US3691329A

US3691329A - Control switch for microwave oven

Info

Publication number: US3691329A
Application number: US186332A
Authority: US
Inventors: Wesley L Ball
Original assignee: Appliance Manufacturing Co Inc
Current assignee: Appliance Manufacturing Co Inc; Raytheon Technologies Corp
Priority date: 1971-10-04
Filing date: 1971-10-04
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12
Also published as: CA928750A; GB1348854A; JPS5326309B2; IT958426B; FR2156541A1; JPS4844773A; SE369455B; DE2239705A1

Abstract

The switch structure disclosed coordinates the position of two plunger members, one manually actuated and one engaged by an oven door, so that a switch operated member is incrementally moved into switch-closing position by sequential depression of the two plunger members. Both plunger members must be actuated before the switch member can reach its switch closing position.

Description

United States Patent Ball.

[54] CONTROL SWITCH FOR MICROWAVE OVEN [72] Inventor: Wesley L. Ball, Marion, Ind.

, [73] Assignee: Appliance Manufacturing Company,

Inc., Van Buren, Ind.

[22] Filed: Oct. 4, 1971 [211 App]. No.: 186,332

[52] US. Cl. ..200/50 A, 219/1055 [51] ..H01h 9/22 [58] Field of Search ..200/50 A, 50 C, 61.62;

[56] References Cited UNITED STATES PATENTS 3,504,144 3/1970 Horner ..200/61.62

[ 51 Sept. 12,1972

3,560,677 2/1971 Mequon ..200/50 C Primary Examiner-Robert K. Schaefer Assistant Examiner-M. Ginsburg Attorney-Maurice A. Weikart [5 7] ABSTRACT The switch structure disclosed coordinates the position of two plunger members, one manually actuated and one engaged by an oven door, so that a switch operated member is incrementally moved into switchclosing position by sequential depression of the two plunger members. Both plunger members must be actuated before the switch member can reach its switch closing position.

7 Claims, 7 Drawing Figures P'ATENTEDSEP 12 I972 sum 1 or 2 INVENTOR WESLEY L. BALL ATTORNEYS PATENTEDSEP 12 1912 3.691, 329

SHEET20F2 Fig FigT.

INVENTOR WESLEY L. BALL m 2 KM n mimhauHiWBn ATTORNEYS 1 CONTROL SWITCH FOR MICROWAVE OVEN BACKGROUND OF THE INVENTION Microwave ovens have come into increasing use, and such ovens, particularly domestic microwave ovens used for rapid cooking of food, have an imperative requirement that access to the interior of the oven can only be had when the microwave generating element is deenergized. Provision of a push-button on-off switch controlling the element is, along, not sufficient. Use of v an oven door actuated switch, uncoordinated with any other control, is also insufficient in itself to remedy the safety hazard inherent in utilization of microwave ovens. A relatively simple, fail-safe control which coordinates the position of the oven door with a manually operable member to assure that oven interior access is denied unless the microwave generating element is deenergized is, therefore, a necessary component of a safe, commercially successful microwave food cooking oven.

The concept of the present invention provides a control switch assembly fulfilling these requirements in which the opening and closing of the microwave element controlling switch is not dependent upon spring loading but is, instead positively and mechanically actuated by motion of a pair of plunger elements, moved in proper sequence by a manual push-button and by the oven door.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a switch assembly embodying the present invention, with portions of the housing broken away.

FIG. 2 is a sectional side view taken generally along the line 2-2 of FIG. 1.

FIG. 3 is a front view of the switch assembly shown in FIGS. 1 and 2.

FIG. 4 is a top plan view of the door actuated component of the switch assembly.

FIG. 5 is a side sectional view, similar to FIG. 2 but taken generally at the centerline (parallel with and viewing in the same direction as line 2-2 of FIG. 1) and showing the switch assembly in the position assumed when the oven door is closed but prior to actuation of the manual control.

FIG. 6 is a view similar to FIG. 5 but showing the switch assembly in the position assumed when the oven door has been closed and the manual control has been actuated.

FIG. 7 is a side sectional view of a modified form of the switch structure shown in FIGS. 1-6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring initially to FIGS. 1 and 2, the switch assembly embodying the present invention includes a housing having a top wall 10, a front wall 11, a rear wall 12, sidewalls l3 and 14 and a base 16 (FIG. 2). Mounted on the exterior face of the top wall is a solenoid 17 whose plunger is rigidly secured to a member 18 (FIG. 2) which extends within the housing and is moved upwardly by the solenoid plunger when the solenoid is energized for a purpose to be subsequently explained.

Mounted on

terminals

19 and 21 which extend into the interior of the housing are fixed or stationary

electrical contacts

19a and 21a. A movable contact member 22, carrying movable

electrical contacts

23 and 24 is positioned adjacent opposite the fixed contacts, the

contacts

23 and 24 being adapted to engage and thus electrically bridge the

fixed contacts

19a and 21a when the movable contact member 22 is placed in closed position. The bridging of

contacts

19a and 21a closes the electrical circuit between the

terminals

19 and 21 and, it will be understood, controls the energized and deenergized condition of the microwave radiating element (not shown) which is operated by the circuit through

terminals

19 and 21.

As may best be seen in FIG. 2, the contact carrying member 22 is resiliently supported, by means of spring 26, on an electrically non-conducting plunger-bridging member 27, the member 27 having a centrally extending portion 27a against which the spring 26 bottoms. The ends of the member 27 are rounded, as indicated in FIG. 2, and extend into apertures in spaced plunger members, identified at 28 (FIG. 5) and 29 (FIG. 2), the member 27 thus extending between the

plunger members

28 and 29 and being pivotally attached thereto. As will be evident from FIG. 1 and 5, a sidewardly extending portion 280 of the plunger member 28 carries the aperture through which the rounded upper end of the member 27 extends. As will be evident from FIG. 4, the aperture 29b, into which lower rounded end of the member 27 extends, is carried by an auxiliary leg 29a which is integral with and extends parallel to the main body of the plunger 29. As will be evident from FIGS. 1

and 2, an additional plunger member 31, acting as a stop plunger extends across the housing and is parallel with and aligned with the plunger 28. The stop plunger 31, although extending parallel to plunger 28, is laterally spaced from it and is not connected to the plunger bridging member 27.

- All three of the

plunger members

28, 29 and 31 are supported in the housing so as to permit limited axial motion of the plungers. Compression spring 32 carried on the plunger 29, compression spring 33 carried on the plunger 31, and compression spring 34 (FIG. 5), carried on the plunger 28, serve as resilient means biasing or urging the respective plungers to the limit of their leftward (as viewed in the drawings) position in the housing.

As many best be seen in FIGS. 1 and 3, the

plungers

28 and 31 are additionally bridged, exteriorly of the housing, by an interlock means taking the form of a member 36 whose ends extend freely through apertures in the portions of the

plungers

28 and 31 just exterior of the housing front wall 11. The member 36 extends into a slot 38 in the wall 11, and as may best be seen in FIG. 3, the slot 38 is discontinuous and the portion 39 of the wall 11 provides a-bearing against which the central portion of the member 36 bears to provide a central fulcrum for the member 36 permitting it to move angularly as one or the other of the

plungers

28 or 31 is manually actuated, the interlock assuring that both plungers cannot be in depressed, or actuated position simultaneously. It will be understood that the outer ends of the

plungers

28 and 31 both carry push-buttons, these push-buttons being shown in phantom lines in FIGS. 2, 5 and 6, together with surrounding portions of the oven control panel and wall, none of which form specific elements of the present invention.

As will be evident particularly from FIGS. 2, 5 and 6, the door engaged plunger member 29, capable of axial movement within the housing, is also mounted for controlled pivotal motion, the pivotal motion occurring generally about the junction of the member 29 with the housing rear wall 12 as a fulcrum. As may best be seen in FIG. 4, the member 29 is apertured as indicated at 290 for accommodating the tip 41a (FIG. 2) of a retaining member 41 whose function and configuration will be subsequently described. Referring again to FIG. 4, a generally U-shaped cut-out portion in the member 29 defines an upturned tongue or abutment 29d which, as may be seen in FIG. 2, is adapted to be engaged by a latch member 42 carried by the oven door 43, engagement of the door abutment 42 with the portion 29d of the plunger occurring as the door is moved into closed position. As may best be seen in FIGS. 2 and 4, a portion of the member 29, identified as 29c, is bent upwardly and this upwardly bent portion is provided with sidewardly extending tabs 29f and a downwardly turned latch or hook portion identified at 29g.

As will be evident from FIGS. 2 and 3, the front wall 11 of the housing is provided with a generally rectangular aperture 44, the portions of the housing wall removed to provide the aperture being bent rearwardly to the interior of the housing to form inwardly extending, rectangular flanges 46. These flanges are provided with diagonally directed, or inclined slots 47 which accommodate the tabs 29f on the plunger 29 and along which the tabs ride as the plunger is moved axially within the housing thus providing the controlled pivotal movement of the plunger 29 previously referred to.

A comparison of FIGS. 2 and 5 will make evident that the retaining member 41, previously mentioned, extends generally vertically within the housing and is composed of a transverse portion 41f which extends between two identical, rearwardly extending, triangularly-shaped flanges 41b and 41c. The reduced ends of the flanges extend through slots in the top wall as will be evident from FIG. 1. Inside the housing, the reduced upper ends of the flanges 41b and 41c accommodate compression springs 41d (FIG. 2) and 41e (FIG. 5) which serve to resiliently bias or urge the retaining member 41 generally, axially downward in the housing. The tip portion 41a of the member 41 is of reduced width and, as mentioned with reference to FIG. 4, extends into the aperture 29c in the member 29. As will be evident from FIGS. 2 and 5, the lower housing wall 16 is provided with a tab 51 which is struck from the housing wall and acts as a locking abutment and is adapted to engage the extending tip 41a of the member 41 during operation of the switch structure as will subsequently be described. As may best be seen in FIGS. 5 and 6, the member 41 is further provided with an additional transverse bar 52 which is adapted to be engaged by the notch 28b and the inclined surface 28con the upper margin of plunger 28. As may best be seen in FIG. 2, the transverse bar 52 is also adapted to be engaged by the member 18 moved by the plunger of the solenoid 17.

In operation, referring initially to FIG. 2, the switch assembly is shown in the position assumed by the plungers when the oven door 43 is open and neither of the manually actuated

plunger members

28 and 31 are depressed or actuated. Under these conditions and the contacts 23-24 are separated from the contacts 19a21 so that the electrical circuit between the terminals l9 and 21 is open. The portion 29e of the plunger 29 is in the upward extreme of the pivotal movement of the member 29 and the plunger is in its extreme leftward position because of the force exerted by the compression spring 32. The

plungers

28 and 31 are also in their extreme leftward position, the retaining member 41 is also in its upper position, being held there by its engagement with the member 29, the springs 41d and 41e being compressed. The member 18 operated by the solenoid 17, although in engagement with the bar 52 of the member 41, exerts no upward force on it since solenoid 17 is deenergized. The inclined surface 31a (FIG. 2) on the upper margin of the plunger 31 is out of engagement with the transverse bar portion 52 of the member 41 and the inclined surface 28c and notch 28b (FIG. 5) on the upper margin of the plunger 28 are also separated from the transverse portion 52 of the member 41. Referring to FIG. 5, when the oven door 43 is closed as there indicated, the portion 42 of the oven door engages the portion 29d of the plunger 29 and moves it axially rightwardly as viewed in FIG. 5 compressing somewhat the spring 32. This rightward motion of the plunger 29 cocks or tilts the member 27 to its position of FIG. 5 thereby moving the

contacts

23 and 24 incrementally toward the fixed contact and 21a, respectively. This rightward motion of the plunger 29 further causes the tabs 29f to ride downwardly within the slots 47 to thereby pivotally move the member 29 downwardly so that the extending end 29g of the member closes over the portion 42 of the door to latch the door to closed position.As this rightward motion of the member 29 takes place, the springs 41d and 41e will cause the lower end of the member 41 to follow the member 29 thereby lowering the member 41 within the housing until the transverse portion 52 engages the upper edge of the plunger 28, the position shown in FIG. 5. It will be noted from FIG. 5 that with the door closed, but prior to the depression of the plunger 28 manually the switch contacts 19a-21 remain open, that is, unbridged by contacts 23-24.

Referring to FIG. 6, the switch components are shown in the position assumed when the plunger 28 is depressed manually, by means of its push-button, with the oven door 43 closed. Under these conditions, the rightward movement of the plunger 28 will move the upper end of the member 27 to its position of FIG. 6, thereby providing the final increment of motion for the member 27 necessary to move the contacts into closed position and completing the electrical circuit between the

terminals

21 and 19 permitting the microwave element to be energized. This rightward movement of the plunger 28 permits the transverse portion 52 of the member 41 to move along the inclined surface 280 of the member 28 and into the notch 28b as shown in FIG. 6. The resulting slight downward motion of the member 41, under the bias of springs 41d and 4'le, causes the tip portion 41a of the member 41 to engage the end of and be positively locked by, the locking abutment 51. Under these conditions the oven door 43 is locked closed, the plunger 28 is held in its rightward position so that the contacts are held closed, and operation of the oven may proceed. It should be noted that the incremental movement of the member 27 into contactsclosing position, shown in FIG. 6, occurs because of the sequential, mechanically produced rightward motion of the plunger 29 and the plunger 28 and this closing motion is not dependent of spring action. The locking abutment 51 provides a rigid mechanical lock preventing leftward motion of the plunger 29 thereby preventing a forced opening of the oven door 43 as long as member 41 is in its position of FIG. 6.

Except as a result of energization of'solenoids 17, to be subsequently described, the oven door cannot be reopened unless the stop plunger 31 (FIG. 2) is depressed, that is, moved axially rightwardly by manually actuating its push-button. When this occurs, the inclined surface 31a (FIG. 2) on the plunger 31 engages the underside of the transverse portion 52 of the member 41 and cams it upwardly. Simultaneously, the

interlock member 36 (FIGS. 1 and 2) is angularly moved counterclockwise (as viewed in FIG. 1) to force the plunger 28 outwardly into its de-actuted position, the transverse portion 52 having been lifted out of the notch 28b by the caming action of the inclined surface 31a on the plunger 31. This lifting of the member 41 also withdraws the tip 41a from engagement with the locking abutment 51 so that the door 43 can then be opened. This motion of the

plunger

28 and 29 also, of course, disengages the switching contacts and the switch components assume their positions of FIG. 2.

It will be understood that the above described procedure for opening the oven door and deenergizing the radiating element may be utilized whenever the oven door has been closed. However, in the normal course of events, during a normal baking cycle, for example, the time during which the oven is to be energized will be controlled by a timer (not shown) which at the end of the selected time period will provide an electrical impulse momentarily energizing the solenoid 17 indicating the end of the cooking period. When the solenoid 17 is momentarily energized, it plunger will raise the member 18 (FIG. 2) applying a lifting force to the underside of the transverse portion 52 of the member 41. This results in an upward motion of the member 41, lifting the member 52 out of the notch 28b in the plunger 28, and permitting the spring 34 to drive the plunger 28 leftwardly (as viewed in FIG. 5) to thereby open the switch contacts and release the oven door for opening as previously described.

A modified and simplified version of the switch assembly is illustrated in FIG. 7. As there shown, a start plunger 61 (comparable to plunger 28) extends across the housing 62. A stop plunger (comparable to plunger 31) also extends across the housing adjacent the plunger 61 but is not shown in FIG. 7. This stop plunger is interlocked with the start plunger 61 by means of the interlock member 63 (comparable to the interlock member 36). The stop plunger (not shown) has no function other than to provide a means for driving the start plunger leftwardly or outwardly (as viewed in FIG. 7) when the stop plunger is actuated, and to raise the member 71. Extending between the plunger 61 and a door plunger 64 is a plunger bridging member 66 (comparable to the member 27 previously mentioned) which carries movable contacts 67 adapted to engage fixed contacts 68. The door plunger 64, at its end 64a, exterior of the housing, is adapted to be engaged by the oven door as it is closed the plunger 64 being thereby depressed or moved rightwardly, as viewed in FIG. 7, this movement of the plunger 64 being resisted by the compression spring 69. A retaining member 71 extends generally vertically within the housing and is comparable to the retaining member 41 in the structure of FIGS. 1-6. The member 71 is provided with a tab or abutment 71a which is adapted to ride the inclined surface 61a on the plunger 61 and to drop into the notch 61b on the plunger 61 when these elements are in appropriate position. A central shoulder 71b on the member 71 rests against the upper margin of the plunger 64, the inclined or ramp surfaces 64b and 64c on the upper margin of the plunger 64 being adapted to be engaged by the shoulder 71b under various operating conditions of the assembly. A compression spring 72 functions to bias or urge the member 71 downwardly, as viewed in FIG. 7. A compression spring functions to bias the plunger 61 outwardly or leftwardly, as viewed in FIG. 7.

In operation, with the switch assembly components in their positions of FIG. 7, the

switch contacts

67 and 68 are open. When the oven door is closed, as the door engages the tip 640 of the plunger 64, the plunger will be moved rightwardly, as viewed in FIG. 7, and this incrementally moves the contacts 67 toward the contacts 68 but such motion, alone, is not enough to close the contacts. The shoulder 71b on the member 71 rides down the ramp 64b and the spring 72 moves the abutments 71a on the member 71 down into engagement with the inclined surface 61a on the plunger 61. With the oven door closed and the contacts 67 moved partially toward closed position, the push-button tip of the plunger 61 maybe manually actuated, compressing the spring 70 and moving the notch 61b beneath the abutment 71a lowering the member 71 into the notch. With this rightward movement of the plunger 61 the final increment of motion of the contacts 67, necessary to close them against contacts 68, will be imparted to the member 66 and the circuit through the switch assembly will be closed to energize the microwave radiating element (not shown).

After the switch contacts have been closed, they may be reopened either by opening the oven door, releasing the plunger member 64, or by depressing the stop button to lift member 71 and angularly move the interlock member 63 to thereby drive the plunger 61 leftwardly, as viewed in FIG. 7, into its de-actuated position. If the contacts are opened by the opening of the oven door, it will be evident that the leftward movement of the plunger 64 will cause the ramp 64b to lift, or move upwardly, the member 71 releasing the plunger 61 to move to its leftward, de-actuated position. The leftward movement of the plunger 64 and of the plunger 61 will, of course, place the member 66 in its position of FIG. 7 in which the

contacts

67 and 68 are opened. When the stop button is pushed while leaving the oven door closed the leftward movement of the member 61 will cause the

contacts

67 and 68 to open. The rightward movement of the stop plunger (not shown) causes an inclined portion of that plunger to engage the abutment 71a on the member 71 to lift member 71 permitting release of the member 61 for its movement leftwardly.

From the foregoing it should be noted that in the switch assemblies described, depressing or actuating either the start plunger or the oven door engaged plunger will not alone be sufficient to close the switch contacts. Closure of the switch contacts requires that both plungers be actuated and the door engaged plunger must be depressed or actuated first otherwise the start plunger will not be held in its actuated position but will return to de-actuated position when finger prcssurcunlncslannullonlsmleaiefl.lnmeilruelure described with reference to FIG. 7,.the oven door is not latched closed but may be opened, however, this opening of the oven door will open the switch contacts. In the structure described with reference to FIGS. l6 the oven door 43 is latched closed and cannot be opened until the stop button is depressed or until the solenoid 17 is momentarily energized. In the opening of the contacts, either by means of the door plunger 29 or the start plunger 28, the opening movement is mechanically produced so that the movable and fixed contacts are mechanically opened and the opening force on the contacts is not dependent on return spring bias which might fail to open the contacts should they be welded or otherwise abnormally stick closed. The positive lock provided by the abutment 51 serves to protect against forcing the oven door open and the control insures that access to the oven interior cannot be obtained without following the sequential control operation insuring that the switch contacts are in open position. The principal of the invention has been illustrated and explained herein with respect to what is presently considered to represent its best embodiments.

Iclaim:

1. A switch assembly, adapted for use with microwave ovens, which coordinates the position of an oven door with the closed and open position of a switching element, said assembly including a housing, a pair of stationary contacts mounted within said housing and a moveable contact member adapted to engage and electrically bridge said stationary contacts when moved to a first position and to disengage said stationary contacts when moved to a second position, a pair of spaced plunger members mounted for movement within said housing and having portions extending externally of the housing, a plunger-bridging member extending between said plungers and pivotally attached thereto, said bridging member carrying said moveable contact member intermediate its ends, whereby when said extending portions of the plungers are successively depressed said moveable contact member is incrementally moved from its said second position to an intermediate position then to its said first position to bridge said stationary contacts.

2. A switch assembly as claimed in claim 1 in which one of said extending plunger portions is adapted to be engaged and thereby depressed by an oven door as it is closed and the extending portion of the other plunger is adapted to be manually depressed.

3. A switch assembly as claimed in claim 2 having resilient means urging both of said plungers out of depressed position, and further including a retaining member supported for movement within said housing and having spaced surfaces engaging said plunger members, the retaining member surface engaging said ."lllllllllllllltll lllttll l er in positlon w en said retaining member is in a first position, the distance between said plunger engaging surfaces being such that said retaining member can occupy its said first position only when said door engaged plunger portion is depressed.

4. A switch assembly as claimed in claim 3 having an additional manually actuated plunger member mounted adjacent to said manually depressable plunger and having a surface engageable with said retaining member when said additional plunger member is manually actuated to move said retaining member out of its said first position independently of the position of said oven door, and interlock means between said manually depressable plunger and said additional plunger to assure that both cannot be simultaneously actuated.

5. A switch assembly as claimed in claim 3 having a solenoid mounted adjacent said retaining member, a member moved by energization of said solenoid and engaging said retaining member to move it out of its said first position thereby releasing said manually depressable plunger form its depressed position.

6. A switch assembly as claimed in claim 3 in which said door engaged plunger is supported for controlled pivotal motion, said door engaged plunger being provided with a door-latching abutment adapted to retain the oven door in closed position while said plunger is at one extreme of its said pivotal motion and to release the oven door when at the other pivotal motion extreme, said retaining member preventing movement of said door engaged plunger to said other pivotal motion extreme when said retaining member is in its said first position.

7. A switch assembly as claimed in claim 6 in which a locking abutment is carried by said housing, and said retaining member is placed in engagement with said locking abutment when both said door engaged plunger and said manually depressable plunger are in depressed position, engagement of said retaining member with said locking abutment providing a positive lock to prevent release of the oven door by said door latching abutment until said retaining member is moved out of its said first position.

Claims

3. A switch assembly as claimed in claim 2 having resilient means urging both of said plungers out of depressed position, and further including a retaining member supported for movement within said housing and having spaced surfaces engaging said plunger members, the retaining member surface engaging said manually actuated plunger member being adapted to retain said plunger member in depressed position when said retaining member is in a first position, the distance between said plunger engaging surfaces being such that said retaining member can occupy its said first position only when said door engaged plunger portion is depressed.