Closing screw for a projectile
The locking screw with a pressure relief channel and closure element addresses internal pressure issues in projectiles by controlled failure at a defined limit, enhancing safety and reliability.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- RHEINMETALL WAFFE MUNITION GMBH
- Filing Date
- 2025-11-20
- Publication Date
- 2026-06-18
AI Technical Summary
Existing locking screws for projectiles, such as high-explosive shells, fail to effectively manage internal pressure increases due to external thermal influences without causing complex reactions or structural instability, posing safety hazards.
A locking screw with a pressure relief channel and a closure element that fails at a defined pressure limit, allowing controlled pressure release through the channel, designed to withstand mechanical stress and temperature changes.
The solution provides robust and reliable pressure relief without affecting projectile performance, ensuring safety by preventing catastrophic failures and reducing hazards.
Smart Images
Figure EP2025083702_18062026_PF_FP_ABST
Abstract
Description
[0001] Applicant:
[0002] Rheinmetall Waffe Munition GmbH Heinrich-Ehrhardt-Straße 2 29345 Südheide
[0003] General Power of Attorney: 723130.1
[0004] 30800065WO 20.11.2025
[0005] ELL / MAY
[0006] Title: Locking screw for a projectile
[0007] Description
[0008] The present invention relates to a locking screw having the features of the preamble of claim 1. Furthermore, the invention relates to a projectile having the features of the dependent claim.
[0009] Locking screws for projectiles, including projectiles of the type mentioned above, are known from the prior art. Such projectiles are used, for example, as high-explosive shells in artillery. For safety reasons, these projectiles are usually delivered unfuzed (without a nose fuse) and stored, for example, in military depots. For ease of handling, such projectiles are often equipped with a locking screw or a lever-type locking screw.
[0010] Such projectiles are subject to external influences during transport and storage, such as vibrations, temperature changes, or, in extreme cases, fire or gunfire. A key safety requirement is therefore a low reactivity or minimal damage caused by these (unprimed) projectiles. If, for example, a high level of thermal energy is applied to a projectile from the outside due to a fire, the internal pressure in the projectile casing increases as a result of the rising temperature. The rising temperature initiates the decomposition of the explosives, which, accelerated by the high internal pressure, can, in extreme cases, lead to the decomposition of the explosives inside the projectile (deflagration to detonation). Independently of this, the increasing internal pressure increases the prestress acting on the projectile casing, so that the casing can fail if its strength limits are exceeded, potentially leading to...Large amounts of energy are transferred to fragments of the projectile casing and its surroundings. This poses a potential hazard to people and property in the vicinity of the projectile.
[0011] In the prior art, various measures have been implemented to achieve pressure relief in the event of an increase in the internal pressure of the projectile (e.g., due to external thermal influences). For example, Fenbart US 2017 / 016705 describes a locking screw in which a pressure relief valve is held by a screw, with an explosive material located in the threaded bore for the screw. This explosive material reacts upon external thermal influence and shears off the screw, allowing the pressure relief valve to open. This design is quite complex, and the reaction of the explosive material may potentially lead to further reactions, for example, of other ammunition.
[0012] US 10,378,870 Bl further discloses a sealing screw with a corrugated metal ring, made of plastic, designed to melt in case of fire, thus allowing the projectile to vent. US 3,927,791 Al discloses a sealing screw with a channel containing a fusible bismuth alloy (low melting point). Similarly, versions using wax instead of a bismuth alloy are known from the prior art. Such sealing screws with fusible links are sometimes complex in design and expensive to manufacture. Furthermore, these sealing screws with fusible links often exhibit insufficient stability. Additionally, some sealing screws with fusible links cannot withstand storage at temperatures of 71 °C and above followed by mechanical stress (e.g., a drop test).
[0013] The invention is based on the objective of enabling pressure relief of any internal pressure that may prevail in the shell of a projectile using simple design means. It is desirable that this does not negatively affect the performance of the projectile.
[0014] The invention solves this problem by means of a locking screw with the features of claim 1. The locking screw is designed and / or intended for a projectile, in particular for an explosive projectile with a head detonator receptacle.
[0015] The sealing screw has a screw body extending along a central longitudinal axis. A channel (pressure relief channel) is formed within the screw body, extending along the central longitudinal axis from a first side of the screw body (inside or rear) to a second side of the screw body (outside or front). In other words, the channel opens into the screw body at the first side and exits the screw body at the second side. The channel thus extends along the central longitudinal axis through the screw body.
[0016] A closure element (pressure relief element) is arranged in the channel, which closes the channel. The closure element is designed and / or configured such that, when a defined limit pressure prevailing in the channel is exceeded (pressure-related), the closure element at least partially fails or collapses and consequently at least partially releases the channel.
[0017] In other words, the closure element is configured and / or designed such that it blocks or closes the channel up to a defined limit pressure (acting on the channel, particularly from the first side) and, if this limit pressure is exceeded, at least partially fails or collapses, thereby releasing the channel. The closure element is designed such that it at least partially collapses when the limit pressure is exceeded.
[0018] With the proposed sealing screw, in the event of a pressure build-up on the first side of the screw body (thus, in the installed state, inside the shell casing), the failure of a sealing element in the center of the screw at least partially releases the channel in the screw body. In other words, the failure of the sealing element creates a pressure relief channel. The controlled failure of the relief element is achieved by exceeding a defined internal pressure (to be determined during the design process) within the shell casing. This distinguishes the proposed sealing screw from the known solutions with heat-locking devices described above, where failure occurs due to temperature. For example, a pressure increase resulting from cold deformation of the shell casing cannot be adequately addressed by heat-locking solutions.However, this is possible with the proposed sealing screw, since failure occurs depending on the pressure, namely when a defined pressure limit or limit pressure is exceeded.
[0019] In a preferred embodiment, the closure element can have a retaining section and a closure section, wherein the closure element is configured such that, upon exceeding the limit pressure, the closure section at least partially detaches from the retaining section or at least partially fails or collapses. This contributes to a robust design, as the different functions (retaining and failure) are performed by different sections. The closure section thus fails or deforms in such a way that the channel is at least partially released, e.g., by shearing or bursting of the closure section. The retaining section can have a sleeve-shaped form. The closure section can have a disc-shaped form. Optionally, a tool-engaging section for mounting the closure element can be provided on the closure element.The tool gripping section can be formed on the inside of the retaining section or project rearward (towards the first side) from the closure section. In the assembled state, the closure element is inserted into the channel together with the retaining section.
[0020] Advantageously, the channel can have a section with a profiled inner contour, and the retaining section of the closure element has a corresponding profiled outer contour. This contributes to a secure coupling of the closure element in the channel, as the profiles are in engagement with each other. For example, the inner and outer contours can each have grooves, which are oriented circumferentially.
[0021] Specifically, the channel can have a section with an internal thread, while the retaining section of the closure element has a corresponding external thread. This contributes to a structurally simple and secure fastening of the closure element in the channel. The closure element can thus be screwed into the internal thread in the channel using the external thread formed on the retaining section. Advantageously, a (radially) inwardly projecting shoulder can be formed on or in the channel, against which the closure element rests when installed. The shoulder forms a mechanical stop. This can indicate that the closure element is fully screwed in. Furthermore, it can create a counter-bearing that holds the retaining section in place, preventing the closure section from breaking or collapsing at that point.Depending on the design, the locking element can rest against the shoulder with a front end of the retaining section (in the screwing direction) or with a collar projecting outwards (radially) from the retaining or locking section. The collar can also protrude from the locking element at a rear end (in the screwing direction).
[0022] Specifically, the screw body may have an eyelet section, a bracket, or a dome on the second side. The eyelet section or bracket is designed and / or intended for coupling with a lifting device, such as a load hook or crane hook. In other words, the locking screw can be designed as a lifting ring locking screw.
[0023] Advantageously, an external thread can be formed on the screw body towards the first side, adjacent to which is a recess in which a sealing ring is arranged. This ensures a reliable seal against the front opening (mouth hole) when the sealing screw is mounted on the projectile. The sealing ring can be an O-ring. In a specific embodiment, the sealing element can be made of metal. This contributes to a robust design with low weight.
[0024] Alternatively, the sealing element can be made of plastic. This also allows the channel in the screw body to be reliably sealed, and such a screw body is comparatively corrosion-resistant.
[0025] The aforementioned problem is also solved by a projectile with the features of the dependent claim. Regarding the advantages achievable thereby, reference is made to the relevant explanations concerning the locking screw.
[0026] The projectile has a casing that extends along a central longitudinal axis and features a front with a front opening (mouth hole). The projectile also has a sealing screw with one or more of the aspects described above. The front opening can be closed or is closed by means of the sealing screw. For this purpose, the projectile casing has an internal thread at the front opening that corresponds to the external thread of the screw body.
[0027] The projectile can be a high-explosive projectile with a nose fuse receptacle. The projectile can have a caliber of 105 mm, 152 mm, or 155 mm (millimeters). A primary charge, in particular an explosive charge (pressed or cast), can be arranged within the projectile casing as the payload. One or more booster charges for initiating the primary charge can also be arranged within the projectile casing.
[0028] The projectile casing may have a rear (base-side) opening in the direction of fire, to which the casing is provided with an internal thread. A projectile base may be provided, which has an external thread corresponding to the internal thread. The projectile base can be screwed into the opening and, when screwed in, closes the opening of the projectile casing.
[0029] The measures discussed above and / or those described below can be used to further develop the floor.
[0030] The invention is explained in more detail below with reference to the figures, wherein identical or functionally identical elements are provided with identical reference numerals, possibly only once. The figures show:
[0031] Fig. 1 shows a design form of a projectile in a longitudinal section;
[0032] Fig. 2 shows an embodiment of the locking screw of the projectile from Figure 1 in a perspective exploded view;
[0033] Fig. 3 shows the locking screw from Figure 2 in its assembled state in a longitudinal section; Fig. 4 shows a further embodiment of the locking screw of the projectile from Figure 1 in a perspective exploded view;
[0034] Fig. 5 shows the locking element of the locking screw from Figure 4 in a longitudinal section; and
[0035] Fig. 6 shows one possible embodiment of the locking screw from Figures 4 and 5.
[0036] Figure 1 shows a longitudinal section of a design form of a projectile, the projectile as a whole being designated by the reference sign 10.
[0037] The projectile 100 has a projectile casing 102 that extends along a central longitudinal axis ML and has a projectile front 104 (projectile tip) (at the front in the direction of fire S). The projectile casing 102 defines an interior projectile space 106 and is rotationally symmetrical in this example.
[0038] The projectile casing 102 tapers towards the projectile front 104. A front opening 108 (mouth) is formed at the projectile front 104, which is closed by means of a locking screw 10. In this example, the locking screw 10 has a lug section 12, over which the projectile 100 can be handled. In other words, the locking screw 10 is designed as a lever-type locking screw.
[0039] Guide and / or sealing rings 110 are arranged in the rear section of the projectile casing 102. A projectile tail section 112 is provided on the side facing away from the projectile front 104, which is screwed to the projectile casing 102. The projectile tail section 112 forms a projectile tail. Optionally, the projectile tail section 112 can have an (integrated) gas generator 114 (shown here only schematically).
[0040] The projectile casing 102 has an opening 116 along its central longitudinal axis ML, facing away from the projectile front 104 (at the rear in the direction of fire S), at which the projectile casing 102 is provided with an internal thread 118. At the rear of the internal thread 118 (at the rear in the direction of fire S), a further internal thread 120 is provided for attaching the projectile tail section 112.
[0041] A projectile base insert 122 is provided, which has an external thread 124 that corresponds to the internal thread 118 of the projectile casing 102. The projectile base insert 122 is screwed into the internal thread 118 and closes the opening 116. Inside the projectile casing 102, a main charge, e.g., an explosive charge, and one or more booster charges for initiating the explosive charge can be arranged (not shown).
[0042] A first embodiment of the locking screw 10 of the projectile 100 is described with reference to Figures 2 and 3.
[0043] The locking screw 10 has a screw body 14 extending along a central longitudinal axis M. A channel 16 is formed in the screw body 14, extending with respect to the central longitudinal axis from a first side 18 of the screw body 14 (rear) to a second side 20 of the screw body 14 (front). The channel 16 thus extends along the central longitudinal axis M through the screw body 14.
[0044] A closure element 22 is arranged in the channel 16 (see Figure 3), which closes the channel 16. The closure element 22 is designed and / or configured such that, when a defined limit pressure prevailing in the channel 16 is exceeded (see arrows 24 in Figure 3), the closure element 22 at least partially fails or collapses due to pressure and consequently at least partially releases the channel 16.
[0045] The closure element 22 has a retaining section 26 and a closure section 28. The closure element 22 is designed such that, when the limit pressure is exceeded, the closure section 28 at least partially detaches from the retaining section 26 or at least partially fails or collapses.
[0046] The retaining section 26 has a sleeve-shaped form. The locking section 28 has a disc-shaped form. In the installed position, the retaining section 26 faces the second side 20 and the locking section 28 faces the first side 18 (locking section 28 is located behind the retaining section 26).
[0047] In this example, a tool grip section 30 for mounting the locking element 22 is formed on the locking element 22. The tool grip section 30 projects rearward (toward the first side) from the locking element 28. In this case, the tool grip section 30 is formed by several pin sections 32 that are mechanically connected to the locking element 28, for example, four pin sections 32. The pin sections 32 define, by way of example, a cross recess on the inside and a hexagon on the outside.
[0048] The channel 16 has a section with an internal thread 34, and the retaining section 26 of the closure element 22 has a corresponding external thread 36. Thus, the closure element 22 can be screwed into the internal thread 34 in the channel 16 and fastened with the external thread 36 formed on the retaining section 26.
[0049] A radially inwardly projecting shoulder 38 is formed on or in the channel 16, against which the locking element 22 rests in the assembled state (see Figure 3). The locking element 22 rests against the shoulder 38 with a (radially) outwardly projecting collar 40. The collar 40 is formed at the rear end of the locking element 22 in the screw-in direction.
[0050] The screw body 14 has an external thread 42 on the first side 18, adjacent to which is a relief groove 44 in which a sealing ring 46 is arranged, e.g. an O-ring. Separately, the sealing element 10 in the example is made of plastic (plastic insert or plastic plug).
[0051] The present sealing screw 10 functions as follows: The sealing screw 10 is equipped with the sealing element 22 and a sealing ring 46. When the sealing screw 10 is screwed into the front opening 108, the sealing ring 46 seals the interior of the floor 106 against external influences such as moisture. The sealing element 22 is screwed into the internal thread 34 in the channel 16 via the external thread 36.
[0052] If the shear strength of the plastic locking screw 10 (see area of the shear bands B in Figure 3) is exceeded by the applied pressure or internal projectile pressure (see arrows 24 in Figure 3), the locking section 28 is sheared off from the retaining section 26.
[0053] At the center of the sealing screw 10, the channel 16 is at least partially opened, so that a pressure relief channel is formed. The pressure in the interior of the floor 106 is reduced by expansion and / or escape of the reaction products in the form of gases and the energetic materials towards the channel 16 or the pressure relief channel forming therein.
[0054] A further embodiment of the locking screw 10 of the projectile 100 is described with reference to Figures 4 and 5.
[0055] The present locking screw 10 corresponds in its design to the locking screw 10 described with reference to Figures 2 and 3, so that reference is made to the explanations there to avoid repetition.
[0056] In contrast, the present closure element 22 is made of metal. The closure element 22 is arranged in the channel 16 when assembled and closes the
[0057] Channel 16. The closure element 22 is designed and / or configured such that, when a defined limit pressure prevailing in channel 16 is exceeded, the closure element 22 at least partially fails or collapses due to pressure and consequently at least partially releases the channel 16.
[0058] The closure element 22 has a sleeve-shaped retaining section 26 and a disc-shaped closure section 28. The closure element 22 is designed such that, upon exceeding the limit pressure, the closure section 28 at least partially detaches from the retaining section 26 or at least partially fails or collapses. In the installed position, the closure section 28 faces the second side 20 (closing section 28 is located at the front end of the retaining section 26). In the example, the closure section 28 is designed as a rupture surface.
[0059] In this example, a tool grip section 30 for mounting the locking element 22 is formed on the locking element 22. The tool grip section 30 is formed on the inside of the retaining section 26 and is shown here by way of example in the form of two opposing grooves 31.
[0060] The present closure element 22 has an external thread 36 in the retaining section 26, with which the closure element 22 can be screwed into the internal thread 34 in the channel 16 and fastened (internal thread 34 see Figure 3). The present closure screw 10 functions as follows:
[0061] As explained, the sealing screw 10 is equipped with a metallic sealing element or relief element 22, which can also be referred to as a "burst insert". The metallic sealing element 22 can be screwed into the channel 16 of the sealing screw 10.
[0062] When the permissible strength of the closure element 22 is exceeded, the closure section 28 or the bursting surface tears open and allows chamfers and energy-carrying materials to escape from the interior of the floor 106.
[0063] Figure 6 shows one possible design of the locking screw 10 from Figures 4 and 5.
[0064] The present locking screw 10 largely corresponds in its design to the locking screw 10 described with reference to Figures 4 and 5, so that, to avoid repetition, reference is made to the descriptions therein. The locking element 22 corresponds in its design to the locking element 22 described with reference to Figures 4 and 5, so that reference is also made to the above descriptions in this respect.
[0065] In contrast, the locking screw 10 does not have an eyelet section 12 but a dome 13 in which relief pockets 15 are formed.
[0066] The function of this locking screw 10 is analogous to that of the locking screws 10 described above. The locking element 22 used is independent of whether the locking screw 10 is designed with eyelet section 12 or dome 13.
Claims
Patent claims 1. A locking screw (10) for a projectile (100) with a screw body (14) extending along a central longitudinal axis (M), wherein a channel (16) is formed in the screw body (14) which extends with respect to the central longitudinal axis (M) from a first side (18) of the screw body (14) to a second side (20) of the screw body (14), characterized in that a locking element (22) is arranged in the channel (16) which closes the channel (16) and is configured such that the locking element (22) fails at least partially when a defined limit pressure prevailing in the channel (16) is exceeded and at least partially releases the channel (16).
2. Sealing screw (10) according to claim 1, characterized in that the sealing element (22) has a retaining section (26) and a sealing section (28), wherein the sealing element (22) is arranged such that the sealing section (28) detaches at least partially from the retaining section (26) or fails at least section by section when the limit pressure is exceeded.
3. Sealing screw (10) according to claim 2, characterized in that the channel (16) has a section with a profiled inner contour, wherein the retaining section (26) of the sealing element (22) has a corresponding profiled outer contour.
4. Sealing screw (10) according to claim 2, characterized in that the channel (16) has a section with an internal thread (34), wherein the retaining section (26) of the sealing element (22) has a corresponding external thread (36).
5. Sealing screw (10) according to one of the preceding claims, characterized in that on or in the channel (16) an inwardly projecting shoulder (38) is formed against which the locking element (22) rests in the assembled state.
6. Locking screw (10) according to one of the preceding claims, characterized in that an eyelet section (12) or a dome (13) is formed on the screw body (14) towards the second side (20).
7. Sealing screw (10) according to one of the preceding claims, characterized in that an external thread (42) is formed on the screw body (14) towards the first side (18), to which a relief groove (44) adjoins, in which a sealing ring (46) is arranged.
8. Locking screw (10) according to one of the preceding claims, characterized in that the locking element (22) is made of metal.
9. Sealing screw (10) according to one of claims 1 to 7, characterized in that the sealing element (22) is made of plastic. 10th projectile (100) , with a projectile casing (102) extending along a central longitudinal axis (ML) and comprising a projectile front (104) with a front opening (108) comprising, and with a locking screw (10) according to one of the preceding claims, wherein the The front opening (108) can be closed or sealed by means of the locking screw (10).