Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2003-04-11
2004-10-19
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S602100, C029S609000, C029S609100, C340S854400, C340S855600, C310S036000, C367S082000, C073S152030, C073S152470
Reexamination Certificate
active
06804875
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an elastic wave generator, magnetostriction oscillator mounting structure and method.
An elastic wave generator is a device for generating an acoustic longitudinal elastic wave and expected to be utilized in the following variety of fields:
(1) a transmitter of an acoustic transmission apparatus utilizing a drilling pipe as an acoustic signal transmitting medium;
(2) a transmitter of an acoustic transmission apparatus utilizing a metal structural body or a rigid structural body as an acoustic signal transmitting medium;
(3) an apparatus for injecting or internally generating a longitudinal elastic wave into a concrete or metallic structural body for inspecting characteristics, property changes, flaws or the like of the structural body;
(4) an apparatus for injecting or internally generating a longitudinal elastic wave into a concrete or metallic structural body for structural analysis of a building or a mechanical structural body;
(5) a seismic wave generating apparatus for evaluating stratum or the like;
(6) an acoustic speed measuring apparatus for measuring characteristics of strata or the like; and
(7) other apparatus for non-destruction inspection, measurement, survey, information transmission or the like in which a relatively large vibration is effective.
Heretofore, the method for applying a stress to a mechanical structure includes a hydraulic press generating a static compression stress, an expansion test machine generating a static tensile force or a hammer or a falling object generating a dynamic stress. In the method using the hammer or the falling object, it is difficult to control the stress at will so that the detailed examination of the workpiece cannot be carried out.
On the other hand, a method for converting strain into stress as a method for freely controlling the stress is used in acoustic measurement of a relatively small structure having a relatively small thickness or uniform composition. However, since this method is not suitable for use in terms of a large structure or a sparse material which needs large stress, the measurement of these materials had to be achieved by generating a large stress with a hammer or a falling substance.
Therefore, in order to generate a controlled large stress, an attention has been paid to materials that have extremely high strain characteristics and a strain-stress conversion apparatus utilizing these materials (piezoelectric material, supermagnetostriction material) has been studied. However, these materials, such as brittle and weak sintered alloys or easily bendable and deformable materials, have compression strengths that are too small not to self-destruct upon the generation of the strain in the stressed state.
While it has been known that the generated stress can be made large when the strain is generated by energizing the piezoelectric material or the magnetostriction material put under the pre-stressed state, the compression strength of the material was too small and the material was self-destroyed when a strain is generated even with a small pre-stress. Therefore, it was not possible to obtain at will a large stress, such as a stress of 10-30 kgf/mm
2
, in order to generate a strong elastic wave (acoustic signal), so that this material was not suitable to apply to a large structural body or a sparse material.
Therefore, while a strain-stress conversion device employing these materials (piezoelectric material, super magnetostriction material) having high strain characteristics have been used in the acoustic measurement of a relatively thin matter or a structural body of a homogeneous composition, the measurement with the hammer or the falling object has conventionally been used for a large structural body or the materials of sparse composition. Although the realization of the acoustic transmission through the use of the drilling pipes for oil rigs of a length of from several hundred meters to several thousand meters have been believed, since there has been provided no realistic acoustic longitudinal elastic wave generator that can provide a large stress wave, the pressure wave transmission or mud pulse system in which drilling mud is used as the transmission medium, has been employed.
According to the study and the analysis of the inventors of the present invention, the unsolved technical problems in these conventional fields of application are given below:
(1) generation and injection of a stress wave at will in a large metallic structural body;
(2) injection of a stress wave at will into a structural body having a composition of an internal disturbance reflection such as concrete, rock or plastic; and
(3) generation and injection of an acoustic longitudinal wave of from several Hz to several ten kHz at and into a structural body.
Then, the present invention is expected to be utilized in a wide variety of fields as discussed previously, so that both the present invention and the conventional technique will be described in terms of examples in which they are applied to the field of oil rigs.
For example, Japanese Patent Laid-Open No. 8-130511 discloses the system in which the information of the bottom of the well being dug in an oil well is transmitted by an elastic wave (acoustic) signal using the drill pipes as a transmission medium.
FIGS. 23
to
25
b
are views showing the system disclosed in Japanese Patent Laid-Open No. 8-130511 and
FIG. 23
being a view showing the overall construction of the oil well facility,
FIG. 24
being a fragmental sectional view showing the drill collar portion at the well bottom of the drill pipe,
FIG. 25
a
being a plan view and
FIG. 25
b
being a sectional side view.
In
FIGS. 23-25
b,
100
shows a tower for drilling an oil well.
24
is a drill pipe inserted into the ground from the tower
100
and having straight cylindrical pipes each having a length of about 8 meters, connected to constitute an assembly of a length of several hundred meters to several thousand meters, the drill pipe being driven to rotate by an unillustrated drive unit mounted to the well tower
100
. Disposed within the drill collar
22
of the drill pipe
24
at the bottom portion of the well is a magnetostriction oscillator
34
.
25
is a sensor for detecting various information necessary for digging, the various information signals from the sensor
25
at the well bottom are converted into digital signals so that an electric current varying in accordance with the converted digital information signal is supplied to an excitation coil
36
of the magnetostriction oscillator
34
, which converts the signal into an elastic wave (acoustic signal) to be transmitted through the drill pipe
24
to the ground surface.
26
is a receiver installed in the portion of the tower
100
of the drill pipe
24
,
27
is a signal processing apparatus for processing to demodulate the received signal of the receiver
26
to monitor the state of the bottom of the well, such as the temperature of the well, the tilt of the drill tip or the like.
The mounting of the magnetostriction oscillator
34
to the drill collar
22
is achieved by the cantilevered mounting as shown in the sectional side view of
FIGS. 25
a
and
25
b
in which a clamping screws
39
and rock nuts
40
are used to make a canti-lever attachment (canti-levered system), so that when the magnetostriction oscillator
34
is elongated by energization, the reaction force from the inertia weight
42
disposed at the free end side is transmitted to the drill collar
22
through the horn
38
to become an elastic wave. Therefore, the injection efficiency of the elastic wave (acoustic) energy from the magnetostriction oscillator
34
to the drill pipe on the order of 0.01 to 0.1, so that, when the drill pipe
24
of several hundred meters to several thousand meters long is used as a transmission medium in actuality, the elastic wave (acoustic wave) does not reach the receiver
26
at the ground level and this system is not practically used in oil well drilling, but the pressure wave transmission or mud pulse
Hattori Shinichi
Matsuhashi Kanji
Sakamoto Takahiro
Shimada Takashi
Taniguchi Ryosuke
Arbes Carl J.
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
Phan Tim
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