The present invention relates to a power plug for insertion into a socket. More specifically, the power plug is designed for insertion into an electrical socket. The invention is particularly suited to use on maritime installations such as vessels, platforms etc., but can also be utilized on onshore installations, or in any situation where electrical sockets are present and a secure connection between the plug and socket is desired.

Background of the invention

Power plugs having both a male side to be inserted into a socket and at least one female side for connecting external power consuming units are known. The most common of these are adaptors, extension leads, timers for plug sockets, and multi socket plugs. Adaptors are used to convert from one typical electrical system to another to enable the use of devices designed to fit standard sockets in different countries, or more specifically countries or systems using different sockets. Such adaptors are often referred to as travel adaptors. Extension leads are often essential in order to power a device some distance away from a main power source. A timer for a plug socket is designed to be plugged into the socket, after which the appliance is plugged into the timer and a selection can be made as to when and for how long e.g. a light, kettle, or other power consuming appliance should be supplied with electrical power. Multi-socket plugs are similar to extension leads without the lead or cord, and can be used when there is a need to couple several devices to a single outlet.

CN205195010U describes a plug for connection to a socket. The plug includes a power jack, allowing connection of another plug of another electrical appliance to the same socket through the power jack. The plug has a projecting body comprising slots convenient for user to plug in and detach. The plug is not temporarily or permanently secured to the socket by additional means. US10454215B2 describes a power plug to be temporarily or permanently secured to a contact point by means of a suction cup. US4566185A describes a plug to be temporarily or permanently secured to a contact point by means of adhesive sections. CN203481582U describes a power plug with a jack having the function of a socket. The power plug comprises a body with a power cord, plugs and a jack. The power plug further comprising a hinged cover and a pull ring for pulling out the plug. The plug does not include any additional fastening means for temporarily or permanently securing the plug to a socket.

EP 3396788 A1 describes locking of plug adapters to power sockets by means of a locking mechanism. The locking mechanism is actuated in order to lock the plug to the socket. The plug comprises a male side to be connected to the socket and a female side with which a further plug device may be plugged into. The locking mechanism is actuated in the presence of a device plug plugged into the female side of the plug.

US 2016344138 A1 describes a device for monitoring and controlling power to electronic devices. A smart plug is described including a housing unit, at least one electrical contact at one side of the housing unit, at least one electrical receptacle on an opposite surface and a cover to close over the electrical receptacle. It also comprises a locking mechanism, however this locking mechanism is securing the cover to the housing unit and the cover prevents plug devices inserted into the receptacle form accidentally being removed. US 2016344138 A1 does not describe any mechanism for preventing the smart plug itself accidentally being removed from a socket.

WO 9300726 A1 describes an electrical plug comprising a housing having a face portion and a cylindrical head portion with two cylindrical contact pins extending out from the cylindrical head portion. The cylindrical head portion is descried to have at least one elastic axially disposed peripheral friction rib providing controlled friction between the plug head and the recessed socket wherein the plug is to be inserted. The at least one friction rib engages the inner surface of the socket in order to make it more difficult to withdraw from the socket. Onboard seagoing vessels, existing contact points for power supply are used to both permanently and temporarily install equipment. Permanently installed equipment may include safety systems like alarms, man over board detection systems, gas and smoke sensors etc. and temporarily installed equipment will include equipment required for repair and maintenance such as power tools, cleansing machines, and so on. Small corridors or gangways make the environment on board a vessel particularly challenging. Traditionally, splitters or branches project out fairly far from the contact point, increasing the risk of stumbling over them. This constitutes a risk of injury or damage both to personnel and/or to equipment. In addition, when disconnecting plugs form a power socket, there is a risk of the splitters or branches also being disconnected. Equipment plugged into sockets onboard a vessel should remain connected where possible due to the important safety or operational function they might provide. There is a need to address the above challenges.

Summary of the invention

In the following throughout the specification, the following terms means: The term “plug” used throughout this document is used to describe a movable connector attached to a power consuming device. The term “gate” is used herein to describe a critical communications unit for safety monitoring onboard a vessel or the like.

A main object of the present invention is to provide a power plug which reduces the need for modification when retrofitting new equipment, such as gates or sensors of a crew monitoring system, to a vessel.

Another object of the present invention is to provide a power plug which allows additional power consuming equipment to be powered from a single electrical socket.

Another object of the present invention is to provide a power plug which reduces the risk of accidental disconnection of equipment, for example in the event of a crew member kicking or stumbling over connectors. A further object of the present invention is to provide a secure connection of equipment to an electrical grid. In some examples such equipment may be sensing devices, gates, or other units critical for ensuring safety of crew members on board a vessel. The equipment may allow constant monitoring of safety critical areas or functions and transmissions of signals.

The objects are achieved by the provision of a power plug as defined in the preamble of the independent claims, having the features of the characterizing portions of the independent claims. A plurality of embodiments, variants or alternatives of the invention are defined by the dependent claims.

According to a first aspect of the present invention, there is provided a power plug for installation in a power socket at offshore installations, such as vessels, platforms, etc. or onshore installations. The power plug comprises a housing and a male connector on a first side of the housing. The male connector comprises a plurality of protruding male connector pins for insertion into the power socket to form an electrical connection. The power plug comprises at least one connection securing device coupled to the housing and positioned such that it contacts the power socket when the power plug is inserted therein to increase the frictional force opposing removal of the power plug from the socket. The at least one connection securing device is configured to be inserted into the housing such that at least a part of the connection securing device contacts the socket when the plug is installed to provide the increased frictional force.

In embodiments, the power plug comprises a female connector on a second side of the housing comprising a plurality of female pin connector holes for receiving a male connector of a plug of a power consuming device.

In embodiments, the at least one connection securing device is configured to possess a continuous series of positions within the housing wherein it is gradually inserted into the socket and contacts the socket with an increasing contact area providing an increasing frictional force. In embodiments, wherein the at least one connection securing device is having an increasing width from the entry section where the at least one connection securing device first comes in contact with the socket to the end section where the at least one connection securing device is fully in contact with the socket providing adjustment of the frictional force.

In embodiments, the male and female connectors are corresponding connectors such that the female connector of the power plug has the same configuration as a power socket suitable for receiving the male connector.

In embodiments, the connection securing device is removably coupled to the housing.

In embodiments, the connection securing device comprises at least one holding pin, said at least one holding pin being configured to be inserted into the housing such that a part of the at least one hold pin contacts the socket when the plug is installed to provide the increased frictional force.

In embodiments, the at least one holding pin is slidably movable from a first position where it projects out at the female connector side prior to activation to a second position wherein said at least one holding pin is activated and projects out at the male connector side to contact the socket when the power plug is installed.

In embodiments, the one or more holding pins comprise a tail end and a wider head end, and contact between the connection securing device and the socket is between the tail end of the holding pin and the socket housing.

In embodiments, the part of the at least one holding pin contacting the socket when the plug is installed comprises a tapered end. The end configured to be inserted into the socket first may be thinner than the region of the pin further up towards the other end (which may be the head end).

In embodiments, the second position comprises a continuous series of positions in which the pin is pushed gradually further into the opening so that more of the holding pin surface contacts the socket when the power plug is installed. This allows the force required to remove the plug from the socket to be carefully adjusted in a simple manner. In embodiments, the at least one holding pin is having an increasing width or diameter from the entry section, the point where the at least one holding pin enters the socket, to the end section, where the at least one holding pin is fully in contact with the socket.

In embodiments, the connection securing device comprises a layer of friction increasing material partly or fully covering at least a part of the housing.

In embodiments, the power plug comprises an electrical cable extending out of the body of the power plug, the electrical cable being connectable to sensors, gates or other power consuming equipment.

In embodiments, the power plug is coupled to a communication unit of a crew monitoring system and the communication unit receives one or more of data and power via the vessel powerlines, the socket, and the power plug.

According to a second aspect of the present invention, there is provided a monitoring system for a vessel, the monitoring system comprising: a central controller; one or more gates configured to be communicatively coupled to the controller, each gate comprising a power plug configured to be inserted into a power socket of the vessel; and a plurality of mobile units each configured to be worn by, carried by, or attached to a crew member or a piece of movable equipment and configured to send data by wireless connection to the gates of the system, wherein each power plug comprises: a housing having a male connector on a first side of the housing comprising a plurality of protruding male connector pins for insertion into the power socket to form an electrical connection, and a female connector on a second side of the housing comprising a plurality of female pin connector holes for receiving a further plug from a power consuming device. The female pin connector holes may be connector slots. At least one connection securing device is coupled to the power plug for preventing accidental removal of the power plug from the socket.

In embodiments, the male and female connectors are corresponding connectors such that the female connector of the power plug has the same configuration as a power socket suitable to receive the male connector. In embodiments, the connection securing device is configured to contact the power socket when the power plug is inserted in the socket, and an electrical connection is made, to increase the frictional force opposing removal of the power plug from the socket.

In embodiments, when the gate is plugged into the power socket, data can be sent from the gate to the central controller using the vessel powerlines.

In embodiments, power is provided to the gate via the socket and the vessel powerlines.

In embodiments, the connection securing device comprises at least one holding pin, said at least one holding pin being configured to be inserted into the housing such that a protruding part of the at least one hold pin contacts the socket when the plug is installed to provide the increased frictional force.

According to a third aspect of the present invention, there is provided a power plug for installation in a power socket, the power plug comprising; a housing; a male connector on a first side of the housing comprising one or more protruding male connector pins for insertion into female connectors of the power socket to form an electrical connection, the power plug comprising at least one connection securing device coupled to the power plug for contacting one or more parts of the power socket when the power plug is installed, and an electrical connection is made, to increase a frictional force resisting removal of the power plug from the power socket.

According to a fourth aspect of the present invention, there is provided a power plug for installation in a power socket, the power plug comprising; a housing; a male connector on a first side of the housing comprising one or more protruding male connector pins for insertion into female connectors of the power socket to form an electrical connection, the power plug comprising at least one connection securing device for contacting one or more parts of the power socket when the power plug is installed, and an electrical connection is made, wherein the connection securing device comprises a magnet within the power plug housing for attraction to a corresponding magnet in the socket. The present invention relates to a power plug for a power consuming unit, the power plug having one male connector to be plugged into a contact point or socket and, in some cases, also an out-going cable to a power consuming unit. The power plug can also comprise a female connector side into which a further plug or a power consuming unit such as a sensor, gate, tools or other equipment may be plugged to provide the unit with power. The power plug may thus function as an intervening unit, located between a plug and socket and conveying power from the socket to the plug of a power consuming device. In some cases, the female and male connectors are complementary. The configuration of the female connector exposed on the power plug for receiving the power plug of an external device is therefore the same as would be available in the socket if the power plug were not present. The power plug can be used to provide additional functionality, such as providing connection to or forming part of a gate for a monitoring system, without reducing the number of connection points available within the installation for plugging in external power consuming devices.

The power plug preferably also includes a connection securing device, which ensures that the electrical connection between the power plug and socket is not interrupted, for example if the power plug is accidentally knocked. When a complementary female connector side is present, the connection securing device also ensures that when the plug of a power consuming device is pulled out from the female connector side, the power plug remains within the socket and an electrical connection between the power plug and the socket is maintained. This can be crucial if the power plug is to provide additional function, such as if it is used as part of a tracking system, as mentioned briefly above and discussed in more detail below.

The present invention relates to a power plug which is removably connected to a socket, but where an increased force or effort is needed to unplug it in order to reduce the likelihood of accidental removal of the power plug. In order to ensure that the power plug does not to detach from the outlet accidentally, the power plug is connected to the wall, power outlet box, or socket by means of the connection securing device as mentioned above. This device may comprise adhesive, fasteners, hook-and-loop fasteners (Velcro), and clips, magnets within the socket and plug housing, friction increasing tabs, covers, or inserts, or any other releasable fastening means which can increase the force required to remove the power plug from the socket.

In an example, the connection securing device works by increasing a coefficient of friction or a frictional force between a surface of the power plug housing and a facing surface of the socket. The connection securing device may therefore be located on the housing or male connector pins of the power plug and may be formed of an elastomeric material, such as rubber, or another similar material to increase this frictional force without requiring any adaption of the socket. The power plug can then be used with standard sockets. This is highly advantageous in the case of a system to be used on a vessel or within a building because the vessel or building can be retrofitted with a system including a plurality of the power plugs without adaption to the existing infrastructure being required. The coefficient of friction between the plug and socket should be greater than the coefficient of friction between the power plug of an external device inserted into the female connector provided on the plug. This way, when the external device is pulled out, the power plug itself will remain within the socket. The force required to pull the power plug out from the socket may be at least 1.5 times as large, more preferably at least twice as large, and most preferably at least three times as large, as the force required to pull an external device (with standard pin configuration in standard materials such as metal) out from the female connector of the power plug. The coefficient of friction can be adjusted by selecting holding pins having different widths. A larger holding pin will provide a higher coefficient of friction and will result in the power plug being more difficult to remove from the socket. The opening can be large enough to receive holding pins with a diameter of up to 3 mm, preferably up to 2 mm.

The at least one connection securing device is configured to be inserted into the housing such that at least a part of the connection securing device contacts the socket when the plug is installed to provide the increased frictional force. The at least one connection securing device can be movable from a first position, representing a non-activated position, in which the connecting securing device is not in contact with the socket, to a second position comprising a continuous series of positions where it is gradually inserted into the socket, allowing for an increased contact area or coefficient of friction between the plug and socket, and thus an increased frictional force opposing the removal of the power plug from the socket. It may also have a predefined first position where it is partly in contact with the socket but can be further inserted in order to adjust the coefficient of friction between the power plug and the socket into which it is inserted, and thus increase the frictional force between the power plug and the socket. If it is desired for removal of the power plug from the socket to be easier, for example for safety reasons, the at least one connection device can be partially inserted, providing a flexible system. The possibility of adjusting of the coefficient of friction, and thus adjusting the frictional force, allows the user to install equipment more sensible of being unplugged than regular equipment.

The at least one connection securing device may have an increased width from the point where it first comes in contact with the socket to the point where it is in the position where it is fully in contact with the socket, giving a further possibility of adjusting the coefficient of friction and thus the frictional force.

Where the power plug is used as part of a safety monitoring system, the connection securing device ensures that continuous electrical power can be supplied to critical equipment like sensors and other safety equipment. The power plug is kept in position within the socket, making the connection of sensors or other critical equipment more stable and user friendly. The likelihood of accidental unplugging is considerably reduced, and a constant signal is safeguarded.

The power plug can be used to supply power to parts of a crew monitoring system, which can be used in any situation where safety is an issue, but which is particularly suited to use on a seafaring vessel. The monitoring system may comprise a plurality of gates or readers, which receive power through the power plug, or which are comprised as part of the power plug. The gates communicate wirelessly with mobile units which will typically be carried by crew members or worn as a wristband, chip, portable card, necklace, or any other similar wearable item. The mobile units may in some cases include sensors and can send sensor data, alerts, or information resulting from the processing of sensor data back to a central controller via the gate. The sensors may provide health data (such as heart rate or blood pressure readings) or position data. The position of the mobile unit, and hence the current whereabouts of the crew member by which it is worn, is also sent to the central controller via the gates and may be determined based on sensor readings or based on which gates receive a signal from the mobile unit at which time.

Connection between the gates of the monitoring system and the central controller may be wireless or may be via powerline communication, in which case the communication lines are set up by plugging the power plug of the gate into a power socket. Power for the gate may also be sourced through the socket or the gate may be battery powered or powered by other means. Use of the powerlines to communicate between gates or between a gate and a central controller is extremely beneficial on a vessel because of the intermittent nature of wireless communication in such an environment. The system can also be very easily retrofitted to an existing vessel simply by plugging gates into power sockets in rooms or areas of the vessel where monitoring of mobile units is desired. If the power plug also comprises a female connector then normal use of the power plugs of the vessel for external devices is not inhibited or reduced.

Such a monitoring system installed on a PGS ship, for example, may make use of tens or hundreds of such gates, which will then occupy a large number of power sockets. In order to maintain a number of available connection points without requiring electrical modifications to be undertaken, the power plug of the present invention can be used. This will avoid large scale modifications of the electrics, which are challenging onboard vessels, and are both time and resource consuming, particularly given the additional challenges due to humidity and corrosion in saline environments. The power plug both couples a gate or unit of the monitoring system to the power socket to transfer power, data, or both, to the gate, and provides an additional female connector point to maintain the functionality of the socket.

Where the power plug forms part of or is coupled to a gate of a crew monitoring system it is clearly very important that either of power or a communication connection to the gate is not lost. Loss of a signal from the gate at a critical time could result in the inability to track a crew member within a particular area and to determine when they may be in danger and when emergency protocol may be required. The connection securing device of the power plug is especially advantageous in this situation because it ensures constant connection to the gate of the monitoring system even when external equipment is plugged into and pulled out of the female connector side of the power plug. The sockets can be utilized as normal with the monitoring system in constant use and retrofitted in a simple manner to the existing infrastructure of the vessel.

The connection securing device can comprise one or more holding pins formed of an elastomeric material, such as rubber, to create an increased frictional force between the plug and socket which can help to prevent accidental removal of the plug from the socket. The holding pin or pins may be wedged between the plug and the socket, keeping the plug in a secure position within the socket. The holding pins can also be arranged along the pins of the male connector such that they are wedged between the male connector pins and the female pin connector holes of the socket. Instead of one or more holding pins, a layer of an elastic material, such as rubber, can also partially or fully cover the part of the power plug housing or the male connector pins in order to form a wedge keeping the plug solidly connected to the socket. In all the above cases, the connection securing device can be permanently affixed to the rest of the power plug or can be removably coupled thereto.

The invention is particularly applicable to the marine industries, such as on-board vessels, platforms etc. However, it can be installed anywhere where power sockets are present. The power plug is described with one female connector at a female connector side of the power plug, but it is not restricted to only one female connector, an arrangement of a plurality of female connectors can also be an option. The power plug may therefore comprise multiple female connectors (e.g. on one or more sides of the power plug housing), and the arrangement on the male connector side of the plug may be as for the plug described with one female outlet. There may be no female connector present, in which case the power plug provides a secure connection for equipment, such as the gate/reader of a monitoring system, but cannot be used at the same time to connect additional equipment to a power source.

Brief description of the drawings

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams, wherein:

Figure 1 shows schematically and in perspective a prior art power plug with a jack;

Figure 2a shows schematically and in perspective a view of one embodiment of the power plug of the present invention;

Figure 2b shows schematically and in front view the female connector side of the power plug in Figure 2a;

Figure 3 shows schematically and in perspective an embodiment of a holding pin of the present invention;

Figure 4a shows a perspective view of the female connector side of the power plug with holding pins in the non-activated position;

Figure 4b shows a close-up of detail A shown in figure 4a;

Figure 4c shows a perspective view of the male connector side of the power plug with holding pins in the non-activated position;

Figure 4d shows a close-up of detail B shown in figure 4c;

Figure 5a shows a perspective view of the female connector side of the power plug with holding pins in the activated position;

Figure 5b shows a close-up of detail C shown in figure 5a;

Figure 5c shows a close-up of detail D shown in figure 5a; and

Figure 6 shows schematically and in perspective an external device, such as a gate, connected to the power plug of the present invention. Detailed description of embodiments

The following description of the exemplary embodiments refers to the accompanying drawings. The drawings illustrate exemplary embodiments of the invention configured to be integrated in building block systems. The exemplary embodiments disclosed in the drawings should not be understood as a limitation to the scope of protection of the invention, merely to illustrate certain aspects of the invention.

The same reference numbers in the different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further particular features, structures or characteristics may be combined in any suitable manner or in one or more embodiments.

Figure 1 shows schematically and in perspective a view of a power plug 100 with a jack according to the prior art. The power plug 100 comprises a housing with conductive pins 114 provided on a front or male connector side 110 of the housing for connecting the plug 100 to a power supply. Another side (in this case the rear side) of the housing is provided with jack units for connecting another plug. The body of the plug is provided with slots for eased handling when connecting and disconnecting the plug from a socket and an additional wire or cable 200 for connecting electrical equipment. The power plug 100 does not include any means by which a secure connection can be provided, and removal of the power plug 100 when additional equipment is removed from the jack units is likely. Figures 2a and 2b show schematically two views of one embodiment of the power plug 100 of the present invention. In figure 2a the power plug 100 is seen in perspective view, showing the female connector 120 of the plug from the female connector side 121 of the housing. The female side of the housing comprises a female connector body 122 and a plurality of female pin connector holes 124. The figure shows two holes, but any number of holes can be present. The configuration of the female connector will be dependent upon the current standard configuration for power plugs where the power plug is intended to be used. In Norway, for example, the Europlug with two holes is used and the female connector will need to be suitable for receiving such a plug. Further, the female connector side 121 is shaped to receive a standard power plug and may include one or more guide slots 126 for receiving corresponding ridges in the housing of the power plug 100 of a power consuming device. Guide ridges may also be included on the female connector side to be received within recesses or grooves in the power plug to be inserted. Again, the shape, size, and positioning of the various recesses and ridges will be designed to complement the configuration of a standard power plug and is not limiting.

On another side of the housing, in this case on the opposite side of the housing to the female connector side, is a male connector side 110. The male connector side comprises a male connector body 112 with a plurality of male connector pins 114 projecting out of its front face. As for the female connector, the figure shows two pins 114, but the number and configuration of the pins can be anywhere from one upwards and will generally be dependent upon the current standard or the type of socket present in the installation/vessel within which the power plugs will be fitted. The male and female connectors may be complementary in that they are designed to couple to standard sockets and standard plugs in a particular country, or on a particular vessel. The number of pins 114 of the male connector side may be equal to the number of holes 124 in the female connector side. The male connector side 110 may also comprise one or more guides 115 and recesses 117 for fitting to complementary recesses and guides in a standard socket. Again, the shapes of the guides, recesses, and pins or holes in the male and the female connector sides may be complementary. This way when the power plug 100 is plugged into a power socket, the female connector exposed on the rear side (and/or other sides) of the housing has the same configuration as the power socket and can be used in the same way to plug in and provide power to external devices. This way the power plug 100 sits between the socket and external device, but does not limit use of the socket to provide power to the device.

The female connector side of the power plug 100 may in some cases, such as due to regulatory restrictions, further comprise protective earth connections or earth conductors 118 protruding into the socket formed at the female connector side, the male connector side 110 can likewise comprise slots 117 to receive corresponding earth conductors in the socket wherein the power plug 100 is to be inserted. The power plug 100 may also comprise an electrical cable 200 extending from the power plug 100. The electrical cable 200 may extend to a power consuming unit 400 (not shown) or may provide power and/or data to an external unit. The additional unit may be a unit of a crew monitoring system, such as the gate or reader of a crew monitoring system as described above. The invention is not, however, restricted to including a cable 200 connecting other electrical equipment. It may also be an arrangement with a plurality of female connectors at the female side of the connector or may include wireless equipment for providing a wireless connection to other devices.

In order to ensure that the power plug 100 can be securely inserted into a socket, a connection securing device is included. The connection securing device may be permanently fixed to the power plug 100 or may be removably attached. The connection securing device may be configured to increase the frictional force which acts oppose removal of the power plug 100 from the socket when it is installed. The connection securing device may therefore be located so that when the power plug 100 is inserted into a socket, the connection securing device is sandwiched between the power plug housing (or in some cases the pins of the male connector portion) and the socket into which it is inserted. Preferably the connection securing device will be formed from a material which helps to increase the frictional engagement between the power plug 100 and the socket, such as an elastomeric material or a material having a rough surface. Use of an elastomeric material may also allow the connection securing device to be squeezed to some extent to change its shape once the plug is inserted, which may help to further increase the frictional force preventing accidental removal of the plug. In some cases, the connection securing device can comprise a layer of the friction enhancing material covering all or a part of the socket-facing surfaces of the housing (the parts of the housing located directly adjacent or contacting the socket when the plug is inserted), or an insert or projection attached to the socket-facing surfaces of the plug. Providing means for increasing the frictional engagement between the plug and socket is a particularly efficient way to maintain a secure connection because minimal adaption to the plug and no adaption to the socket is required. The size of the frictional force, and therefore how difficult it will be to remove the plug once installed can also be carefully and effectively controlled, and can be tailored to different situations by adapting the size and shape of the connection securing device and the material out of which it is made.

In one embodiment, the connection securing device of the power plug 100 comprises one or more holding pins 300. Two holding pins are shown in the figures, which helps to provide the secure connection, but one or more than two holding pins 300 spaced around the housing may be provided. In some cases, the holding pin 300 or holding pins 300 may be permanently attached to the housing of the power plug 100 such as by way of an adhesive, or they may be fixed to the housing using a clip or another mechanical fixing. Preferably, though, the holding pins 300 are able to be inserted through openings in the power plug housing in a way that allows them to be easily removed again through the openings if desired. The power plug 100 can be used normally if easy removal from the socket is desired for some reason, or the holding pins 300 can be inserted to provide the secure connection. This provides a level of flexibility to the system.

Figure 3 shows schematically and in perspective a view one possible embodiment of the holding pin 300. The or each holding pin 300 may comprise a long tail end 320 and a wider head end 310 as shown in the figure. An opening is provided in the power plug housing, extending towards the male connector side 110, through which the tail end 320 of a holding pin 300 can be inserted. The opening or openings can be accessed from the female connector side of the power plug 100 when the power plug 100 is plugged into a socket. This means that the secure connection can be provided without removal of the power plug 100 from the socket simply by inserting the holding pins 300 in through the openings. The head 310 can be dispensed with, but allows easier removal of the holding pin 300 from the opening and provides for easier insertion.

Once at least partially inserted into the opening, the holding pins 300 may be movable from a first position, representing a non-activated position, in which the holding pins 300 project out towards the female connector side 125 (as shown in figures 4a-d). Where the holding pin 300 includes a wider head end 310, the head 310 of holding pin 300 projects out at the female connector side 310. The holding pin 300 can be pushed into an inserted position by either providing a force on the head of the holding pin 310 or, if the holding pins 300 do not include a head 310, on the tail end 320 of the elongated pin 300 which projects out of the female connector side 120.

When an external device is plugged into the female connector side 120, or a force is applied manually, the holding pins 300 may be pushed in through the openings towards the male connector side 110. The holding pins 300 are thus slidable from the first into a second position (shown in figures 5a-c), which represents the activated position, in which at least a part of the tail 320 of the one or more holding pins 300 is positioned to contact the socket when the power plug 100 is inserted. A secure connection can therefore be provided by the increased frictional force between the holding pins 300 and the socket when a pulling force is applied to the power plug 100 in a direction away from the socket. The plug 100 is thus firmly inserted into the socket. The plug 100 can be removed if desired, but this will require more force than would be the case if the connection securing device, in this case the one or more holding pins 300, were not present, and may require use of an additional tool.

The holding pin or pins 300 can be movable within the opening(s) so that the activated position comprises a continuous series of positions in which the pin is pushed gradually further into the opening. The fully inserted position is shown in figures 5a-c. This feature of allowing for a gradual insertion of partial insertion of the holding pins 300 can be used to adjust the coefficient of friction between the power plug housing and the socket into which it is inserted. If a larger force is required to prevent removal of the plug when a power device is pulled out from the female connector, for example, the holding pins 300 can be inserted further into the housing towards the fully inserted position. If it is desired for removal of the power plug 100 from the socket to be easier, for example for safety reasons, the holding pin 300 or one or more of the holding pins 300 can be partially inserted. This provides an extremely flexible system. The holding pins 300 can also be configured to include a tapered end which will provide another level of control over the coefficient of friction between the holding pin and the socket. The pin may be thinner at the end furthest from the head 310, or the end configured to be inserted first through the opening. The thickness of the holding pin 300 may decrease continuously along the length of the holding pin 300 or a section of the holding pin 300, or may decrease in increments.

When in their second activated position, the holding pins 300, which are preferably made of an elastic material such as rubber, are wedged between the housing of the power plug on the male connector side and the opening of the socket into which the power plug 100 is inserted. The wedged holding pins 300 help to prevent accidental removal of the power plug 100. In order to detach the power plug 100 from the socket, the holding pins 300 may first need to be released and pulled back into the first position before the power plug 100 can be pulled out of the socket. In some cases, this can be done manually, but in other cases disengagement of the holding pin(s) from the second position to the first position may require the use of an additional tool or additional equipment, such as a flat screwdriver or a similar. In some cases, the power plug and the holding pins can be pulled out of the socket together. Generally, though, it is advantageous for the frictional force opposing removal of the power plug 100 from the socket (when the power plug is fully inserted into the socket and the connection securing device is in its activated position if applicable) to be large enough to prevent removal of the power plug 100 from the socket simply by manually pulling the power plug 100 away from the socket.

Figure 4a shows schematically and in perspective a view of an embodiment of the power plug 100 of the present invention. In figure 4a the holding pins 300 are in the first position as described above. Figure 4b shows a detail A from figure 4a representing a track or groove for the holding pin 119 on the male connector side 110 which is empty due to the holding pin 300 being in the non-activated position. The shape of the track or groove 119 may correspond to at least part of the shape of the tail 320 of the holding pin 300. The holding pin 300 in this case does not extend through the front or male connector side 110 of the housing and will not create additional friction between the housing and the socket when inserted. The invention is not restricted to including such a track or groove 119 along which the holding pin 300 can slide, and no track is also an option, in which case the holding pin 300 can simply extend through a hold in the housing or can be placed on the housing and removably fixed thereto using adhesive or a clip or similar. The track or groove 119 will support the holding pin 300 in its desired position and orientation and so does provide certain advantages. Figure 4c shows schematically and in perspective another view of the embodiment shown in figure 4a. Figure 4d shows a detail B from figure 4c illustrating the holding pin 300 in the first position as describe above.

Figure 5a shows schematically and in perspective a view of an embodiment of the power plug 100 of the present invention. In figure 5a the holding pins 300 are shown in the second, activated, position as described above. Figure 5b shows schematically and in perspective a detail C from figure 5a illustrating how the holding pin 300 sits within the track or groove 119 in the male connector side 110 and protrude outward of the power plug housing on a socket-facing side. Figure 5c shows schematically and in perspective a detail D from figure 5a. Here the holding pin 300 is in the second position, and the head 310 of holding pin 300 has been pushed so that it is flush with the base of the female connector socket. The figures each show two holding pins 300, but as mentioned above the apparatus is not restricted to two holding pins 300, and may comprise only one holding pin 300 or three or more holding pins 300.

Figure 6 shows schematically and in perspective an external device 400 connected to the power plug 100 of the present invention by means of an electrical cable 200. The length of the electrical cable 200 is customizable and thus adjustable. The external device 400 may be power consuming device 400.

The device 400 attached to the power plug 100 in the example shown in figure 6 may part of, or may be coupled to, one or more gates/readers of a crew monitoring system, such as the system described in WO2019/098841, which is hereby incorporated by reference. The crew monitoring system comprises at least a central controller, a plurality of gates, and a plurality of mobile units to be worn by personnel or attached to moveable equipment for tracking. The gates each represent a communications unit through which data from central controller and from mobile units located around the vessel can be routed. The gate may also be configured to process signals and select which data or alerts to send on to the central controller or to the mobile units depending on the processing. Each gate of the system can be provided with an antenna for receiving signals from the mobile unit, and in most cases the gate/reader will comprise a transceiver for also sending signals to the mobile units (such as an alert signal sent from a central controller through the powerlines).

The mobile units will generally comprise radio frequency tags and will therefore communicate with the gates via radio frequency, such as via Bluetooth ^R ™ Low Energy. At least identification information should be provided to the gate from the mobile unit. Sensors on the mobile unit can communication data relating to the health or activity of the crew member (temperature, heart rate, blood pressure, acceleration to detect a fall, triangulated position, ID, etc). The gates may, in some cases, produce an RF field which can activate a mobile base when a crew member enters the region within which the RF field is sufficiently strong.

The power cable 200 from the power plug 100 may provide power to the associated gate from the vessel’s powerlines via the socket, may provide a data connection through the powerlines, or may provide both a data connection and power to the gates through the powerlines via the socket. The data connection may be to other gates/readers plugged into power sockets in different areas of the vessel or may be to a central controller. The crew monitoring system can thus be retrofitted to an existing vessel with minimal change being required to the systems on board, in a way which will not limit use of the electrical sockets available on the ship. The specially designed power plug described above with its connection securing device ensures that use of the sockets will not risk disconnection of any part of the monitoring system, which may be crucial in terms of crew safety.

Table 1