GB2143993A - Electrical appliance interlock switch - Google Patents

Abstract

An interlock switch (20) for an electrical appliance such as a microwave oven has a housing (22) having an interior front wall (34), and a plurality of conductive switch elements (100 - 109). A pair of barriers (64, 70) define a pair of gaps (75, 77) with the interior front wall (34) for mounting a buss (90), comprising a first segment (94), formed integrally with one of the conductive switch elements (102), and a second segment (92), formed integrally with another one of the conductive switch elements (106) and electrically connected to the first segment (94). The barriers (70, 64) and a further barrier (60) provide isolation between selected switch elements so that broken off pieces from some switch elements will not come in contact with other switch elements. The barrier (70) is stationary and the barriers (60, 64) are mounted on a pivotable switch element actuator (54). <IMAGE>

Description

SPECIFICATION Electrical appliance interlock switch with improved isolation means and buss BACKGROUND OF THE INVENTION This invention relates generally to electrical appliances and specifically to microwave ovens which have a frame defining a cooking chamber, and a door hingedly mounted to the frame. More particularly, this invention relates to such appliances which utilize an interlock switch, mounted in the door jamb, actuated by probe means extending from the door in alignment with the door jamb. The interlock switch permits the oven to be operated only when the oven door is fully closed and latched, thereby providing a highly desirable safety feature.

Interlock switches used for this purpose typically comprise two electrically coupled switches, both of which must be actuated in order for operating power to be passed to the oven. The value of such an interlock switch is, of course, reduced if one of the two electrically coupled switches becomes welded closed due to tampering, equipment malfunction or some spurious condition. If this occurs, actuation of the unaffected switch will be the only action necessary to allow operating power to be passed to the oven. This, of course, would defeat many of the safety benefits associated with a conventional interlock switch.

SUMMARY OF THE INVENTION The present invention contemplates an improved interlock switch for use with an electrical appliance such as a microwave oven. The appliance comprises a frame defining a door jamb, a door mounted to the frame, and a probe mounted to the door in alignment with the door jamb.

The invention further includes an interlock switch having a housing mounted to the door jamb and actuator means mounted to the housing, the actuator means being operable by the probe. The switch housing has an inside front wall and three groups of conductive switch elements, most of which are mounted along that wall in cantilever arrangement. Also mounted in the housing are a stationary barrier and first and second movable barriers. The stationary barrier is disposed between the first and second groups of conductive switch elements and the first movable barrier is disposed substantially linearly with the stationary barrier. The second movable barrier is located between the second and third groups of conductive elements. The first and second movable barriers are movable from a first position to a second position upon operation of the actuator means by the probe.

The stationary and first movable barriers isolate the first and second conductive switch elements and the second movable barrier iso lates the second and third conductive switch elements so that broken off pieces from one of the conductive switch elements cannot come in contact with the other of the ccnductive switch elements even when the movable barriers are moved from their first position to their second position. The stationary barrier has a portion displaced from the front wall defining a first gap therewith, and the second movable barrier has a portion displaced from the front wall defining a second gap therewith disposed within the first gap and the second gap interconnects one of the conductive switch elements in the first group with one of the conductive switch elements in the third group.Because the buss is substantially captivated within the gaps defined by the front wall and the stationary and the second movable barriers, the likelihood of it interfering with the operation of the switch elements even if it becomes broken off is greatly mini mized.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiment of the invention summarized above is shown in the accompanying drawings wherein: FIGURE 1 is a schematic, perspective view of an electrical appliance incorporating the invention; FIGURE 2 is a schematic, plan view of the interlock switch used with the appliance shown in FIG. 1; FIGURE 3 is a schematic, plan view of the interlock switch shown in FIG. 2 in a partially actuated condition; FIGURE 4 is a schematic, plan view of the interlock switch shown in FIG. 2 in a fully actuated condition; FIGURE 5 is an enlarged, schematic, perspective of a portion of the appliance and the interlock switch shown in FIG. 1; and FIGURE 6 is an enlarged, schematic, perspective view of the portion of the interlock switch shown in FIG. 5, but in an actuated condition.

DETAILED DESCRIPTION OF THE PRE FERRED EMBODIMENT OF THE INVENTION Referring now to Figure 1 there is illustrated a preferred embodiment of the invention. In particular, there is illustrated an electrical appliance, such as a microwave oven 10, having a frame 1 2 defining a chamber 11 into which food to be heated by oven 10 is placed. Frame 1 2 further includes a door jamb 1 3 into which is mounted an interlock switch 20.

Oven 10 further includes an oven door 1 5 which is typically hingebly mounted to frame 1 2. Near the free end of oven door 1 5 there is mounted probe means 16, preferably in the form of a rigid pin member 1 7 and a movable latch pawl 1 8. Pin member 1 7 and latch pawl 1 8 are preferably aligned with door jamb 1 3, and in particular are aligned, respectively, with a first actuator 40 and a second actuator 50 associated with interlock switch 20.As explained in greater detail hereinafter, pin member 1 7 operates first actuator 40 as oven door 1 5 becomes partially closed, and latch pawl 1 8 operates second actuator 50, when oven door 1 5 is fully closed and latched.

The operation of probe means 1 6 in the form of pin member 1 7 and latch pawl 1 8 are shown best by referring to Figures 5 and 6.

As oven door 1 5 closes, rigid pin member 1 7 abuts a contact face 42 of first actuator 40, thereby moving a slider 44 horizontally (see horizontal arrow in Figure 6) against a coil spring 46. The movement of slider 44 causes actuation of several switch elements associated with interlock switch 20 in a manner explained in greater detail hereinafter.

Similarly, latch pawl 1 8 operates second actuator 50 when oven door 1 5 is fully closed and latched. Thus, still referring to Figures 5 and 6, interlock switch 20 comprises a housing 22 having a rear wall 24. Rear wall 24 defines a notch 36 and a latch 39 extending therein. Latch 39 has an angled face 37 and a horizontal face 38 adapted to be sequentially contacted by a latch surface 1 9 of latch pawl 1 8. When latch pawl 18 begins to advance into notch 36 in side wall 24, during the closure of oven door 1 5, latch surface 1 9 is urged downwardly by angled face 37 of latch 39.As latch pawl 18 advances further into notch 36, latch surface 1 9 slides along horizontal face 38 of latch 39 until face 38 is aligned with a cutout 31 defined in latch pawl 18. When this occurs, latch pawl 18 springs upwardly (see vertical arrow in Figure 6), whereby oven door 1 5 is fully closed and latch pawl 18 becomes latched with latch 39.

As shown in Figures 5 and 6, in this prefferred embodiment, probes 16,17 operate actuators 40,50 without actually entering the interior of housing 22 of interlock switch 20.

Indeed, throughout the entire operation of switch 20, actuators 40,50 isolate the outside environment of switch 20 from the interior of housing 22. As a result, door probe wear particles and other spurious material cannot readily enter housing 22 and perhaps interfere with the operation of the various components therein. Further, this arrangement greatly minimizes the likelihood that access to the interior of housing 22 can be gained via an external implement (such as a knife or screwdriver) through tampering, carelessness or accident.

Operation of actuator 50 by the latching of latch pawl 18 to latch 39 causes actuator 50 to move from the position shown in Figure 5, to the position shown in Figure 6. This, in turn, causes actuation of several switch elements associated with interlock switch 20 in a manner explained in greater detail hereinafter.

From the foregoing description, however, it should be clear that the sequence of movement of actuators 40 and 50 is such that first actuator 40 is operated by rigid pin member 1 7 before oven door 1 5 is fully closed, but second actuator 50 is not operated by latch pawl 1 8 until oven door 1 5 is fully closed and latched.

The specific components of interlock switch 20 and their operational sequence in response to the movement of actuators 40 and 50 is illustrated in Figures 2-4. In particular, Figure 2 illustrates the position of the switch elements comprising interlock switch 20 when oven door 1 5 is open, Figure 3 illustrates the position of those switch elements when oven door 1 5 is partially closed, and Figure 4 illustrates the position of those switch elements when oven door 1 5 is fully closed and latched.

Referring now to Figure 2, housing 22 of interlock switch 20 is shown to include, in addition to rear wall 24, a pair of side walls 26, 28 a bottom wall 25, and a plurality of anchoring fixtures 32 defining an interior front wall 34. Extending outwardly from side walls 26, 28 are a pair of mounting ears 29 which are used to facilitate the mounting of interlock switch 20 in door jamb 1 3 of oven 1 0.

Interlock switch 20 further includes a stationary barrier 70 which preferably comprises a rigid member extending upwardly from base 25 near the center of housing 22. Pivotally mounted to base 25 of housing 22 is a platform 54 having a movable barrier 60 extending upwardly therefrom along substantially the same line defined by stationary barrier 70 when oven door 1 5 is in the fully closed position of Figure 4. A pair of substantially parallel flange members 67, 68 also extend upwardly from platform 54 intersecting, respectively, the opposite ends of movable barrier 60. Also extending upwardly from platform 54 are three rigid pins 61, 62 and 63 whose function will be explained hereinafter.

An additional movable barrier 64, extending substantially parallel to stationary barrier 70 when oven door 1 5 is in the fully closed position of Figure 4 also extends upwardly from platform 54. Additional barrier 64 terminates in a hub 66 which is mounted over a post 65 extending upwardly from base 25.

Actuator 50 is preferably integrally formed with platform 54 near the end thereof opposite hub 66. Thus, movement of actuator 50, in response to movement of latch pawl 18, causes platform 54 to pivot about post 65.

This movement of platform 54 causes a corresponding movement of pins 61, 62 and 63, movable barrier 60, and additional barrier 64.

Housing 22 further incorporates a slider guide 45 through which slider 44 can be moved back and forth in response to the operation of actuator 40 by rigid pin member 1 7. Extending upwardly from slider 44 is a pair of actuator pins 47, 48, and extending transversely from slider 44 is an actuator arm 49. The functions of actuator pins 47, 48 and actuator arm 49 will be explained hereinafter.

Mounted inside housing 22 of interlock switch 20 are a plurality of electrically conductive switch elements 100-109. Switch elements 100-106 and switch elements 108 109 have, respectively, fixed ends 110-116 and 118-119, substantially captivated between adjacent ones of anchoring fixtures 32, and (except for switch element 108) free ends 120-126 and 128-129.

Interlock switch 22 also includes an electrically conductive switch element 107 which is preferably integrally formed with switch element 108. Thus, in this embodiment, switch element 107 has a free end 1 27 and an interconnected end 11 7 which connects with an interconnected end 1 28 of switch element 108. Each of switch elements 100-109 is preferably mounted edgewise within housing 22 of interlock switch 20, so that they sometimes function as leaf springs, and are formed of electrically conductive material such as copper or the like.

In this preferred embodiment switch elements 100 and 101 form part of a circuit for an auxillary device such as a lamp (not shown), and are normally closed, i.e., in the "make" condition, when oven door 1 5 is in the open position of Figure 2. Thus, the lamp in the circuit comprising switch elements 100 and 101 will be illuminated when oven door 15 is open.

Switch elements 101 and 102 preferably form part of a primary interlock circuit for microwave oven 10, and are normally open, i.e., in the "break" condition when oven door 1 5 is in the open position of Figure 2. Thus, switch elements 101 and 102 prevent operating power from being supplied to microwave oven 10 as long as oven door 1 5 is open, converting to the "make" condition only when the door is fully closed and latched.

Switch elements 103 and 104 preferably form part of a logic circuit (not shown) which, in accordance with well known microwave oven operation, controls many of the oven's operating parameters and sequences. As shown in Figure 2, switch elements 103 and 104 are normally in the "break" condition when oven door 1 5 is open, thereby rendering the logic circuitry inoperative at that time.

Switch elements 105 and 106 comprise the secondary interlock for microwave oven 10. As with the primary interlock defined by switch elements 101 and 102, switch elements 105 and 106 are normally in the "break" condition when oven door 1 5 is open, changing to the ''make" condition only when oven door 1 5 is fully closed and latched.

Switch elements 106 and 107 form part of a monitoring circuit which includes a fuse (not shown), and are normally in the "make" condition when the oven door is open. In accordance with conventional interlock switch operation, if switch elements 1 06 and 107, and switch elements 105 and 106, are ever simultaneously closed, such as if a malfunction causes switch elements 105 and 106 to be welded together, the fuse will blow, thereby preventing operating power from being supplied to oven 10 even if all other conditions for proper oven operation have been satisfied. Switch element 106, sometimes referred to herein as a common switch element, has a monitor side 106a and an interlock side 106b.A part 1 38 of switch element 106 on the monitor side 1 06a is adapted to contact a portion 1 36 of switch element 107 near the free end 1 27 thereof when oven door 1 5 is open. On the other hand, a part 1 32 on the interlock side 1 06b of switch element 106 is adapted to contact a portion 1 34 of switch element 105 when oven door 1 5 is fully closed and latched.

Finally, switch elements 108 and 109, which are normally in the "break" condition when oven door 1 5 is open, form part of a second auxillary circuit which may also include a lamp (not shown). In this preferred embodiment switch elements 108 and 109 are disposed lower in housing 22 than any of the other switch elements 100 through 107.

In particular, switch elements 108 and 109 are located in a plane slightly above base 25 of housing 22, while switch elements 100 through 107 are located in a plane closer to the top of housing 22.

A buss 90, preferably comprised of an integrally formed segment 94 of switch element 102 and an integrally formed segment 92 of switch element 106 serves to electrically interconnect those two switch elements.

For safety purposes, buss 90 is mounted edge-wise in gaps 75 and 77, thereby being substantially captivated between interior front wall 34 on the one hand, and the forward end 72 of stationary barrier 70 and the forward end of movable barrier 64, i.e., hub 66 on the other hand. The segments 92, 94 comprising buss 90 are preferably formed by bending portions of switch elements 102 and 106 until the ends of the bent portions are in facing relationship. These ends of segments 92, 94 are then electrically interconnected in any conventional manner.

Stationary barrier 70 and movable barrier 60, along with portions of rear wall 24, side wall 26 and interior front wall 34, define a first compartment 80 within housing 22 of interlock switch 20. First compartment 80 serves to confine, within that compartment, any pieces of interlock switch 20 which, due to part failure, abuse, or manufacturing error, become broken off and loose inside housing 22. By isolating such broken off pieces in this manner, they cannot accidentally fall into a portion of housing 22 outside the boundaries of first compartment 80 and accidentally short circuit or interfere with other switch elements or components. For the same purpose, stationary barrier 70, movable barrier 60 and additional barrier 64, along with portions of rear wall 24 and interior front wall 34 define a second compartment 85, isolated from other portions of housing 22.Similarly, additional barrier 64, along with portions of rear wall 24, side wall 28 and interior front wall 34 define a third compartment 88, isolated from other portions of housing 22.

The operation of interlock switch 20 can now be explained. When oven door 1 5 is open, the switch elements of interlock switch 20 take the configuration shown in Figure 2.

In this configuration, pin 61 provides a force on switch element 101 substantially in the direction of arrow 140. Similarly, pin 63 provides a force on switch element 105 substantially in the same direction as arrow 1 40.

On the other hand, pin 62 provides a force on switch element 103 in the direction opposite arrow 1 40. Thus, when actuator 50 is operated by latch pawl 1 8 (Figure 6) the force opposing the movement of actuator 50 is substantially reduced. In particular, if the magnitude of the force at each of pins 61, 62 and 63 is substantially equal, the combined force of pins 61, 62 and 63 opposing movement of actuator 50 is approximately one third that which it would be if the forces applied by all three pins 61, 62 and 63 were in the same direction as arrow 140.

As oven door 1 5 begins to close, the operation of rigid pin member 1 7 and actuator 40 takes effect. This, in turn, causes slider 44, and hence actuator pins 47, 48 and actuator arm 49, to move from the positions shown in Figure 2 to the position shown in Figure 3.

Thus, switch elements 108 and 109 move from the "break" to the "make" position, while switch elements 107 and 106 move from the "make" to the "break" position.

Further, switch element 106 moves closer to (but still does not contact) switch element 105.

When oven door 1 5 is fully closed, and latch pawl 1 8 is latched to latch 39 (Figure 6), the switch elements change from the positions shown in Figure 3 to the positions shown in Figure 4. More particularly, switch elements 105 and 106 contact one another.

Switch elements 103 and 104 move from the "break" to the "make" position, switch ele ments 101 and 102 move from the ' "break" to the "make" position, and switch elements 100 and 101 move from the "make" to the "break position.

The interlock switch described herein, when used in connection with an electrical appliance such as microwave oven 10, provides many efficiencies, economies, and safety features. For example, the use of switch element 106 as a cantilevered common switch element adapted to contact switch element 107 on one side of switch element 106 and to contact switch element 105 on the other side of switch element 106, combines the advantages of reliability, efficiency, economy, and compactness in a single switch. Further, the use of stationary and movable barriers of the type described isolates any pieces of interlock switch 20 which, due to part failure. abuse, or manufacturing error, become broken off or loose inside housing 22.As such, these broken off pieces cannot accidentally fall into portions of housing 22 outside the boundaries of the compartments in which they are confined, and accidentally short circuit or interfere with other switch elements or components. Additionally, by captivating buss 90 in gaps 75 and 77, and forming it integrally from portions of switch elements 102 and 106, the chances of buss 90 breaking away and causing electrical or mechanical damage to the other components of interlock switch 20 is greatly reduced.

In view of the foregoing, the above described interlock switch, adapted for use with an electrical appliance such as a microwave oven, has numerous beneffits and advantages not available heretofore. However, several modifications and embodiments of this switch, and its operating environment, which do not part from the true scope of the invention, will become apparent to those skilled in the art.

Accordingly, all such modifications and embodiments are intended to be covered by the appended claims.

Claims (16)

1. An interlock switch for an electrical appliance including frame means defining a door jamb, a door mounted to said frame means, probe means mounted to said door in alignment with said door jamb, and an interlock switch housing mounted to said door jamb, having actuator means, mounted to said housing, operable by said probe means, comprising; a first group of conductive switch elements mounted in said housing for making a first electrical connection; a second group of conductive switch elements mounted in said housing for making a second electrical connection; stationary barrier means, mounted in said housing between said first and second groups of conductive switch elements;; movable barrier means, disposed within said housing substantially colinearly with said stationary barrier means, movable from a first position to a second position upon operation of said actuator means by said probe means; a first compartment defined, at least in part, by portions of said stationary and movable barrier means, said first compartment bounding said first group of conductive switch ele ments; and a second compartment defined, at least in part, by portions of said stationary and movable barrier means, said second compartment bounding said second group of conductive switch elements, whereby said first and second groups of conductive switch elements remain bounded even upon movement of said movable barrier means from said first position to said second position.

2. The interlock switch defined in claim 1 further includes: platform means, movable by said actuator means; and additional barrier means extending upwardly from said platform means to define, at least in part, an additional compartment for additional conductive switch elements.

3. An interlock switch for an electrical appliance including frame means defining a door jamb, a door mounted to said frame means, and an interlock switch housing mounted to said door jamb, comprising; first and second conductive switch elements mounted in said housing; stationary barrier means disposed within said housing between said first and second conductive switch elements; and movable barrier means disposed within said housing between said first and second conductive switch elements, movable from a first position to a second position upon closure of said door; said stationary and movable barrier means defining, at least in part, first and second compartments, when said movable barrier means are in either said first or said second positions, whereby broken off pieces from one of said conductive switch elements cannot come in contact with the other of said conductive switch elements.

4. An interlock switch for an electrical appliance having an interlock switch housing mounted to said appliance comprising; first and second conductive switch elements mounted in said housing; means, including a stationary barrier and a movable barrier, for isolating said first and second conductive switch elements so that broken off pieces from one of said conductive switch elements cannot come in contact with the other of said conductive switch elements; and means for moving said movable barrier while maintaining the isolation between said first and second conductive switch elements.

5. The interlock switch defined in claim 4 further includes: actuator means operable by probe means on said appliance; platform means movable by said actuator means; a third conductive switch element; and additional barrier means, extending upwardly from said platform means for isolating said third conductive switch element from at least one of said first and second conductive switch elements.

6. The interlock switch defined in claim 5 wherein said control housing includes a base, and wherein said platform means is pivotably mounted on said base.

7. An interlock switch, adapted for use with an electrical appliance having probe means, including an interlock switch housing actuator means mounted to said housing operable by said probe means, and first, second and third conductive switch elements mounted in said housing, the improvement comprising: means, including a stationary barrier and a movable barrier for isolating said first and second conductive switch elements so that broken off pieces from one of said conductive switch elements cannot come in contact with the other of said conductive switch elements; and means, responsive to said probe means, for moving said movable barrier while maintaining the isolation between said first and second conductive switch elements; platform means movable by said actuator means; and additional barrier means, extending upwardly from said platform means for isolating said third conductive switch element from at least one of said first and second conductive switch elements.

8. In an interlock switch having a control housing characterized by an interior front wall and three groups of conductive switch elements mounted along said wall, the improvement comprising: a stationary barrier mounted in said housing between a first group and a second group of said conductive switch elements, said stationary barrier having a forward portion displaced from said front wall and defining a first gap therewith; a movable barrier mounted in said housing between said second group and a third group of conductive elements, said movable barrier having a forward portion displaced from said front wall, and defining a second gap therewith; and a buss, disposed within said first gap and said second gap, interconnecting one of said conductive switch elements in said first group and one of said conductive switch elements in said third group.

9. The interlock switch defined in claim 8 wherein said buss is disposed edgewise within said first and second gaps and is captivated therein.

10. The interlock switch defined in claim 8 wherein said buss comprises a first segment formed from one of said conductive switch elements in said first group of conductive switch elements, and a second segment formed from one of said conductive switch elements in said third group of conductive switch elements,

11 The interlock switch defined in claim 10 wherein said first segment and said second segment are electrically connected.

12. The interlock switch defined in claim 10 wherein said first segment is formed integrally with said one of said connecting switch elements in said first group of connecting switch elements, and said second segment is formed integrally with said one of said connecting switch elements in said third group of connecting switch elements.

13. In an interlock switch having a control housing characterized by an interior front wall and three groups of conductive switch elements mounted along said wall, the improvement comprising: first means defining a first gap with said interior front wall; second means defining a second gap with said interior front wall; a buss, disposed within said first gap and said second gap, interconnecting one of said conductive switch elements in one of said groups with one of said conductive switch elements in another one of said third group.

14. The interlock switch defined in claim 1 3 wherein said first means includes barrier means mounted in said housing between a first group and a second group of said conductive switch elements;

1 5. The interlock switch defined in claim 1 3 wherein said second means includes barrier means mounted in said housing between said second group and a third group of said conductive switch elements.

16. In an interlock switch having a control housing characterized by an interior front wall and three groups of conductive switch elements mounted along said wall, the improvement comprising: first means defining a first gap with said interior front wall; second means defining a second gap with said interior front wall; a buss, disposed within said first gap and said second gap, interconnecting one of said conductive switch elements in one of said groups with one of said conductive switch elements in another one of said third group; said buss being formed from a first segment integrally formed from one of the conductive switch elements in said first groups, and a second segment integrally formed from one of the conductive switch elements in said third group.