EP3192132A1

EP3192132A1 - Socket outlet

Info

Publication number: EP3192132A1
Application number: EP15839549.1A
Authority: EP
Inventors: Nima SHAHINIAN; Harald Furu
Original assignee: Home Control As
Current assignee: Home Control As
Priority date: 2014-09-09
Filing date: 2015-09-08
Publication date: 2017-07-19
Anticipated expiration: 2035-09-08
Also published as: EP3192132A4; WO2016039631A1; CN107112690B; NO337978B1; CN107112690A; ES2861357T3; NO20141092A1; EP3192132B1

Abstract

A socket (100) comprises a cover (120) with a cylindrical well face (130) having greater diameter than an enveloping cylinder (230) about an existing, predefined plug (200), at least two contact holes (121) adapted to receive contact pins (211) for transmitting electrical power, wherein each contact hole (121) is located at the bottom of a concave contact pin-guide (141, 142). Ground terminals (112) are arranged in the well (130). When a plug is inserted in the well (130), the contact pins on the plug slide along the concave guides (141, 142) toward the contact holes (121). Thereby, the plug is rotated about the cylindrical well's axis of rotation symmetry. In one embodiment, the contact pins of the plug is longer than the distance between the contact holes (121) and the top of the ground terminals (112). Thereby, the plug may rotate in the well (130) unhindered by the ground terminals (112). An alternative embodiment where the ground terminal is a ground pin for a polarised socket is also disclosed.

Description

SOCKET OUTLET

BACKGROUND

Field of the invention

[0001] The present invention concerns contacts for connection to a power supply network, in particular a socket with facilitated entry of a plug.

Prior and related art

[0002] Movable electro technical equipment typically has a power cord with a plug, and connects to a power supply network by inserting the plug into a socket, which is permanently connected to the power supply network. Currently, about 20 such connections are in use in different countries. Common to all, is that the terminals with live voltage are available through contact holes in the socket, and that the plug has protruding contact pins fitting into the contact holes. The shape of contact pins and their corresponding contact holes vary. For example, blade shaped contact pins are used in USA, whereas cylindrical contact pins are usual in Europe. Some contacts are polarised, i.e. that certain contact pins should be connected to certain current conducting wires denoted line (L) and neutral (N). Other contacts are unpolarised, wherein it is irrelevant which contact pin is connected to current conducting wire L or N. Both polarised and unpolarised contacts can be grounded or ungrounded. This description regards a grounded socket, which has terminals connected to electrical ground (earth) in addition to the current conducting terminals for the contact pins of the plug.

Because the ground terminals are at a fixed ground potential, and accordingly do not convey electrical power during normal operation, the ground terminals can be exposed in the socket. The ground terminals can also have different design in different countries. For example, a spring biased ground clip adapted to a groove in the plug is common in Germany and several other European countries, while a ground pin adapted to a hole in the plug is common in France.

[0003] In order to facilitate sale of electrical apparatuses, and to make it convenient for travellers to bring along electrical apparatuses from one country to another, electrotechnical equipment, including plugs and sockets, becomes ever more standardised. US International Trade Administration (IT A) has accorded letters A-N to the most common connections, and a European standard, Certification of Electrotechnical Equipment (CEE) applies to electro- technical equipment in most of Europe. For example, most electrical apparatuses in Europe except Great Britain and Ireland are delivered with a grounded plug of type CEE 7/7, which is included in ITA's type F. This plug is used as an example in the following. One skilled in the art can without inventive effort adapt the example to other types of contacts. Other contact types will also be described when relevant.

[0004] It is impractical to have to change plug on lamps, ovens and other electrotechnical equipment in order to adapt the equipment to the invention. Because European electro- technical equipment currently is delivered with a plug ofthe type CEE 7/7 and compatible types, one objective of the present invention is that a European implementation must be able to receive plugs, but not necessarily all plugs that can be received in a socket of type CEE 7/7. In general, an objective is that the socket according to the present invention should be able to receive a plug of a kind that is delivered with equipment sold for domestic use also in countries with different standards, e.g. Great Britain and USA, typically for 110 V or 220-240 V network voltage.

[0005] US 1 812 343 A discloses a socket with a short and a long guiding groove that guides contact pins on a plug toward respective openings in the socket when the plug is pressed against them. At the same time, this causes the plug to turn with respect to the socket.

[0006] DE 653 597 C discloses a similar socket with two opposing, semi-circular concave faces that are inclined in opposite directions toward respective contact holes such that the contact pins slides toward the contact hole, and the plug turns accordingly, when the plug is pressed against the socket.

[0007] Some countries, for example Denmark, Finland, Norway and Sweden, require that the sockets have a child safety device, i.e. equipment to prevent children from getting into contact with the power supply network. The child safety device is typically a lid over the contact holes and/or a device that requires that the contact pins can only be inserted if they are pressed against both contact holes simultaneously.

[0008] Furthermore, there is an increased attention on so-called universal design, i.e. that buildings, apartments, offices and items in daily use are designed such that people with reduced abilities can use them without help or additional adaptation. Thus, an additional purpose of the present invention is to provide a socket with such universal design.

[0009] Existing outlets can be mounted entirely on the outside of a wall, or they can have permanent connections to the power supply network in a box embedded in the wall, and just a cover at the outside of the wall. In both cases, there is a desire to be able to retrofit a socket in an existing installation.

[0010] The objective of the present invention is thus to provide a socket that satisfies at least one of the needs above, and that preserves advantages from prior art. SUMMARY OF THE INVENTION

[0011] This objective is attained with a socket according to claim 1.

[0012] In particular, the invention provides a socket comprising a cover with a cylindrical well having greater diameter than an enveloping cylinder about an existing, predefined plug, at least two contact holes adapted to receive contact pins for transmitting electrical power, wherein each contact hole is located at the bottom of a concave contact pin-guide. The socket has ground terminals arranged in the well.

[0013] When a plug is inserted in the well, the contact pins on the plug slide along the concave guides toward the contact hole. Thereby, the plug is rotated about the cylindrical well's axis of rotation symmetry.

[0014] In one embodiment, the contact pins of the plug is longer than the distance between the contact holes and the top of the ground terminals. Thereby, the plug may rotate in the well unhindered by the ground terminals.

[0015] The contact pin-guides preferably have an inclination from their respective contact holes to a narrower and shallower part of the contact pin-guides. Viewed from above, the contact pin-guides will thereby have large open surfaces facing upwards near the contact holes, and gradually smaller open surfaces in a rotational direction away from the contact holes. If the contact pins on the plug engage a narrower part of the contact pin-guides, the plug will rotate toward the contact holes in a certain direction, e.g. counterclockwise.

[0016] In some embodiments, the cover is attached by a snap-lock to a contact box. This facilitates mounting of the cover once the contact box is mounted on a wall or similar.

[0017] In some embodiments, the well further comprises two protruding elements with mutual parallel, plane side faces in the longitudinal direction of the well, guiding grooves that extend radially outward from a mid-section on the plane side faces and that extend from the bottom of the well to top faces on the protruding elements. The side faces are adapted to the plug, for example a plug according to CEE 7/7, and the guiding grooves are in that case adapted to the guiding ribs on the plug. The side faces and the guide grooves take up loads applied to the plug while it is inserted in the socket, and can also contribute with friction force in order to retain the plug in the well.

[0018] In a first embodiment of the protruding elements, both top faces on each protruding element is oriented perpendicular to the well's axis of rotation symmetry. In this embodiment, the side faces and guide grooves merely havet the functions discussed in the previous paragraph. [0019] In a second embodiment of the protruding elements, a first top face on each protruding element is oriented perpendicular on the well's axis of rotation symmetry, and a second top face on each protruding element forms a helical face along the cylindrical wall of the well and has the least distance to the bottom of the well at the guiding groove. In this embodiment, the first top faces prevent further axial motion of the plug in the well when the plug is not correctly oriented in the well. Thus, this embodiment may be suitable for polarised contacts. When the plug is correctly oriented in the well, it will slide along the helical top faces and thereby move axially until the contact pins are inserted in the contact holes.

[0020] The helical face preferably has the same inclination as the bottom of the contact pin- guides. Thereby, the top face support the sides of the plug, the guide ribs in the example above, at the same time as the contact pin-guides slide along the contact pin-guides toward the contact holes.

[0021] In a third embodiment of the protruding elements, both top faces on each protruding element are helical faces leading toward the guiding grooves. This facilitates insertion of a plug with guide ribs or similar.

[0022] The socket preferably also has a guide from an outer face of the cover toward the well. This guide guides the plug toward the well when it is moved against the outer surface of the cover.

[0023] Further features and advantages of the present invention appear in the dependent claims and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will be described in greater detail in the following by means of exemplary embodiments with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of a socket viewed from a first viewpoint;

Fig. 2 is a perspective view of the socket in Fig. 1 viewed from a second viewpoint;

Fig. 3 is a side view of the socket in Figs. 1 and 2 with a partially inserted plug;

Fig. 4 is a section along the plane TV-TV in Fig. 3;

Fig. 5 is a top view of a connection box for the socket in figures 1-4;

Fig. 6 is a top view of the connection box in figure 5 with a cover;

Fig. 7 is a side view of the socket viewed from a side oriented 90° from the side shown in figure 3;

Fig. 8 shows a part of an alternative embodiment viewed from above; Fig. 9 is a section along the plane IX-IX in figure 8;

Fig. 10 is a section along the plane X-X in figure 8;

Fig. 11 illustrates a guide with two parallel top faces;

Fig. 12 illustrates a guide with two inclined top faces;

Fig. 13 is a perspective view of a socket with ground clip and

Fig. 13 is a perspective view of a socket with ground pin.

DETAILED DESCRIPTION

[0025] The drawings are schematic, and not necessarily to scale. Several details known to those skilled in the art are omitted for clarity. In the figures 1-7 so-called "schuko" ground clips serve as a first example on ground terminals 112, while a ground pin 150 serves as an example in the figures 8- 12. The term ground terminal in the claims comprise these and other elements for connecting a plug to ground. Furthermore, the terms ground clip and ground pin in the following description be understood as examples of "ground terminal" as the term is used in the claims.

[0026] Figures 1 and 2 are perspective views of a socket 100 with ground terminals 112, a cover 120 and a guide 123 that leads from an outer surface on the cover 120 toward a well 130 for receiving a plug 300 (Fig. 3). Figure 1 also shows a connection box 110 filling into a standard wall box. The cover has an integrated and resilient snap-lock 116 retaining it to the connection box 110. The connection box 110 has one or more openings (not shown) for a ground cable from the power supply network. Trough-shaped contact pin-guides 141, 142 is fixedly disposed in the bottom of the well 130, and are best shown in figure 2. Contact holes 121 for contact pins on a plug 200 are located in the bottom of the trough shaped contact pin- guides 141, 142. When a plug is inserted into the well 130, the contact pins will slide along the guiding faces 141 and 142 and along an imagined helical face down to their respective contact holes 121. In other words, the contact pin-guides 141 and 142 have an inclination from their respective contact holes 121 to a narrower and shallower part of the contact pin- guides 141, 142, i.e. clockwise in figure 2.

[0027] Figure 3 illustrates a plug 200 inserted in a socket 100 according to the invention. In this example, the plug 200 is of type CEE 7/7 and the socket 100 is adapted this plug and compatible types. The line TV-TV illustrates an imaginary plane through the centre of the contact pins on such a plug 200, and also through the centre of the contact holes 121 in the socket 100. [0028] The socket 200 has a cylinder face 230 with diameter slightly less than the well 130 shown in the preceding figures. The cylinder face 230 is broken by a plane 231, which in the shown position is parallel to the paper plane. A guide rib 232 protrudes from the plane 231 and is encompassed by an imaginary extension of the cylinder face 230 such that the guide rib 232 can pass down into the cylindrical well 130 shown in figures 1 and 2. A similar plane 231 with guide rib 232 is provided on the diametrically opposite side of the plug 200.

[0029] As mentioned in connection with figure 1, the cover 210 is attached to the connection box 110 by means of snap-lock 116. The snap-lock 116 is here an integrated and resilient part of the cover. When mounting the cover on the connection box 110, the snap-lock 116 slides along the wall of the connection box. When the cover is mounted, the snap-lock 116 is biased inwardly toward the connection box 110 such that shoulder or the like against an edge on the connection box 110 retains the cover on the connection box 110. The cover can alternatively be attached to the connection box 110 with one or more screw(s) in a known manner.

[0030] Figure 4 is a section along the plane TV -TV in figure 3. The plug 200 is not part of the invention, and is therefore shown without inner details. A guide 123 between the outer surface of the cover 120 and the well 130 (fig. 1) leads the plug toward the well 130 when the plug 200 is inserted. In figure 4, the guide 123 is shown as a concave, rounded transition, whereas it is shown as a frusto-conical transition in the figures 9-11. It should be understood that any shape guiding the plug 200 to toward the well 130 may be used. In the position shown in Fig. 4, the contact pins 221 of the plug is barely inserted in the contact holes 121, and the bottom of the plug 200, from which the contact pins 221 extend, is located within the guide 123, but above the ground clip 112. It is understood that the distance between the bottom of the contact pin-guides 141, 142 and the top of the ground clip 112 must be less than the length of the contact pins 121. In a CEE 7/7 plug, the length of the contact pins 221 19 mm. Thus, in the example on figure 4, the top of the ground clips 112 are e.g. 16- 18 mm over the bottom of the contact pin-guides 141, 142 such that the plug 200 can rotate unhindered or unobstructed by the ground clips 112. Similarly, the distance from the contact holes 121 to the top of other types of ground contacts, e.g. a ground pin in a French socket (150 in figures 8- 10), be less than the length of the contact pins 221.

[0031] Figure 4 also shows how a lower edge of the snap-lock 116 engages an edge on the connection box 110 and thereby retains the cover.

[0032] Figure 5 is a top view of the connection box 110, more particularly the socket from the preceding figures viewed from above without cover. The connection box 110 comprises a plate 1100 with fastening holes 1101 for attachment to a wall or similar, for example with screws. Electric ground potential is supplied through two diametrically opposed ground clips 112 to complementary ground rails on the plug (not shown in Fig. 5). For this, the ground clips 112 are radially biased inwardly, and slide along the axially directed ground rail when the plug is inserted or withdrawn.

[0033] A ground terminal 1120 is connected to ground in the power supply network. The ground terminal 1120 can be a ground rail fixedly attached to the ground clips 112, which in that case is attached to the connection f\box 110. Alternatively, the ground clips 112 can be attached to a ground rail on the cover (not shown in figure 5), which engages the ground terminal 1120 when the cover is mounted.

[0034] Sliding terminals 111 in the extension of the contact holes 121 (Fig. 6) is, when in use, electrically connected to the live connectors in the power supply network, and provide both mechanical and electrical connections to the contact pins (221, fig. 4) on the plug.

[0035] Figure 6 shows the socket 100 in the same scale and orientation as the connection box 110 in figure 5. Thus, a cover 120 is mounted on the connection box 110 in Fig. 5. The cover comprises the top plate 120, which is not necessarily plane. The ground clips 112 are located in openings on the cover 120, and the axis between the ground clips 112 is perpendicular to the axis through the centres of the contact holes 121.

[0036] Figure 7 shows the socket from a side that is perpendicular to the side shown in figure 3. In the shown embodiment, the ground clips 112 are located in openings 114 through the wall of the cover 120. Thus, during insertion of the plug, the ground clips 112 can be partly pushed outward and into the opening 114. When the plug is inserted, the bias will force the ground clip 112 against a complementary ground rail (212, fig. 10) on the plug.

[0037] In the embodiment in figures 1-7 it does not matter which contact pin on the plug is inserted into which contact hole 121 in the socket, and the originally German "schuko"- contact with two symmetrically placed ground clips 112 is used as example. In the example on the figures 8-10, the symmetrically ground clips 112 are replaced with an asymmetrically placed ground pin 150 to illustrate a polarised socket, i.e. a contact where each contact pin must be inserted in a certain contact hole. The plug of type CEE 7/7 has a hole to receive one ground pin 150 from an originally French standard, and is therefore used as example.

[0038] Figure 8 shows the alternative embodiment viewed from above. As discussed in connection with figure 3, a plug 200 may have a substantially cylindrical outer face 230 cut by two planes 231, each with a protruding guiding rib 232. The embodiment in the figures 8- 10 has similarly a substantially cylindrical well 130 with protruding elements 131 and guide groves 132 adapted to a plug of type CEE 7/7 and compatible types. The guide grooves 132 extend radially outward from parallel plane side faces toward the cylinder wall in the well 130, i.e. along an axis through the centres of contact holes 121 in the contact pin-guides 141, 142. The plane IX-IX is perpendicular to this axis, and cuts through the centre of the contact pin 150 in figure 8. The guide grooves 132 extend from the bottom of the well 130 to top faces 1210 and 1311. The top faces 1310 are diametrically opposing each other, and the top faces 1311 are diametrically opposing each other.

[0039] The variant with German ground clips, e.g. as shown in Fig. 6, can advantageously also be provided with similar protruding elements or guiding faces 131 and guide grooves 132. The "alternative embodiment" should here and in the following be construed as a contact with guide faces 131, 132 etc. in the well, regardless of whether the grounding comprises clips as in figure 6 or a pin as in figure 8.

[0040] Figure 9 is a section along the plane IX-IX in figure 8, and illustrates a first embodiment of the protruding elements 131. The guide 123 and the contact pin-guides 141, 142 are as in the embodiment in the figures 1-7, and are not described again here. The part 1310 of the top face for the element 131 here extends perpendicular to the well's axis of rotation symmetry, and is placed at a sufficient distance from the bottom of the well 130 to allow the plug 200 to rotate over the ground pin 150 when the guide rib 232 of the plug (figures 3 and 10) slides along the top face part 1310.

[0041] Another part 1311 of the top face of the element 131 is inclined downwardly toward the guide groove 132. As the inclined face 1311 extends along a cylinder wall, the top face 1311 in this embodiment a helical face with inclination in the same direction as the plug will be guided toward the contact holes 121 during insertion into the socket, i.e. counterclockwise in figure 8 and toward the left hand side of figure 9. Thus, the plug in figure 3 can move axially down on the ground pin 150 when a guide rib 232 on the plug slides along the part 1311 of the top face, but not when it slides along the part 1310 of the top face.

[0042] Figure 10 shows the plug 200 with contact pins 221 engaging the bottom of the contact pin-guides 141, 142. The guide ribs 232 is supported by both top faces 130, which are diametrically opposite each other, see Fig. 8. Thereby, the rotational axis of the plug 200 parallel to the axis of the ground pin 150. When the plug 200 rotates such that the guide ribs slide along the helical faces 1311, the axis of rotation remains parallel to the pin 150, which thereby will slide easily into the corresponding hole in the plug if the plug is correctly oriented in the well. That is, the axis of the ground hole in the plug 200 cannot possibly be inclined relative to the ground pin 150. If the pin 150 does not enter the hole, the plug must be oriented 180° erroneous, such that the N-pin is aligned with the L-hole and vice versa. The top faces 1310 and the contact pin-guides 141, 142 in figure 9 support a subsequent 180° rotation.

[0043] Without the protruding elements 131, the asymmetric shape of the contact pin-guides 141, 142 implies that the plug 200 is guided axially downward to the contact holes 121 regardless of where the contact pins engages. With the embodiment in figure 9, the guide ribs 232 can engage the top face 1310 without the contact pins 221 engaging the bottom of the contact pin-guides 141, 142. If the contact pins 221 are rotated toward a narrower and shallower part of the contact pin-guides 141, 142, they will quickly arrive in the position shown in figure 10. A further rotation in the same direction, i.e. clockwise in figure 8, will lift the plug 200 axially upward in the well 130. A small rotation in the opposite direction will move the guide ribs over the top faces 1311, which here are helical, such that the contact pins 221 are guided axially downward toward the contact holes 121. Thus, the user quickly receives a tactile feedback on the correct direction of rotation even with horizontal guiding faces 130, more precisely top faces 1310 that are perpendicular to the well's axis of rotation symmetry at a distance from the contact holes 121 that is larger than the length of the contact pins 221 of the plug. Thus, the variant in figures 9 and 10 can be advantageous in polarised contacts, here exemplified by the eccentric pin 150, because the guide is asymmetric.

[0044] Figure 11 shows a second embodiment of the top faces 1310 and 1311, where both pairs of top faces 1310, 1311 extend perpendicular to the well's axis of rotation symmetry, i.e. parallel to the paper plane in figure 8. In such an embodiment, the height from the contact holes 121 to the top faces 1310, 1311 of the protruding elements 131 preferably adapted such that the contact pins 221 of the plug can slide unobstructed along the bottom of the contact pin-guides 141, 142 during insertion of the plug. The groove 132 then receives the guide rib 232 on the plug only when the plug is inserted fully into the socket, and contributes with friction force to retain the plug and also by taking up forces applied to the plug when it is plugged into the socket 100.

[0045] Figure 12 shows a third embodiment of the protruding elements 131, where both top faces 1310 and 1311 are inclined downward toward the guide groove 132. This embodiment facilitates insertion of the guide rib 232 into the guide groove 132. Support from the top faces align the hole in the plug with the ground pin 150 as in the embodiment in the figures 9 and 10. The embodiment in figure 12 does not support 180° rotation as the embodiment in figures 9 and 10. As the embodiments shown in figures 9-11, the embodiment in figure 12 contributes with friction force and support against lateral forces on the top of the plug 200 when it is fully inserted in the socket. [0046] In all three embodiments shown ing figures 9-12, the ground pin 150 is sufficiently long to ensure that the plug 200 is grounded before the contact pins 221 engages the live terminals. This is a common requirement in standards for sockets with ground terminals, CEE 7/7 included. Provided this requirement is met, the length of the contact pin 150 can be adapted the guides in the socket 100, the length of the contact pins 221 on the plug 200 and the distance from the top faces 1310, 1311 to the live terminals (not shown) in the socket 100. In a preferred embodiment, the inclined face 1311 has the same inclination as the bottom of the contact pin-guides 141 and 142.

[0047] From figures 8-12 with description, it should be understood that the top faces 1310 and 1311 together with the ground pin 150 provide a tctile feedback to the user on the orientation of the plug, and that the asymmetric shape in figure 9, specifically the horizontal faces 1310, especially facilitates changing the orientation of the plug in the well 130.

[0048] Figure 13 illustrate a socket 100 with guiding faces 1310 and 1311 as described in connection with figures 8-12, but with a ground clip 112 replacing the ground pin 150. The top plate 120 with the transition 123 and the trough-shaped symmetrical guides 141 and 142 are described above. Figure 14 is similar to figure 13, bus has a ground pin 150 rather than the ground clips 112. Bothe embodiments shown in figures 13 and 14 can be used with a plug according to the European standard CEE 7/7, and represent an unpolarised contact and a polarised contact, respectively. Furthermore, it is understood that the invention is not limited to CEE 7/7, and that symmetric or asymmetric guides similar to the top faces 1310 and 1311 in figures 9, 11 and 12 can be used in other types of contacts.

[0049] The invention is described with reference to examples of a socket for a plug of a certain type, but the scope of the patent is defined by the following claims.

Claims

1. A socket (100) comprising a cover (120) with a cylindrical well (130) having greater diameter than an enveloping cylinder (230) about an existing, predefined plug (200), at least two contact holes (121) adapted to receive contact pins (211) for transmitting electrical power, wherein each contact hole (121) is located at the bottom of a concave contact pin-guide (141, 142), characterised by

ground terminals (112; 150) arranged in the well (130).

2. The socket (100) according to claim 1, wherein the contact pins (221) of the plug is longer than the distance between the contact holes (121) and the top of the ground terminals (112, 150).

3. The socket (100) according to claim 1 or 2, wherein the contact pin-guides (141, 142) have an inclination from their respective contact holes (121) to a narrower and shallower part of the contact pin-guides (141, 142).

4. The socket (100) according to any preceding claim, wherein the cover (120) is attached by a snap-lock (116) to a contact box (110).

5. The socket (100) according to any preceding claim, wherein the well (130) further comprises two protruding elements (131) with mutual parallel, plane side faces in the longitudinal direction of the well, guiding grooves (132) that extend radially outward from a mid- section on the plane side faces and that extend from the bottom of the well (130) to top faces (1310, 1311) on the protruding elements (131).

6. The socket (100) according to claim 5, wherein a first top face (1310) on each

protruding element (131) is oriented perpendicular on the well's axis of rotation symmetry, and a second top face (1300) on each protruding element (131) forms a helical face along the cylindrical wall of the well and has the least distance to the bottom of the well (130) at the guiding groove (132).

7. The socket (100) according to claim 6, wherein the helical face (1311) has the same inclination as the bottom of the contact pin-guides (141, 142).

8. The socket (100) according to claim 5, wherein both top faces (1310, 1311) on each protruding element (131) are helical faces leading toward the guiding grooves (132).

9. The socket (100) according to claim 5, wherein at least one top faces (1310, 1311) on each protruding element (131) are helical faces leading toward the guiding grooves (132).

10. The socket (100) according to any preceding claim, further comprising a guide (123) from an outer face of the cover (120) toward the well (130).