GB2574485A

GB2574485A - Hydrostatic signal tube interupt device

Info

Publication number: GB2574485A
Application number: GB1809505.9A
Authority: GB
Inventors: Jones Roy
Original assignee: ECS Special Projects Ltd
Current assignee: ECS Special Projects Ltd
Priority date: 2018-06-10
Filing date: 2018-06-10
Publication date: 2019-12-11
Anticipated expiration: 2038-06-10
Also published as: GB201809505D0; GB2574485B

Abstract

A shockwave interrupt device comprising a preferably transparent or semi-transparent housing 10 with a series of water entry ports (20, 60 Fig 1). Diametrically opposed signal tube retaining arms (30, 35 Fig 1) are inserted into the housing. The upper retaining arm 30 holds the lead line 160 while the lower retaining arm 35 holds the detonator 40. In use water enters the ports, forcing disc 140 against a spring 120. This in turn forces a cylindrical member 130 so that the passage 180 through the shock tube is completed. If the device is not armed the shockwave is diverted into a self-contained chamber 100.

Description

HYDROSTATIC SIGNALTUBE INTERUPT DEVICE

The present invention reiates generally to a hydrostatically actuated signal tube interrupt device, used for example to interrupt an explosive shockwave created after initiation in a signal 5 lead line leading to a subsea explosive charge. Embodiments of the invention are suitable for use as a safety interrupt whenever a non-electric explosive fuze, generally referred to in the art as “shocktube”, is employed to initiate an explosive charge when used for, but not limited to, Explosive Ordnance Disposal (EOD) demolition and neutralisation of target or nuisances ordnance in a marine environment. However embodiments of the invention have a wide range 10 of other marine applications.

Background

When historic or nuisance subsea munitions are required to be neutralised or detonated in a controlled manner this is generally achieved by the positioning of an explosive disposal charge 15 adjacent to the target ordnance such that when it is initiated it generates a sympathetic detonation of the target ordnance.

Due to the location of the target ordnance, the preparation of this disposal charge is typically undertaken on the deck of a ship.

A disposal charge, typically consisting of plastic explosive, is prepared and a detonator is fitted. The detonator is connected to a signal line; increasingly the signal, or “lead line” as it is usually referred to, is non-electric shocktube.

Shocktube is a small diameter, three-layer piastic tube coated on the innermost wall with a reactive explosive compound, which, when ignited, propagates a low energy signal, similar to a dust explosion. The reaction travels at approximately 2,000 metres per second along the length of the tubing with minimal disturbance outside of the tube

It is this lead line that will carry the signal from the surface to the disposal charge after its placement subsea. The lead line is then generally connected to a signal initiation device, usually a RF receiver, housed in a marine float. Once prepared this setup can then be lowered into the water and using an underwater remotely controlled vehicle (ROV) or other means it can be placed into position adjacent to the target ordnance.

At this point the disposal charge setup, which is still on the ship, is susceptible to premature initiation from stray RF signals or perhaps a lightening strike, whilst these occurrences are rare the result of this premature initiation is usually catastrophic for personnel and equipment in the vicinity.

Summary

This invention is a shockwave interrupt device that is installed into a shocktube lead line immediately before the detonator to remove the possibility that, should an unexpected initiation 10 of the leadline occur, the resultant shock wave would not reach the detonator thus preventing premature explosion.

The invention employs a fail-safe design to divert the signal wave into a chamber whilst simultaneously closing the pathway to the detonator. However, when the device is lowered into 15 the water and safely submerged to a predetermined depth, the hydrostatic pressure actuates the device thereby allowing for the progression of the shockwave to transit normally to the detonator and initiate the explosive charge as required to neutralise the target ordnance.

Detailed Description

Embodiments of the invention will now be described by way of exampie only and with reference to the accompanying drawings in which:

Figure 1 is a perspective view of an interrupt device according to embodiments of the invention; 25

Figure 2 is longitudinal cross section of the interrupt device according to embodiments of the invention in the “Safe” mode;

Figure 3 is a longitudinal cross section of the interrupt device according to embodiments of the 30 invention in the “Armed mode

Referring particularly to to Figure 1, in this example it shows a perspective view of the interrupt device according to embodiments of the invention, Figures 2 and 3 being longitudinal cross sections in the “Safe and “Armed” mode. The illustrated interrupt device generally indicated by 35 numeral 10, is a generally hollow housing which may be cylindrical and may of a resilient material which may be polycarbonate, poly methyl methacrylate, or similar and preferably transparent or semi-transparent in nature and having a series of one or more water entry ports 20 at the forward end are preferably but not essentially circular in shape and may be radially distributed around the circumference of the forward section 80, this section may be cylindrical and may be coincident, larger or smaller in diameter to the main section. The termination of this 5 elongated section may be closed with a screwed cap 50, which may be of polymer materia! and also may have one or more water entry ports 60.

in the centre of the rear section of the housing are two perpendicular diametrically opposed shocktube retaining arms 30 and 35 which are inserted into the housing into which shocktube 10 can be inserted and retained. The shocktube from the lead line 160 when inserted into the inlet arm 30 and the shocktube to the detonator 40 when inserted into the retaining arms are positively retained at a fixed distance apart (not shown in this view). In this example the arms are of a non-rigid material such as transparent silicon tubing, which is bonded into the housing and the shocktube is retained by a suitable metal crimp 70.

At the rear of the housing may be a nut 55 that allows for attachment to a convenient structure within the demolition charge setup, but various methods of attachment to the host setup may be employed.

Referring particularly to Figure 2, in this example the interrupt device is held in this position as the spring 120 is sufficient to overcome ambient pressure. The housing 10 has a small cylindrical bore 90 in the centre, which connects an enclosed chamber 100 at the rear, which also may be conveniently cylindrical, to a main elongated cylindrical bore 110, which extends towards the forward section and may be closed with a screwed end cap 50. In the cylindrical bore 110 is a spring 120, which can be changed or adjusted to resist water pressure at various desired depths.

This spring 120 acts on the centre of a flanged cylindrical member that extends forward and rearwards, at the forward end of this member it passes through an anti-rotation disk 140 such 30 that it is allowed to freely move in a linear manner. This member has an extended cylindrical section towards the rear that fits into the centre bore of the housing 90.

Embodied into the rear end of this member of this example is a diverting feature 150, which may be concave semi-cylindrical in form, that whilst not submerged, coincides with the 35 shockwave entry port 170 in the housing to divert the signal from the lead line 160 into the chamber 100, which may have a non-return valve fitted to vent excess pressure, while simultaneously closing the access port 180 to the detonator.

In this configuration should unexpected initiation occur the resultant shockwave is diverted by 5 the feature 150 embodied in the end of the cylindrical member into the chamber 100.

Referring particularly to Figure 3, in this example it is assumed that the interrupt device is underwater and at, or beyond, the chosen actuation depth for the interrupt device. Water has entered the forward section of the housing through the water entry ports 20 and the increased 10 pressure due to depth has acted upon the retained seal 190, which may have a “U” shaped cross section as shown in the preferred example, the increased pressure on this seal 190 being preferably of “ll cross section, causes the outer edges to act upon their mating surfaces to increasingly ensure that the seawater does not permeate into the centre section of the housing.

The force therefore acts in a linear direction on the cylindrical member 130 and in overcoming 15 the resistance of the spring 120, which has been preset to a desired depth, causes the cylindrical member 130 to move rearwards.

This movement of the cylindrical member simultaneously aligns the transfer hole 200 in the cylindrical member with the shockwave entry port 170 with the detonator access port 180 in the 20 housing and moves the diverting feature 150 out of position.

In this configuration, any shock wave signal sent though the shocktube lead line 160 will pass directly to the shocktube detonator 40 and initiate the disposal charge.

Obviously many modifications and variations of the invention are possible in the light of the above teachings, it is therefore understood that within the scope of the appended claims that the invention may be practiced otherwise than as specifically described.

Claims

1. A shockwave interrupt device that diverts and arrests a shockwave created in low

5 energy explosive signal tube that is actuated at a preset depth of water comprising:

A housing having an elongated bore therein;

means of attaching two or more signal tubes and containing a reciprocally operating member;

means of closing, diverting and opening a shockwave incorporated into said member;

10 means responsive to ambient water pressure operatively associated with said member;

means of dissipating a percussion shockwave to prevent explosion.

2. A shockwave interrupt device that arrests and diverts a shockwave created in a low energy signal tube that is actuated at a preset depth of water comprising;

15 A transparent housing that has one or more water entry ports at the forward end.

A flanged cylindrical member with extended cylindrical forms on each side

A convex semi-cylindrical form on a cylindrical member that simultaneously diverts the shockwave and blocks access to the detonator

A “U” shaped seal on the cylindrical member

20 Flexible, perpendicular diametrically opposed signal tube retaining arms and retaining crimps

An anti-rotation disk to restrict the movement of the cylindrical member to a linear direction

An integral expansion chamber for dissipation of the shockwave

3. A shockwave interrupt device that diverts and dissipates a shockwave created in low energy explosive signal tube where the device is manually armed.

4. An assembly as claimed in any preceding claim in which the form in the cylindrical

30 member to divert the shockwave is angular, hemi-spherical or of other convex geometric shape.

5. An assembly as claimed in any preceding claim in which the housing is in one or more sections and screwed or bonded together.

6. An assembly as claimed in any preceding claim in which the housing has one or more water entry ports that are not circular or are of irregular distribution.

7. An assembly as claimed in any preceding claim in which the signal tube retaining arms

5 are silicon tubing or similar flexible transparent or semi-transparent polymer and are screwed, affixed or bonded into the housing.

8. An assembly as claimed in any preceding claim in which the signal tube is retained in the housing by means of a push-fit connector or gland arrangement.

9. An assembly as claimed in any preceding claim in which the housing is cylindrical, hexagonal or of other geometric form.

10. An assembly as claimed in any preceding claim in which the housing is semi-

15 transparent or opaque.

11. An assembly as claimed in any preceding claim where the expansion chamber has a non-return arrangement to vent excess pressure.

20

12. A device comprising a plurality of signal tube entries/exits, each as claimed in any preceding claim.

13. Any of the assemblies substantially as hereinbefore described with reference to the accompanying drawings.

14. Any of the devices substantially as hereinbefore described with reference to the accompanying drawings.