The present invention relates to apparatus for retaining a material

breaking device. The material may be coal or rock.

The device to be retained is sold under the Cardox trade mark and is

an alternative to explosives. It comprises a housing containing a charge of

liquid carbon dioxide and a heater which can be activated remotely by

electrical means. In operation the housing is placed in a hole bored into the

coal or rock to be broken and the heater electrically activated from a remote

location. This causes the liquid carbon dioxide to convert to high pressure

gas which bursts a seal in the housing escaping into the coal or rock to

effect the required breaking action. If the housing is not retained within the

coal or rock during this action it is ejected and the breaking effect is

reduced. Various methods of achieving this have been suggested in the

past. One is described in International Application No. PCT/GB95/0I233

filed by George Henry Webb. In the arrangement described in this

application sealing rings are forced under the pressure of the gas along a

divergent cone into sealing engagement with the wall of the hole in which

the device is disposed thus preventing it from being ejected from the hole.

Whilst this arrangement works well further development has led to a simpler

and less expensive but equally reliable altemative.

According to the present invention, there is provided apparatus for

retaining a device in a bore in a mass of material to be broken by the device

on activation of the device comprising a member adapted for connection to

the device and defining a passage for conducting gas from the device on

activation thereof to the bore in the material, a member operative to engage

the wall of the bore and means for supporting the member, the member and

means for supporting being such that when the member is moved under gas

pressure relative to the means for supporting the member is expanded out

into contact with the wall of the bore to retain the apparatus and any device

connected thereto in the bore.

In a preferred embodiment of the invention the member adapted for

connection to the device is screwthreaded at both ends. One end is

externally screwthreaded for connection to a complementary internally screwthreaded bore in the device. The other end is externally screwthreaded

for connection to a complementary internally screwthreaded housing. This

housing houses and retains one end of a bolt which provides a mount

towards its other end for the means for supporting. This means for

supporting comprises a cone which is coaxially mounted on the bolt. The

member is mounted on this cone and comprises a nylon bush defining an

internal complementary conical bore and having a slot which extends from

the bore to the surface of the bush and between axial ends of the bush. The

slit may be "Z" shaped when viewed in side elevation or may simply extend

axially from one axial end of the bush to the other preferably at an angle to

the centreline of the bush. Under gas pressure the bush is pushed along the

cone opening the slit and allowing the bush to seaiingly engage the wall of

the bore to retain the apparatus and any device connected to it in the bore.

The gas pressure tends to close the central portion of the Z restricting any

flow of gas through the sift. However the differential areas at opposite ends

of the bush subject to gas pressure produce a net force urging the bush

along the cone and therefore into contact with the wall of the bore.

In order that the invention may be more clearly understood one

embodiment thereof will now be described by way of example with

reference to the accompanying drawings in which:*

Figure I shows a cross-sectional view of one form of device to be

retained by apparatus according to the invention,

Figure 2 shows a cross-sectional view of one form of apparatus

according to the invention for use with the device shown in figure 1,

Figure 3 diagrammatically shows the apparatus prior to activation of

the device.

Figure 4 diagrammatically shows the apparatus after activation of the

device,

Figure 5 shows a perspective view of part of the apparatus of figure

2,

Figure 6 is a side elevational view of the part of figure 5 and

Figure 7 is an axial cross sectional view of the part of figure 5.

Referring to Figure I, the device comprises a housing I having a

sealing plug 2 screwed therein at one end and a seal 7 at the other end

which may be ruptured under gas pressure. The housing I contains a

chemical energiser or heater 3 in which an electrically operable activator 4

is inserted. Electrical conductors 5 lead from the activator 4 to holes 6

where external conductors (not shown) may be connected to the

conductors 5. The holes 6 are formed in the plug 2 and the plug also

defines a passage 8 through which the conductors 5 extend. The plug 2

also defines a passage 9 in which a carbon dioxide filling valve 10 is

disposed and through which liquid carbon dioxide may be supplied to the

housing I. Devices of this nature are well known and are supplied under the

trade mark Cardox.

Referring to Figure 2, the retaining apparatus comprises a body

connector II having an externally screwthreaded portion 12 which is adapted

to be screwed into a complementary internally screwthreaded bore 13

formed in that end of the housing I remote from the valve 10. The connector

defines a bore 12a extending axially and emerging at aperture 12b from the

connector II. The body connector II has a further similar externally

screwthreaded portion 14 which extends in the opposite direction to that of

the portion 12 and which is screwed into a complementary screwthreaded

aperture in a cone bolt housing 15. This housing 15 includes a neck portion

16 of reduced radial dimension which prevents the head 17 of the cone bolt

18 disposed in the housing 15 being withdrawn from the housing. A rubber

buffer 19 is disposed between the head 17 and the portion 14. The cone bolt

18 extends from the cone bolt housing 15. This bolt 18 is externally

screwthreaded at 20 and a frusto cone 21 is screwed onto the bolt. A high

density nylon bush 22 concentrically surrounds the bolt 18 and is axially

disposed between the housing 15 and the frusto-cone 21. Referring to

Figures 5, 6 and 7 this nylon bush 22 defines an internal frusto-conical bore

23 and is provided with an expansion slot 24. When viewed on the surface

of the bush 22, the slot is approximately 'Z' shaped, the top and bottom

portions of the "Z" subtending an angle of approximately I20o on the

centreline of the bush. The angle of the sides of the frusto-conical bore 23

to the axis of the bore is about 13°. The above angles may be varied as

desired. As an alternative, a diagonal expansion slot may be employed

instead of the 'Z' shaped slot described above. This alternative form of slot

is shown in dashed line at 25 in figure 3. The angle of the slot to the centre

line axis of the bush is 70° but this angle may be varied as desired.

The operation of the above described arrangement is as follows. The

apparatus and device are screwed together and placed in a bore in the mass

of material to be broken. The device is electrically activated in the normal

way via the electrical conductors 5. The heater 3 causes the liquid carbon

dioxide charge to gasify. This gas expanding very rapidly ruptures the seal

7 and flows through the bore 12a out through the aperture 12b into and

along the bore in the material in which the device is disposed to break up

the material. The pressure of the gas forces the nylon bush 22 axially along

the cone so that the cylindrical outer surface of the bush is forced into

contact with the wall of the bore of the material thus holding the retaining

apparatus and thereby the device connected to it firmly in position in the

bore in the material. The axially extending parts 24a of the 'Z' shaped slot

open up circumferentially under pressure from the gas thus promoting

circumferential expansion of the slot, but the pressure of the gas tends to

urge that part 24b of the slot which extends circumferentially to the closed

state which inhibits passage of gas to the other side (axially) of the bush.

This differential opening of different parts of the slot is shown on Figure 4.

Even if gas does pass to the other side of the bush there is a resultant force

due to the pressure of the gas urging the bush 22 along the cone and into

contact with the wall of the bore in the material because of the difference

in the areas of the bush subject to gas pressure at opposite ends of the

bush. The area 26 of the bush II adjacent the lesser diameter end of the

cone 20 subject to gas pressure is greater than the area 27 at the other end

of the bush. This is also the case when the alternative form of slot is used

although with that form of slot passage of gas from one side of the bush to

the other is easier.

It will be appreciated that the above embodiment has been described

by way of example only and that many variations are possible without

departing from the scope of the invention. For example, the bush may be

made of material other than nylon, and the member on which it is supported

may be other than conical. A nylon ring 31 may be provided at the large

diameter end of the cone 20 to prevent the bush 22 being pushed off the

bolt lδ.