lengthened accordingly.
Echoes arriving simultaneously with or after the expiration of the
"listening" period are ignored.
Still referring to FIG. 1, there are also shown several second
pairs of acoustic transducers 26 and 27, designated as straight
detection transmitter and straight detection receiver,
respectively, again without regard to placement or order. These
comprise only a portion of the total detection function of the
invention, this portion being referred to as the straight ahead
direction, and their purpose is to measure the distance to objects
positioned substantially in line with car door 12. Crosshatched
area 28 of FIG. 1 shows the approximate shape of the energy path
belonging to transmitters 26 and receivers 27, as if projected
shadow-fashion .[.against shadow-fashion.]. against .Iadd.the
.Iaddend.floor .[.or.]. .Iadd.of .Iaddend.the elevator car. As
shown, more than one pair of transducers 26 and 27 may be used for
this purpose. In FIG. .[.2.]. .Iadd.1 .Iaddend.three such pairs, 26
and 27, are indicated for purposes of illustration and are
positioned in the drawing to imply their distribution throughout
the lengthwise dimension of columnar element 20.
Energy from each transmitter 26 travels along path 29 in a
diverging pattern until it reaches the vertical strike post 13. If
no intervening object is positioned in the energy path, a
reflection from strike post 13 will return generally along path 30
to impinge on receiver 27 at precisely the same instant when
similar reflected energy within path 24 impinges on receiver 22,
but the action of transmitter 21 and receiver 22, as previously
described, will negate the effect of reflected energy at receiver
27 by prohibiting its use in further processing. The arrival of any
reflected energy from objects some "lesser distance" away will,
however, be allowed as usable reflections representing objects
located between the columnar element 20 and strike post 13.
It should be understood that the term "lesser distance" in the
preceeding sentence refers to differences as small as fractions of
an inch between the distance to the reflecting objects and the
comparative distance to strike post 13, and it is only when these
two distances are exactly equal or when the distance to the
reflecting object is greater than the distance to strike post 13
that the action of transmitter 21 and receiver 22 intervenes to
discard the received reflection signals. Thus, even an object the
thickness of a person's hand, held flat against strike post 13,
presents a reflecting surface closer to the columnar element 20
that strike post 13 and produces a usuable reflection.
Factors other than the distance to strike post 13 will be shown to
further control and modify the status of reflected energy which is
otherwise usable, later in the discussion.
Referring now to FIG. 2, another pair of acoustic transducers 31
and 32 is shown, designated as angled detection transmitter and
angled detection receiver, respectively, once again without regard
to placement or order. These comprise the remaining portion of the
total detection function of the invention, this portion referred to
as the angled direction, and their purpose is to measure the
distance to objects located alongside the path of car door 12,
either within the space between doors 12 and 14 or directly in the
path of hoistway door 14, as illustrated by shaded area 36, shown
shadow-fashion against the floor. The energy transmitted from
transmitter 31 is aimed in a broadly divergent pattern at an angle
to the path of car door 12, so that a majority of the area outside
of the elevator car and including the path of hoistway door 14 is
reached. While there may be many pairs of transducers 31 and 32
used in an embodiment of the invention, there must be at least one
pair thereof. In FIG. 2 two such pairs are indicated for purposes
of illustration and are shown to imply their distribution along the
length of columnar element 20, perhaps interspersed with transducer
pairs 26 and 27 previously described.
Energy from each transmitter 31 travels generally along a divergent
path 33 until it strikes some object positioned in its path,
whereupon reflected energy returns generally along path 34 to
impinge on receiver 32. If the reflected energy arrives at receiver
32 prior to any limiting action of transmitter 21 and receiver 22,
as previously discussed, the object causing a reflection must be
located a distance less than the distance from the columnar element
20 to strike post 13, and is usable. The effect of the limiting
action of transmitter 21 and receiver 22 is to describe a radius R
equal to the width of the doorway opening, with origin at the
columnar element 20, sweeping an arc of limitation through space
beyond which no objects will be detected. As the door closes, this
radius R decreases until at full closure it is zero. Detection of
an object remains possible as long as the object falls within the
radius R and either in Zone 28 of FIG. 1 or Zone 36 of FIG. 2, no
matter how small the remaining opening may be. Further it becomes
impossible for a person or object to enter or leave the elevator
car without crossing either zone.
In FIG. 3 there is shown a plan view of the elevator entrance from
a vantage point directly overhead. Objects 37, 38, 39 and 40 are
placed in the entrance to demonstrate the effect of both the
straight direction and angled direction functions performed by
transducer pairs 26 and 27 and by transducer pairs 31 and 32. It
can be seen that object 40 and the building masonry outline 18
nearest strike post 13 both fall outside the effective radius R as
determined by transmitter 21 and receiver 22 of FIG. 1 and will
therefore not be detected as targets. Object 39 reflects no energy
at all and is therefore excluded. Objects 37 and 38 will be
detected, however, as they intersect the defined danger zones 28
and 36.
In FIG. 4, zones 28 and 36 have contracted to become zones 28a and
36a due to the closing motion of door 12. Object 41 clearly must
pass through both zones to enter the elevator car. Building masonry
18 nearest strike post 13 remains outside the effective radius R of
zone 36a and therefore is not detected as a target even though it
is undoubtedly reflecting energy in the angled direction.
In all of the preceding discussion it has been assumed that zones
28 and 36 of FIG. 1 and FIG. 2 are extended to their maximum limit
as determined by the action of transmitter 21 and receiver 22. This
is a desirable case where doorway protection is being provided in
nursing homes, hospitals and the like. However, extension of these
zones accordingly adds undesirably to the floor-to-floor time of
the elevator in situations where speed of service is essential,
such as in office buildings, for the detection of an object
anywhere within the combined zones of protection results in
re-opening of the door or prevention of further closing action as
long as the object is in range.
In order to alleviate this predicament, this invention provides for
individual control of the effective range of zone 28 and zone 36 of
FIG. 1 and FIG. 2 to some limit smaller than the width of the
doorway opening. This is accomplished by setting up time limits
measured from the beginning of each transmission burst to a point
represented by elapsed time whereafter no reflections will be
considered as usable. FIG. 5 illustrates zones 28b and 36b, each
shorter than the full doorway opening, and different from each
other. It will be seen that zone 36b still extends across path 19
of hoistway door 14, FIG. 2, and so spreads energy in front of door
14 as in previous examples. Dashed line 42 shows the outer-most
limit of the path of zone 36b as both doors progress to a position,
near strike post 13, depicted by dashed lines 43 and 19a. It can be
seen that object 44 may remain stationary, as shown, without being
detected until such time when door 12 has advanced a considerable
percentage of the doorway opening, whereupon object 44 will
eventually fall within zone 36b and be detected. It will be seen
further that zone 28b and zone 36b remain at their set range limits
until such time when, due to door travel, those limits become equal
to or larger than the actual doorway opening, as determined by
transmitter 21 and receiver 22, whereafter they become contracted
to effective limits as shown by zones 28c and 36c, less than radius
R as previously discussed, and will continue to be contracted until
they become zero at full door closure.
Therefore, this invention is provided with user-selected controls
for the effective detection ranges of both straight ahead zone 28
and angled zone 36. It allows doors 12 and 14 to proceed as long as
an object in their paths is beyond the selected ranges of imminent
danger, until each selected range in its turn is modified by the
overriding limit of actual doorway opening width, radius R of FIG.
2.
Throughout the preceding discussion strike post 13 has been the
vehicle of reflection for the energy of transmitter 21, simply
because in the example of an elevator doorway it is there as part
of the door frame and presents a convenient vertical surface of
sufficient area to produce good reflections. The use of strike post
13 in the example should in no way limit the invention to doorways
with similar strike post arrangements, for the same effect can be
produced by any suitable area arranged in line with the energy from
transmitter 21. In the case of an elevator which has so-called
center parting doors, for example, car door 12 exists as two
separate panels moving in opposite directions and coming together
at the vertical centerline of the doorway. Hoistway door 14 is
arranged similarly. A suitable reflecting surface mounted flush
with the leading edge of the opposing door will serve the same
purpose as did strike post 13 in that it will identify the farthest
limits of the doorway opening at all times.
A further example might be elevators of the freight variety
utilizing panel doors which open vertically. Here the invention
might be arranged horizontally on the upwardly opening car door so
that its acoustic energy radiated downward. The floor would become
the equivalent of strike post 13 in the case of a single door
arrangement. In the case of center parting vertically moving doors,
some suitable reflecting surface might be attached in appropriate
fashion to the opposing door to duplicate the function of strike
post 13.
Further details and understanding of the invention will now become
apparent through discussion of the successful embodiment which has
formed the basis of this application. FIG. 6 illustrates in a
functional way how the desired operation of the invention may be
accomplished, using where possible generic functional names of
various logical elements which are well known in varieties of form.
Also, an embodiment of the invention need not be limited to any
singular discipline but may use combinations of disciplines, such
as electronics, electromechanics, pneumatics or hydraulics. The
embodiment discussed has been accomplished using electronic and
electromechanical forms.
Referring to FIG. 6, oscillator 46 is a source of continuous
alternating signals which for illustration purposes may be set
equal in frequency to the chosen acoustic frequency of the
transmitters and receivers used. In the present case, output 47 of
oscillator 46 is 26 KHz and of a shape commonly referred to as a
square wave. Output 47 is directed to a frequency divider chain 48
containing seven successive sections, or stages, each of which has
an output frequency exactly one half of its input frequency.
Divider chain 48 therefore presents at its outputs, A, B, C, D, E,
F, and G subdivisions of input signal 47, such that output A is 13
KHz, B is 6.5 KHz, C is 3.25 KHz, D is 1.625 KHz, E is 8121/2 Hz, F
is 4061/4 Hz, and G is 2031/8 Hz. Any frequency 47 chosen to be
other than 26 KHz changes outputs A through G accordingly. This
type of division of frequency is called binary. The nature of
outputs A through G is such that two polarities, or states, are
used to represent information of the sense true-false, yes-no,
up-down or any set of dual meanings of special significance to the
user. In this discussion the sense OFF-ON is satisfactory and is
used throughout.
Further, where a given term such as a letter symbol is used, such a
designation is merely a name for the signal, nothing more. Further
still, the use of a bar symbol over any letter designation, such as
.[.A or G.]. .Iadd.A or G .Iaddend.signifies that the signal is
doing exactly the inverse of a concurrent signal A or G
respectively. If A is ON, .[.A.]. .Iadd.A .Iaddend.must be OFF. If
.[.A.]. .Iadd.A .Iaddend.is ON, A must be OFF.
Returning to FIG. 6, output G of 48 proceeds to a second binary
divider 49 to produce outputs H at approximately 102 Hz, J at 51
Hz, K at 251/2 Hz and L at 123/4 Hz. Dividers 48 and 49 have been
shown as separate functions here for clarity. In reality, they are
simply eleven successive binary division stages.
As discussed earlier, the operation of the invention depends on the
continuous transmission of short bursts of acoustic energy at a
frequency of 26 KHz, in one case from transmitter 21 and in the
other case from transmitters 26 and 31, as shown in FIGS. 1 and 2.
Following each burst is a "listening" period, and for illustration
this is chosen to be about 5/1000 second, or 5 milliseconds,
representing a distance of approximately 33 inches of range
maximum.
It will be observed that since output G of divider 48 is about 200
Hz, each cycle is 1/200 second, or 5 milliseconds. Output G is
therefore selected to become the master timing signal for the
operation. Each burst of frequency begins precisely at a known
condition of G and defines the need of a preceding listening
period. Output G is routed to the input of delay one shot 50 wich
triggers to produce at its output 51 an ON condition of short
duration, and 51 is routed to AND gate 52 to become an input. The
remaining input to AND gate 52 is signal 47, which is the 26 KHz
signal. The operation of AND gate 52 is as follows: when signal 51
is ON, signal 47 is presented intact at output 53, and when signal
51 is OFF, output 53 is blank.
Thus, during the short interval when output 51 of one shot 50 is
ON, output 53 of AND gate 52 is the desired 26 KHz signal. A short
burst of the 26 KHZ signal has been created just following the end
of a listening period, to start a new cycle under control of signal
G. Signal 53 is routed to transmitter 21.
Transmitter 21 may be any form or variety of ultrasonic transducer
suitable for the purpose, as the general field of ultrasonic
transduction is well known and the invention is not restrictive in
this area. Ceramic piezoelectric devices are well suited to the
application and are capable of producing good signals from low
voltage electrical signals. In the example, output 53 is directly
applied to transmitter 21 which produces acoustic waves at a
frequency of 26 KHz for the duration of time that signal 51 is
ON.
Similarly, receiver 22 is selected from the many forms of
ultrasonic sensory devices to create electrical signals from
impinging acoustic energy, and in the example receiver 22 receives
reflected energy desirably from strike post 13, FIG. 1. Output 54
of receiver 22 is routed to an amplifier 56 and squaring circuit
57. The function of squaring circuit 57 is to transform any signal
from amplifier 56, sufficiently large to be identified as a true
signal, into a uniform pulse of standard voltage levels for use in
the ON-OFF sense as previously described. A generic term for such a
device as squaring circuit 57 is the Schmitt Trigger, which can be
adjusted to produce an ON condition only when its input is above a
given threshold level of voltage, and is OFF for all lesser input
levels. Thus the output 58 of squaring circuit 57 changes from OFF
to ON at precisely the instant when sufficiently strong acoustic
energy impinges on receiver 22. If said energy results from
reflections from strike post 13 of FIG. 1, then signal 58
represents the point in time, following frequency burst 53,
equivalent to the distance from transmitter 21 to strike post 13
and back to receiver 22. This point in time defines the end of the
maximum "listening" interval.
In a like fashion, signal 53 is used to create acoustic energy
bursts in transmitters 26 and 31. Although the minimum number of
these transmitters in any given embodiment of the invention is one
of each, a higher number of each is contemplated and in this
example eight of each have been shown. There would therefore be
eight transmitters 26 operating in the straight detection mode and
eight transmitters 31 operating in the angled detection mode. It is
further contemplated that just one of these at a time will be
caused to generate an acoustic energy burst, followed successively
by each remaining transmitter in its turn until all have been used,
and the process repeated. Corresponding receivers 27 and 32 are
similarly employed in step with their counterparts. This process is
sometimes termed scanning, and the device which sequentially
connects many devices to a single wire or vice versa may be called
a scanner. In binary-based electronic systems, such as this
example, a scanner is often equipped with a set of control
connections intended for control signal inputs which are binary
subdivisions of each other, with frequency ratios of 4, 2, 1. The
device internally converts these control signals into commands for
proper sequencing, and for each distinct combination of binary
input signals the scanner connects an appropriate information
signal to a common terminal point. A very simple illustration of
such a device might be a rotary switch such as used in selecting
television channels.
In FIG. 6, signal 53 is accordingly routed also to scanners 59 and
60, each with eight information signal input "channels", whose
purpose is to connect signal 53 sequentially to eight transmitters
26 and eight transmitters 31 respectively. Each scanner is
controlled by binary frequency signals H, J and K from frequency
divider 49. Further, each scanner is supplied with an inhibiting
input N such that when any signal at the inhibit input is ON, the
scanner outputs are all blank. Signal L of divider 49 and its
opposite sense signal .[.L.]. .Iadd.L .Iaddend.perform the function
of inhibiting first one scanner, then the other, thus shifting
signal 53 from the straight detection transmitters 26 to the angle
detection transmitters 31 in alternating fashion. Each transmitter
26 is connected to signal 53 one time before scanner 59 is
inhibited, whereupon each of the transmitters 31 is connected to
signal 53 one time before the process repeats. It must be
remembered that between each burst of frequency of signal 53 is a
listening period.
In a like fashion, receivers 27 and 32 are connected through
scanners 61 and 62 to signal line 63. These scanners operate now in
the reverse sense but are otherwise identical to scanners 59 and
60. Since all four scanners are controlled by identical input
signals from binary divider 49, they are always in step. Any signal
representing received acoustic energy from receivers 27 or 32 is
therefore routed to amplifier 64 and squaring circuit 66 during the
listening period for that receiver-transmitter pair selected by the
scanners, is amplified and shaped as previously described, and
becomes output 67.
Output 67 then represents the occurrence of reflected energy from
an object. It remains to identify the relationship between the time
of occurrence of signal 67 and the several factors which govern
whether it may be interpreted as having arrived from an object
endangered by the doors, as previously explained, for though a
reflection from some object has been received and amplified during
a listening period, nothing further is known about it.
Flip-flop 68 is an element responsible for controlling the length
of each listening period. Its operation is such that for every
appropriate signal transition at its input T, output Q changes to
the alternate of two stable states. If Q is ON and transition
occurs at T, .[.O.]. .Iadd.Q .Iaddend.will go OFF. If Q is OFF and
a transition occurs at T, Q will go ON. A remaining input S is used
to restore the device to a given state at output Q regardless of
the state of input T. When S is ON, output Q is OFF and remains OFF
after S returns to OFF until a subsequent input transition at
T.
It may be seen that output 51 of delay one shot 50, used to produce
the burst of frequency in conjunction with AND gate 52, also is
routed to an input of OR gate 69. This gate is a logic element
whose output 70 is ON if any one of its inputs is ON, and whose
output is OFF only when all of its inputs are OFF. Consequently
signal 51 causes output 70 of gate 69 to be ON for the duration of
each frequency burst and forces output Q of flip-flop 68 to the OFF
condition through the action of input S. Q is used as an input to
AND gate 71, whose remaining input is signal 67 representing
reflected energy from some receiver-transmitter pair 27-26 or
32-31. Consequenly, AND gate 72 is blocked during the burst of
frequency period, and its output 72 is blank.
It is desired to begin the listening period as soon as the burst of
frequency has propagated away from the immediate vicinity of any
transmitter 26 or 31 sufficiently far so as to have escaped from
the physical structure of the columnar element 20. Delay one shot
73 is set to produce a signal 74 whose duration exceeds that of one
.[.shop.]. .Iadd.shot .Iaddend.50 by a small amount of time equal
to said escape time. Since both one shot 50 and one shot 73 begin
their respective intervals together with signal G, it follows that
signal 74 lasts slightly longer than signal 51. The transition of
signal 74 back to its original state at the end of its ON time
triggers flip-flop 68 at input T and, since signal 51 is by then
OFF, signal 74 is allowed to change output Q of flip-flop 68 to the
ON condition. The listening period has begun, and AND gate 71 will
now reproduce intact at output 72 all of the information on line
67.
The end of a listening period is controlled by output Q of
flip-flop 68 returning to its OFF state. In one case, already
discussed, signal 58 represents energy reflected from strike post
13 of FIG. 1 and signifies the radial distance R of FIG. 2.
Reflected energy from objects further away than R are to be
rejected by the invention, accomplished by ending the listening
period at precisely the instant when signal 58 operates through OR
gate 69 to return Q to its OFF condition.
It can be seen that signal 67 will be able to pass intact through
AND gate 71 only if it should occur prior to signal 58. Any
simultaneous occurrence of signals 67 and 58 will result in signal
58 negating signal 67 by shutting off AND gate 71. Thus any object
responsible for usable reflected energy represented by signal 67
must be positioned in the doorway some distance from columnar
element 20 less than the distance represented by signal 58, or
radius R of FIG. 2. If no reflected energy is received to produce
signal 58, then the listening period will continue until the start
of a subsequent frequency burst, whereupon output Q of flip-flop 68
is automatically returned to its OFF state by signal 51 as
described.
There remains to be explained those provisions exemplified by FIG.
5 wherein individual discrete time periods representing operating
range may be selected for the straight detection function and for
the angled detection function, and these may differ in value.
Delay one shot 76 is provided with adjustment element 77 which can
be set to govern the time period of one shot 76, following input G,
that its output is ON. Element 77 is available to the user.
Further, AND gate 78 is controlled by signal L at one input to
allow remaining input signal G to pass through intact only while L
is ON, and this action corresponds to the time period when straight
ahead scanners 59 and 61 are functioning. Output 79 of AND gate 78
starts one shot 76 at the beginning of each frequency burst when
signal L is ON, and output 80 of one shot 76 is arranged to turn
OFF for an interval thereafter, as selected with element 77. The
selected time duration would desirably fall short of that time
representing the full doorway opening. At the conclusion of this
selected interval, output 80 returns to its ON state and resets
flip-flop 68 through OR gate 69, as discussed previously. It should
be understood that the earliest reset signal arriving at OR gate
69, following the action of signal 74 to begin a given listening
period, will end the same listening period by resetting flip-flop
68 at its input S. Referring to FIG. 5 and in view of the
preceding, zone 28b has been shown set to some maximum range less
than the distance to strike post 13, through the combined operation
of AND gate 78, one shot 76, adjustment 77, OR gate 69 and
flip-flop 68. The action of these combined elements occurs prior to
any action due to signal 58 representing reflections from strike
post 13, and therefore cuts zone 28b short as shown. However, as
door 12 approaches strike post 13 there is always some point when
signal 58, a variable with door position, occurs before signal 80,
a fixed time period independent of door position. When door 12 is
closer to strike post 13 than the distance selected to create zone
28b, signal 58 is indeed earlier than signal 80. The listening
period is thereafter controlled totally by signal 58, until the
doors have closed fully.
In like manner, AND gate 81, one shot 82, adjustment element 83 and
signal 84 are employed during the duration of .[.L.]. .Iadd.L
.Iaddend.to govern the maximum range of the angled detection
function.
Thus the presence of any signal 72 at the output of AND gate 71
signifies reflected energy from some object either within the
selected range of zone 28 or within the selected range of zone 36
or within the radius R as determined by transmitter 21 and receiver
22, when R is smaller than the selected range of either defined
zone. Since these three parameters represent by definition
conditions of imminent danger to persons or objects in the path of
either door 12 or door 14, any signal 72 must result in a control
output signal from the invention to cause the door motive means to
stop and reverse its closing action. A typical control output
signal for such a purpose might be a switch closure produced by a
relay. Accordingly, the remainder of FIG. 6 shows one shot 86 used
to create a relatively long duration signal of uniform shape from
the sometimes long or sometimes short signals on line 72. Relay
driver 87 uses the shaped output to energize a relay 88, whose
contacts 89 are presented as terminations of the invention suitable
for the use described.
It is to be understood that all of the elements of FIG. 6 have been
presented as idealized generic devices and that provisions for any
impedance matching, polarity inversion, amplification or wave
shaping may be employed as required by the choice of elements used.
While a frequency of .[.27.]. .Iadd.26 .Iaddend.KHz has been used
in the illustration, any inaudible acoustic frequency may be
employed without affecting the principles described herein, and
other embodiments and applications are within the spirit and scope
of the invention.
It is further to be understood that the preceding illustration of
the invention presented two distinct portions of its detection
function, as represented by transmitter/receiver pairs 26 and 27
and by transmitter/receiver pairs 31 and 32, in order to create a
step-by-step description of the complete detection function.
Transmitter/receiver pairs 26 and 27 of FIG. 1 may be eliminated
from the invention without loss of function, as long as at least
one of transmitter/receiver pair 31 and 32 is employed as
described.
* * * * *