Acoustics – Geophysical or subsurface exploration – Seismic wave generation
Patent
1981-04-08
1983-09-27
Wilbur, Maynard R.
Acoustics
Geophysical or subsurface exploration
Seismic wave generation
367189, G01V 1047, G01V 1133
Patent
active
044063458
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to transducers for inducing vibrational signals in an elastic medium, and more particularly, but not by way of limitation, it relates to an improved construction for a baseplate and housing assembly for a transducer especially suitable for generating relatively high frequency seismic waves in the earth.
2. Description of the Prior Art
A conventional seismic transducer of the prior art is illustrated in U.S. Pat. No. 3,745,885 to Fair et al., assigned to the assignee of the present invention. The Fair et al. device includes a baseplate, a reaction mass, and a double-rod-end piston disposed in a cylindrical bore of the reaction mass. The lower rod end is attached to the baseplate and the upper rod end is attached to an upper frame member that is also connected to the baseplate. Seismic transducers such as that shown in the apparatus of Fair et al. are generally designed for operation within the range of about 2-80 cycles per second. The present invention provides a housing and baseplate structure suitable for operation in a relatively higher frequency range, up to and exceeding approximately 250 cycles per second.
SUMMARY OF THE INVENTION
In a seismic transducer designed for relatively high frequency operation, there are two primary design parameters which must be optimized. First, it is necessary that the baseplate and housing structure be as lightweight as possible. Second, the baseplate and housing structure must also be kept as rigid as possible so that the dynamic force transmitted into the earth will be in phase over the entire baseplate contact area. The structure connecting the upper end of the piston shaft assembly to the baseplate must be of sufficient rigidity that forces transmitted from the upper end of the shaft remain in phase with forces transmitted into the baseplate from the lower end of the shaft.
The present invention achieves such a lightweight rigid housing and baseplate structure by providing a frame or housing made up of three sections. The first section includes a relatively small diameter flat plate bolted to the upper end of the piston shaft. The outer periphery of the flat plate is rigidly attached to the second housing section which comprises a frusto-conical section having a side angle of approximately 45.degree. to the axis of the frusto-conical section. The lower end of the frusto-conical section is in turn rigidly attached to a cylindrical barrel section, the bottom end of which is rigidly attached to the baseplate. The baseplate includes a central hub to which the lower end of the piston shaft is rigidly connected. Upper and lower parallel skin plates extend radially outward from the upper and lower ends of the central hub and a plurality of stiffener plates extend radially outward from the central hub to provide a rigid baseplate assembly which will maintain in-phase force transmittal and holddown force distribution across the baseplate.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view with parts in section of the seismic transducer of the present invention.
FIG. 2 is a bottom view of the baseplate of the present invention showing the bottom skin plate partially cut away so that the stiffener plates may be easily viewed.
FIG. 3 is an inverted sectional elevation view of the baseplate assembly of FIG. 2 taken along line 3--3.
FIG. 4 is an inverted elevational sectional view of the baseplate of FIG. 2 taken along line 4--4 specifically showing the manner in which the stiffener plates and the upper and lower skin plates are assembled.
FIG. 5 illustrates a bottom view of another form of baseplate for use in the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings and particularly to FIG. 1, the seismic transducer apparatus of the present invention includes a baseplate 12 having a hydraulically powered vibrator assembly 14 mounted thereon.
The seismic transducer is generally attached to a vehicle 15, such as a
REFERENCES:
patent: 2910134 (1959-10-01), Crawford et al.
patent: 3159233 (1964-12-01), Clynch et al.
patent: 3557900 (1971-01-01), Kilmer
patent: 3983857 (1976-10-01), Silverman
patent: 4116299 (1978-09-01), Martin
patent: 4206896 (1980-06-01), Cadillac et al.
Conoco Inc.
Kaiser K. R.
Miller William J.
Wilbur Maynard R.
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