US 3638638 A
A bimetal-operated locking arrangement for a latched door of a self-cleaning oven which includes a second bimetal means having negative deflection characteristics below a certain temperature cooperating with the main bimetal means to aid the movement of the locking means toward a locked position during a period of oven temperature rise, and to aid the movement of the locking means away from the locked position during the period of falling oven temperatures following a heat cleaning operation.
Claims available in
Description (OCR text may contain errors)
United States Patent Phifer  LATCHING AND LOCKING ARRANGEMENT FOR SELF-CLEANING OVEN DOOR  Inventor: Clarence Gary Phifer, Columbia, SC.
 Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa.
 Filed: May 26, 1970 ] Appl. No.: 40,495
[ Feb. 1, 1972 Primary Examiner-Charles J. Myhre Attorney-F. H. Henson and E. C. Arenz  ABSTRACT A bimetal-operated locking arrangement for a latched door of a self-cleaning oven which includes a second bimetal means having negative deflection characteristics below a certain tem perature cooperating with the main bimetal means to aid the  U S cl 126/197 movement of the locking means toward a locked position dur- 51 I .Cl 15/02 g a period of oven temperature rise and m aid the movc 1 ment of the locking means away from the locked position dur-  Fl? 0 Seareh..... ..l26/197, 273 g the period of falling oven temperatures following a heat cleaning operation.  References Cited 10 Claims, 9 Drawing Figures UNITED STATES PATENTS 3,050,048 8/ 1962 Scott ..l26/273 C L; l I I J l l |l |l ll -7i -J I6 30 26" 28 I I4" I I1 l I l |2- u 24"; H c II: II H CF U PATENTEU FEB H 72 sum 1 or 3 FIG.
a Ffi i FIG. 3
WITNESSES INVENTOR Clarence G. Phifer ATTORNEY PAIENIEII FEB I i972 SHEET 3 OF 3 OVEN TEMP. 550F AND FALLING MAIN BIMETAL 54- 400F LAG COMP-58- 350F TAL 54- 300F FIG. 8
OVEN TEMP-550F AND RISING MAIN BIME LAG COMP FIG. 7
LATCHING AND LOCKING ARRANGEMENT FOR SELF- CLEANING OVEN DOOR CROSS-REFERENCE TO RELATED APPLICATION Holtkamp U.S. Pat. application Ser. No. 40,485 filed May 26, 1970 is a related patent application.
BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to the art of locking self-cleaning oven doors during a cleaning operation.
2. Description of the Prior Art I am not aware of any prior art which I consider to be particularly pertinent to my invention.
In the l-loltkamp patent application referred to above, the form of locking means illustrated and briefly described constitutes one embodiment of my invention. The predecessor to the locking means there shown and described and which was contributed by Holtkamp, basically comprised a pivoted lever having an upper locking portion adapted to be moved into obstructing relation behind the rear end of a drawbar which was operated to a forward position by manual operation of the catching means, and which included a lower end engaged by a main bimetal which deflected in one direction upon a rising oven temperature to move the locking portion of the lever behind the drawbar.
Several difficulties were experienced with the Holtkamp arrangement. It is relatively easy to provide a single main bimetal in the fashion just described which cooperates with a suitable lever mechanism to obtain the movement of the locking portion of the lever mechanism to an obstructing position relative to a drawbar at the temperature in the oven at which the locking is to be effected. However, the locking mechanism is not directly subject to oven temperatures, and only reflects oven temperatures in an analogous way. As a result, the temperature, of the main bimetal, for a given oven temperature during rising oven temperatures, is not the same as, but is rather lower than, the bimetal temperature during falling oven temperatures, because the main bimetal has been heated beyond that temperature capable of causing initial locking during the high oven temperatures existing during the cleaning operation. Additionally, the variable heat loss characteristics of different types of ovens, and even of different ovens of the same type, adds to the problem. As an example, a system using a single main bimetal may lock at, say, 600 F. oven temperature as the oven is being heated into the heat cleaning temperature range, but will not unlock until the oven temperature has dropped to perhaps 300 F. during the cooling period following the heat cleaning cycle. In effect, thermal lag thus experienced adds approximately 1 extra hour to that part of the heat cleaning cycle during which it is required that the door be locked.
Accordingly, one aim of my invention is to substantially reduce or eliminate this temperature differential at which locking and unlocking occur. Additionally, it is contemplated in accordance with my invention that an arrangement be provided in which the bimetals used are inherently protected from overstress in case interference with physical movement with any part of the locking means is encountered. Further, the arrangement provided in accordance with my invention is intended to provide an overstress protection means of a character such that any bimetals used are not subjected to undue bias which would complicate calibration operations.
SUMMARY OF THE INVENTION In carrying out my invention I provide a latching and locking arrangement for the door of a pyrolytic self-cleaning oven of the type heatable to a cooking temperature range and to a higher heat-cleaning temperature range which includes latching means movable between door-latched and door-unlatched positions, locking means movable between a latchlocked and a latch-unlocked position, first means responsive to and reflecting oven temperatures for moving the locking means between the locking means positions, and second means responsive to and reflecting oven temperatures for aiding movement of the locking means toward a latch-locked position as the oven temperature rises to a temperature requiring a door-locked condition, and for aiding movement of the locking means toward the latch-unlocked position as the oven temperature falls through the temperature which permits a door-unlocked condition.
In the preferred form, the second means comprises a bimetal which has negative deflection characteristics at the temperatures experienced by said second bimetal as the oven temperature rises to the temperature requiring a door-locked condition, and which has positive deflection characteristics at temperatures experienced by said second bimetal as the oven temperature falls through the temperature which permits an unlocked oven door. The first means, comprising a first bimetal, is arranged to transfer its moving force to the locking means through stress-resilient means so that overstress of the bimetals is avoided under conditions blocking movement of the locking means between the locking means positions.
DRAWING DESCRIPTION FIG. 1 is a side elevational view of a range having a heat cleaning oven incorporating the invention;
FIG. 2 is a top view of a lockbox and strike plate assembly with the drawbar in a rear, unlatched position;
FIG. 3 is a front elevational view of the assembly of FIG. 2 with the drawbar in a forward, latched position, and the locking means in a position obstructing the return of the drawbar;
FIG. 4 is a fragmentary top view similar to FIG. 2, but with the drawbar in the forward latching position;
FIG. 5 is an isometric view of the currently preferred form of locking means according to the invention;
FIG. 6 is a fragmentary, exploded isometric view illustrating one way in which the coupling and stress-reliefmeans between the two bimetals is arranged.
FIG. 7 is a fragmentary elevational view showing the relationship between the parts of the locking means as it is moving into a locking position;
FIG. 8 is a fragmentary elevational view as in FIG. 7, but showing the relationship of the parts of the locking means as it is moving out of a locking position; and
FIG. 9 is a fragmentary elevational view of another form that the locking means according to the invention may take.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the range 10 includes an interior oven cavity 12 adapted to be closed by the swing-down door 14 which may be manually latched by turning handle 16 in a clockwise direction. By so turning the handle, a projection 18 (not shown in FIG. 1) is turned up out of the top edge of the door to engage with a strike plate 20 located above the top edge of the door in the front nose portion of the surface unit platform 22. One mechanism suitable for carrying out this type of latching operation is described in Nagel U.S. Pat. No. 3,390,909, to which reference should be had for further detail.
The oven cavity 12 contains the usual bake heating element 24, and broil element 26 which preferably is used for providing the heat for the self-cleaning operation in accordance with Kastovich U.S. Pat. application Ser. No. 552,663, now U.S. Pat. No. 3,504,161. The oven also contains temperature sensing means 28 which, through conventional thermostatic means, normally controls energization of whichever heating elements are used for carrying out cooking operations and heat cleaning operations.
The top wall of the oven liner defining the oven cavity 12 is indicated by the numeral 30. A lockbox 32 has its lower portion seated upon the outer face of the wall 30 in limited heatconducting relation and contains the locking means of the invention.
Referring to FIGS. 2 and 3 in particular, the lockbox 32 takes the general form of an open from box provided with a number of horizontal slots 34 in the rear and sidewalls. The horizontal slots provide heat breaks which limit the rate of transfer through the box side and rear walls. The lockbox 32 is supported by being attached directly to the strike plate which, in turn, is secured to the frame of the range in the nose of the platform 22. Downwardly projecting tabs 36 at the lower ends of the sidewalls seat on the top wall 30 of the oven liner to provide single point contact at each side. This single point contact arrangement is for the purpose of providing uniform and predictable heat transfer rates into the lockbox structure from the oven liner of one range as compared to the liner of the next range.
The latch and lock arrangement includes an L-shaped lever 38 pivotally carried on the strike plate and having one leg pivotally attached at its end to drawbar 40. The drawbar is biased to the rear, and the L shaped lever is biased in a clockwise direction (toward the position shown in FIG. 2) by a torsion spring 42 which, because of the hook portion engaging one edge of the front end of drawbar 40, also tends to rotate the drawbar 40 in a counterclockwise direction (i.e., to the left at its rear end).
A slot 44 (FIG. 3) in a bent-up tab portion of the lockbox cooperates with the pivotal connection between the drawbar and the L-lever to impose a translational motion to the drawbar as it is drawn forwardly so that in its forward and latched position (FIG. 4), it is substantially perpendicular to the front edge of the strike plate 20.
When the oven door is to be latched, the latch handle 16 on the oven door is swung downwardly to move the projection 18 up into the strike plate slot into engagement with the one leg of the L-lever 38, which pivots counterclockwise and accordingly draws the drawbar 40 forwardly to a position shown in FIG. 4. While the torsion spring 42 tends to urge the drawbar 40 rearwardly, the weight of the latch handle prevents this from occurring. However, so long as the drawbar is not obstructed in movement in a rearward direction by the locking means generally designated 46, turning of the latch handle back toward an unlatched position releases the one leg of the L-lever which had been engaged by projection 18, and permits the torsion spring 42 to move the drawbar rearwardly to its FIG, 2 position. It is noted that the arrangement ofthe forward end of the drawbar and the L-lever accords in most respects with that of the noted Nagel patent.
The drawbar 40 has a depending portion 48 (FIGS. 24) at its rear end which is used to control switch means in the forward path of movement of the depending portion. As part of my inventive contribution, the angle between the depending portion 48 and the main portion 40 of the drawbar is about 80, and the bend line 50 between these portions forms a slight acute angle, such as 4, relative to a line perpendicular to the longitudinal axis of the main portion of the drawbar. The purpose of this arrangement is to insure that the engagement of the portion of the locking means 46 which contacts or obstructs the return of the drawbar engages only the bend line 50 when such engagement occurs, and that the movement of the locking means from a locked position to an unlocked position is facilitated if the user should have attempted to prematurely unlatch the still-locked oven door, and then have left the door handle in that position at which lock interference was encountered, and the locking means is in the process of moving toward an unlocked position.
The currently preferred form of locking means according to my invention, and its relation to the other parts in the lockbox, may be best understood in connection with FIGS. 3 and 5. Among the parts which cooperate during locking are a base member 52 pivotally carried on a relatively low friction pivot shaft 53 attached to the vertical rear wall of the lockbox, and a main bimetal 54 which has its lower end fixed to the lower wall of the lockbox and its upper end coupled, through a circular spring wire 56, (which serves in part as stress relief means) to the lower end of lag-compensating bimetal 58. This compensating bimetal has its lower end coupled to one end of the spring wire circle, and its upper end rigidly fastened on a right angle tab portion of the base member. The rightangle tab portion has an upward extension 62 which is the part adapted to move into obstructing relationship with the rear end of the drawbar 40.
Referring to FIG. 6, the relationship between the coupled ends of the main bimetal 54 and compensating bimetal 58 with the spring wire circle 56 is illustrated before the assembly of the parts, The lower end of the compensating bimetal is provided with a right angle lug 63 with a threaded hole 64 therein. The ends of the circular spring wire 56 are provided with loops 65 in the plane of the wire. A small, headed screw 66 receives one of the loops 65 on its shank and is screwed into the threaded hole 64. Thus the one end of the wire 56 is held tightly to the lower end of the lag-compensating bimetal, while the inherent bias of the spring wire circle urges the lower end of the lag-compensating bimetal toward the main bimetal upper end because of the engagement of the other loop end 65 of the wire against the one face of the main bimetal. The inter mediate part 67 of the wire circle 56 (FIG. 5) passes through a rectangular aperture 68 in the center part of the lag-compensating bimetal.
The operation of the locking arrangement in accordance with oven temperatures will first be described generally and then in some detail. As the oven temperature rises to a temperature at which it is required to have the door locked, the main bimetal 54 deflects to the right at its upper end and thereby pivots the base member 52 in a counterclockwise direction through its coupling with the lag-compensating bimetal 58 and, accordingly, the locking extension will be moved into the obstructing position shown in FIGS. 3 and 4. With descending oven temperatures after the cleaning cycle has been completed, the base member 52 will pivot clockwise in accordance with the deflection to the left of the upper end of the main bimetal 54 and thus move the lock extension 62 out of an obstructing position at the rear end of the drawbar.
Referring to FIGS. 7 and 8, it will be appreciated that if the lag-compensating bimetal 58 were simply a rigid, nondeflecting member, so that in effect the upper end of the main bimetal would be directly coupled to the lower end of the pivotal base member 52, the base member would always have a given orientation for a given temperature of the main bimetal. Now, while the upper end of the main bimetal and the lower end of the lag-compensating bimetal are held together by the clamping action of the circular spring 56 (except under an abnormal stress condition), only the upper end of the lagcompensating bimetal is fixedly attached to the upper end portion 60 of the base member. In other words, and as may be seen in FIGS. 7 and 8, the length of the compensating bimetal bridges the pivot point 53 of the base member. Thus, if the lagcompensating bimetal deflects in the direction as shown in FIG. 7 from a straight line, and with a given position of the upper end of the main bimetal, the base member is rotated in a counterclockwise (toward locking) direction since the lower end of the lag-compensating bimetal is held against the upper end of the main bimetal by the noted clamping force, and the only part free to move is the base member under these conditions. Conversely, if the lag-compensating bimetal deflects in the direction as shown in FIG. 8 from a straight line, with a given position of the upper end of the main bimetal, the base member is rotated in a clockwise (away from locking) direction.
It will further be appreciated that, as noted before, the temperatures of the main bimetal and lagcompensating bimetal are not the same as oven temperatures, but simply reflect the oven temperatures, and will lag somewhat in following changes in oven temperatures. Thus, with the oven temperatures rising toward heat cleaning temperatures from a cold start, the differentials in temperature will be in the order of the following examples with the described arrangement. With an oven temperature of, say, 550 F. and rising, the main bimetal 54 may have a temperature of about 300 F., while the lagcompensating bimetal 58, being further removed from the oven and in more limited heat-receiving relation than the main bimetal, may have a temperature of about 200 F. With a given analogous temperature condition experienced by the bimetals, the lag-compensator bimetal is selected from that group which has the properties of negative deflection suitable for the analogous temperature conditions experienced. For example, a Chace No. 4600 bimetal has the property of negative deflection below 250 F and positive deflection above 250 F. Thus with the low-expansion side of both bimetals to the right as shown in FIGS. 7 and 8, (the low side with respect to the lag-compensating bimetal meaning the low side during a positive deflection condition above 250 F.), the bimetals will assume positions similar to that shown in FIG. 7 with a rising oven temperature of about 550 F. The FIG. 7 representation is intended to correspond with a barely locked condition of the latching means in which the locking extension portion 62 of the locking means has just moved to a position obstructing the return of the drawbar. Upon a further increase in oven temperatures into the heat cleaning temperature range, the main bimetal 54 will, of course, deflect farther to the right at its upper end and the locking extension portion 62 will also move farther to the left behind the drawbar.
After the heat cleaning cycle has been terminated and the oven temperature is dropping, the condition at the time the latching means is to be unlocked will occur with the parts having the general relationship as shown in FIG. 8. Since the main bimetal 54 has had an opportunity to reach a temperature above that which it had with respect to FIG. 7, such as 400 F., the main bimetal upper end will be deflected farther to the right as shown. The lag-compensating bimetal 58 will also have a substantially higher temperature (e.g., 350 F.) than the temperature it had when it assumed the position in FIG. 7, and accordingly will be deflected in a positive way as shown. Accordingly, it will be appreciated that with the arrangement as described the lag-compensating bimetal aids the main bimetal in achieving locking under the FIG. 7 conditions, and aids the main bimetal in achieving unlocking under the FIG. 8 conditions, since in FIG. 7 the action of the lag-compensating bimetal is to rotate the base member 52in a counterclockwise direction, while in FIG. 8 it is to rotate it in a clockwise direction. Thus, the arrangement according to the invention substantially reduces the differential between the locking and unlocking temperatures of the oven.
The circular wire 56 arrangement not only serves to couple the main bimetal and lag-compensating bimetal, but also serves as a stress relief means if any part of the mechanism becomes jammed against movement while the bimetals change in temperature and accordingly deflect. The coupling arrangement providing the single point contact between the lag-compensating and the main bimetals is also advantageous in providing minimal frictional drag between these members, thus also promoting calibration.
An alternate arrangement embodying the invention is shown in FIG. 9 in which the coupling between the lower end of the lag-compensating bimetal 58, which is of the negative and positive deflection type, is through an adjustable screw 70 carried by the lower end of the lag bimetal and urged toward the upper end of the main bimetal 54 by the action of the leaf spring 72 which has its upper end sandwiched between the tab portion 60 of the base member 52, and the upper end of the lag-compensating bimetal 58. The leaf spring 72 performs essentially the same function as the circular spring 56 in that it urges the ends of the compensating bimetal and main bimetal together, and serves as stress relief means. In other respects, the action of the FIG. 9 embodiment is essentially the same as that illustrated in FIGS. 7 and 8.
While the invention has been described in terms of using bimetals, it is considered within the purview of those skilled in the art to use other differentially expansible materials to accomplish the aims ofthe invention.
l. A latch and lock arrangement for the door of a pyrolytic self-cleaning oven heatable to a cooking temperature range, and to a higher cleaning temperature range, including:
latching means movable between door-latched and doorunlatched positions;
locking means movable between latch-locked and latch-unlocked positions;
first means responsive to oven temperatures for moving said locking means between said locking means position; and
second means responsive to oven temperatures for aiding movement of said locking means toward said latch-locked position as the oven temperature rises in the temperature range between a cooking and cleaning temperature range, and for aiding movement of said locking means toward said latch-unlocked position as the oven temperature falls through said temperature range between said cooking and cleaning temperature ranges.
2. An arrangement according to claim 1 wherein:
said first means and said second means comprise bimetals.
3. An arrangement according to claim 2 wherein:
said second bimetal is located relative to said oven and said first bimetal to be subjected to oven temperatures to a lesser degree than said first bimetal.
4. An arrangement according to claim 2 wherein:
said second bimetal means comprises a bimetal element having negative deflection characteristics at temperatures experienced by said second bimetal as said oven temperature rises in the temperature range between a cooking and cleaning temperature range, and having positive deflection characteristics at temperatures experienced by said second bimetal as said oven temperature falls through the temperature range between said cooking and cleaning temperature range.
5. An arrangement according to claim 2 including:
means for transferring the moving force of said first bimetal means to said locking means, said transferring means including stress resilient means for preventing overstress of said bimetals under conditions blocking movement of said locking means between said positions,
6. An arrangement according to claim 2 including:
means mounting said locking means for movement as a first order lever with said first bimetal applying a force spaced in one direction from the fulcrum of said lever;
means for transferring said force to the opposite end portion of said lever, said opposite end portion operating means movable into obstructing relationship with said latching means.
7. An arrangement according to claim 6 wherein:
said means for transferring said force includes said second bimetal, said second bimetal bridging the fulcrum of said lever with one end of said second bimetal being rigidly connected to said opposite end portion of said lever, and the other end of said second bimetal being coupled through stress resilient means with a movable portion of said first bimetal.
8. An arrangement according to claim 2, including:
a drawbar movable in accordance with operation of said latching means, said drawbar including a main portion and a downwardly-bent depending portion, said depend ing portion lying at an acute angle relative to said main portion.
9. An arrangement according to claim 8 wherein:
the bend line formed between said main and depending portions extends in a direction which, when said drawbar is in a position corresponding to said latching means being in a latched position, forms an opening angle with the line of travel of the obstructing portion of said locking means as said obstructing portion is moved in an unlocking direction.
10. A latch and lock arrangement for the door of a pyrolytic self-cleaning oven heatable to a cooking temperature range, and to a higher cleaning temperature range, including:
latching means movable between door-latched and doorunlatched positions;
locking means movement to locking and unlocking positions at substantially the same oven temperature irrespective of whether said oven temperature is rising toward a heat cleaning temperature range, or falling from a heat cleaning temperature range.