Oscillating scanner arrangement

Detection systems for identifying an object in the path of a vehicle are affected by external interferences which render them unreliable. An oscillating scanner arrangement having first and second spaced apart transceiver assemblies is mounted on a frame of the work vehicle at spaced apart locations and are each pivotally movable between spaced apart angular positions. First and second devices pivotally connect the first and second transceiver assemblies respectively to the frame, and a power device reciprocally moves the first transceiver assembly between the first and second positions. A tie arrangement connects the first transceiver assembly to the second transceiver assembly and reciprocally moves the second transceiver assembly between the third and fourth positions. Thus, the problems related to external interference are solved in an efficient and economical manner. The oscillating scanner arrangement is particularly suited for use on a material handling vehicle.

TECHNICAL FIELD 
This invention relates generally to an oscillating scanner arrangement for 
a vehicle and, more particularly, to an oscillating scanner arrangement 
having the first transceiver assembly pivotally connected to a material 
handling vehicle at a first location and a second transceiver assembly 
pivotally connected to the material handling vehicle at a second location 
spaced from said first location, and a drive means for reciprocally moving 
the first and second transceiver assemblies about the first and second 
axis. 
BACKGROUND ART 
Work vehicles such as material handling vehicles, for example, lift trucks, 
platform trucks, AGV's (automatic guided vehicles), and the like are 
provided for transporting loads between spaced apart locations in 
factories, warehouses, and the like. Often there are several work vehicles 
operating within close proximity to one another which makes it necessary 
to provide a detection system to identify when another vehicle is in its 
path of travel. This is particularly the case when the vehicle is of the 
driverless type. 
U.S. Pat. No. 4,345,662 dated Aug. 24, 1982 to Michael Deplante depicts an 
automatic guided vehicle with a radar detector consisting of one or more 
ultrasonic emitters and one or more ultrasonic receivers for detecting 
obstacles in the path of the vehicle. These radar detectors are rigidly 
secured to the vehicle and disperse ultrasonic signals fore and aft of the 
vehicle. One problem with such a system is that vehicles of this type 
operate in environments that are often noisy and disruptive to ultrasonic 
sensors of this type. As a result, false signals received would adversely 
affect the operation of the vehicle and cause frequent shutdowns of the 
AGV and adversely affect the overall operation of the workplace. 
In order to improve over the reliability of a ultrasonic obstacle detection 
system, it was envisioned that a light signal response system would 
overcome the heretofore mentioned problem and provide a reliable and 
preferable solution to the problem since a light signal response system 
consisting of a transmitter and receiver would not be influenced by noise 
or other factory generated signals. This solution appeared to be 
successful. However, it was found that certain objects did not adequately 
reflect the light signal back to the receiver due to a weakness in the 
intensity of the light signal. The option of replacing a single 
transmitter and receiver with several fixedly mounted transmitters and 
receivers of a substantially higher intensity and narrow beam width was 
considered, but found impractical due to space and cost limitations. 
It is necessary, therefore, to provide a transceiver arrangement capable of 
sensing the presence of an object in front of the work vehicle in all 
potential operating environments and in a simple and low cost manner. 
DISCLOSURE OF THE INVENTION 
In one aspect of the present invention, a work vehicle having a frame, an 
end portion, first and second spaced apart sides, and a longitudinal 
vehicle axis is provided. A first transceiver assembly has a transmitting 
portion which is adapted to deliver a first light signal having a central 
axis, and a receiving portion which is adapted to receive a reflection of 
the first light signal. A second transceiver assembly has a transmitting 
portion which is adapted to deliver a second light signal having a central 
axis, and has a receiving portion which is adapted to receive a reflection 
of the second light signal. A first pivotal connecting device pivotally 
connects the first transceiver assembly to the frame at a first location 
adjacent the frame end portion for pivotal movement about a first axis, 
and a second pivotal connecting device pivotally connects the second 
transceiver assembly to the frame at a second location adjacent the frame 
end portion and frame second side for pivotal movement about a second 
axis. A powering device reciprocally moves the first transceiver assembly 
about the first axis between a first position at which the first light 
signal central axis extends outwardly from the frame end portion at a 
diverging angle "A" relative to a plane lying along and extending 
elevationally from the longitudinal vehicle axis, and a second position 
angularly spaced from the first position at which the first light signal 
central axis extends outwardly from the frame end portion at a converging 
angle "B" relative to the plane lying along and extending elevationally 
from the longitudinal vehicle axis. A tie device connects the first 
transceiver assembly to the second transceiver assembly and reciprocally 
moves the second transceiver assembly about the second axis between a 
third position at which the second light signal central axis extends in an 
outwardly direction from and relative to the frame end portion at a 
converging angle "C" relative to said plane lying along and extending 
elevationally from the longitudinal vehicle axis, and a fourth position 
angularly spaced from the third position at which the first light signal 
central axis extends in an outwardly direction from and relative to the 
frame end portion at a diverging angle "D" relative to the plane lying 
along and extending elevationally from the longitudinal axis. 
In another aspect of the present invention, a material handling vehicle has 
a frame which has an end portion, opposed first and second spaced apart 
sides connected to the end portion, and a longitudinal vehicle axis 
extending along the frame and passing through the end portion. A first 
shaft is connected to the frame at a first location adjacent the end 
portion and first side of the frame, and a second shaft is connected to 
the frame at a second location adjacent the second end portion and second 
side of the frame. A first bracket has a base portion and a first arm 
portion which is connected to extend from the first bracket base portion, 
and a second bracket has a base portion and a first arm portion which is 
connected to extend from the second bracket base portion. First and second 
transceiver assemblies each have a light signal transmitting portion and a 
reflected light receiving portion. The first transceiver assembly light 
transmitting portion is adapted to deliver a first light signal having a 
central axis, and the first transceiver assembly light receiving portion 
is adapted to receive a reflection of the first light signal, and the 
second transceiver assembly light transmitting portion is adapted to 
deliver a second light signal having a central axis, and the second 
transceiver assembly light receiving portion is adapted to receive a 
reflection of the second light signal. An adjusting device pivotally 
connects the first transceiver assembly to the first bracket first arm 
portion and the second transceiver assembly to the second bracket first 
arm portion. The adjusting device maintains the first and second 
transceiver assemblies each at a selected one of a plurality of pivoted 
angular positions relative to a common plane passing substantially 
normally through the first and second shafts. A linkage arrangement 
connects a rotary output shaft of an electric motor to the first bracket 
and pivotally and reciprocally moves the first bracket about the first 
shaft between a first position at which the first light signal central 
axis projects outwardly from the first transceiver assembly at a diverging 
angle "A" relative to a plane lying along and extending vertically from 
the longitudinal vehicle axis, and a second position angularly spaced from 
the first position at which the first light signal central axis extends 
outwardly from the second transceiver assembly at a converging angle "B" 
relative to the plane lying along and extending vertically from the 
longitudinal vehicle axis. The first bracket is pivotally movable between 
the first and second positions in response to rotary movement of the 
output shaft. A tie rod is pivotally connected to and between the first 
and second brackets and is adapted to pivotally move the second bracket 
about the second shaft between a third position and a fourth position 
angularly spaced from the third position in response to pivotal movement 
of the first bracket between the first position and the second position. 
The second light signal central axis projects outwardly from the second 
transceiver assembly at a converging angle "C" relative to the plane lying 
along and extending vertically from the longitudinal vehicle axis at the 
third position, and the second light signal central axis projects 
outwardly from the second transceiver assembly at a diverging angle "D" 
relative to the plane lying along and extending vertically from the 
longitudinal vehicle axis at the fourth position.

BEST MODE FOR CARRYING OUT THE INVENTION 
With reference to the drawings, a work vehicle 10 has a frame 12 which has 
first and second spaced apart sides 14,16, and an end portion 18. The 
first and second sides 14,16 are connected to the end portion 18 at spaced 
apart locations on the end portion and define a substantially 
rectangularly configured frame 12. A tower portion 20 which houses a 
controller (not shown) is connected adjacent the end portion 18 of the 
frame 12 and extends in an elevational direction upwardly from the frame 
12. A pair of openings 24 is disposed in the tower at a location adjacent 
the end portion 18. Preferably, the openings 24 are each closely adjacent 
the first and second frame sides 14,16. A source of electrical energy 26, 
in the form of a storage battery, is provided for supplying electrical 
energy needs of the vehicle. A platform 28 or other load carrying 
implement, for example, a lift mast and the like (not shown), is connected 
to the frame 12 in any suitable manner. A plurality of vehicle wheels 30 
enable the vehicle to be propelled over the ground in any conventional and 
suitable manner. Although the particular work vehicle shown is an AGV 
(automatic guided vehicle), it is to be understood that other types of 
work vehicles, manned or unmanned, are to be considered as suitable fields 
of equivalent use. 
An oscillating scanner arrangement 32 having first and second spaced apart 
transceiver assemblies 34,36 is provided for identifying an object in the 
path of the work vehicle 10 and deliver a signal to the controller in 
response to positive identification of an object in the path of the work 
vehicle 10. The first transceiver assembly 34 is disposed in one of the 
openings 24, and the second transceiver assembly 36 is disposed in the 
other of the openings 24. 
Referring to FIGS. 2 and 4, the first transceiver assembly 34 has a 
transmitting portion 38 and a receiving portion 40. The first transceiver 
transmitting portion is adapted to deliver a first light signal which has 
a central axis 42, and the first transceiver receiving portion 40 is 
adapted to receive a reflection of the first light signal. Similarly, the 
second transceiver assembly 36 has a transmitting portion 44 and a 
receiving portion 46. The second transceiver transmitting portion 44 is 
adapted to deliver a second light signal having a central axis 48. The 
second transceiver receiving portion 46 is adapted to receive a reflection 
of the second light signal. The first and second transceiver assemblies 
34,36 preferably include Visolux, Model LT2000, Reflection Light Scanners. 
These scanners are self contained, focused beam, photoelectric controls 
which will detect all objects, regardless of texture and color, within the 
scanning field. Objects in the background, beyond the upper scanning 
limits of the device, will not be detected. The unit utilizes an LED to 
transmit a visible beam of modulated Infra-Red light at the object to be 
detected. Provided the object is within the scanning field, the receiver 
system will detect the light reflected from it. 
A first means 50 (FIG. 3) is provided for pivotally connecting the first 
transceiver assembly 34 to the frame 12 at a first location adjacent the 
frame end portion 18 and the frame first side 14. The first means 50 
preferably includes a first bracket 52 and a first shaft 54 which is 
rigidly connected to the first bracket, for example, by splines or a 
tapered portion on shaft 54. The first shaft 54 is pivotally connected to 
the frame 12 at the first location and defines a first axis 56. The first 
transceiver assembly 34 is mounted on the first bracket 52 and pivotally 
movable about the first axis 56. 
A second means 58 is provided for pivotally connecting the second 
transceiver assembly 36 to the frame 12 at a second location spaced from 
the first location and adjacent the frame end portion 18 and the frame 
second side 16. The second means 58 preferably includes a second bracket 
60 and second shaft 62 which is securely connected to the second bracket 
60, for example, by splines or tapered portion on shaft 62. The second 
transceiver assembly 36 is mounted on the second bracket 60 and pivotally 
movable about a second axis 64. The first and second axis 56 and 64 of the 
first and second shafts 54 and 62, respectively, are parallel to one 
another and extend in an elevational direction from a support member 68 
which is connected to the frame 12. Preferably, the first and second 
shafts 54,62 are normal to surface 66 of support member 68. 
Referring to FIGS. 2 and 4, a power means 70 is provided for reciprocally 
moving the first transceiver assembly 34 about the first axis 56 between a 
first position 72 at which the first light signal central axis extends 
outwardly from the frame end portion 18 at a diverging angle "A" of 
approximately 34 degrees relative to a plane 74 lying along, passing 
through, and extending elevationally from a longitudinal vehicle axis 76, 
and a second position 78 angularly spaced from the first position 72 at 
which the first light signal central axis 42 extends outwardly from the 
frame end portion 18 at a converging angle "B" of approximately 34 degrees 
relative to plane 74. A tie means 80 connects the first transceiver 
assembly 34 to the second transceiver assembly 36 and reciprocally moves 
the second transceiver assembly 36 about the second axis 64 between a 
third position 82 at which the second light signal central axis 48 extends 
in an outward direction from and relative to the frame end portion 18 and 
at a converging angle "C" at approximately 34 degrees relative to plane 
74, and a fourth position 84 angularly spaced from the third position 82 
at which the second light signal central axis 48 extends outwardly from 
the frame end portion at a diverging angle "D" of approximately 34 degrees 
relative to plane 74. Surface 66 of support member 68 is preferably normal 
to plane 74 and parallel to longitudinal axis 76. 
An adjusting means 86 (FIGS. 2 and 5) pivotally connects the first 
transceiver assembly 34 to the first bracket 52 and the second transceiver 
assembly 36 to the second bracket 60 and maintains the first and second 
transceiver assemblies 34,36 each at a selected one of a plurality of 
pivoted angular positions relative to a plane 88 passing substantially 
normally through each of the first and second shafts 54,62. The plane 88 
is parallel to the surface 66 of support member 68 and normal to plane 74 
which passes through the vehicle axis. The first bracket 52 has a base 
portion 90 and first and second spaced apart arm portions 92,94 connected 
to the base portion 90 at spaced apart locations and extends from the base 
portion 90 in preferably an elevational direction. Likewise, the second 
bracket 60 has a base portion 96 and first and second spaced apart arm 
portions 98,100 which are connected to the base portion 96 at spaced apart 
locations thereon and which extend therefrom in preferably an elevational 
direction. The base portion 90 is connected to the first shaft 54, and the 
base portion 96 is connected to the second shaft 62. 
Adjusting means 86 includes first and second adjustment means 102,104. The 
first adjustment means 102 pivotally connects the first transceiver 
assembly to the support member 68 and maintains the first transceiver at 
the selected one of a plurality of angular locations relative to and 
spaced from the support member surface 66, and the second adjustment means 
104 pivotally connects the second transceiver assembly 36 to the support 
member 68 and maintains the second transceiver assembly 36 at a selected 
one of a plurality of angular locations relative to and spaced from the 
support member surface 66. Specifically, the first adjustment means 102 
includes a first cross shaft 106 which pivotally connects the first 
transceiver assembly 34 to the first and second arm portions 92,94 of the 
first bracket 52, a first arcuate slot 108 disposed in the first arm 
portion 92 and a third arcuate slot 110 disposed in the second arm portion 
94. A first fastener 112 is connected to the first transceiver assembly 
34, disposed in the first arcuate slot 108, and forcibly engageable with 
the first arm portion 92, and a third fastener 114 is connected to the 
first transceiver assembly 34, disposed in the third arcuate slot 110, and 
forcibly engageable with the second arm portion 94 of the first bracket 
52. It is to be noted that the arcuate slots 108,110 are defined by a 
radius pivoted about an axis of the first cross shaft 106. The first and 
second arcuate slots 108,110 each have a branch slot 116 extending 
therefrom to permit disengagement of the first transceiver assembly 34 
from connection with the first bracket 52. 
The second adjustment means 104 includes a second cross shaft 118 which 
pivotally connects the second transceiver assembly 36 to the first and 
second arm portions 98,100 of the second bracket 60, a second arcuate slot 
120 disposed in the first arm portion 98 of the second bracket 60 and a 
fourth arcuate slot 122 disposed in the second arm portion 100 of second 
bracket 60. A second fastener 124 is connected to the second transceiver 
assembly 36, disposed in the second arcuate slot 120, and forcibly 
clampingly engageable with the first arm portion 98, and a fourth fastener 
126 connected to the second transceiver assembly 36, disposed in the 
second arcuate slot 120, and forcibly clampingly engageable with the 
second arm portion 100 of the second bracket 60. Branch slot 116 is also 
provided in the first and second arm portions 98,100 of the second bracket 
60 to permit removal of the second transceiver assembly 36 from connection 
with the second bracket 60. 
Referring to FIGS. 2 and 5, a first housing 128 is provided to connect the 
first transceiver assembly 34 to the first bracket 52, and a second 
housing 130 is provided for connecting the second transceiver assembly 36 
to the second bracket 60. The first housing 128 has an opening 132 of 
preferably an elongate configuration disposed therein, and a pair of 
projections 134 extending from the housing in a common direction. The 
first transceiver assembly 34 is disposed in and connected to the first 
housing, and the first transceiver transmitting and receiving portions 
38,40 are disposed in the opening 132 and adapted to pass and receive 
light therethrough. The second housing 130 similarly has an opening 136 of 
preferably an elongate configuration disposed therein, and a pair of 
projections 138 connected to and extending from the housing in a common 
direction. The second transceiver assembly 36 is disposed in and connected 
to the second housing 130 in any suitable manner. The second transceiver 
transmitting and receiving portions 44,46 are disposed in the opening and 
adapted to pass and receive light therethrough. The first cross shaft 106 
is connected to the pair of projections 134 of the first housing 128, and 
the second cross shaft 118 is connected to the pair of projections 138 of 
the second housing 130. The projections 134,138 are pivotably movable 
about the first and second cross shafts 106,118, respectively. 
The first and third fasteners 112,114 are connected in any suitable manner 
to the first housing 128 at spaced apart locations on the housing 128 and 
project from the housing 128 in opposed directions so that they may be 
positioned in the first and third arcuate slots 108,110, respectively. 
Similarly, the second and fourth fasteners 124,126 are connected to the 
second housing 130 at spaced apart locations on the housing 130 and extend 
from the second housing 130 in opposite directions so that they may be 
disposed in the second and fourth arcuate slots 120,122, respectively. The 
first and second housings 128,130 have a channel shaped configuration, and 
the fasteners extend from opposed sides of the channel member. Each of the 
fasteners 112,114,124,126 have a nut 140 screwthreadably connected thereto 
and adapted to forcibly engage the respectively adjacent arm portions 
92,94,98,100 of the first and second brackets 52,60 and clampingly engage 
the arm portions 92,94,98,100 against the respective first and second 
housings 128,130. Thus, it can be seen that the first adjusting means 102 
maintains the first transceiver assembly 34 at a selected one of a 
plurality of pivoted angular positions relative to and in a plane normal 
to the plane 88, and the second adjustment means 104 maintains the second 
transceiver assembly 36 at a selected one of a plurality of pivoted 
angular positions relative to and in a plane normal to plane 88. The first 
and second cross shafts 106,118 are preferably parallel to plane 88, and 
the projections 134,138 of the first and second housings 130,132, 
respectively, are perpendicular to the first and second cross shafts 
106,118, respectively. 
The tie means 80, as best shown in FIG. 2, includes a tie rod 142 having 
first and second spaced apart end portions 144,146, a first lever arm 148 
connected to and extending from the first bracket 52 at the base portion 
90, and a second lever arm 150 connected to and extending from the base 
portion 96 of the second bracket 60. A fastener 152 of any suitable 
configuration pivotally connects each of the first and second spaced apart 
end portions 144,146 to the first and second lever arms 148,150, 
respectively. Although the lever arms 148,150 are shown as integral parts 
of the first and second brackets 52,60, other configurations to achieve 
equivalent results are contemplated and within the scope of the invention. 
The tie rod 142 is adapted to pivotally move the second bracket 60 about 
the second axis 64 between the heretofore mentioned third and fourth 
positions 82,84 in response to pivotal movement of the first bracket 
between the first position 72 and the second position 78. The second 
bracket 60 is preferably at the third position 82 in response to the first 
bracket 52 being at the first position 72, and the second bracket 60 is at 
the fourth position 84 in response to the first bracket 52 being at the 
second position 78. 
Referring to FIGS. 2 and 3, the power means 70 includes an electric motor 
154 drivingly connected to a rotary output shaft 156, such as by a 
transmission 157. Linkage means 158 connects the rotary output shaft 156 
to first bracket 52 and pivotally and reciprocally moves the first bracket 
52 about the first axis 56 between said first and second positions 72,78 
in response to rotary motion of output shaft 156. 
The linkage means 158 includes a first link 160 having first and second 
spaced apart end portions 162,164, a second link 166 having first and 
second spaced apart end portions 168,170, and a third link 172 having 
first and second spaced apart end portions 174,176. The first link first 
end portion 162 is connected to the rotary output shaft and rotatable with 
the rotary output shaft 156. The second link second end portion 170 is 
connected to the first shaft 54 and rotatable with the first shaft 54. The 
third link first end portion 174 is pivotally connected to the first link 
second end portion 164, and the third link second end portion 176 is 
pivotally connected to the second link first end portion 168. Each of 
these pivotal connections are made in any suitable and conventional manner 
such as by a pivot pin of well-known construction. Power means 70 is 
secured to the vehicle frame 12 at a location adjacent the first shaft 54 
so that the length of the second and third links 160,166,172 is kept to a 
minimum. Preferably, the power means 70 is removably secured to the 
vehicle frame 12 via threaded fasteners. The support member 68 is 
preferably first and second spaced apart gussets 178,180. The first gusset 
178 is connected, such as by welding, to the frame first side 14 and frame 
end portion 18, and the second gusset 180 is connected, such as by 
welding, to the frame second side 16 and frame end portion 18. The first 
shaft 54 is rotatably connected relative to the first gusset 178, and the 
second shaft 62 is rotatably connected relative to the second gusset 180. 
The first transceiver transmitting portion 38 is elevationally spaced from 
the first transceiver receiving portion 40, and the second transceiver 
transmitting portion 44 is spaced elevationally from the second 
transceiver receiving portion 46. Because the first and second transceiver 
assemblies pivotally move about the first and second axes 56,64, it is 
important that the transmitting and receiving portions lie above one 
another so that there will be no false signals due to either a lag or a 
lead of the reflective light beam caused by this motion. Although not 
shown, the first and second transceiver assemblies 34,36 and the electric 
motor 154 are connected to the source of electrical energy 26 in a manner 
as to provide power for operation thereof. 
Industrial Applicability 
With reference to the drawings, the oscillating scanner arrangement 32 
provides a unique, low cost, efficient, and highly accurate way of 
detecting objects in the path of movement of vehicle 10. In operation, 
electrical current is delivered from the battery 26 to the first and 
second transceiver assemblies 34,36 and electric motor 154. This current 
causes the transmitting portions 38,44 to deliver a light signal, having 
an intense beam of narrow width, from the vehicle 10 in a direction 
substantially in the path of movement of the vehicle 10. The electrical 
current also activates the receiving portions 40,46 of the first and 
second transceiver assemblies 34,36 and conditions the transceiver 
assemblies to deliver a signal in response to the receiving portions 40,46 
being turned on by the reflected light. The electric motor 154 is 
responsive to the controller, not shown to rotate output shaft 156 at a 
preselected speed. The speed of rotation of the motor is selected as a 
function of the width of the vehicle, the speed of the vehicle, and the 
scanning range of the first and second transceiver assembly 34,36. The 
desired range of the light signal for a typical AGV application is in the 
vicinity of two meters (6.5 feet). 
Rotation of output shaft 156 is converted to reciprocating or oscillating 
motion and delivered to the first shaft 54 by linkage means 158. Because 
the first shaft 54 is connected to the rotary output shaft 156 by links 
160,166,172, reciprocating motion of the first shaft 54 will be limited to 
a preselected amount of angular rotation established by the relative 
lengths of the first and second links 160,166. Preferably, the amount of 
rotation of the first shaft 54 will enable the light beam of a first 
transceiver assembly 34 to cover a range of pivotal motion equal to at 
least one half the distance between the first and second sides 14,16 of 
frame 12 within the scanning range of the light beam. 
As the first transceiver assembly 34 pivots about the first axis 56 between 
the first and second positions 72,78, the tie means 80 moves the second 
transceiver assembly 36 about the second axis 64 between the third and 
fourth positions 82,84. The angle of pivotal movement selected between the 
third and fourth positions 82 and 84 will enable the light beam of the 
second transceiver assembly 36 to cover at least one half the distance 
between the first and second sides 14 and 16. Therefore, the entire width 
of the vehicle is scanned in the path of the vehicle 10 from side to side 
of the vehicle 10. 
The adjusting means 86 enables the first and second transceiver assemblies 
34,36 to be aligned so that the central axis 42 of the first light signal 
and the central axis 48 of the second light signal are directed at 
substantially the same elevationally oriented angle relative to plane 88. 
Preferably, the first and second transceiver assemblies will be at an 
elevationally oriented angle relative to plane 88 at which the light 
signals will be able to identify an object in the path of the vehicle of 
various sizes and locations relative to the surface on which the vehicle 
operates. Theoretically, central axis 42 and 48 should be directed at an 
imaginary target having a minimum height of 152.4 mm, (0.5 ft) at the 
maximum scanning range of approximately two meters (6.5 feet) from the 
transceiver assemblies 34,36. To align the assemblies, one must first 
release the first, second, third, and fourth fasteners 112,114,124,126 and 
pivot the first and second transceiver assemblies about the cross shafts 
106,118 until the desired positions are obtained. Nuts 140 are then screw 
threadably rotated into engagement with the first and second brackets 
52,60. The transceivers as a result are retained by the clamping force of 
the nuts 140 against the brackets 52,60. 
The tie means 80 not only transfers oscillating motion from the first 
transceiver assembly 34 to the second transceiver assembly 36 but also 
provides for a limited amount of adjustment so that the central axes 42 
and 48 are parallel to each other. The adjustment is made at the first and 
second end portions 144,146 of the tie rod 142 through fastener 152 which 
pivotally connects the first and second lever arms 148,150 to the tie rod 
142. 
As vehicle 10 traverses the underlying surface, the first and second 
transceiver assemblies 34,36 sweep about the first and second axes 56,64 
between the first and second positions 72,78 and third and fourth 
positions 82,84 in response to rotary motion of the output shaft 156. 
Objects in the path of the vehicle will reflect the light signals directed 
by the first and second transmitting portions 38,44 back to the respective 
ones of the first and second receiving portions 40,44. Upon receipt of the 
reflected signal, the first and second transceiver assemblies 34,36 will 
deliver a control signal to a control unit (not shown) which will cause 
the vehicle to take further action. Such action includes, for example, a 
reduction in the speed of the vehicle followed by vehicle braking. 
It should be noted that the second transceiver assembly 36 is at the third 
position 82 when the first transceiver assembly 34 is at the first 
position 72, and at the fourth position 84 when the first transceiver 
assembly 34 is at the second position 78. This motion enables the vehicle 
to ensure that the full field in front of the vehicle is scanned. Because 
the oscillating scanner arrangement 32 utilizes light emitting 
transceivers with relatively narrow width beams of relatively high 
intensity, the problems heretofore mentioned have been eliminated. By 
oscillating the transceivers 34,36, it is possible to fully cover the path 
of travel of the vehicle 10 without requiring additional transceiver 
assemblies, thus making usage feasible from a cost and space standpoint. 
Other aspects, objects, and advantages of this invention can be obtained 
from a study of the drawings, the disclosure, and the appended claims.