GB2219446A

GB2219446A - Facilitating disengagement of electrical plug

Info

Publication number: GB2219446A
Application number: GB8911426A
Authority: GB
Inventors: Batia Sofer; Carmel Sofer
Original assignee: RIVIERA ENTERPRISES Ltd
Current assignee: RIVIERA ENTERPRISES Ltd
Priority date: 1988-06-01
Filing date: 1989-05-18
Publication date: 1989-12-06
Also published as: IL86594A0; GB8911426D0; ES2012009A6; ZA891467B; AU3516689A

Abstract

A plug comprising a housing 20 configured to define a gripping surface 32, and at least one electrically conducting pin 26 extending generally parallel to a longitudinal axis and arranged for engagement with a complementary socket, has means for facilitating manual disengagement of the pin 26 from the socket comprising a pusher element arranged for movement generally parallel to the longitudinal axis and having a socket contact surface 24 at one end and a user contact surface 16 at an opposite end. Easy disengagement of the plug from the socket may be achieved by gripping the surface 32 of the housing with the fingers and simultaneously exerting an axial force on the pusher element by engagement of the user contact surface 16 with the thumb, causing the socket contact surface to push against the socket as the housing is pulled away from the socket. <IMAGE>

Description

FIELD OF THE INVENTION The present invention relates generally to electrical plugs, and more particularly to electrical plugs which may be safely and easily manually connected to and disconnected from a complementary socket.

BACKGROUND OF THE INVENTION Electrical appliances in homes, offices, factories and public facilities are generally connected to an electric supply by means of a plug, attached to the appliance cable, which is manually inserted into a wall socket or into a socket attached to the end of a cable. After use, the appliance is often disconnected by pulling the plug out of the socket, there being many reasons for doing so, among them prevention of leakage current, prevention of inadvertent operation, repair or adjustment, and freeing the socket for use with another appliance.In practice the act of engagement or disengagement of an electric plug can be surprisingly difficult, particularly for elderly and handicapped persons, in that the act of disengagement requires considerable force, often due to misalignment of the plug pins relative to the socket recesse: A further disadvantage of existing standard electric plugs is that sockets are often not firmly anchored in the wail surface and when force is applied to a plug connected thereto, with the object of disengaging the plug, the wall socket may become partially or totally disengaged from the wall. To prevent socket disengagement, it is possible to use one hand to press the socket to the wall while simultaneously pulling out the plug with the other.However, this method is relatively difficult to effect, particularly for elderly and handicapped persons, and is also hazardous as the hand pressing on the socket may inadvertently come into contact with the plug pins while they are partially withdrawn, with consequent risk of electric shock.

Plugs which attempt to overcome the problem of socket disengagement from the wall by providing a member which communicates with the socket or presses it against the wall in the course of manual disengagement of the plug are known in the art. U.S. Patents 2,688,734; 3,475,715; 3,926,424; 4,045,106 and 4,326,763 and German DT 2,937,035 describe spring loaded plugs which are self-ejecting as a result of a spring action. These plugs suffer from the disadvantage of requiring considerable force in order to effect insertion, which makes them difficult for a person of average strength to use. A fortiori, such plugs are particularly unsuited for use by elderly and physically handicapped persons.

A further disadvantage of spring loaded plugs is that repeated use thereof can damage and even break plastic socket covers presently in use, as a result of repeated impingement of the spring loaded element of the plug against the socket.

Yet another disadvantage is that plugs which are forcibly ejected from a socket as a result of strong spring action could impinge upon adjacent objects such as the hand of the person effecting disengagement, with consequent risk of discomfort or injury.

It is noted that the force required in order to disengage a plug varies considerably among wall sockets presently in use. Therefore, a particular spring loaded plug may not be disengageable from each and every wall socket, unless the spring provided therein is particularly strong, in which case the possible undesirable consequences, described hereinabove, of the particularly strong spring action constitute a relatively serious drawback.

Still another disadvantage is that many spring loaded plugs are ejected by pressing a button provided on a side of the plug. The button is not always easily accessible, particularly when several plugs are inserted in a multiple socket.

SUMMARY OF THE INVENTION It is one of the objects of the present invention to overcome the disadvantages of prior art electrical plugs and to provide an electrical plug which can be safely and easily connected and disconnected using relatively little force and using only one hand.

There is thus provided in accordance with a preferred embodiment of the present invention an electrical plug comprising a housing configured to define a finger-engageable gripping surface, at least one electrically conducting pin mounted in the housing, extending generally parallel to a longitudinal axis and arranged for engagement with a complementary socket, and means for facilitating manual disengagement of the at least one electrically conducting pin from the socket and comprising a user engageable pusher element arranged for movement generally parallel to the longitudinal axis and defining a socket contact surface at one end for engagement with the socket and a user contact surface at an opposite end for engagement by a user, whereby enhanced disengagement of the plug from the socket may be achieved by a user by gripping the finger-engageable gripping surface of the housing with his fingers and simultaneously exerting an axial force on the pusher element by engagement of the user contact surface with his thumb, causing the socket contact surface to push against the socket as the housing is pulled away from the socket.

Further in accordance with a preferred embodiment of the present invention, the at least one pin is fixedly mounted with respect to the housing.

Still further in accordance with a preferred embodiment of the present invention, the pusher element comprises an elongate element.

Additionally in accordance with a preferred embodiment of the present invention, the pusher element is formed of an electrically insulative material.

Additionally in accordance with a preferred embodiment of the present invention, the gripping surface comprises a curved surface.

Further in accordance with a preferred embodiment of the present invention, the gripping surface comprises a plurality of adjacent surfaces.

Still further in accordance with a preferred embodiment of the present invention, the socket contact surface has a cross sectional area smaller than the cross sectional area of another part of the pusher element.

Further in accordance with a preferred embodiment of the present invention, the thumb contact surface has a cross sectional area greater than the cross sectional area of another part of the pusher element.

Additionally in accordance with a preferred embodiment of the present invention, the pusher element has a uniform cross section.

Further in accordance with a preferred embodiment of the present invention, the pusher element comprises a hollow element which at least partially surrounds at least one of the at least one pins when the pusher element is in an extended orientation relative to the housing.

There is also provided in accordance with a preferred embodiment of the present invention an electrical plug including a housing, at least one electrically conducting pin for interengagement with a complementary socket, and means for facilitating manual release of the plug from the socket, the facilitating means including a slidable member being slidable relative to the at least one pin, the slidable member including a surface arranged to contact and apply pressure to a face of the socket while the pin is inter-engaged therewith, and manipulating means for effecting the relative movement between the conducting pin and the member to cause disengagement of the pin from the socket while the slidable member is in contact with the socket face, the interaction of the manually applied force and counterforce being operative to cause the housing to move relative to the member in a direction opposite to the direction of application of the manually applied force and consequently to disengage the plug from the socket solely as a result of the manual force exerted thereon.

According to a preferred embodiment of the present invention, the housing includes at least one abutment surface extending in a direction traversing the direction of movement of the slidable member, for facilitating gripping of the housing by a user and the exertion by the user of pressure on the manipulating member simultaneously with a counterforce whereby the housing is movable relative to the member in a direction opposite to the direction of application of the pressure solely by the manual force exerted thereon.

Further in accordance with a preferred embodiment of the present invention, the electrical plug is configured to allow the at least one abutment surface of the housing to be gripped with at least one finger and to allow a thumb to be used to apply force on the manipulating means.

Further in accordance with a preferred embodiment of the present invention, the housing includes a front surface from which the pin extends, a back surface, a top surface above the pin and a bottom surface below the pin, the manipulating means extending from the back surface of the housing in a direction substantially opposite to that of the pin.

Additionally in accordance with a preferred embodiment, the abutment surface includes a ledge disposed substantially normal to the top surface and flush with the back surface.

Still further in accordance with a preferred embodiment of the present invention, the abutment surface includes a surface of a tubular projection. Preferably, the tubular projection extends at an angle of less than 180 degrees with respect to the bottom surface and less than 90 degrees with respect to the back surface for receiving an electrical cable.

Further in accordance with a preferred embodiment of the present invention, the top surface is formed with a plurality of ridges serving as an abutment surface.

Further in accordance with a preferred embodiment of the present invention, the bottom surface is formed with 2 plurality of ridges serving as an abutment surface.

Since, as noted hereinafter, some European countries have wall sockets with a projecting earth pin, the term socket face as used herein is intended to include a socket face or extensions thereof or depressed recessed surfaces thereof such as the head of the projecting earth pin or the inner central face of a telephone plug socket.

Additionally, in accordance with a preferred embodiment of the present invention, the electrical plug is configured for use with wall sockets having a projecting earth pin, the electrical plug comprising a slidable member configured to contact and apply pressure on the head of the projecting earth pin.

In accordance with a further preferred embodiment of the present invention, the electrical plug is configured for use with telephone sockets, the plug comprising a slidable body configured to contact and apply pressure on the inner central face of the socket contact.

In accordance with still a further preferred embodiment of the present invention, the plug is configured for use with a television central antenna.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: Fig. 1 is a side elevation of an electrical plug constructed and operative in accordance with a first preferred embodiment of the present invention; Fig. 2 is a plan view of the lower part of the embodiment of Fig. 1; Fig. 3 is an exploded view of the embodiment of Fig. 1; Fig. 4 is an exploded view of an electrical plug constructed and operative in accordance with a second preferred embodiment of the present invention; Fig. 5 is a side cross-sectional view of an electrical plug constructed and operative in accordance with a third preferred embodiment of the present invention; Fig. 6 is a top cross-sectional view of the embodiment of Fig. 5;; Fig. 7 is an exploded view of the embodiment of Fig. 5; Fig. 8 is a cross-sectional elevation of a plug in a disengaged position, the plug being constructed and operative in accordance with a fourth preferred embodiment of the present invention; Fig. 9 is a cross-sectional elevation of an electrical plug suitable for use with a European-style socket, the plug being constructed and operative in accordance with a fifth preferred embodiment of the present invention; and Fig. 10 is a cross-sectional elevation of an electrical plug suitable for use with a telephone socket, the plug being constructed and operative in accordance with a sixth preferred embodiment-of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Reference is made to Figs. 1-3 which illustrate an electrical plug constructed and operative in accordance with a first preferred embodiment of the present invention. The plug is connectable to an electric cable via connecting means 34 which defines part of the cable entry, thereby engaging the cable. The plug further comprises a generally cylindrical housing portion 20 secured at its bottom to a base plate 22 by screws br any other suitable means, and a planar portion 32, typically disposed substantially parallel to base plate 22. Planar portion 32 is preferably integrally formed with the cylindrical housing portion 20. A plurality of conducting pins 26 are supported onto base plate 22 by conventional means and protrude outward therefrom.

The perimeter of planar member 32 typically somewhat exceeds the perimeter of housing portion 20 so that at least a portion of the edge of planar member 32 protrudes beyond the edges of housing portion 20.

An elongate slidable pusher member 24 comprises a protruding portion 21 defining a thumb-engageable surface 16.

Portion 21 protrudes through an aperture 14 in planar member 32 when the plug is engaged in an electrical socket and may be substantially flush with the outer surface of planar member 32 when the plug is disengaged from the socket. Slidable member 24 also comprises an electrical socket contacting planar portion 25, preferably being disposed substantially parallel to surface 16.

Planar portion 25 may protrude through an aperture 30 in base plate 22 when the plug is being disengaged from the socket and may be substantially flush with the outer surface of base plate 22 when the plug is engaged in the socket. According to a preferred embodiment, protruding portion 21 is integrally formed with slidable member 24.

According to a preferred embodiment, slidable member 24 comprises a first elongate hollow portion 40 defining a conduit 12 along its length. Conduit 12 is typically sealed at one end by planar portion 25. Protruding portion 21 comprises a second elongate portion 42, each of elongate portions 40 and 42 being of generally uniform cross section, the dimensions of the cross section of portion 40 preferably being such as to allow portion 40 to slide through aperture 30 but not through aperture 14, and the dimensions of the cross section of portion 42 preferably being such as to allow portion 42 to slide through aperture 14 but not through aperture 30.

Preferably, a hollow elongate portion 10 is integrally formed with planar member 32 and protrudes from an inner surface 41 thereof. A light and relatively weak compression spring 11 may be provided, disposed interiorly and coaxially relative to hollow elongate portion 10. A rod 13, typically mounted on that face of portion 25 which communicates with the interior of conduit 12, is provided within conduit 12, being disposed generally coaxially therewith. The spring, the rod 13, the elongate portion 10 and the conduit 12 are configured and arranged so that, when the plug is disengaged from the electrical socket, the spring maintains hand-contacting surface 16 in a generally fixed, typically flush, orientation relative to the outer surface 33 of planar member 32.

When the plug is engaged in the wall socket, elongate portion 10 engages conduit 12, rod 13 compresses the spring and surface 16 protrudes relative to outer surface 33. It is appreciated that the spring arrangement described above, as well as similar spring arrangements described in connection with other embodiments hereinbelow, are not an essential feature of the present invention.

hlhen it is desired to insert the plug into a socket, mechanical pressure, typically manual pressure, is applied to planar member 32 and/or to housing portion 20, in the direction of arrow 60, so as to induce pins 26 to enter the socket (not shown) and to bring socket contacting surface 25 into engagement with the outer face of the socket. Further pressure on planar member 32 may result in full entry of the pins 26 into the socket, and simultaneous sliding motion of member 24 relative to planar member 32 in a direction opposite that of arrow 60, causing protrusion 21 to protrude from planar member 32 through aperture 14. The plug is now in its engaged position.

To disengage the plug from the socket, a user brings his thumb, preferably, into contact with surface 16, while simultaneously gripping housing portion 20 and/or planar member 32, preferably with a finger or fingers, such as the index and/or middle fingers. The user applies pressure to surface 16 in the direction of arrow 60, while simultaneously exerting a counterforce on planar member 32. The counterforce overcomes any holding force applied by the wall socket to conducting pins 26 and disengages the plug from the socket. Pressure of slidable member 24 on the wall socket, as a result of user-applied pressure on surface 16, is operative to prevent the socket from becoming disengaged from the wall.Since the pressure applied by, preferably, the thumb is normally continuous over time, unlike the force applied by heavy duty springs known in the art, no damage is normally caused to the socket.

Slidable member 24 is, preferably, attached to housing portion 20 during production in a manner which, while allowing protruding portion 21 to slide relative to aperture 14, generally does not allow member 24 to be entirely disengaged from housing portion 20. Thus if the plug is disassembled by the user for wiring purposes, the plug, excepting the pins, separates into only two components, the first comprising housing portion 20 and slidable member 24, and the second comprising base plate 22.

Unless otherwise specified herein, all elements of the plug, apart from pins 26 which are formed of a suitable conducting material and may comprise standard conducting pins, are formed of suitable electrical insulating materials, such as plastic.

In Fig. 4 there is seen a second preferred embodiment of the present invention in exploded view, similar numerals being used to designate similar parts already discussed with reference to Figures 1-3. The plug constructed in accordance with this embodiment is configured to mate with European style sockets having "spring earth contacts". The plug is similar to that illustrated in Figs. 1-3 with the following exceptions: preferably, there are provided guiding rails 82, being integrally formed with, and disposed generally perpendicularly to, base plate 22. Rails 82 are configured to engage top and bottom arms of an earth contact 17 (shown disassembled in a solid line and assembled in a broken line). An elongate aperture 80 is provided along at least a portion of the length of elongate member 24.During production, the upper arm 15 of earth contact 17 is passed through aperture 80 in member 24, prior to joining member 24 to base plate 22. According to a preferred embodiment, once member 24 is inserted into opening 30 and earth contact 17 is engaged with rails 82, base plate 22, slidable member 24 and earth contact 17 become a single unit not easily disengageable.

Simultaneous pushing on surface 16 and pulling on planar member 32 allows member 24 to slide relative to housing portion 20 while the plug is being disengaged. Elongate opening 80 is of a length which ensures that earth contact 17 will not interfere with the movement of member 24. According to a preferred embodiment, a relatively weak spring (not shown) is mounted onto earth contact 17, being disposed generally parallel to and equidistant from the upper and lower arms thereof. hEen the plug is assembled, the spring is arranged so as to be disposed along at least a portion of the length of elongate aperture 80 and serves to maintain slidable member 24 in a generally fixed orientation relative to the housing portion 20 when the plug is disengaged.

Earth contact 17 is typically formed of a metal with somewhat elastic properties, such as brass, in order to facilitate snug contact with the earth contact in the wall socket.

Referring now to Figs. 5-7 there is seen a plug, shown in a disengaged orientation, constructed and operative in accordance with a third preferred embodiment of the present invention, and comprising a housing portion 120, a base plate 122, a slidable elongate pusher member 124 and several conducting pins 26.

According to a preferred embodiment, housing portion 120 comprises a first portion 140 for engagement with a wall socket and a second portion 136 for engagement with an electrical cable (not shown), the two portions 136 and 140 preferably angled with respect to one another by an angle of o o approximately 90 - 150 Surfaces 131 and 133 of housing portion 120 preferably serve as abutment surfaces to be gripped by the index and middle fingers during disengagement of the plug and are typically formed with ridges 132 and 134, respectively, thereupon.

Alternatively or in combination, surface 138 of portion 136 can serve as an abutment surface to be gripped by the middle finger during disengagement of the plug. Alternatively or in combination, as shown in Fig. 7, the extremity of portion 136 adjacent portion 140 may protrude relative to the extremity of portion 140 adjacent portion 136, thereby defining a ledge 135 to facilitate handgrip.

As in the previous embodiments, slidable member 124 slides back and forth with respect to the housing portion 120, defining engaged and disengaged positions of the plug. 'Then the plug is engaged, one surface 137 of member 124 may contact the wall and an opposite surface 116 may protrude relative to portion 136.

For safety reasons, member 124 is preferably configured and arranged to sheath a substantial portion of the length of pins 26 when the plug is disengaged, typically leaving only 2-3 mm of their length exposed in order to allow a user to guide the plug into the socket, thus generally preventing contact between pins 26 and the fingers of the user while the plug is partially engaged to the socket. Specifically, the wall-contacting surface 137 of member 124 may be configured with slits 139 corresponding in number and in location to the number and location of pins 26.

A light duty compression spring 28 is preferably provided resting within a suitably configured elongate aperture 128 provided along at least a portion of the length of elongate member 124. Spring 28 serves to maintain member 124 in a fixed position relative to housing portion 120 when the plug is disengaged. The plug is assembled by any suitable means, such as by a screw 121 threaded through aperture 141, aperture 128 and socket 123. Preferably, once slidable member 124 is assembled into housing portion 120 during production, it becomes part of the housing portion 120 and is not easily separated. Therefore, when the plug is disassembled by the user for wiring purposes the plug separates into only two parts.According to a preferred embodiment, slidable member 124 may be snapped into an upper portion 143 of first housing portion 140, such that slidable member 124 can slide relative to housing portion 120 but cannot be easily disengaged therefrom.

Fig. 8 shows a plug in a disengaged orientation, constructed and operative in accordance with a fourth embodiment of the invention. This embodiment is generally similar to the embodiment of Figs. 1 - 3 but, as in the embodiment of Fig. 7, member 24 is configured to sheath most of the length of pins 26 so as to generally prevent hand-pin contact when the plug is partially engaged. The plug housing is formed of a handcontacting portion 20 and a wall-contacting portion 22 joined by a hinge 133. Hinge 133 serves primarily as a pivot axis allowing the plug to be opened for wiring purposes but preferably also protrudes somewhat from the surface of the plug and thereby serves to facilitate gripping of the plug by the user.

Fig. 9 illustrates a plug, shown in an engaged position, constructed according to a further embodiment of the invention, and being particularly configured to mate with certain European wall sockets in which a projecting earth pin and at least two recessed power supply contacts are provided. During disengagement, force is applied to the earth pin rather than to the surface of the wall socket. Accordingly, the plug is provided with at least two projecting pins 26 configured to enter the at least two power supply contacts provided in the wall socket. A recess 48 is configured to allow penetration of the projecting earth pin protruding from the wall socket.

During disengagement, a first extremity 230 of slidable elongate member 24 is disposed interiorly of recess 48, as is the earth pin protruding from the wall socket, and a second extremity 232 of member 24 protrudes relative to surface 32 of housing portion 20. Preferably, a light, relatively weak compression spring 28 is provided which serves to maintain member 24 in a fixed position relative to housing portion 20 when the plug is in its disengaged position. Alternatively, spring 28 may comprise a light relatively extension spring.

The edges of surface 32 typically jut outward relative to those surfaces of housing portion 20 which are generally perpendicular to surface 32, as explained above with reference to Fig. 1. Disengagement of the plug from the socket is effected by gripping surface 32 with the fingers, while simultaneously applying thumb pressure to extremity 232 of member 24, causing member 24 to contact the earth pin (not shown), and to apply pressure thereto in the direction of arrow 228. The effect of the user-applied pressure on the earth pin in the direction of the wall is to generally prevent disengagement of the socket from the wall, while pins 26 are simultaneously withdrawn from the socket.

Fig. 10 shows a plug constructed and operative in accordance with still a further preferred embodiment of the invention, being particularly configured to mate with a telephone socket in which a center pin is provided. Recess 48 is configured to receive the telephone socket center pin. A single stepped pin 50 carries at least two insulated electrical contacts. As in the embodiment of Fig. 9, when the plug is being disengaged, member 24 contacts the telephone socket center pin (not shown) within recess 48 and applies pressure thereupon in the direction of the wall, thus preventing disengagement of the socket from the wall. As in Fig. 9, a relatively weak compression or extension spring 28 is optionally provided.

With reference to all the above embodiments, it is believed to be desirable for that surface of the slidable member which contacts the wall socket to be of relatively small dimensions, and for that surface of the slidable member upon which wall-directed pressure is applied by the user's thumb to be of relatively large dimensions, in order to create concentration of a relatively large force on a relatively small area of the wall socket.

It will be appreciated that the various preferred features of the plug shown and described hereinabove with respect to certain embodiments of the plug may in fact be equally applicable in other embodiments. Description of a particular feature in connection with only a subset of the embodiments described hereinabove is intended only to facilitate understanding and not to limit the applicability of that feature to the particular subset of embodiments.

It is further appreciated that a plug constructed and operative in accordance with the present invention can be configured to mate with wall sockets of substantially any configuration, such as, but not limited to, the wall socket of a television central antenna, and can also be configured for use with electrical sockets not engaged in a wall.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the invention is defined only by the claims which follow:

Claims

CLAIMS 1. An electrical.plug comprising: a housing configured to define a finger-engageable gripping surface; at least one electrically conducting pin mounted in the housing, extending generally parallel to a longitudinal axis and arranged for engagment with a complementary socket; and means for facilitating manual disengagement of said at least one electrically conducting pin from the socket and comprising:: a user engageable pusher element arranged for movement generally parallel to said longitudinal axis and defining a socket contact surface at one end for engagement with the socket and a user contact surface at an opposite end for engagement by a user, whereby enhanced disengagement of the plug from the socket may be achieved by a user by gripping the fingerengageable gripping surface of the housing with his fingers and simultaneously exerting an axial force on the pusher element by engagement of the user contact surface with his thumb, causing the socket contact surface to push against the socket as the housing is pulled away from the socket.
2. An electrical plug according to claim 1 and wherein said at least one pin is fixedly mounted with respect to said housing.
3. An electrical plug according to either of the preceding claims and wherein said pusher element comprises an elongate element.
4. An electrical plug according to any of the preceding claims and wherein said pusher element is formed of an electrically insulative material.
5. An electrical plug according to any of the preceding claims and wherein said gripping surface comprises a curved surface.
6. An electrical plug according to any of the preceding claims and wherein said gripping surface comprises a plurality of adjacent surfaces.
7. An electrical plug according to any of the preceding claims and wherein said socket contact surface has a cross sectional area smaller than the cross sectional area of another part of said pusher element.
8. An electrical plug according to any of the preceding claims and wherein said thumb contact surface has a cross sectional area greater than the cross sectional area of another part of said pusher element.
9. An electrical plug according to any of the preceding claims and wherein said pusher element has a uniform cross section.
10. An electrical plug according to any of the preceding claims and wherein said pusher element comprises a hollow element which at least partially surrounds at least one of said at least one pins when the pusher element is in an extended orientation relative to the housing.
11. An electrical plug substantially as shown and described hereinabove.
12. An electrical plug substantially as illustrated in any of the drawings.