US3438666A

US3438666A - Latching mechanism with temperature-responsive blocking device

Info

Publication number: US3438666A
Application number: US637504A
Authority: US
Inventors: Karl H Erickson
Original assignee: Amerock Corp
Current assignee: Amerock Corp
Priority date: 1967-05-10
Filing date: 1967-05-10
Publication date: 1969-04-15
Anticipated expiration: 1986-04-15

Description

April 15,1959 K H. ERICKSON 3,438,666

LATCHING MECHANIM WITH TEMPERATURE-RESPONSIVE BLOGKING DEVICE Filed May l0. 1967 sheetv @f2 jlwfommsx/ Aprll 15, 1969 K. H. ERICKSON 3,438,656

LATCHING MECHANISM WITH TEMPERATURE-RESPONSIVE BLOCKING DEVICE :filed May lo, 1967 v sheet 2 of 2 United States Patent 3,438,666 LATCHING MECHANISM WITH TEMPERATURE- RESPONSIVE BIACKING DEVIQE Karl H. Erickson, Rockford, Ill., assigner to Amerock Corporation, Rockford, Ill., a corporation of Connecticut Filed May 1t), 1967, Ser. No. 637,504 Int. Cl. Etl'b 5]/00, 65/44 U.S. Cl. 292-210 8 Claims ABSTRACT oF THE "piscLosURE A temperature-responsive blocking device having a blocking member which is rotated into blocking relation with a latch for a self-cleaning oven to prevent movement of the latch to an unlatched position when the temperature of the oven is above a predetermined value. The blocking member is rotated solely by the action of a spiraled bimetallic coil which is subjected only to thermal stresses imposed by normal expansion and contraction of the met'al strips forming the coil.

Background of the invention` Summary of the invention The primary aim of the present invention is to provide a new and improved blocking device of the above character which remains more precisely sensitive to temperature changes throughout its service life than prior arrangements of the same general type and which, at the same time, may be calibrated more easily and accurately to cause the blocking member to rotate into its blocking position at a precisely selected temperature. In a more detailed aspect, the invention contemplates a novel blocking device in which the position of the blocking member is determined exclusively by the natural thermally stressed condition of the bimetallic coil, and in which the coil is substantially free of external mechanical forces in all positions of the blocking member thereby to reduce the likelihood of over-stressing the coil.

To achieve these ends, the blocking member is rotated into and out of blocking relation with the latch solely by the action of the coil as the latter winds and unwinds in response to temperature changes. Moreover, the blocking member is left free to rotate to any position demanded by the thermally stressed coil without restricting normal expansion and contraction of the coil. Since no external mechanical force is used to rotate the blocking member and since the coil is free to expand and contact in accordance with its natural tendencies, the danger of overstressing the coil and destroying its sensitivity is substantially eliminated.

Brie]t description of the drawings FIGURE 1 is a fragmentary vertical cross-section of an exemplary applicance equipped with a latching mechanism having a blocking device embodying the novel features of the present invention.

FIG. 2 is a fragmentary cross-section taken substantially along the line 2-2 of FIG. 1 and showing the 3,438,666 Patented Apr. 15, 1969 ICC parts with the latch in a latched position and with the blocking member in an inactive position.

FIG. 3 is a fragmentary cross-section taken substantially along the line 3 3 of FIG. 1.

FIG. 4 is a fragmentary cross-section. taken substantially along the line 4 4 of FIG. 3.

FIG. 5 is a fragmentary view similar to FIG. 2 but showing the blocking member in an active position.

FIG. `6 is a fragmentary view similar to FIG. 5 but showing the blocking member in an intermediate position.

FIG. 7 is an enlarged exploded perspective view of part of the blocking device.

Detailed description As shown in the drawings for purposes of illustration, the invention is embodied in a latching mechanism cornprising a latch 10 mounted within the cabinet 11 of an appliance such as a self-cleaning oven and having an elongated bolt 13 selectively engageable with a strike 14 on the oven door 15 to latch the door in a tightly closed position prior to operation of a high-temperature cleaning unit (not shown) for burning olf food and grease from the oven walls. In such a latch, an operating lever 16 is pivoted on a supporting base 17 is connected to the bolt in such a manner that counterclockwise swinging of the lever from an unlatched position shown in phantom in FIG. 2 to a latched position shown in full results in corresponding movement of the bolt from an unlatched position to a latched position in which a hooked outer end 19 of the bolt is disposed in engagement with the strike to hold the door tightly sealed against the cabinet. To prevent activation of the high-temperature cleaning unit when the door is open or free to open, a safety switch 20 is connected electrically into the control circuit of the unit and is positioned on the base 17 to be closed by the lever as the latter moves to its latched position so that the circuit will be conditioned for operation only when the door is closed and latched.

Only a brief description of the latch 10 itself will be presented herein since reference may be had to my copending application Ser. No. 622,142, led Mar. l0, 1967, for more specific details of the construction and operation of a latch of this type. In general, the supporting base 17 is disposed between the oven and the top wall 21 of the cabinet 11 and is mounted on an upper oven wall 23 which is separated from the oven liner 24 by a layer of insulation 25. The operating lever 16 is generally U- shaped in elevation and comprises upper and lower

horizontal plates

26 and 27, the lower plate being connected pivotally to the base by a rivet 29 and being joined to the upper plate by an upright wall 30 (FIG. 3) extending between the two plates. To swing the lever about the axis of the rivet between its unlatched and latched positions, a handle 31 accessible from the front of the cabinet is fastened at its inner end to the upper plate 26 and projects outwardly through a slot 33 located between the top of the door 15 and the top wall 21 of the cabinet. As the handle is moved manually back and forth in an arc along the front of the cabinet, the corresponding motion of the lever is transmitted to the bolt 13 by a driving link 34 whose outer end is pivotally connected to the bolt by a rivet 35 and whose inner end is similarly connected to the lower lever plate 27 by a rivet 36. The bolt is mounted for compound pivoting and sliding movement on the rivet 29 and is moved into and out of engagement with the strike 14 (see FIG. 2) as the lever is swung back and forth between the unlatched and latched positions.

I-n appliances operated under high temperature conditions, it is desirable to prevent unlatching and opening of the door when the operating temperature is above a dangerous level. For example, opening of the door 15 of a self-cleaning oven during operation of the high-temperature cleaning unit would allow smoke and odors to escape from the oven chamber and would admit oxygen into the chamber thus creating the danger of a sudden llame. In the present instance, movement of the latch 10 to the unlatched position when the temperature within the oven exceeds a predetermined safe value is prevented by a blocking device 37 including a blocking member 39 which is rotated into blocking relation with the latch (see FIG. in response to the expansion of a spiraled bimetallic coil 40 adapted to Sense the temperature within the oven.

The present invention contemplates a novel blocking device 37 in which the blocking member 39 is rotated into and out of blocking relation with the latch solely by the action of the bimetallic coil 40, is always positioned exactly in accordance with the natural thermally stressed condition of the coil, and is left free to rotate to any position demanded by the coil without restricting normal expansion and contraction of the coil. For these purposes, the Winding and unwinding action undertaken by the coil in response to changes in temperature is used to full advantage to rotate the blocking member into and out of blocking relation with the latch without the air of external mechanical forces. In the blocking position, the blocking member prevents unlatching of the latch and yet is free to move relative to the latch so as to permit the coil to expand in accordance with its natural tendencies. As a result, the danger of mechanically overloading the coil and destroying its sensitivity is eliminated since the coil is always free of stresses imposed by mechanical rforces.

In the present instance, the blocking member 39 is centrally located on the upper side of the inner end portion of the base 17 and is fastened to the upper end of a vertical shaft 41 (FIG. 3) rotatably m-ounted in the base and projecting downwardly through the upper oven wall 23 to the level of the oven liner 24. Near its lower end, the shaft is journaled in a horizontal portion 43 of an angularly bent bracket 44 fastened to the underside of the base by rivets 45. The bimetallic coil 40 is connected to the lower end of the shaft and, as the coil winds and unwinds in response to temperature changes in the oven, the shaft is rotated about its own axis thereby turning the blocking member back and forth between an active position (FIG. 5) blocking unlatching of the latch 10 and an inactive position (FIG. 1) leaving the latch free for movement to the unlatched position. To prevent the insulation 25 from restricting rotation of the shaft, a semicylindrical shield 46 (FIG. 3) extends along the shaft and is fastened to a vertical portion 47 of the bracket 44, the shield and the bracket thus coacting to form an enclosure surrounding the shaft.

As shown most clearly in FIGS. 3 and 4, the coil 40 comprises a pair of dissimilar resilient metal strips such as brass and iron bonded together in face-to-face relation and wound spirally about the axis of the shaft 41. An inner end 49 of the coil is bent inwardly from the inner turn of the coil and is clamped rigidly within a vertical slot 50 formed in the lower end of the shaft. To anchor the coil relative to the shaft, an outer end 51 of the coil is bent outwardly and projects loosely through a slot 53 formed in a vertical lower leg 54 integral With and depending from the horizontal portion 43 of the bracket 44. The coil is protected from the insulation 25 by a shroud 55 (FIGS. 1 and 3) fastened to the bracket 44 and enclosing all of the coil except the lower side thereof which is exposed directly to the heat in the oven chamber. Since the coil herein unwinds as the metal strips expand, the shaft and the blocking member 39 are turned counterclockwise by the inner end 49 of the coil as the temperature increases in the oven chamber, In all positions of the blocking member, the metal strips are subjected only to stresses imposed by thermal expansion and contraction and are never wound mechanically against their own resiliency. Thus, when considered as a spring, the coil is always relaxed and the inner end 49 thereof exerts substantially no lforce on the edges of the anchoring slot 53 in the bracket 44. That the coil is never wound spring fashion is illustrated by the fact that the relative positioning of the

ends

49 and 51 at a given temperature before installation of the coil is exactly the same as the relative positioning of the ends at the same temperature after the coil has been installed and has been in normal service use.

Preferably, the blocking member 39 is formed by a lug 57 (FIG. 7) integral with an upstanding from one end of a flat plate 59 adapted to be coupled for rotation in yunison with the shaft 41 and disposed below the level of the lower lever plate 27. When the oven is at room temperature, the blocking member is disposed in the inactive position (FIG. 5) in which the lug is spaced angularly from an inner extension 60 of the lower lever plate 27 and is positioned out of the path followed by the extension during counterclockwise movement of the operating lever 16 from the latched position to the unlatched position. With the blocking member in the inactive position, the extension simply passes by the lug and over the plate 59 to permit free movement of the lever between its positions.

As the temperature within the oven begins to increase, the bimetallic coil 40 expands and unwinds so that the inner end 49 of the coil begins to rotate the shaft 41 to move the lug 57 counterclockwise in an arcuate path, the position of the lug in the path being determined exclusively by the natural thermally stressed condition of the coil. When the self-cleaning unit is being used and initially raises the temperature of the oven to a preselected value such as 600 F., the lug is turned to an intermediate position (FIG. 6) in which the leading edge of a curved outer abutment surface 63 of the lug is disposed just within the path followed by a relatively long arcuate abutment surface 64 of slightly greater curvature formed on the lever extension 60 and spaced about l/16 of an inch from the lug. Accordingly, the lug Will engage the extension upon initial movement of the operating lever 16 toward the unlatched position and will block complete unlatching movement of the lever thereby to prevent opening of the door 15 when the cleaning unit is operatmg.

Continued operation of the cleaning units increases the temperature of the oven to a maximum level of about 900 F. The lug 57 thus continues to turn counterclockwise in the active portion of the arcuate path and moves to the final position (FIG. 6) in which the abutment surface `63 is face-to-face with the abutment surface 64 to block unlatching of the latch. During such turning, the lug moves freely past the extension `60 since the

abutment surfaces

63 and 64 are spaced `from each other and since the active portion of the arcuate path is sutlciently long to permit rotation of the lug to any position demanded by the coil 40 as the temperature in the oven is raised to a maximum value. As a result, the latch does not engage and restrict rotation 'of the blocking member 39 to interfere with normal expansion of the coil 40. The latter thus is never in danger of being mechanically overstresed and therefore will remain precisely sensitive to temperature changes throughout the service life of the oven.

To enable calibration of the blocking device 37, that is, to set the lug 57 for rotation into the intermediate position (FIG. 6) at precisely 600 F. the blocking member 39 is adapted to be adjusted angularly about the axis of the shaft 41. For this purpose, the upper end portion 65 (FIG. 7) of the shaft project loosely through a hole 66 formed in the mounting plate 59 of the blocking member to leave the latter free for rotation on the shaft. The mounting plate rests on a fiat base plate 67 rigid with the upper end of the shaft and is coupled for rotation with the base plate and the shaft by a screw 69 projecting through an arcuate slot 70 formed in the mounting plate and threaded into a hole 71 in the base plate. To calibrate the blocking device, the screw 69` is loosened and the temperature is raised to 600 F. The blocking member 39 then is rotated about the shaft to adjust the lug 57 to the position shown in FIG. 6 thereby positioning the lug in accordance with the thermally stressed condition of the coil 40 at that temperature. Thereafter, the screw is tightened to hold the blocking member in its selected angular position on the shaft and the base plate 67. This calibration is relatively simple since the workman easily can see when the lug V57 is positioned properly with respect to the extension `60. Moreover, only the characteristics of the coil need be taken into account in making the adjustment since the coil is the only instrumentality affecting the position of the lug.

I claim as my invention:

1. In a latching mechanism adapted to be held in a latched condition under certain operating temperatures, the combination of, a support,a latch mounted on said support for movement between latched and unlatched positions, a first abutment surface on said latch and movable along a predetermined path as the latch is moved from said latched position to said unlatched position, a blocking member mounted for rotation on said support and having a second abutment surface movable in an arcuate path, first along an inactive portion disposed out of said first path and then along an active portion disposed in said first path but spaced from said first abutment surface, the length of said active portion being proportional to a range of temperatures varying from a predetermined value to a normal maximum operating value, said second abutment surface being operable when positioned in said active portion of said arcuate path to engage said first abutment surface after initial movement of the latch toward said unlatched position thereby to block complete movement of the latch toward said unlatched position, a bimetallic coil having one end fastened to said support and having an opposite end fastened to said blocking member and movable relative to said one end as said coil winds and unwinds in response to temperature changes thereby to rotate said second abutment surface to a position in said arcuate path precisely correlated with the natural thermally stressed condition of the coil at any given temperature, said coil holding said second abutment surface in said inactive portion of said arcuate path when the temperature is below said predetermined value and being thermally expanded to turn said second abutment surface into said active portion when the temperature exceeds said predetermined value, and said second abutment surface moving freely alongside said first abutment surface during such turning by virtue of the spacing between the two surfaces and moving to any position demanded by said coil without restricting normal expansion thereof by virtue of the length of said active portion of said arcuate path.

2. A latching mechanism as defined in claim 1 in which said first abutment surface is arcuately curved on a greater radius that the arcuate path and is at least equal in length to the active portion of said path.

3. A latching mechanism as defined in claim 1 further including a shaft journaled in said support and mounting said blocking member for rotation on the support, said opposite end of said coil being fastened to said shaft to rotate the latter, and adjustable means normally coupling said shaft and said blocking member for rotation in unison, said means being selectively releasable from said blocking member to leave the blocking member free for rotation about said shaft and thereby permit adjustment of the angular position of said second abutment surface in said arcuate path independently of said coil.

4. In a latching mechanism adapted to be held in a latched condition under certain operating temperatures, the combination of, a support, a latch mounted on said support for movement between latched and unlatched positions, a first abutment surface on said latch and movable along a first path as the latch is moved from said latched position to said unlatched position, a blocking member mounted for movement on said support and having a second abutment surface movable in a second path, first along an inactive portion disposed out of `said first path and then along an active portion disposed in said first path, the length of said active portion being proportional to 4a range of temperatures varying from a predetermined value to a normalmaximum operating value, said second surface being spaced from said first surface when positioned in said active portion and being operable to engage said first surface after initial movement of the latch toward said unlatched position thereby to block complete movement of the latch to the unlatched position, a spiraled bimetallic coil having one end fastened to said support and having an opposite end operably connected to said blocking member and movable relative to said one end as the coil winds and unwinds in response to temperature changes thereby to move said second surface to a position in said second path precisely correlated with the natural thermally stressed condition of the coil at any given temperature, said coil holding said second surface within said inactive portion of said second path when the temperature is below said predetermined value and unwinding to shift said second abutment surface into the active portion of said second path when the temperature exceeds said predetermined value, and said second surface moving freely along the active portion during such shifting by virtue of the spacing between the two surfaces and of the length of the active portion.

5. In a latching mechanism adapted to be held in a latched condition under certain'operating temperatures, the combination of, a support, a latch mounted on said support for movement between latched and unlatched positions, a first abutment surface on said latch and movable along a first path as the latch is` moved from said latched position to said unlatched position, a blocking member mounted for rotation on said support and having a second abutment surface movable in an arcuate path, first along an active portion disposed out of said first path and then along an inactive portion disposed in said rst path, the length of said active portion being proportional to a range of temperatures varying from a predetermined value to a normal maximum operating value, said second surface being spaced from said first surface when positioned in said active portion of said arcuate path and being operable to engage said first surface after initial movement of said latch toward said unlatched position thereby to block complete movement of the latch to the unlatched position, a bimetallic element connected between said blocking member and said support and operable to expand and contract in response to temperature changes thereby to rotate said second surface to a position in said arcuate path precisely correlated with the natural thermally stressed condition of the element at any given temperature, said element holding said second surface within said inactive portion of said arcuate path when the temperature is below said predetermined value and being stressed thermally to turn said second surface into said active portion when the temperature exceeds said predetermined value, and said second surface moving freely relative to said ii-rst surface and moving freely along the active portion during such turning by virtue of the spacing between the two surfaces and by virtue of the length of the active portion.

6. In a latching mechanism adapted to be held in a latched condition under certain temperature environments, the combination of, a support, a latch mounted on said support and movable along a predetermined path from a latched position to an unlatched position, a blocking member mounted on said support for rotation in an arcuate path between an inactive position disposed out of said first path and an active position disposed in said rst path and engageable with said latch to block movement of the latter from said latched position to said unlatched position, a spiraled bimetallic coil having a one end held on said support and having an opposite end connected to said blocking member and movable relative to said one end as the coil Winds and unwinds in response to temperature changes thereby to turn the blocking member to a position in said arcuate path `determined exclusively by the natural thermally stressed condition of the coil at any given temperature, said coil holding said blocking member in said inactive position at normal room temperature and being stressed thermally to positively rotate the blocking member to said active position when the temperature increases to a value signicantly higher than room temperature, and said coil being mechanically unstressed at normal room temperature with said one end exerting substantially no force on said support.

7. A latching mechanism as dened in claim 6 in which the relative positioning of the ends of the coil at normal room temperature before installation of the coil and before fastening of the ends to the blocking member and the support is exactly the same as the relative positioning of the ends at normal room temperature after installation of the coil and after the coil has rotated said blocking member back and forth between said active and inactive positions in normal operating fashion.

8. A latching mechanism as defined in claim 6 in which said blocking member is rotatably mounted on a shaft journaled in said support, said opposite end of said coil being fastened to said shaft to yrotate the latter, and adjustable means normally coupling said shaft and said blocking member for rotation in unison, said means being selectively releasable from said blocking member to leave the blocking member free for rotation about said shaft and thereby permit adjustment of the angular position of the blocking member independently of said coil.

References Cited UNITED STATES PATENTS 2,598,067 5/1952 OBrien 110-18 3,05 0,048 8/ 1962 Scott 126-273 3,362,398 1/1968 Fane 126-273 MARVIN A. CHAMPION, Primary Examiner.

JOHN R. MOSES, Assistant Examiner.

U.S. Cl. X.R.