CHARGING UNIT FOR CORDLESS APPLIANCES

Abstract: A connection system for so-called "cordless" electrical appliances is designed to permit a substantial degree of freedom in the placement of the appliance proper onto the base from which it takes its electrical supply. In a first embodiment (Fig. 1), a plug and socket connector is employed, the plug being coupled to the appliance proper and the socket to the base, and the socket incorporates a pair of pivoting shutter elements which are arranged to be pivoted apart as the plug is inserted into the socket, the plug at the same time unlocking a shutter locking arrangement; this arrangement permits insertion of the plug into the socket throughout almost a full 360 of relative rotation of the plug relative to the socket. A second embodiment (Fig. 7) employs but a single shutter element in the socket part and the shutter is arranged to jam and prevent access to the socket if it is not uniformly depressed; this arrangement permits a full 360 of rotation of the plug relative to the socket.

Description: Charging unit for cordless appliances Field of the Invention: This invention generally concerns improvements relating to electrical appliances and connectors therefor and more particularly, though not exclusively, relates to an improved connection system for so-called "cordless" electrical appliances in which power is supplied to an appliance proper via a base unit coupled to the electrical supply. Examples of such cordless appliances are electric kettles and hot water jugs and electric smoothing irons, but the connection system of the present invention is not limited to use in such appliances and, moreover, is not limited to use with cordless appliances. Background of the Invention: Cordless appliances generally have a s.ocket outlet provided in or on the base unit and a mating connecting inlet in or on the appliance proper, and generally require fairly precise alignment between these two parts in order to connect the appliance proper to the base. The connecting inlet of the appliance proper commonly comprises a set of male terminal pins which are adapted to mate with a complementary set of female terminals provided in a shrouded portion of the base unit, and the base unit terminals are commonly provided in an upstand formed on the base unit and adapted to locate in a generally complementary recess formed in the body of the appliance proper for providing the degree of alignment between the respective parts that is necessary to ensure correct mating of the two parts of the connection system. An exemplary cordless connection system of this kind is disclosed in our British Patent Application No. 9102099.0 (GB-A-2 241 390) . An alternative system in which the terminal pins are provided in the base unit and complementary spring terminals are provided in the appliance proper is disclosed in our British Patent Application No. 9018502.6 (GB-A-2 236 220) . The requirement that the appliance proper and the base unit should mate with each other only in a predetermined single orientation is a restriction upon the freedom of the appliance designer to achieve the desired product form and also presents some inconvenience to users of the appliance. It has previously been recognized that an excessive requirement for alignment of the appliance proper with the base unit is undesirable and in British Patent No. GB-B-2 221 104 (Strix Ltd.) there is disclosed a cordless connection system which is generally conventional but is adapted to accommodate a degree of initial misalignment of the appliance proper with the base. However, prior to the present invention (insofar as we are aware) no attempt has been made -to design a cordless connection system which does not, or at least substantially does not, require alignment of the respective parts. Objects and Summary of the Invention: It is the principal object of the present invention to provide a connection system for cordless electrical appliances which overcomes or at least substantially reduces the problems of the prior art as discussed hereinbefore. A more particular object of the present invention is to provide a cordless connection system which does not, or at least substantially does not, require alignment of the respective parts. According to a first aspect of the present invention a female connector part for a cordless connection system has a plurality of movable shutter elements having surfaces which together define a concavity for receiving a male connection part, and a releasable locking member holding said plurality of shutter elements in closed condition until released, the arrangement being such that the insertion of an appropriate male connector part into said cavity serves to release said locking member and to urge said shutter elements open for enabling electrical terminals of said male connector part to engage conductors provided in the female part. The concavity defined by the surfaces of the shutter elements may be circular in plan view, that is in a direction transverse to the normal direction of insertion of the male connector part therein, and may have a generally conical or frusto-conical form with rectilinear generatrices which could alternatively be curved either convexly or concavely if desired to give a variation of the insertion force required to introduce the male connector part against spring biassing of the shutter elements. By appropriately forming the terminals of the male connector part and the co-operating conductors of the female part, the male part may be arranged to be capable of mating with the female part throughout substantially a 360° range of alignment rotation of ' the male part with respect to the female. In an embodiment of the abovementioned first aspect of the present invention, which will be described in detail hereinafter, there are two shutter elements each of which has a surface portion defining one half of a circular, frusto-conical concavity, and the two shutter elements are pivotally mounted so that in the closed condition of the elements the aforementioned surface portions face each other. On their undersides, that is to say on the sides of the shutter elements opposite to the surfaces thereof wherein said hemi-concavities are formed, the shutter elements are each provided with a protrusion such as to define with the corresponding protrusion formed on the other shutter, when the shutters are closed, a short annular spigot. The locking member is a generally cup-shaped element having a base and an upstanding annular wall, and in the locked condition of the shutter elements the cup-shaped element is biassed towards the spigot defined by the closed shutter elements and its upstanding annular wall closely surrounds the spigot and prevents the shutter elements from opening. The male connector part has three in-line terminal pins and the central pin is longer than the two side pins so that, when the male connector part is inserted into the concavity of the female part, the locking member is displaced by the tip of the central terminal pin thereby freeing the spigot formed on the shutter elements from its upstanding annular wall and enabling the shutter elements to be pivoted apart by interaction with the pins of the male connector part. The locking member in the above described embodiment of the invention itself constitutes a spring-loaded connector which co-operates with the central pin of the male connector part. In an alternative arrangement, however, the locking member could itself be formed as a shutter comprised of one or more parts arranged to be disturbed by the central terminal pin of the male connector part for admitting the pin to contact with a separate spring connector provided in the female connector part. In a non-earthed system, for example a double- insulated system, the central pin of the male connector part could be formed of electrically insulating material in which case the locking member would itself constitute neither an electrical conductor nor a shutter to admit the pin to a conductor, and electrical energy would be transferred through the connector via the two side pins of the male connector part. Alternatively, in a non-earthed system, the two side pins could be made common (i.e. electrically coupled together) and the central pin could provide an electrical connection function. As abovementioned, in an earthed connector system as described the central pin of the male connector part could comprise an earth pin and might co-operate either with the locking member itself or with an earth conductor provided in the female connector part and shuttered from the earth pin by the locking member. In this case, the conductors provided in the female connector part for co-operation with the two side pins of the male connector part might comprise respective arcuate spring conductors; there would be a gap between the ends of such conductors to provide electrical isolation of the live and neutral connections and, to preclude the possibility of the male connector part being inserted in an orientation such as would lead to such gaps being bridged, at least in part, by respective ones of the side terminal pins, means might be provided in the gaps such as to direct the entering pins to one side or the other of the gap. For a non-earthed system utilizing the central pin of the male connector part as one pole, the electrical conductor provided in the female connector part for co-operating with the other (commoned) pins of the male connector part might comprise an annulus providing a full 360° possibility of relative rotational orientation between the two connector parts. In use of such a connector system with a cordless electrical appliance, the female connector part would normally be provided in or on the base unit and the male connector part would normally be provided on the appliance proper; however, the female connector part could be provided on the appliance proper and the male part provided in or on the base unit provided that shuttering was provided for the male terminal pins. The external form of the male and female connector parts could advantageously be shaped to facilitate mating of the two connector parts by guiding them together once they were imprecisely engaged with each other. The use of a female connector part incorporating two pivotally mounted shutter elements arranged to be pivoted apart by an incoming male connector part, as described in the foregoing, may not always enable ready mating of the male and female connector parts to be achieved within a full 360° of rotational orientation of the two parts. We have accordingly developed an alternative connection system which, in accordance with a second aspect of the present invention, overcomes this problem. Our alternative connection system includes a shutter having rotational symmetry which is arranged to be opened by movement in relation to co-operating parts in a predetermined direction, such movement being possible only if the shutter has a predetermined disposition relative to at least one co-operating part and the shutter and/or such co-operating part(s) being configured to permit alternative disposition of the shutter. ,With such a shutter provided in one part of a two part complementary connector system, the other part would be provided with means to ensure displacement of the shutter with the shutter held in the requisite disposition for opening of the same. More generally, according to the abovementioned second aspect of the present invention there is provided an electrical connector comprising a plug part and a socket part, the plug part being insertable into the socket part by relative movement between the two parts in a predetermined direction irrespective of the relative rotational orientation of the two parts transversely to said predetermined direction, and a shutter being provided in the socket part and being displaceable therein for admitting the plug part only if the shutter has a predetermined disposition, the shutter being capable of adopting alternative dispositions within the socket part, and the plug part being formed so as to hold the shutter in said predetermined disposition so long as the plug part and socket part are approached to each other in said predetermined direction. In an exemplary embodiment of such second aspect of the present invention, which also will be described in detail hereinafter, the shutter includes a circularly- cylindrical part which is axially displaceable, against a spring bias, within a second circularly-cylindrical part so long as the axes of the two cylindrical parts have a predetermined relative disposition, namely they are coaxial or very nearly so. The shutter and the second cylindrical part are, however, constructed so as to permit the shutter to be tilted and it is arranged that the shutter then cannot be opened by being displaced into the second cylindrical part. The shutter and the second circularly-cylindrical part are both incorporated into one connector part of the system, and the other part includes a circularly-cylindrical part adapted for displacing the shutter in the requisite direction while holding it in the requisite disposition. Any effort to open the shutter which does not simultaneously ensure that it is held in the requisite opening disposition will cause it to tilt thereby preventing it from being opened. The two connector parts, so long as they are brought together in the requisite degree of coaxial orientation for effecting opening of the shutter, are capable of being connected together within the full 360° range of relative rotational orientation and there is no requirement to effect rotary alignment of the two parts. Having thus briefly described first and second aspects of the present invention, the invention, in accordance with a third aspect thereof, can be summarized as providing a shuttered electrical connection system in or for a cordless electrical appliance, the connection system in use permitting the appliance proper to be operatively coupled to its base throughout substantially 360° of relative rotational orientation between the respective parts or, more preferably, throughout a full 360° of relative rotational orientation. The foregoing and further aspects of the present invention are set forth in the appended claims and will best be understood from consideration of the following detailed description of exemplary embodiments of the invention which are illustrated in the accompanying drawings. Description of the Drawings: Figure 1 is an exploded full size perspective view of an exemplary female connector part constructed and arranged in accordance with the aforementioned first aspect of the present invention; Figures 2A, 2B and 2C are perspective views showing to an enlarged scale 2.5 times that of Figure 1 the assembly of the female connector part shown in Figure 1; Figures 3A to 3F are perspective, plan and elevation views to an enlarged scale 2.5 times that of Figure 1 of a body part of the female connector part shown in Figure i; Figures 4A to 4E are perspective, plan and elevation views to yet a further enlarged scale 5.0 times that of Figure 1 of a shutter element of the female connector part shown in Figure 1; Figures 5A to 5E are perspective, plan and elevation views to an enlarged scale 2.0 times that of Figure 1 of spring connector parts of the female connector part of Figure 1; Figures 6A to 6D are, respectively, a perspective view to an enlarged scale 10.0 times that of Figure 1 of a locking member of the female connector part of Figure 1 and plan and elevation views to an enlarged scale 2.5 times that of Figure 1 of the locking member; Figure 7 is an axially exploded view of an exemplary connector socket part constructed and arranged in accordance with the aforementioned second aspect of the present invention; Figure 8A shows the connector socket part of Figure 7 in assembled condition and with its component parts shown in enlarged sectional side elevation view, and Figure 8B shows a sectional side elevation view of an exemplary connector plug part adapted to be mated with the socket part of Figure 8A; Figure 9 shows the connector socket and plug parts of Figures 8A and 8B in engaged condition; Figure 10 is a view similar to Figure 8A and illustrating the operation of the shutter mechanism incorporated into the connector socket part; and Figure 11 is a perspective view of the connector socket part illustrating water shedding features incorporated into its upper parts. Detailed Description of the Embodiments: Referring first to Figure 1, the female connector part 1 is shown as comprising a moulded plastics body part 25 (shown in detail in Figures 3A through 3F) to which are assembled a spring-loaded locking member 18 (shown in detail in Figures 6A through 6D) serving additionally for connecting to the central pin of an in-line three-pin male connector part (not shown) having a central pin of circular cross-section, spring terminal parts 22-1 and 22- 2 (shown in detail in Figures 5A through 5E) for coupling to the side pins of the male connector part, pivotal shutters 8 and 9 (shown in detail in Figures 4A through 4E) and a cover member 26. The spring terminal parts 22-1 and 22-2 are identical to each other and are each as shown in Figures 5A to 5E. Each part comprises a receptacle 27 for a spade terminal, a pair of supports 28 upstanding from opposite ends of the receptacle 27, and an arcuate, almost semi-circular conductor portion 29 which is adapted to make contact with one of the side terminal pins of the male connector part. The receptacle 27 is adapted to seat into an accommodating recess 30 formed in the body part 25 of the female connector (see Figure 2A) and the free ends of the conductor portion 29 are adapted to seat in respective grooves 31 formed in the sidewall of an upstand 32 provided on the body part 25, the grooves 31 being capped at their upper ends (as viewed in Figure 2A) for providing vertical restraint to the ends of conductor portion 29 by an integrally moulded part 33 having upper surfaces inclined towards the conductor parts 29 of the respective springs 22-1, 22-2. The recesses 30 are each boxed in on the underside of the female connector part. Figure 2B shows the assembly of the locking member 18 with the connector and Figures 6A to 6D show ,the detailed form of the locking member 18 as comprising a tubular part 34 formed with indented spring fingers and coupled to one end of a leaf spring 35 having a receptacle 36 for a spade terminal formed at its other end. The tubular part 34 is adapted to be fitted into a bore 37 formed in a central cylindrical portion of the upstand 32 provided on body part 25 of the female connector, the fitting of the tubular part 34 into bore 37 being effected from the underside of the body part 25. As shown in Figures 3B and 3F, a hook 38 is formed integrally with the underside of body part 25 and the arrangement is such that leaf spring 35 can be engaged under the hook 38 by rotation of the locking member 18 about the axis of its tubular part 34. With the leaf spring 35 engaged under the hook 38, the tubular part 34 is effectively supported within the bore 37 and can be depressed downwardly against the action of the leaf spring 35 until it abuts the integrally formed stops 39 formed at the bottom of bore 37 (see, for example, Figure 3B) . By virtue of this arrangement, the tubular part 34 of the locking member 18 will be depressed by the central terminal pin of a male connector part as it is inserted into the female part, such central terminal pin being longer than the side pins, but the extent of this depression will be limited by the stops 39 thereby enabling the central terminal pin to be moved down into the tubular part 34 past the spring fingers formed therein. The shutter elements 8 and 9 are identical to each other and are each as shown in Figures 4A to 4E. The upstand 32 on the base 25 of the female connector has a pair of posts 40 at its opposite ends and the posts each carry a stub shaft 41 for mounting a respective one of the shutter elements as shown in Figure 2C. An elastomeric bushing may be incorporated into the mounting of the shutters 8 and 9 in order to spring bias the shutters into their closed condition as shown in Figure 2C, or alternatively appropriate spring members (not shown) may be provided for this purpose. In the closed condition of the shutters 8 and 9 and with the locking member 18 in its normal (non-depressed) condition, the upper edge of the tubular part 34 of the locking member 18 projects above the upper edge of the upstand 32 (see Figure 2B) and extends into the annulus defined by the two semi-circular grooves 21 formed in the undersides of the shutters; this engagement of the tubular part 34 of the locking member 18 with the grooves 21 serves to retain the shutters 8 and 9 in closed condition until such time as the locking member 18 is depressed by the longer central terminal pin of a male connector part, and thereafter the shutter elements 8 and 9 can be urged to pivot apart by the action of the shorter side pins of the male connector part upon the inclined surfaces of the shutter elements. In the event that the male connector part approaches the female connector part in such a relative orientation that the side terminal pins of the male connector part impinge upon the shutter elements 8 and 9 along or substantially along the line where their contiguous faces meet, the contact of the side terminal pins with the inclined surfaces 33 will serve to guide the male connector part towards a slightly different rotational orientation whereat the side terminal pins will assuredly contact the connector portions 29 of the springs 22-1 and 22-2. The side faces of the terminal pins may themselves be chamfered to enhance this effect. The operation of the female connector part of Figures 1 to 6 will be clear from the preceding description. The two shutter elements 8 and 9 define a frusto-conical recess in the upper face of the connector and this recess, in use of the connector, is adapted to receive the in-line terminal pins of a male connector part. The shutter elements 8 and 9 cannot be rotated apart so. long as the locking member 18 is in its undepressed position where its upper edge engages in the annular groove 21 defined by the two semi-circular grooves formed in the undersurfaces of the shutter elements. When the male connector part is introduced into the recess in the upper face of the female connector, however, the central pin 4 contacts the locking member 18 and depresses it, thereby moving the upper edge of the tubular part 34 of the locking member out of the groove 21 and enabling the shutter elements 8 and 9 to be pivoted apart. The central terminal pin of the male connector part is dimensioned to fit into the circular opening defined at the base of the frusto-conical recess defined by the curved surfaces of the two shutter elements, and to abut the ends of the spring fingers released internally from the tubular part 34 of the locking member 18 for displacing the locking member. Once the locking member 18 is moved out of engagement with the groove 21 in the undersides of the shutter elements 8 and 9, sloping flanks provided on the central terminal pin 4 engage the shutter elements and begin to urge them apart. As insertion of the male connector part progresses, the two side pins of the male connector, which may have chamfered faces, engage the conical surfaces of the shutter elements, thereby completing the full opening of the shutters whilst the central terminal pin drives down into the tubular part 34 of the locking member 18 and enabling the side pins to contact the conductor portions of the spring members 22-1 and 22-2. This sequence of events will occur substantially irrespective of the angular orientation of the male connector part with the female part; only in the event of the male connector part being inserted with its in-line terminal pins aligned with the contiguous faces of the closed shutter elements 8 and 9 will it be necessary to make a small angular adjustment of the relative orientation of the two connector parts in order to achieve their coupling together, and the inclined surfaces 33 will assist this and ensure that the side terminal pins of the male connector part are guided into contact with respective spring conductor parts 29. The illustrated embodiment provides satisfactory electrical clearances between the two spring conductor parts 29 and between the conductor parts 29 and the central tubular part 34 of the locking member 18 which, in the embodiment, is adapted to provide an earth connection. Furthermore, the design of the embodiment is such that, in use thereof in the base unit of an electrical appliance, any spillage of liquid into the recess of the female connector part will simply drain through the central bore 37. In use of the described female connector part in the base unit of an electrical appliance in the form of an electrically powered water heating vessel, the male terminal pins may be the terminal pins of an element protector device, for example the XI device manufactured by Otter Controls Ltd. and described in British Patent Specification No. 2194099 with reference to Figures 3A, 3B and 3C thereof, or alternatively could be pins of an appropriate connector provided in the appliance and coupled by means of appropriate leads to an element protector device provided elsewhere in the appliance. A modification of the conventional terminal pin geometry of the XI element protector would be required to conform it to the in-line pin geometry of the male connector part described herein, but the XI design in tolerant of such changes. Alternatively, the geometry of the described female connector part could be modified so that it would co-operate with male terminal pin geometries other than the described in-line geometry. The fact that the described female connector is non-polarized, namely the side pins of the male connector part can contact either of the two spring conductors 29, does not give rise to difficulties when the connector is used with the abovementioned XI element protector since the XI device provides safety with non-polarized supplies because it provides double pole disconnection in its back-up or secondary protection mode. As will be readily appreciated, the embodiment of the invention as described in the foregoing minimizes the need for positional guidance when mating the two connector parts, and it is only necessary for the central pin of the male connector part to be within the conical recess of the female connector part for ensuring mating of the parts. A suitable application of the described system might place the female connector part centrally on a circular base, within a cylindrical upstand. The male connector part might then be centrally positioned under the appliance proper within a raised area having sloping sides for engaging the sides of the base upstand in order to give just sufficient initial guidance to locate the central terminal pin of the male connector part within the conical recess of the female connector part. Alternatively, and as mentioned hereinbefore, the female connector part could be provided on the appliance proper and the male connector part could be on the base, for example as described in GB- A-2236220. The described arrangement of the locking member which, until released, prohibits opening of the shutter elements is particularly convenient for use with an earthed appliance but could be substantially modified, particularly if the earth connection was not required. For such an arrangement, the locking member could possibly be formed as an integrally moulded part of the body moulding 25 and could be supported by means of an integrally moulded plastics spring. Furthermore, whilst it is simple and convenient to arrange the locking member to interact directly with the shutter elements, a less direct interaction could be provided wherein, for example, depression of the locking member caused the withdrawal of latches provided in the connector and which in their forward positions inhibited the ability of the shutter elements to pivot open. Referring now to Figures 7 and 8A, the connector socket part of a second embodiment is generally designated 101 and is formed of a number of generally circularly- cylindrical components which assemble together to form a socket having rotational symmetry in a plane transverse to the axial direction of the components, which corresponds to the direction in which the plug and socket parts of the connector are moved to mate the two connector parts. The components of the socket part comprise a moulded plastics main housing 102, a moulded plastics shutter 103, first and second electrical contact rings 104 and 105, a spiral spring 106, a moulded plastics base 107 and a spring contact finger 108. As best shown in Figure 8A, the larger diameter contact ring 105 fits within an upper part 109 of the main housing 102 which is dimensioned to make close contact with an outwardly turned upper edge 110 of the contact ring 105 which abuts a shoulder 111 formed in the main housing 102. The shutter 103 fits loosely within the main housing 102 so as to be axially moveable with a degree of freedom to tilt as will be explained below, and comprises an annular head portion 112, a cylindrical portion 113 and an outwardly extending flange 114 which abuts the lower edge 115 of the contact ring 105 to prevent the shutter from moving out of the main housing. The main housing 102, with the contact ring 105 and shutter 103 installed, fits onto the base 107 with a cylindrical lower part 116 of the main housing fitting closely over an upstanding cylindrical part 117 of the base and a hollow.central post 118 of the base extending upwards through the central opening 119 provided in the head of the shutter 103. The lesser diameter contact ring 104 fits tightly onto an appropriately dimensioned part 120 of the post 118 with its lower edge 121 abutting a shoulder 122 provided on the post, and the upper edge 123 of the ring 104 is turned inwardly so as to conform to the lower extremity of an undercut portion 124 of the post 118. The spring contact finger 108 extends within the central hollow 125 of the post 118 and an opening 126 is provided in the top of the post for admitting a terminal pin to the interior of the post for electrically contacting the contact finger 108. Figure 8B shows an exemplary form of overtemperature disconnect device, suitable for use with a water boiling appliance for example, the device including a connector plug part adapted for use with the connector socket part of Figures 7 and 8A. The connector plug part is generally designated 130 and comprises a plastics moulding formed with an outer circularly-cylindrical wall 131 dimensioned to make a relatively close fit over the upper part 109 of the main socket housing 102, and an inner circularly- cylindrical wall 132 dimensioned to make a relatively close fit into the space occupied by the shutter 103 of the socket between the central post 118 and the radially inner surface of the socket part 109, the lower edge 133 of the inner wall 132 serving to depress the shutter 103 when the plug is correctly inserted into the socket in the axial direction. A central, axially extending terminal pin 134 is mounted in the plug part 130 and is adapted to extend into the opening 126 provided in the top of the central post 118 of the connector socket and to make electrical contact with the spring finger 108, and first and second spring terminals 135 and 136 each carrying an electrical contact at its free end are cantilevered within the plug part 130 in registry with respective grooves 137 and 138 provided in the outer and inner surfaces respectively of the inner wall 132 of the plug, the grooves 137 and 138 providing space for the respective spring terminals 135 and 136 to flex. Figure 9 shows the connector plug part 130 of Figure 8B mated with the connector socket part 101 of Figure 8A, the mating of the two parts being effected by moving them together in the axial direction as indicated by the arrow shown in Figure 8B. It will be seen from Figure 9 that the central terminal pin 134 of the plug part makes electrical contact with the spring finger 108 of the socket part, that the contact provided at the free end of spring terminal 135 of the plug part makes electrical contact with the outer contact ring 105 of the socket part, and that the contact provided at the free end of spring terminal 136 of the plug part makes electrical contact with the inner contact ring 104 of the socket part. The shutter 103 in the socket part is depressed against the bias of the spring 106 by the lower edge 133 of the wall 132 of the plug part, and will be restored to its closed condition as shown in Figure 8A by the action of the spring 106 when the plug part 130 is withdrawn from the socket part 101, abutment of the upper surface of the flange 114 on the shutter 103 with the lower edge 115 of the outer contact ring 105 limiting the range of upward movement of the shutter in the plug socket part. As mentioned previously, an undercut 124 (namely a portion of lesser diameter) is provided on the central post 118 of the socket part 101 just above the location of the contact ring 104. A similar undercut is defined within the upper part 109 of the main socket moulding 102 just above the location of the contact ring 105. The purpose of these undercuts is to prevent the contacts provided on the spring terminals 135 and 136. of the plug part dragging on the respective surfaces of the socket part during insertion and withdrawal of the plug part and possibly leaving metallic tracks on the surfaces. Such tracks would be electrically conductive and would represent an electrical hazard. The undercuts also reduce wear on the electrical contacts which may, for example, be formed of silver. The contact rings 104 and 105 are preferably formed of copper or a copper alloy having a thermal conductivity at least 90% of that of copper and provided with a thick (e.g. 50μm) surface plating of a silver antimony alloy as described in GB-A-2253097, and the terminal pin 134 may be similarly formed. It will be seen that the plug and socket parts of the connector of Figures 7 to 11 have rotational symmetry in a plane transverse to the axial direction of their insertion one into the other as depicted by the arrow shown in Figure 8B. Namely, apart from the spring 106 and the spring terminals 135 and 136, all of the component parts of the plug and socket are generally circular in transverse cross-section, transverse that is to the axial direction. The fact that this is so enables the plug part of the connector to be introduced into the socket part throughout a full 360° of relative rotation between the parts. Referring to Figure 10, this is a view of the socket part of the connector which is very similar to Figure 8A, but illustrates the locking action of the shutter in the event that it is subject to a force which is not applied uniformly throughout the full extent of its annular upper surface. In order to meet safety requirements, it must not be possible to gain access to live parts within the socket by depressing the shutter with a test or human finger and, as shown in Figure 10, the arrangement of the shutter 103 is such that if it is depressed at a single point, as shown by the arrow, then it rocks upon the supporting spring 106 and its lower rim engages the upper edge of the cylindrical upstand 117 which prevents downwards movement of the shutter. The shutter can only be depressed into the socket by application to the top of the shutter of a force which is more or less uniform throughout the annular extent of the shutter head so that the shutter is maintained in coaxial alignment with the socket and its flange 114 can slide down within the cylindrical upstand 117. The underside of the inner wall 132 of the plug part can provide such a uniform force so long as the plug and socket parts are sufficiently well aligned in the axial direction. As shown, the inner edge of the top of the upstand 117 has a chamfer and, by selection of the angle of this chamfer and the radial clearance between the shutter flange 114 and the inner surface of the upstand 117, it is possible to achieve a satisfactory range of angle of approach of the plug to the socket whilst maintaining the electrical safety provided by the shutter. The engaging surfaces of the shutter and the upstand 117, that is to say the surfaces which engage to prevent depression of the shutter when a non-uniform force is applied which causes it to tilt, could be curved so as to have a ball-and-socket type of co-operation allowing smooth disengagement of the locked shutter as the plug is brought into proper alignment for entry into the socket. By provision of such curved surfaces, the appliance proper part of a cordless appliance could be placed casually onto its base and smooth engagement between the plug and socket parts of the connector system would still be achieved. Referring now to Figure 11 and back to Figure 8A, it will be seen that the top edge of the main housing 102 of the socket part 101 of the subject connector is provided with shaped castellations 150 designed to allow water to drain from the top surface of the socket whilst providing an inwardly facing guiding surface to enhance the engagement guidance of the plug 130 into the socket. As shown in Figure 8A, the inner surface of each castellation upstand forms part of a female conical annulus which acts to guide the bottom surface 133 of the inner wall 132 of the plug into contact and alignment with the top of the shutter 103, and also serves as a lead in for the contact provided at the end of spring terminal 135. The surfaces between the castellation upstands form part of a male conical annulus which slopes outwards and downwards to encourage any water spilled onto the top surface of the shutter to escape between the castellation upstands rather than penetrate to the interior of the socket. The main housing 102 is further provided with a skirt 151 which forms a water shedding feature designed to overlap an aperture in a cordless appliance base, for example, in which the socket is mounted. While the plug and socket connector as described in the foregoing are particularly intended for use with a cordless electrical appliance, such as a kettle or hot water jug for example, the invention is not limited to such an application and could form the basis of an appliance cord set, for example, replacing the standard 10 amp connector currently in use in the UK. The socket of Figures 7 to 11 for example could be fitted with a cable anchorage and cosmetic cover and used with a plug mounted in or on an appliance, or alternatively the plug could be provided with the cable anchorage and cover and used with the socket mounted in or on the appliance. A locking means would preferably be provided to ensure that the shutter spring did not push the plug out of the socket and this could be a simple manual latch arrangement. Such a plug and socket connector would enable very simple and low force engagement and would provide enhanced safety as compared to current 10 amp connectors. The overtemperature disconnect device shown in Figure 8B is a modified form of the device described in GB-A- 2194099 with reference to Figures 3A, 3B and 3C thereof and is illustrated herein in schematic form merely by way of an example of the way in which the plug part of the subject connector could be utilized. As illustrated in Figure 8A hereof the upper ends 161 and 162 of the spring terminals 135 and 136 in the plug portion 130 of the device extend into a switch enclosure 160 where they are engaged by respective electrically conductive springs 163 and 164 which are biassed into engagement with the terminal ends 161 and 162 by a moulded plastics material member 165 which corresponds to the thermally-collapsible carrier 121 shown in Figures 3A, 3B and 3C of GB-A-2194099 abovementioned. Although not shown in Figure 8A, reference to GB-A- 2194099 will show that the contact between the springs 163 and 164 and the terminal ends 161 and 162 is necessary in order that power can be supplied through the overtemperature disconnect device to an electrical heating element comprising a resistance heating element proper and an element head plate, the head plate of the heating element being shown in Figure 8B at 166. The member 165 stands on the head plate 166 as shown and, in the event of an overtemperature condition, the member 165 thermally deforms under the action of the springs 163 and 164 thereby breaking the connections made between the springs 163 and 164 and the terminal ends 161 and 162 and interrupting the supply of power to the heating element. As described in GB-A-2194099, the member 165 can serve to carry a bimetallic element in close thermal contact with the element head plate 166, the bimetallic element serving to open a set of contacts provided in the power supply line to the heating element in the event of an element overtemperature condition, the thermally induced collapse of the member 165 then serving a secondary or back-up function in the event, however unlikely, that the primary protective function provided by the bimetal and its associated contacts set fails to operate. It will be appreciated that the above-described embodiment is exemplary only and that many modifications and variations are possible without departure from the general ambit of the invention. For example, it would be possible to dispense with either the central terminal pin 134 or one of the spring terminals 135, 136 if there was no requirement for an earth terminal. If the central terminal pin 134 was dispensed with, then clearly there would be no need to form the central post 118 of the socket part 101 with a hollow interior and the spring terminal 108 could also be eliminated, though it could in some circumstances possibly be advantageous to retain the hollow interior of the central post as a feature for enhancing the water shedding ability of the socket. Other modifications and variations will readily occur to those possessed of relevant skills.

Claims: CLAIMS : 1. In or for a cordless electrical appliance, a shuttered electrical connection system permitting the appliance proper to be operatively coupled to its base throughout substantially 360° of relative rotational orientation between the respective parts. 2. In or for a cordless electrical appliance, a shuttered electrical connection system permitting the appliance proper to be operatively coupled to its base throughout a full 360° of relative rotational orientation between the respective parts. 3. A shuttered electrical connection system as claimed in claim 1 or 2 and comprising a plug part and a socket part, and wherein the shutter is arranged to be locked in the stand alone condition of the plug and socket parts and to be releasable by proper coupling of the plug part with the socket part. 4. A shuttered electrical connection system as claimed in claim 3 wherein the shutter is provided in the socket part. 5. A plug and socket electrical connector wherein a shutter in the socket is displaceable by the plug to permit entry of the plug into the socket only if the shutter has a predetermined disposition relative to the socket, and wherein the plug is insertable into the socket irrespective of the relative rotational orientation of the plug and socket transversely to the direction of insertion of the plug into the socket. 6. An electrical connector comprising a plug part and a socket part, the plug part being insertable into the socket part by relative movement between the two parts in a predetermined direction irrespective of the relative rotational orientation of the two parts transversely to said predetermined direction, and a shutter being provided in the socket part and being displaceable therein for admitting the plug part only if the shutter has a predetermined disposition, the shutter being capable of adopting alternative dispositions within the socket part, and the plug part being formed so as to hold the shutter in said predetermined disposition so long as the plug part and socket part are approached to each other in said predetermined direction. 7. An electrical connector as claimed in claim 6 wherein the socket part comprises a circularly-cylindrical member within which a shutter having a circular section is axially displaceable so long as the shutter disposition is generally coaxial with the socket part, the arrangement being such that the shutter cannot be displaced within the socket if the shutter disposition is tilted out of coaxiality. 8. An electrical connector as claimed in claim 7 wherein a portion of the shutter is arranged to engage a portion of the socket to prevent displacement of the shutter into the socket when the shutter disposition is out of coaxiality. 9. An electrical connector as claimed in claim 8 wherein the shutter has a circularly-cylindrical portion dimensioned to make a sliding fit within a corresponding portion of the socket, and entry of the socket into such corresponding socket portion is inhibited by engagement of the one part with the other if the socket is depressed in a tilted disposition. 10. An electrical connector as claimed in claim 7 or 8 or 9 wherein a circularly-cylindrical post is provided within the circularly-cylindrical socket member, the post extending coaxially of the circularly-cylindrical socket member, and the shutter is annular and is arranged to be displaceable within the annular space between the internal surface of the circularly-cylindrical socket member and the external surface of the post. 11. An electrical connector as claimed in any of claims 7 to 10 wherein an electrical contact ring is provided in said circularly-cylindrical socket member and an electrical terminal is provided on the plug part for contacting said contact ring when the plug and socket parts are operably engaged. 12. An electrical connector as claimed in claim 11 wherein the electrical terminal provided on the plug part comprises a contact carried by a terminal spring on the surface of a circularly-cylindrical member of the plug which is adapted to be inserted into the circularly- cylindrical socket member. 13. An electrical connector as claimed in claim 10, or as claimed in claim 11 or claim 12 as dependent upon claim 10, wherein an electrical contact ring is provided on said post and an electrical terminal is provided, on the plug part for contacting said contact ring on said post when the plug and socket parts are operably engaged. 14. An electrical connector as claimed in claim 13 wherein the electrical terminal provided on the plug part for contacting the contact ring on the post comprises a contact carried by a terminal spring on the inner surface of a hollow circularly-cylindrical member of the plug which is adapted to be inserted into the annular space between the circularly-cylindrical socket member and the post. 15. An electrical connector as claimed in any of claims 11 to 14 wherein the circularly-cylindrical socket member and/or the post respectively is provided with a portion adjacent to the location of its respective contact ring which is dimensioned so that the respective terminal provided on the plug part does not drag across such portion during insertion and removal of the plug part into and from the socket part. 16. An electrical connector as claimed in any of claims 11 to 15 wherein the or each said contact ring is formed of copper or of a copper alloy having a thermal conductivity approaching that of copper and has a thick plating layer of silver antimony alloy. 17. An electrical connector as claimed in claim 10, or as claimed in any of claims 11 to 16 as dependent upon claim 10, wherein said post is hollow. 18. An electrical connector as claimed in claim 17 wherein an electrical contact is provided within said hollow post and a terminal pin is provided on the plug part for entering into the hollow post and contacting said electrical contact when the plug and socket parts are operably engaged. 19. An electrical connector as claimed in any of claims 3 to 18 wherein the socket part includes water-shedding formations. 20. An electrical connector as claimed in claim 19 wherein an annular rim of the socket part is formed with castellations, the inner surfaces of the upstands whereof form part of a female conical annulus serving to guide the plug part into the socket part, and the surfaces between the upstands whereof form part of a male conical annulus for encouraging the shedding of water between the castellations. 21. An electrical connector as claimed in any of claims 3 to 21 wherein one of the plug and socket parts of the connector is formed as an integral part of an overtemperature disconnect device adapted to be incorporated into an electrical appliance. 22. An electrical connector as claimed in claim 21 wherein the other of the plug and socket parts of the connector is adapted to be incorporated into the base unit of a cordless electrical appliance. 23. A cordless electrical appliance incorporating an electrical connector as claimed in any of the preceding claims. 24. A female connector part for a connector system comprising interconnecting male and female parts, said female connector part having a plurality of movable shutter elements having surfaces which together define a concavity for receiving the male connector part, and a releasable locking member holding said plurality of shutter elements in closed condition until released, the arrangement being such that the insertion of the male connector part into said cavity serves to release said locking member and to urge said shutter elements open for enabling electrical terminals of said male connector part to engage conductors provided in the female connector part. 25. A female connector part as claimed in claim 24 wherein said concavity is circular in plan view and has a generally conical or frusto-conical form, the arrangement being such as to enable the male connector part to mate with the female connector part throughout substantially a 360° range of alignment rotation of the male connector part with respect to the female connector part. 26. A female connector part as claimed in claim 25 having two shutter elements each of which has a surface portion defining one half of a circular, frusto-conical concavity, and the two shutter elements are pivotally mounted so that in the closed condition of the shutter elements the said surface portions face each other. 27. A female connector part as claimed in claim 26 wherein the underside of each of said shutter elements is provided with a formation which, when the shutter elements are in closed condition, together co-operate with said locking member, and the locking member is displaceable by the male connector part on insertion of the same into the concavity of the female connector part so as to free said formations from the locking member and thereby enable the shutter elements to open. 28. A female connector part as claimed in claim 27 wherein the locking member is located at the apex of the frusto-conical cavity so as to be displaceable by an appropriately formed portion of the male connector part. 29. A female connector part as claimed in claim 28 wherein the locking member comprises an electrical conductor of the female connector part, said electrical conductor being adapted to be contacted by a central terminal of the male connector part. 30. A female connector part as claimed in claim 29 wherein at least one arcuate conductor is provided in the female connector part to be contacted by a side terminal of the male connector part. 31. A female connector part as claimed in claim 30 wherein there are two arcuate conductors provided in the female connector part to be contacted by respective ones of two side terminals of the male connector part, and adjoining ends of the two arcuate conductors are spaced apart from each other, means being provided in the gaps between such adjoining ends for directing the entering side terminals of the male connector part to one side or other of the gaps. 32. A female connector part as claimed in any of claims 24 to 31 utilized in a cordless connection system. 33. A female connector part as claimed in any of claims 24 to 31 in combination with a co-operating male connector part. 34. A cordless electrical appliance comprising a base unit and an appliance proper and wherein a female connector part as claimed in any of claims 24 to 31 and a co-operating male connector part are utilized for connecting the appliance proper to the base unit.

Inventors: BROOK STEPHEN ROGER, GAETA ANTONIO MARTIN, HARRISON RONALD BRIAN, O'NEILL ROBERT ANDREW, WHITE IAN GEOFFREY, BROOK, STEPHEN, ROGER, GAETA, ANTONIO, MARTIN, HARRISON, RONALD, BRIAN, O'NEILL, ROBERT, ANDREW, WHITE, IAN, GEOFFREY
Applicants: BROOK STEPHEN ROGER, GAETA ANTONIO MARTIN, HARRISON RONALD BRIAN, ONEILL ROBERT ANDREW, OTTER CONTROLS LTD, WHITE IAN GEOFFREY, OTTER CONTROLS LIMITED
Application year: 1993
Main classification: H02B1
IPC codes: D06F79, H01R13, H02J7