AU2005201023B2 - Safety Interlock for Blender - Google Patents

Description

Safety Interlock for Blender Field of the Invention The invention relates to safety interlocks and more particularly to an interlock for a blender or other kitchen appliance. Background of the Invention An electric blender consists of a number of separate cooperating parts. These parts include, for example, a jug, jug seal, jug base (with blades) and motor housing. Where the blades are removable from the jug, these parts may be disassembled on a regular basis for cleaning and must be re-assembled prior to use. They must be assembled easily, and not leak when assembled. Improper assembly may also present a safety hazard, for example, operation of the blades without the presence of the jug. Improper assembly also extends to having the jug's threads cocked or incompletely screwed down into the base or having the base incompletely seated in the housing. It is also an advantage to provide the user with a device that can be assembled correctly in more than one orientation. Here orientation refers to the orientation of the jug around the axis of the motor's output shaft. Multiple orientations favours left and right handed users as well as more versatile countertop placement and is less demanding of the user in general. One way of safeguarding the user against improper assembly is to electrically disable the motor with an interlock safety or cut out switch. The switch disables the motor unless certain parts are in position and the switch is thereby depressed. Switches of this type are known in, for example, blenders and food processors. Prior art interlock switches are not able to tolerate a variety of jug assembly positions and some exert a significant counterforce against the parts that they 1.

make contact with. This counterforce may make assembly difficult or cause a jug such as a plastic jug to become unseated. Objects and Summary of the Invention It is an object of the invention to provide an appliance with an interlock which overcomes some of the disadvantages of prior art interlock safety switches. It is also an object of the invention to provide a blender with an interlock which overcomes some of the disadvantages of prior art interlock safety switches. Accordingly there is provided an appliance with a motor housing having a seat in which and from which protrudes the motor's output shaft. The seat receives a base of a vessel. The base contains a plate or ring which surrounds a coupling for the shaft. One or more fingers extend from the ring through a floor of the base. A bottom portion of the ring mechanically cooperates with one or more electrical cut out switches mounted in the seat. In preferred embodiments the bottom portion of the ring comprises a lip portion which is adapted to enter a slot in the switch and activate it, when the appliance is properly assembled. In another embodiment, compression springs are interposed between the ring and the base. Brief Description of the Drawing Figures Figure 1 is a perspective view of blender according to the teachings of the present invention. Figure 2 is a perspective view, partially sectioned, of blender jug base according to the teachings of the present invention. 2 Figure 3 is another perspective view, partially sectioned, of a blender jug base according to the teachings of the present invention. Figure 4 is an exploded perspective view of a blender jug base according to the teachings of the present invention. Figure 5 is a top plan view of a jug base and seat. Figure 6 is another exploded perspective view of a blender jug base according to the teachings of the present invention. Best Mode and Other Embodiments of the Invention As shown in Figure 1, a blender 10 comprises a housing 11 for a motor and various user controls. The top of the housing forms a seat 12 having in this example internally scalloped circumferential walls 17 for receiving the cooperating base 14 of a jug 15. The output shaft of the motor and the motor side coupling (not shown) protrudes into the seat. As shown in the example of Figures 2-4, the base 14 features external scallops 16 above which mate in a variety of orientations with the internal scallops 17 of the seat 12. The base also has a flat floor 18 above which is located a circular polymeric seal 19. The floor 18 surrounds a domed area 20 through which extends the shaft 21 which connects the jug-side coupling 22 to the blades 23. As better shown in Figure 5, the floor 18 of the base 14 has one or more through openings or slots 24 formed through it. The underside of the base 14 has a number of descending and internally threaded posts 25 which are received by cylindrical guides 26 which are part of a ring 27 which fits within the underside of the base 14. In this specification and the claims that follow, the term "ring" encompasses any shape having a central opening that at least partially surrounds the blender's shaft or coupling, even when the central opening is not round. The ring is piloted on the posts 25 and is free to reciprocate axially. The ring floats on (optional) compression springs 30 which are retained at one end by flanges 31 formed at the top of the guides and at the other end by 3 threaded retaining screws 32 which are driven into the posts 25. Note that one spring is located adjacent to each finger in this example. The ring also has at least one, and in this example, four flattened fingers 33 which extend up through the slots 24. The slots are thus equal in number to the number of fingers 33 and equally spaced from one another. The underside of the ring 27 forms (at least in part) an edge, blade or lip portion 35 of reduced thickness. As will be explained this lip portion 35, when correctly aligned, can enter a slot 41 formed in a raised cap 42 formed on a safety switch 40 located on the seat. In preferred embodiment the slot 41 will not admit a human finger. As shown in Figure 2, the springs 30 urge the ring toward the floor of the base and thus the fingers 33 into full extension through their slots 24. In this position, the lip 35 can not make contact with the electrical switch 40 which is found in the seat 12. Accordingly, the switch 40 will not register that the blender is assembled correctly and does not, regardless of the use of the operator switches, permit power to be transmitted to the motor. As shown in Figure 3, when the jug is properly screwed down onto the ring seal 19, mechanical (and equal) contact is made with all of the fingers 33. This causes them to compress the springs 30 as they descend. This drives the ring 27 down into the base 14. If the device is assembled correctly and when the ring 27 is depressed sufficiently, a portion of the lip 35 of the ring 27 enters a slot or opening 41 formed in the top of the switch 40. When the jug is screwed in sufficiently, the lip 35 makes contact with the working contact of tle switch by fitting through the slot 41. Depressing the switch allows power to be transmitted to the motor. A safety indicator light may also be illuminated for the user's benefit. In effect, this arrangement makes it impossible to activate the motor unless the jug is fully screwed into its base and the base is correctly positioned in the seat 12. The particular example given here provides four guide and spring sets 26, 30 and 4 eight matching scallops on each of the seat 12 and base 14. This provides for eight orientations or positions in which the user can correctly insert the base into the seat. Note from Figure 5, that the slots 24 and thus the fingers 33 are located between adjacent scallops 16, 17. In another embodiment, and as exemplified by Fig. 6, the springs 30 maybe omitted or effectively replaced by another source of resilient bias. For example, as shown in Figure 6, an embodiment of the invention has no springs between the ring 50 and the base 51. Instead, controlled tolerances allow the ring to reciprocate, as required, without binding. In this embodiment, the return spring in the body of the electrical switch 52 is adequate to support the weight of the ring 50 (and the seal 53) so as to prevent inadvertent activation of the switch 52 by the ring 50. The example Fig. 6 also demonstrates that in another modification of the invention, the jug may be oriented at an infinite number of radial positions relative to the housing. Reference to Figs. 1 and 5 illustrate that the eight scallops 16, 17 limit the jug to eight different radial orientations. By eliminating the scallops and providing a smooth exterior 54 to the base 51 and a smooth interior to the seat, the jug may be located with the handle pointing in any direction. To prevent the base from spinning in the seat, a circumferential polymer grip ring 55 may be located around the base. In another embodiment a polymer grip ring 56 may be located under the shoulder 57 that surrounds the top of the base. In yet another embodiment, the tapering sides of the base and seat can be made to interfere slightly to create controlled friction between the base and seat. In order to ensure that the lower lip 58 of the ring 50 can enter the slot 59 in the switch 52, the lip 58 is made (in this example) continuous and uninterrupted. Accordingly, the cylindrical or other guides 60 are positioned radially inward (as shown) or outboard of the lip 58. Note that in prior art devices, the bias exerted by the return spring in the safety switch 40, 52 had to be carefully determined and controlled. If the spring force 5 was too weak, the switch may have been depressed inadvertently or by a seal (such as 19, 53). If the spring force was excessive, the spring might actually lift a light plastic jug off the seat and destabilise it. In the present invention, the spring force of the return spring in the switch 40, 52 is practically irrelevant, particularly where the springs 30 are used in the ring 27. These springs 30 may be made stiffer than in prior art devices because the jug does not rest on them. Instead these springs are compressed by screwing the jug into the base. Design details disclosed here should be considered as examples and not as limitations to the scope of the invention. 6

Claims (15)

1. A motorised food preparation appliance having a safety interlock, comprising: a motor housing having a seat for receiving a base of a container; the seat having on it a safety switch that can control power to the motor; the base having a floor in which is formed at least one through opening; a ring being located below the floor and having a finger corresponding to each opening, each finger extending through the one or more openings; the ring having a portion that when the housing and base are properly assembled, makes contact with the switch, allowing power to be transmitted to the motor.

2. The food preparation appliance of claim 1, further comprising: a ring seal located in the base and above the one or more openings.

3. The food preparation appliance of claim 1, further comprising: one or more additional safety switches, located on the seat, each one requiring activation by a portion of the ring in order that power be supplied to the motor.

4. The food preparation appliance of claim 1, wherein: the openings are two or more in number and equally spaced from one another.

5. The food preparation appliance of claim 1, wherein: the ring is retained on the base by springs that urge the ring toward the floor.

6. The food preparation appliance of claim 5, wherein: 7 each spring is located adjacent to a finger.

7. The food preparation appliance of claim 5, wherein: the springs and fingers are equal in number.

8. The food preparation appliance of claim 1, wherein: the safety switch has an opening into which fits a portion of the ring.

9. The food preparation appliance of claim 1, wherein: the ring further comprises a lip that cooperates to depress the safety switch.

10. The food preparation appliance of claim 1, wherein: the base and seat are coupled together by cooperating scallops that orient the base with respect to the housing.

11. The food preparation appliance of claim 1, wherein: each finger is flattened and each opening is a cooperating slot.

12. The food preparation appliance of claim 1, wherein: each opening is located between adjacent scallops.

13. The food preparation appliance of claim 1, wherein: the safety switch further comprises an opening that will not admit a human finger but that will admit the portion of the ring. 8

14. The food preparation appliance of claim 1, wherein: an exterior surface of the base carries a polymeric grip ring that acts against the seat to prevent rotation of the base.

15. The food preparation appliance of claim 1, wherein: the appliance is a blender having a jug that fits into the base, the jug impinging on each finger when correctly assembled with respect to the base. 9