US3789951A

US3789951A - Vibrator system for generating seismic waves in the earth

Info

Publication number: US3789951A
Application number: US00223896A
Authority: US
Inventors: D Silverman
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-02-07
Filing date: 1972-02-07
Publication date: 1974-02-05
Anticipated expiration: 1991-02-05

Abstract

This invention describes a vehicle-mounted electrohydraulic vibrator system useful for generating seismic waves in th earth. It comprises a baseplate supported from the vehicle by downwardly extending means and attached to the baseplate through compliances. The vibrator system comprises four hydraulic cylinders and pistons operatively mounted in the cylinders. The pistons are attached to the baseplate through a first frame and are supported thereby. The cylinders are connected to a second frame placed above and resting on the vibrator. The second frame is adapted to support a mass. The mass can be a separate discrete mass of metal, or alternatively, the second frame can be clamped to the bed of the vehicle, in which case the vehicle becomes the reaction mass. If the vehicle has a drive shaft, two of the cylinders are placed on each side of the drive shaft. The pistons in the cylinders are single-acting. That is, a first piston in a first cylinder is pushed downwardly and a second piston in a second cylinder is pushed upwardly with respect to the cylinders when pressure fluid is introduced into the cylinders. The four single-acting vibrators arranged in rectangular spacing provide an alternating vertical force acting at the center of the rectangle.

Description

United States Silver-man atent 1 Feb. 5, 1974 SEISMIC WAVES IN THE EARTH Daniel Silverman, 5969 S. Birmingham, Tulsa, Okla. 74105 221 Filed: Feb. 7, 1972 211 Appl. No.: 223,896

[76] Inventor:

Primary Examiner--Samuel Feinberg Assistant Examine'rJ. V. Doramus [5 7] ABSTRACT This invention describes a vehicle-mounted electrohydraulic vibrator system useful for generating seismic waves in th earth. It comprises a baseplate supported from the vehicle by downwardly extending means and attached to the baseplate through compliances,

The vibrator system comprises four hydraulic cylinders and pistons operatively mounted in the cylinders. The pistons are attached to the baseplate through a first frame and are supported thereby. The cylinders are connected to a second frame placed above and resting on the vibrator. The second frame is adapted to support a mass. The mass can be a separate discrete mass of metal, or alternatively, the second frame can be clamped to the bed of the vehicle, in which case the vehicle becomes the reaction mass. If the vehicle has a drive shaft, two of the cylinders are placed on each side of the drive shaft.

The pistons in the cylinders are single-acting. That is, a first piston in a first cylinder is pushed downwardly and a second piston in a second cylinder is pushed upwardly with respect to the cylinders when pressure fluid is introduced into the cylinders; The four single-acting vibrators arranged in rectangular spacing provide an alternating vertical force acting at the center of the rectangle.

24 Claims, 13 Drawing Figures VIBRATOR SYSTEM FOR GENERATING SEISMIC WAVES IN THE EARTH DESCRIPTION OF THE PRIOR ART The prior art is represented by the following US Pats., Nos. 2,910,134 Crawford et al.; 3,159,233 Clynch et al.; and 3,306,391 Bays.

In the geophysical exploration industry using the seismic method of mapping subsurface geology, there has been, in recent years, an increase in the use of a method of seismic prospecting called the Vibroseis system. This method, unlike the conventional explosive impulse method, uses a vibratory signal involving many cycles of alternating pressure against the surface of the earth. The frequency of the alternations generally varies with time, the signals being called swept frequency signals, which typically have a duration of from to 7 seconds, and a frequency range of from 20-100 cps.

This swept frequency seismic signal in the earth is generated by an electrohydraulic vibrator supported on a baseplate which is pressed into contact with the earth by a portion of the weight of the truck or other vehicle which transports the vibrator. The vibrator comprises a cylindrical mass (of weight up to 5,000 pounds) with a cylindrical bore containing a piston. Piston rods extend above and below the piston and are attached to a frame which surrounds the mass and is supported on the baseplate.

The vibrator is generally mounted near the middle of the truck or other transport vehicle. Those vehicles, such as trucks, which have a drive shaft, require that the vibrator be mounted on a tall structure, or tower, which is attached to the base plate, the legs of which straddle the drive shaft. The vibrator is mounted on top of the tower, where it is generally at an elevation above the bed of the truck. This large mass mounted on the high tower provides an unstable condition, and is a weakness of the prior art designs. Also, the large mass of the tower adds to the mass of the moving system and detracts from the oscillating force that can be applied to accelerate the earth. It is well known that one measure of the energy transmitted into the earth is the amplitude of motion of the baseplate. Also, the amplitude of motion of the moving system comprising piston, piston rods, frame, tower and baseplate for a constant force input, varies inversely to the mass of the moving system. Therefore, any excess mass in the moving system detracts from the force that can be applied to accelerate the earth.

SUMMARY OF THE INVENTION It is a primary object of this invention to provide an electrohydraulic vibrator for mounting on a vehicle with a drive shaft, wherein the vibrator is mounted at low elevation, directly on the baseplate.

It is a further object of this invention to provide a seismic vibrator which has a moving system of minimum mass.

It is a still further object of this invention to provide a seismic vibrator in which a separate reaction mass for the vibrator is not required, but in which the mass of the vehicle serves both as a hold-down mass and as the reaction mass for the vibrator.

It is a still further object of this invention to provide a vibrator system in which a plurality of vibrators are operated in parallel and which include means to accurately synchronize all of the vibrators so as to be precisely in-phase.

It is a still further object of this invention to provide a vibrator system that has a higher frequency of operation than conventional systems.

These and other objects are accomplished and the limitations of the prior art devices are overcome in the design of the present invention, in which four short vertical hydraulic cylinders are used, with four singleacting pistons slidably received therein. The four cylinders are positioned two on each side of the drive shaft in the corners ofa rectangle. Two of the cylinders, (on a diagonal of the rectangle) are oriented so that on the application of hydraulic pressure, the pistons move upwardly, and in the other two, (on the other diagonal) the pistons move downwardly, with respect to the cylinders. The thickness of the cylinder walls is no greater than that required for pressure and mechanical requirements, as the mass is not directly associated with the cylinders, as in the prior art.

There is a first frame to which the extended ends of the pistons are connected. There is a second frame to which the cylinders are connected. Either the first or second frame can be connected to the baseplate, in which case the other frame is connected to the mass. In order to minimize the mass of the moving system, the first frame, (connected to the pistons) is preferably connected to the baseplate, and the second frame (connected to the cylinders) supports the mass above the cylinders. The axes of the cylinders are parallel to each other and perpendicular to the baseplate.

In this design of the vibrator, the pistons and cylinders are substantially less than half as tall as the cylinder in the prior art. Also, because two pistons push in parallel and two pull in parallel, they can be of smaller diameter. The mass of the first frame, plus pistons and baseplate, which constitute the moving system, is thus very much less than that of the prior art systems. Therefore, a much smaller force is required to accelerate the moving system, leaving a larger fraction of the total force output of the vibrator to accelerate the earth and to generate seismic waves. Furthermore, the lighter mass permits higher frequency of operation. Also, as will be described later, since the cylinders are smaller, the fluid volume to each cylinder is smaller, and conventional valves will provide a higher frequency of operation. These are some of the principal operating benefits of this invention.

' Considering that the first frame connects the pistons to the baseplate, then the second frame connects the cylinders to the mass. The mass can be a separate discrete volume of metal mounted on the second frame. However, since there is a practical limit to the weight of such a mass that can conveniently be transported, in this invention the mass of the vehicle is used both to press the baseplate into firm contact with the earth, and to provide the reaction mass for the vibrator. The second frame extends upwardly to the level of the truck bed, and after the baseplate has been positioned on the earth and the truck frame raised, the second frame is removably clamped to the truck bed. One way to do this provides a vertical post, as part of the second frame, with a plurality of hydraulic rams attached to the truck frame that move radially inwardly to grasp the post and hold it rigidly in association with the frame of the truck.

The preferred design makes use of four single-acting pistons in short cylinders, two on each side of the drive shaft. However, it is possible to use two cylinders, one on each side of the drive shaft with double-acting pistons. Here again, the pistons are attached to the first frame, the cylinders to the second frame and the second frame clamped to the truck frame.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects of this invention and a clear understanding of the principles of the invention will be evident from the following description taken in conjunction with the appended drawings, in which:

FIG. 1 shows a generalized view of the side elevation of a transport truck supporting the vibrator of this invention.

FIG. 2 shows a transverse section taken along the plane 2-2 of FIG. 1.

FIG. 3 shows a horizontal section taken along the plane 3-3 of FIG. 2.

FIG. 4 shows a horizontal section taken along the plane 4-4 of FIG. 2.

FIG. 5 is a side elevation taken along the plane 55 of FIG. 2.

FIGS. 5A and SB illustrate details of pistons and clamps.

FIG. 6 is a plan view taken along the horizontal plane 66 of FIG. 2.

FIG. 7 illustrates an alternate embodiment of a clamping mechanism.

FIG. 8 illustrates an embodiment of this invention utilizing two double-acting pistons and cylinders.

FIG. 9 illustrates a way to positively synchronize the valves on cylinders which are spacially separated from each other.

FIG. 10 illustrates a method of minimizing leakage of pressure fluid from the cylinders past the pressure seals.

FIG. 11 illustrates a closed, series, hydraulic drive for DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, the numeral 10, represents generally the hold-down apparatus, numeral 11 represents generally the truck transport vehicle, numeral 12 represents generally the vibrator lifting apparatus, the numeral 14 represents generally the vibrator system, numeral 16 the second frame for supporting the mass, and numeral 18 the mechanism that clamps the second frame to the truck.

The vibrator system 14 is mounted on a baseplate 20 which is supported from the vehicle 11 by lifting means 12. The lifting means 12 comprises a cylindrical rod 24 which is slidably received in a vertical guide tube 29, fastened to the truck frame at its lower end. The rod 24 has a crossarm 26 at its bottom end which is attached to the compliances 22 which are attached to the baseplate 20. The rod 24 at its upper end supports two piston rods 30 which slide in hydraulic cylinders 28, 28', which are attached (FIG. 2) by means 35 to the frame 62 of the truck. By pulling down on the piston rods 30, the rod 24 is forced down until the baseplate hits the surface 17 of the earth 19. If the rods 30 are pulled down farther, the truck body will be lifted until two of the wheels 23 are off the ground, and part of the weight of the truck will be supported on the compliances 22 pressing down on the baseplate 20. This piston of the apparatus is well known in the art and forms no part of this invention.

The vibrator system illustrated in FIGS. 2-5 comprises four cylinders equipped with single-acting

pistons

32, 32, 34, 34'. These are positioned in the corners of a rectangle.

Cylinders

32, 32 are on one diagonal. The other two cylinders 34, 34' are on the second diagonal. Pistons 36 in

cylinder

32, and 36 in cylinder 32 are adapted to move downwardly with respect to their cylinders on the application of pressure fluid. The

pistons

38 and 38 in

cylinders

34 and 34 respectively are adapted to move upwardly with respect to the cylinders on the application of pressure fluid.

The single-acting pistons can be simple rods inserted and sealed into the cylinders. At the expense of more seals, the pistons (for example 36 in FIG. 5A) can have a smaller diameter extension (36A). This permits more firm attachment of the pistons to the first frame 40 which ties the pistons to the baseplate.

On the other side of the drive shaft is a second set of pistons and cylinders identical to the two just described and shown in FIG. 5. However, on the opposite side (right side of the truck), the forward piston 36 moves downwardly, while on the left side the forward piston 38 moves upwardly, and vice versa for the rearward pistons.

The cylinders (FIG. 5) 34 and 32 are joined to a second frame 16, which has upstanding legs 44 which support plate 46, which ties together the two sets of two cylinders. The first frame 40 may have cross arms (not shown) which tie together the two sets of pistons for greater rigidity. The total force of the pressure fluid acts on the pistons and through them to the frame 40 and thus to the baseplate and to the earth. Very large forces are generated and the

frames

40 and 16 must be sufficiently rigid to transmit this force without deformation. For simplicity and clarity of drawings, only simple frames are shown, although those skilled in the art will know how to design strong structural frames for this purpose.

This design of vibrators differs in a number of respects from the conventional prior art devises which utilize a single cylinder, which is formed inside of the cylindrical mass and has a double-acting piston system. Furthermore, these prior art vibrators are mounted high on top ofa structural steel tower. The frame which supports the piston rods, and the tower are massive because the pistons rods must be commensurate with the size of the mass, etc. In this design the pistons are single acting so that the length of the piston rods is short and the first frameis short. There is no tower, and thus the overall mass of the moving system is a minimum.

If desired, the second frame 16 can support a separate discrete volume of metal, such as a cube, that would rest upon and be fastened to the horizontal plate 46. However, in this invention the preferred embodiment involves the use of part of the mass of the vehicle as the reaction mass for the vibrator. This is illustrated in FIGS. 2, 5 and 6. A long rigid vertical post 48 is supported from the plate 46 of the second frame 16. When the baseplate is pressed into intimate contact with the earth, the post will extend up through an opening 66 in the bed of the truck. A plurality of horizontal hydraulic rams 56 (two of which are shown) are. slidable in cylinders 54 which are attached rigidly to the bed of the with the electrical signal to the valve control system. These systems work well when, as in the prior art, there is only a single vibrator. Whenthere are two or more vibrators, each mounted on separate trucks, then each vibrator requires the same feedback control to maintain the phase of each of the vibrators in constant phase relation with the electrical signal, and therefore in constant phase relation with each other.

The principal difference between this invention and the prior art devices, is that there are more than a single cylinder, and this vibrator system may contain two or more vibrators, each having a cylinder and a piston. These are spaced apart on the baseplate. To maintain them in proper phase relation it is important that the valves which control the flow of pressure fluid are held precisely in-phase. This I do, by physically restricting and controlling the motion of these valves by tying them together with a mechanical or hydraulic system. One form of such a mechanical control system is shown in FIG. 9.

A hydraulic actuator 100 has a cylinder 101 and a piston 102 with two

piston rods

103, 104. Pressure fluid is introduced cyclically into the cylinder in accordance with an electrical signal by electrohydraulic control means well known in the art. Such electrohydraulic controls are available on the market and need no further description. Shown are two pressure

fluid control valves

112, 114 which are to be maintained in constant phase relation with the actuator 102 to control pressure fluid flow to the two cylinders (not shown) as is well known in the art. Each of the valves includes a cylinder 113 and a valve spool 116, fluid connection to the vibrator cylinder 120, and

fluid connection

121, 122 to the pressure fluid high and low pressure reservoirs, not shown. The

piston rods

103, 104 of the actuator 100 are connected by flexible tension cables 106 to the

piston rods

117, 118, etc. of the

valves

112, 114, etc. by means of pulleys 108-111, etc. to provide a closed tension circuit. With suitable tension in the system and a minimum of stretch in the cable 106, and a minimum ofmass in the valve spools 116, they will move exactly in-phase with the piston of the actuator 100.

In order to ensure that all of the slack is out of the tension cable 106,

pulleys

123, 124, 125 may be used in conjunction with screw 126 attached to the shaft of pulley 125, bracket 127 attached to the frame of the vibrator and nut 128 to maintain a static tension in the cable greater than the alternating forces applied by the piston 102.

A similar synchronizing control system, can be designed in which hydraulic liquid is used as the control medium in place of the tension cable 106.

The operation of the spool valves in FIG. 9 is well known in the art and need not be described further. Although only two valves are shown, as many valves as desired can be connected through series cables, rods or hydraulic conduits and actuators, so that they are forced to operate in constant phase with each other.

Although the details have not been described in this application, it will be clear that the well known control systems using displacement or velocity sensors on the baseplate and on the piston cylinder combinations to control the phase of the baseplate in synchronism with the signal applied to the vibrator, can be used with the vibrator system of this invention. In the prior art such control systems have been applied only to the single piston-cylinder systems. With the use of the valve phase controls as described in conjunction with FIG. 9, it is not necessary to provide duplicate electronic control systems and sensors on each vibrator. Only one such control system would be needed since all of the valves and thus all of the vibrators would operate precisely together. Thissingle control could be applied to one of the plurality of vibrators, or it could be applied between the first and a second frame, which respectively are fastened to the baseplate and the mass.

In the prior art vibrators with a single cylinder and two piston rods, certain volumes of liquid at a selected pressure are required to generate the desired force. Using present day valve art, there is a limit to the volume of lquid which can be controlled by the valves as a function of frequency. This limitation sets an upper limit on the frequency of operation. In this invention, because only half as much volume is required for each cylinder, with the same valves, a much higher frequency of operation is possible. This feature combined with the lower mass of the moving system provides a higher frequency vibrator than the prior art systems.

FIG. 10 indicates a detail of the piston and cylinder construction which relates to the sealing of the pistons in the cylinders. The piston 168 is fastened to the baseplate 170. The cylinder 164 is fastened to the second frame which is fastened to the mass. High pressure hydraulic liquid is applied to cylinder chamber 169 through pipe 177,

valves

176, 182 and through pipe 174. At the same time the pressure fluid is applied through pilot pipe 178 and through the opening 180 through the cylinder wall, in the space between the two O-

ring seals

165, 166. Thus, in the very thin annular space between the piston and cylinder there is a hydraulic pressure which is, at all times, the same as that in the cylinder chamber 169. Thus there is no pressure difference across the seal ring 166 and therefore no leakage across that seal ring. If desired, the pipe 178 can alternatively be connected through pipe 178 to the source of pressure fluid through pipe 177. With the pipe 178 connected to pipe 177 and maximum pressure applied to pipe 174, the valve 182 can be closed and thereafter there will be no leakage of pressure from chamber 169. This feature can be used in connection with the cylinders and pistons of the clamping means described in connection with FIG. 7.

While I show clamping means for releasably clamping the second frame, through post 48 to the truck frame that operates on the basis of hydraulic force, it is clear that motor driven screw means can of course be equally well used. The pistons and cylinders of FIGS. 6, 7, are, in effect, hydraulic jacks, and motor driven screw jacks, or equivalent means, could be substituted for them.

In FIG. 11 is illustrated a hydraulic system that obviates the need of valves on each cylinder. Since the pistons are all connected to a rigid first frame 196, fluid flow through pipe 214 into cylinder chamber 216 will drive piston 193 downwardly, and with it, the first frame 196, attached to baseplate 20. As the frame 196 moves down, piston 194 presses fluid out of chamber 218 into pipe 220. Now, if piston 212 in cylinder 210 is moved to the left, it will force liquid from chamber 213 into pipe 214, and chamber 216, and will accept fluid from chamber 218 through pipe 220 into chamber 222. The piston 222 can be driven through piston rod 202 by piston 201 in actuator cylinder 200. Piston 201 is driven by pressure fluid controlled by valve means truck by clamps 68 and bolts 70 (FIGS. 5 and 6) or by other means well known in the art. The rams are oriented radially toward the post 48. In this embodiment the post 48 is shown as of square cross-section. It is convenient therefore to use 2, or 4 rams, one directed against each face of the post. The surfaces of the post are knurled or roughened 52, or have threads, or V notches (FIG. 5B) etc., cut into the post, with matching surfaces on the faces of the rams 56. It is possible also, though not shown, to have two upright posts adjacent the frame post 48, the former fastened securely to the bed of the truck, with a tapered horizontal opening formed through the three contiguous posts. The ram then would have a tapered rod of the same taper, which would be inserted and pressed tightly into the tapered seat, to securely lock the mass supporting post to the truck frame.

Because there may be slight misalignments due to irregularities in the surface on which the base plate rests, the faces of the rams, etc., and the tapered rod could be on a swivel or ball-and-socket mechanism so as to adjust to the precise position of the baseplate and vibrator. Shown in FIG. 5B are ball and socket means 58 in the ends of the rams. These can be held in place for example by rings 59 attached to the rams 56.

After the baseplate is placed on the earth, part of the weight of the truck is applied through compliances 22, by lifting the rear end of the truck, as is well known in the art. The rams 56 are then closed, at light fluid pressure, until all of the rams are in contact with the post 48. This light fluid pressure serves to position all pistons in contact, without disturbing the natural position of the post 48. Then the fluid pressure is increased until the pistons are pressed very tightly against the post. In this condition, because of the roughness of the post and piston faces, there will be no slippage of the post with respect to the pistons. And, since the cylinders are securely anchored to the truck frame, the truck mass now becomes the reaction mass for the vibrator.

There may be some natural flexibility in the frame of the truck. This may have to be reinforced with stiffening members, to provide a rigid mass. It is possible also to combine a small mass (such as the second frame itself, or the second frame plus a small mass) directly connected to the cylinders, and the large mass of the truck. This can be a direct connection or with controlled compliances between the small mass and the truck (which could be in the truck frame itself). Of course there will be small resonances of piping and frames on the truck itself which might respond to the impressed oscillatory forces. These can be reinforced or isolated as is well known in the art. The compliance in the connection between the post 48 and the truck (if present), might be designed to provide an overall response to the system to improve the wave shape of the seismic signal generated in the earth.

It will be clear, that while I show the first frame, which is attached to the baseplate, also attached to the pistons, and the second frame which is attached to the mass also attached to the cylinders, this is a matter of choice, and the pistons could just as well be connected to the second frame, and the cylinders to the first frame. The choice is preferably made so that the mass of the moving system is the least possible. Since the pistons are of smaller mass than the cylinders they should be connected to the first frame. Also, as will be discussed later, the valves which control the pressure fluid should be attached to the cylinders, and they should be attached to the mass, so as to have as little movement as possible.

Also, while I show a square post 48, a post of any number of faces (three or more) or a round post could be used with appropriate numbers of rams and corresponding shapes of clamping faces of the rams.

In FIG. 7 I show another embodiment of a clamp means for removably attaching the second frame to the truck. This shows the post 48 with a sphere 72 adjustably attached to the post, such as by threads, not shown. There are two spherical-

seat plates

75, 76 above and below the sphere. These are held lightly together and to the sphere by bolts 89 and springs 90. There is a structural frame 78 attached to the truck frame 60, and a plurality of

vertical cylinders

80, 82 and

pistons

84, 86 below and above the

plates

75, 76. There should be two sets of at least three cylinders and pistons spaced angularly about the post 48. The upper and lower pistons are preferably in alignment.

In operation, after the baseplate is set and the truck lifted, the lower pistons 84 are raised and the upper pistons 86 are lowered, by introducing low pressure fluid through

valves

91 and 88. When they are all in firm contact with the upper and

lower plates

75, 76, the pressure is raised. When full pressure has been applied, there is still a small gap 77 to permit the full pressure to be applied to the sphere and the post. Then

valves

88 and 91 are closed. The post 48 is now locked to frame 78 and to the bed of the truck.

Other means can, of course, be used to removably clamp the second frame of the vibrator to the truck frame. An important feature of this invention lies in the use of such releasable or removable clamping means to obviate the need of a separate, discrete, heavy, costly reaction mass for the vibrator. It is also clear that a removable clamping means is required, which is released at all times except when the vibrator is operating. A continuously applied clamping means cannot be used since the spacing between vibrator and truck is different when the vibrator is raised for transport, and lowered for operation.

While my preferred embodiment is to use 4 cylinders and pistons as shown in FIGS. 2, 3, 4, each of which are single-acting, and positioned two on each side of the drive shaft, I contemplate also using two double-acting pistons in cylinders, one on each side of the drive shaft. This is shown schematically in FIG. 8. There are two cylinders 87 containing two pistons 85. Each piston has two

piston rods

92, 93. These are attached to a first frame 94 which is attached to the baseplate 20. The cylinders 87 are attached to second frame 95, which has risers 44 which attach to plate 46 as in FIG. 2. The system of FIG. 8 can, of course, carry a separate reaction mass mounted on plate 46, although preferably, the plate 46, through post means 48 is removably clamped to the truck frame to use the truck as the reaction mass. The driveshaft 64 operates in the space between the cylinders.

In the prior art devices, a single cylinder and piston system has been used, with a single valve assembly to simultaneously control the flow of pressure fluid to opposite sides of the double-acting piston. Furthermore, special apparatus including displacement sensors and feedback circuitry (not shown) are used to ensure that the phase of the movement of the baseplate is (within selected ranges) maintained in constant phase relation through

openings

204, 206 from high and low pressure hydraulic reservoirs, as is used on prior art vibrators. The closed hydraulic system of piston 212 could be pressured up by means such as pump 207, for example, to provide as tight a control of pistons 193,194 as desired. Also by change in diameter of piston 212 with respect to piston 201, a force multiplication on the

pistons

193, 194 can be achieved. Thus the system of FIG. 11 not only obviates the need for separate valves on each cylinder it guarantees the in-phase operation of all pistons. While only two pistons and cylinders are shown, any number can be connected in series in this way.

While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components. It is understood that the invention is not to be limited to the specific embodiment set forth herein, by way of exemplifying the invention,

2. The vibrator system as in claim 1 in which said mass means comprises a separate discrete volume of metal supported by said second frame.

3. The vibrator system as in claim 1 in which said 5 mass means comprises at lesat part of the mass of said vehicle.

4-. The vibrator system as in claim 3 including means to removably clamp said second frame means to said vehicle.

5. in an electrohydraulic vibrator system for generating seismic waves in the earth, said system including a transport vehicle, a baseplate, a vibrator system having a first of two relatively reciprocating parts fastened to a first frame fastened to said baseplate and the second of said two parts supporting a second frame, and means on said vehicle for pressing down on said baseplate through compliances with a force equal to at least portion of the weight of said vehicle, and means to selectively apply high pressure fluid to said vibrator system,

but the invention is to be limited only by the scope of the improvement comprising;

the attached claim or claims, including the full range of equivalency to which each element or step thereof is entitled.

What is claimed is:

1. In an electro-hydraulic vibrator system for generating seismic signals in the earth, said vibrator mounted on a vehicle and including baseplate a, and means to support said baseplate from said vehicle, said support means including means to lower said baseplate to the earths surface, and means including a compliant means for pressing down on said baseplate with a force equal to part of the weight of said vehicle, the improvement, comprising;

a. four cylinders and four pistons means slidably and sealably received therein, one in each of said cylinders, said cylinders spaced apart on said baseplate in the four corners of a rectangle; frame means b. first frame means attached to said pistons, and second frame means attached to said cylinders, either ofsaid first or said second frame means attached to 4 and supported by said base plate, the other of said first or second framemeans attached to a reaction mass positioned above said cylinders, the axes of said cylinders directed perpendicular to said baseplate;

c. reaction mass means supported by said second frame means; and

(1. means to selectively direct high pressure fluid to said cylinders, the first two cylinders on a first diagonal axis adapted to move their pistons upwardly on the application of pressure fluid, the second two cylinders on the second diagonal axis adapted to move their pistons downwardly on the application of pressure fluid, said pressure fluid applied sequentially to said first two cylinders and then to said second two cylinders;

whereby pairs of upward forces will be simultaneously applied to said base plate at the corners of said first diagonal axis and pairs of downward forces will be simultaneously applied at the corners of said second diagonal axis, sequentially, as said pressure fluid is applied sequentially to said first two and to said second two cylinders, said pairs of upward and downward forces all equal to each other and combining to form an oscillating vertical force applied to said baseplate at the center of said rectangle.

means to releasably rigidly clamp said second frame to said vehicle while said vibrator is operating and to unclamp said second frame from said vehicle when said vibrator is not operating, whereby said 25 second frame and said vehicle are forced to move in unison when said vibrator is operating and to move separately when said vibrator is not operating, whereby at least a portion of the mass of said vehicle acts as at least a part of the reaction mass for said vibrator system.

6. The vibrator system as in claim 5 in which said vibrator system includes a single cylinder and a single double-acting piston therein, said piston rigidly connected to said baseplate and said cylinder releasably 35 rigidly clamped to said vehicle.

7. The vibrator system as in claim 5 including a plurality of cylinders and including:

a. valve means associated with each of said plurality of cylinders to control the admission and expulsion of high pressure fluid to and from said cylinders; and

b. control means to control said valve means whereby the operation of said plurality of valves is simultaneous.

8. The vibrator system as in claim 7 in which said control means is hydraulic.

9. The vibrator system as in claim 7 in which said control means is mechanical.

10. The vibrator system as in claim 5 in which said clamp means comprises;

a. vertical post means attached to said second frame,

and

b. a plurality of opposed hydraulic rams attached to said vehicle in a horizontal plane directed inwardly radially to said post means to securely grasp said post and means to removably apply hydraulic pressure to said rams.

11. The vibrator system as in claim 5 in which said clamp means comprises:

c. clamp frame means attached to the truck frame;

d. a plurality of upwardly directed pistons in cylinders fastened to said clamp frame below, and a second plurality above said seat plate; and

e. means to apply high pressure liquid to said cylinders to press said pistons on said top and bottom seat plates; and

f. valve means to lock said pressure liquid in said cylinders.

12. The vibrator system as in claim in which said clamp means comprises:

a. vertical first post means attached to said second frame;

b. second post means attached to the truck frame on second post mounted on each side of said first post;

c. transverse openings coaxial through said three posts, said opening of a selected taper; and

d. tapered piston rod means of said selected taper operatively controlled be driven into said tapered opening.

13. The vibrator system as in claim 11 including two spaced seal rings between said pistons and their cylinders, and means to apply to the annular space between each piston and its cylinder, between said two seal 7 rings, a liquid pressure substantially equal to the pressure of said liquid in said cylinders.

14. In an electrohydraulic vibrator system for generating seismic waves in the earth, said system including a transport vehicle, a baseplate, and means on said vehicle for pressing down on said baseplate through compliances with a force equal to at least a portion of the weight of said vehicle, and including a vibrator system comprising a plurality of spaced-apart vibrator assemblies, each assembly comprising two elements relatively reciprocable with respect to each other, one element of each assembly connected to a first frame and the second element of each assembly connected to a second frame, one frame connected to said baseplate, the other frame connected to a reaction mass, the improvement comprising;

a. high pressure fluid means to operate said vibrator assemblies;

b. plurality of valve means, one associated with each of said vibrator assemblies for controlling the flow of pressure fluid to said vibrator assemblies and c. control means to drive all of said valve means in precise synchronism.

15. The vibrator system as in claim 14 in which said control means comprises mechanical means.

16. The vibrator system as in claim 1 in which said vehicle has a central longitudinal drive shaft and said cylinders and pistons are positioned two on each side of said drive shaft.

17 The vibrator system a sdn claiinfS in which said cylinders and pistons are positioned adjacent said base plate.

18. The vibrator system as in claim 1 including:

(a) valve means associated with each of said plurality of cylinders to control the admission and expulsion of high pressure fluid to and from said cylinders; and

(b) control means to control said valve means whereby the operation of said plurality of valves is simultaneous.

said control means comprises mechanical means.

20. The vibrator system as in claim 31 in which said control means comprises hydraulic means.

2 1 The vibrator system as in claim 13 in which said vibrator system comprises two cylinders, each including a double-acting piston therein.

22. The vibrator system as in claim 13 in which said vibrator system comprises four cylinders arranged in the corners of a rectangle. each cylinder containing a single-acting piston. two of the pistons adapted to move upwardly and two adapted to move downwardly with respect to said cylinders on the application of said pressure fluid.

23. The vibrator system as in claim 24 in which at least part of said reaction mass includes a part of the mass of said vehicle; and including means to releasably rigidly clamp said other frame to said vehicle.

24. The vibrator system as in claim 24 in which said control means comprises hydraulic means.

UNITED STATES PATENT OFFICE CETTFTCATE 0T QORECTTQN Patent No. V V mm D d February 5:}22

l v t r( Daniel Silverman It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

change 1'31" to --l8--, change "13" to --5--. change "13" to --'5----o change "24 to --l change "24" to "-14".

Claim 20 line Claim 21 line Claim 22 line Claim 23 line Claim 24 line Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents I FORM po'wso 9' uscoMM-Dc 60376-P69 I 1.5. GOVERNMENT PRINTING OFFICE: 1959 0-356-334,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PH Li -fit NO Dated F y 5 I Inventor(s) Daniel Silverman It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

change 1'31" to --l8--. change "13" to --5--. change "13" to --5--. change "2'4" to --l4--'. change 24" to --l Claim 20 line Claim 21 line Claim 22 line Claim 23 line Claim 2 line Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents I FORM 0 (10-69) USCOMM-DC 60376-P6S 1 a U.S. GOVERNMENT PRINTING OFFICE: I9" 0-366-33

Claims

1. In an electro-hydraulic vibrator system for generating seismic signals in the earth, said vibrator mounted on a vehicle and including baseplate a, and means to support said baseplate from said vehicle, said support means including means to lower said baseplate to the earths surface, and means including a compliant means for pressing down on said baseplate with a force equal to part of the weight of said vehicle, the improvement, comprising; a. four cylinders and four pistons means slidably and sealably received therein, one in each of said cylinders, said cylinders spaced apart on said baseplate in the four corners of a rectangle; b. first frame means attached to said pistons, and second frame means attached to said cylinders, either of said first or said second frame means attached to and supported by said base plate, the other of said first or second frame means attached to a reaction mass positioned above said cylinders, the axes of said cylinders directed perpendicular to said baseplate; c. reaction mass means supported by said second frame means; and d. means to selectively direct high pressure fluid to said cylinders, the first two cylinders on a first diagonal axis adapted to move their pistons upwardly on the application of pressure fluid, the second two cylinders on the second diagonal axis adapted to move their pistons downwardly on the application of pressure fluid, said pressure fluid applied seQuentially to said first two cylinders and then to said second two cylinders; whereby pairs of upward forces will be simultaneously applied to said base plate at the corners of said first diagonal axis and pairs of downward forces will be simultaneously applied at the corners of said second diagonal axis, sequentially, as said pressure fluid is applied sequentially to said first two and to said second two cylinders, said pairs of upward and downward forces all equal to each other and combining to form an oscillating vertical force applied to said baseplate at the center of said rectangle.

3. The vibrator system as in claim 1 in which said mass means comprises at lesat part of the mass of said vehicle.

4. The vibrator system as in claim 3 including means to removably clamp said second frame means to said vehicle.

5. In an electrohydraulic vibrator system for generating seismic waves in the earth, said system including a transport vehicle, a baseplate, a vibrator system having a first of two relatively reciprocating parts fastened to a first frame fastened to said baseplate and the second of said two parts supporting a second frame, and means on said vehicle for pressing down on said baseplate through compliances with a force equal to at least portion of the weight of said vehicle, and means to selectively apply high pressure fluid to said vibrator system, the improvement comprising; means to releasably rigidly clamp said second frame to said vehicle while said vibrator is operating and to unclamp said second frame from said vehicle when said vibrator is not operating, whereby said second frame and said vehicle are forced to move in unison when said vibrator is operating and to move separately when said vibrator is not operating, whereby at least a portion of the mass of said vehicle acts as at least a part of the reaction mass for said vibrator system.

6. The vibrator system as in claim 5 in which said vibrator system includes a single cylinder and a single double-acting piston therein, said piston rigidly connected to said baseplate and said cylinder releasably rigidly clamped to said vehicle.

7. The vibrator system as in claim 5 including a plurality of cylinders and including: a. valve means associated with each of said plurality of cylinders to control the admission and expulsion of high pressure fluid to and from said cylinders; and b. control means to control said valve means whereby the operation of said plurality of valves is simultaneous.

8. The vibrator system as in claim 7 in which said control means is hydraulic.

9. The vibrator system as in claim 7 in which said control means is mechanical.

10. The vibrator system as in claim 5 in which said clamp means comprises; a. vertical post means attached to said second frame, and b. a plurality of opposed hydraulic rams attached to said vehicle in a horizontal plane directed inwardly radially to said post means to securely grasp said post and means to removably apply hydraulic pressure to said rams.

11. The vibrator system as in claim 5 in which said clamp means comprises: a. spherical ball means supported by said second frame; b. spherical seat plates above and below said ball means; c. clamp frame means attached to the truck frame; d. a plurality of upwardly directed pistons in cylinders fastened to said clamp frame below, and a second plurality above said seat plate; and e. means to apply high pressure liquid to said cylinders to press said pistons on said top and bottom seat plates; and f. valve means to lock said pressure liquid in said cylinders.

12. The vibrator system as in claim 5 in which said clamp means comprises: a. vertical first post means attached to said second frame; b. second post means attached to the truck frame on second post mounted on each side of said first pOst; c. transverse openings coaxial through said three posts, said opening of a selected taper; and d. tapered piston rod means of said selected taper operatively controlled be driven into said tapered opening.

13. The vibrator system as in claim 11 including two spaced seal rings between said pistons and their cylinders, and means to apply to the annular space between each piston and its cylinder, between said two seal rings, a liquid pressure substantially equal to the pressure of said liquid in said cylinders.

14. In an electrohydraulic vibrator system for generating seismic waves in the earth, said system including a transport vehicle, a baseplate, and means on said vehicle for pressing down on said baseplate through compliances with a force equal to at least a portion of the weight of said vehicle, and including a vibrator system comprising a plurality of spaced-apart vibrator assemblies, each assembly comprising two elements relatively reciprocable with respect to each other, one element of each assembly connected to a first frame and the second element of each assembly connected to a second frame, one frame connected to said baseplate, the other frame connected to a reaction mass, the improvement comprising; a. high pressure fluid means to operate said vibrator assemblies; b. plurality of valve means, one associated with each of said vibrator assemblies for controlling the flow of pressure fluid to said vibrator assemblies ; and c. control means to drive all of said valve means in precise synchronism.

17. The vibrator system as in claim 16 in which said cylinders and pistons are positioned adjacent said base plate.

18. The vibrator system as in claim 1 including: a. valve means associated with each of said plurality of cylinders to control the admission and expulsion of high pressure fluid to and from said cylinders; and b. control means to control said valve means whereby the operation of said plurality of valves is simultaneous.

19. The vibrator system as in claim 18 in which said control means comprises mechanical means.

20. The vibrator system as in claim 18 in which said control means comprises hydraulic means.

21. The vibrator system as in claim 5 in which said vibrator system comprises two cylinders, each including a double-acting piston therein.

22. The vibrator system as in claim 5 in which said vibrator system comprises four cylinders arranged in the corners of a rectangle, each cylinder containing a single-acting piston, two of the pistons adapted to move upwardly and two adapted to move downwardly with respect to said cylinders on the application of said pressure fluid.

23. The vibrator system as in claim 14 in which at least part of said reaction mass includes a part of the mass of said vehicle; and including means to releasably rigidly clamp said other frame to said vehicle.

24. The vibrator system as in claim 14 in which said control means comprises hydraulic means.