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Патент USA US2581066

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Jan- 1, 1952
Filed March 16, 1950
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(Jam/‘en CZ. Glaxandar
Patented Jan. 1, 19,52
_ 2,581,063
UNITED smrss PATENT omcr
Warren A. Alexander, Tulsa, Okla., assignor to
Standard Oil Development Company, a corpo
ration of Delaware
Application March 16, 1950, Serial No. 150,097
3 Claims.
(01. 177-352)
This invention relates to a novel type of geo
invention further details of this element of the
phone or seismic pickup to be used for the de
apparatus will not be set forth. This material
tection of seismic energy, and the conversion
may be understood by referring, to "Reviews of
of this energy to electrical energy. The geo
Modern Physics” for July 1948, vol. 20, page 457,
phone of this invention simply consists of a 5 et seq. It is to be understood then that element
metallic plate variably spaced from a perma
2 in the drawing is a permanentlyelectrl?ed
nently electri?ed substance. The construction
material characterized by the maintenance of
is such that seismic energy acting on the geo
opposite electrical charges on the two faces of
phone varies the position of the metallic plate
it. For example the electret may be positioned
with regard to the permanently electri?ed ma 10 so that the upper surface of it exhibits a positive
terial so as to develop a varying charge on the
charge. It is apparent then that if a metallic
plate. The electrical signal developed by the
body is brought in proximity to the electret a
plate may then be ampli?ed and recorded as
charge will be induced in this body. Thus, by
In many applications, particularly in the
search for oil by seismographic methods, delicate
instruments are required capable of transform
ing mechanical vibrations, or motions into elec
trical energy. These instruments are generally
positioning a metallic plate, or other conductive
material 3, parallel to and adjacent to the elec
tret, the distance of this plate from the electret
may be indicated by the charge on the plate.
Again by varying the distance of the plate from
the electret, the frequency of displacement vari-v
called geophones or seismic pickups. It is the 20 ation may be determined from the frequency
particular object of this invention to provide
with which the charge of the plate varies. To
an instrument of this character having advan
wards this end the plate 3 may be supported by
tages as regards simplicity of construction, mam
springs 4 and 5 so as to maintain the plate above
tenance and use.
the electret in a vertically variable manner. It
In accordance with this invention a geophone 25 is apparent then that upon receipt of seismic
is constructed essentially containing two ele
energy coming upwardly through the earth,
me ts. First a permanently electri?ed-material
movement of the housing I will cause the plate
whic "has been called an “e1ectret" is positioned
3 to vibrate so as to vary its position from the
in the geophone. Adjacent the electret, on a
electret. The result of this will be that an
spring mounting, is a plate composed of elec 30 alternating current will be generated by the
trically conductive material, preferably metal
plate, having a frequency of the seismic energy
lic. The nature of the electret is such that as
and having an intensity proportional to the in
the proximity of the plate from the electret
tensity of the seismic energy. Consequently, by
varies, the charge induced on the plate will also
coupling the plate 3 and housing I to an am
vary. Since the plate will vary in distance from 35 plifying and recording system, the desired in
the electret at a frequency about that of seismic
formation as to the seismic energy may be
energy affecting the geophone, an alternating
obtained. As illustrated, in the ‘drawing, a cou
' current will be developed in the plate which may
pling unit 6 may be employed which is preferably
be ampli?ed and recorded by conventional meth
positioned in the housing I as an integral part
‘ ods. It may, therefore, be appreciated that the 40 of the geophone apparatus. One lead 1, leads
geophone of this invention is an extremely simple
from the plate 3 to the coupling unit while a
and uncomplicated type of apparatus.
second lead 8 is connected to ‘the housing I and‘
Referring to Figure 1 of the drawing a. geo
to the coupling unit. Leads 1 and 8 may lead
phone is diagrammatically illustrated embodying
to the input of a cathode follower matching
‘ the principles of this invention. The particular 45 unit, or they may lead to an electronic ampli?er,
geophone illustrated is of the type identi?ed as an
or any other desired type of electrical coupling
area geophone particularly adapted for position
apparatus. It is preferred, however, that the
ing on the surface of the ground for the receipt
signal developed across leads 1 and 8 be sub
of seismic energy traveling upwardly to the sur
jected to some ampli?cation prior to transmis
face. As indicated, the geophone consists of 50 sion through conductors 9 and I0 extending from
an external housing I, containing the electret
the geophone housing. The signals developed
element 2. The electret may be made of any
' by leads 9 and I0 may then be recorded in the
desired materials capable of maintaining a per
conventional fashion.
manent electri?cation. As the nature and con
A particularly desirable type of structure is
struction of the electret, is not a part of this
illustrated in Fig. 2. The surface of the electret
2 is spherical concave while the surface of the '
plate 3 is spherical convex. Springs l2 elas
tically supportthe plate 3 above the electret 2
vertical seismic impulses than to horizontal seis
mic impulses comprising a housing, an electret
element supported horizontally within said hous- -
so that the curved surfaces are positioned in
non-touching, substantially parallel concentric
relation. This type of structure discriminates
against horizontal waves but responds to vertical
waves. It is to be noted that the plate area is
ing, said electret element having an upper curved
5 ‘surface of essentially spherical concave shape,
an electrically conductive body having a lower
surface of essentially spherical convex shape
generally to the shape of the upper
preferably smaller than the concave area of
the electret, thus permitting the plate to move 10 surface of said electret element, spring means
fastened to said housing and elastically sup
horizontally without any overlapping of \the'elec
porting said electrically conductive body‘ above
It is desired that the natural‘ period of the
said electret element in a manner positioning
said curved surfaces in non-touching. substanplate mass and spring elasticity be greater than
tially parallel concentric relation, and'mean's
that of the seismic signals to be recorded.
15 electrically connected to said electret element
What is claimed is:
and to said conductive body whereby the elec
1. A geophone havinggreater sensitivity to
trical charge induced in said conductive body
vertical seismic impulses than to horizontal seis
can be measured as a function of the vibrating
mic impulses comprising a permanently electri
motion of said conductive body relative to said
?ed body having a curved surface, an electrically
conductive body having a curved surface, cor
responding in general shape to said ?rst curved
surface, one of- said surfaces being essentially
spherical concave and- the other of said surfaces
electret element.
being essentially spherical convex, and spring 25 The following references are of record in the
?le of this patent:
means elastically supporting one of said bodies
above the other body in a manner positioning
I _
said curved surfaces in non-touching, substan
tially parallel concentric relation.
Rutherford ______ __ Dec. 17, 1935
2. Geophone as de?ned by claim 1 wherein the 30 2,257,187
Owen __________ __ Sept. 30, 1941
surface area of one of said surfaces is less than
that of the other surface.
'3. A geophone having greater sensitivity to
Ritzmann ______ ___ Feb. 10, 1942
Truman ________ __ Apr. 20, 1943
Ellsworth ________ _'_ Jan. 25, 1944
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