Detonator sensor assembly

Abstract

A sensor assembly for use in actuating an electronic detonator in response to a shock tube event propagated through a shock tube, the sensor assembly including support, and at least one sensor on a surface of the support, the support being configured to position the at least one sensor displaced laterally from a line of action of the shock tube event.

Claims

1. In combination a sensor assembly and a shock tube, wherein the sensor assembly is used in actuating an electronic detonator in response to a shock tube event propagated through the shock tube, the sensor assembly including a cylindrical support, a plurality of sensors arranged circumferentially on an inner surface of the cylindrical support and a screen over the sensors, the support being configured to define an interior, located at an end of the shock tube, into which a shock wave is propagated in an axial direction along a line of action and with the plurality of sensors displaced laterally from the line of action.

2. A combination according to claim 1 wherein the plurality of sensors is selected at least from a light sensor, a pressure sensor, and a plasma sensor, for respectively sensing light changes, pressure changes and plasma generated by the shock tube event.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is further described by way of examples with reference to the accompanying drawings wherein;

(2) FIG. 1A is a cross-sectional longitudinal view of a portion of a sensing assembly according to a first embodiment of the invention;

(3) FIG. 1B is an end view of the sensing assembly of FIG. 1A;

(4) FIG. 2 is a view of a sensing assembly according to a second embodiment of the invention; and

(5) FIG. 3 shows a plasma sensor used in the sensing assembly of FIGS. 1A and 1B.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIGS. 1A and 1B show a first embodiment of a sensing assembly 10 contained in a housing 12 connected to an end 14 of a shock tube 16 through which a shock wave 18 is propagated in an axial or longitudinal direction 19.

(7) The sensing assembly 10 includes a support 20 made from a flexible substrate. A plurality of sensors 22, configured to detect parameters specifically and uniquely associated with a genuine shock tube event, is located on a surface 24 of the support 20. The support 20 is rolled into a cylinder 25 (FIG. 1B), with the surface 24 facing towards an interior 26 of the cylinder 25. A transparent, flexible screen 28 covers the sensors 22.

(8) In use, the shock wave 18 is propagated into the interior 26 of the cylinder and the sensors 22, protected by the screen 28, sense signals associated with different parameters which are uniquely linked to the shock wave. Data of the sensed signals are sent to a processor 30 to verify that the signals are indeed originated by a genuine shock tube event. The processor 30 sends a signal to a switch 32 which activates a timer to time detonation of an electronic detonator (not shown).

(9) FIG. 2 shows another embodiment of a sensing assembly 10A where a support 20A is configured to be wrapped around a wall 34 of a shock tube 14A. The shock tube wall 34 is preferably transparent. An assembly of sensors 22A faces an outer surface 36 of the wall 34. A shockwave 18A, propagated through the shock tube 14A, is detected by the sensors 22A and signals produced by the respective sensors are verified in the same manner as previously described.

(10) In the first embodiment, which is illustrated in FIGS. 1A and 1B, the sensors are a combination of light sensors, pressure sensors and plasma sensors. Only light sensors are suitable for use in the second embodiment, which is illustrated in FIG. 2.

(11) The light sensors are generally organic photovoltaic sensors capable of sensing a light signal through the screen 28, or the wall 36, in the first and second embodiments, respectively. If the signal has the appropriate characteristics, then the light signal is verified by the processor 30 and a command is sent to the timer switch 32. An output of the organic photovoltaic sensor can be optimised to respond in less than 50 micro seconds.

(12) Each pressure sensor is selected from the following; a piezoresistive strain gauge, a capacitive pressure sensor, an electromagnetic pressure sensor, a piezoelectric sensor, an optical pressure sensor, a potentiometeric pressure sensor, a resonant pressure sensor, a thermal pressure sensor and an ionization pressure sensor. The pressure sensor is in a confined volume of a size defined by the housing 12. The shockwave 18 which exits the shock tube 16 at the end 14 enters the volume. A pressure signal produced by the sensor is verified and processed in the manner which has been described in the case of the light sensor.

(13) FIG. 3 shows a plasma sensor suitable for use in the sensing assembly 10 of the first embodiment, which is shown in FIGS. 1A and 1B. The sensor includes the support 20, which is made from an organic material or a metal oxide, and four interconnected contacts 38, made from a copper circuit with a gold overlay, which are located in or on the support. The contacts 38 are connected to conductive tracks or rods 40 which extend through the protective screen 28. The contacts 38, in response to a plasma pulse propagating through the interior 26, generate a signal which is dependent on a change in the conductivity between the contacts. The signal is propagated via the tracks 40 to a processor for verification in the manner described.

(14) The pressure and plasma sensors are not suitable for use with the second embodiment, which is illustrated in FIG. 2.

(15) Due to the protection provided to the sensors by means of the screen 28 in the first embodiment and by the wall 36 in the second embodiment, the sensors are not damaged by the shock tube event and the risk of data not being processed due to damaged sensors is substantially diminished.