Delay units and methods of making the same

• US 20060236887A1
• Filed: 02/06/2006
• Published: 10/26/2006
• Est. Priority Date: 02/08/2005
• Status: Active Grant

• Current Assignee: DYNO Nobel Incorporated (Incitec Pivot Limited)
• Original Assignee: DYNO Nobel Incorporated (Incitec Pivot Limited)
• Inventors: Childs, John, Shank, Lawrence J. III
• Granted Patent: US 7,650,840 B2
• Time in Patent Office: Days
• US Class Current: 102/272
• CPC Class Codes: F42C 9/10 the timing being caused by combustion F42C9/14 takes precedence

Abstract

A delay unit (10) comprises a timing strip (14) and, optionally, a calibration strip (20) deposited on a substrate (12). The timing and calibration strips comprise energetic materials which optionally may comprise particles of nanosize materials, e.g., a fuel and an oxidizer, optionally applied as separate layers. A method of making the delay units comprises depositing onto a substrate (12) a timing strip (14) having a starting point (14d) and a discharge point (14e) and depositing onto the same or another substrate a calibration strip (20). Timing strip (14) and calibration strip (20) are of identical composition and are otherwise configured, e.g., thickness of the strips, to have identical burn rates. The calibration strip (20) is ignited and its burn rate is ascertained. The timing strip (14) is adjusted by an adjustment structure to attain a desired delay period, preferably on the basis that the burn rate of the timing strip (14) is substantially identical to that of the calibration strip (20) and ascertaining the burn rate of the calibration strip. The adjustment may be attained by one or more of providing the timing strip with jump gaps (164), an accelerant or retardant (166a, 166b), completing the timing strip with a bridging strip (14c), or establishing a selected effective length of the timing strip by positioning one or both of a pick-up charge (16) and relay charge (18) over a portion of the timing strip.

Claims

1. A delay unit comprising a substrate having deposited thereon (a) at least one timing strip having a starting point and a discharge point spaced apart from each other, the distance along the timing strip between the starting point and the discharge point defining the effective length of the timing strip, and (b) a calibration strip, the timing strip and the calibration strip each comprising an energetic material capable of conducting an energy-releasing reaction therealong, the calibration strip and the timing strip being separated from each other sufficiently to preclude ignition of the timing strip by the calibration strip.

2. The delay unit of claim 1 wherein the energetic material of at least the timing strip is selected from the class consisting of a fuel and an oxidizer.

3. The delay unit of claim 2 wherein the energetic material of at least the timing strip is comprised of at least one discrete layer of fuel and at least one discrete layer of oxidizer, the layer of fuel and the layer of oxidizer being in contact with each other.

4. The delay unit of claim 1, claim 2 or claim 3 wherein the energetic material of the calibration strip is substantially the same as the energetic material of the timing strip.

6. The delay unit of any one of claims 1, 3 or 5 wherein the timing strip comprises a first strip having a terminal gap, and a bridging strip connecting the first strip to close the terminal gap, the first and bridging strips cooperating to define the effective length of the timing strip between the starting point and the discharge point.

7. The delay unit of claim 6 wherein the timing strip further comprises a second strip, the second strip being separated from the first strip by the terminal gap and the bridging strip connects the first strip to the second strip.

8. The delay unit of claim 6 wherein the energetic material comprises nanosize particles.

9. The delay unit of any one of claims 1, 3 or 5 wherein the energetic material comprises nanosize particles.

10. The delay unit of any one of claims 1, 3 or 5 further comprising a pick-up charge in signal transfer communication with the starting point of the timing strip and a relay charge in signal transfer communication with the discharge point of the timing strip.

11. The delay unit of any one of claims 1, 3 or 5 further comprising at least one of (a) a pick-up charge in signal transfer communication with the starting point of the timing strip, and (b) a relay charge in signal transfer communication with the discharge point of the timing strip, and wherein a portion only of the timing strip is covered by at least one of the charges whereby the effective length of the timing strip is determined by placement of the charge or charges.

12. The delay unit of claim 11 wherein both the pick-up charge and the relay charge are present and at least one of the charges covers a portion of the timing strip.

13. The delay unit of any one of claims 1, 3 or 5 further comprising a pick-up charge spaced from a relay charge and a plurality of the timing strips connected in signal transfer communication at one end of the timing strips to the pick-up charge and at the other end of the timing strips to the relay charge, to provide redundant timing strips to initiate the relay charge.

14. The delay unit of claim 13 wherein the timing strip has a first bus area at its starting point and a second bus area at its discharge point, the first bus area being in signal transfer communication with the pick-up charge and the second bus area being in signal transfer communication with the relay charge.

15. The delay unit of claim 14 wherein the second bus area is enlarged relative to the timing strips whereby the energy released at the second bus area is greater than the energy released along the timing strips.

16. The delay unit of any one of claims 2, 3 or 5 wherein the oxidizer comprises TiO₂.

17. The delay unit of any one of claims 1, 3 or 5 wherein the timing strip comprises an adjustment structure selected from the class consisting of one or more jump gaps, one or more accelerants and one or more retardants.

18. The delay unit of any one of claims 1, 3 or 5 wherein the energetic material comprises nanosize particles of fuel M′

and oxidant MyOx wherein M′ and

M are the same or different metals and y and x may be the same or different positive integers 1, 2, 3 . . . n.

19. The delay unit of claim 18 wherein M′

and M are selected from one or more of Ag, Al, B, Cu, Hf, Si, Sn, Ta, W, Y and Zr.

20. The delay unit of claim 18 wherein M′

and M are selected from one or more of Al, Cu and Ag.

21. The delay unit of any one of claims 1, 3 or 5 wherein the timing strip is comprised of a major portion and a minor portion, the major portion having an effective length greater than that of the minor portion and the minor portion having a burn rate greater than that of the major portion, the disparity in the respective lengths and burn rates of the major and minor portions being great enough that the burn time of the minor portion is negligible compared to the burn time of the major portion so that the delay period of the delay unit is substantially determined by the burn time of the major portion.

5. A delay unit comprising a substrate having deposited thereon at least one timing strip having a starting point and a discharge point spaced apart from each other, the distance along the timing strip between the starting point and the discharge point defining the effective length of the timing strip, the timing strip comprising an energetic material capable of conducting an energy-releasing reaction therealong, the energetic material being selected from the class consisting of a fuel and an oxidizer and wherein the energetic material is comprised of at least one discrete layer of the fuel and at least one discrete layer of the oxidizer, one of the layer of the fuel and the layer of the oxidizer contacting each other.

22. A method of making a delay unit comprising depositing onto a substrate a timing strip having a starting point and a discharge point, the timing strip comprising an energetic material comprised of a fuel and an oxidizer, the fuel and oxidizer being applied separately to the substrate as discrete layers of fuel and oxidizer which contact each other on the substrate.

23. The method of claim 22 further comprising depositing on the substrate a calibration strip of energetic material separated from the timing strip sufficiently to preclude ignition of the timing strip by the calibration strip.

24. The method of claim 23 wherein the energetic material of the calibration strip is substantially the same as the energetic material of the timing strip.

25. A method of making a delay unit comprising:

(a) depositing onto a substrate a timing strip having a starting point and a discharge point, the timing strip comprising an energetic material having a given burn rate along its length and the effective length of the timing strip being the length along the timing strip between the starting point and the discharge point, the effective length and burn rate of the timing strip determining the delay period of the delay unit;

(b) depositing onto a substrate a calibration strip of given length having an initial point and a finish point, the calibration strip being comprised of an energetic material which is substantially identical to the energetic material of the timing strip;

(c) igniting the calibration strip and measuring the time it takes for the calibration strip to burn from its initial point to its finish point to thereby ascertain the burn rate of the calibration strip; and

(d) after step (c), adjusting the effective length of the timing strip to attain a desired delay period on the basis that the burn rate of the timing strip is identical to the ascertained burn rate of the calibration strip.

26. The method of claim 25 wherein step (d) is carried out by initially depositing only a portion of the timing strip by leaving at least one terminal gap between the starting point and discharge point of the timing strip, and closing the terminal gap or gaps in the timing strip with a bridging strip to provide a continuous timing strip from the starting point to the discharge point, the bridging strip being configured to provide the timing strip with an effective length which, at the burn rate ascertained for the calibration strip, will provide a desired delay period for the delay unit.

27. The method of claim 25 wherein step (d) is carried out by providing one or more jump gaps in the timing strip.

28. The method of claim 25 wherein step (d) is carried out by applying one or more accelerants to the timing strip.

29. The method of claim 25 wherein step (d) is carried out by applying one or more retardants to the timing strip.

30. The method of claim 25 wherein the delay unit further comprises at least one of (a) a pick-up charge in signal transfer communication with the starting point of the timing strip, and (b) a relay charge in signal transfer communication with the discharge point of the timing strip, and step (d) is carried out by covering a portion only of the timing strip by at least one of the charges whereby the effective length of the timing strip is the length of the timing strip left uncovered by the charge or charges.

31. The method of claim 30 further comprising covering one portion of the timing strip with the pick-up charge and another portion of the timing strip, with the relay charge to establish the effective length of the timing strip by the length of the timing strip between the pick-up and relay charges which is not covered by the charges.

32. The method of claim 25 or claim 26 wherein the energetic material comprises nanosize particles.

33. The method of claim 25 or claim 26 wherein the energetic material is comprised of at least one discrete layer of fuel and at least one discrete layer of oxidizer, the layer of fuel and the layer of oxidizer being in contact with each other.

34. The method of claim 25 or claim 26 including depositing the timing strip and the calibration strip onto the same substrate.

35. The method of claim 25 or claim 26 including depositing the timing strip and the calibration strip on respective separate substrates.

36. The method of claim 25 or claim 26 wherein the energetic material comprises nanosize particles of fuel M′

and oxidant MyOx wherein M′ and

M are the same or different metals and y and x may be the same or different positive integers 1, 2, 3 . . . n.

37. The method of claim 36 wherein M and M′

are selected from one or more of Ag, Al, B, Cu, Hf, Si, Sn, Ta, W, Y and Zr.

38. The method of claim 36 wherein M′

and M are selected from one or more of Al, Cu and Ag.

39. The method of claim 36 wherein M is titanium, y=1 and x=2.