GB2303977A

GB2303977A - Cordless electric kettle

Info

Publication number: GB2303977A
Application number: GB9622460A
Authority: GB
Inventors: Leslie Alexander Gort-Barten
Original assignee: Dualit Ltd
Current assignee: Dualit Ltd
Priority date: 1996-10-29
Filing date: 1996-10-29
Publication date: 1997-03-05
Anticipated expiration: 2016-10-29
Also published as: GB9622460D0; GB2303977B; GB9703285D0

Abstract

A cordless electric kettle comprises a power base unit 10 to be connected to a power supply and an extension unit 15 connected to a kettle body 14, the units being moulded from plastics and each incorporating an electrical connector 13, 17 located substantially on the kettle vertical axis, the electrical connectors being interengagable when the kettle is placed on the base unit at any orientation around the axis. The kettle includes an ON/OFF switch (20, figure 4) having a manually operable actuator 23,25, biasing means (32) biasing the switch to an OFF position, a plunger (30) associated with one of the connectors and arranged to be depressed through a predetermined distance when the connectors are fully engaged, to disable the biasing means such that the ON/OFF switch may remain in the ON position. On separation of the base and extension unit, the biasing means will be restored to urge the switch to the OFF position before the electrical connection between the connectors is broken. The base and extension units are designed to mate successfully despite small inaccuracies in the dimensions of the moulded parts. In one example, one or more of the kettle feet projects downwardly further than the others, to always engage the opposing surface of the base. Alternatively, the moulding is slotted adjacent to the feet, to give limited axial movement, or the base unit electrical connector 13 is sprung mounted.

Description

CORDLESS ELECTRIC KETTLE This invention relates to cordless electrical kettles.

Conventional cordless kettles have a power base unit to be connected to a power supply and a base extension unit connected to the kettle, the base unit and extension unit each including an electrical connector, with the connectors arranged to electrically interconnect when the kettle is placed on the base unit. The interface between the two units is circular to allow the units to be connected to each other at any angle about the vertical axis of the units. To achieve proper connection one of the connectors fits into a circular section cylindrical recess in the other of the connectors, conventionally the base unit has an upstanding connector fitting into a recess in the connector of the kettle extension unit. It is a requirement that the two connectors are in firm end to end contact.

Such a kettle has a lever-type ON/OFF switch, the actuator of which can be moved to an ON connecting position to complete the electrical circuit when the units are connected, and which will be automatically moved to the OFF position when the water in the kettle boils.

In addition, in order to prevent arcing between the connectors if the kettle is lifted while the circuit is completed, a biasing means is provided which biases the switch to an OFF position if the kettle is lifted and before the contactors cease to make electrical contact. The biasing means acts on a downwardly extending plunger within the socket recess, the plunger being coupled to an operating arm which interacts with the ON/OFF switch lever.

Depression of the plunger as a result of a firm connection of the connectors removes the biasing from the ON/OFF switch lever so that it can stay in the ON position. The plunger is necessarily spaced radially to one side of the vertical axis of the units. Space constrictions on conventional kettles of this type means that the vertical movement of the plunger between its operative and inoperative conditions is small, not exceeding about 1 mm.

The base unit and the extension unit are both conventionally moulded from plastics materials and the connectors securely fastened thereto so that no vertical movement of the connectors relative to the mouldings can occur.

Because of the tolerances which must be allowed for in the moulding manufacture and because of warping of the mouldings, it is the practice, in order to ensure proper firm contact in every product between the connectors (and the depression of the plunger), that the units are designed to allow a small gap between the surfaces of the mouldings surrounding the connectors, when the connectors are interconnected. A gap of 0.5 to 1 mm is usually built into the design.

However this gap leads to vibration/wobble of the kettle in use which is undesirable. An object of the present invention is to prevent/reduce the amount of vibration or wobble in a cordless kettle of this type.

Conventionally the base of the extension unit is formed with three equal feet having rounded lower surfaces and it is these lower surfaces which are, by design, spaced from the upper surface of the base moulding.

The present invention, in one aspect, provides a cordless kettle in which at least one of the feet (or other engagement means) on the base of the kettle extension is longer than another or the others of the feet (or other engagement members). Preferably the foot or feet on the side of the extension remote from the plunger is/are longer than the other foot or feet.

The longer foot/feet may be, for example, about 1 mm (0.5 to 2mm) longer than the other foot or feet. The other foot or feet will be dimensioned to produce a nominal gap.

With this arrangement the longer foot will always contact the upper surface of the power unit and will prevent wobble or vibration but because the kettle can tip slightly on the base unit minor inconsistencies in dimensions of the moulded units can be accommodated whilst still ensuring firm contact of the connectors and full depression of the plunger.

The longer foot could be sprung so that it may move inwardly by a small distance. This could in a preferred form be achieved by providing a slit or slits in the base moulding adjacent the foot.

In another form the invention provides a kettle in which the feet (or other engagement members) extending outwardly from one unit theoretically all substantially engage the surface of the other unit, when the connectors are fully engaged, but all, or at least those feet which are on the same side of the extension unit as the plunger, are sprung so that they can move inwardly slightly. The spring loading would have to be sufficiently weak that the weight of the kettle plus minimum water would move the feet inwardly if necessary.

In yet a further aspect the invention provides a cordless kettle in which the connector in the base unit is vertically movable relative to the base unit moulding but is biased upwardly with a biasing force sufficiently great to ensure that the units will always be fully connected and the plunger depressed. This arrangement would again allow the base unit and extension unit mouldings to be brought into engagement when the connectors are fully connected despite any slight inconsistencies in dimensions from the theoretical just engaging dimensions.

One embodiment of cordless kettle, in accordance with the invention, will now be described, by way of example only, with reference to the accompanying drawings of which: Figure 1 is a central section through the relevant parts of a cordless kettle, Figure 2 is a central section at right angles to the section of Figure 1, Figure 3 is a diagrammatic view of interengageable parts of the kettle in a switch OFF condition, Figure 4 is a diagrammatic view of the interengaging parts of Figure 3 in a switch ON position, Figure 5 is a diagrammatic underneath plan view of the base extension on a smaller scale, and Figure 6 parts A and B show diagrammatically two alternative forms of sprung foot.

A power base 10 of a cordless kettle comprises a plastic moulding 1 2 in which is fixed an electrical connector 1 3 secured to prevent any relative vertical movement between the moulding and connector. A minor relative horizontal movement is allowed for. A kettle body 1 4 has firmly secured thereto a base extension unit 1 5 comprising a plastics material moulding 1 6 to which is firmly secured an electrical connector 1 7 designed to interconnect with the connector 1 3. The base unit 10 is arranged to be connected to a power source and the connector 1 7 is electrically connected to the kettle heating element.

The mouldings 1 2 and 1 6 are circular in plan view and the connectors are circular on and about the vertical axis of the kettle, with the connector 1 7 defining a socket 1 8 to accommodate the upstanding connector 1 3 so that the units can be electrically interconnected at any angle about the vertical axis.

The electrical circuit includes an ON/OFF switch, indicated diagrammatically at 20 in Figure 3 and including a fixed conductor 21 mounted to the connector 17 and a movable conductor 22 located on a switch actuating lever 23 pivotted about a horizontal axis at 24. The outer end 25 of the lever can be manually depressed to move the conductors 21 and 22 into contact to effectively complete the electrical circuit of the kettle.

Means, not shown, are provided for restoring the lever 23 to its OFF position when the water in the kettle boils.

A plunger 30 extends downwardly into the socket 1 8 of connector 1 7 and is biased downwardly, as shown diagrammatically in Figure 3, by a spring 32. Plunger 1 3 also carries a substantially radially extending arm 33, located to interact with a part 34 of the lever arm 23. With the plunger in its downwardly biased position, shown in Figure 3, the arm 33 acts on the lever if it is moved to the ON position of the switch and biases it back to its OFF position. Only when the plunger is depressed, by pushing the electrical connector 1 3 into the socket 1 8 to form a firm electrical connection, can the ON/OFF switch be left in the ON position to complete the circuit, as shown in Figure 4.The plunger thereby ensures that the circuit is broken before the electrical connectors 1 3 and 1 7 are disconnected if the kettle is lifted from the base when the circuit is completed. This prevents arcing between the connectors 13 and 17.

- The cordless kettle as above described is aiready known. With this type of kettle the plunger movement is small - round 1 mum. It has been found that the mouldings cannot be consistently produced to sufficiently close tolerances, allowing also for warping of the mouldings, to ensure that the plunger is always fully depressed on connection of the connectors if the mouldings are nominally dimensioned to just contact one another when the connectors are fully connected. For this reason it has been normal to design the units with a built-in gap between the base of the extension unit and the upper surface of the power unit of about 1 mum, so that on connection the kettle is supported solely by the centrally located connectors.This leads to unacceptable vibration and wobbling of the kettle and can lead to the kettle tipping to unlatch the ON/OFF switch before the water has boiled.

Conventionally the base of the extension unit is formed with three equiangularly spaced feet near the outer edge of the base surface and the gap is left between the rounded lower surfaces of these feet and the upper substantially flat surface of the base unit. In the drawings these feet are indicated at 41, 42 and 43, with the feet 41 and 42 being located on the same side of the extension unit as the plunger and foot 43 being located radially opposite the plunger. According to the present invention the foot 43 (or other engagement member) is made longer than the other feet by approximately lmm but in the range 0.5 to 2mm with the other feet still being dimensioned to theoretically leave a gap of approximately 0.5mm between their lower surfaces and the upper surface of the base unit.With advantage the longer foot is sprung so that it can move inwardly from its rest position. This is preferably achieved as shown in Figures 6A and 6B by providing a slit 44 around three sides of the foot or two slits 45 one on either side of the foot. Other springing could be used.

In an alternative arrangement all the feet are lengthened so that there is no gap built into the design (nominally the mouldings just contact one another on full interconnection of the connectors) but at least some of the feet, preferably the foot or feet on the same side of the unit as the plunger, are sprung, for example, as shown for the foot 43 in Figure 6. This spring loading must be such that the weight of the kettle plus a minimum amount of water in it will overcome the springing and depress the feet if necessary to overcome dimensional errors to allow full interconnection. The feet or other engagement members could be upstanding from the base and able to move downwardly under the kettle weight.

As a yet further alternative the connector unit 1 3 could be mounted in the moulding 1 2 for limited vertical movement but biased upwardly. The feet could then be dimensioned to theoretically engage the upper surface of the power base, with inconsistencies in the dimensions due to tolerances in manufacture or warping of the mouldings being taken up by the movement of the connector.

Claims

1. A cordless electrical kettle comprising a power base unit to be connected to a power supply and an extension unit connected to a kettle body, the units being moulded from plastics material and each incorporating an electrical connector located substantially on the kettle vertical axis, the electrical connectors being interengagable to form an electrical connection with one another when the kettle is placed on the base unit at any orientation around the axis, an ON/OFF switch movable to an ON position by a manually operable actuator, biasing means biasing the switch to an OFF position, a plunger associated with one of the connectors and arranged to be depressed through a predetermined distance when the connectors are fully engaged, depression of the plunger by the predetermined distance being arranged to disable the biasing means such that ON/OFF switch may remain in the ON position, the predetermined amount being such that on separation of the base unit and extension unit the biasing means will be restored so as to urge the switch to the OFF position before the electrical connection between the connectors is broken, the base unit and extension unit having engagement parts respectively on upwardly facing and downwardly facing surfaces at least some of which are arranged to substantially always engage one another when the plunger is sufficiently depressed to disable the biasing means despite small inaccuracies in the dimensions of the moulded units, said engagement being achieved by:: a) making the or each engagement part on the side of the extension unit opposite the plunger longer than the or each engagement part on the same side as the plunger, or b) by making one or more of the engagement parts with limited axial movement relative to the remainder of the moulding, or c) by spring mounting the electrical connector in the base unit for limited axial movement in its moulding.

2. A kettle according to Claim 1 in which the engagement parts comprise a substantially level upper surface portion of the base unit and downwardly extending feet on the extension unit.

3. A kettle according to Claim 2 in which there are three downwardly extending feet on the extension unit with a single foot substantially radially opposite the plunger extending downwardly for a greater distance than the other two feet.

4. A kettle according to Claim 3 in which the longer foot is substantially 0.5 to 2mm longer than the other feet.

5. A kettle according to Claim 3 in which the longer foot is substantially 1 mm longer than the other feet.

6. A kettle according to any of Claims 3 to 5 in which the mouldings and connectors are dimensioned to theoretically leave a gap of substantially 0.5mm between the shorter feet and the surface of the base unit when the connectors are fully engaged.

7. A kettle according to any of Claims 2 to 6 in which one or more of the feet are sprung by providing a slot or slots in the moulding adjacent one or more of the feet.

8. A kettle according to any of Claims 1 to 7 in which the electrical connector of the base unit fits into a recess in the electrical connector of the extension unit and the plunger is biased to extend into the recess to be depressed by engagement with the end face of the base unit connector.

9. A kettle according to any of Claims 1 to 8 in which the plunger is movable through a distance of substantially 1 mm.

10. A kettle according to Claim 1 in which the connector of the base unit is mounted for limited vertical movement in its moulding and including spring biasing means biasing the connector upwardly.

11. A kettle according to Claim 10 in which the engagement parts of the mouldings are dimensioned to theoretically just contact one another when the connectors are fully engaged without axial movement downwardly of the base connector.

1 2. A cordless electrical kettle substantially as described herein with reference to or as illustrated in the accompanying drawings.