US3029733A

US3029733A - Method and means for causing seism

Info

Publication number: US3029733A
Application number: US761882A
Authority: US
Inventors: Roy W Mcelroy
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-09-18
Filing date: 1958-09-18
Publication date: 1962-04-17
Anticipated expiration: 1979-04-17

Description

April 17, 1962 R. w. MCELROY METHOD AND MEANS FOR CAUSING SEISM Filed Sept. 18. 1958 'INVENTOR. R O Y W. M E L ROY ATTORNEY Filed Sept. 18, 1958, Ser. No. 761,882

1 Claim. ((31.102-42) invention pertains to exploration of geological formations by seismic reflection etc.; and more particu- .larly to the production of seism.

, widely used ethod of geological exploration includes the production of a-seismic wave which bounces or echoes from a particular sub-surface formation. These echoes are recorded by seismographs and by the interpretation of the seismograms so produced; an indication may be had of the underground formation. Customarily, the

seismic wave is produced by drilling a hole about a hundred feet below the surface of the earth and detonating an 7 explosive charge within theearth.

L have invented a method ,of producing seism which makes it unnecessary to drill a hole within the earth. Basically, it.5comprises a bottom plate which rests upon the earth and a heavier weight which sets upon-the bottom plate. An explosive charge is located between these two'members. When the charge is detonated, an impact of large'magnitude is caused upon the bottom plate forcing the earth downward, compressing it, because of the heavier upper weight.

An object of this invention is to produce seism.

Another object of this invention is to produce a single seismic wave so that seismograms may be easily interpreted.

A further object of this invention is to achieve the above witha device which is safe to operate, easy to use, and light in weight so that it is easily portable.

- Still further objects are to achieve the above with a device that is sturdy, compact, simple, and reliable, yet inexpensive and easy to manufacture.

The specific nature of the invention as well as other objects, uses, and advantages thereof will clearly appear from the following description and from the accompanying drawing, in which:

FIGURE 1 is a sectional view of a device according to this invention.

FIGURE 2 is a plan View of the device shown in FIG- URE 1.

As may be seen in the accompanying drawings, one embodiment of this invention uses a device having cup shaped bottom 10. This bottom member 10 has plane surfaced bottom 12 which is adapted to be set solidly upon the earth. Along the exterior of the sides of the cup shaped member are handles 14 for dragging the device along the ground. 7

The inside of the cup shaped member 10 has an axial cylindrical bore 16. The upper inner lip is beveled at 18 for purposes which will be described later. Concentric with the bottom is boss 20 which has rod 22 threaded into it, so that the rod 22 extends upwardly co-axial with the bottom portion. An annular concavityt24 is cut Within the bottom member around the boss 20. This concavity is filled with an explosive charge 26 when the device is m use.

By means of a radial bore through the bottom member detonator 28 is introduced. It is contemplated that an electrical detonator would be used and the explosive charge be detonated with the aid of battery 30 and switch 32. As explosive charges and detonators (either electrical, mechanical, or otherwise) are well known to the art, they have not been described in detail here. The choice of the particular type of explosive to be used, the amount of the explosive charge, and the type of detonator are all well within the skill of the one ordinarily skilled in the art.

' shaped bottom member.

I upon the boss.

[-2 Upper member 34 is, partially seated within the cup The upper member 34 is generally cylindrical in shape and has a reasonably snug fit with the lower member 16. The upper. member has.

an bore in which the rod 22 is located. Also the upper memberhas an axial depression which mates with boss 20. The depth of this depression is less-than the height-of the boss, therefore the upper member rests bottom of the upper member and the upper portionvof the bottom. of the cup-shaped member. When the upper member. is in the lower position 'as illustrated, it does not rest upon the explosive charge .or any bits of the explosive charge which might be spread around. The upper member also has-handles '36 by which it may be moved;

Spring catches 38 are attached to the top of the upper member. These catches are means .for retaining the upper member in a separated position after the, upper and lower members have been blown apart by the explosive charge. They are firmly attached to the upper member by any convenient means such as welding or bolting.

' They have catch 44 at the top which is'supported by leaf spring 42. which extends parallel to the axis of the device.

Loop 44 is on the extreme upper portion of the rod 22 so that a hook may be engaged therein to lift the device by power mechanism. Immediately below this loop, the rod is of greater diameter than the lower portion of the rod. This portion of greater diameter is threaded so that a stop 46 may be adjustably attached thereto. The stop 46 is a disk shaped member. The diameter of the disk is slightly greater than the distance between the catches 44) when the leaf springs 42 are in the relaxed position. Therefore as the upper member moves up, the upper'surface of the catches dllwill act as cams and spread the catches apart as they move over to stop 46. However, as the upper member attempts to move downward, the lower edges of the catches will stopon the disk 46 and retain the upper member in a separated position from the lower member.

The remote ends of the catches 40 are in the form of handles 48. If it is desired to separate the upper and lower members other than by the explosive charge, the handles may be used for this purpose, preferably in conjunction with power equipment. Alternately, the disk stop 46 may be screwed down to its lowest position and the catches 40 snapped over it in this position. Then by rotating the disc along with the upper member, the upper and bottom member can be separated.

Helical compression spring 50 encircles the rod '22 and normally rests upon the top of the upper member, and extends to bottom of the stop. When the explosive charge separates the upper and lower members, the spring will 'of the explosive charge detonating while the second sound wave would be produced when the upper member dropped back upon the lower member.

It is necessary that the upper member have greater mass than the bottom member. Otherwise, the device would act as a launching for a projectile and the greater amount of energy would be expended in sending the upper member up. However, by making the upper member of greater mass, the greater amount of energy is expended in forcing the lower. member down which gives a greater impact and seism.

There is a definite clearance between the,

The lower edge of the upper member is beveled at 52. The gases resulting from the explosion of the charge will escape in an upward manner when the

bevels

18 and 52 become aligned. If it were not for these 'bevels, most of the gases would be dissipated in an horizontal direction. Rather good confinement of the explosion is obtained even though the top member does not fit tightly within the cup shaped member nor around the sectional rod 22. There is not a straight line escape route for the gases. The gases from the explosive charge 46 must turn a corner along any route in order to escape.

With this device, a simple mechanism has been provided for producing seism. It is relatively lightweight and easily transported by a small truck. Indeed it may be transported by helicopter or blimp to extremely remote areas in rough terrain making possible geophysical exploration where otherwise it would not be economically feasible to use ground vehicles.

It will be apparent that the embodiment shown is on the exemplary and that various modifications can be madein construction, materials, and arrangement within the scope of the invention as defined in the appended claim.

I claim as my invention:

A means for causing seism: a rigid cup shaped bottom member, a rigid upper member seated partially within said bottom member, said upper member having a greater mass than said bottom member, an explosive charge within said bottom member between the two members, means for detonating the explosive charge, guide means attached to the lower member for guiding the upper member, said means for guiding including a rod extending from about the axis of the cup shaped bottom member, the upper member having a hole through which the rod extends, a stop on the rod for limiting the movement of the upper member, the stop being a disc shaped element threaded onto the rod, a helical compression spring surrounding the rod between the bottom member and the stop, and catch means attached to the upper member in operative relationship to the stop for retaining the upper member in a separated position; so that when the bottom mem-' her is placed solidly upon the earthand the charge detonated a seismic wave is produced within the earth resulting from only one impact.

References Cited in the file of this patent UNITED STATES PATENTS