U.S. patent number 3,672,462 [Application Number 04/867,621] was granted by the patent office on 1972-06-27 for apparatus for controlling sonic energy distribution.
This patent grant is currently assigned to General Signal Corporation. Invention is credited to John H. Auer, Jr..
United States Patent |
3,672,462 |
Auer, Jr. |
June 27, 1972 |
APPARATUS FOR CONTROLLING SONIC ENERGY DISTRIBUTION
Abstract
An electromechanical transducer is provided for producing pulses
of sonic energy and respondingly generating electrical signals
relative to received sonic energy wherein a driver generates the
sonic pulses; and an improvement for projecting the sonic energy in
a peculiar controlled pattern is a wave guide interposed at the
output of the driver for controlling the propagation of the pulses
by setting up substantially a line source of sonic energy which
emanates the sonic energy in an operating pattern of at least a
minimum intensity near the point of greatest breadth of the
pattern. There has been provided an electromechanical transducer
for projecting sonic energy in a peculiar pattern including a head
mounted at the output of the transducer and a wave guide having a
transverse slot therethrough adapted to cooperate with the head for
directing the propagation of the sonic energy to substantially
complete sonic coverage within a limited range.
Inventors: |
Auer, Jr.; John H. (Fairport,
NY) |
Assignee: |
General Signal Corporation
(Rochester, NY)
|
Family
ID: |
25350140 |
Appl.
No.: |
04/867,621 |
Filed: |
October 20, 1969 |
Current U.S.
Class: |
367/93; 367/97;
367/175; 73/642; 367/138 |
Current CPC
Class: |
G01S
7/521 (20130101); G08G 1/04 (20130101); G10K
9/13 (20130101); G10K 11/28 (20130101); G01S
15/04 (20130101); G01S 7/2923 (20130101) |
Current International
Class: |
G10K
9/00 (20060101); G08G 1/04 (20060101); G01S
15/00 (20060101); G01S 7/292 (20060101); G01S
7/521 (20060101); G01S 15/04 (20060101); G10K
11/28 (20060101); G10K 9/13 (20060101); G10K
11/00 (20060101); G01s 009/00 (); H04r
001/28 () |
Field of
Search: |
;181/31A,.5R ;73/71.5U
;340/8RT,8L,38 ;179/115.5H ;333/95,98 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Borchelt; Benjamin A.
Assistant Examiner: Doramus; J. V.
Claims
What is claimed is:
1. An electromechanical transducer apparatus for producing pulses
of sonic energy and respondingly generating electrical signals
relative to received sonic energy wherein a driver generates the
sonic pulses and the improvement for projecting the sonic energy in
a peculiar controlled pattern comprises:
wave guide means interposed at the output of said driver and having
a rectangular opening formed in such wave guide means for
controlling the propagation of said pulses, the rectangular opening
formed in said wave guide means setting up substantially a line
source of sonic energy, said line source emanating the sonic energy
in an operating pattern of at least a minimum intensity near the
point of greatest breadth of the pattern.
2. The transducer apparatus of claim 1 wherein the wave guide means
comprises:
a cap having a radial slot of rectangular shape, mounted over the
output of said driver, for collecting and directing the energy
towards the slot, said slot for modifying the propagation of said
pulses to create the line source of pulsed sonic energy along the
slot when said sonic energy is propagated therethrough by the
driver.
3. The transducer apparatus of claim 2 wherein the wave guide means
further includes:
a suppressor for eliminating secondary oscillations produced as a
result of modification of the sonic energy pattern.
4. A transducer apparatus of claim 3 wherein the slotted cap for
modifying the pulsed sonic energy and the suppressor further
comprises:
two walls mounted at acute angles to the cap and each having a
straight edge;
the walls with straight edges parallel to each other at a
predetermined distance forming the slot, and
said angular positioning of the walls disposed inwardly towards the
driver for suppressing the secondary oscillations.
5. The transducer apparatus of claim 4 including a heat mounted to
the transducer between the output of the driver and the slotted cap
for further directing said beam and for further decreasing
secondary oscillations.
6. The transducer apparatus of claim 5 wherein the head comprises a
conoidal wedge-like body aligned with said slot, interposed between
said driver and wave guide.
7. The transducer apparatus of claim 6 wherein the conoidal
wedge-like body has a circular bottom and arcuate surfaces
extending from the bottom and meeting at the top of the body
forming a wedge tip, said wedge tip aligned in and lateral with the
slot.
8. An improved transducer wherein the improvement for projecting
sonic energy in a peculiar controlled pattern comprises:
a head mounted at the output of the transducer and;
a wave guide having a transverse slot therethrough adapted to
cooperate with the head for directing the propagation of the sonic
energy to substantially complete sonic coverage within a limited
range.
9. The improved transducer of claim 8 wherein the wave guide
comprises a cup positioned for covering the output of the
transducer and the head to capture the sonic energy and the slot is
positioned in the cup over the head.
10. The improved transducer of claim 9 wherein the cup includes
side walls at acute angles to the axis of the head projecting from
the slot inwardly towards the transducer, said side walls for
cooperating with the head for providing a relatively smooth
unobstructed exit path for sonic energy to be conducted towards the
slot whereby sonic energy is not reflected back into said
transducer causing distortion of said energy.
11. The improved transducer of claim 10 wherein the head comprises
a wedge-like conoidal body having arcuate sides oppositely disposed
in said cup such that the arcuate sides are relatively parallel to
the walls of the cup for further smoothing said exit path.
12. The improved transducer of claim 8 wherein said peculiar
pattern of controlled energy comprises:
a substantially minimum intensity pattern of elliptical shape, said
pattern in a plane substantially parallel to the output of the
transducer and within the limited range.
13. The improved transducer of claim 12 wherein a line source of
energy is set up along the slot of the wave guide and the
elliptical pattern is widest in a direction perpendicular to said
line source.
14. The improved transducer of claim 12 wherein the cup has a
conduit slot therethrough providing a drainage for collected fluids
in said cup.
15. A vehicle detection system comprising a transducer responsive
to pulsed electrical energy for providing emitted sonic energy
pulses and respondingly generating electrical signals relative to
received sonic energy including:
a wave guide means interposed at the output of the transducer
having a transverse opening formed therein for directing the
propagation of the emitted sonic energy pulses to establish
substantially complete sonic coverage within a limited area.
16. The vehicle detection system of claim 15 wherein said peculiar
pattern of controlled energy is at least a minimum intensity of
sonic energy pulses covering an elliptical pattern.
17. The vehicle detection system of claim 16 wherein the wave guide
means includes a cap having a radial slot therein forming the
transverse opening, a line source of sonic energy formed along said
slot for providing the elliptical pattern of sonic energy in a
plane parallel to the output of the transducer, said elliptical
pattern widest in a direction perpendicular to the line source and
having at least a minimum intensity in said pattern.
Description
BACKGROUND OF INVENTION
The present invention relates to sonic detector systems and more
particularly to systems capable of distinguishing vehicle reflected
signals in a defined zone.
Sonic detection systems find utilization in a number of
applications, for example, traffic control and garage supervision.
This invention describes a system primarily intended for the
detection and indication of vehicle presence for traffic
control.
In a typical application, detection systems transmit short duration
pulses of vibration energy, preferably within the ultrasonic
frequency region. These pulses are directed toward the vehicles by
transducer apparatus which also produces electrical signals by
responding to reflected energy from the roadway and vehicle
surfaces. The roadway reflections are gated out of the system and
have no effect upon its operation. Those signals reflected from the
vehicle or object are recognized and produce a distinctive
indication of vehicle or object presence. Thus, presence of a
vehicle or object on the roadway is indicated whenever sufficiently
strong reflections of sonic energy are received by the transducer
apparatus within the vehicle gate interval.
In practice, systems using ultrasonic techniques have proven
substantially successful and adaptable to various environments and
targets. However, due to the nature and design of those presently
deployed systems, all in varying degrees are limited by certain
operation deficiencies. Primarily these deficiencies may be related
to the inability of the system to adequately distinguish false
signals, either generated within the system or present in the
environment, from signals actually reflected from the surface of
the vehicle or object under scrutiny. Noise or false signals mainly
result from electrical coupling within the system and ringing or
continued vibration of the sonic transducer after transmission of
each sonic pulse. The latter source of noise is the use of a single
sonic transducer for both transmitting and receiving. Another
noteworthy problem concerns vibrations in reflected signal strength
due to differences in shapes and sizes and materials of the vehicle
or objects. Variation occurs in reflected signals also because the
initial pulses are projected in "lobes" of high and low intensity
patterns. That is, over a desired zone of detection, the intensity
of the pattern of pulses projected by the transducer varies
significantly to cause sensitivity problems. When a wide detection
zone is desired, apparatus necessary for detection in a large zone
is multiplied because the so-called low intensity areas must be
covered with at least a minimum intensity pattern before a
significant reflected signal can be utilized.
SUMMARY OF INVENTION
There has been provided an electromechanical transducer for
projecting sonic energy in a peculiar pattern including a head
mounted at the output of the transducer and a wave guide in the
form of a cap having a transverse slot therethrough adapted to
cooperate with the head for directing the propagation of the sonic
energy to substantially complete sonic coverage within a limited
range.
An electromechanical transducer apparatus for producing pulses of
sonic energy and respondingly generating electrical signals
relative to received sonic energy has been provided. A driver
generates the sonic pulses and an improvement for projecting the
sonic energy in a peculiar controlled pattern is a wave guide
interposed at the output of the driver for controlling the
propagation of the emitted sonic pulses. The wave guide means sets
up substantially a line source of sonic energy. The line source
eminates the energy in an operating pattern of at least a minimum
intensity near the point of greatest breadth of the pattern.
There has been provided an improved object detection system wherein
a transmitter produces periodic pulses of sonic frequency and
peculiar time duration. A transducer converts these pulses into
emitted sonic energy pulses and respondingly generates electrical
signals relative to received sonic energy including energy
reflected from the object. A detector manifests an indication of
object presence when actuated and a receiver is rendered responsive
for a selected interval to the signals for actuating the detector
only when signals having a peculiar characteristic correlative to
the pulses of sonic energy are received during the selected
interval. The improvement provides for projecting the emitted sonic
energy in a peculiar pattern wherein a wave guide means interposed
at the output of the transducer modifies the propagation of the
emitted sonic energy pulses to control the pattern. The wave guide
means sets up substantially a line source of emitted sonic energy
for spreading the emitted sonic energy pulses in a direction
perpendicular to the line source such that an elliptical pattern of
sonic energy is produced and said line source provides an operating
pattern of at least a minimum intensity over the elliptical
pattern.
It is another object of the invention to provide an improved object
detection system with a controlled detection zone.
It is yet another object of the invention to provide a vehicle
detection system wherein a transducer produces a peculiar pattern
of at least a minimum intensity.
It is still another object of this invention to provide a
controlled pattern of sonic energy in a controlled area.
It is another object to provide an enlarged pattern of sonic energy
distribution.
It is yet another object of the invention to adapt wave guide
techniques to sonic detector systems for increasing the reliability
of such systems.
The foregoing objects and features of the present invention are
clearly outlined and explained in the drawings and detailed
description.
DESCRIPTION OF DRAWINGS
The drawings contain the following:
FIG. 1 shows one embodiment of the object detection system of the
present invention.
FIG. 2 shows another embodiment of the object detection system of
the present invention using two-pulse recognition.
FIG. 3 shows a pattern of emitted sonic energy of a transducer
without the improvement of the present invention.
FIG. 3A shows a projection of the emitted sonic energy of FIG. 3
along 3A--3A.
FIG. 4 shows a pattern of emitted sonic energy of the transducer of
the present invention.
FIG. 4A shows a projection of the emitted sonic energy of FIG. 4
along line 4A--4A.
FIG. 5 shows a side section elevation of the transducer of the
present invention.
FIG. 6 is a top elevation of the transducer of the present
invention.
FIG. 7 is a portion of the preferred wave guide means.
FIGS. 8 and 9 are side and bottom elevations of the preferred
insert, respectively.
FIG. 10 is a side view of a modified wave guide.
FIG. 11 is a side section elevation of the prior art
transducer.
FIG. 12 is a front elevation of the modified wave guide of FIG.
10.
DESCRIPTION OF THE EMBODIMENT
FIG. 1 shows a detection system incorporating pulse recognition and
detection in which a time base generator 10 containing a
free-running oscillator of the multivibrator or other similar type
generates pulses of desired repetition rate. The time base
generator 10 has two outputs alternately producing pulses. The
alternate pulses are used to control a receiver gate generator unit
11 and a transmitter pulse character generator 12 respectively.
The pulse character generator 12 produces a pulse having an
identification characteristic different from the noise signals
either generated or received by the system. A transmitter 14 is
controlled to transmit an electrical signal of substantially a
single sonic frequency possessing the same identification
characteristic. The transducer apparatus 15 responds to the
transmitter 14 by converting the transmitter 14 electrical signals
into a vibratory output of substantially the same frequency and
characteristic. It also responds to reflected or environmental
sonic energy by generating electrical signals. Thus the transducer
apparatus 15 respondingly produces electrical signals corresponding
to environmental sonic noise and reflected sonic signals.
The receiver gate generator 11 when keyed by the time base
generator 10 provides a system gate signal activating the receiver
circuitry for periods of time relative to the anticipated receipt
of reflected signals from the targets. The receiver isolator unit
16 conducts the electrical signals to the receiver amplifier 17 and
provides the desired impedance levels for the transducer apparatus.
It is primarily needed in applications where a single transducer
for both transmitting and receiving is utilized. The receiver
amplifier 17 is tuned to the sonic frequency of the transmitted
pulse and thus is primarily responsive to only those signals
containing energy within its band. The gate signal supplies bias
voltage to the first stage of the receiver amplifier 17, and thus
controls its response. When no gate signal is present, the gain of
the receiver amplifier 17 is essentially zero while during the gate
signal interval it reaches a value determined by the parameters of
the circuit. This gain control prevents the amplifier from
responding to signals received at times other than those
anticipated for reflected target signals. Amplifier gain is also
modified during the gate interval by other circuitry to further
control the response of the system to ringing signals and
variations in signal strength. These controls will be more fully
described in ensuing detailed descriptions.
The recognition detector 18 responds only to those amplified
signals having the peculiar identification characteristic of the
transmitted pulse. If the received electrical signal is coincident
with the gate signal and has a characteristic correlative to the
peculiar character of the transmitted pulse, the recognition
detector 18 circuitry will respond. The recognition detector 18
circuitry may be conditioned to respond only to a plurality of
reflected signals received within a particular selected interval
ranging over a number of transmission cycles. Should the
requirements of the recognition detector 18 be met, it initiates an
alteration in the detection memory 19.
The detection memory 19 when altered to a second stable state,
produces a distinctive indication of vehicle presence and also
causes a release timer 20 to be activated. Should signals be
produced by the recognition detector 18 at a rate greater than a
predetermined minimum, the release timer 20 once actuated, is
prevented from producing an output signal. At such time, however,
as recognition detector 18 signals cease, relative to the removal
of the object or vehicle from the detection zone, the release timer
20 times out and extinguishes the presence indication in the
detection memory 19, thus conditioning the system for detection of
succeeding vehicles or object. The detection memory 19 contains a
feedback feature represented by line 21 which increases the gain of
the receiver amplifier after detection is accomplished. The
increased gain prevents loss of recognition due to reductions in
reflected signal strengths.
An embodiment using multiple pulse detection is also detailed. It
must therefore be kept in mind that the various forms shown are
intended to show equipment organizations conforming to the
exigencies of practical applications and not necessarily providing
the maximum security available for any given situation.
FIG. 2 shows a system embodiment, containing both pulse recognition
and plural pulse detection, wherein a time base generator 10
comprising any suitable free-running oscillator of required
pretition rate, creates repetitive pulses used to key the
transmission of sonic energy and receiver gate signals. The time
base generator 10 output is conducted to the transmit pulse timer
22, which apparatus provides a pulse output of approximately 5
millisecond duration to drive transmitter 14. The transmitter
output, a substantially monotonic energy pulse of 5 millisecond
duration, supplies power to the sonic transducer 15. The sonic
transducer 15, through electromechanical conversion, directs
compressional wave front signals, commensurate to the frequency of
the transmitter signal, to intercept the predetermined path of
moving vehicles or objects.
The time base generator output 10 determines the repetition rate of
receiver gate signals by triggering the receiver gate generator 11.
In response to each pulse from the time base generator 10; the
receiver gate generator 11 produces an output signal of sufficient
duration so as to encompass an interval of time commencing shortly
after the cessation of transducer 15 transmission and ending
shortly before the time required for acquisition of the sonic
energy reflected from the pavement. If the system is used where no
pavement reflection exists, then a different time may be selected.
The receiver gate generator 11 output is utilized by various parts
of the system, viz., the receiver amplifier 17, receiver pulse
timer 23 and gate and memory 24 in the recognition of reflected
vehicle signals.
The sonic transducer 15 in addition to being capable of converting
electrical energy into mechanical motion, is also sensitive to the
receipt of pressure variations. Pressure variations are caused by
ambient noise conditions present in the environment of the
transducer and energy reflections in response to its own
transmitted pulses. Thus, as a transmitted sonic pulse is reflected
either from the roadway or a passing vehicle, it is sensed by the
transducer 15 and results in generation of a voltage output. The
voltage output is coupled to the receiving portion of the system
through receiver isolator 16 which allows the receiver portion of
the system to sense reflected signals while rejecting excessively
large signals produced when voltage or power is supplied to the
transducer 15. Also prevented is the loading of the transmitter 14
during pulse transmission periods and the transducer 15 during
energy reflection periods.
Output from the receiver isolator 16 is conducted to the receiver
amplifier 17. The amplifier is tuned to the tonal frequency of the
transmitter-transducer combination and is relatively unresponsive
to any received signals not primarily containing that single basic
frequency; this results in rejection of a certain amount of noise
received from environmental effects on the transducer itself. The
receiver amplifier 17 is rendered responsive by the receiver gate
generator 11 signal, thus avoiding responding to energy pulses
indicative of transmitted rather than reflected signals.
The received signals of specified tonal frequency after
amplification are received by the receiver pulse timer 23 which is
arranged to produce a signal output upon its recognition of pulses
having a time duration in excess of 3 milliseconds. Further, the
received pulses of required duration must be coincident with the
gate signal provided by receiver gate generator 11. If these two
conditions are met, a signal output lasting for the remaining
duration of the gate signal period is produced by the gate and
memory unit 24.
The gate and memory unit 24 is only enabled during the gate period
provided by receiver gate generator 11. Its memory feature is
provided by the bistable character of its circuitry; once energized
during the gate interval, it can be only deenergized upon cessation
of the gate signal. Thus, the receipt of reflected signals during
the gating period produce only a single output from the gate and
memory unit 24.
The two-pulse detector unit 25 is actuated if more than a single
output signal is derived from the gate and memory unit 24 during a
predetermined span of time. This interval is selected to encompass
one or more energy transmission cycles, a single cycle consisting
of the time between successive transmission of energy from the
sonic transducer 15 as determined by the time base generator 10.
System parameters are chosen to demand two received pulses before
producing an output from the two-pulse detector 25 to indicate the
presence of a passing vehicle or object of this condition
ultimately distates the cycle time of the system dependent upon the
transducer 15 coverage and the maximum speed of the vehicles.
The two-pulse detector 25 output then effects a change of state in
the detection memory unit 19. Once the detection memory unit 19 is
altered, it remains so until output signals from the gate and
memory unit 24 cease for longer than a certain maximum period. The
desired period, before resetting of the detection memory unit 19,
is determined by specified operational requirements and implemented
by a release timer unit 20. The release timer unit 20 starts to
time out whenever a signal is produced by the detection memory unit
19 and is reset to start upon each receipt of an output signal from
the gate and memory unit 24. Thus, as long as signals are being
received from the gate and memory unit 24 at a certain minimum
rate, the release timer unit 20 is not permitted to time out. At
such time as these, signals cease for a period commensurate with
the minimum rate, the release timer 20 goes through its time cycle
and produces an output signal which in turn resets or clears the
detection memory unit 19.
In addition to the problems described in the previous discussion,
difficulties associated with acoustical patterns set up by the
transducer must be discussed. These problems when solved provide
for reliability relative to the detection zone pattern and thus
increase the efficiency of the electronic improvements previously
discussed.
Referring to FIG. 3 of the drawings, the transducer unit 15 without
the improvement of the present invention and its normal sonic
pattern is shown. The curve G at a radius D from transducer 15
represents the gate interval set up by gate generator 11. This wave
pattern is of a uniform intensity along line 26. This intensity
represents the minimum signal which must be transmitted by the
transducer unit 15 in order to receive a reflected signal from an
object within the detection zone of any usable intensity. The
pattern of FIG. 3 has a major lobe in the center and two minor
lobes to either side of center. This pattern presents certain
difficulties in vehicle traffic detection. The pavement 27 is
divided into two lanes at center lane marker CL; L and R
representing left and right. It is sometimes desirable to be able
to detect vehicles in both lanes L and R. For this reason,
transducer 15 is placed above the center CL of the highway as
shown. Vehicles coming within the detection zone of the unit 15
reflect sonic pulses from the surface of the vehicle to the unit 15
and a suitable electrical signal is generated for controlling the
associated apparatus. Certain of the reflected signals to the
transducer 15 are gated out by the timing of the various circuits
of the system. Generally all signals below one or two feet from the
pavement 27, represented by curve G, are gated out so that there is
no pavement reflection to the transducer 15. However, it can be
seen from the drawing that the areas 29 and 29' indicate that the
minimum intensity sonic energy varies along curve G. With this
difference in intensity shown merely by way of example in FIG. 3,
it is possible to miss or lose sight of a vehicle in the detection
zone. To alleviate this problem, it has sometimes been necessary to
use separate transducers and place one over each of the lanes L and
R to be certain of positive detection. This, when multiplied by as
many intersections that are usually controlled by systems of this
sort, requires additional equipment which is quite costly.
FIG. 3A is a projection of the pattern provided by transducer 15
upon a plane parallel to the highway containing line 3--3'. The
outer circle 30 shows the extremity of the system or widest range
of points A--A'. Circles 31 and 32 define an annular shaped area 33
(unshaded) produced by the rotation of points B--B' and C--C' by
180.degree. about the center CL of the highway 27, wherein a
substantially less intense signal is received or available in the
detection zone. A vehicle may be present in area 33 and yet be
missed by the detection system. Line 32, the innermost circle,
shows again a high intensity area possibly the width of one lane of
traffic which would be used in single lane occupancy detection.
FIG. 4 shows the transducer 15 of the present invention with wave
guide 34 adapted to the output of the transducer 15. This wave
guide 34 modifies the sonic pulses emitted from transducer 15 by
setting up a line source at the output of wave guide 34 and
produces a pattern having at least a minimum intensity signal over
the detection zone. The curve G similar to FIG. 3 at a radius D
from the transducer 15 represents the gate interval set up by gate
generator 11. From this all signals below line G are gated out by
the system and transducer 15 is not responsive to reflected signal
from any objects beyond curve G. Comparing FIGS. 3 and 4, it is
apparent that empty areas 29--29' of FIG. 3 are not present within
curve G and therefore the whole detection zone is filled.
FIG. 4A is a pattern 30' of the sonic energy in a plane including
line 4A--4A parallel to the highway. The pattern in FIG. 4A shows
an elliptical shape 30' covering more of an area than the pattern
in FIG. 3A. The curbs 36--36' shown in FIGS. 3A and 4A define the
width of the highway 27. It is clear that the projection 30 in FIG.
3A does not extend as widely as the projection 30' of FIG. 4A. The
elliptical pattern may be arranged to either be longitudinal with
the direction of the highway or across the two lanes L and R as
shown in FIG. 4A. It has also been found useful to use the
arrangement of the present invention with sidefire operation when
across the highway detection is desired for three lane detection.
That is, the transducer 15 is mounted off to the side of a highway,
projecting sonic energy across the highway rather than down upon
it. The same gating techniques are used as previously described,
but for particular applications, side-fire may be more useful.
Because of the shape of walls 48 and inserts 52, if the device is
used for side-fire operation, it is possible for water to collect
in the wave guide 34. Slot 51 extending through wall 48 provides
for adequate water drainage under such circumstances.
As will be explained later, the elliptical shape of the pattern is
a direct result of the wave guide 34 being interposed after output
of the transducer 15. A vehicle anywhere within the range of the
device across the highway 27 will be detected whether it is in the
left or right lane.
The transducer 15 and certain components shown in FIGS. 5-9
includes a ferro-magnetic base 40 in which is mounted magnet 38 and
ferro-magnet circular pole piece 41 and an outer pole piece 46
located about pole piece 41 leaving an annular air gap 42 for the
flux of magnet 38. Non-ferromagnetic annular member 37 maintains
the alignment of the air gap 42 between outer pole piece 46 and
inner pole piece 41 without shunting the field in the air gap 42.
The magnet 38 provides magnetic flux through inner pole piece 41
across the air gap 42 through outer pole piece 46, base 40 and back
to the bottom of magnet 38. Diaphragm 45 having an annular shape
for mounting over slot 42 includes ring 44 which fits into slot 42
and is capable of movement therein. The ring 44 has a wire coil 39
built therein, wrapped around, circularly, with the inner pole
piece 41 and the wire coil 39 is attached by leads 43 to terminal
points 47 for actuation by electrical energy. The diaphragm 45 is
driven by ring 44 and coil 39 where it interacts with the magnetic
field of the magnet 41 and produces emitted sonic energy pulses in
response to electrical signals impressed in leads 43, and diaphragm
45 drives coil 39 which generates electrical signals from reflected
pulses. An outer wall 48 is mounted on top of the outer member 46
and extends downwardly and inwardly from the top about the outer
edge of diaphragm 45. Head 49 is a conoidal wedge having a defined
shape mounted in the center of the transducer through a shank hole
50 through inner pole piece 41, magnet 38 and base 40 by screw 81.
Wave guide 34 is formed by two wedge shaped inserts 52 mounted in
the walls 48 of transducer 45 by screws 53. The wedges 52 in
combination with the walls 48 provide a passage way forming a wave
guide cap having a slot 54 for guiding pulses of sonic energy for
transmission and reception by the driver of a transducer.
FIG. 11 shows a cross section of a typical transducer 60 of the
prior art which includes a ferro-magnetic base 61, a magnet 58
mounted in the base 61, a circular inner pole piece 62 mounted
above the magnet 58 and outer pole piece 63 which is mounted to the
base 61, forming an annular air gap slot 64 between the inner pole
piece 62 and outer pole piece 63. Non-ferro-magnetic annular member
57 maintains alignment of air gap 64 between outer pole piece 63
and inner pole piece 65 without shunting the field in the air gap
64. Magnet 58 provides the flux through inner pole piece 62 across
air gap 64 through outer pole piece 63 through the base 61 to the
bottom of magnet 58. A diaphragm 65 having an annular shape is
mounted over the air gap 64. The diaphragm 65 has a ring 66
attached thereto with a wire coil 59 built in about the ring 66,
circularly of the magnet 62 with leads 67 attached to terminals 68.
When an electrical signal is impressed on terminals 68, a current
flows through ring 66 and coil 59 and interacts with the field
established by magnet 62 and a reflected pulse vibrates diaphragm
65 causing pulses of electrical energy to be generated in ring 66
and coil 59 and transmitted to terminals 68. Outer walls 69 are
mounted to the base 61 over outer pole piece 63 about diaphragm 65
and bullet 70 is mounted to base 61 through shank hole 71 in base
61, magnet 58 and inner pole piece 62.
The wave guide 34 of transducer 15 shown in FIG. 6 provides a slot
54 at the output of the transducer 15. This slot 54 interfers
somewhat with the propagation of the sonic pulses emitted from the
transducer at the diaphragm 45. A line source of sonic energy is
set up along slot 54 and the line source produces a uniformly
projected pattern of sonic energy along the slot 54 which projects
the energy in the desired pattern. The intensity is spread somewhat
in a direction perpendicular to the direction of the slot. In this
way, the transducer 15 can be placed above two lanes of traffic as
shown in FIG. 4 and the slot can be aligned with the direction of
traffic flow such that the line source of sonic energy aligned
along slot 54 radiates sonic energy tending to spread perpendicular
to the direction of slot 54 which generally is aligned with the
traffic flow so that the pattern is spread across the lanes as
shown in FIG. 4A.
The wave guide 34 is composed of two removable wedge shaped inserts
52--52. Screw 53 fastens the wave guide inserts 52 to wall 48 and
allows for the removal of wave guide to permit theuse of the
transducer 15 as a single lane occupancy detector.
The use of wave guide 34 also suppresses secondary oscillations
which may arise by insertion of the wave guide 34 initially. With
reference to FIGS. 10 and 12, it is possible to obtain a pattern
similar to that shown in FIG. 4 by placing a plate 73 over the
output of transducer 60. Plate 73 has a slot 74 therein. There
would be an air space 75 between the diaphragm 66 of the transducer
60 and the outer wall 69 such that sonic pulses emitted from the
diaphragm 65 may bounce against plate 73 and cause ringing which
would actuate the system improperly.
Bullet 49 shown in side and bottom elevations in FIGS. 8 and 9
respectively is incorporated in transducer 15 and provides for a
smooth exit path for sonic energy. It fills a gap between the
diaphragm 45 and slot 54 and inserts 52--52 so that secondary
oscillations will not be reflected back into the transducer 15
while it is transmitting sonic pulses. The conoidal wedge-like
shape of bullet 49 and the width of slot 54 as shown has been
determined by experimentation to obtain the most efficient
configuration for the particular frequencies being used in this
application. Typically the frequencies range in the area of 20
kilohertz.
The present disclosure describes a system combining sonic energy
gating with a controlled beam of pulses. The gating the timing of
the various pulses as they are transmitted and reflected back as
previously described are to a degree dependent upon an accurate
zone of detection. It is possible to get such an accurate zone by
using more than one transducer. However, this requires additional
equipment which often is very expensive. The present system
provides for a controlled detection zone by using one transducer
having a wider area of detection than has heretofore been advisable
to use. A higher input to the transducer 15 does not necessarily
increase the effectiveness of the system because the wave patterns
are substantially the same whether there are high or low intensity
inputs. The wave guide means 34 is the device which modifies the
pulse transmission such that a uniform pattern of sonic energy is
distributed over a desired area. In this case, an elliptical
pattern such that two lanes of traffic may be detected at the same
time.
The present invention also provides for a convertible feature to be
incorporated into the wave guide 34. This convertible feature makes
it possible to adapt the transducers presently being used to double
lane occupancy detection and also provide for transducers of the
present invention to be used as single lane occupancy detectors
without substantial change in the cost of the overall detector.
That is it would be possible to substitute the conoidal wedge-like
bullet 49 for the prior art bullet and mount inserts 52--52 in
alignment with the bullet 69 to form the wave guide. In addition,
the inserts 52--52 may be removed having a pattern adaptable to
single lane detection without a substantial effect on the
efficiency of the transducer 15 in other respects.
The removability of wave guide 51, i.e., by removal of wedges
52--52, provides transducers adaptable to systems which are already
in operation. These devices when combined with the gating
techniques described previously increase the efficiency of
operation without a sacrifice of a substantial amount of expense
and time in installation.
The use of the wave guide means of the present invention provides
for an enhanced system wherein controlled beam propagation is
provided. The invention provides a method of adapting present
detectors to the more efficient operation of the present disclosure
by the interposition of two inserts forming a wave guide at the
output section of present vehicle detectors in use in addition to
the wave guide, a new bullet is inserted for providing a smooth
exit for sonic pulses. The use of the wave guide 34 in connection
with sonic detectors has not heretofore been used as a method of
controlling the sonic beam. While there are methods of controlling
sound patterns into various directions including so-called sound
lenses, the cost, size and excess of reflected secondary signals
causing ringing is prohibitive in the applications for which these
devices are contemplated. Wave guide 34 when used in conjunction
with a highly efficient sonic transducer produces an energy pattern
which is quite efficient and adaptable to the uses for which the
invention was developed, without excess production, installation
and maintenance expenses.
While there has been described what is at present considered to be
the preferred embodiment of the invention, it will be obvious to
those skilled in the art that various changes and modifications may
be made therein, without departing from the invention, and it is,
therefore, aimed in the appending claims to cover all such changes
and modifications as fall within the true spirit and scope of the
invention.
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