US 4,364,446 A · Generating pulses

Abstract

Methods and devices are disclosed for generating acoustic pulses in a water or land medium, e.g., for use in seismic investigations. The pulse amplitudes, waveshapes, and frequencies can be controlled by signals that may originate at a remote location. Compressed gas is confined at high pressure in a valve chamber (12, 194). An initiating signal causes the opening of a passage (54, 56, 192) from the chamber into the medium to initiate the rise of a pressure pulse therein. A second signal causes the closing of the passage in a manner such that the initial rise of the pressure pulse is limited by the closure of the passage. In one device, the passage is opened by one sleeve valve member (60) and closed by another sleeve valve member (58). In another device the passage is opened by a sleeve valve member (196) whose motion to open the passage is arrested substantially instantaneously by transferring its momentum to a momentum exchange sleeve (246) that is then gradually decelerated. The passage may be closed by the same sleeve valve member (196) whose motion to close the passage is arrested substantially instantaneously by transferring its momentum to a second momentum exchange sleeve (220) that is then gradually decelerated.

Claims12

Dependent claims

The method of generating an acoustic pulse in a water or land medium utilizing a sleeve valve member that is axially movable between a base position closing the passage and a displaced position clearing the passage comprising the steps of

confining compressed gas at high pressure in a valve chamber within the medium by holding the sleeve member in the base position,
generating an initiating signal,
responding to the signal by sleeve valve member towards the displaced position to open the passage for the compressed gas from the chamber into the medium so as to initiate the rise of a pressure pulse therein,
generating externally of the valve chamber a second signal during the initial rise of the pressure pulse,
responding to the second signal by closing the passage in a manner such that the initial rise of the pressure pulse is limited by the closure of the passage arresting the motion of the sleeve valve member at the displaced postion by substantially instantaneously transferring most of its momentum to a momentum exchange sleeve, and gradually decelerating the momentum exchange sleeve.

2 more elements

A compressed gas discharge device adapted for generating acoustic pulses, comprising

a valve body encompassing a generally cylindrical valve chamber for containing compressed gas and having port means adapted to provided a passage from the valve chamber into a region surrounding the valve body,
a first and a second sleeve valve member each enclosing a portion of the valve chamber and each being axially movable between a respective base position and a respective displaced position, the valve members being adapted to clear the passage when one member is in its base position and the other is in its displaced position, the valve members also being adapted to close and seal the passage when both members are engaged and occupy their displaced positions and when both engaged members are in transit from their displaced positions to their base positions, and
signal responsive means for initiating movement of each sleeve valve member individually from its respective base position to its respective displaced position, thereby to control both the commencement and the time duration of a flow of gas from the valve chamber through the passage.

Dependencies are inferred from the claim text.

Generating pulses

Life of this patent

Generating pulses

Life of this patent

Abstract

Claims12