DELAY UNIT FOR A PROJECTILE

Abstract

The invention relates to a method of delaying a mechanism in a firearm and a delay unit for a projectile comprising i) a first and a second pressure chamber (3a, 3b) arranged to receive combustion gases in a firearm via at least one inlet (1a, 1b) arranged to each of said first and second pressure chambers (3a, 3b) following firing of a projectile ii) at least one outlet for transferring the combustion gases (4a, 4b), arranged to each of said first and second pressure chambers (3a, 3b), to a piston chamber in which a displaceable piston (6) is arranged dividing the piston chamber into a compartment (5b) having a volume V.sub.1 upstream the piston (6) and a compartment (5a) having a volume V.sub.2 downstream the piston (6), wherein said at least one outlet (4a, 4b) from the first and second pressure chambers (3a, 3b) are arranged to transfer said combustion gases to said compartments (5a, b) of said piston chamber to provide an overall pressure difference between compartments (5a) and (5b) pressing the piston (6) at an initial idle position downstream whereby the volume V.sub.2 of compartment (5a) is reduced and whereby the piston (6) being pressed downstream towards an end position actuates a function at a predetermined point in time following firing of a firearm.

Claims

1-16. (canceled)

17. Delay unit for a projectile, the delay unit comprising: a first and a second pressure chamber (3a, 3b) each configured to receive combustion gases in a firearm via at least one inlet (1a, 1b) arranged to each of said first and second pressure chambers (3a, 3b) following firing of a projectile; and at least one outlet for transferring the combustion gases (4a, 4b), arranged to each of said first and second pressure chambers (3a, 3b), to a piston chamber in which a displaceable piston (6) is arranged dividing the piston chamber into a compartment (5b) having a volume V.sub.1 upstream the piston (6) and a compartment (5a) having a volume V.sub.2 downstream the piston (6), wherein: the outlets (4a, 4b) from the first and second pressure chambers (3a, 3b) are configured to transfer said combustion gases to said compartments (5a, 5b) of said piston chamber to provide an overall pressure difference between compartments (5a) and (5b) pressing the piston (6) at an initial idle position downstream, whereby the volume V.sub.2 of compartment (5a) is reduced, and whereby the piston (6) being pressed downstream towards an end position actuates a function at a predetermined point in time following firing of the firearm.

18. Delay unit according to claim 17, wherein a resilient means is configured to maintain the piston (6) immovable at an initial idle position prior to establishing a pressure difference between compartments (5a, 5b).

19. Delay unit according to claim 17, wherein the piston (6) in said initial idle position is configured to block flow of combustion gases from the piston chamber via an opening (8) between the piston chamber and a sub-chamber (9).

20. Delay unit according to claim 19, wherein the sub-chamber (9) is provided with a displaceable sub-chamber piston (10) configured to be displaced from an initial idle position when exposed to flow of combustion gases originating from the piston chamber.

21. Delay unit according to claim 17, wherein said inlets of the first and second pressure chambers (3a, 3b) each have an area ranging from 0.1 to 50 mm.sup.2.

22. Delay unit according to claim 17, wherein at least one outlet is arranged to at least one of said first and/or second pressure chambers (3a, 3b) for evacuating a predetermined portion of said combustion gases outside of the delay unit.

23. Delay unit according to claim 17, wherein the outlets for transferring combustion gases (4a, 4b) to the piston chamber are arranged at the opposite side of the pressure chambers relative to the inlets (1a, 1b).

24. Delay unit according to claim 17, wherein the piston (6) is configured to be displaced from an initial idle position downstream to an end position such that an opening (8) between the piston chamber and a sub-chamber (9) is unblocked.

25. Delay unit according to claim 17, wherein: a sub-chamber piston (10) is configured to break a short circuit comprising a piezoelectric sensor following actuation of the sub-chamber piston (10), the sub-chamber piston (10) is configured to be actuated by the combustion gases which flows into the sub-chamber as the opening (8) is unblocked, and as the combustion gases enter the sub-chamber, the sub-chamber piston is configured to be pressed downstream from its initial position to an end position in analogy with the piston (6) of the piston chamber.

26. Delay unit according to claim 22, wherein the outlet for evacuating combustion gases has a length ranging from 1 to 50 mm.

27. Delay unit according to claim 17, wherein the outlet of each pressure chamber (4a, 4b) for transferring combustion gases has an area ranging from 0.5 to 50 mm.sup.2.

28. Delay unit according to claim 17, wherein a fuse is connected to the delay unit.

29. Delay unit according to claim 17, wherein a piezoelectric sensor is connected to the delay unit.

30. Delay unit according to claim 25, wherein the sub-chamber piston (10) is configured to break a short circuit comprising a piezoelectric crystal following actuation of the sub-chamber piston (10).

31. Method of delaying a mechanism for a projectile in a firearm comprising a delay unit according to claim 17, the method comprising the steps of: receiving combustion gases by a first and a second pressure chamber (3a, 3b) in a firearm via at least one inlet (1a, 1b) arranged to each of said first and second pressure chamber (3a, 3b) following firing of a projectile, and transferring the combustion gases by at least one outlet (4a, 4b), the at least one outlet being arranged to each of said first and second pressure chambers (3a, 3b), to a piston chamber in which a displaceable piston (6) is arranged dividing the piston chamber into a compartment (5b) having a volume V.sub.1 upstream the piston (6) and a compartment (5a) having a volume V.sub.2 downstream the piston (6), wherein the outlets (4a, 4b) from the first and second pressure chambers (3a, 3b) are arranged to transfer said combustion gases to said compartments (5a, 5b) of said piston chamber to provide an overall pressure difference between compartments (5a) and (5b) pressing the piston (6) at an initial idle position downstream whereby the volume V.sub.2 of compartment (5a) is reduced and whereby the piston (6) being pressed downstream towards an end position actuates a function at a predetermined point in time following firing of the firearm.

32. Use of a delay unit according to claim 17 for delaying premature detonation of a warhead.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 discloses an overview comprising a delay unit positioned in a round (projectile) of a firearm and how combustion gases enter the delay unit. FIG. 2 discloses a delay unit comprising a piston chamber in which piston 6 is positioned in an initial idle position before firing. FIG. 3 discloses a delay unit in which piston 6 has been displaced from its initial position. FIG. 4 discloses a delay unit in which piston 6 has reached its end position.

DETAILED DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1 shows a delay unit 11 mounted in a round 12. The black strip 13 represents a short circuit which, subsequent to actuation and displacement of a subchamber piston 10, is broken after a predetermined period of time (the delay unit is dimensioned to result in a predetermined delay). By breaking the short circuit, arming for subsequent detonation of a warhead (not shown) may be initiated. An SAI (Safety/Arming/Initiation) unit 14 is arranged adjacent to the delay unit 11, i.e. behind the delay unit 11 in the firing direction. Illustrated lines 15 show the flow of combustion gases originating from combusted propellant (not shown on the left-hand side of the delay unit in FIG. 1). Combustion gases flow into the inlet channels 1a, 1b of the pressure chambers 3a, 3b of the delay unit 11 whereby a pressure is accumulated therein.

[0047] FIG. 2 shows a delay unit comprising two pressure chambers (3a, 3b) having predetermined volumes.

[0048] According to one embodiment of the invention, which applies generally and not only in association with FIG. 2, the outlets from the pressure chambers (3a, 3b) may have a volume ranging from 0.1 to 50, preferably from 1 to 10, most preferably from 1 to 5 mm.sup.3. According to one embodiment, the area of the outlets from the pressure chambers (3a, 3b) may range from 1 to 10, preferably from 1 to 5, most preferably from 1 to 2 mm.sup.2. According to one embodiment, the length of the outlets from the pressure chambers (3a, 3b) may range from 1 to 10, preferably from 1 to 5, most preferably from 2 to 3 mm.

[0049] As a projectile is fired (not shown), combustion gases flow into inlet channels 1a, 1b whereby a pressure is accumulated in pressure chambers 3a, 3b whereby an overpressure is obtained in each of the pressure chambers 3a, 3b. As combustion gases enter the inlet channels 1a, 1b, back valves 2 in each of the channels 1a, 1b allow combustion gases to enter while safeguarding no combustion gases leak out via the inlet channels 1a, 1b.

[0050] The chambers 3a, 3b are provided with outlet channels 4a, b through which combustion gases are transferred to a piston chamber divided into two compartments 5a and 5b by a piston 6 arranged in the piston chamber. The piston 6 has a first area facing the compartment 5a. The piston 6 has a second area facing a compartment 5b (below compartment 5a in FIG. 2). The piston 6 thus separates the piston chamber into two compartments. The spring 7 safeguards the piston is maintained in an initial idle position. As can be noted in FIG. 2, an opening (outlet) is arranged between the piston chamber and a subchamber 9. By maintaining the piston 6 in its initial idle position before any gas enters compartment 5b, piston 6 ensures there is no gas leaking out of the piston chamber via outlet channel 8 to the subchamber 9 provided with a subchamber piston 10. As a pressure difference arises in the piston chamber following firing as combustion gases flow into the pressure chambers 3a, 3b, and transferred to the piston chamber, the piston 6 will be displaced from an initial idle position in FIG. 2 to an intermediate position as further shown in FIG. 3. The piston 6 is displaced downstream such that the spring 7 is compressed. The arising pressure difference forces the piston 6 downstream by providing a higher pressure in compartment 5b than in compartment 5a. Hence, the piston 6 will be brought into motion due to the pressure difference. A low pressure difference, for example a somewhat higher pressure in compartment 5b than 5a will result in a relatively slow motion of the piston 6 whereas a higher pressure difference imparts a quicker displacement of piston 6. It goes without saying the skilled person can design suitable areas of e.g. inlets 1a, 1b as well as outlets 4a, 4b to dimension the delay unit depending on the requirements and use thereof.

[0051] For example, the dimensioning of an evacuation hole may be used to establish a pressure difference in the pressure chambers which in turn may be used to establish a pressure difference in the piston chamber.

[0052] Various parameters may be varied to provide a pressure difference over the piston 6 and thus control the delay unit 11. Provision of an evacuation channel (not shown) positioned on the same side as the inlet channel 1a is one option to reduce the accumulated pressure in pressure chamber 3a and eventually the pressure in compartments 5a and 5b to allow for displacement of piston 6 (upwards in FIGS. 2-4). The evacuation channel may be designed with a diameter and length resulting in a suitable pressure difference in compartments 5a and 5b. The higher the pressure difference over the piston 6, the faster the displacement of the piston 6, and, the faster the combustion gases will flow into subchamber 9 as a consequence of the displacement of piston 6 unblocking opening 8. As the opening 8 is unblocked, the combustion gases will flow into subchamber 9 and actuate subchamber piston 10 which is pressed to the left in the figures (cf. FIGS. 3 and 4). According to a preferred embodiment, subchamber piston 10 is maintained in an initial idle position prior to actuation thereof, e.g. by means of a resilient means such as a spring. As combustion gases enter the subchamber, the subchamber piston will be pressed downstream from its initial position to an end position in analogy with the piston 6 of the piston chamber. As the subchamber piston 10 reaches an end position, various mechanisms may be actuated, for example the breaking of a short circuit 13 as illustrated in FIG. 1. Subchamber piston 10 may also control any other delay mechanism needed subsequent to firing of a projectile. The pressure difference over the piston 6 may be precisely monitored to provide for a very precise predetermined delay. This in turn renders the displacement of the subchamber piston 10 very precise too. An intermediate position of pistons 6 and 10 is shown in FIG. 3 and end positions of pistons 6 and 10 are shown in FIG. 4. FIG. 3 thus shows an intermediate position of piston 6 displaced such that opening 8 of the outlet to subchamber 9 has become partially opened whereby combustion gases present in piston compartment 5b enters subchamber 9. As combustion gases enter the subchamber 9, the subchamber piston 10 will thus displace as shown in FIG. 3 wherein subchamber piston 10 divides the subchamber 9 into compartments 9a, 9b as shown in FIG. 3. In FIG. 4, piston 6 and subchamber piston 10 have been further displaced to their respective end positions. Piston 6 has pressed the spring 7 to its end position whereby piston 6 has reached it end position. As the subchamber piston 10 reaches its end position, an actuation mechanism may be initiated such as the pressing of a copper bushing (initially positioned close to the subchamber wall) through the subchamber wall whereby a short circuit is broken resulting in arming of e.g. a fuze.