Detonator system with high precision delay

#1. Field of the Invention

#The present invention relates to a detonator (or blasting cap) system with high precision delay, and more particularly, to such a detonator system for mining, quarrying, and construction where the sequencing of detonation of output charges is important to achieve predetermined results.

#2. Description of the Related Art

#With the above and other related objects in view, the invention consists in the details of construction and combination of parts as will be more fully understood from the following description, when read in conjunction with the accompanying drawings in which:

#FIG. 1 represents an elevational view of shock tube 12 connected to housing 10 in position to be inserted inside the booster charge housing assembly 11.

#FIG. 2 shows an elevational cross-sectional view of the members shown in the previous figure with housing 10 in place.

#Referring now to the drawings, where the present invention is generally referred to with numeral 100, it can be observed that it basically includes detonator container or housing 10 with an open end 10a through which shock tube 12 enters and main charge assembly 11 cooperatively receives therein container 10. Latch assembly 14 engages container 10. As seen in FIG. 1, container 10 includes foldable anchorage member 13, having a substantially conical shape in one of the embodiments. FIG. 1 also shows a flexible membrane 16 that is cammingly pushed in when container 10 is inserted inside assembly 11. Assembly 11 includes main explosive charges 25. Membrane 16 is intended to prevent the entry of foreign material inside container 10. This mechanical displacement actuates switch 20, as shown in FIG. 2, thereby activating some of the circuits inside the container. As seen in FIG. 2, a portion of shock tube 12 penetrates inside container 10, which in turn is completely housed within assembly 11 with anchorage member 13 protruding passed end 18 with a through central opening 19. Assembly 11 has preferably a substantially cylindrical shape with an outer thread 15 for matingly receiving cooperating annular assemblies with additional explosive charge, as needed. In use, the combined assemblies 10 and 11 are typically suspended inside a vertical bore where it is deployed.

#Electric power source 29, in one of the embodiments, delivers electric power at two voltage levels: V1 and V2. V1 is used to power the digital logic and it has a relatively low voltage (i.e. 5 volts or less). V2 delivers a higher direct voltage to enable the sensors and provide the necessary energy to signal generator 35, voltage elevator 36, and firing assembly 34. In one of the embodiments, V2 can vary from 6 volts to 20 volts. Solid lines represent direct connections to the battery at times after switch 20 is closed. Terminals 20a and 20b provide separate connections to voltages V1 and V2.

#Redundant sensor assembly 31 includes two photosensors 42; 43, in one of the embodiments, for detecting the presence of the input impulse signal in shock tube 12. The interconnection of assembly 31 with the other assemblies is diagrammatically shown in FIG. 3, and in a more expanded form in FIG. 4. Redundant sensor assembly 31 sends two signals to control unit 33. The first signal comes from signal presence photosensor 42, with terminals 42a and 42b as shown in FIG. 4. Photosensor 42 is enabled when switch 20 is closed. When photosensor 42 detects the presence of the input pulse (by detecting the light emitted) it sends an electrical signal to control unit 33 and to presence circuit 46a. Unit 33 includes sufficient software and storage resources to initiate a counter with a pre-established count (time delay) that is accomplished in a given time period. Presence circuit 46a is activated. Control unit 33, in response, closes transistor switch 38 thereby activating photosensor 43. Photosensor 43 sends a signal to control unit 33 and to presence verification circuit 46b. Outputs from presence circuit 46a and presence verification circuit 46b are connected to the gates of transistors 39a and 39b, respectively. Switching transistor 39a is connected in series with switching transistor 39b and when both transistors are turned on, capacitor assembly 30 is connected to the ground permitting the latter to be charged up by voltage elevator 36. Switching transistors 39a and 39b can be implemented with N-channel MOSFET (metal oxide silicon field effect transistors) with minimum power consumption. The second signal comes from verified signal presence photosensor 43, with terminals 43a and 43b as shown in FIG. 4. Like with photosensor 42, photosensor 43 transmits a verification signal to control unit 33 and to presence verification circuit 46b. Circuit 46b in turn transmits a suitable signal to the gate of transistor 39b.