`
`
`Ex. PGS 1030
`
`
`
`EX. PGS 1030
`
`
`
`
`
`

`

`United States Patent [19J
`Myers
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,885,726
`Dec. 5, 1989
`
`[54] COMPOUND HYDRAULIC SEISMIC
`SOURCE VffiRATOR
`Inventor: Wilbur J. Myers, Ft. Worth, Tex.
`[75]
`[73] Assignee: Conoco Inc., Ponca City, Okla.
`[21] Appl. No.: 265,428
`[22] Filed:
`Oct. 31, 1988
`Int. Cl,4 ............................................. H04R 23/00
`[51]
`[52] u.s. Cl ..................................... 367/142; 367/143;
`367/174; 181/120
`[58] Field of Search ....................... 367/143, 174, 142;
`181!110, 120, 402; 91!530, 167 R; 92/65
`References Cited
`U.S. PATENT DOCUMENTS
`3,653,298 4/1972 Bilodeau ................................. 92/65
`
`[56]
`
`3,676,840 7/1972 Bays ...................................... 340/12
`4,139,733 2/1979 Falkenberg ......................... 381/202
`4,741,246 5/1988 Padarev ................................ 91/530
`
`Primary Examiner-Deborah L. Kyle
`Assistant Examiner-J. Woodrow Eldred
`
`[57]
`ABSTRACf
`A seismic source marine vibrator having compound
`hydraulic cylinders for high and low frequenCies is used
`to generate both low frequency and high frequency
`acoustic pulses. Low frequency pulses are generated by
`operating a low frequency radiating surface and a high
`frequency radiating surface simultaneously. High fre(cid:173)
`quency pulses are _generated by operating the high fre(cid:173)
`quency radiating surface alone.
`
`22 Claims, 2 Drawing Sheets
`
`/6
`
`Ex. PGS 1030
`
`

`

`U.S. Patent Dec. s, 1989
`
`Sheet 1 of2
`
`4,885,726
`
`16
`
`/6
`
`FIG. 2
`
`FIG.
`
`I
`
`Ex. PGS 1030
`
`

`

`U.S. Patent Dec. 5, 1989
`
`Sheet 2 of2
`
`4,885,726
`
`0
`
`FIG.
`
`Ex. PGS 1030
`
`

`

`1
`
`4,885,726
`
`2
`in conjunction with a single actuator. U.S. Pat. No.
`3,394,775, which is a continuation in part of U.S. Pat.
`No. 3,329,930, introduces a vibrational transducer unit
`which consists of two pistons attached to a cylinder and
`5 a piston rod. A flexible rubber cylinder or boot is
`slipped over these two pistons and securely fastened to
`each so that air which is trapped between the pistons
`cannot escape into the water nor can water flow into
`the air chamber. The reciprocating piston imparts a
`pressure wave into the water while the innerhousing
`areas within the rubber enclosure are isolated and main-
`tained at a predetermined air pressure such that maxi(cid:173)
`mum coupling of vibrational energy into the water
`medium is provided.
`U.S. Pat. No. 3,482,646 titled "Marine Vibrator De(cid:173)
`vices" issued to G. L. Brown et al. is a single piston,
`single actuator type of assembly similar to that of the U.
`S. Pat. No. 3,392,369. A pair of shell-like housing mem(cid:173)
`bers are disposed generally in parallel and are flexibly
`sealed between the respective outer peripheries to de(cid:173)
`fme an interior air space. A drive means is contained
`within the air space and connected to the respective
`housing members to impart reciprocal movement to one
`housing member with respect to the other.
`Additional hydraulic seismic source generating sys(cid:173)
`tems are described in U.S. Pat. No. 4,103,280, titled
`"Device for Emitting Acoustic Waves in a Liquid Me-
`dium" issued to Jacques Cholet et al., U.S. Pat. No.
`4,211,301 titled "Marine Seismic Transducer" issued to
`J. F. Mifsud, U.S. Pat. No. 4,294,328 titled "Device for
`Emitting Acoustic Waves in a Liquid Medium by Im(cid:173)
`plosion" issued to Jacques Cholet et al. and U.S. Pat.
`No. 4,578, 784 titled "Tunable Marine Seismic Source"
`issued to J. F. Mifsud.
`However, as stated previously, all of the foregoing
`hydraulic vibrator systems share a common problem.
`That is, none of the foregoing systems are capable of
`operating over a wide range of frequencies but in gen(cid:173)
`eral, are limited to acoustic pulse generation in the low
`frequency range.
`
`COMPOUND HYDRAULIC SEISMIC SOURCE
`VIBRATOR
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`This application is related to co-pending U.S. patent
`application Ser. No. 265,601 entitled "Multiple Fre(cid:173)
`quency Range Hydraulic Actuator" (ICR 8139) filed
`concurrently herewith.
`.
`
`10
`
`BACKGROUND OF THE INVENTION AND
`RELATED ART
`The present invention relates to marine seismic explo(cid:173)
`ration, and more particularly to marine seismic explora- 15
`tion in which a seismic source is coupled to the ocean
`floor to generate acoustic pulses.
`In present seismic exploration, acoustic pulses are
`generated by seismic sources, propagate through the
`earths crust, are reflected by subsurface interfaces and 20
`detected upon the ret~ to the surface. In marine ex(cid:173)
`ploration, seismic sources have taken the form of explo(cid:173)
`sive charges and airguns. However, both of these types
`of seismic sources have had deleterious effects on ma(cid:173)
`rine life. As a result, a hydraulic vibrator had been 25
`developed. The hydraulic vibrator used in marine ex(cid:173)
`ploration is similar to that used in land based seismic
`exploration. This type of seismic source has been found
`to have less deleterious effects on marine ecosystems.
`In seismic pulse generation, it is beneficial to be able 30
`to generate pulses over a wide frequency range. In this
`regard, the use of hydraulic vibrators includes a prob(cid:173)
`lem in the range of frequencies generated. In general, a
`hydraulic vibrator system includes a hydraulic power
`plant, a hydraulic cylinder, hydraulic circuitry and 35
`structural members designed to operate over a range of
`frequencies. Stroke and flow requirements for low fre(cid:173)
`quency operation necessarily are exclusive of high fre(cid:173)
`quency operation due to their size and mass. Similarly,
`stroke and flow design requirements concommitant 40
`with high frequency propagation exclude the applica(cid:173)
`bility of these vibrator systems from use in low fre(cid:173)
`quency systems.
`
`45
`
`PRIOR ART
`An example of an early type hydraulic vibrator sys(cid:173)
`tem is described in U.S. Pat. No. 3,392,369 titled "Fluid(cid:173)
`Actuated Dual Piston Underwater Sound Generator"
`issued to J. A. Dickie et al. In the patent, two similarly
`sized sound radiating pistons are driven by hydraulic 50
`actuators in unison. The pistons are arranged as a pair of
`oppositely outwardly facing elements on opposite sides
`of the stationary housing and are sealed to the housing
`by flexible rubber gaskets. The actuator is adapted to
`move each piston in the direction opposite to that of the 55
`other at any particular time. As the pistons move out
`changing the external volume of the transducer, the
`internal space is filled with a gas under pressure. The
`apparatus described in this patent is designed to operate
`at low frequencies so that the sound waves which are 60
`generated under water have low attenuation.
`U.S. Pat. Nos. 3,329,930 and 3,394,775, both entitled
`"Marine Vibration Transducer" issued to J. R. Cole et
`al. also describe hydraulic seismic source generators.
`U.S. Pat. No. 3,329,930 relates to a vibrational trans- 65
`ducer that is driven at a controlled rate, two-part vibra(cid:173)
`tion by driving a piston vertically, reciprocally against
`the water medium. In this patent, a single piston is used
`
`SUMMARY OF THE INVENTION
`The present invention provides a hydraulic seismic
`source vibrator which is directed to solving the prob(cid:173)
`lems presented by prior art hydraulic seismic source
`vibrators. The present invention consists basically of an
`upper housing, a low frequency radiating surface, a low
`frequency hydraulic cylinder, a high frequency radiat(cid:173)
`ing surface, and a high frequency hydraulic cylinder. In
`operation, the low frequency pulses are generated
`through the operation of the low frequency radiating
`surface to which the high frequency radiating surface is
`connected. When low frequencies are to be generated,
`both the low frequency surface and the high frequency
`surface are operated in conjunction to provide the ef(cid:173)
`fect of one large low frequency radiating surface. The
`physical combination of the low frequency radiating
`surface with the high frequency radiating surface gener(cid:173)
`ates acoustic pulses having a frequency range from low
`frequencies to a mid range. For the operation in the
`higher frequency range, the high frequency radiating
`surface operates alone. In doing so, the high frequency
`radiating surface can provide acoustic pulses having
`frequencies from the mid range to high frequencies,
`which have not been attained by hydraulic vibrator
`systems previously.
`
`Ex. PGS 1030
`
`

`

`4,885,726
`
`3
`BRIEF DESCRIPTION OF THE ORA WINGS
`FIG. 1 is a partial sectional side view of a first em(cid:173)
`bodiment of a compound hydraulic seismic source vi(cid:173)
`brator.
`FIG. 2 is an alternative embodiment of a compound
`hydraulic seismic source vibrator which utilizes two
`low frequency hydraulic cylinders and one high fre(cid:173)
`quency hydraulic cylinder.
`FIG. 3 is a variation of the compound hydraulic seis(cid:173)
`mic source vibrator of FIG. 1 in which the low fre(cid:173)
`quency and the high frequency hydraulic cylinders are
`combined into a single cylinder.
`
`4
`nected to high frequency radiating surface 14 causing
`the generation of high frequency acoustic pulses. Low
`frequency radiating surface 12, due to its connection to
`support disk 32, high frequency hydraulic cylinder 34,
`5 and high frequency radiating surface 14, is only capable
`of generating low frequency acoustic pulses due to the
`mass involved. On the other hand, high frequency radi(cid:173)
`ating surface can be moved rapidly to generate high
`frequency acoustic pulses by the action of high fre-
`10 quency piston rod 38 due to its size and its construction
`for movement independent of the operation of low
`frequency radiating surface 12.
`In this regard, hydraulic vibrator 8 provides an
`acoustic pulse generator capable of generating both low
`DESCRIPTION OF THE PREFERRED
`15 frequency acoustic pulses and, because of its unique
`EMBODIMENT
`configuration, high frequency acoustic pulses also.
`Referring now to FIG. 2, a second embodiment of the
`The following description identifies an apparatus by
`present invention .is illustrated having similar compo-
`which both low frequency and high frequency acoustic
`nents identified with the same numerals as those in FIG.
`pulses may be generated in subsurface environments. A
`compound marine vibrator is described in which a woo- 20 1. In the embodiment of FIG. 2, two low frequency
`fer/tweeter type of arrangement is configured to permit
`hydraulic cylinders 20A and 20B are illustrated as indi-
`generation of both low frequency and high frequency
`vidually being connected to low frequency radiating
`surface 12. Cylinders 20A and 20B are mounted to
`acoustic pulses.
`Referring now to FIG. 1, a first embodiment of the
`upper housing 10 through brackets 44A and 44B, re-
`present invention is illustrated as hydraulic vibrator 8 25 spectively. Brackets 44A and 44B are further supported
`by cross piece 46. In operation, low frequency hydrau-
`which includes an upper housing 10, a low frequency
`radiating surface 12, and a high frequency radiating
`lie cylinders 20A and 20B are actuated simultaneously
`surface 14. Low frequency radiating surface 12 is con-
`causing low frequency piston rods 18A and 18B to
`nected to upper housing portion 10 through flexible
`move low frequency radiating surface 12 in unison.
`gasket 16 and low frequency piston rod 18. Low fre- 30 Low frequency piston rods 18A and 18B are connected
`quency piston rod 18 is connected to low frequency
`directly to low frequency radiating surface 12 through
`mounting disks 46A and 46B. When low frequency
`piston (not shown) within low frequency hydraulic
`cylinder 20. Low frequency hydraulic cylinder 20 is
`hydraulic cylinders 20A and 20B are not actuated, they
`mounted to upper housing 10 on a cross piece 22 and on
`maintain the position oflow frequency radiating surface
`a cap 24 at its top ledge 26. Cap 24 is mounted on upper 35 12 in a fixed position with respect to upper housing 10.
`housing 10 at its central uppermost portion. Support
`Accordingly, high frequency radiating surface 14 may
`brackets 28 are provided connecting upper housing 10
`be moved by high frequency piston rod 38 through the
`with cross pieces 22 to provide stability for low fre-
`actuation of high frequency hydraulic cylinder 34 inde-
`quency hydraulic cylinder 20. Additional support
`pendently oflow frequency radiating surface 12. This is
`brackets 30 are connected to a support disk 32 which is 40 due to the fact that high frequency hydraulic cylinder
`mounted on low frequency piston rod 18. Support
`34 is mounted on support members 36 and support
`brackets 30 are connected to low frequency radiating
`brackets 30, both of which are secured to low frequency
`surface 12 to transmit the force generated .through low
`radiating surface 12.
`frequency piston rod 18 directly to low frequency radi-
`As with the operation of the embodiment illustrated
`ating surface 12.
`45 in FIG. 1, hydraulic vibrator SA as illustrated in FIG. 2
`High frequency hydraulic cylinder 34 is mounted on
`may generate low frequency acoustic pulses through
`support disk 32 which has additional support members
`the operation oflow frequency hydraulic cylinders 20A
`36 mounted to low frequency radiating surface 12. High
`and 20B in unison, forcing the motion of low frequency
`frequency piston rod 38 is connected directly to high
`radiating surface 12, support brackets 30, support mem-
`frequency radiating surface 14 through mounting disk 50 bers 36, high frequency hydraulic cylinder 34, high
`40. High frequency radiating surface 14 is connected to
`frequency radiating surface 14 and mounting disk 40.
`low frequency radiating surface 12 through flexible When high frequency acoustic pulses are desired, actua-
`gasket 42.
`tion of high frequency hydraulic cylinder 34 permits
`motion of high frequency radiating surface 14 indepen-
`In operation, when low frequency acoustic pulses are
`to be generated, hydraulic cylinder 20 is actuated which 55 dent of low frequency radiating surface 12.
`drives low frequency piston rod 18. Movement of low
`In operation, for both the embodiments of FIG. 1 and
`frequency piston rod 18 forces low frequency radiating
`FIG. 2, any movement of the low frequency hydraulic
`surface 12 along with support disk 32, high frequency
`cylinder piston rod 18 in FIG. 1 or 18A and 18B in FIG.
`hydraulic cylinder 34, mounting disk 40, and high fre-
`2 is transmitted directly to the low frequency radiating
`quency radiating surface 14 to move in unison to gener- 60 surface 12, the high frequency hydraulic cylinder 34
`ate low frequency acoustic pulses. During high fre-
`and the high frequency radiating surface 14 only. Any
`quency operation, low frequency piston rod 18 is main-
`movement of the high frequency hydraulic cylinder
`tained in a stable position, holding support disk 32 fixed.
`piston rod 38 is transmitted directly to the high fre-
`Accordingly, high frequency hydraulic cylinder 34 is
`quency radiating surface 14. Thus, the low frequency
`also held fixed allowing high frequency piston rod 38 to 65 hydraulic system is optimized to drive the low fre-
`move independent of support disk 32 and low frequency
`quency hydraulic cylinder over a range of frequencies
`radiating surface 12. In operation, high frequency piston
`from very low frequency, long stroke, up to intermedi-
`rod 38 moves, moving mounting disk 40 which is con-
`ate frequencies. The high frequency hydraulic system is
`
`Ex. PGS 1030
`
`

`

`4,885,726
`
`6
`5
`same numbers as they appear in FIG. 1. The top portion
`optimized to drive the high frequency hydraulic cylin-
`der over a range of frequencies from intermediate fre-
`of a main cylinder housing 52 is attached to the upper
`quencies up to very high frequencies. The stroke of the
`housing 10 of a hydraulic vibrator or the like. Main
`high frequency hydraulic cylinder is relatively short, to
`cylinder housing 52 has a lip 54 which may be attached
`minimize the volume of hydraulic oil between a hydrau- 5 to upper housing 10 through the use of bolts 56 or by
`lie servovalve and the face of the hydraulic cylinder
`some other method known in the art such as welding,
`ram. Also, the structural mass is very small so that the
`etc. Illustrated as a portion of main cylinder housing 52
`system can be driven at very high frequencies. The
`is hydraulic servo control 58 with inlet/outlet passages
`outer housing of low frequency hydraulic cylinder 20
`60 and 62. Passages 60 and 62 feed to open areas 64 and
`and that of hydraulic cylinder 20A and 20B in FIG. 2 is 10 66, respectively, between main cylinder housing 52 and
`attached to the upper housing 10 of vibrators 8 and SA,
`a low frequency piston actuator 68. Low frequency
`respectively, in order to minimize the mass that the low
`actuator piston 68 may be connected to low frequency
`frequency cylinder is required to move. Also, the outer
`radiating surface 12 or to any similar device which is to
`housing of high fr!:quency hydraulic cylinder 34 rather
`be actuated at low frequencies Piston 68 is ftxed to
`than high frequency piston rod 38 is attached to low 15 surface 12 by bracket 70 through bolts 72. The top
`frequency radiating surface 12 in order to minimize the
`portion of low frequency actuator piston 68 includes
`mass that the high frequency cylinder is required to
`high frequency servo control 74 which includes inlet
`move.
`outlet passages 76 and 78 that feed open areas 80 and 82
`The upper housing of the compound vibrator is rela-
`located between low frequency actuator piston 68 and
`tively heavy as compared with the radiating surfaces in 20 high frequency actuator piston 84. High frequency pis-
`order to maximize the amount of energy that is radiated
`ton 84 may be connected to a high frequency radiating
`in a downward direction. Vibrators 8 and SA are also
`surface 14 or the like by any method known in the art.
`larger in diameter than conventional marine vibrators
`In operation, low frequency actuator piston 68 and
`so that a large amount of energy can be output at low
`high frequency actuator piston 84 may be connected to
`frequencies. This, combined with superior high fre- 25 any surface which requires vibrating or back forth mo-
`quency performance, results in a fewer number of vibra-
`tion of the frequencies these two pistons are designed to
`tors being required for a given total energy output, as
`generate. For low frequency operation, servo control
`compared with conventional marine vibrators. The
`58 forces hydraulic fluid through passage 60 into open
`number of power plants, amount of handling equip-
`area 64 to force low frequency actuator piston 68
`ment, and number of persons required to operate the 30 towards its full downward position. When this has been
`equipment can also be less. Compound marine vibrators
`accomplished, servo control 58 reverses, permitting
`8 and SA may be operated in numerous modes. For
`fluid to exit open area 64 through passage 60 while
`example, marine vibrators 8 and SA may be operated by
`forcing fluid into open area 66 through passage 62.
`actuating only the low frequency hydraulic cylinder 20
`Since the combined length of open areas 64 and 66
`or 20A and 20B. The vibrator thus functions as a con- 35 comprise a long stroke distance, piston 68 will move
`ventional marine vibrator. High frequency radiating
`surfaces 12 and 14 at a low frequency rate.
`surface 14 would not move with respect to low fre-
`When actuation of surface 14 at a high frequency is
`quency surface 12. Thus, the frequency bandwidth
`desired, servo control 74 is used to force fluid through
`would be limited to low to mid-range frequencies.
`passage 76 into open area 80 forcing high frequency
`A second mode in which marine vibrators 8 or SA 40 actuator piston 84 to its fully outwardly extended posi-
`may be operated is one in which the vibrator could start
`tion. Upon reaching its fully extended position, hydrau-
`a sweep at very low frequencies with the high fre-
`lie fluid is then forced into open area 82 through passage
`quency hydraulic cylinder 34 fixed or with the same
`78 while hydraulic fluid occupying open area 80 is per-
`sweep as the low frequency hydraulic cylinder 20. As
`mitted to exit through passage 76. Thus, an in and out
`intermediate frequencies are reached, the low fre- 45 motion is provided through high frequency actuator
`quency sweep system could be stopped and the high
`piston 84 to vibrate surface 14 at a high frequency. The
`frequency system would continue to the desired level.
`high frequency is accomplished through two aspects.
`A third mode in which the marine vibrator system
`First, high frequency actuator piston 84 together with
`may be operated is one in which the low frequency and
`surface 14 constitute a low mass. Second, the stroke
`high frequency systems could be actuated simulta- 50 length of high frequency actuator piston 84 is short, that
`neously with two different sweeps. For example, the
`is, the total length of open areas 80 and 82, when high
`low frequency system could sweep through a frequency
`frequency actuator piston 84 is centered as illustrated in
`range of 3 to 50 Hz at the same time that the high fre-
`FIG. 3 is relatively short when compared to the stroke
`quency system was sweeping with a frequency rang of
`length of low frequency piston 68.
`50 to 150 Hz.
`Thus, a single cylinder assembly may be used to gen-
`Finally, a fourth mode in which marine vibrators 8 or
`erate both low frequencies such as 5 to 50 Hz and high
`SA could be operated is one in which the vibrator func-
`frequencies such as 50 to 150 Hz through the use of the
`tions as a conventional marine vibrator by actuating
`design of the present invention.
`only the high frequency system.
`Although the present invention was illustrated by
`Hydraulic and electrical control circuitry required to 60 way of preferred embodiments, each describing a com-
`produce and control the vibrator sweeps are not illus-
`pound vibrator with two radiating surfaces, the present
`trated since the actual controls are conventional and are
`invention would apply to any number of radiating sur-
`considered to be standard for the industry and under-
`faces. Multiple arrays of radiating surfaces could be
`stood by one skilled in the art
`superimposed on the largest diameter radiating surface.
`Referring now to FIG. 3, a compound hydraulic 65 In addition, multiple radiating surfaces could be con-
`actuator is illustrated. This actuator may be used in the
`nected directly to the upper housing rather than to
`embodiment of FIG. 1. Reference surfaces and similar
`another radiating surface. Furthermore, the vibrators
`portions of the actuator have been identified with the
`illustrated can also be used for land seismic exploration
`
`55
`
`Ex. PGS 1030
`
`

`

`4,885,726
`
`5
`
`10
`
`7
`The lower surface radiating surfaces could be the com(cid:173)
`pound base plate of a land vibrator. Thus, the present
`invention should not be limited to the described em(cid:173)
`bodiments but only limited by the following claim ele-
`ments and their equivalents.
`I claim:
`1. A compound seismic source comprising:
`a housing including an upper section, a low frequency
`radiating section and a high frequency radiating
`section;
`a low frequency hydraulic cylinder mounted on said
`upper section for vibrating said low frequency
`radiating section; and
`a high frequency hydraulic cylinder mounted on said
`low frequency radiating section for vibrating said 15
`high frequency radiating section.
`2. The compound seismic source according to claim 1
`wherein said low frequency radiating section is con(cid:173)
`nected to said upper section by a flexible seal and said
`high frequency radiating section is connected to said 20
`low frequency radiating section by a flexible seal.
`3. A compound seismic source vibrator comprising:
`a housing having an upper section and a low fre(cid:173)
`quency radiating section;
`a low frequency means for vibrating said low fre- 25
`quency radiating section;
`a high frequency radiating section flexibly connected
`to said low frequency radiating section; and
`a high frequency means rigidly secured to said low
`frequency radiating section for separately vibrating 30
`said high frequency radiating section.
`4. The compound-seismic source according to claim 3
`wherein said low frequency radiating section is con(cid:173)
`nected to said upper section by a flexible seal.
`S. The compound seismic source according to claim 3 35
`wherein said low frequency means includes a hydraulic
`cylinder fixed to said upper section.
`6. The compound seismic source according to claim S
`wherein said low frequency means includes a piston
`having a rod connected to said low frequency radiating 40
`section.
`7. The compound seismic source according to claim 3
`wherein said high frequency means includes a hydraulic
`cylinder fixed to said low frequency radiating section.
`8. The compound seismic source according to claim 7 45
`wherein said high frequency means includes a piston
`having a rod connected to said high frequency radiating
`section.
`9. The compound seismic source according to claim 3
`wherein said low frequency radiating section creates 50
`acoustic waves in a range from low frequencies to inter(cid:173)
`mediate frequencies.
`10. The compound seismic source according to claim
`3 wherein said high frequency radiating section creates
`acoustic waves in a range from intermediate frequencies 55
`to high frequencies.
`11. The compound seismic source according to claim
`3 wherein said high frequency radiating section is con(cid:173)
`nected to move in unison with said low frequency radi(cid:173)
`ating section when said low frequency means vibrates 60
`said low frequency radiating section.
`12. A method for generating seismic acoustic waves
`over a wide frequency range in a subsea environment
`comprising the steps of:
`providing a housing having an upper section, a low 65
`frequency radiating section and a high frequency
`radiating section coupled to the low frequency
`radiating section;
`
`8
`generating low frequency acoustic waves by vibrat(cid:173)
`ing the low frequency radiating section .and the
`coupled high frequency radiating section; and
`generating high frequency acoustic waves by inde(cid:173)
`pendently vibrating the high frequency radiating
`section.
`13. The method according to claim 12 wherein the
`step of generating low frequency acoustic waves in(cid:173)
`cludes the steps of:
`providing a hydraulic cylinder fixed to the upper
`section of the housing; and
`vibrating the low frequency radiating section to pro(cid:173)
`vide acoustic waves in a range from low frequen(cid:173)
`cies to intermediate frequencies.
`14. The method according to claim 13 wherein said
`step of generating low frequency acoustic waves in(cid:173)
`cluded the steps of:
`generating acoustic waves having their frequency
`increase sequentially at a predetermined rate.
`15. The method according to claim 12 wherein the
`step of generating high frequency acoustic waves in(cid:173)
`cludes the steps of:
`providing a hydraulic cylinder fixed to the low fre(cid:173)
`quency radiating section; and
`vibrating the high frequency radiating section to
`provide acoustic waves in a range from intermedi(cid:173)
`ate frequencies to high frequencies.
`16. The method according to claim 15 wherein said
`steps of generating high frequency acoustic waves in(cid:173)
`cludes the step of:
`generating acoustic waves having their frequency
`increase sequentially at a predetermined rate.
`17. A multiple frequency range marine seismic trans(cid:173)
`ducer, comprising:
`an upper housing;
`a low frequency cylinder means rigidly secured to
`said upper housing and extending a low frequency
`piston means;
`a low frequency radiating surface that is rigidly con(cid:173)
`nected to said low frequency piston means;
`a high frequency cylinder means that is rigidly con(cid:173)
`nected to said low frequency piston means and
`extending a high frequency piston means; and
`a high frequency radiating surface rigidly secured to
`said high frequency piston means, said high fre(cid:173)
`quency radiating surface being generally co-planar
`with and concentric to said low frequency radiat(cid:173)
`ing surface;
`whereas the low frequency cylinder means recipro(cid:173)
`cates both low and high frequency radiating sur(cid:173)
`faces, and the high frequency cylinder means recip(cid:173)
`rocates only the high frequency radiating surface.
`18. A seismic transducer as set forth in claim 17
`which is further characterized to include:
`support means rigidly joining said low frequency
`piston means and said high frequency cylinder
`means in axial alignment, said support means ex(cid:173)
`tending rigid connection to said low frequency
`radiating surface.
`19. A seismic transducer as set forth in claim 17
`which is further characterized in that:
`said upper housing is shaped generally round and
`concave downward to defme a lowermost perime(cid:173)
`ter;
`said low frequency radiating surface is shaped gener(cid:173)
`ally round with a circularly open center and con(cid:173)
`cave upward to defme an uppermost outer perime-
`
`Ex. PGS 1030
`
`

`

`4,885,726
`
`9
`ter adjacent said upper housing lowermost perime(cid:173)
`ter; and
`flexible sealing means is connected between the adja(cid:173)
`cent upper housing perimeter and low frequency
`radiating surface perimeter.
`20. A seismic transducer as set forth in claim 18
`which is further characterized in that:
`said upper housing is shaped generally round and 10
`concave downward to defme a lowermost perime-
`ter;
`said low frequency radiating surface is shaped gener(cid:173)
`ally round with a circularly open center and con- 15
`cave upward to defme an uppermost outer perime(cid:173)
`ter adjacent said upper housing perimeter; and
`
`10
`flexible sealing means is connected between the adja(cid:173)
`cent upper housing perimeter and low frequency
`radiating surface perimeter.
`21. A seismic transducer as set forth in claim 19
`5 which is further characterized in that:
`said high frequency radiating surface is circular and
`closely received within the circular open center of
`said low frequency radiating surface; and
`second flexible sealing means is connected to seal
`between the high frequency radiating surface and
`the circular open center of said low frequency
`radiating surface.
`22. A seismic transducer as set forth in claim 17
`wherein said low frequency cylinder means comprises:
`at least two hydraulic actuators connected in bal(cid:173)
`anced relationship relative to the upper housing.
`* * * * *
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`Ex. PGS 1030
`
`