GB2208332A

GB2208332A - Switched, cordless electrical appliances

Info

Publication number: GB2208332A
Application number: GB8803883A
Authority: GB
Inventors: Malcolm James Wootton; John Crawshaw Taylor
Original assignee: Strix Ltd
Current assignee: Strix Ltd
Priority date: 1987-07-24
Filing date: 1988-02-19
Publication date: 1989-03-22
Anticipated expiration: 2008-02-19
Also published as: GB2208332B; GB2208336A; GB8817136D0; HK48493A; GB8717626D0; GB2208336B; GB2208331A; GB8803882D0; SG21493G

Abstract

An electrical appliance (4) such as a water heating jug or iron, is adapted to be detachably interengaged with a corresponding base unit 10, whereby terminal pins 17 of an electrical connector 16 arranged in a lower region of the appliance are engaged with a female socket connector 11 forming part of the base unit for the supply of electric power to the appliance. Switch means 15 are mounted to the appliance for electrically isolating said pin connector from the appliance when the appliance is not engaged with the base unit, the switch means comprising a pair of contacts associated with a spring mechanism which maintains the contacts open until such time as the appliance is engaged with the base unit, an operating member 22 being coupled to the spring mechanism and being arranged to co-operate with a part of the base unit or socket connector thereof when the appliance is engaged with the base unit so that the spring mechanism operates to close the contacts by snap-action to permit power to be supplied to the appliance, the spring mechanism also operating to open the contacts by reverse snap-action when the appliance is disengaged from the base unit. The switch means 15 is mounted between the pins 17 and the conventional terminal pins (at 30) of the appliance. The pins 17 are vertical or sloped (see figure 4, not shown). <IMAGE>

Description

1 - NO 52-558 ELECTRICAL APPLIANCES 2 2 0 8 33 This invention relates to

electrical appliances, and relates in particular to such appliances which have become known as "cordless" appliances. Such appliances are provided with a free standing base unit defining a receiving area for a lower part of the appliance, the appliance being placed on the base unit when it is desired to supply electrical power to the appliance and being subsequently removable from the base unit. A known cordless appliance is an electrical water beating jug having an immersion heater or similarly constructed heater mounted in thermal contact with the underside of the base of the jug. The same principle is applicable to other appliances which need not necessarily be energised while being handled, e.g. electric irons.

The base unit of a cordless electrical appliance includes a female socket connector connected to a source of electrical power and arranged for engagement with a complementary terminal pin connector, mounted to a lower part of the appliance, as and when the appliance is placed on the base unit whereby electrical power may then be supplied to the appliance. It is therefore the base unit rather than the appliance which is seen to be connected to the mains power supply, and when detached from the base unit no electrical lead is connected to the appliance; hence the name cordless.

with such arrangements problems can however arise due to electrical arcing between the electrical contacts of the socket connector and the pins of terminal pin.connector if engagement therebetween occurs with the socket connector connected to the mains (as is common), so that the appliance is energised by.the action of interengaqing the pin and socket connectors as the appliance is placed on the base unit. The problem of arcing can be greater in the case of a cordless appliance than in the case of a more traditional arrangement of detachable socket connector since in the cordless appliance the force and speed of interengagement between the socket and pin connectors will typically be less.

Viewed from a first aspect the invention provides an electrical appliance adapted to be detachably interengaged with a corresponding base unit therefor, whereby terminal pins of an electrica 1 connector arranged in a lower region of the appliance are engaged with a female socket connector forming part of the base unit for the supply of electric power to the appliance, there being switch means mounted to the appliance for electrically isolating said male pin connector from the appliance when the appliance is not engaged with the base unit, said switch means comprising a pair of contacts associated with a spring mechanism which maintains the contacts open until such time as the appliance is engaged with the base unit, an operating member being coupled to the spring mechanism and being arranged to co-operate with a part of the base unit or socket connector thereof when the jug is engaged with the base unit as aforesaid whereby the spring mechanism operates to close the contacts by snap-action to permit power to be supplied to the appliance, the spring mechanism also operating to open the contacts by reverse snap-action when the appliance is disengaged from the base unit.

With such an arrangement the problem of arcing is avoided, and since the switch contacts are opened and closed by snap action, rapid and positive operation of the switch is achieved regardless of the speed of interengagement between the appliance and the base unit. In particular it has been found that the operating time of the switch should be less 11 than one half the cycle of the ac power supply if arcing is to be avoided.

in a preferred embodiment, the switch means comprises a pivotal contact lever carrying a switch contact and movable by snap action to make and break engagement of such switch contact with an adjacent stationary contact. Spring means are provided normally to bias the lever into a first position in which the contacts are open, and the lever being tripped by snap action to a second position in which the contacts are closed via an unstable dead centre position upon engagement thereof by the operating member when the appliance is placed on its base unit. The second position is a semi- stable one, in that once the appliance is removed from the base unit so that the operating member is released the spring means returns the lever to the first position via the dead centre position so that the contacts are opened by reverse snap- action.

In a preferred embodiment, the contact lever is formed of metallic strip material, and the spring means constitutes a central tongue integral with and extending intermediate two side arms of the lever, the tongue being arranged in tension to urge the lever into the first or second positions as aforesaid. Preferably, the tongue is defined by a generally U-shaped cut out portion which defines also a bridge portion spaced from the end of the tongue and extending between the side arms at the end of the lever remote from the contact carried thereby.

In a preferred such embodiment, the lever is arranged on a fixed support member projecting between the side arms, and defining a location seat for the front end of the tongue, there being a pivotal member or tensioner acting between the support member and free end of the contact lever and arranged to maintain the tongue in tension. In such an arrangement, the operating member preferably co-operates with the free end of the lever. Advantageously, the pivotal member or tensioner projects between the side arms and includes a notch which engages the front edge of the bridge portion extending between the side arms at the free end of the lever. Preferably, the operating member is arranged for engagement with an extension of the tensioner, beyond the point of engagement thereof with the bridge portion. In this way, the operating member can have greater leverage about the pivotal mounting of the tensioner to the support member which means that less force on the operating member is required to trip the contact lever to its second position. If there is not adequate leverage, it is possible that the weight of the appliance-may not be sufficient to maintain the operating member in a position in which the contact lever remains tripped to its second position. The arrangement whereby the operating member engages an extension of the tensioner is also such that the leverage may conveniently be adjusted by varying the length of such extension whereby the switch means may be adapted for use with different weights of appliance without otherwise being substantially redesigned or modified. In preferred embodiment, the operating member comprises push rod located adjacent and extending substantially parallel to the terminal pins of the pin connector of the appliance, the push rod co-operating with a part of the base unit or socket connector thereof when the appliance is engaged with the base unit so as to be displaced in such a way to trip the contact lever to its second position in which the contacts are closed.

In a particularly advantageous embodiment which simplifies manufacture and minimises the number of parts involved the preferred switch means is 1 associated with the terminal pin connector of the appliance, the said support member being conductive and being fixedly and electrically connected to the top of one of the pins of the connector. The support member, with the tensioner which is also conductive, thus forms part of the electrical circuit whereby power is supplied to the appliance via the switch contacts.

As discussed above one form of cordless electrical appliance is a water heating jug. Jugs of this general type are traditionally provided with a thermally-sensitive control unit having switch means adapted and arranged to disable the heater upon overheating e.g. in the event of the jug boiling dry or being switched on with insufficient liquid in the jug to cover the heating element. A switch means adapted to disable the heater upon boiling may also form part of the same or further control unit of the jug. There are many known types of control unit intended for use in traditional rather than cordless Jugs and kettles, i.e. those where a separate female socket connector is manually engaged with and disengaged from the appliance, rather than being incoporated in a base unit.

Control units have thus generally been provided with terminal pins adapted for engagement by a separate socket connector whereby electrical power may be supplied to the heater via switch means of the control.

With the preferred arrangement of switch means discussed above, a stationary electrical contact of the switch means may conveniently be mounted, e.g. by a suitable clip, to a terminal pin of such a control unit and the arrangement may thus be such that a control unit not previously adapted for use with cordless appliances may be incorporated in such an applicance without the need substantially to modify the control unit concerned.

- 6 Viewed from a second aspect the invention provides a hot water jug adapted to be detachably interengaged with a corresponding base unit therefor, the jug incorporating a first terminal pin connector located in a lower region thereof and arranged for engagement with a complementary socket connector forming part of the base unit, the socket connector being connected or connectable to a source of mains power, the jug further comprising a thermally-sensitive control unit a body portion of which mounts the pins of a second terminal pin connector forming part of the control unit, the control unit incorporating protector switch means connected between the second terminal pin connector and the heater of the jug, such protector switch means being operable to disable the heater in the event of the element thereof overheating, the jug further comprising a heater isolating switch means connected between respective pins of said first and second terminal pin connectors, such switch means comprising an electrically conducting contact lever carrying a movable contact and pivotable by snap-action to make and break engagement between said movable contact and an adjacent stationary contact, the stationary contact being carried by a conducting support element which is fixedly mounted to one of the terminal pins of said second terminal pin connector, and said lever member being located on an electrically conducting support member which is fixedly mounted to one of the pins of the first terminal pin connector, there being an operating member which is displaceable in a direction generally parallel to the pins of the first connector when said jug is engaged with the base unit and co-operates with the contact lever so that the contacts of the heater isolating switch means are closed by snap-action of the contact lever to permit the supply of electrical power to the heater, the switch contacts opening by reverse snap-action of the -X lever when the jug is removed from the base unit so that said first terminal pin connector is isolated from said second terminal pin connector and thus from said heater.

In one embodiment the terminal pins of the first terminal pin connector are orientated generally vertically, although in an alternative embodiment the pins may be inclined to improve ease of engagement between the pin and socket connectors when the 10 jug is engaged with the base unit.

As described above, one of the pins of the terminal pin connector of the control unit is electrically connected to a corresponding pin, usually the live pin, of the first terminal pin connector via the heater isolating switch means. The remaining pins, i.e. the neutral and earth pins, of the control terminal pin connector can conveniently be permanently electrically connected to their counterparts by suitable conducting strips and clip members.

This preferred configuration enables a known type of thermally-sensitive control unit, i.e. not one specifically adapted for use in a cordless arrangement, to be incorporated in a cordless jug together with a heater isolating switch means without the need to substantially modify the control unit whilst minimising the number of electrical components and connections required.

Certain embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:

Figure 1 is a schematic side view, partly in cross-section and partly broken away, illustrating a lower peripheral region of a water heating jug in accordance.with the invention; Figures 2a and 2b are schematic side elevational views illustrating the element isolating switch means; Figures 3a-3c illustrate the contact lever of the switch means shown in Figures 2a and 2b; and Figure 4 illustrates an alternative embodiment of water heating jug.

Referring firstly to Figure 1, the lower peripheral region of a water heating-jug is illustrated. The jug includes a wall 1 of suitable plastics material provided with an aperture 2 within which the head portion 3 of an electric immersion heater 4 is clamped in sealing relation with a termallysensitive control unit 5 ' by means e.g. of bolts (not shown). The general configuration of the heater and control unit will be well known to those skilled in the art, dnd as is conventional the heater includes a pair of cold leads 8 extending through the head portion 3 and a so-called hot return part 6 which is brazed to the head in good thermal contact therewith. An annular sealing ring is engaged between the head and the control unit so as to provide a water tight seal with the container wall. The control unit 5 may, for example, be of the general type disclosed in U.K. Patent Specification No. 2182598, and incorporates electrical switch means coupled to a thermally sensitive actuating means, for example, a bimetal, arranged in good thermal contact with the hot return 6 of the element, the arrangement being such that the heater 4 is disabled upon overheating thereof e.g. in the event of the jug boiling dry or having been switched on with insufficient water therein to cover the element. optionally the control unit 5 may comprise a further back-up switch means arranged to disable the heater upon serious overheating in the event of failure of the primary protector switch means, and in some configurations a switch means is also provided in the control unit which is responsive to an actuator exposed to steam or vapour egressing 1; 9 from the container so as to disable the heater upon boiling.

Those skilled in this art will be familiar with the basic components of such a control unit and will recognise that the general layout and configuration may vary.

As is conventional with such a control unit, body part thereof carries terminal pins 7 of terminal pin connector adapted, in traditional applications for the control unit, for engagement with a detachable female socket connector whereby electrical power may be supplied to the heater 4 via the switch means of the control unit.

The illustrated jug is however a cordless arrangement and the jug is thus adapted for engagement on a base unit 10 incorporating an upwardly facing female socket connector 11 connected to the mains via a cable 12 which extends out of the base unit. The socket connector 11 is shown only schematically in Figure 1, but may be of the general type disclosed in co-pending patent application No. 872,1070 dated 8th September 1987 entitled "Electrical Connectors". As shown schematically in Figure 1 the connector 11 incorporates contact members 13, which are connected respectively to the live, neutral and earth, located beneath respective upwardly facing terminal pin receiving apertures.

The illustrated jug incorporates an element isolating switch means 15 incorporated in the upper part of a male terminal pin connector 16 which carries terminal pins 17 (of which only one is shown in Figure 1 for clarity) projecting downwardly from the terminal pin connector and adapted for engagement with respective ones of the contact members 13 of the socket connector 11. when the jug is placed on its base unit.

The switch means 15, as shown most clearly in Piqures 2a and 2b, includes a movable contact carried by a pivotal contact lever 21 coupled to the top end of a vertically displacable operating member 22, the operating member 22 being slidably mounted to the housing of the terminal pin connector 16 and projecting downwardly through the lower wall of the housing so as to be engaqable with the top face of the socket connector 11 of the base-unit.

As shown in Figures 3a-3c the contact lever, formed of resilient metallic strip material, includes side arms 25 defining therebetween a central tongue 26 extending away from contact 20, and a bridge portion 27 extending between the side arms 26 at the end of the lever remote from the contacts 20.

The lever 21 is located on a fixed conducting support member 28 which is fixedly connected to the top end of the live one of the terminal pins 17 of the pin connector 16. The switch means further comprises a fixed contact member 29 carried by a metallic strip support element 30 including a sleeve 31 at its lower end which is engaged with the corresponding one of the terminal pins 7 of the pin connector of the control unit 5. - A pivot member or tensioner 32 is engaged between the top of the support member 28 and the front edge of the bridge portion 27, whereby the lever is pivotally mounted with the tongue 26 held in tension. Knife edge pivots Pl,P2 are formed respectively between the tensioner 32 and the support member 28 and between the tensioner and the front edge of the bridge portion 27, the front edge of the tongue 26 engaging in a groove formed in the confronting face of the support member 28.

The tensioner 32 includes an extension 33 which projects below the lever 21 and away from the contact end, the extension 33 being engaged by the top end of the operating member 22.

1 This arrangement may be regarded as a moving pivot over centre spring mechanism. When the jug is removed from the base unit the operating member is free to move downwardly, and in this condition as shown in Figure 2a the tongue 26 biases the end of the contact lever 21 carrying the movable contact 20 away from the fixed contact 29, suitable stop means (not shown) being provided to define the illustrated stable open position of the lever.

In this condition the live terminal pin 17 of the connector 11 is isolated from the corresponding terminal pin 7 of the control unit connector. Power can therefore not be supplied to the heater.

When the jug is engaged with the base unit, the operating member 22 is displaced upwardly and therefore the tensioner 32 pivots about pivot point Pl, and at a certain critical position the pivot point P2 reaches a dead centre position of the system, and the lever moves by snap-action to a closed position shown in Figure 2b. The arrangement is such the lever only moves to the closed condition once the pins 17 are engaged with the corresponding contact members 13 of the socket connector 11, whereby the problem of arcing occuring between the pins and contact members is avoided.

The closed condition is a semi-stable condition in that once the operating member is released consequent upon the jug being removed from the base unit, the tongue 26 causes the end of the lever remote from the contact 20 to move downwardly until the pivot point P2 again reaches a dead centre position whereby reverse snap-action causes the movable contact to move downwardly so that the contacts are broken. It will thus be seen that the contacts are always open and closed rapidly by snap-action, regardless of the speed of movement of the operatinq member and of the speed of engagement between the jug and its base unit.

22083"11")2 It will be apparent from the drawings that in the closed condition of the contacts 20,29 electrical power may be supplied between the terminal pins 17,7 via the support member 28, the over centre lever 21 and the contacts 20,29. As described above, electrical power can then be supplied to the heater via the switch means of the control unit 5, and it will be seen that a control unit designed for use in a traditional arrangement may be adapted for use in a cordless jug without the need substantially to modify the control unit itself. The earth and neutral wires of the terminal pins 17 may be readily connected to the corresponding pins 7 of the central unit via metallic strip members (not shown).

An alternative embodiment is shown schematically in Figure 4, in which like parts are denoted by like reference numerals. This embodiment differs from the one illustrated in Figure 1 in that the terminal pins 17 of the connector 16 are inclined, as are the corresponding openings defined in the socket connector 11. This improves the ease of engagement between the connectors 16,11. Figure 4 further illustrates a strip member 40 permanently electrically connecting the neutral one of the pins 17 to the corresponding pin 7, the switch means 15 again being associated with the live pin. Figure 4 further illustrates part of the control outer plastics housing 41 which defines an inner housing within which the switch means 15 and socket connector 16 are located. The control unit 5 of the Figure 4 embodiment further comprises an overcentre spring mechanism 42 arranged to couple a switch means (not shown) of the control unit to a thermallysensitive actuator exposed to steam egressing from the container during boiling, as is usual in such a control.

t 151 b.

Claims

Claims 2208332

1. An electrical appliance adapted to be detachably interengaged with a corresponding base unit therefor, whereby terminal pins of an electrical connector arranged in a lower region of the appliance are engaged with a female socket connector forming part of the base unit for the supply of electric power to the appliance, there being switch means mounted to the appliance for electrically isolating said male pin connector from the appliance when the appliance is not engaged with the base unit, said switch means comprising a pair of contacts associated with a spring mechanism which maintains the contacts open until such time as the appliance is engaged with the base unit, an operating member being coupled to the spring mechanism and being arranged to co-operate with a part of the base unit or socket connector thereof when the jug is engaged with the base unit as aforesaid whereby the spring mechanism operates to close the contacts by snap-action to permit power to be supplied to the appliance, the spring mechanism also operating to open the contacts by reverse snap-action when the appliance is disengaged from th.e base unit.

2. An appliance as claimed in claim 1, wherein the switch means comprises a pivotal contact lever carrying a switch contact and movable by snap action to make and break engagement of such contact with an adjacent stationary contact, spring means being provided to bias the lever into a first position in which the contacts are open when the appliance is disengaged from the base unit, the lever being tripped by snap action to a second position in which the contacts are closed via an unstable dead centre position upon engagement thereof by the operating member when the appliance is placed on its base unit.

3. An appliance as claimed in claim 2 wherein the contact lever is formed of metallic strip material, and the spring means constitutes a central tongue integral with and extending intermediate two side arms of the lever, the tongue being arranged in tension to urge the lever into the first or second positions as aforesaid.

4. An appliance as claimed in claim 3 wherein the tongue is defined by a generally U-shaped cut out portion which defines also a bridge portion spaced from the end of the tongue and extending between the side arms atthe end of the lever remote from the contact carried thereby.

5. An appliance as claimed in claim 3 or 4 wherein the lever is arranged on a fixed support member projecting between the side arms, and defining a location seat for the front end of the tongue, there being a pivotal member or tensioner acting between the support member and free end of the contact lever and arranged to maintain the tongue in tension.

6. An appliance as claimed in claims 4 and 5 wherein the tensioner projects between the side arms and includes a notch which engages the front edge of the bridge portion extending between the side arms at the free end of the lever.

7. An appliance as claimed in claim 6 wherein the operating member is arranged for engagement with the tensioner, beyond the point of engagement thereof with the bridge portion.

8. An appliance as claimed in 5, 6 or 7 wherein the support member and tensioner are conductive, the support member being mounted to the top of one of the terminal pins of the electrical connector, the support member, tensioner and lever all forming part of the electrical circuit whereby power is supplied to the heater via t he switch contacts.

9. An appliance as claimed in any preceding claim wherein the operating member comprises a push rod 1 located adjacent and extending substantially parallel to the terminal pins of the pin connector of the appliance, the push rod co-operating with a part of the base unit or socket connector thereof when the appliance is engaged with the base unit so as to be displaced in such a way to trip the contact lever to its second position in which the contacts are closed.

10. A hot water jug adapted to be detachably interengaged with a corresponding base unit therefor, the jug incorporating a first terminal pin connector located in a lower region thereof and arranged for engagement with a complementary socket connector forming part of the base unit, the socket connector being connected or connectable to a source of mains power, the jug further comprising a thermally-sensitive control unit a body portion of which mounts the pins of a second terminal pin connector forming part of the control unit, the control unit incorporating protector switch means connected between the second terminal pin connector and the heater of the jug', such protector switch means being operable to disable the heater in the event of the element thereof overheating, the jug further comprising a heater isolating switch means connected between respective 1Dins of said first and second terminal pin connectors, such switch means comprising an electrically conducting contact lever carrying a movable contact and pivotable by snap-action to make and break engagement between said movable contact and an adjacent stationary contact, the stationary contact being carried by a conducting support element which is fixedly mounted to one of the terminal pins of said second terminal pin connector, and said lever member being located on an electrically conducting support member which is fixedly mounted to one of the pins of the first terminal pin connector, there being an operating member which is displaceable in a direction generally parallel to the pins of the first connector when said jug is engaged with the base unit and co-operate with the contact lever so that the contacts of the heater isolating switch means are closed by snap-action of the contact lever to permit the supply of electrical power to the heater, the switch contacts opening by reverse snap-action of the lever when the jug is removed from the base unit so that said first terminal pin connector is isolated from said second terminal pin connector and thus from said heater.

11. An electrical appliance, substantially as herein described with reference to the accompanying drawings.

Published 1988 w- The Patent Office. State_ Ho,,;sc. 667.1 Hir. Hc2born. London IVCIR 4TF Further cople-c =y be obta,_ncd frcm The Pa-cn. Off,-E Sales Branch, St Marv Cray, Orpington, Kent BR5 3RD Printed by Multiplex technicpies lt(L St Mary Crky. Kent - Con. 1,87- C