U.S. patent number 3,727,332 [Application Number 05/200,893] was granted by the patent office on 1973-04-17 for laser guidance system for grade control.
Invention is credited to Walter George A. Zimmer.
United States Patent |
3,727,332 |
Zimmer |
April 17, 1973 |
LASER GUIDANCE SYSTEM FOR GRADE CONTROL
Abstract
A vehicular machine, such as a trencher, having working means,
such as a digging wheel, carried thereon for working material to a
desired grade as the machine moves along a given path. Vertical
adjustment of the working means is automatically controlled by a
laser guidance system mounted on the machine for movement
therewith. The guidance apparatus includes a reference means, such
as a shoe of a trencher, movable with the machine and which engages
the surface of the material already worked to the desired grade by
the machine. The guidance apparatus also includes a detector
apparatus comprising a laser beam generator mounted on a
stabilizing platform and a beam sensor remote therefrom but
enclosed within the same housing, the housing being carried by the
framwwork of the working implement of the machine. The stabilized
laser is preferably located in close proximity to the reference
means with the beam aimed generally in the plane of motion of the
working implement relative to the machine. Deviations of the
working means from the desired grade are sensed by relative motion
between the beam and sensor to develop a control signal utilized by
a hydraulically actuated hoisting mechanism to raise or lower the
working means to thus correct for such deviations and thereby
maintain the material being worked at the desired grade as the
machine moves along said path.
Inventors: |
Zimmer; Walter George A.
(Chatham, Ontario, CA) |
Family
ID: |
22743647 |
Appl.
No.: |
05/200,893 |
Filed: |
November 22, 1971 |
Current U.S.
Class: |
37/97; 33/625;
56/DIG.15; 172/4.5; 299/1.5; 37/907 |
Current CPC
Class: |
E02F
3/18 (20130101); E02F 5/145 (20130101); E02F
3/181 (20130101); E02F 9/2045 (20130101); Y10S
56/15 (20130101); Y10S 37/907 (20130101) |
Current International
Class: |
E02F
9/20 (20060101); E02F 5/02 (20060101); E02F
5/14 (20060101); E02F 3/18 (20060101); E02f
005/08 () |
Field of
Search: |
;172/4.5,4
;37/80,97,DIG.20 ;299/1 ;94/46AC ;33/185V ;56/DIG.15 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pulfrey; Robert E.
Assistant Examiner: Crowder; Clifford D.
Claims
I claim:
1. A machine for working material to a desired grade along a given
path in, on or over terrain comprising a vehicle for moving upon
said grade, working means carried by said vehicle for working the
material to the desired grade as the vehicle moves on the terrain
along the given path, said working means being vertically
adjustable relative to said vehicle, reference means movable with
the machine and adapted to engage with the surface of the material
worked on by said working means at a location wherein the surface
of the material has been worked to substantially the desired grade
by said working means, generator means for producing a beam of
radiant energy in the general direction of travel of said working
means, sensor means spaced from said generator means and adapted to
sense said beam of radiant energy, first carrier means carrying one
of said generator means and said sensor means in a given
relationship with said reference means for generally vertical
movement therewith, second carrier means carrying the other of said
generator means and said sensor means in a given relationship with
said working means for generally vertical movement therewith,
stabilizing means for maintaining the beam of radiant energy
produced by said generator means in a given stabilized attitude to
project in a plane generally parallel to the path of travel of said
working means, said sensor means being disposed generally
transversely to and intersecting said beam of radiant energy, said
sensor means detecting relative motion between said sensor means
and the point at which said beam of radiant energy strikes said
sensor means caused by relative generally vertical movement between
said reference means and said working means and generating a signal
indicative of vertical deviation of said working means from the
desired grade, and control means responsive to said signal to
adjust said working means generally vertically to correct for said
deviation such that the material being worked remains at the
desired grade as said working means is moved by said vehicle along
the path of travel of the grade.
2. The machine of claim 1 wherein said generator means comprises a
laser light source.
3. The machine of claim 1 wherein said stabilizing means comprises
a gimbal having a first axis of rotation extending generally
parallel to the beam of radiant energy produced by said generator
means and a second axis of rotation extending generally
horizontally and transversely to said first axis of rotation, said
generator means being carried by said gimbal, and a pendulum weight
rigidly connected with said generator means for pivotal movement
therewith on said second axis of said gimbal with the combined
center of gravity of said generator means and said pendulum weight
being generally vertically below said second axis of said
gimbal.
4. The machine of claim 3 wherein the point of intersection of said
first and second axes of said gimbal is generally on a vertical
center line from the point at which said reference means engages
the material worked on by said working means.
5. The machine of claim 3 which also comprises means connecting
said pendulum weight with said second carrier such that the angular
relationship between said second carrier and said pendulum weight
can be adjusted.
6. The machine of claim 1 wherein said sensor means is mounted for
rotational movement in a plane generally transverse to said beam of
radiant energy on an axis generally parallel thereto.
7. The machine of claim 1 wherein said sensor means is mounted to
pivot on a generally horizontal axis generally transverse to said
beam of radiant energy and the center of gravity of said sensor
means is generally vertically below said generally horizontal
rotational axis.
8. The machine of claim 1 wherein said generator means is in a
given relationship with said reference means for movement therewith
and said sensor means is in a given relationship with said working
means for movement therewith.
9. The machine of claim 1 wherein said working means comprises a
digging wheel having a plurality of circumferentially spaced
buckets thereon adapted to produce when rotated, a trench having a
bottom surface in the terrain, and said reference means comprises a
shoe adapted to be received in said trench behind said digging
wheel and to bear on said bottom surface of said trench.
10. The machine of claim 9 which also comprises an enclosure having
a rigid hollow tube, a sensor housing connected to said tube
adjacent one end thereof, and a generator housing connected to said
tube adjacent the other end thereof with said sensor means mounted
in said sensor housing and said generator means mounted in said
generator housing such that said beam of radiant energy produced by
said generator means passes through said hollow tube and impinges
on said sensor means.
11. The machine of claim 10 in which said first carrier means
comprises means pivotally mounting said generator housing on said
shoe and said second carrier means comprises generally vertically
adjustable means mounting said enclosure adjacent said one end of
said tube in an adjustable given relationship to the axis of
rotation of said digging wheel.
12. The machine of claim 1 wherein said working means comprises a
rigid frame pivotally connected adjacent one end thereof to said
vehicle and a digging wheel mounted on said frame for rotation
thereon and having a plurality of circumferentially spaced buckets
adapted to dig a trench having a bottom surface when said wheel is
rotated in the terrain, and said reference means comprising a shoe
positioned behind said digging wheel and fixed to said frame, said
shoe being adapted to be received in the trench produced by said
digging wheel and to bear on the bottom surface of said trench with
said shoe, frame and digging wheel being adapted to be pivoted in
the trench about a point adjacent the trailing lower edge of said
shoe as said one end of said frame is raised and lowered to control
the grade of the bottom surface of the trench produced by the
digging wheel, said generator means being carried by said first
carrier means so that the point from which said beam of radiant
energy eminates from said generator means lies generally vertically
over said pivot point adjacent the lower trailing edge of said
shoe.
13. The machine of claim 1 which also comprises a detector
apparatus enclosure having a rigid hollow tube, a sensor housing
connected to said tube adjacent one end thereof, and a generator
housing connected to said tube adjacent the other end thereof with
said sensor means mounted in said sensor housing and said generator
means mounted in said generator housing such that said beam of
radiant energy produced by said generator means passes through said
hollow tube and impinges on said sensor means.
14. The machine of claim 13 which also comprises means mounting
said sensor means in said sensor housing for adjustment of said
sensor means generally transversely to said beam of radiant energy
comprising a slide, an adjustment screw operably connected with
said slide and being adapted to be manually rotated externally of
said sensor housing to generally vertically reciprocate said slide
within said sensor housing, and gimbal means carried by said slide
with said sensor means mounted on said gimbal means.
15. The machine of claim 1 wherein said sensor means comprises at
least two photocells producing said electric signal indicative of
vertical deviation of said working means from the desired grade,
and said control means responsive to said electric signal comprises
a hydraulic cylinder with a ram therein operably connected with
said working means for vertically adjusting the position of said
working means relative to said vehicle, an electro-hydraulic
control valve adapted for selectively directing a hydraulic fluid
under pressure into said cylinder to move said ram in said
cylinder, and electric circuitry utilizing said electric signal of
said sensor means to actuate and control said electro-hydraulic
valve to direct hydraulic fluid under pressure into said cylinder
to move said ram to adjust said working means to correct for said
deviation of said working means from the desired grade as said
working means is moved by said vehicle along the path of travel of
the grade.
16. A guidance system for controlling a working means carried by a
machine for working a material to a desired grade as the machine
travels along a given path by adjusting the working means relative
to the machine, and said machine having a reference means movable
with the machine and adapted to engage with the surface of the
material previously worked to the desired grade by said working
means, said guidance system comprising generator means for
producing a beam of radiant energy generally in the direction of
travel of the working means, stabilizing means for maintaining the
beam of radiant energy produced by said generating means in a given
stabilized attitude to project in said direction of travel of the
working means, said stabilizing means being adapted for mounting in
a given relationship with one of said working means and said
reference means, sensor means extending generally transverse to and
intersecting the beam of radiant energy produced by said generating
means, said sensor means being spaced from said generating means
and adapted for mounting in a given relationship with the other one
of said working means and said reference means, said sensor means
detecting relative motion between said sensor means and the point
at which the beam of radiant energy impinges on said sensor means
caused by relative movement between said reference means and said
working means to produce an electric control signal indicative of
deviation of said working means from the desired grade, whereby
said electric control signal can be utilized to adjust said working
means relative to the machine such that the material is worked to
the desired grade as the working means is moved by the machine.
17. The guidance system of claim 16 wherein said generator means
comprises a laser light source.
18. The guidance system of claim 17 wherein said stabilizing means
comprises a gimbal having a first carrier adapted for rotation on
an axis generally parallel to the beam of radiant energy produced
by said laser light source and a second carrier mounted for
rotation on said first carrier on an axis generally transverse to
said axis of rotation of said first carrier, said laser light
source being mounted on said second carrier for rotation therewith
with the point from which the beam of radiant energy eminates
generally coincident with the point of intersection of the axes of
rotation of said first and second carriers, and a pendulum weight
fixed to said second carrier such that the center of gravity of the
combined laser light source, second carrier and pendulum weight is
generally vertically below the point of intersection of the axis of
said first and second carriers.
19. The guidance system of claim 18 which also comprises a
container receiving said pendulum weight therein and adapted to
retain a liquid therein whereby the pivotal movement of said
pendulum about the axes of said first and second carriers is
dampened by the liquid.
20. The guidance system of claim 18 which also comprises means
connecting said pendulum weight with said second carrier such that
the angular relationship between said second carrier and said
pendulum weight can be adjusted.
21. The guidance system of claim 17 wherein said sensor means
comprises at least one photovoltaic cell.
22. The guidance system of claim 16 which also comprises means
mounting said sensor means so that said sensor means can rotate on
an axis generally parallel to the beam of radiant energy produced
by said generator means.
23. The guidance system of claim 16 which also comprises means
mounting said sensor means so that it can rotate on a first axis
generally parallel to the beam of radiant energy produced by said
generator means and can also rotate on a second axis generally
transverse to the beam of radiant energy produced by said generator
means and in which the center of gravity of said sensor means is
generally vertically below the point of intersection of said first
and second axes of rotation of said means for mounting said sensor
means.
24. The guidance system of claim 17 which also comprises an
enclosure having a rigid hollow tube, a sensor housing connected to
said tube adjacent one end thereof, and a generator housing
connected to said tube adjacent the other end thereof, with said
sensor means mounted in said sensor housing and said generator
means mounted in said generator housing such that said beam of
radiant energy produced by said generator means passes through said
hollow tube and impinges on said sensor means.
25. The guidance system of claim 16 wherein said sensor means
comprises at least two photocells producing said electrical control
signal indicative of vertical deviation of said working means from
the desired grade and the guidance system also comprises electric
circuitry utilizing said electric control signal of said sensor
means to actuate and control an electro-hydraulic valve of the
machine to direct hydraulic fluid under pressure into a fluid motor
of the machine to adjust the working means to correct for said
deviation of said working means from the desired grade as the
machine travels along a given path such that the material is worked
to the desired grade.
26. A machine for working material to a desired grade along a given
path in, on or over terrain comprising a vehicle for moving upon
said grade, working means carried by said vehicle for working the
material to the desired grade as the vehicle moves on the terrain
along the given path, said working means being vertically
adjustable in a given plane of motion relative to said vehicle,
reference means movable with the machine and adapted to engage with
the surface of the material worked on by said working means at a
location wherein the surface of the material has been worked to
substantially the desired grade by said working means, generator
means for producing a beam of radiant energy in the general
direction of said motion plane, sensor means spaced from said
generator means and adapted to sense said beam of radiant energy,
first carrier means carrying one of said generator means and said
sensor means in a given relationship with said reference means for
generally vertical movement therewith, second carrier means
carrying the other of said generator means and said sensor means in
a given relationship with said working means for generally vertical
movement therewith, stabilizing means for maintaining the beam of
radiant energy produced by said generator means in a given
stabilized attitude to project in said motion plane, said sensor
means being disposed generally transversely to and intersecting
said beam of radiant energy, said sensor means detecting relative
motion between said sensor means and the point at which said beam
of radiant energy strikes said sensor means caused by relative
generally vertical movement between said reference means and said
working means and generating a signal indicative of vertical
deviation of said working means from the desired grade, and control
means responsive to said signal to adjust said working means
generally vertically to correct for said deviation such that the
material being worked remains at the desired grade as said working
means is moved by said vehicle along said given path.
27. The machine of claim 26 wherein said generator means comprises
a laser light source.
28. The machine of claim 27 wherein said stabilizing means
comprises pivot means having an axis of rotation extending
generally horizontally and transversely to said motion plane, said
generator means being carried by said pivot means, and a pendulum
weight rigidly connected with said generator means for pivotal
movement therewith on said axis with the combined center of gravity
of said generator means and said pendulum weight being generally
vertically below said axis.
Description
This invention relates to machines for grading material in, on, or
over terrain such as ditching, tunneling, grading and other similar
earth working machines, as well as paving machines and the like,
and more particularly to such machines with guidance systems for
controlling the grade or elevation of the material graded by such
machines.
Objects of this invention are to provide an improved machine for
grading material, and an improved control system for such a
machine, which automatically controls and adjusts the grading
implement of the machine during operation of the machine to
maintain the material being worked by the machine at a desired
predetermined grade.
Another object is to provide a machine and/or control system
therefor of the above character which is self-contained and does
not require any apparatus external to the machine and hence can be
ready and quickly set up and adjusted, operates automatically after
set up and adjustment, is rugged and durable, and produces within
close tolerances the desired grade .
These and other objects, features and advantages of this invention
will be apparent from the following description, appended claims
and accompanying drawings in which:
FIG. 1 is a side elevational view of a ditching machine with a
grade control including a detector apparatus embodying this
invention mounted on the machine.
FIG. 2 is an enlarged side elevational view of the detector
apparatus shown in FIG. 1.
FIG. 3 is a fragmentary isometric view of the detector apparatus
with portions broken away to illustrate a laser light source and
sensor units thereof.
FIGS. 4, 5 and 6 are side, end, and top views, respectively,
partially in section of the laser light source unit of the detector
apparatus.
FIG. 7 is a fragmentary side elevational view partially in section
of a modified form of the detector apparatus.
FIG. 8 is a fragmentary vertical sectional view taken on line 8--8
of FIG. 7.
FIG. 9 is a schmatic diagram of the electric circuitry of the
detector apparatus and the associated hydraulic system of the
ditching machine.
Referring in more detail to the drawings, FIG. 1 illustrates a
ditching machine 20 comprising a conventional six-wheel tractor
vehicle 22 and a trenching unit 24 towed by tractor 22. Trenching
unit 24 has a rigid frame 26 with a digging wheel 28 mounted for
rotation thereon about an axis 28' and a shoe 30 rigidly fixed
thereto. Digging wheel 28 has a plurality of buckets or scoops 31
mounted thereon and is rotated via a chain drive 32 through a power
take-off unit 33 of vehicle 22 to dig a trench 34 in terrain 36 as
vehicle 22 moves over the terrain along the desired path of trench
34. The material removed by scoops 31 is dumped in a conveyor 35
which carries the material laterally away from digging wheel 28.
Shoe 30 rides along the bottom surface 38 of trench 34 to iron out
and smooth the bottom surface and is stabilized in the trench by a
small fin 40 at its trailing edge. The grade or elevation of bottom
surface 38 of trench 34 is varied and controlled by raising and
lowering the front end of frame 26 so that trencher unit 24 pivots
in an upright plane about pivot point 41 at the trailing bottom
edge of shoe 30. The forward end of frame 26 is raised and lowered
by a conventional hydraulic ram and cable mechanism 42 fixed to
tractor 22. The forward end of frame 26 is pivotally connected to a
saddle 44 slidably received on a pair of horizontally spaced and
generally vertically extending rails or ways 46 rigidly fixed to
the rear of the frame of tractor 22. Digging machine 20 including
trencher unit 24 as thus far described is conventional and well
known in the prior art and thus will not be described in further
detail.
The control system of machine 20 embodying this invention for
automatically controlling the grade or elevation of bottom surface
38 of trench 34 has a detector apparatus 50 mounted on trencher
unit 24. As shown in FIG. 2, detector apparatus 50 has a laser
light source 52 mounted on a carrier plate 54 rigidly fixed through
end plate 55 to one end of a long hollow tube 56. A sensor unit 58
is mounted in a closure 60 rigidly fixed to the other end of tube
56. A cabinet 62 with a control panel 64 is mounted exteriorly on
tube 56. A removable cover 66 overlies carrier plate 54 and is
releasably fastened thereto to enclose source 52. Source 52
comprises a conventional laser unit which generates a beam of
highly coherent monochromatic light represented by broken line 68
which passes through tube 56 and impinges on sensor unit 58.
Generally rectangular apertures 67 and 69 are provided in end plate
55 and sensor housing 60 respectively to allow light beam 68 to
pass through tube 56 and strike sensor unit 58. Light beam 68 is
slightly diffused by a suitable lens system 70 (FIG. 3) of source
52 so that beam 68 impinges on sensor unit 58 in a small, generally
circular area or spot 72 rather than a single point. Source 52 can
be a standard helium-neon gas laser driven from a 12-volt battery
power source such as is commercially available from Nova Laser
Systems, Inc. Ltd., 1825 Wyandotte St., Windsor, Ontario, Canada as
Model Number Mark II and thus will not be described in further
detail.
As shown in FIGS. 2 and 3, sensor unit 58 has two vertically
stacked coplanar photovoltaic solar cells 74 and 76 mounted in a
frame 78 which is pivotally received in a yoke 80 for rotation on
an axis generally transverse to light beam 68. Photocells 74 and 76
are electrically isolated from both frame 78 and each other and
their adjacent ends are preferably spaced approximately 0.030 of an
inch from each other. Yoke 80 is pivotally mounted on slide 82 by a
bearing 84 for rotation on an axis generally parallel to light beam
68 and transverse to and intersecting the pivotal axis of sensor
mounting frame 78. Slide 82 is mounted for reciprocation in a
rectangular frame 86 fixed to an end wall of housing 60 and is
reciprocated by a threaded shaft 88 extending through housing 60
with a manually operable crank handle 90 fixed to its exposed end
(FIG. 2). A counter weight 91 fixed to the lower end of frame 78
provides a center of gravity for sensor unit 58 which is below its
transverse pivotal or gimbal axes to assure that sensor unit 58
within predetermined limits remains in a generally vertically
extending attitude as detector 50 pitches up and down and as it
rolls about its longitudinal axis.
As shown in FIGS. 3-6, source 52 is mounted on plate 54 by a gimbal
92 with a first generally rectangular, four-sided carrier frame 94
and a second U-shaped carrier frame 96. Carrier frame 94 is mounted
for rotation on a longitudinal axis generally parallel and
generally coincident with light beam 68 by a pair of tubular front
and rear coaxial hollow stub shafts 97 and 97' fixed to the front
and rear walls respectively of frame 94. Shafts 97 and 97' are
respectively journalled in bearings 98 and 98' respectively
received in vertically extending supports 100 and 100' slidably
connected for adjustment to track bars 102 and 102' fixed to
support plate 54. A hole 104 in the front wall of frame 94
concentric with shafts 97 allows light beam 68 to pass through
frame 94 via shaft 97 to impinge on sensor 58. Frame 96 of gimbal
92 is mounted in frame 94 for rotation on an axis perpendicular to
the axis of rotation of frame 94 by a pair of opposed coaxial
trunnions 106 each having a stub shaft 108 extending through the
associated side wall of frame 94. Shafts 108 are received in
coaxial bearing assemblies 110 mounted in opposed openings 112 in
forks 113 of frame 96. Laser unit 52 is fixedly mounted to frame 96
for rotation therewith between spaced parallel mounting plates 115
fixed to forks 113 of frame 96. Laser light unit 52 is preferably
mounted with the point from which light beam 68 eminates coincident
with the point of intersection of the rotational axes of gimbal
92.
To retain laser light unit 52 in a stabilized attitude within
predetermined limits, as detector apparatus 50 pitches and rolls, a
pendulum 114 is fixed to the lower end of a rigid arm 116 which
extends through a clearance hole 117 in carrier plate 54 and is
fixed at its upper end to frame 96. Movement of pendulum 114 and
thus movement of laser light unit 52 is dampened by a liquid 118,
such as castor oil, received in a generally rectangular container
120 releasably secured and sealed to the lower face of carrier
plate 54. The liquid 118 is prevented from escaping through
clearance opening 117 by a flexible seal 122 received over arm 116
and secured and sealed to the lower face of carrier plate 54.
The rearward end of detector 50 is pivotally mounted on trencher
unit 24 of ditching machine 20 by a pair of opposed coaxial stub
shafts 124 which are fixed to the side walls of cover housing 66
preferably coaxial with trunnions 106. As shown in FIG. 1, shafts
124 are pivotally received in the upper ends of a pair of
horizontally spaced arms 126 of a support bracket 127 fixed to the
rear of frame 26. The forward end of detector 50 is supported by a
threaded shaft 128 which is connected to tube 50 adjacent its
forward end and secured by jam nuts 130 to a bracket 132 fixed to
frame 26. Detector apparatus 50 is thus adjustably mounted on
trencher unit 24 with its longitudinal axis extending generally
parallel to the longitudinal dimension of trench 34 produced by the
trenching unit. The entire detector, including sensor 60, can be
pivoted about the axis of shafts 124 by adjusting nuts 130 on shaft
128 to thereby facilitate initial set up wherein tube 50 is
oriented with the longitudinal axis preferably generally parallel
to the desired grade of the bottom surface 38 of the trench.
Preferably, detector 50 is also mounted so that lateral gimbal axis
of light beam 68 is generally vertically above point 41 about which
trencher unit 24 pivots as indicated by vertical center line 134 in
FIG. 1.
The foregoing mounting of detector 50 is intended to accommodate
use of ditching machine 20 on terrain 36 which is inclined at not
more than about say a 2 or 3% grade. If more steeply inclined
terrain is encountered, arm 116 of pendulum 114 will strike the
edge of hole 117 in carrier plate 54 and prevent laser 52 from
assuming a stabilized attitude. Accordingly, to allow laser 52 to
assume a stabilized attitude when digging machine 20 is used on
more steeply inclined terrain, the angular relationship between
pendulum 114 and laser unit 52 is made adjustable by a modified
mounting structure shown in FIGS. 7 and 8. In this modified form,
laser 52 is fixed as by welds 136 to a steel plate 138 pivotally
mounted on frame 96 of gimbal 92 at a point coincident with the
axis of rotation of frame 96. Mounting plate 138 is releasably
secured in various angular positions in relation to pendulum 114 by
a threaded bolt 140 engaging a guide plate 142 fixed to carrier
frame 96. Bolt 140 extends through an arcuate slot 144 in plate 142
and a graduated scale 146 adjacent the slot indicates the angular
position of laser 52 relative to pendulum 114.
Detector 50 has electric control circuitry 150 schematically
illustrated in FIG. 9 which is mounted in control panel 62. In
response to the position of light beam 68 on photocells 74 and 76,
electric circuitry 150 operates and controls a conventional
electro-hydraulic, four-way directional control valve 152 connected
to a source of pressure fluid for controlling supply of such fluid
to a hydraulically actuated cylinder 154 of hoist mechanism 42 for
raising and lowering trenching unit 24. Electric relays 1-CR and
2-CR mounted in panel 62 control the supply of current from a
source 156 to a force motor 158 of hydraulic valve 152 which
actuates a pilot spool which in turn controls the main spool of the
valve. Current source 156 may comprise two 12-volt batteries 160
and 162 with one terminal of each battery, 164 and 166
respectively, of opposite polarity connected to ground. The other
opposite polarity terminals of batteries 160 and 162 are connected
across one end of a pair of leads 168 and 170. Normally open
contacts 1-C1 and 2-C1 of control relays 1-CR and 2-CR respectively
are connected in series with leads 168 and 170 respectively, and
the other ends of leads 168 and 170 are connected to one terminal
159 of force motor 158, the other terminal of which is connected to
the ground. The output terminals 188 and 188' of operational
amplifiers 182 and 184 are respectively connected through normally
closed contacts 2-C2 and 1-C2 to one side of the coils of relays
1-CR and 2-CR, the other terminal of the coils being grounded.
Potentiometers 198 and 198' are connected in parallel across leads
168 and 170 to provide individual adjustment of the point at which
each operational amplifier 182 and 184 saturates. A slide 200 and
200' of each potentiometer 198 and 198' is connected to input
terminal 180 and 180' of its associated operational amplifier 182
and 184 through a lead 202 and 202' and a resistor 204 and 204'
which limits the input current from the potentiometer to its
associated operational amplifier. Operational amplifiers 182 and
184 are protected from an overload at output terminals 188 and 188'
by limiting resistors 206 and 206' connected across output
terminals 188 and 188' and input terminals 180 and 180' through
leads 202 and 202'. Electric power for operational amplifiers 182
and 184 is provided by leads not shown in FIG. 9 through a master
power switch 207 mounted on control panel 64 (FIG. 2). A center
zero galvanometer 208 for nulling the output of the photocells 74
and 76 during adjustment of apparatus 50 as explained hereinafter
is connected in series with a switch 209 and terminals 178 of
photocells 74 and 76. Null meter 207 and switch 208 are mounted on
control panel 64. Potentiometers 198 and 198' are mounted on
control panel 64 and can be manually adjusted by turning knobs 210
and 210' respectively connected thereto.
Photocells 74 and 76 are of the photovoltaic type which generate an
output current proportional to the amount of light striking the
cell. Such cells are commercially available as catalog No. IN 240
CG from Centralab, Inc., Semi-Conductor Division of Globe-Union,
Inc. of El Monte, Calif. Suitable operational amplifiers 182 and
184 are commercially available as model No. LM-201 from National
Semi-Conductor Corp., San Ysidro Way, Santa Clara, Calif. 95051. A
model LM-201 operational amplifier has two input channels, one of
which is grounded as shown in the schematic of FIG. 9. With these
particular commercially available photovoltaic cells and
operational amplifiers suitable values for resistors 186-186',
198-198', 204-204', and 206-206' respectively are 10K, 50K, 100K
and 1 Meg. ohms, respectively.
As illustrated schematically in FIG. 9, ditching machine 20 has a
hydraulic system with a reservoir 211 connected to the outlet of
hydraulic valve 152 and the inlet of a pump 212 the discharge or
high pressure side of which is connected to the inlet port of valve
152. The control ports 214 and 216 (conventionally designated ports
A and B) of hydraulic valve 152 are connected by suitable conduits
218 to the opposed ends of hydraulic cylinder 154. A suitable
hydraulic control valve 152 is commercially available as Model
PVE-1000 from SLI Industries, 14740 Arminta St., Van Nuys, Calif.
91402. This model is a proportional pilot-operated four-way
directional control valve actuated by a force motor which can be
energized by a 12-volt DC power source. Electric circuitry 150 does
not utilize the proportional control feature of this valve which
has been selected because of its rapid response to the switching of
its force motor by the control relays rather than for its
proportional control feature per se.
To use detector apparatus 50, it is mounted on ditching machine 20
(as shown in FIG. 1) with one end adapted to move generally
vertically with digging wheel 28 and the other end adapted to pivot
about a point which is in a fixed relationship with a reference
point (such as point 41) on the bottom surface 38 of trench 34 with
the reference point moving with the digging machine as wheel 28
produces the bottom surface of the trench. Preferably, detector
apparatus 50 is mounted so that it pivots about the common point of
intersection of the transverse axes of rotation of gimbal 92 which
is preferably coincident with the point of emination of light beam
68. This pivot point preferably is on a generally vertical line
(such as line 134) extending through the reference point which
preferably is point 41 about which trenching unit 24 pivots or
rocks to control the grade or elevation of bottom surface 38 of the
trench.
In setting up and adjusting detector apparatus 50 to control the
grade of the bottom surface 38 of trench 34, digging machine 20 is
initially operated in a conventional manner by manually
manipulating the conventional control levers (not shown) to raise
and/or lower digging wheel 28 through cable and hydraulic mechanism
42 to bring the shoe 30 and point 41 to the desired grade of bottom
surface 38 in an initial portion of the trench. Laser unit 52 and
control circuitry 150 are energized by turning on switch 207. With
trenching unit 24 in the initial portion of trench 34, produced by
manually controlling the machine and with shoe 40 resting on this
initial portion of surface 38 at the desired grade, sensor unit 58
is shifted generally vertically so that laser beam 68 is centered
between and impinges equally on both photocells 74 and 76. Sensor
unit 58 is adjusted to center beam 68 by manually adjusting
threaded screw 128 to pivotally move detector apparatus 50 so that
beam 68 is approximately centered and the beam is precisely
centered by adjusting threaded screw 88 to raise or lower sensor
unit 58 relative to tube 52 of the detector apparatus. Null meter
208 is connected across photocells 74 and 76 by turning on or
closing switch 209 to provide an indicator for determining when
beam 68 is centered between the photocells so that they have equal
outputs. After beam 68 is centered, switch 209 is turned off to
deactivate null meter 208. In some situations such as where the
pitch or slope of the terrain is very steep, the modified form of
detector apparatus of FIGS. 7 and 8 is used so that laser unit 52
will be free to swing in gimbal 92. In this modified form the
angular relationship of pendulum 114 to the laser unit is also
adjusted in rough centering beam 68 between photocells 74 and
76.
After beam 68 has been centered, tractor 22 is driven by the
operator over terrain 36 along the desired longitudinal path of
trench 34 and detector 50 automatically controls the raising and
lowering of digging wheel 28 to produce the desired grade of bottom
surface 38. If, for example, tractor 22 goes over a high spot in
terrain 36, digging wheel 28 will be raised above the desired
elevation of surface 38 and, hence, detector apparatus 50 will
energize cable and hydraulic mechanism 42 to lower digging wheel 28
and when the tractor goes over a low spot in the terrain 36, wheel
28 will be urged below the desired elevation of surface 38 and
detector apparatus 50 will energize mechanism 42 to raise digging
wheel 28 to the desired elevation. Whenever light beam 68 is
deflected from its center position between photocells 74 and 76,
circuitry 150 in conjunction with hydraulic directional valve 152
and hydraulic cylinder 154 of mechanism 42 operates as a
servomechanism to raise or lower digging wheel 28 so that light
beam 68 is again centered between the photocells. For example, when
a high spot in terrain 36 shifts tractor 22 so that digging wheel
28 is raised above the desired elevation, detector 50 is pivoted
upwardly with the frame 26 about the pivot point 41 while laser
light source 52 remains in a stabilized attitude due to gimbal 94
and pendulum 114 so that more light of beam 68 impinges on
photocell 76 which increases the magnitude of its positive output
current. When the magnitude of this positive output current exceeds
the negative bias current at input terminal 180' set by
potentiometer 198', operational amplifier 184 saturates and
produces an output current at terminal 188 which energizes the coil
of control relay 2-CR. Energizing control relay 2-CR closes
normally open contacts 2-C1 which causes current from source 156 to
flow in one direction through force motor 158 and shifts the pilot
spool of hydraulic valve 152 in one direction from its neutral
position, thereby admitting hydraulic fluid under pressure through
outlet port 214 into the rod end of hydraulic cylinder 154 to
retract its rod and thereby extend the cable of mechanism 42 to
lower digging wheel 28 to the desired elevation and return light
beam 68 to its center position between the photocells. Similarly,
when a low spot in terrain 36 shifts tractor 22 so that digging
wheel 28 is lowered below the desired elevation, detector 50 is
pivoted downwardly with frame 26 about point 41 while laser light
source 52 remains in a stabilized attitude so that more light of
beam 68 impinges on photocell 74 which increases the magnitude of
its positive output current. When the magnitude of this positive
output current exceeds the negative bias current at input terminal
180, set by potentiometer 198, operational amplifier 184 saturates
and produces an output current at terminal 188 which energizes the
coil of control relay 1-CR. Energizing control relay 1-CR closes
normally open contact 1-C1 and thus causes current to flow in the
opposite direction through force motor 158, thus shifts the pilot
spool of hydraulic valve 152 in the opposite direction from its
neutral position, thereby directing hydraulic fluid under pressure
through port 216 into the head end of cylinder 154 to extend its
rod and thereby shorten the cable of mechanism 42 to raise digging
wheel 128 to the desired elevation and return light beam 68 to its
center position between the photocells. By adjusting potentiometers
198 and 198', the magnitude of the bias on inputs 180 and 180' of
operational amplifiers 182 and 184 can be varied and, hence, the
extent to which beam 68 can deviate or be displaced from the center
position between photocells 74 and 76 before the servo action is
initiated to return the beam to the center position can be adjusted
and controlled. Thus, the extent of the deviation of digging wheel
28 from the desired elevation of bottom surface 38 of trench 34,
can be adjusted and controlled. Each relay 1-CR and 2-CR has a
normally closed contact 2-C2 and 1-C2 respectively in the circuit
for energizing the coil of the other relay so that both relays
cannot become simultaneously energized which would provide a short
across power source 156 through force motor 158 of hydraulic valve
152.
Both laser light unit 52 and photocell sensor unit 58 are gimbaled
and weighted with pendulums to provide a center of gravity below
the intersection of the transverse axes of the gimbals so that the
units will remain in stabilized attitudes as the ditching machine
pitches and rolls. Thus, only the generally vertical displacement
of digging wheel 28 relative to reference point 41 as it moves
along the bottom surface produced by digging wheel 28 is indicated
by the deflection of beam 68 from its center position between
photocells 74 and 76. In one working embodiment, a detector device
comprising the aforementioned laser light unit Model No. Mark II of
Nova Laser Systems, Inc., and photovoltaic sensor cells Model IN
240 CG of Centralab Inc., with a longitudinal spacing of ten feet
between the photocells and the point from which the light beam
eminates from the laser light source, was mounted as shown in FIG.
1 on a tandem wheel traction farm trencher manufactured by Zimmer
Brothers Farm Drainage Ltd. of Chatham, Ontario. This trencher is
similar to but more rugged than like trenchers made by Speicher
Brothers, Inc., 308 Portland St., Celina, Ohio, and is adapted to
dig up to 6 foot deep trenches. On such a unit, detector 50
operates satisfactorily and has produced a trench 34 with a bottom
surface 38 which was within plus or minus one-eighth of an inch of
the desired grade or elevation in a lineal length of the trench of
100 feet. In operation, the mechanical vibration of the trencher
causes the gimbals or rotary mountings of the laser light and
photocell sensor units to oscillate about their stabilized
positions rather than come to rest in these positions, which is
believed to improve the accuracy and response time of the detector
apparatus. Similarly, the hydraulic and mechanical system for
raising and lowering the digging wheel to control the elevation of
the bottom surface of the trench tends to slightly overshoot and
hunt for the desired elevation so that it oscillates about the
position producing the desired elevation rather than coming to rest
at such position, which further improves the accuracy and response
time of the trencher. Where the terrain is reasonably flat or the
trencher is stabilized so that it does not roll or tilt sideways
significantly as it moves across the terrain, mounting the sensor
unit 58 in an adjustable fixed position so that it is not free to
pivot, and monnting the laser light unit so that it is free to
rotate on only one axis generally horizontal and transverse to the
travel of the trencher and hence is stabilized with respect to only
the pitching of the trencher, has worked satisfactorily.
From the foregoing description, it will now be apparent that the
present invention provides an improved apparatus for guiding or
controlling a vertically adjustable working implement as the same
operates to maintain a desired grade of the material being worked
by the implement along the path of travel of the machine carrying
or propelling the implement. By mounting the entire detector
apparatus 50 on machine 20 which carries or propels the working
implement 28, there is no need to provide or establish remote
sighting stations or associated equipment, thereby eliminating a
substantial cost item not only in equipment but also in set-up
labor. Moreover, the self-contained nature of the detector and
guidance system of the present invention enables the machine to be
used under extremely adverse field conditions due to the laser beam
being completely protected by tube 56 from the surrounding
environment. Also due to the fact that the beam 68 need not
traverse open air between a remote station and machine 20, it is
not affected by dust, haze or contaminated atmosphere and cannot be
obstructed by intervening obstacles along the path of working such
as trees, brush, changes in terrain or the like. The detector
apparatus 50 and associated control equipment as disclosed
previously herein has also proven to be extremely rugged since it
has been found capable of withstanding the extreme shocks and
vibrations normally encountered on a trenching machine of the
character described.
In prior existing laser beam vehicle guidance systems using a
source of laser light mounted stationarily and remote from the
entire machine and a sensor mounted on the machine, side tilt of
the machine will change the elevation of the sensor because it
travels through an arc during tilting motion of the machine. This
in turn will produce a false reading of a change in elevation where
in fact the working implement such as the digging wheel or the
tractor towing the digging wheel has not changed its elevation.
However, with the present invention both the stabilized source 52
of the laser beam as well as the remote sensor 58 are preferably
attached to an essentially rigid framework 26 or to other similar
portions of an equivalent machine. Therefore, the beam source and
sensor change elevation together during side tilt or sway of the
machine as it moves along the grade being worked, and hence this
motion does not introduce error into the guidance system.
It is to be understood that in the case of a trencher, road grader
or other similar construction equipment having a fore and aft
relationship between the vehicle and working implement, tube 56 is
oriented so as to extend in the direction of travel of the machine
along the path of material being worked. As used in this
description and appended claims, this means that tube 56 and hence
beam 68 will extend generally parallel to the direction of travel,
it being understood that detector 50 can be oriented with sensor 60
mounted either ahead of or behind source 52 relative to the forward
movement of the machine. However, it is also contemplated that the
detector 50 of the present invention may be used to control the
elevation of a working implement mounted to extend laterally of a
construction machine in applications where the relative motion
between the working implement and the machine which is carrying the
same occurs on a plane which is perpendicular or otherwise
laterally or transverse to the direction of forward travel of the
machine. When controlling an implement of this character, detector
50 is mounted such that tube 56 extends generally parallel to the
plane of such relative motion. One end of the framework of detector
50, such as sensor 60, is rigidly supported on the adjustable
working implement for movement therewith and the other end, such as
housing 66, is supported, as by a pivotal mounting previously
described herein, on a suitable reference platform of the machine
so that it is maintained in a predetermined relationship with a
portion of the machine which senses or rides on the material which
has already been worked to the desired grade.
It is also to be understood that it is preferred to mount detector
50 as closely as possible to the portion of the machine, such as
shoe 30, which is sensing the grade of the material already worked.
For example, in the case of the automatically guided trencher 20
described previously herein detector 50 is mounted with source 52
on the vertical center line 154 which extends through the pivot
point 41 of the shoe 30. Because the digging wheel frame 26 may be
lowered relative to the tractor 22 an amount sufficient to dig a
trench of up to say 6 feet in depth, detector 50 is mounted high
enough on frame 26 to remain above and clear of even the deepest
trenches being dug. However, in applications such as road grading
or the like where the working implement is operating essentially at
or slightly above the surface level of the surrounding terrain, it
is preferred to mount detector 50 within a foot or less of the
portion of the machine which is riding on or otherwise sensing the
grade of the material which has already been worked to the desired
grade by the machine.
It will be noted that sensor 58 is preferably mounted on machine 20
at a point remote from the machine-mounted source 52, say 10 to 30
feet. Such spacing provides an amplification of the travel of the
beam spot 72 impinging on photocells 74,76: i.e., only a slight
relative movement between the stabilized source 52 and its
supporting framework as frame 26 pitches up and down will cause a
relatively large amount of relative travel between the beam spot
and the photocells. Hence, sensor 58 is capable of detecting very
slight changes in elevation of the forward end of the frame 26
while still employing a relatively simple and rugged stabilizing
apparatus in the form of the pendulum weight 114. This
characteristic also makes it possible to construct detector 50 as a
very rugged and strong piece of equipment which is capable of
withstanding the very severe shocks and vibrations produced by a
trenching machine or the like during normal operation thereof.
* * * * *