A sealing plug

Abstract

A sealing plug comprises a rod (200) and a sleeve (12) combination, wherein the rod is designed to have an outer tapered portion (50) so that when the sealing plug is installed by a setting tool, the sleeve material flows into the gap (52) between the sleeve (12) and the tapered portion (50) to help lock the sleeve and the rod together. In addition, the tool nozzle (30) has a conical tapered portion, which is designed to cause the sleeve (12) material to first flow radially outward when installed to achieve locking of the plug in the blind hole (34) in which it is installed.

Description

Technical Field

[0001] The present invention relates to sealing plugs for use in blind installation environments and particularly, but not exclusively, to threadless plugs that can be used in hydraulic fluid sealing and flow control applications. The present invention also relates to installation tools for use with these blind sealing plugs and methods of application of such plugs. Blind installation means that the hole into which the sealing plug is to be inserted (and for which a fluid-tight seal is to be provided) can be accessed from only one side. Background Art

[0002] Blind sealing plugs generally operate on the principle of radial expansion of the material within the blind hole. The radial expansion of the plug blocks the hole, thereby preventing fluid from flowing through the sealed plug. There are generally two types of expansion actuation: push and pull. In each case, a relatively harder material than the material expanding in the hole is used to cause the relatively soft expanding material to flow radially outward in the hole. With the push method, the pusher is sometimes removed from the hole after the plug has been set; while for the pull method, the puller is captured in the hole after setting. This generally means that the puller has some form of structural weakness formed therein so that it breaks under a defined load, thereby separating the puller from the part that actuates it, thereby leaving the plug in the hole.

[0003] An example of a known pull-type sealing plug is disclosed in EP-A-1,440,272. This document discloses a form of sealing plug which consists of a sleeve held around a rod. The rod has a head formed of a relatively harder material than the material of the sleeve. The head is provided with an annular projection for penetrating into the sleeve material when the plug is set in a blind hole. The annular projection, once set in the sleeve, provides a fluid seal between the head of the plug and the sleeve when set in the hole.

[0004] Although this type of sealing plug functions effectively, it has been found that its construction can be improved to provide a plug whose characteristics for setting in a blind hole are more controlled so that a progressive hole filling action is achieved by deforming the sleeve and there is no tendency for the sleeve to move axially within the hole during setting, as is possible with known sealing plugs. This also allows for better containment of the sleeve material, since it will be pressed against the hole surface during setting and will therefore be able to resist very high pressures, such as oil in excess of 1600 bar, without the seal popping out of the hole. Summary of the invention

[0005] The object of the present invention is to provide a sealing plug which overcomes these drawbacks and provides a rod which is better retained in the sleeve both during and after the setting operation.

[0006] Therefore, the present invention provides in one aspect thereof a sealing plug for blind installation in a suitable hole so as to plug and seal the hole, the sealing plug comprising:

[0007] a generally cylindrical hollow sleeve defining a first axis and having a given outer diameter;

[0008] a rod comprising a proximal cylindrical protrusion, a distal head, and a central portion between the proximal cylindrical protrusion and the distal head, the rod head having an outer diameter greater than an outer diameter of the central portion, and wherein the outer diameter of the central portion is greater than an outer diameter of the proximal cylindrical protrusion of the rod, and wherein the rod defines a second axis;

[0009] The rod head is formed of a material that is harder than the material of the sleeve;

[0010] When the central portion of the rod is in the sleeve, it is arranged to be retained in the sleeve by frictional engagement between the outside of the central portion of the rod and the inside of the sleeve, so that the first axis and the second axis are coaxial; the sealing plug is characterized in that the outer diameter of the central portion of the rod gradually decreases relative to the axis of the rod in a direction from the proximal cylindrical protrusion of the rod to the distal head of the rod until a minimum central portion diameter is reached, at which point the central portion of the rod intersects with the rod head.

[0011] Preferably, the stem head has an annular shoulder adjacent a central portion of the stem, the annular shoulder being inclined at an acute angle relative to a radius of the second axis.This helps control radial flow of sleeve material during setting of the plug.

[0012] In a preferred embodiment, the inclination of the annular shoulder forms a concave area facing the central portion of the stem. This in turn facilitates the flow of material during setting of the sealing plug.

[0013] Preferably, the inclination angle of the shoulder relative to the radius of the second axis is between 5° and 25°, more preferably between 10° and 15°, and more preferably the inclination angle of the shoulder is 14°.

[0014] Advantageously, the rod head is formed with an annular projection facing the central portion of the rod. The annular projection may be in the form of a protruding ring which may be arranged to engage with the hollow sleeve. This provides a better fluid seal between the rod head and the sleeve than without such an annular projection.

[0015] In another aspect, the present invention provides a method of setting a sealing plug as described above and defined in the appended claims.

[0016] Other characteristics of the invention are set forth in the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0018] Figure 1 shows an axial section through the stem of a sealing plug according to the invention;

[0019] Figure 2 Shows Figure 1 Detailed view of the enlarged portion A of FIG.

[0020] Figure 3 shows a section taken through an unset sealing plug according to the present invention;

[0021] Figure 4 Shows Figure 1 Isometric view of the rod;

[0022] Figure 5 Shows Figure 1 Detailed cross section of the club head at the enlarged portion D;

[0023] Figure 6 The complete sealing plug before installation is schematically shown;

[0024] Figure 7 Schematic diagram showing the process of starting to be introduced into the setting tool. Figure 6 Sealing plug;

[0025] Figure 8 The installation of the sealing plug by the setting tool is shown;

[0026] Fig. 9 Shown in cross-sectional detail Figure 8 pictorial diagram;

[0027] Figures 10(a) to 10(d) schematically illustrate sequential stages of installation of a sealing plug according to the present invention;

[0028] Fig.11 shows the sealing plug installed; and

[0029] Fig.12 An alternative club head including an annular protruding ring according to the present invention is shown. DETAILED DESCRIPTION

[0030] First reference Figure 1 and Figure 2As can be seen, the rod 200 according to the present invention includes three main regions: a proximal cylindrical protrusion 2, a central portion 4, and a distal head end 6. The rod 200 can be formed as a single unit, or formed from multiple elements. In this example, the rod is formed as a single unit of heat-treated medium carbon steel. The three regions of the rod each have a different outer diameter. The outer diameter of the head 6 is greater than the outer diameter of the central region 4. The outer diameter of the central region 4 is greater than the outer diameter of the proximal cylindrical protrusion 2. The reasons for these different outer diameters will be explained below. The length of the rod 200 is not important in the present invention. The method of clamping the rod to place the sealing plug of the present invention is also not important.

[0031] The proximal cylindrical projection 2 terminates in an inwardly tapered end 8 so that the rod can be more easily inserted into a setting tool, as will be explained below. In this example, to further assist in setting the plug, the rod carries a series of annular grooves 10 along its axial extent. The annular grooves enable the setting tool to effectively grip and pull the projection 2 during installation of the plug.

[0032] like Figure 3 As shown, the rod 200 is arranged to be located within an outer sleeve 12 formed of a material softer than the material of the rod 200. In this example, the sleeve 12 is formed of annealed aluminum alloy 6061. The sleeve 12 defines an axis AA. The rod 200 defines a second axis BB (see Figure 2 ).

[0033] The sealing plug is formed by the combination of the sleeve 12 and the rod 200, so that the rod 200 is located inside the sleeve 12 and is coaxial with the sleeve 12. Figure 3 In the illustration, for clarity, only axis AA is shown, but a person skilled in the art will appreciate that both axis AA and axis BB are coaxial; in this example axis AA and axis BB are coincident.

[0034] Reference Figure 2 , the structure of the central region 4 can be seen. The central region includes a weakened area 14, which provides a location for the rod to break once a sufficient axial load is applied to the rod during installation of the rod 200 in a known manner. A person skilled in the art can easily understand that the force that causes the rod to break at the weakened area 14 is mainly determined by the radial depth of the weakened area 14.

[0035] The maximum outer diameter of the central region 4 is at 16. The diameter is selected here to be at least the same as the inner diameter of the sleeve 12 so that when the rod 200 is inserted into the sleeve 12, there is an interference fit to hold the rod in place within the sleeve 12. This interference fit ensures that the rod 200 and the sleeve 12 are coaxial and prevent relative axial movement when the assembly is manipulated.

[0036] The tapered area 15 is located between the weakened zone 14 and the maximum diameter 16 of the central region 4. This taper 15 facilitates assembly of the sleeve 12 onto the rod 200. The taper 15 is radially inward from the maximum diameter 16 to the weakened area 14, and the purpose of the taper 15 is to provide a guide that enables the sleeve 12 to be assembled onto the rod 200. This is an assembly aid during the formation of the plug (the combination of the rod 200 and the sleeve 12), and has no effect during the setting of the sealing plug when in use.

[0037] In the case of moving along the axial direction BB from the proximal cylindrical protrusion 2 end of the rod to the distal head 6 end (when observing Figure 2 The outer diameter of the central region 4 tapers radially inwardly at 50 to a minimum diameter point 18 (from right to left when viewed from left to right). The purpose of this taper along the central region 4 will also be described below. An inner shoulder 21 is located between the minimum diameter point 18 and the head 6. The inner shoulder 21 is formed as part of the rod head 6 radially inward of the junction with the minimum diameter position 18. Although the inner shoulder 21 is shown in this example, the inner shoulder is a preferred feature and does not have to be used. As will be appreciated by those skilled in the art, the present invention can function adequately even without such a shoulder 21.

[0038] Now also refer to Figure 5 , it can be seen that the head 6 is formed with an annular shoulder 20 adjacent to the central region 4. In this example, the shoulder 20 abuts against an inner shoulder 21 at the minimum diameter point 18. The shoulder 20 is arranged along a surface 22, which is inclined at an acute angle α relative to the radius RR of the axis BB. The angle α is selected to be in the range of 5° to 20°; preferably in the range of 10° and 15°. In this example, the angle is 14°. Regardless of the angle α, the angle α is selected to ensure that the inclination of the annular shoulder 20 relative to the radius RR forms a concave region facing the central portion 4 of the rod. In this example, the concave region extends at 23 to the outer edge of the shoulder. However, the concave region does not necessarily have to extend completely radially from the central axis BB to the circumferential periphery of the head 6. The concave region can extend only partially between the axial center and the radial periphery, or even in sections between the axial center and the radial periphery (as opposed to a single continuous length). In addition, the surface 20 defining the concave region is not necessarily straight. The purpose of the concave region will be explained below.

[0039] exist Figure 4 An isometric view of rod 200 can be seen in FIG.

[0040] Reference now Figures 6 to 11 , which shows how to Figures 1 to 5 A sealing plug is set in the blind hole 34. In the example shown, the hole 34 is formed in a workpiece 36 (eg, a hydraulic valve block).

[0041] Figure 6 The illustration of shows a complete sealing plug formed by a rod 200 held in a sleeve 12. As described above, the rod 200 is held in the sleeve 12 due to the interference fit between the rod 200 and the sleeve 12 resulting from the selection of the outer diameter 16 of the rod central region 4 and the inner diameter of the sleeve 12.

[0042] It can be seen that the radius R drawn as the outer diameter of the rod head 6 6 Greater than the radius R drawn for the outer diameter of the sleeve 12 12 This is chosen because, when the plug is inserted into the blind hole 34 to be sealed, the sleeve 12 (in this example made of aluminum material which is relatively softer than the steel of the rod) may be damaged by the material forming the hole during the process of inserting the plug into the hole. This is particularly true if the material forming the hole is, for example, steel. By ensuring that R 6 Greater than R 12 , avoiding the risk of sleeve damage. In this example, as shown in the figure numeral 26, R 6 and R 12 The difference between is 0.1 mm, but any suitable difference may be used. Figure 6 As can be seen on the left side, in order to help insert the rod head 6 into the hole (not shown), the end of the head 6 can be rounded 28, or chamfered, so that the head 6 can easily enter and be centered in the hole 34 when inserted.

[0043] Reference now Figure 7 , which shows the proximal cylindrical projection 2 inserted into the nosepiece 400 of a setting tool 600. How such a setting tool 600 operates to set a blind sealing plug will be understood and appreciated by those skilled in the art, and the setting tool 600 will not be described further herein. Suffice it to say that the purpose of the tool 600 is to grip the projection 2 and subsequently apply an axial force to the projection 2, while at the same time holding the sleeve 12 against axial movement of the sleeve 12, so that movement of the head 6 relative to and towards the sleeve 12 occurs. The front face 30 of the nozzle 400 is tapered, and in this example is shown as a convex conical form, as will be explained below.

[0044] Figure 8The projection 2 is shown in a position where it is fully drawn into the tool 600 via the nozzle 400, so that the tapered face 30 abuts against the sleeve 12. Typically, a vacuum advancement mechanism draws the projection 2 into the tool and holds the sleeve 12 against the face 30. The reason for the abutment between the face 30 and the sleeve 12 is to prevent axial movement of this end of the sleeve 12 toward the tool 600 during setting of the plug. The tapered face 30 of the nozzle 400 is arranged to provide a convex conical surface toward the sleeve 12. The angle β formed by the taper relative to the radius R of the rod 200 is between 10° and 20°; preferably between 14° and 16°. In this example, the angle is 15°. This means that a tapered gap 32 is formed between the face 30 and the sleeve 12, the purpose of which will be explained below.

[0045] Reference now Fig. 9 , which shows that the front piece 38 of the tool 600 is formed as an annular shoulder on the nozzle 400 and engages (and contacts) a surface of the workpiece 36 in addition to the tapered surface 30 engaging the sleeve 12 within the bore 34 .

[0046] To set the plug, the tool 600 applies an axial force (towards the Fig. 9 on the right side of the ).

[0047] Reference is now made to Figures 10(a) to 10(d), which illustrate the result of this operation. In Figure 10(a), the slight, initial axial force applied by the tool to the rod 200 is insufficient to move the rod relative to the sleeve 12.

[0048] Once the force applied by the tool 600 to the rod 200 is sufficient to cause relative movement between the rod and the sleeve 12, relative movement between the tool 600 and the workpiece 36 is prevented because the front part 38 of the nozzle 400 of the tool 600 abuts and is positively retained on the workpiece 36. Therefore, the only movement allowed is the movement of the rod 200 within the hole 34 (towards the right side of the figure, as shown by arrow M).

[0049] The result of this movement of the rod 200 is that the rod head 6 is pulled into engagement with the left side of the sleeve 12. The initial contact between the rod head 6 and the sleeve 12 is the contact of the inner shoulder 21. Since the inner shoulder 21 is formed by the material of the rod head 6 (here steel), and since the material of the sleeve 12 is softer than this material (in this example, the sleeve material is aluminum), the protruding outer edge of the shoulder 21 penetrates the end of the sleeve 12. This sleeve penetration is part of the sealing effect. This is the situation shown in Figure 10 (b).

[0050] As shown in Fig. 10(c), when the rod head 6 continues to move due to the axial pulling force of the setting tool 600, the next contact occurs between the annular outer edge 23 of the rod head 6 and the radial outer portion of the sleeve 12. This again causes the rod head 6 to penetrate the sleeve 12, as seen at reference numeral 42. This penetration is also part of the sealing effect.

[0051] Along with the above contact between the rod head 6 and the sleeve 12, the other side of the sleeve 12 (the right side of FIG. 10 ) contacts the tapered surface 30 of the nozzle 400. Again, because the material of the nozzle 400 (in this example, hardened steel) is harder than the material of the sleeve 12, the right side of the sleeve 12 deforms. Due to the convex shape of the tapered surface 30 (as seen through the sleeve 12), the deformation of the sleeve here causes the material flow of the sleeve 12 to start from its radial inner portion 44 (which first contacts the tapered surface 30), and the sleeve material flows (which is plastic flow) in a radially outward direction away from the axis BB. This is shown in FIG. 10 (d).

[0052] It will be appreciated that the first flow of sleeve material caused by the movement of the rod 200 is caused by the shape of the nozzle taper 30. In other words, the radially outward plastic flow of the sleeve 12 material (on the right side of the sleeve 12) is the first flow. The effect of this is to push the sleeve 12 material to flow radially outward to contact the inner surface of the bore 34, thereby preventing any axial movement of the sleeve 12 within the bore 34 at the area marked 35. Any axial sliding of the sleeve within the bore 34 during the setting process (which is known to occur in prior art sealing plug setting operations where deformation of the sleeve occurs first from the distal end of the sleeve) will be avoided because this will compromise the integrity of the finished sealing surface provided at the interface of the sleeve 12 and the bore 34 surface.

[0053] Continued movement of the rod 200 toward the setting tool 600 causes continued flow of sleeve material (which has begun at the right side of the sleeve 12 and progresses from there toward the left side). This hole filling action is due to the sleeve 12 gradually contacting the inner surface of the hole 34 from right to left as the rod head 6 moves from left to right. Since the sleeve 12 is squeezed between the tapered surface 30 and the rod head 6 within the hole 34, the subsequent flow is a radial expansion (radially outward) flow. Since the right end of the sleeve 12 cannot move axially (due to contact with the front face 30 of the nozzle of the setting tool), as the sleeve material reaches and contacts the inner surface of the hole 34 at position 48, the material of the sleeve 12 expands radially to fill the hole 34.

[0054] The final radial movement of the sleeve 12 is to the left in contact with the rod head 6. The radial movement here is radially inwards towards the axis BB due to the taper 50 formed on the central region 4 of the rod from the maximum diameter to its minimum diameter 18. It will be appreciated that since the outside of the sleeve 12 has been in contact with the inside of the hole 34 at both regions 35 and 48, at this stage the sleeve material flows into the gap 52 formed between the taper 50 and the inside of the sleeve 12. This is due to both the taper 50 and the angle α of the shoulder 20 of the rod head. The combined effect of these two features is to force the plastic flow of the sleeve material radially inwards into the gap 52 and the recess between the surface 22 and the left end of the sleeve 12.

[0055] Here, radial inward movement completes the sealing of the bore 34 by the sleeve 12, and the continued axial force applied to the stem nose 2 through the nozzle 400 causes the strain limit to be reached at the neck 14 (as will be understood by those skilled in the art), where the stem nose 2 breaks, thereby leaving a set plug sealed within the bore 34, as shown in FIG. Fig.11 shown.

[0056] It will be appreciated that the annular protrusion 24 (in this example an annular ring formed with a sharp peak profile, such as Fig.12 The annular projection 24 may further be used to move the material of the sleeve 12 radially outward to seal the bore 34 and radially inward to seal the inner shoulder 21 and the tapered portion 50 during the setting operation. In addition, the annular projection 24 may provide an extended sealing surface between the rod head 6 and the end of the sleeve 12 (against the rod head 6) to enhance fluid leakage resistance.

[0057] It will be appreciated by those skilled in the art that the presence of the annular projection 24 is preferred, but not essential, for the application of the present invention. It can be seen that in the case of the presence of the annular projection 24 on the shoulder 20, its purpose is the same as that disclosed in EP-A-1,440,272, i.e., to allow the annular projection 24 to penetrate into the material of the sleeve 12 during the setting process of the sealing plug, thereby creating an additional and effective fluid seal between the head 6 and the sleeve 12 in the blind hole. As mentioned above, since the material of the head 6 is harder than the material of the sleeve 12, the annular projection 24 can penetrate into the material of the sleeve 12.

[0058] During setting of the sealing plug in the above example, it will be appreciated that the high axial forces applied by the rod head 6 to the sleeve 12 (17.5 kN in this example to seal the 8 mm diameter hole 34) result in the sleeve material forming an effective axial seal within the hole 34 and the static reducer 30 due to the high (radial pressures may peak at 200 MPa and residual stresses of approximately 100 MPa after the neck 14 breaks) resultant radial stresses. These stresses act to provide an effective seal between the hole 34 and the sleeve 12 and between the sleeve 12 and the surfaces (6, 50 and 46) of the rod 200 so as to provide a leak-proof plug.

[0059] The tight fit of the rod head 6 within the bore 34 also serves to minimize the escape of sleeve 12 material around the outer edge of the shoulder 23. The annular protrusion (such as 24) or outer edge 23 formed on the inner shoulder 21 serves to embed the sleeve 12 and provide an independent sealing feature of the rod head 6 against the sleeve 12, thereby preventing leakage through the bore of the installed sleeve 12. Likewise, the tight fit of the tapered front face 30 of the nozzle within the bore 34 limits the escape of sleeve 12 material around the front face 30 of the nozzle and toward the setting tool 600.

[0060] The breaking of the broken neck 14 generates a recoil force which is used to push the remaining rod 200 portion in the sleeve 12 to the left in a manner known to those skilled in the art, such as Fig.12 However, the intimate contact formed between the taper 50 on the rod 200 and the radially inner compressed sleeve 12 material that has flowed into the gap 52 ensures that there is no relative axial movement that could reduce the effectiveness of the seal formed between the outer surface of the sleeve 12 and the bore 34. The taper 50 also serves to maintain the integrity of the seal if the end of the rod 200 is subsequently accidentally impacted by an external object or intentionally interfered with.

[0061] Although in the above example the rod 200 has been shown with a series of annular grooves 10 along its axial extent, alternatives may be used by those skilled in the art. For example, the outer surface of the rod 200 may be formed with a helical groove. In this case, the nozzle 400 of the setting tool 600 will also be provided with a complementary helical groove for rotational engagement with the outer helical groove of the rod, thereby enabling the tool 600 to move the rod 200 relative to the sleeve 12 so as to achieve installation of the plug in a known manner. In practice, it will be understood that the rod may be provided with, for example, a female thread, and the setting tool 600 with a complementary male thread. However, it may not be necessary at all for the outer surface of the rod to be provided with any profile.

[0062] Those skilled in the art will appreciate that the broken neck 14 is not necessary for the present invention. As an alternative example, the tool 600 can apply a predetermined pulling force on the rod 200 and then simply separate from the rod. This can be achieved by, for example, a rotary pulling tool that engages with the outer surface of the spiral groove formed on the outer surface 2.

[0063] Features List

[0064] 200 shots

[0065] 400 Nozzle

[0066] 600 Setting tools

[0067] 2 Proximal cylindrical protrusion

[0068] 4 Central

[0069] 6 Distal head

[0070] 8 Tapered end of rod

[0071] 10 Rod ring groove

[0072] 12 Sleeve

[0073] 13 Front tapered area

[0074] 14 Weakened area for rod fracture

[0075] 15 Rear tapered area

[0076] 16 Maximum diameter of central area 4

[0077] 18 Minimum diameter of the central area

[0078] 20 Annular shoulder

[0079] 21 Inner Shoulder

[0080] 22 Surface of shoulder 20

[0081] 23 Outer edge of shoulder

[0082] 24 Annular protrusion

[0083] 26 Difference between head and sleeve

[0084] 28 Rounded part of the head

[0085] 30 Front of the nozzle

[0086] 32 Clearance between the nozzle and the sleeve

[0087] 34 Blind hole

[0088] 35 Area where the material of the first sleeve flows

[0089] 36 Workpiece having hole 34 formed therein

[0090] 38 Front part of nozzle

[0091] 42 The head 6 penetrates into the sleeve 12

[0092] 44 Sleeve radial inner

[0093] 46 The radial inner portion of the sleeve 12

[0094] 48 Contact point between hole 34 and sleeve

[0095] 50 Inner rod tapered portion

[0096] 52 The gap between the interior of the sleeve 12 and the rod tapered portion 50

Claims

1. A sealing plug for blindly installing in a workpiece hole (34) so ​​as to plug and seal the workpiece hole, the sealing plug comprising: a cylindrical hollow sleeve (12) defining a first axis (AA) and having a given outer diameter; A rod (200) comprising a proximal cylindrical protrusion (2), a distal rod head (6) and a central portion (4) located between the proximal cylindrical protrusion and the distal rod head (6), wherein the outer diameter of the distal rod head (6) is greater than the outer diameter of the central portion, and wherein the outer diameter of the central portion is greater than the outer diameter of the proximal cylindrical protrusion of the rod, and wherein the rod defines a second axis (BB); The distal rod head (6) has an annular shoulder (20) adjacent to the central portion (4) of the rod, the annular shoulder being inclined at an acute angle (α) relative to the radius of the second axis (BB), and the annular shoulder comprising an inner shoulder (21); The distal rod head (6) is formed of a material harder than the material of the sleeve; the central portion of the rod being arranged, when within the sleeve, to be retained within the sleeve by frictional engagement between an exterior portion of the central portion of the rod and an interior portion of the sleeve such that the first axis and the second axis are coaxial; The sealing plug is characterized in that the outer diameter of the central portion of the rod gradually decreases relative to the axis of the rod in the direction from the proximal cylindrical protrusion of the rod to the distal rod head (6) until a minimum central portion diameter (18) is reached, at which point the central portion of the rod intersects with the distal rod head (6).

2. The sealing plug according to claim 1, wherein: The inclination of the annular shoulder (20) forms a concave area facing the central portion of the rod.

3. The sealing plug according to claim 1, wherein: The inclination angle of the annular shoulder (20) relative to the radius of the second axis is between 5° and 25°.

4. The sealing plug according to claim 3, wherein: The inclination angle of the annular shoulder (20) is between 10° and 15°.

5. The sealing plug according to claim 4, wherein: The inclination angle of the annular shoulder (20) is 14°.

6. A sealing plug according to any one of the preceding claims, wherein: An annular protrusion (24) facing the central portion of the rod is formed on the distal rod head.

7. The sealing plug according to claim 6, wherein: The annular projection (24) is arranged to engage with the hollow sleeve.

8. The sealing plug according to any one of claims 1 to 5, wherein: The central portion (4) of the rod is formed with an axial tapered portion (15) which narrows in a direction from the distal rod head (6) towards the proximal cylindrical protrusion (2).

9. A method for setting a sealing plug as claimed in any one of claims 1 to 5, the method using a setting tool (600) having a nozzle (400), the nozzle having a tapered end (30), the setting tool being capable of gripping the proximal cylindrical protrusion (2) of the rod through the tapered end, the method comprising: Inserting the sealing plug into the blind hole so that the proximal cylindrical protrusion of the rod protrudes from the hole; Passing the nozzle of the setting tool through the proximal cylindrical protrusion of the rod and placing the nozzle against the sleeve; moving a proximal cylindrical protrusion of the stem toward the setting tool, thereby causing relative axial movement between the stem and the sleeve; The method is characterized in that the relative movement between the rod and the sleeve causes the material of the sleeve to first deform radially outward from the proximal end of the rod adjacent to the nozzle of the sealing tool under axial compression when the distal rod head moves axially to engage with the sleeve, and then the material of the sleeve is axially tapered and deformed along the central portion of the rod toward the distal rod head so as to deform radially inward along the tapered portion (50).

10. The method according to claim 9, wherein: The tapered portion of the nozzle is convex so as to facilitate radially outward expansion of the sleeve.

11. The method according to claim 9 or 10, wherein: The stem has a breakaway neck formed therein, the breakaway neck being adapted to break when the sealing plug is set and when a predetermined axial force is applied to the captured stem.

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