GB2426695A - Safety system for electrically operated kitchen devices - Google Patents

Abstract

A safety system intended for electrically operated kitchen appliances, such as blenders and food processors comprises a clutch that selectively couples and decouples the drive between a motor and an implement rotatable about an axis within a container. The clutch reciprocates between a first decoupling position and a second coupling position and is configured to require the application of a force in excess of 20 newtons for movement to the second coupling position against a resilient means. The pressure may be exerted via the lower rim of the side wall of a bottomless goblet. The clutch may comprise a plurality of spring members (44, 45, 46) symetrically distributed about the axis, an annular spring cover (50) having recesses for symetrically distributed screw pillars (21, 22, 23).

Description

1 2426695

SAFETY SYSTEM

This invention relates to safety systems and it relates especially, though not exclusively, to such systems for electrically operated kitchen appliances such as blenders, food processors and the like.

Many appliances used in the kitchen contain cutting or macerating knives or blades which can be rotated at reasonably high speeds by means of powerful electric motors and thus can present significant risk to users, as well as to children and others who may interfere with unattended appliances, unless appropriate safety measures are incorporated.

Most kitchen appliances manufactured by reputable companies have safety systems intended to protect users, and others, from accidental contact with rotating knives or blades, and most existing systems work reasonably well under most circumstances. However, there is a continual quest for safety systems exhibiting improved security and robustness, and moreover legislation is continually being introduced to ensure that adequate safety standards are established and met. The present invention aims to provide a safety system conforming to all current safety legislation and which, moreover, is user friendly. The invention also aims to provide an electrically powered kitchen appliance incorporating such a safety system.

Safety systems based around a clutch-like operator have been recently proposed, and two such systems are disclosed in our UK patent applications Nos. GB 0412087.9 and GB 0419036.9. Such systems are effective and user-friendly, but can be quite costly to implement in a manner affording the reliability and performance levels required in use.

The present invention relates to a simpler system which is directed at a current safety requirement whereby a product is defined as safe if it presents a sufficiently high mechanical resistance to a force needed to activate it.

According to the invention there is provided a safety system for selectively permitting a motor to drive an implement, within a container, in rotation about an axis; the system comprising a drive coupling, mounted for reciprocating motion along said axis between a first position, de-coupling the motor from the implement, and a second position coupling the motor to the implement; resilient means urging said drive coupling towards said first position and configured to require the application of a force in excess of 20 Newtons to move said drive coupling to said second position.

In a preferred embodiment, the arrangement is such that said force can be applied only by the action of locating said container correctly in place to contain said implement.

Preferably, the container comprises a bottomless goblet having a base side-wall adapted to be located in place around said implement by a readily releasable and securable means such as screw threads or a bayonet fixing. By this means, the implement can be utilised with different goblets.

It is further preferred that the resilient means is responsive to pressure exerted via the lower rim of the side-wall of said bottomless goblet.

The resilient means preferably comprises a plurality of spring members symmetrically distributed in angle at a common radius around said axis.

In a particularly preferred embodiment, three spring members are provided; said spring members being disposed in substantial alignment with said axis.

It is further preferred that an annular spring cover is provided; said cover being configured to constrain said spring members to respective, defined locations.

The invention also encompasses a kitchen appliance incorporating a safety system in accordance with any of the foregoing.

In order that the invention may be clearly understood and readily carried into effect, one embodiment thereof will now be described with reference to the accompanying drawings, of which: Figure 1 shows, in exploded and perspective view, essential components of a safety system in accordance with said embodiment of the invention; Figure 2 shows, in cross-sectional view, part of a system in accordance with one example of the invention, with the goblet removed and the drive coupling in its first (safe) condition; and Figure 3 shows, in underside plan view, the system in the operational condition of Figure 2.

Referring now to the drawings, in which consistent numbering is adopted throughout, certain components of the system to be described are housed within a base (not shown) of a domestic electrical appliance; in this case a liquidiser/blender. A drive coupling 10 is configured to be driven in rotation by the vertically disposed output shaft of an electric motor (not shown) fixedly mounted in any convenient manner beneath the base.

The electric motor may be of any type convenient and suitable for use in the context of the appliance in question.

The drive coupling 10 is supported by a collar-like housing 20, which also supports, on its upper surface, a chopping or blending implement 30 formed with a plurality of blades 31. Rotation of the coupling 10, by means of a suitably shaped configuration on the motor shaft sliding into and interlocking with a cruciform slot 11 in the coupling, causes rotation of the implement 30.

Protruding axially downwards from the housing 20 are three screw pillars 21, 22 and 23, with centres disposed at intervals of 120 degrees about the axis of the system, and three spring locating pillars such as 24 and 25 (the third of these cannot be seen in the drawing), similarly located but interleaved with the screw pillars in angular position.

A respective linear coil spring 44, 45 or 46 is located over each of the spring locating pillars such as 24 and 25.

A spring cover 50 is provided on its outer surface with arcuate cut-outs 51, 52 and 53, located and dimensioned to accommodate respective ones of the screw pillars 21 to 23, and capable of sliding relative thereto. The spring cover 50 also bears a respective hollow and tubular upstand, such as that shown at 56, positioned and dimensioned to receive each of the spring pillars such as 24 and 25; the spring pillars being configured to slide within the upstands as the housing 20, together with its supported components, moves axially of the system to engage/disengage the motor drive shaft and the coupling 10. By this means, the desired axial movement is permitted, whilst constraining the springs closely to a defined location, thereby reducing risk of the springs distorting under pressure and jamming the system.

A retaining ring 60 is provided to retain the various components of the system. It is provided with through-holes 61, 62 and 63 through which screws 71, 72 and 73 can be inserted to engage with screw-threads formed in the lower ends of respective screw pillars 21, 22 and 23.

It will be appreciated that, in operation, the springs 44, 45 and 46 are normally configured to urge the housing 20, and thus the coupling 10, upwardly relative to the retaining ring 60, which is fixed in relation to the motor housing. This is the position shown in Figure 2; the first or safe position, in which the coupling 10 is urged upwardly sufficiently far relative to the motor housing that the drive shaft of the motor cannot engage with it. Thus, in this position, even if the motor is activated, the bladed implement 30 will not rotate.

When a goblet is screwed or bayoneted on to the blade housing, the force exerted thereby exceeds the predetermined force of 20 Newton needed to overcome the resilient upwardly directed force provided by the springs 44 to 46 and compresses the springs, thereby permitting the drive coupling 10 to be moved downwards to its second, or operating position, at which it engages with the motor drive shaft and can thus be driven thereby.

The safe condition, therefore, obtains at all times when the container is removed from the base housing 20. This, as mentioned, is the condition shown in Figure 2, which is viewed from the section line A-A on Figure 3.

It will be appreciated that the system as described herein provides protection not only in circumstances where the electric motor might be actuated by mischievous, malicious or inadvertent operation of a power switch, but also in circumstances where a short circuit or other electrical mischance or breakdown actuates the motor independently of the power switch.

With general reference to the scope of this invention, it is pointed out that, whilst, in the specific example of the invention described above with reference to the drawings, there are three screw pillars and three spring locating pillars which form complete and symmetrically interleaved sets extending all around the motor drive axis, other arrangements are possible. In particular, there may be differing numbers of screw and spring pillars and/or either or both sets of pillars need not be continuously disposed over a full 360 degrees. It is in any event preferred, however, that symmetrical arrangements of at least the spring pillars are utilised, as this promotes even spring loading, reliable operation and longevity of the system.

Furthermore, alternative mechanisms are readily available which do not employ screw pillars at all. For example, there may be provided opposing members co-operatively shaped to snap fit together.

Moreover, although the particular example of the invention described with respect to the drawings utilises a coaxial configuration for the motor and the rotatable implement, it will be appreciated that the respective axes of these components could be displaced laterally from one another if desired, by means for example of gearing and/or any other convenient form of drive translation system.

Claims (10)

1. CLAIMS: 1. A safety system for selectively permitting a motor to drive an

   implement, within a container, in rotation about an axis; the system comprising a drive coupling, mounted for reciprocating motion along said axis between a first position, de-coupling the motor from the implement, and a second position coupling the motor to the implement; resilient means urging said drive coupling towards said first position and configured to require the application of a force in excess of 20 Newtons to move said drive coupling to said second position.
2. 2. A system according to claim 1, wherein the arrangement is such that said force can be applied only by the action of locating said container correctly in place to contain said implement.
3. 3. A system according to claim 1 or claim 2, wherein the container comprises a bottomless goblet having a base side-wall adapted to be located in place around said implement by a readily releasable and securable means such as screw threads or a bayonet fixing.
4. 4. A system according to any preceding claim, wherein the resilient means is responsive to pressure exerted via the lower rim of the side-wall of said bottomless goblet.
5. 5. A system according to any preceding claim, wherein the resilient means comprises a plurality of spring members symmetrically distributed in angle at a conmTlon radius around said axis.
6. 6. A system according to claim 5, wherein three spring members are provided; said spring members being disposed in substantial alignment with said axis.
7. 7. A system according to claim 5 or claim 6, wherein an annular spring cover is provided; said cover being configured to constrain said spring members to respective, defined locations.
8. 8. A system according to any of claims 5, 6 or 7, further comprising a plurality of pillars for screw fixings interleaved in angle with said spring members.
9. 9. A safety system substantially as herein described with reference to, and/or as shown in, the accompanying drawings.
10. 10. A kitchen appliance incorporating a safety system in accordance with any preceding claim.