Note: Descriptions are shown in the official language in which they were submitted.
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This is a division of Application Serial No. 472,860.
This application relates to tamping and topping plugs
for bore holes.
BACRGROUND OF THE I~VENTI0~7
In carrying out a seismic exploration, a standard
procedure is to drlll holes into the geologic formations of
interest and to plant explosive charges in the bore holes. The
charges are then detonated and appropriate measurements recorded
to enable evaluation of the formation.
There are a number of problems associated with this
seismic drilling. One of these occurs during the actual blast.
Unless the hole is properly plugged prior to detonation, a large
proportion of the energy of the blast escapes upwardly through
the hole and is thus not properly directed through formation of
interest.
There is therefore a continuing need for a bore hole
plug which is simple and inexpensive in construction yet
sufficiently durable to remain in place for extended periods and
to withstand the force of the blast. To date, a variety of plugs
have been proposed and used, but these do not satisfactorily meet
all of the criteria set out above.
In addition, plugs are required to be inserted into
bore holes to support concrete, earth or other topping materials
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used to close the hole. Accordingly, a simple plug which could
withstand the force of the blast and remain in the hole as a
topping plug would be highly desirable. Such a plug could be
used as a topping plug only if required.
The bore hole plug of the present invention is intended
to alleviate the problems discussed.
PRIOR ART
Various types of tamping and topping plugs are known in
the art, but none of these offer the advantages of the present
invention.
Canadian Patent 827,427, issued November 18, 1969, to
Ace Explosives Ltd. provides a drive point for explosive charges
having some similarity in structure but used for a completely
unrelated purpose.
Canadian Patent 920,508, issued February 5, 1973, to
Ovelson, illustrates one form of topping plug for use subsequent
to drilling and shooting of a seismic test hole. The device
utilizes a flanged annular rim at right angles to a body section
which rim has the facility of limited diametrical size
adjustment.
Canadian Patent 1,010,780, issued May 24, 1977, to
Markicevic, provides another form of plug device for marking and
plugging bore holes at the surface. The device is not intended
to confine the blast to the hole.
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Canadian Patent 1,048,405, issued February 13, 1979, to
Bassani, provides a further form of hole plugging device for use
in plugging holes following blasting.
United States Patent 2,822,876, issued February 11,
1958, to Murrow, et al., illustrates a form of bridging plug for
use in plugging a bore hole or isolating a lower section of a
well.
United States Patent 3,264,992, issued August 9, 1966,
to Beck, illustrates a tamping plug comprising two parts which
work together to plug a bore hole during blast in the hole.
Finally, Canadian Application Serial No. 462,827 filed
September 10, 1984, by Jim Jackson, one of the inventors in the
present case, illustrates a different form of tamping and topping
plug for use in bore holes.
SUMMARY OF THE INVENTION
A simple molded plastic device has now been developed
which is light, economical, of one piece ccnstruction; and which
is very effective in tamping and plugging bore holes to confine
the force of the blast to the hole.
The invention thus provides a plug for endwise
insertion into a drill hole, the plug including an elongated
central body and at least two arrays of ourtwardly extending
means being integrally formed with the central body and having
outer extremities for engaging the surrounding wall of the drill
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hole, the juncture of the outwardly extending means of one array
being at a longitudinal distance along the central body from the
juncture of the outwardly extending means of the other array, the
means forming the arrays ~eing flexible inwardly from an unflexed
condition wherein the outer extremities of the means in each
array are disposed about a longitudinal axis of the plug on a
peripheral line of greater diameter than the drill hole, the
peripheral lines of the two arrays having a substantial space
therebetween in the longitudinal direction of the plug.
In a preferred embodiment the body member is
cylindrical and the elongated members extend from the front and
rear ends of the body member.
There is further provided a process for enhancing the
information obtainable from seismic blasting comprising inserting
endwise into a seismic bore hole in which an explosive charge has
been placed, and above the said charge, a tamping plug including
an elongated central body and at least two arrays of ourtwardly
extending means being integrally formed with the central body and
having outer extremities for engaging the surrounding wall of the
drill hole, the juncture of the outwardly extending means of one
array being at a longitudinal distance along the central body
from the juncture of the outwardly extending means of the other
array, the means forming the arrays being flexible inwardly from
an unflexed condition wherein the outer extremities of the means
in each array are disposed about a longitudinal axis of the plug
on a peripheral line of greater diameter than the drill hole, the
peripheral lines of the two arrays having a substantial space
therebetween in the longitudinal direction of the plug; then
exploding the charge and taking seismic readings.
BRIEF D~SCRIPTION OF THE DRAWINGS
In drawings which illustrate embodiments of the
invention,
FIGURE l is a perspective view of a plug according to
the invention;
FIGURE 2 is a front plan view of a plug according to
the inventiOn;
FIGURE 3 is a side elevation of a plug according to the
invention;
FIGURE 4 is a rear plan view of a plug according to the
invention;
FIGURE 5 illustrates a plug according to the invention
located in a bore hole prior to a blast;
FIGURE 6 illustrates the embodiment of FIGURE 5 after
the blast.
While the invention will be described in conjunction
20 with illustrated embodiments, it will be understood that it is
not intended to limit the invention to such embodiments. On the
contrary, it is intended to cover all alternatives, modifications
and equivalents as may be included within the spirit and scope of
the invention as defined by the appended claims.
DETAILED DESCRIPTION OF TH~ PREF~RRED EMBODIMENTS
In the following description, similar features in the
drawings have been given similar reference numerals.
The plug 10 includes a body section 12 of cylindrical
5 configuration. The plug is preferably formed of a resilient
material such as elastomer or a plastic. The forward end 14 of
the body section 12 terminates in the illustrated embodiment in a
truncated conical end section 16.
The end section 16 may be profiled in a number of
10 different configurations other than conical. For exapmle,
hemispherical, pyramidal or flat end sections 16 would also
serve. It is basically only required that the plug 10 be
substantially closed, so as not to allow the passage of the blast
or of part of the blast beyond the plug.
The most preferred embodiment of end section 16,
however, is the illustrated truncated cone.
A series of elongated members or claws 18 and 20
protrude outwardly and rearwardly from the front 14 and rear 22
of the body section 12. These members are integral with the body
section 12.
While various configurations of the individual members
18 and 20 would be acceptable, it is preferred that the width and
thickness both decrease from the base 24 to the outer extremity
26 of the said members. As illustrated, the forward members 18
25 are molded to smoothly taper to an edge 28; while the rearward
members 20 are somewhat thicker and are bevelled at 30 toward the
ends 32.
The front and rear claws 18 and 20 are as a group
preferably arranged in a symmetrical fashion about the plug body
12. The plug 10 thereby has good directional stability in the
bore hole and is prevented from becoming misaligned on insertion
or with the force of the blast. In the prefered configuration
the plug includes two forward claws 18 and four rear claws 20.
A pair of flange sections 34 and 36 extend around a
major part of the rear end 38 of the body section 12. These
flange sections leave spaces 40 and 42 behind the forward claws
18. The flange sections 34 and 36, when the plug is in use, fit
closely to the sides of the bore hole to reduce blast leakage
around the sides of the plug. In the preferred embodiment the
flange sections are in part integral with the rear claws 20. In
this situation the flange sections play an important reinforcing
role in aiding the members 20 to withstand the force of the
blast .
The manner of use of the plug is as follows. After a
hole 43 has been drilled and the explosive charge planted in the
hole, the plug of the present invention is inserted into the
hole. The charge is then exploded. The force of the explosion
causes a flexing of the plug and causes the plug to move up the
hole slightly. This serves to set the claws 18 and 20 into the
sides of the hole to confine the blast. ~ comparison of FIGURES
5 and 6 illustrates clearly the position before and after the
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blast.
The setting vf the claws in this manner is aided by the
extra force which is brought to bear on the plug by reason of the
flat portion 44 of the truncated conical end 16. Thus a fairly
flat such end portion is highly preferred. The basic requirement
is that the plug not allow the blast to escape up the bore hole
and that the plug therefore be closed.
In this way the force of the blast is substantially
confined to the hole and so to the surrounding formations.
The plug 10 is then normally left in the hole as a
topping plug and the filling material, such as concrete, then
poured in on top. In use the upward force exerted by the plug
during the blast looses a substantial amount of material from the
walls 52 tFIGURE 6) of the hole which material then becomes
topping fill.
Thus it is apparent that there has been provided in
accordance with the invention tamping and topping plug for bore
holes that fully satisfies the objects, aims and advantages set
forth above. While the invention has been described in
conjunction with specific embodiments thereof, it is evident that
many alternatives, modifications and variations will be apparent
to those skilled in the art in light of the foregoing
description. Accordingly, it is intended to embrace all such
alternatives, modifications and variations as fall within the
spirit and broad scope of the invention.
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