EP3111519B1

EP3111519B1 - Socket

Info

Publication number: EP3111519B1
Application number: EP15751300.3A
Authority: EP
Inventors: Nima J. SHAHINIAN; Harald Furu
Original assignee: Home Control As
Current assignee: Home Control As
Priority date: 2014-02-24
Filing date: 2015-02-18
Publication date: 2019-07-17
Anticipated expiration: 2035-02-18
Also published as: ES2745198T3; EP3111519A4; EP3111519A1; NO20140238A1; NO337061B1; WO2015126260A1

Description

BACKGROUND

Field of the invention

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

Movable electrotechnical 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.
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 (ITA) has accorded letters A-N to the most common connections, and a European standard, Certification of Electrotechnical Equipment (CEE) applies to electrotechnical 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.
Specifically, Figures 1a and 1b illustrate a plug 200 of type CEE 7/7, which is a hybrid between a German and a French standard. The original German plug is standardised as CEE 7/4 ("Schuko"), and defines two cylindrical contact pins with length L = 19 mm, diameter d = 4.0 mm and distance S = 19 mm between the central axes as shown in Figure 1a. CEE 7/7 defines a plug with somewhat different dimensions than those shown in Fig. 1a, but the socket according to CEE 7/7 receives both new plugs of type CEE 7/7 and older plugs of type CEE 7/4.
Figure 1b shows the plug in Figure 1a viewed from below. Here, a hole 250 adapted to a ground pin from the French standard is visible. A metal sleeve within the hole 250 is connected to metal plate in the ground groove 212 from the German CEE 7/4, and onward to a ground wire in the apparatus' power cord. Maximum diameter a for the plug, sizes b, c for a guiding nose 232 and other measures are found in CEE 7/7.
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 electrotechnical equipment is delivered with a plug of the type illustrated in Figures 1a and 1b, one objective of the present invention is that a European implementation must be able to receive plugs of type CEE 7/7 and similar, 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, typically for 110 V or 220-240 V network voltage.
Fig. 2a shows a schematic section through a commercially available, grounded socket 10 for the plug shown in Figures 1a and 1b. The illustrated variety has a cover which lies on a wall surface 15 and semi-circular groves 14 (see Fig. 2b) in order to guide the plug's contact pins toward contact holes 121. The socket 10 has a well with depth less than the length of the contact pins in CEE 7/7, i.e. h < 19 mm. Thus, the contact pins 211 (Fig. 1) can slide on the bottom face of the well and/or in the guides 14 until they hit the holes 121, and the plug can then be pressed down until the contact pins hit the terminal 111, which are different terminals L and N in a polarised contact. These terminal 111 are connected to the power supply network, which in this example has 220-240 V AC and delivers a current up to 16 A. A radially biased ground clip 112 is connected to a ground wire in the power supply network. The electrical terminals L, N and ground are connected to wires, and placed in a wall box 11 in a known manner.
Figure 2b shows the socket in Figure 2a viewed from above. The circle drawn with a dot-dash-line corresponds to the section through the press plate shown with a dot-dash line in in Figure 2a. Thus, the edge of wall box 11 is visible. The semi-circular grooves 14 serve to guide the contact pins of the plug toward the holes 121, and are therefore deepest at the holes 121 and less deep toward their ends. Similar grooves are found in some commercially available sockets, e.g. in Elko model 1091. The ground clips 112 are shown schematically, and are biased radially inward, such that they will firmly engage ground grooves in a plug inserted into the socket.
The guides 14 shown in Figures 2a and 2b guides the contact pins toward the contact hole 121, but it may still be difficult to align the contact pins, especially if the socket is located on a place where the contact holes are not visible, or for people with reduced vision or functional abilities. Therefore, sockets with larger and deeper contact pin-guides, which guide the plug's contact pins toward the contact hole in the socket, are provided.
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.
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.
DE3731588 A1 discloses a socket comprising a spring-loaded cover plate protecting the socket against dust.
DE 2457072 A1 discloses a grounded electrical socket with concave contact leads as described above. This socket is further developed with a base plate that can be shifted axially in the direction of the contact pins disclosed in DE 270 1 188 AI against a spring force. The latter is considered to be the closest prior art.
WO2005/025012 A1 discloses a socket comprising an electrical terminal receptacle moveable within a body. The receptacle is releasable retained in a first position while no plug is inserted in the socket.
US2006/172583 A1 discloses a socket for receiving a plug.
FR 2840117 A1 discloses a socket comprising a removable mechanism with a fixed and moving section, so that the socket slides between two positions. When the plug is in place, the socket is pushed into the wall, hiding the plug.
EP 2456021 A1 discloses a socket that includes slidable mobile side posts.
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.
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.
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

This objective is attained with a socket according to claim 1.
In particular, the invention provides a socket comprising a cover with a cylindrical well face for receiving a predefined plug and comprising at least two contact holes adapted to receive contact pins of said plug for transmitting electrical power thereto, wherein each contact hole is located at the bottom of a concave contact pin-guide. The contact holes and the contact pin-guides are disposed on a press plate, which is axially movable along the well face between an outer position, wherein the press plate is biased outwardly by a spring, and an inner position, wherein contact pins and ground contacts on the plug inserted into the socket are electrically connected to their respective terminals adapted for fixed connection to a power supply network. The press plate is rotatably movable about a rotational symmetry axis (z) of the cylindrical well face between a first orientation where the contact holes are angularly displaced from the terminals and a second orientation where the contact holes are angularly aligned with the terminals.
The existing, predefines plug is preferably a type that is delivered with electrotechnical equipment in a region, for example type CEE 7/7 in Europe or a corresponding grounded plug in other parts of the world. The contacts on the plug comprises both contact pins and ground contacts.
When the press plate is in its outer position, the contact pins may slide freely in the contact pin-guides without being obstructed by ground terminals in the socket. When the contact pins have entered the contact holes, the plug is oriented and can be moved axially onto the ground terminals. The outward axial bias prevents the press plate from moving to its inner position while the contact pins are pressed against the bottom of the concave contact pin-guides. This makes it easier for people with reduced functional abilities to insert a grounded plug into a grounded socket.
When the terminals are connected to a power supply network, electrically conductive terminals transmit electrical power to the contact pins, and one or more ground terminal(s) connected to a ground wire in the power supply network connect the plug's ground contact(s) with electrical ground potential. The terminals may be mounted in a connection box from a previously installed socket, such that only the previous is replaced with the cover according to the invention, which has an axially movable press plate. Alternatively, the terminals may be mounted in a connection box as part of the socket, such that new terminals must be connected to the power supply network in a known manner. In both alternatives, the terminals are adapted for fixed connection to the power supply network. This facilitates retrofitting the invention in an existing installation. In addition, costs are reduced if the cover can be retrofitted over a previously installed connection box.
The angular displacement makes it possible to prevent that an object inserted into the contact holes hits the terminals that transmit current and voltage, and thereby acts as a child safety device.
Each contact hole leads preferably to a tunnel extending axially in an elongated body. If a child inserts an electrically conducting rod into the contact hole and pivots the rod from side to side, the angular amplitude is limited by the tunnel openings to arctan (D/Lt), where D is the largest cross section of the contact hole and Lt is the length of the tunnel. For example, the maximum angular amplitude decreases from about 70° for a contact hole through a plate with thickness Lt = 0,5D to below 30° if the tunnel is extended to Lt = 2D. This reduces the risk for injury to a child, and thus increases the safety.
In a preferred embodiment, the press plate is held in its inner position by a radially directed element. This prevents the press plate from moving outward and pulling along the plug, and becomes more important with an increasingly powerful bias on the press plate. The radially extending member can be a fixed rib, particularly if the bias is large.
In some embodiments, the radially directed element is radially biased inwardly from the cylindrical well face. When the press plate has forced such an element radially out toward the well face and passed a certain axial position, the biased element moved inward on the upper side of the press plate, and keep it in its inner position. This may provide a tactile feedback to the user indicating that the plug is properly inserted. When the plug is pulled out, the biasing force of the radial holding elements must be overcome without pulling the plug out of the press plate.
In an alternative embodiment, the tunnel in the elongated body comprises an electrically conductive sleeve connected to a power supplying sliding contact displaced from the contact hole. When the press plate with the contact holes is in the outer position, the sleeve is isolated from the sliding contact such that the child with the rod do not engage the live wires even if the child touches the electrically conductive sleeve. When the press plate is in its inner position, the sliding contact is closed such that electric voltage is transmitted to the contact pins through the electrically conductive sleeve. An electrically conductive sleeve can clamp the contact pins in a similar manner as the sliding contacts in a traditional socket, and possibly be adapted such that the press plate is pulled out together with the plug in embodiments with radially biased holding elements.
The child safety can be further improved by directing the contact holes (121) in the outer position toward an electrically insulating element placed behind the press plate. In embodiments wherein the press plate only moves axially, a child safety device from prior art can be employed. The insulating elements are then plates that can only be removed from the contact holes when two contact pins are pressed against them simultaneously. In embodiments wherein the press plate turns about the central axis between the outer and inner position, an insulating sleeve can be mounted, for example in the extension of an elongated tunnel. The rotational motion during insertion of the plug will then displace the contact hole from the insulating sleeve to a live terminal.
A frusto-conical guiding face is preferably arranged between a top face of the cover and the cylindrical well face. This transition acts as a funnel and guides the plug toward the well and the press plate. Insertion of the plug is thereby further facilitated.
Further features and advantages of the present invention appear in the dependent claims and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

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. 1a: illustrates a known plug that may be used with the present invention;
Fig. 1b: shows the plug in Fig. 1a viewed from below;
Fig. 2a: is a schematic section through a known, grounded socket;
Fig. 2b: shows the socket in Fig. 2a viewed from above;
Fig. 3a: shows a plug inserted in a socket according to the invention;
Fig. 3b: shows an embodiment of a press plate for use in the invention;
Fig. 4: is a perspective view of a preferred embodiment;
Fig. 5: shows a detail from Figure 4;
Fig. 6: is a top view of the preferred embodiment with the press plate in its outer position;
Fig. 7: is a first schematic section through the embodiment in Figure 6;
Fig. 8: shows the embodiment in Figure 6 with the press plate in its inner position; and
Fig. 9: is a second schematic section through the embodiment in Figures 3-8.

DETAILED DESCRIPTION

Figures 1 and 2 illustrate prior art, and are described above.
Figure 3a 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 to this plug and compatible types.
The illustrated embodiment of the socket 100 is configured for wall mounting, and for this comprises a connection box 110 that fits into a standard wall box 11 (Fig. 2a), and a cover 120 covering the wall box. The opening 113 is for a cable from the power supply network, in this example a cable with a ground wire and conductors L and N as in Fig. 2a. These are to be electrically connected to electrotechnical equipment through a power cord (not shown) through the opening 202 in the plug 200.
For ease of description, an imaginary central axis z is drawn through the socket 100. This x-axis is coaxial with the axis of rotation of a cylindrical well face 130 with diameter greater than a cylinder wall or enveloping cylinder 230 about the plug. In this description, the terms "axial" and "radial" refer to the central axis z. Thus, when the plug is inserted, as in Fig. 3a, the cylinders 130 and 230 extend coaxially about the central axis z, and both contact pins and all ground contacts on the plug are directed axially.
A frusto-conical transition 123 guides the plug toward the well bounded by the well face 130 when the plug is inserted.
Electrical ground potential is transmitted through two diametrically opposed ground clamps 112 (not shown in Fig. 3a) to complementary ground grooves 212 on the plug. For this, the ground clips are radially biased inward toward the central axis z, and slide along the axially directed ground groove 212 when the plug 200 is inserted or withdrawn. The contact pins on the plug (not shown) slide in a similar manner along complementary sliding terminals. What is termed axial displacement herein, is thus generally used to provide electrical contact between complementary contacts on the plug and terminals within the socket, for example ground clip/ground groove and contact pin/sliding terminal. As noted, contact pins for electrical wires extend from the plug, but the socket may also have a contact pin for ground that is inserted into a sliding contact (250 in Fig. 1b) by axial displacement.
The enveloping cylinder 230 of the plug is broken by a control face 231 that extends axially and parallel to the axis through the diametrically opposed ground grooves 212. If desirable, a corresponding face can be provided in the well of the socket, for example in order to accommodate certain standards. In principle, however, any cylinder face 230 of which a part 231 is cut away fits into a cylindrical face with larger diameter. The well in the socket 100 is therefore depicted as a straight cylinder without control faces adapted to local standards.
The guiding rib 232 on the plug 200 can have a corresponding groove in the well of the socket, but again this is an adaptation comprised by the invention. As long as the outer face of the control rib 232 lies on or inside (the imaginary) enveloping cylinder extending from the face 230 on the plug, the plug 200 may be inserted in a cylindrical well with larger diameter.
Fig. 3b illustrates a press plate 140 for use in the invention. The press plate 140 can generally move axially along the well face 130 on the socket 100, and may for this have radially directed lugs 143 fitting into corresponding groves in the cylinderwall 130 and/or radially directed grooves 144 adapted to elements protruding radially inward from the cylindrical well face 130 in various embodiments. For example, ground clips 112 can pass through grooves 144 in the press plate as the press plate 140 is displaced axially in the socket 100. Thus, in general, radially directed guiding elements such as lugs 143 and/or grooves 144 be distributed along the circumference of the press plate 140.
In this example, the press plate 140 has axially directed contact holes 121 for two cylindrical contact pins on a plug of type CEE 7/7. The contact holes 121 are located in the bottom of concave contact pin- guides 141 and 142, which have the same function as the semi-circular guides 14 shown in Fig. 2b. Thus, the concave contact pin- guides 141 and 142 guide the contact pins 211 toward the contact holes 121 when the plug 200 is pressed axially against the press plate 140 in the direction into the paper plane in Figure 3b. This applies regardless of where or how the contact pins engages the press plate 140. The plug 200 will rotate about the central axis z when the contact pins slide along the bottom of the contact pin- guides 141 and 142.
Figure 4 shows the press plate 140 with the contact pin- guides 141 and 142 in an inner position. The press plate has an outer position, wherein ground terminals such as ground clips 212 and a ground pin (not shown) adapted to the ground hole 250 in Fig. 1b is fully or partially hidden. Hence, in the outer position, the contact pins can slide unobstructed by ground terminals along the bottom of the concave contact pin- guides 141 and 142 toward the contact holes 121. In a polarised contact, the ground element advantageously protrude somewhat from the press plate in the outer position, such that the contact pins are guided toward their respective terminals L and N. For example, the ground pin in a polarised French contact protrude somewhat over the top face of the press plate when this is in its outer position. When the contact pins are inserted into the contact holes 121 by the contact pin- guides 141 and 142, there are two possibilities. Either, the contact pins are correctly oriented, such that the ground pin slips into the ground hole 250, or the orientation is incorrect, such that the ground pin prevents further axial motion of the plug 200. In the latter case, it suffices to withdraw the plug a short distance, correct the orientation (rotate the plug 180° about the central axis in this example) and insert the contact pins into the contact holes with correct orientation. In an unpolarised contact, such as the "Schuko"-contact in this example, the orientation of the contact pins is indifferent, and both possible orientations are therefore correct orientation.
When the contact pins are inserted into the contact holes 121 with correct orientation, the press plate is displaced along with the plug to the inner position shown in Figure 4. This inner position can preferably only be reached when the plug 200 is inserted, and Figure 4 shows the press plate in its inner position merely for illustration. As shown in Fig. 4, the press plate is guided axially over a ground clip 112, which thereby is electrically connected to the ground groove 212 on an inserted plug. Similarly, an axial displacement will insert an axially directed ground pin into a complementary hole, the hole 250 in Fig. 1b in this example, on a correctly oriented polarised plug.
The press plate 140 with the contact pin-guide 142 can move axially along the ground clip 112. The ground clip 112 can thereby also serve as axial guide for the press plate. In order to avoid that press plate pivots about the axis between diametrically opposing ground clips 112, the press plate can advantageously be provided with guiding walls (not shown) extending parallel to the sides of the ground clip 112.
The press plate 140 must be able to resist a certain axial force in its outer position such that the contact pins can slide along the concave contact pin- guides 141 and 142 without causing the press plate to move toward the inner position shown in Figure 4. The press plate is therefore outwardly biased by a spring when in the outer position. In order to hold the press plate in its inner position, radially directed holding elements may be mounted, in Fig. 4 represented by ground clip 212 and a ball 146, both of which are biased radially inward by a spring force. When the plug is inserted, the radial biasing forces must be overcome before the holding element snaps in place above the press plate. The user holding the plug 200 may feel more or less distinctly that such an element, for example the ball 146, snaps in position. With sufficient radial bias, the user is provided with a distinct tactile feedback when the press plate is in its inner position, and thereby that the plug is fully inserted.
Figure 5 shows the encircled detail in Figure 4. The cover 120, the conical guide 123, the well face 130 and the concave contact pin-guide 142 are recognised from Figure 4. The ground clip 112 is springy and biased radially inward. When the press plate moves axially along the well face 130, the ground clip 112 is pushed radially outward into a recess 114 in the cylindrical well face. When the press plate has passed and is in its inner position, the ground clip 112 engages the press plate, and thereby exerts an axial force on the press plate that contributes to hold the press plate in the inner position shown in Figure 4. It is understood that the ball 146 in Fig. 4 can move radially outward in a similar manner, and that a suitable number radially biased elements 112, 146 collectively can overcome the spring force needed to keep the press plate in its outer position while the contact pins slide in the contact pin- guides 141, 142 when the plug is inserted. In such an embodiment the press plate must be provided with clamps or the like, such that it can be pulled out together with the plug. An electrically conductive sleeve mounted in the contact hole can act as a clamp about the contact pins on the plug, and is described in greater detail below.
Figure 6 shows a preferred embodiment, wherein the press plate with the contact pin- guides 141, 142 is angularly displaced relative to the cove 120. In this example, the axis 122 through the centres of the contact holes 121 is rotated 30° clockwise about the central axis z with respect to the lower edge of the cover 120. The angular displacement is preferably sufficient to ensure that the contact holes 121 are not aligned with the AC-terminals behind the cover 120, but the shown angle of 30° is otherwise randomly selected. In this embodiment, the press plate 140 acts as a child safety device in that an object inserted axially through a contact hole 121 does not engage a live terminal, i.e. one of the power transmitting terminals L or N.
Figure 7 is a section along the plane VII-VII in figure 6, i.e. through the centre of a contact hole 121 viewed along the axis through the centres of the contact holes. The cover 120 is cut as in Figure 2a. The socket 100 is mounted on a wall surface 15, and the connection box 110 is adapted to a standard wall box 11 embedded behind the wall face 15 in a known manner. The connection box 110 contains sliding contacts or sleeves for contact pins connected to AC-terminals L and N as in Figure 2a. Usually, the connection box 110 and cover 120 are delivered as a unit. However, it is possible to make a cover 120 with axially displaceable pressure plate adapted to an existing connection box.
In Figure 7, the press plate 140 is in its upper position at the bottom of the frusto-conical guiding face 123. The guiding face 123 and the concave contact pin-guide 141 in the press plate 140 are configured to guide a contact pin toward the contact hole 121. The section shows the tail end of the other contact pin-guide 142, which guides the second contact pin toward a similar contact hole hidden behind the illustrated contact hole 121.
From Figure 7, it is apparent that the contact hole 121 is not aligned with the current conducting sliding contacts or sleeves L and N. Furthermore, the contact hole in the bottom of the concave contact pin-guide 141 the opening to an elongated tunnel. In reality, the tunnel is just an extension of a short cylindrical contact hole 121 through the press plate. An elongated object inserted through the shown elongated tunnel 121 can be moved laterally less than a similar object that can pivot freely about a centre in a hole in a thin plate. More particularly, the angular amplitude is limited by the tunnel openings to arctan(D/L_t), where D is the largest cross section of the contact hole and L_t is the length of the tunnel. For example, the maximum angular amplitude decreases from about 70° for a plate having thickness L_t = 0,5D to below 30° with a tunnel length L_t = 2D. This reduces the risk for a child inserting an object through the hole 121 from the outside, and thereby unintentionally contacts one or both the current conducting terminals L and N. If desirable, the connection box 110 may be provided with an electrically insulating blocking element (not shown) in the extension of the hole or tunnel 121 in Figure 7, such that it is impossible to insert an object into the hole before the press plate 140 is rotated about the central axis z, and the hole 121 thus is displaced from the blocking element.
In Figure 7, a ground bar connected to the ground clips 112 is shown mounted on a cylindrical pin 115 at the central axis z.
The ground bar can be fixed relative to the well face 130 as in a traditional socket. A similar pin is used in traditional sockets, and iit is hence possible to make a cover according to the invention with a ground pin fitting in a ground hole in an existing installation.
Alternatively, the ground bar can be attached to the press plate 140, and the cylindrical pin 115 can still be inserted into an existing connection box. In this embodiment, the cylindrical pin 115 functions as a shaft for rotation about the central axis z, such that a ground pin for a polarised plug (the hole 250 in Figure 1b) is fixed relative to the press plate 140, and thereby can protrude over the press plate as described above.
The press plate 140 is biased radially outwards, i.e. in the z-direction, by a spring 145. In the embodiment on Figure 7 and in an embodiment wherein the press plate only moves axially, the spring 145 must have sufficient stiffness to return the press plate 140 to the upper position, but not stiffness large enough to force the plug 200 out of the socket. The spring 145 can be one or more spiral springs. However, in embodiments where the press plate 140 can rotate about the z-axis, spiral springs would require a separate sliding connection, while leaf springs and disc springs have a face along which the press plate may slide. Hence, the spring 145 is schematically shown as a curve, which preferably represents a leaf spring or a disc spring. In particular, it is noted that such a leaf spring or disc spring can be affixed in a mid plane for the axial motion. When the press plate 140 passes the mid plane, such a leaf spring or disc spring will curve in an opposite direction, and thereby push the press plate inwardly toward the electrically conductive contacts L and N. This can be useful if the plug is attached to the press plate.
Figure 8 corresponds to Figure 6, but the press plate is rotated such that the axis 122 through the centres of the contact holes 121 extends parallel to the edge of the cover, and is aligned with the conductive contacts below. The top plate is also displaced to the inner position, such that the ground clips 112 are visible.
Figure 9 is a section through the plane IX-IX in Figure 8, i.e. centrally through the socket along the axis 122. The top plate 140 is in its inner position, and the contact holes 121 are aligned with their respective sliding terminals in the connection box 110. It is understood that a cable from the power supply network is inserted through the wall box 11 and hole 113 in the connection box for electric connection as illustrated in Figure 7, but which is not shown in Figure 9.
The rotation of the press plate 140 about the central axis z from the orientation shown in Figures 6 and 7 to the orientation shown in the figures 8 and 9 has, as noted, aligned the contact holes 121 with their respective sliding contacts in the connection box. Such a rotation is enabled in a practical manner by providing the cylindrical face of the well with axial ribs 131 directed radially inwardly, such that the top plate 140 can slide on top of them. The rotation can be stopped by a radially directed element, for example a wall or groove 13 as shown in the traditional socket illustrated in Figure 2b. In the present example, the groove 13 can be adapted to the nose 232 on the plug 200 shown in Figure 3a. The ground clip 112 and the top af the groove for the rib 232 are 90° apart, and may if desirable serve as support for the top plate 140 instead of or in addition to separate ribs 131 on the cylinder walls.
The rotation is preferably less than the angular distance between ribs and other radially directed elements. In the present example, the rotation is 30° about the z-axis. Figure 9 indicates 8 radially extending elements with 45° distance between them, of which two ribs 131, one ground clip 112 and two walls 13 are visible in the figure. As long as the rotation is less than the angular distance between the radially extending elements on the cylinder wall 130, no groove in the press plate 140 slides over any radially extending element before it is aligned over ribs and ground terminals, and thereby can move axially.
In Figure 9, the press plate 140 is rotated and moved axially inward along the ribs 131 from the position on Figure 7. The distance from the top of press plate 140 to the sliding contacts in the connection box in Figure 9 is shorter than the contact pins on the plug, i.e. less than 19 mm in the present example. This limits the length of the conical elements around the contact holes 121.
The spring 145 is compressed by the axial displacement of the press plate 140. The spring force is proportional to the compression and the stiffness of the spring, and must be overcome by the plug's friction against fixed parts of the socket. If not, the spring force will push the plug out of the socket.
In an alternative embodiment, the order of the rotational and axial displacements can be interchanged. Then, when the plug is inserted, the press plate 140 is first displaced axially along ribs 131, and thereafter rotated under the ribs. Then, the spring force from spring 145 can be increased because it forces the top plate against the bottom of axially directed ribs 131. When the plug is pulled out, the press plate is then first rotated until grooves in the press plate is aligned with the ribs 131, and the spring 145 contributes with a force pushing the plug toward the outer position.
In a variety, the rotational and axial motions can be combined to a helical motion. The plug 200 then rotates about the z-axis while the contact pins slide along the surfaces of the troughs 141 and 142 toward the contact holes 121 as described above, and slides thereafter axially into the holes 121. The rotational and axial motion of the press plate 140 then follows in essentially the same direction.
In yet another variety, the sliding contacts 111, which in figure 9 are depicted as cylinders, edge contacts, and the contact holes 121 have electrically conductive sleeves inside. These sleeves preferably clams the contact pins when the plug is inserted, such that the press plate is pulled along when the plug is pulled out. When the press plate is in its outer position as in Figures 6 and 7, there is no electrical contact between electrically conducting faces within the contact holes 121 and the live wires.
It is recognised that any contact connecting the contact holes to their respective conducting terminals in the inner position and breaks the connection in the outer position can be used in a socket with axial motion. Similarly, a contact that is closed or broken by a rotation be used in varieties with a press plate that rotates about the z-axis. An axial motion combined with a rotation in a freely selected order can thus provide electrical contact between electrically conductive faces in the contact holes 121 in the top plate 140 and sliding contacts 111 permanently connected to the power supply network, including when the siding contacts 111 are not axially directed cylinders in the extension of the holes 121 as shown in the drawings.
The invention is described with reference to an example of a socket for a plug of a certain type, but the scope of the patent is defined by the following claims.

Claims

A socket (100) comprising socket terminals (111, 112), a cover (120) with a cylindrical well face (130) for receiving a plug (200) and comprising at least two contact holes (121) adapted to receive contact pins (211) of said plug for transmitting electrical power thereto, wherein each contact hole (121) is located at the bottom of a concave contact pin-guide (141, 142), said contact holes (121) and the contact pin-guides (141, 142) are disposed on a press plate (140), wherein said press plate (140) is configured to be axially movable along the well face (130) between an outer position, wherein the press plate is biased outwardly by a spring (145), and an inner position, wherein contact pins (211) and ground contacts (212, 250) on the plug (200), said plug (200) inserted into the socket (100), are electrically connected to their respective socket terminals (111, 112), characterised in that the press plate (140) is rotatably movable about a rotational symmetry axis (z) of the cylindrical well face (130) between a first orientation where the contact holes (121) are angularly displaced from the terminals (111) and a second orientation where the contact holes (121) are angularly aligned with the terminals (111), wherein the cylindrical well face (130) has axial ribs (131) directed radially inwardly, such that the press plate (140) can rotatably slide on top of them.
The socket (100) according to claim 1, wherein the press plate (140) is held in its inner position by a radially directed holding element (112, 146; 131).
The socket (100) according to claim 2, wherein the radially directed holding element (146) is radially biased inwardly from the cylindrical well face (130).
The socket (100) according to any preceding claim, wherein each contact hole (121) leads to a tunnel extending axially in an elongated body (124).
The socket (100) according to claim 4, wherein the tunnel in the elongated body (124) comprises an electrically conductive sleeve connected to a power supplying sliding contact displaced from the contact hole (121).
The socket (100) according to claim 5, wherein the electrically conductive sleeve is adapted to clamp a contact pin such that the press plate is pulled out together with the plug.
The socket (100) according to any preceding claim, wherein the contact holes (121) in the outer position are directed toward an electrically insulating element placed behind the press plate (140).
The socket (100) according to any preceding claim, further comprising a frusto-conical guiding face (123) between a top face of the cover (120) and the cylindrical well face (130).