WO1980001535A1

WO1980001535A1 - Electrical appliance,for example electrical heating appliances

Info

Publication number: WO1980001535A1
Application number: PCT/GB1980/000021
Authority: WO
Inventors: R Holmes
Original assignee: Prestige Group Ltd; R Holmes
Priority date: 1979-02-05
Filing date: 1980-02-04
Publication date: 1980-08-07
Also published as: GB2041708A; EP0023498A1

Abstract

An electrical appliance, which is particularly but not exclusively suitable for domestic heating or cooking of food, e.g. a high-speed cooker, comprises a vessel (1) for containing material to be heated. The vessel (1) incorporates, preferably at its base, an electrically heating assembly (5) having electrical terminals (9, 11) projecting therefrom. When the vessel (1) is inserted in a predetermined orientation in a cavity (6) in a base unit (7), the terminals (9, 11) are electrically connected to corresponding terminals (10) in the base unit, by manipulation of a rotary switch (14), for energisation of the heating assembly via suitable electrical control circuitry in the base unit (7). The base terminals (10) are located within respective spaced recesses (17) in the switch (14) for rotation therewith between an inoperative position in which contact between respective terminals (9, 11, 10) is inhibited but respective ones of the vessel terminals (9, 11) can enter the respective recesses (17) on correct insertion of the vessel (1) into the cavity (6), and an operative position which, if reached after the inoperative position with the vessel (1) correctly inserted, establishes electrical contact between respective terminals (9, 11, 10).

Description

"ELECTRICAL APPLIANCES, FOR EXAMPLE ELECTRICAL HEATING APPLIANCES"

This invention relates to electrical appliances, for example electrical heating appliances, and particularly but not exclusively to heating appliances suitable for heating or cooking food, e.g. a high speed or "pressure" cooker.

Particularly where an electrical appliance is intended for domestic use, it is important that live electrical terminals are not exposed by, for example, accidental disconnection of the heater assembly from the electrical supply.

According to one aspect of the present invention, there is provided an electrical appliance including a first structural element which incorporates electrical circuitry having exposed first electrical terminals adjacent an external surface portion of the first structural element;■ a second structural element constituting a base unit and defining a cavity for accommodating at least said external surface portion of the first structural element in a predetermined orientation; a rotary switch member of electrically insulating material which is mounted on the base unit within the cavity for rotation with respect to the-base unit between first and second positions; and second electrical terminals carried by the rotary switch member for rotation therewith, each second terminal being disposed behind a respective shield carried by the switch member, whereby, if the switch member is in its first position when the said external surface portion of the first structural element is inserted into the cavity in said predetermined orientation, each second terminal is in registration with a respective one of said first terminals but electrical contact therebetween is inhibited by the intervention of th respective shield, and if the switch member is in its secon position when the said external surface portion of the firs structural element is inserted into the cavity in said predetermined orientation, the first and second terminals are mutually displaced about the axis of rotation of the switch member but subsequent rotation of the switch member to its first position causes each first terminal to pass behind the respective shield and establish electrical contact with the respective second terminal.

According to a second aspect of the present invention there is provided an electrical heating appliance comprising a vessel for containing material to be heated and incorporating an electrical heater assembly which includes exposed first electrical terminals adjacent an external surface portion of the vessel; a base unit definin a cavity for accommodating at least said external surface portion of the vessel in a predetermined orientation; a rotary switch member of electrically insulating material which is mounted on the base unit within the cavity for rotation with respect to the base unit between first and second positions; and second electrical terminals carried by the rotary switch member for rotation therewith, each second terminal being disposed behind a respective shield carried by the switch member, whereby, if the switch member is in its first position when the said external surface portion of the vessel is inserted into the cavity in said predetermined orientation, each second terminal is in registration with a respective one of said first terminals but-electrical contact therebetween is inhibited by the intervention of the respective shield, and if the switch member is in its second position when the said external surface portion of the vessel is inserted into the cavity in said predetermined orientation, the first and second fitted an annular housing 4 in which is contained an electrical heater assembly 5 (Figures 2,3) for use in heating the bottom wall of the body and hence the contents of the vessel during cooking. The housing 4 is provided with feet 4a which support the vessel 1 when the vessel is removably and snugly located in a cavity 6 within a base unit 7, the height of the cavity 6 being sufficient for the base unit to surround a major portion of the vessel. A control panel 8 built into the base unit 7, and with suitable control circuitry (not shown) are provided for controlling the supply of electrical power to the heater assembly 5 via a switch assembly which will now be described with reference to Figures 2 to 5.

The heater assembly 5 has two supply terminals 9 for connection to an electrical power supply e.g. the electricity mains via mains supply terminals 10 carried by the base unit as described in detail hereinbelow. A third coaxial terminal or connector pin 11 is brazed onto the inner side of the heater assembly annular housing 4, the third terminal 11 performing the dual function of earth connector and a connector for a sensor such as a thermistor, the latter function being to put the control circuitry into a suitably operative condition only when the vessel is properly located in the base unit 7 with its electrical terminals 9 connected to the supply terminals 10 in the base unit ready for energisation of the heater assembly. The terminals 9, 11 all project radially inwardly of the annular housing 4 into a space 12 (Figure 1) defined by the annular housing 4 and the bottom wall 2a of the vessel body 2.

At the bottom of the cavity 6 in the base unit 7, mounted on the bottom wall 13 thereof is a disc-like rotary switch member 14, which is made of electrically insulating material such as a plastics material, and which is rotatable relative to the bottom wall 13 about its central axis about a spindle 14a in a plane which is substantially parallel to the bottom wall 13. Rotation of the switch terminals are mutually displaced about the axis of rotation of the switch member but subsequent rotation of the switch member to its first position causes each first terminal to pass behind the respective shield and establish electrical contact with the respective second terminal.

Preferably, the vessel is adapted to withstand pressures above atmospheric pressure, so that the appliance is suitable for use in high speed cooking of food. Conveniently, the heater assembly and the first terminals therefor are located below the underside of the vessel, the vessel being lowered into an upwardly opening recess in the base unit which can accommodate a major portion of the vessel. Preferably the socket member is a disc-shaped member which is shaped so that accidental exposure of the second terminals when live, due for example to premature removal of the vessel from the recess after a heating operation, can be avoided. Reference is now made to the accompanying drawings which illustrate, by way of example, one embodiment of the invention, and of which:-

Figure 1 is a diagrammatic side view of a domestic high speed cooker according to one embodiment of the invention;

Figures 2 and 3 are diagrammatic plan views of the heater assembly and rotary switch of the cooker of Figure 1, respectively showing the switch in its disconnected and connected positions; Figure 4 is a diagrammatic sectional view on line IV-IV in Figure 3; and

Figure 5 is a diagrammatic sectional view on line V-V .in Figure 2.

Referring to Figure 1 a pressure vessel 1 has a cylindrical body 2 defining a chamber for accommodating food to be cooked and a lid 3 which can be releasably secured to the body 2. At the bottom of the body 2 is

OMPI WIPO member 14 is effected normally by means of a rod 15 which is connected by a suitable linkage (not shown) to the switch member 14 and which extends through the base unit wall to protrude from the control panel 8 via an elongate slot therein (not visible) . The arrangement is such that movement of the free end of the rod 15 in either direction produces corresponding rotation of the switch member 14 about its axis- in a respective direction through a limited angle, which in this embodiment is approximately 17°. The ends of the slot defining the limits of the movement of the rod 15 in each direction also define respectively inoperative (i.e. disconnected) or operative (i.e. connected) conditions of the pairs of terminals 9,11 and 10, as described below. A portion of the periphery of the switch member 14 is provided with a downwardly extending skirt portion 27 which extends through a corresponding arcuate slot 13d in the bottom wall 13. As the rod 15 reaches the limits of its movement, the skirt portion 27 engages the respective ends of the slot 13d, thus providing accurate control of the rotation of switch member 14 by the movement of rod 15.

The switch member 14 is provided with a number of recesses 17 which are spaced about its axis. Each terminal 10 is mounted in the switch member 14 so as to protrude downwardly through a corresponding slot 13a. in the bottom wall 13 and upwardly into the inner end of a respective one of the recesses 17, as best seen in Figure 4. The electrical connection 10a for each terminal 10 and the slot 13a in the bottom wall 13 are adapted to permit terminal 10 to move in an arcuate path as the socket member 14 is rotated, without hindrance. Preferably, as illustrated, the recesses 17 are formed in the periphery of the switch member 14. As best seen in Figure 5, each recess 17 need not extend completely through the thickness of the switch member, but has a mouth 18 in the upper broad surface 19 of the switch member which is angularly spaced about the axis of rotation of the switch member 14 from the respective terminal 10 at the inner end of the recess. Thus, the terminal 10 is at all times covered by a shield 20 located immediately thereover, whatever the position of the rod 15.

Preferably, however, a slot 18A may be provided below the mouth 18 of each recess 17, to allow water, crumbs etc. to fall through the switch member and thereby avoid the possibility of electrical shirt-circuits or non-engagement of the electrical terminals 9,10,11 due to "foreign bodies" in the recesses. The socket member is urged upwardly of the bottom wall 13 by means of a spring 21 which is located in a central depression 13b in the bottom wall 13 and engages the underside of the switch member 14.

When the vessel is lowered into the cavity 6 in the base unit, it is guided into a predetermined orientation therein by means of at least one recess 22 (Figure 1) in the upper side walls 23 of the base unit which accommodate the respective handle or handles 24 of the vessel. The correct predetermined orientation of the vessel in cavity 6 can be defined as being achieved when the vessel is positioned so that the terminals 9,11 are in vertical registration with the respective terminals 10 when the switch member is in its operative position (i.e. rod 15 is in position B) . The spacing of each terminal 10 and the mouth 18 of its recess 17 about the rotary axis of the switch member is such that when the rod 15 is in its inoperative position A (Figure 2) and the vessel is lowered into the cavity 6 correctly, the . terminals 9, 11 are each in registration with and pass freely through the mouths 18 of respective recesses 17 until the feet 4a. or the annular housing 4 engage in correspondingly formed depressions 13£ in the bottom wall 13-(Figute 4) . At this time the end of each terminal 9,11 within the respective recess 17 engages a guide surface 25 in the recess 17, the surface 25 being urged thereagainst by the spring 21. The dimensions of each ^* recess 17 are such that the switch member 14 is thus

OMP , IP located within the space 12 surrounded by the housing 4, there being sufficient clearance to permit subsequent rotation of the switch member 14 relative to the vessel in the direction of arrow C (Figure 5) into its operative position, the end of each terminal 9,11 being guided in its recess 17 during this rotation between guide surfaces 25 and 26. Once the operative position is reached, each of the terminals 9,11 is in the position shown in dotted lines in Figure 5, i.e. it is in vertical registration with the respective terminal 10 and in electrical contact therewith due to the upward biassing action of spring 21 on switch member 14. Any attempt to remove the vessel from the recess 6 unless the switch member 14 is returned to its inoperative position will be foiled by the engagement of the terminals 9,11 below the respective shields 20.

If, on the other hand, the vessel is lowered correctly into the cavity 6 , but the switch member is in its operative position i.e. the terminals 9,11 are in vertical registration with the respective terminals 10 during lowering of the vessel, then the terminals 9,11 will not enter the recesses 17. Instead the terminals 9,11 will engage the upper surfaces of the shields 20, causing the switch member 14 to be depressed downwardly against the action of spring 21, so that the skirt portion 27 on the switch member 14 is pushed still further through slot 13d in the bottom wall 13. The extent of the movement of the switch member 14 in these circumstances is indicated by arrow D in Figure 4. Clearly subsequent rotation of switch member 14 into its inoperative position permits the speedy engagement of the terminals 9,11 in the mouths of the respective recesses 17 due to the upward bias of spring 21 , and further rotation of the switch member 14 back to its operative position establishes electrical contact between the respective terminals 9,10 and 11 as described above.

It will be observed that each terminal 10 is surrounded by the electrically insulating material of the switch member 14 a construction which provides protection against possible short circuits between the terminals 10 when the vessel is in position in the cavity 6 with the terminals 9,10,11 respectively in electrical contact and meets with electrical standard safety requirements during a cooking operation.

OMPI

Claims

CLAIMS :

1. An electrical appliance including a first structural element which incorporates electrical circuitry having exposed first electrical terminals adjacent an external surface portion of the first structural element; a second structural element constituting a base unit and defining a cavity for accommodating at least said external surface portion of the first structural element in a predetermined orientation; a rotary switch member of electrically insulating material which is mounted on the base unit within the cavity for rotation with respect to the base unit between first and second positions; and second electrical terminals carried by the rotary switch member for rotation therewith, each second terminal being disposed behind a respective shield carried by the switch member, whereby, if the switch member is in its first position when the said external surface portion of the first structural element is inserted into the cavity in said predetermined orientation, each second terminal is in registration with a respective one of said first terminals but electrical contact therebetween is inhibited by the intervention of the respective shield, and if the switch member is in its second position when the said external surface portion of the first structural element is inserted into the cavity in said predetermined orientation, the first and second terminals are mutually displaced about the axis of rotation of the switch member but subsequent rotation of the switch member to its first position causes each first terminal to pass behind the respective shield and establish electrical contact with the respective second terminal.

2. An electrical heating appliance comprising: a vessel for containing material to be heated and incorporating an electrical heater assembly which includes exposed first electrical terminals adjacent an external surface portion of the vessel; a base unit defining a cavity for accommodating at least said external surface portion of the vessel in a

5 predetermined orientation; a rotary switch member of electrically insulating material which is mounted on the base unit within the cavity for rotation with respect to the base unit between first and second positions; and

10 second electrical terminals carried by the rotary switch member for rotation therewith, each second terminal being disposed behind a respective shield carried by the switch member, whereby, if the switch member is in its first position when the said external surface portion of the - 15 vessel is inserted into the cavity in said predetermined orientation, each second terminal is in registration with a respective one of said first terminals but electrical contact therebetween is inhibited by the intervention of the respective shield, and if the switch member is in its

20 second position when the said external surface portion of the vessel is inserted into the cavity in said predetermined orientation, the first and second terminals are mutually displaced about the axis of rotation of the switch member but subsequent rotation of the switch member

25 to its first position causes each first terminal to pass behind the respective shield and establish electrical contact with the respective second terminal.

3. An electrical heating appliance as claimed in 30 claim 2, in which the switch member is substantially disc-like, and in which each second terminal is carried by the switch member so as to be exposed within an inner portion of a respective one of a plurality of recesses formed in said switch member and spaced about the rotary 35 axis thereof, the mouth of each recess being located in one broad face of the switch member and being spaced from said respective second terminal about the rotary axis of the switch member, the switch member being disposed in said cavity with said one broad face facing outwardly so as to be adjacent to said external surface portion of

5 said vessel when the latter is inserted into the cavity, whereby, if the switch member is in its second position when the external surface portion of the vessel is inserted into the cavity as aforesaid each first terminal is in registration with and enters the mouth of a respective

10 one of said recesses, so that said subsequent rotation of the switch member to its first position causes the first terminals to enter the inner portions of the respective recesses and therein contact said respective second terminals. - 15

4. An electrical heating appliance as claimed in claim 3, in which said recesses are formed at the periphery of the switch member.

20 5. An electrical heating appliance as claimed in any of claims 2 to 4, in which each shield constitutes an abutment with which the respective first terminal is engageable when the external surface portion of the vessel is accommodated in the cavity and the first and

25 second terminals are in electrical contact as aforesaid in order to inhibit removal of said vessel before the switch member is rotated back to its second position.

6. An electrical heating appliance as claimed in 30 any of claims 2 to 5, in which means are provided for resiliently urging the switch member, and hence the second terminals carried thereby, outwardly of the wall of the cavity on which said switch member is rotatably mounted.

35 7. An electrical heating appliance as claimed in any of claims 2 to 6, in which said rotary switch member is manually rotatable via a rod which protrudes outwardly of said base unit through an elongate slot therein.

8. An electrical', heating appliance as claimed in any of claims 2 to 7, in which said first terminals

5 include a sensor which, when in electrical contact with a corresponding one o-f, said second terminals, is arranged to activate electrical -control circuitry provided in the base unit thereby to pexaiit the supply of electrical power to the second terminals and hence energisation of

10 said electrical heater assembly.

9. An electrical heating appliance as claimed in any of claims 2 to 8, in which said cavity in the base unit is shaped so that said vessel is moved in a

- 15 substantially downward direction as the external surface portion thereof is inserted into said cavity.

10. An electrical heating appliance as claimed in any of claims 2 to 9, in which the dimensions of the

20 cavity are such that a major portion of said vessel can be accommodated therein.

11. An electrical heating appliance as claimed in any of claims 2 to 10, in which said external surface

25 portion of said vessel is located on its underside.

12. An electrical heating appliance as claimed in claim 11, in which said electrical heater assembly is incorporated in an annuisar housing located on the underside

30 of the vessel, the first terminals protruding from the inner circumferential surface of the annular housing, the arrangement being such that when the bottom portion of the vessel is located in said cavity, the said annular housing surrounds said rotary switch member.

35

13. An elecisricad'-.heating appliance as claimed in any of claims 2 to i£, sr-^which said vessel is adapted to withstand pressures above atmospheric pressure whereby the appliance can be used in the high speed cooking of food.

OMPI Λ, WIPO _«*,