Note: Descriptions are shown in the official language in which they were submitted.
~ 1141853
B~C~GROU~D OF T~E I~V~TI~
The present invention relates to a land seismicenergy source for seismic surveying or exploration on the
earth and particularly to a pivoted elevator mounting for
the generating assembly of such a land seismic energy source
In seismic exploration on land, intense seismic
impulses are transmitted down into the earth's surface at
a desired site or grouping of sites, called the "shot point"
or "shot points", and these impulses may be repeated at
frequent intervals. A network of geophones is used to
sense and to provide a recording of the results at various
points spaced from the shot point or points at which the
powerful sound impulses have been transmitted into the
earth. These geophones are coupled to the earth for re-
ceiving the seismic energy which has been reflected and/or
refracted by sub-surface geologic strata and various other
sub-surface structures in the earth. Then the seismic
energy generator equipment is raised from the surface of
the earth and moved to the next shot point or group of
shot points, and seismic impulses are then transmitted into
the earth at the new shot point(s3, and so on. In this
manner, information is obtained about the conditions and
characteristics o~ the geologic formations in the regions
being surveyed. Such seismic surveying can be conducted on
land, gravel, rocks, marshland, mud, sand, swamps or in
shallow water where the land source can be positioned down
against the earth.
Such land seismic energy sources have been con-
structed in compact and mobile form wherein the seismic
energy generator includes a tank which may be in the shape
of an inverted dome provided with a displaceable diaphragm
~ ~
1141853 .
.
bottom to enclose therein an incompressible liquid, such
as water. One or more powerful gas-releasing airguns are
positioned within the tank and receive and store pressurized
air or other suitable gas under high pressure from a source
of pressurized gas such as the high pressure receiver
storage tank of a high pressure air-compressor. A metal
pan is positioned between the diaphragm and the earth so
that upon a very sudden or intensely abrupt release of the
high-pressure gas into the liquid the flexible diaphragm
suddenly thrusts down on the metal pan to displace a portion
of the earth beneath the pan and thereby produce a powerful
seismic impulse transmitted down into the earth.
In reaction to this transmission of a powerful
seismic impulse, the seismic energy generator is forced
away from the ground and, thus, seismic energy generating
assemblies are generally constructed so that the energy
generator is free to move wi~in an assembly frame in
reaction to transmission of the seismic impulse. Hydraulic
catch cylinders are often provided to hold the energy
generator away from the ground surface for a short period
of time after the impulse is generated in order to avoid
spurious seismic signals which would result if the energy
generator were allowed to immediately fall back to its
initial position.
Various lifting arrangments have ~een used to
raise the seismic energy generator up from an operating
position on the ground to an inoperative position for
transport. Generally, in the prior art the seismic energy
generator assem~ly is pivotally suspended from a supporting
frame, and this supporting frame is swung upwardly along
an arc to raise the seismic energy generator assembly.
Detailed information concerning prior mobile
land seismic energy sources patented by the present inventor
~1418S3
is disclosed in U.S. Patents 3,800,907 issued April 2, 1974;
3,779,335 issued December 18, 1973; and 3,310,128 issued March
21, 1967. A preferred generator assembly which may be used with
the mounting apparatus of this invention is disclosed in United
States Patent No. 4,108,271 issued August 22, 1978 in the name
of the present inventor.
SUMMARY
It is among the advantages of this invention
that it provides an elevator mounting for a seismic energy gen-
erating assembly which readily accommodates local variations in
the slope of the earth's surface and enables powerful seismic
energy impulses to be transmitted into the earth in spite of the
fact that the generating assembly may be tipped away from verti-
cal orientation.
It is among the further advantages of this inven-
tion in certain of its aspects that it provides an elevator
mounting whereby the generating assembly may be easily placed on
ground not level relative to the vehicle on which the generating
assembly is mounted. Due to the ease with which the energy gen-
erating assembly can be set on unlevel ground and then used and
then can be elevated for transport to the next shot point, an
effective and efficient seismic surveying operation can be carried
out by the survey crew.
According to certain aspects of the present inven-
tion, a mobile land seismic energy source for surveying on the
earth by transmitting powerful seismic energy impulses into the
earth includes vertical guide means for guiding a seismic energy
generating asse~bly in vertical movement relative to an outer
-4-
853
supporting frame attached to a land vehicle. The vertical
guide means are pivotally mounted to the outer supporting
frame for swinging movement
-4a-
1853
about a generally horizontal axis. Elevator means are
provided to lift the seismic energy generating assembly
relative to the vertical guide means to lift the generating !
assembly from an operable position on the ground to an
inoperable position above the ground in readiness for trans-
port to a new shot point.
According to an ~ther aspect of the invention,
the vertical guide means include two rigid linear tubular
channel members and said generating assembly includes
horizontal extensions which fit into the tubular channel
members in sliding engagement therewith. The extensions
include tough, slippery plastic polymer sleeves at least
partially surrounding vertical -ylindrical mandrels posi-
tioned with}n and coaxial with the tubular channel members.
According to yet other aspects of the invention,
the vertical guide means is pivotally mounted to an outer
supporting frame by means of a spherical, self-aligning
bearing, and means are provided for limiting the angular
extent of the swinging movement of the vertical guide means.
According to a further aspect of the inventicn,
the means for limiting the swing of the vertical guide
means include first elements mounted on the vertical guide
means and second elements mounted on the outer supporting
frame cooperating with said first elements. These e~ements
include low friction slide pads which prevent the vertical
guide means from individually twisting about the spherical
bearings. In one embodiment as shown, there is a hori-
zontal extension from one of said vertical guide means and
outer supporting frame and a member on the other of said
vertical guide means and outer supporting frame. The
-5- !
member has an arcuate slot therein for receiving the
extension. The extension moves along the slot with swing-
ing movement of the vertical guide means but is stopped
by the slot at the ends thereof to limit the extent of swing
In another embodiment as shown, a face plat~ provides a
sliding track against which slide pads can travel in an
arcuate path with stop means for limiting the arc of swing-
ing motion.
According to another aspect of the invention,
the-generator assembly is pivotally connected to the outer
supporting frame for swinging movement about a horizontal
axis which passes generally through the center of gravity
of the generating assembly. To this end, the outer
supporting frame includes beams extending generally horizon-
tally from the chassis frame of the vehicle.
Advantageously, the illustrative embodiment
of this invention includes a support frame which supports
the seismic energy generator assembly for swinging movement
about a pivot axis extending transversely with respect to
the transport vehicle. The lateral wheel or tread spacing
of the vehicle is generally commensurate in size with the
diameter of the Ufootprint'' of the seismic impulse generator
Accordingly, the vehicle driver positions the vehicle with
respect to the shot point, so that the lateral wheelbase
location will achieve the requisite lateral tilting of the
generator assembly to accommodate a ground slope in one
geographic coordinate direction. Then, the transverse
pivot axis accommodates localized ground slope in a second
geographic coordinate direction perpendicular to the first.
~he support frame carries swing-limiting means for limiting
the extent of swinging movement of the generator assembly
about the transverse pivot axis.
I
1141853
Among the further advantages of the pivot
elevator mounting embodying this invention is that it enables
the seismic energy generator assembly to be reliably oper-
ated for transmitting the desired strong seismic energy
impulses into the earth even when the generator assembly
is simultaneously tilted in two directions, i.e. upon terrain
having a dual slope. ~t enables the generator assembly to
be pressed down firmly flush against the earth surface in
spite of the fact that the earth surface may ~e sloped in
two geographic coordinate directions at the shot point. Con-
sequently, an exploration crew is enabled to carry out a
seismic survey along a predetermined map line with intended
shot points at uniformly spaced increments along that line
in spite of irregularities in slopings of the earth sur-
face which are encountered as the crew proceeds with its
task. An accurate and reliable survey operation thereby is
produced, because the actual shot points, as made by the
crew are located in accordance with a predetermined program
where these shot points were intended to be located.
In other words, the survey crew becomes encouraged
to proceed in accordance with the predetermined survey
program rather than making spur of the moment deviations to
avoid difficult local terrain slopes.
The fact that the pivoted elevator mounting .
embodying this invention ena~les the seismic energy generator
to be conveniently and reliably operated in difficult terrain
is even more advantageous and important than might at first
appear. There are two new techniques in land seismic survey _
ing which are to be considered: (1) The most recent land
seismic survey programs are likely to specify that a relative _
ly grea umber of individual "pops", i.e. seismic energy
1141853
impulses, are to be transmitted by each seismic energy
generator per mile of travel. For example, the survey
program may specify the order of 500 "pops" per seismic
energy generator per mile. If a survey crew is using three
survey vehicles in a predetermined array, such a schedule
means that the crew will be called upon to produce 1,500
"pops" per mile of survey. Moreover, each "pop" is to be
transmitted from a precisely predetermined geographic co-
ordinate location in order that the resultant data collected
will appropriately and meaningfully match with the subsequen :
computer processing intended to be carried out. (2) In
addition, digital processing of the data being collected
may be carried out in the field as the survey itself is
progressing. Suitable port~ble microprocessors are now
available for such field processing. This field processing
of data as a survey progresses enables the person in charge
to make strategic decisions based upon what is being
learned. These strategic decisions may involve parameters
such as the spacing between shot points and the array of
shot points, the number of"pops"to be produced at each shot
point, and the arrangement of geophones. Changes in these
paramaters may be decided upon in order to enhance the data
in view of péculiarities in sub-surface geologic structures.
Consequently, the accuracy in the geographic
location of each shot point is tremendously important in
optimizing the effectiveness of the seismic survey campaign.
Now, when it is considered that as may as 500 "pops" per
vehicle per mile are being produced, it will be understood
that the real convenience and reliability in operation
irrespective of difficult terrain afforded by employing the
present invention are of crucial importance in practicable
accomplishment of the surveying objectives.
114~1953
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, features, and
advantages of the invention will be apparent from the
following more particular description of preferred embod-
imentsof the invention, as illustrated in the accompanying
drawings in which like reference characters refer to the
same parts throughout the different views. The drawings
are not necessarily to scale, emphasis instead being placed
upon illustrating the principles of the invention.
- Figure 1 is a side elevational view of a mobile
land seismic energy source including the improved elevator
mounting embodying the present invention. In this view,
the seismic energy generating assembly is set against a
site on the ground which has an uphill inclination from
the vehicle;
Figure 2 is a view similar to that of Figure 1
but showing the seismic energy generating assembly set
against asite having a downhill inclination;
Figure 3 is an enlarged-side elevational view of
the energy generating assembly and support frame of Figure
l;
Figure 4 is a rear elevational view of the gen-
erating assembly and support frame of Figure 3 as seen
from the position 4-4 in Figure 3, and with the generating
assembly shown in a level position;
Figure 5 is a top plan view of the energy gen-
erating assembly and supporting frame of Figure 4;
Figure 6 is a rear elevational view, with a
portion thereof in section, of the pivot mounting of
Figures 3 and 4. Figure 6 is a section taken along the
ine 6-6 in Figure 3 and shown greatly enlarged~
1141853
Figure 7 is a rear elevational sectional view
of the swing limiting means of Figures 3 and 4, being a
section taken along the line 7-7 in Figure 3 and shown
greatly enlarged;
Figure g is a rear sectional, eIevational
view of a lift guide extension from the cage-like frame
positioned within the tubular guide channel. Figure 8
is a section taken along the line 8-8 in Figure ~ and shown
greatly enlarged;
- Figure 9 is a top sectional view of the lift
guide extension and tubular guide channel taken along line
9-9 in Figure ~;
Figure 10 is a rear elevational sectional view,
similar to Figure 7, and showing a modified embodiment
of the swing limiting means; and
Figure 11 is a side elevational sectional view
taken along the line 11-11 in Figure 10. - .
DETAILED DESCRIPq~ION
AS may be seen in Figur~sl and 2, a seismic
energy generating assembly for generating the transmitting
into the earth strong seismic energy impulses is indicated
generally at 22. The generating assem~ly 22 is shown
. .
. .
1141853
positioned upon the surface of the earth and is supported
by an outer supporting frame shown generally at 23. This
suppoxting frame 23 is attached to a conventional land
vehicle 24. Such a conventional land vehicle 24 may be
a truck, a log skidder, a tractor, a vehicle with revolving
treads, and so forth, depending upon the type of terrain
to be explored. The seismic energy generating assembly
22 includes an inner cage-like frame 26 with a seismic
energy generator 28 supported therein. The seismic energy
generator 28 includes a steel pan 30 which is positioned
on the earth surface when a seismic impulse is to be
generated and transmitted down into the earth.
As can be seen in Figure 1, the elevator mounting
of the present invention is swingable about pivot bearings
29 carried ~y the supporting frame 23 so that the orien-
tation of the generating assembly as a whole is adapted to
conform with local variations in the slope of the earth
surface. Thus, the metal pan 30 can be seated down flush,
even against a surface which is inclined relative to ~he
vehicle. As shown in Figure 2, the pivoted elevator
mounting is also adapted to conform to a local region of
the earth surface which slopes d~wnwardly relative to the
vehicle.
The seismic energy generating assembly 22 is more
clearly shown in the enlarged views of Figures 3 and 4.
The inner cage-like frame 26 includes a lower circular
portion 31 having resilient bumper eleme~ts 33 extending
downwardly therefrom which are shown pressing down against
the upper rim of the pan 30. With the generating assembly
22 in the operating position as shown the cage~ e frame
26 presses the pan 30 down against the earth.
1141853
It has been noted that when a strong seismic
impulse is transmitted into the earth, the generator 28 is
suddenly forced upwardly in a reaction as the pan 30 is forced
downwardly in a sudden powerful impulse. To reduce the upward
reaction movement of the generator and to increase the magnitude
of the seismic impulse, weights 32 are rigidly attached to the
generator. As described in U.S. Patent No. 3,779,335 and in
U.S. Patent No. 4,108,271 referred to above, a water/air separ-
ator 34 is provided to separate the air which has been dis-
charged by the airgun or airguns (not shown) from the water
in the confining tank of the generator (not shown) so that this
discharged air can then be released into the atmosphere.
When a seismic impulse is generated, the genera-
tor 28 suddenly moves upwardly along with its weights 32. Once
the energy generator 28 has reached the upper limit of its move-
ment in reaction to the seismic impulse, hydraulic catch cylin-
ders 36 and 38 having check valves associated therewith prevent
the generator from crashing down. Associated hydraulic circuits
are arranged to lower the generator down gently into its ori-
ginal position with the pan against the earth in readiness to
transmit another impulse into the earth. For information about
the appropriate hydraulic circuit arrangement, the reader may
see U.S. Patent No. 3,779,335 referred to above. ~he hydraulic
cylinders 36 and 38 have their upper ends attached by respec-
tive self-aligning connections 40 and 42 at the top of the
cage-like frame 26, and similar self-aligning connections are
provided for attaching the bottom ends of the piston rods 37
and 39 extending from cylinders 36 and 38.
-12-
~141853
In order to prevent tilting of the pan 30 into
a misaligned position prior to firing, a plurality of '.
pneumatic pull-up cylinders 44 and 45 may be provided as
described and claimed in said application, Serial No. 805,522 .
The upper end of each cylinder is secured to the cage-like
frame 26. Respective piston rods 46 and 48 are connected
to the pan 30 by pull-up connecting links 5~ and 52. A
flexible high pressure hose line (not shown~ feeds compress-
ed air into each pull-up cylinder beneath-the piston therein
for exerting a forceful upward pull on the perimeter of the
pan to hold the pan against the bumpers 33 prior to firing
of the airgun(s). Thus, if the operator inadvertently place~
the pan 30 of the land seismic energy source down on the 1.
ground with a rock or the like eccentrically located under
the bottom of the pan, the upward pull of the connecting linX s
50 and 52 prevents the pan from tilting relative to the rest
of the seismic energy generator prior to firing. After
firing of the airgun(s), downward motion of the pan 30 is
permitted by extension of the piston rods 46 and 48.
Durin~ transport from one shot point to the
next shot point, the generatar assembly 22 is elevated from
the surface of the earth as will be explained later. The
generator 28 is then supported by the piston rods 37 and 39
which become fully extended from cylinders 36 and 38, and
the pan 30 is held up by a plurality of flexible, stretchabl~
curved holdup straps 54 and 56. These holdup straps are
sufficiently flexible and stretchable to permit downward
movement of the pan 30 during transmission of a seismic
impulse into the earth. ~lso, they are slac~ and assume a
1141853 1 1
bowed configuration, as seen in FIG. 4, when the pan 30 is
being pressed against the earth before the generator
28 is actuated (fired).
If desired, the pull-up cylinders 44 and 45
and connecting links 50 and 52 may be omitted, if the total
number of holdup straps 54 and 56 is increased, for example,
to six or eight in number.
The supporting frame 23 includes a main lower
yoke structure 58 (FIGS. 3, 4 and 5) and an upper yoke
structure 59. The pivot bearing assemblies 29, discussed
above, are mounted on the lower yoke structure, as will be
explained later, and they define a horizontal pivot axis
63 about which the seismic energy generating assembly 22
can swing. The upper yoke structure 59 includes means
for limiting the extent of swinging movement as will be
explained.
Instead of forming the supporting frame 23
to include lower and upper yoke structures 58 and 59,
these two yoke structures can be integraged into a single
yoke structure as explained below.
As seen in plan view in FIG. 5, the lower and
upper yoke structures 58 and 59 each has a generally U-
shaped configuration and partially encircles the seismic
energy generating assembly 22. The lower yoke structure
58 provides the main support for the seismic energy generat-
ing assembly 22 and includes a pair of beams 60 and 62 which
extend generally horizontally from the rear of the chassis
frame 61 (FI~S. 1 and 2) of the land vehicle 24. The
seismic energy generating assembly can be elevated along
vertical guide means which include long upright channel
members 64 and 66 (FIGS. 3, 4 and 5). These channel
Il I
1~1853
11
members (one of which is also seen in FIGS. 6, 7, 8 and 9)
are tubular members, each having a vertical, longitudinal
opening therein facing inward toward the seismic energy
generating assembly 22. These channel members are pivotal-
ly mounted to the outer supporting beams 60 and 62 by the
pivot bearing assemblies 29, so that the generating assembly
with its vertical guide means can swing about a horizontal
pivot axis 63 for accommodating various localized slopes
of the ea~th surface, as discussed above.
One of the two pivot bearing assemblies 29
for pivotally mounting the tubular channel members 64 and
68 onto the support beams 60 and 62.of the lower yoke struc-
ture 58 is best shown in FIG. 6. A pivot pin 72 has a large
flange 73 and is mounted to a plate 74 which is welded onto
a short length of channel 76. This channel 76 is fitted
onto the tubular channel member 64 like a saddle and is
welded thereto. This pivot pin 72 with its flange 73 is
secured to the plate 74 by a retainer 75 held by bolts 77.
This pivot pin 72 supports a commercially available spherical
self-aligning bearing element 78 within a concave bushing 80.
The bushing 80 is centered in a clearance opening 79 formed
in the web 86 of beam 60 and is held in place by an opposed
pair of clamping plates 82 and 84 which are bolted together
by a plurality of bolts 85 passing through the web 86.
The bushing 80 is a hardened steel and this bearing may be
lubricated through a grease ~itting 88. To prevent loss of
grease, plastic seals 89 are provided.
In addition to the main ~eams 60 and 62 o~ the
lower yoke structure 58, the supporting frame 23 includes
the upper yoke structure 59, discussed above, including
11~1~53
upper beams 90 and 92 as shown in FIGS. 3, 4 and 5. The
upper and lower yoke structures 58 and 59 are rigidly held
together by an upright frame plate 94 and by upright struts
95 on each side (only one can be seen in FIG. 3). The upper
yoke structure 59 is further secured to the vehicle by
rigid diagonal struts 96 and 98, which are tubular in form.
As mentioned above, the two yokes 58 and 59 -
of the supporting frame 23 can be integrated into a single
yoke structure. ~his integral yoke 58 and 59 is made by
replacing the upright side struts 95 with relatively large
area side plates (not shown) which are welded in place extend-
ing between the upper and lower beams 90 and 60 and 92 and
62, respectively. Moreover, by extending these two side
plates forwardly sufficiently far along the lower beams 60
and 62 and by shaping the front edge of each plate to slope
upwardly and back in the manner of a gusset,then these two
side plates may also serve to replace the diagonal struts 96
and 98.
In order to limit the possible swing of the
seismic energy generating assembly 22 about the horizontal
pivot axis 63, a pair of similar swing limiting means 100
and 101 (FTGS. 3, 4 and 73 are provided on the beams 90 and
92, respectively, of the upper yoke structure 59. As shown
in FIG. 3, an arcuate slot 102 is formed in the inner
vertical web 99 of the box beam 9~, and a pin 104, fixed
to the tubular channel member 64, travels in this arcuate
slot. This slot 102 is defined by a segment of a circle
centered at the pivot axis 63. The pin 104 travels along
the slot with swinging of the generating assembly 22 but
is stopped by the ends of the slot. In this example, the
1141853
ends of this arcuate slot are positioned at an angle of 10
forward and aft of a vertical line passing through the pivot
axis 63, thus determining a swing limit of 10 either way
of the generator assembly 22 relative to the support frame 23
but a greater or lesser swing limit may be provided, if
desired.
A sectional view of the swing limiting means
100 is shown in FIG. 7. The pin 104 is welded to a plate 103
which is secured by bolts 105 to a mounting plate 109 welded
onto a channel 111 which is welded to the tubular channel
member 64. The swing limiting pin 104 extends outwardly
through the slot 102. The web 99 serves as a vertical slide
plate extending fore and aft, and near the slot 102 it is
straddled by a pair of tough, slippery plastic slide pads 106
and 107,for example, of high molecular weight polyethylene.
A large steel washer 108 carried by the pin 104 is held
against the outer slide pad 106. These slide pads, being
of tough, slippery material, offer little resistance to swing
ing of the generator assembly even with a tight sliding fit.
To provide access to the pin 104 and arcuate slot 102, a
removable cover plate 110 is fastened over an opening in
the outer vertical web of the box beam 90.
In order to prevent the tubular guide 64 from
turning into a misaligned position about its own axis~ as
might otherwise occur due to the spherical bearing assembly
29 (FIG. 6), the slide pads 106 and 107 are pressed firmly
against the vertical web plate 99. To exert a continuing
firm pressure by both slide pads 106 and 107, a plurality o~
owerful springs 120 thrust against the large washer 108.
ll~i~53 l
~hese springs 120 are mounted in sockets 121 in a spring
retainer 123 held in place by a nut on the pin 104
In order to enable the seismic energy
generating assembly 22 to be elevated, it is mounted to the
tubular vertical guide means 64 and 66 by means of hori-
zontal extension arms 112, 114, 116 and 118 (FIG. 4) from
the cage-like frame 26. As seen in plan view in FIG. 5, the
upper pair of extension arms 114 and 116 project through the
longitudinal openings in the tubular guide channels 64 and
66, and the lower pair of extensions 112 and 114 are
similarly aranged. One of these extensions and the tubular
guide channel are shown in detail in FIGS. 8 and 9.
An arm 114 extends from the cage-like frame 26
and has a cylindrical metal mandrel 122 secured thereto
as by welding. The mandrel is positioned within and is co-
axial with the tubular lift guide channel member 64. A
plastic sleeve 124 of tough, slippery plastic, for example,
high molecular weight polyethylene or Nylon, is wrapped
around the mandrel 122 and is supported on a bottom shoulder
126 of the mandrel. The plastic sleeve is retained on the
mandrel by a washer 128 and a bolt 132 screwed into the
mandrel. Because the plastic sleeve is a tough, slippery
polymer and is a good bearing material, the above assembly,
when positioned within the guide channel 131 of the tubular
member 64, provides a good sliding fit and does not inter-
fere with elevation of the generator assembly 22 along
the guide channel 131. The longitudinal opening in the
guide member 44 is shown at 133 in FIG. 9.
The plastic sleeve 124 is exceptionally durable.
However, if replacement becomes necessary, the washer 128 can
e easily removed to permit convenient removal of the worn
`` 1~4~:853
sleeve. Although the plastic sleeve 124 has a larger dia-
meter than the width of the slot 133, this sleeve can be
removed through the slot 133. This removal is accomplished
by Eirst moving the sleeve 124 upwardly along the lift
guide channel 131 until the sleeve 124 is above the top
of the mandrel 122. Then the sleeve 124 can be rotated 90
and removed out through the slot 133. The width of the sleev
124 in the direction X is less than the width Y of the open-
ing 133, and so when the sleeve is turned 90, it can be
readily removed. A new sleeve can then ~e inserted into
the channel 131 through the slot 133 and turned 90 into
correct alignment. This new sleeve may then be slid down-
wardly in the guide channel 131 into position around the
mandrel 122. Thus, there is advantageously no requirement
for the replacement of expensive metal parts having close
tolerances.
In order to elevate and to lower the
generator assembly 22 along the guide means 64 and 66, a
pair of hydraulic lift and lowering cylinders 134 and 136
(FIGS. 3, 4 and 5) are provided. These cylinders are con-
nected by means of clevis pivots 138 and 140 to brackets 142
and 144 secured to the upper ends of the guide channel
members 64 and 66, respectively. The respective piston rods
146 and 148 extend downwardly and have clevises 150 and 152
fixed to the ends thereof. The piston rods are attached by
means of clevis pins 154 and 156 to brackets 158 and 160
on the lower circular portion 31 of the cage-like frame 26.
By retracting the piston rods 146, 148 into the cylinders 13
and 136, the cage-like frame 26 and thus the entire seismic
energy generator 28 is elevated along the lift guide channel
members 64 and 66. By reversing the action of the lift
~1 1141853 1l
.
.
cylinders 136, 138, the piston rods 146, 148 are extended
for lowering the frame 26 and generator 28. The bumpers
33 become pressed down onto the rim 157 of the pan 30 for
pressing it down forcefully against the ground.
In operation, the seismic energy generating
assembly 22 is transported to the surveying location in an
elevated position by the land vehicle 24. The piston rods
146 and 148 are completely retracted, thereby holding the
cage-like frame 26 in the elevated position as guided by
the extension arms 112, 114, 116 and 118. At the surveying
site or"shot point" the vehicle 24 is positioned so that
the pan 30 can be seated down firmly flat against the earth
surface with angular adjustment only about the horizontal
pivot axis 63. This firm seating of the pan 30 flat against
the surface of the earth in spite of local slope inclina-
tions is advantageously accomplished since the lateral wheel
spacing of the vehicle 24 is hardly wider than the generat-
ing assembly. Thus, the driver positions the parked veh'icle
24 so that its lateral tilting provides the necessary
late tilting of the seismic energy generating assembly
. ' 1.
,
.
llgl853
¦ It is to be noted that the horizontal pivot axis
63 extends transversely; in other words it extends parallel
with the direction of the axles of the vehicle, which is
the direction of the lateral wheel spacing. This lateral
wheel spacing may be called the "lateral wheelbase", and
¦ it is generally co~surate in size with the diameter of
the "footprint" of the seismic impulse generator ~area of
contact of the pan 30 on the ground~. The lateral wheel-
base is much smaller than the longitudinal wheelbase of the
vehicle as determined by the spacing between the forward-
most-and rearwardmost axle of the vehicle. Accordingly,
the driver positions the vehicle so that the lateral wheel-
base location will achieve the requisite lateral tilting
of the generator assembly 22 to accommodate ground slope
in one coordinate direction for the pan 30 to seat flush
onto the earth surface at the shot point. With the vehicle
thus positioned, the piston rods 146 and 148 are extended
to lower the seismic energy generating assembly 22, includ-
ing the cage-like frame 26 and the seismic energy generator
28, until the pan 30 is pressed down by the resilient bumpe
33 flush against the earth surface. Where the surface
at the shot point is inclined upwardly ~rom the longitudinal
wheelbase of the vehicle 24 as shown in Figure 1, the
vehicle may be moved slightly forward as the pan 30 is set
on the ground. As the pivot axis 63 moves forward the
assembly automatically pivots so that the pan 30 ~uickly
rests flush aginst the earth surface.
For a downward slope of the shot point sur~ace
relative to the longitudinal wheelbase of the vehicle as
in Figure 2, the vehicle 24 may be moved slightly in re-
verse as e pan 30 is set on the ground so that the assembl
1141853 1 1
pivots to the position shown.
In summary, the positioning of the lateral wheel-
base accommodates ground slope in one geographic coordinate
direction, and the transverse pivot axis 63 then accommo-
dates localized ground slope in the other geographic
coordinate direction perpendicular to the first.
In order to reduce the amount of forward and
reverse movement of the vehicle in setting the pan 30 flush
against the earth surface, it is preferred that there be
a low pivot axis for the generator assembly generally
passing through its center of gravity. For a given angular
adjustment, the required fore and aft movement of the
vehicle is reduced by lowering the pivot axis. The extent
of horizontal compensation required can be seen to be the
sine of the angle of adjustment, times the distance between
the pivot axis 63 and the bottom surface of pan 30. By
lowering the pivot axis, this distance and thus the re-
quired horizontal compensation is reduced.
Although for the above reasons it is preferred
that a low pivot axis 63 be provided, it is ~est that this
axis not be below the center of gravity of the seismic
energy generating assembly 22 when this whole assembly
is in its most elevated position. If the axis were below
the center of gravity, ~he assembly would tend ~o be top
heavy and awkwardto handle. Thus, the pivot axis 63 should
be at about or slightly above the center of gravity of the
e~e~ated assembly 22 but not below that center of gravity.
The seismic energy generator assembly can be
reliably operated for transmitting intense seismic energy
impulses into the earth even when it is simultaneously
tilted in two geographic directions, that is upon terrain
having dual slopes. The bottom diaphragm surface 162 of
1141853
the pan 30 of the seismic impulse generator is enabled to
be pressed down forcefully flush against the earth's sur-
face by the lift cylinders 134, 136 in spite of the fact that
the ground may be sloped in two geographic coordinate
directions at the shot point, thereby achieving good coupling
with the earth's surface, so as to be able reliably to
transmit strong seismic impulses down into the earth.
FIGS. 10 and 11 show an alternative swing-limit-
ing means lOOA, and a similar swing-limiting means may be
used on the opposite side of the seismic energy generating
assembly 22. The upper beam portion 90 of the supporting
frame 23 has a vertical slide plate 99A mounted thereon.
This slide plate 99 extends in a fore and aft direction.
In FIG. 11, this slide plate 99A is shown in dash and dotted
outline because it is out of the plane of the section 11-11.
Welded to the tubular lift guide member 64
is a short channel 111 having a mounting plate 109 welded
thereto. A pair of slide pads 107 of tough slippery
plastic, such as high molecular weight polyethylene are
mounted on the mounting plate 109. Each pad 107 has a flang~
164 extending around it, and a retainer member 166 overlaps
and engages the flanges 164 to hold these pads in place.
This retainer 166 has a pair of rectangular openings 168
~FIG. 113 through which the pair of slide pads 107 can
protrude into contact with the slide plate 9~A. A plurality
of bolts 105 at each end secure this retainer to the mount-
ing plate 109.
As indicated by the arrows 170 in FIG. 11,
the tubular lift guide member 64 together with its slide pad
swing-limiting assembly lOOA can swing back and forth.
11~1853
The pads 107 slide along an arcua~e path against the inside
face of the slide plate 99A. For limiting the extent
of this swinging movement, there are resilient bumpers 172
mounted on brackets 174 at each end of the slide plate 99A.
In this example, the limit of swing is approximately 10
fore and aft of vertical, but may be made more or less, as
desired, depending upon the overall length of the slide
plate 99A.
This pair of slide pads 107 are spaced
apart in the fore and aft direction, and they bear
firmly against the slide plate 99A in sliding relationship
therewith. They thereby prevent the tubular guide member
64 from turning into a misaligned position about its own
axis as might otherwise occur due to the spherical bearing
assembly 29 (FIG. 6).
In other words, the pair of spaced slide pads
107 in FIG. 11 engaging firmly against one side of the
slide plate 99A stabilize the tubular lift guide member 64
against twisting about its own axis. Similarly, in FIG. 7
the relatively wide pair of slide pads 107 and 106 firmly
engaging opposite faces of the slide plate 99 in sandwich
relationship stabilize the tubular lift guide member 64
against twisting about its own axis. It is to be under-
stood that the two slide pads 107 in FIG. 11 could be re-
placed by one large slide pad having sufficient size to
provide the desired stabilization.
In FIGS. 1 and 2, the support frame 23 is
shown cantilevered from the rear of a vehicle 24. In
other words, the seismic energy generating assembly 22 is
n an "out~oar~" position.
~141853 l
It is to be understood that land seismic
survey vehicles can be constructed having a large clearance
opening within the chassis between the front and rear wheels
for receiving a seismic energy generating assembly "inboard"
within such a clearance opening, for example, as shown in
my earlier Patent No. 3,310,128 to which reference has been
made. Accordingly, it is to be understood that the support
frame 23 can be arranged to support the seismic energy
generating assembly 22 inboard within a large clearance
opening in the chassis of a vehicle between the front and
rear wheels. In such a case, the main side beams 60 and 62
are mounted to the chassis frame near the large clearance
opening in the chassis where the seismic energy generating
assembly is located, and the pivot axis 63 (FIG. 4) extends
transversely with respect to the vehicle.
In the event that the chassis of the vehicle is
designed so that it includes two main beams spaced apart
an appropriate distance and located at an appropriate height
above the ground, then portions of such chassis beams may
directly support the bearing assemblies 29, as shown in
FIG. 6, by forming a hole 80 in the web of such chassis
beam. The swing-limiting means, such as in FIG. 7 or in
FIGS. 10 and 11, are secured to a supporting frame which is
similar to the frame 23 and which extends above the chassis
of the vehicle on either side of the inboard mounted seismic
energy generator assembly 22.
The operation of such an inboard mounted
seismic energy generating assembly 22 is the same as des-
cribed above and is convenient and reliable as described
above. Lateral sloping of the ground is accommodated
by lateral tilt of the w~ole vehicle together with the
assembly 22, while any fore and aft sloping of the ground
l ~'
4~
at the shot point is accommodated by swinging movement
aboùt the transverse pivot axis 63, the same as described
for the outboard mounted assembly 22.
As a result of the convenient and reliable
operating characteristics, an exploration crew is enabled
to carry out a seismic survey along a predetermined map
line with intended shot points at uniformly spaced incre-
ments along that line in spite of difficult irregularities
and dual slopes inthe earth's surface which are encountered
at the successive intended shot points as the crew moves
ahead with its project. An accurate and reliable survey
operation is thereby produced, i.e. reliable data is collect .
ed. The actual shot points as made by the crew will
correspond with those shot points which were laid out on
the map in accordance with a predetermined survey program.
The crew is encouraged to proceed in accordance with the
predetermined survey program rather than making spur of
the moment local deviations to avoid difficult terrain
slopes as encountered. Irrespective of difficult terrain,
the seismic surveying objectives are enabled to be accom-
plished effectively and efficiently.
While the invent~on has been particularly
shown and described with reference to a preferred embodi-
ment thereof, it will be understood by those skilled in
the art that various changes in form and details may be
made therein without departing from the spirit and scope
of the invention as defined by the appended claims.
