Detonator retention system for boosters

Abstract

The present invention relates to a device, a system and a method for retaining detonators in an explosive booster, particularly a retention device for retaining a detonator in the blind hole of a booster which allows the safe extraction thereof from the booster. The retention device comprises a flexible holding means that is movable between a blocking position retaining the detonator inside the blind hole and an open position which allows extracting the detonator from the blind hole.

Claims

1. A retention device adapted to retain detonators inside a booster, said booster comprising: an explosive charge, a through hole comprising a first end and a second end, and a blind hole comprising one end, wherein the retention device comprises, at least one outer face and at least one inner face, at least one substantially flat portion on said at least one outer face, at least one flexible holding device located substantially in said at least one substantially flat portion on the at least one outer face, at least one first opening located in said at least one substantially flat portion, and at least one second opening located in said at least one substantially flat portion, wherein the at least one first opening is adapted to allow the detonator to access the through hole, and the at least one second opening is adapted to allow the detonator to access the blind hole, wherein the at least one flexible holding device is arranged substantially next to each at least one second opening, and said flexible holding device comprises a flange connected to the at least one substantially flat portion, wherein the flange comprises (i) a flat retaining edge that is substantially parallel to the at least one substantially flat portion, and (ii) a free end defined as a conical or flat, and inclined surface of revolution, wherein the flat retaining edge of the flange is positioned in closer proximity to the at least one second opening, wherein the flange will deflect in a radial direction when the free end is pushed axially but will not deflect when a force is exerted perpendicular to the flat retaining edge.

2. The retention device according to claim 1, additionally comprising a protective element, said protective element comprising a substantially flat surface with a recess, said recess being adapted for housing the at least one substantially flat portion, the at least one flange, the at least one first opening and the at least one second opening, thus permitting access to the at least one flange.

3. The retention device according to claim 2, wherein the at least one substantially flat portion and the substantially flat surface of the protective element are connected through a wall.

4. The retention device according to claim 1, comprising one or more centering ribs arranged in the at least one substantially flat portion and substantially next to each at least one second opening, the one or more centering ribs being adapted to guide a detonator through each at least one second opening when said detonator is introduced in said at least one second opening.

5. The retention device according to claim 1, comprising two second openings.

6. The retention device according to claim 1, wherein the at least one flange is movable from outside of the booster between a blocking position retaining a detonator inside the blind hole and an open position to extract the detonator from said blind hole.

7. The retention device according to claim 1, comprising one or two flanges.

8. The retention device according to claim 1, wherein the retention device is prismatic or cylindrical.

9. A booster comprising an explosive charge and a retention device according to claim 1, wherein the retention device is located at one of the ends of the booster.

10. The booster according to claim 9, wherein the booster has a cylindrical or prismatic shape.

11. The booster according to claim 9, comprising a case, wherein the case of the booster is adapted to contain the explosive charge and the retention device is located at a first end of the case.

12. The booster according to claim 11, comprising a cover located at a second end of the case.

13. The booster according to claim 12, comprising at least one through hole in the explosive charge and at least one blind hole in the explosive charge, such that the longitudinal axis of each through hole coincides with the longitudinal axis of each first opening of the retention device and the longitudinal axis of each blind hole coincides with the longitudinal axis of each second opening of the retention device.

14. The booster according to claim 9, wherein there are no plastic tubes defining the blind hole, the through hole, or both the blind hole and the through hole.

15. The retention device according to claim 1, wherein the at least one flange is moved to the open position using a finger or tool.

16. A method of assembling a booster assembly, said method comprising the following steps: providing a booster according to claim 13, introducing a detonator through a first end of the through hole of the booster, until the detonator comes out through the second end of the through hole of the booster, and introducing the detonator through the end of the blind hole of the booster by applying force on the free end of the at least one flange thus moving the at least one flange from an blocking position to an open position, such that when the detonator is completely housed in the blind hole, the at least one flange returns to the blocking position.

17. A method of disassembling a booster assembly, said method comprising the following steps: providing a booster assembly comprising the booster of claim 13 and a detonator, wherein detonator is completely housed in the blind hole and the at least one flange is in an blocking position, unblocking the at least one flange by applying axial force on the free end thus moving the at least one flange from the blocking position to an open position, and pulling on the end of the detonator and extracting the detonator from the booster.

Description

DESCRIPTION OF THE DRAWINGS

(1) The foregoing and other features and advantages of the invention will be more clearly understood based on the following detailed description of preferred embodiment, provided only by way of illustrative and non-limiting example in reference to the attached drawings.

(2) FIG. 1 shows a longitudinal section of the booster.

(3) FIG. 2 shows a bottom view of the booster, in which the retention device can be seen.

(4) FIG. 3 shows a top view of the booster.

(5) FIG. 4 shows a longitudinal section of the retention device.

(6) FIG. 5 shows a perspective cut-away view of the retention device.

(7) FIG. 6 shows another perspective cut-away view of the retention device from a different angle

(8) FIG. 7 shows a possible embodiment of the invention, with two holes for the detonator.

(9) FIG. 8 shows a possible embodiment of the retention device with two flanges.

(10) FIG. 9 shows a bottom view of the booster with two flanges.

(11) FIG. 10 shows a longitudinal section of the booster with a detonator partially inserted in the blind hole.

(12) FIG. 11 shows another longitudinal section of the booster with a detonator completely inserted and retained in the blind hole.

DETAILED DESCRIPTION OF THE INVENTION

(13) The present invention relates to a retention device (1) for detonators (13) in an explosive booster (100), an explosive booster (100) and a method of assembling and disassembling same. Particularly, it relates to a device which allows effectively retaining one or more detonators (13) inside a hole (10) of the booster which does not only prevent the detonator from coming completely or partially out of the hole (10) where it is housed, but also allows extracting the detonator safely if blasting is suspended, such that the risk of accident during handling is minimized. An additional advantage is that, effectively, the retention device (1) is arranged outside the booster (100), reducing the risk of damaging the explosive charge (12) during handling and allowing the operation of the retention device (1) by simply moving the flexible holding means or device (3) with one finger.

LIST OF NUMERICAL REFERENCES

(14) 1 Retention device 2 Cover 3 Flexible holding means 3a Free end 3b Flat intermediate part 3c Cylindrical inner part 4 Centering rib 5 Second opening 6 First opening 8 Wall 9 Through hole 10 Blind hole 11 Perforation 12 Explosive charge 13 Detonator 15 Substantially flat portion 16 Inner face 17 Outer face 18 Substantially flat surface 19 Recess 20 Protective element 100 Booster
Booster

(15) The booster (100) is an element known in the field of the art consisting of a very powerful explosive charge (12), envisaged for setting off other low-sensitivity explosives. Generally, boosters are formed by a cylindrical block of explosive material or explosive charge (12) with two perforations or holes, a through perforation (9) and another blind perforation (10), and externally covered by a casing commonly referred to as a case or shell, made of a lightweight material, such as plastic, for example. The blind hole (10) is used for housing the detonator (13) intended for setting off the booster (100), whereas the through perforation (9) is intended for allowing the passage of the detonator attached to its setting wire through the booster; once on the opposite side, the detonator (13) is completely introduced into the blind perforation (10), only the portion corresponding to the connection with the wires projecting outwards.

(16) Preferably, the retention device (1) is placed at the lower end of the booster (100) such that it retains the detonator more securely as a result of the wire being lopped once through the through hole (10) of the booster, preventing the entire weight of the booster assembly from being supported by the retention device (1). Therefore, when the booster assembly is introduced to the bottom of a shot hole, the booster does not hang directly from the retention device, rather part of the stress is absorbed by the wires that have been passed through the through hole (10) of the booster (100).

(17) It is possible to manufacture the booster by means of a process of casting the explosive material directly in the case, placing metal rods for obtaining the through hole (9) and the blind hole (10). It is also possible to integrate the retention device (1) with the case of the booster. The booster can therefore be manufactured with a minimum of processes and of individual parts. Finally, a cover (2) with a perforation (11) which allows accessing the through hole (9), and which at the same time closes the case and protects the explosive charge (12) of the booster, as shown in FIG. 3, can be placed.

(18) This solution prevents the use of plastic tubes for the hole of the detonator, thereby not only reducing the number of parts and material used, but allowing better wave transmission from the detonator to the explosive charge of the booster.

(19) Retention Device

(20) FIG. 2 shows the lower end of a booster (100) in which the retention device (1) and the position of the flexible holding means (3) and the centering ribs (4) can be seen. In a preferred embodiment, such as the one shown in FIG. 1, the retention device (1) comprises two openings (5, 6), centering ribs (4) and flexible holding means (3) which in the present embodiment correspond to a flexible flange.

(21) FIG. 5 shows the element identified as the substantially flat portion (15), corresponding to a base on which the flexible holding means (3), the centering ribs (4) and the openings (5, 6) are located. Generally, this flat portion (15) is the structural element supporting the retention device (1), and can form a step, as seen in FIGS. 5 and 6, or be arranged at a different level.

(22) The openings (5, 6), which are circular in this embodiment but may have any other section, allow access to the holes (9, 10) of the booster (100). The second opening (5) which is coaxial with the blind hole (10), has flexible holding means (3) located next to the opening (5), such that the flexible holding means (3) are located at a distance from the opening (5) sufficient so as to leave the access free in the open position and to be interposed thereon in the closed position. In a possible embodiment, there is more than one second opening (5), envisaged for the case in which more than one detonator (13) is required for setting off the booster (100). FIG. 7 shows a particular embodiment of a retention device (1) comprising two second openings (5) and the corresponding two blind holes (10) for using the booster with two detonators. Similarly, embodiments with more than one first opening (6) are also possible to allow the passage of several wires of the detonator (13). FIGS. 4, 5 and 6 show with greater clarity a particular embodiment of the openings (5, 6), with an almost tubular shape projecting perpendicularly from the substantially flat portion (15) towards the inner face (17). This particular shape constitutes a further centering element for the detonator (13), while at the same time allows linking the openings (5, 6) with the holes (9, 10) of the booster (100).

(23) As shown in the embodiments of FIGS. 4-9, the centering ribs (4) are elements attached to the substantially flat portion (15) that project outwards in a direction substantially perpendicular to the flat portion (15); furthermore, the centering ribs are arranged close to the border of the second opening (5). The function of these centering ribs (4) is to help the operator to center the detonator (13) in the opening (5). In a particular embodiment, the centering ribs (4) have an almost prismatic shape, with the face arranged opposite the opening (5) being substantially cylindrical, the free end thereof being a conical surface of revolution. FIG. 7 shows a particular embodiment with thinner centering ribs (4) than in the other embodiments shown. It is possible to arrange more than one centering rib (4) per opening, as shown in FIG. 7, as it is also possible to carry out the invention without any rib.

(24) FIG. 4 shows a section of the retention device (1) in which the design of the flexible flange is seen. The flange comprises three parts: a rod attached to the flat portion (15) that will be referred to as a cylindrical inner part (3c), a flat intermediate part (3b), acting as a retainer and furthermore serving as a transition between the inner part and the end of the flange, and a free end (3a), substantially wider than the cylindrical inner part (3c), and with a conical shape of revolution.

(25) Said shape is optimized to make introduction of a cylindrical detonator easier and to cause the movement of the free end (3a) of the flange in a radial direction when it is pushed axially with a detonator (13). Since the cylindrical inner part (3c) is attached to the retention device (1), the flange swivels and allows the passage of the detonator (13). When the detonator (13) is arranged completely in the blind hole (10), it no longer presses on the free end (3a) of the flange and allows the flange to return to the blocking or standby position. In the blocking position, the detonator (13) is retained on the edge of the flat intermediate part (3b) of the flange, even pulling on the wires of the detonator.

(26) FIGS. 8 and 9 show a particular embodiment with two flexible flanges. In these drawings, the two flanges are arranged covering almost half the second opening (5); the incorporation of the second flange increases the safety of the retention device (1) because it allows obstructing almost half the second opening (5), assuring the retention of the detonator (13), and because if one of the flanges breaks or is rendered useless, the other one would allow retaining the detonator (13) in the blind hole (10).

(27) The protective element (20), which can be seen in detail in FIG. 5, is an element of the retention device (1) offering shelter to the holding means (3) and other elements of the device (1), which due to their shape are susceptible of getting caught on something or sustaining blows rendering them useless. The protective element (20) is defined based on a substantially flat surface (18) located above the flange and of the centering ribs (4), such that it acts as a casing for the retention device (1). To make access to the flange and the openings (5, 6) easier, the protective element (20) has a recess (19) in its central area, slightly wider around the flange; said recess (19) is connected with the substantially flat portion (15) through a wall (8).

(28) Method of Putting in and Taking Out a Detonator

(29) When the operator is going to use the explosive booster, he passes the detonator completely through the cavity (11) of the cover (2) and the through hole (9), the detonator coming out through the first opening (6). Then, the detonator is introduced in the second opening (5), pressing on the conical face of the free end (3a) of the flange, and passing through the centering ribs (4). When the entire detonator (13) has been introduced into the blind hole (10), the flange is no longer bent, and the edge of the intermediate flat part (3b) of the flange acts as a mechanical retainer for retaining the detonator. The detonator is therefore held during the introduction of the booster assembly into the shot hole.

(30) FIG. 10 shows a section of the booster (100) in the moment in which the detonator (13) is introduced into the blind hole (10). The flange (3) is seen in the open position, moved radially with respect to the axis of the through hole (10).

(31) FIG. 11 shows the booster (100) with the detonator (13) introduced completely into the hole (10) thereof. The flexible flange (3) prevents its extraction, even when pulling on the wires of the detonator. Depending on the type of detonator, retention occurs in the cap of the detonator or in the channels of the crimper of the detonator (13).

(32) Similarly, if the operator decides to take out or extract the detonator (13) from inside the booster (100), he must press on the flexible flange, bending it, and pulling on the wires of the detonator. This operation of bending the flange can be performed simply with one finger or with any tool.