Abstract:
A compact, reliable motorized oven door latch assembly utilizes a latch that pivotally connects to a motor at an axis that is offset from the motor&#39;s axis. The latch includes a latch guide that is guided by a slot in a housing of the assembly. Rotation of the motor moves the latch between open and closed positions. A cam rotationally engages the motor and includes axially disposed cam surfaces that interact with side-by-side switches to sense when the latch is open and closed. The assembly includes a reusable release/service feature that allows the latch to be opened without operation of the motor if the latch becomes stuck in the closed position. The service feature includes a resiliently deformable flange that defines part of the guide surface.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to latch mechanisms, and particularly relates to motorized latches that are used to lock oven doors shut during high temperature self cleaning operations.  
         [0003]     2. Description of Related Art  
         [0004]     In self-cleaning ovens, it is advantageous that the oven door be latched against inadvertent opening during such period of time as the oven is at a high temperature. Various types of manual and motorized latches have been proposed for this application, and it is now customary to include some form of thermostatically controlled mechanism to prevent unwanted or inadvertent opening of the door.  
         [0005]     Conventional motorized oven door latch mechanisms are often bulky, which makes it difficult to incorporate such mechanisms into oven designs. Conventional latch mechanisms are also frequently mechanically complex, which makes them expensive to manufacture and prone to failure during operation in the extremely hot environment of an oven.  
         [0006]     If a motorized oven door latch mechanism breaks while in the closed position (for example, due to motor failure), it is difficult to open the locked oven door to repair the oven door latch mechanism. It is known in the art to provide a single-use release/service feature to allow the latch to be opened. As illustrated in  FIG. 5  of U.S. Pat. No. 6,315,336, a J-shaped guide slot  28  is formed in a housing of the oven latch. During normal operation of the latch, the relatively straight portion of the “J” defines a cam surface that the latch arm  14  follows between open and closed positions. When the latch arm  14  is in the closed position illustrated in  FIG. 5 , the latch arm  14  may be forced open by applying force to the latch arm  14 , which permanently deforms or breaks the piece of metal that defines the inside curvature of the “J” to allow the latch arm  14  to move into the open position. Unfortunately, the entire mechanism must be replaced after such permanent deformation of the guide slot  28 .  
       SUMMARY OF THE INVENTION  
       [0007]     Accordingly, one aspect of one or more embodiments of this invention provides a simple, cost-effective, reliable, compact motorized oven door latch mechanism.  
         [0008]     Another aspect of one or more embodiments of this invention provides a motorized oven door latch mechanism with a reusable release/service feature that allows an operator to open an oven door that is locked closed without breaking the oven door latch mechanism.  
         [0009]     Another aspect of one or more embodiments of this invention provides an oven door latch assembly for locking an oven door in a closed position. The assembly includes a housing and a motor mounted to the housing. The motor includes an output shaft that defines a motor axis. The assembly also includes an oven door latch pivotally connected to the output shaft at a latch axis that is offset from the motor axis. The latch is pivotable relative to the output shaft about the latch axis. Rotational movement of the output shaft moves the oven door latch between open and closed positions.  
         [0010]     According to a further aspect of one or more of these embodiments, the assembly also includes a cam mounted to the output shaft to rotate with the output shaft about the motor axis. The cam has a first cam surface that faces a direction parallel to the motor axis. The assembly also includes a first switch disposed on the housing and positioned to be actuated by the first cam surface.  
         [0011]     According to a further aspect of one or more of these embodiments, the oven door latch pivotally connects to the output shaft via a pivotal connection between the cam and oven door latch.  
         [0012]     According to a further aspect of one or more of these embodiments, the cam includes a second cam surface that faces a direction parallel to the motor axis. The assembly further includes a second switch disposed on the housing and positioned to be actuated by the second cam surface. The first cam surface may be disposed farther from the motor axis than the second cam surface. The first cam surface and first switch may be positioned such that the first cam surface actuates the first switch when the oven door latch is in the closed position. The second cam surface and second switch may be positioned such that the second cam surface actuates the second switch when the oven door latch is in the open position.  
         [0013]     According to a further aspect of one or more of these embodiments, the assembly also includes a guide surface disposed on one of the housing and the oven door latch, and a latch guide disposed on the other of the housing and the oven door latch. Abutting contact between the latch guide and guide surface guides the oven door latch as it moves between the open and closed positions. The guide surface may be disposed on the housing and the latch guide may be disposed on the oven door latch.  
         [0014]     The latch guide and oven door latch may be integrally formed. The latch guide may be stamped into, molded with, or cast with the oven door latch.  
         [0015]     According to a further aspect of one or more of these embodiments, the guide surface is defined by a slot in the housing.  
         [0016]     According to a further aspect of one or more of these embodiments, the assembly also includes an elastically deformable element that defines a portion of the guide surface, wherein the elastically deformable element is elastically deformable in a direction that allows the oven door latch to move from the closed position into the open position without rotation of the output shaft.  
         [0017]     According to a further aspect of one or more of these embodiments, the assembly is incorporated into an oven. The oven has an oven door with open and closed positions. The assembly locks the oven door closed when the oven door is closed and the latch moves from its open to its closed position. The latch permits the oven door to be opened when the latch is in its open position.  
         [0018]     According to a further aspect of one or more of these embodiments, the assembly includes a flange disposed on the housing. The flange defines a portion of the guide surface. The flange is elastically deformable in a direction that allows the oven door latch to move from the closed position into the open position without rotation of the output shaft.  
         [0019]     Another aspect of one or more embodiments of the present invention provides a method of making an oven door latch assembly for locking an oven door in a closed position. The method includes mounting a motor to a housing. The motor includes an output shaft that defines a motor axis. The method also includes providing a guide surface on the housing and integrally forming a latch guide with an oven door latch. The method also includes pivotally connecting the oven door latch to the output shaft at a latch axis that is offset from the motor axis. The pivotal connection allows the latch to pivot relative to the output shaft about the latch axis. Rotational movement of the output shaft moves the oven door latch between open and closed positions. The cam track has a guide surface. The latch guide abuts and is guided by the guide surface as the oven door latch moves between the open and closed positions. According to a further aspect of one of these embodiments, integrally forming the latch guide with the oven door latch includes stamping the latch guide into the oven door latch.  
         [0020]     Additional and/or alternative advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, disclose preferred embodiments of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     Referring now to the drawings which from a part of this original disclosure:  
         [0022]      FIG. 1  is a front, right, perspective view of an oven door latch assembly according to an embodiment of the present invention;  
         [0023]      FIG. 2  is a partially cut away, right side view thereof;  
         [0024]      FIG. 3  is an exploded view thereof;  
         [0025]      FIG. 4A  is a top view of a cam of the oven door latch assembly in  FIG. 1 ;  
         [0026]      FIG. 4B  is a side view of the cam in  FIG. 4A ;  
         [0027]      FIG. 4C  is a bottom view of the cam in  FIG. 4A ;  
         [0028]      FIG. 5  is a partially-cross-sectional bottom view of the oven door latch assembly in  FIG. 1  incorporated into an oven, with the latch in a closed position;  
         [0029]      FIG. 6  is a partially-cross-sectional bottom view of the oven door latch assembly in  FIG. 1  incorporated into an oven, with the latch in an open position;  
         [0030]      FIG. 7  is a partially-cross-sectional bottom view of the oven door latch assembly in  FIG. 1  incorporated into an oven, with the latch in an open released position; and  
         [0031]      FIG. 8  is a partial bottom perspective view of the latch in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0032]      FIGS. 1-3  illustrate an oven door latch assembly  10  according to an embodiment of the present invention. As best shown in  FIG. 3 , the assembly  10  comprises a housing  20 , a motor  30 , a cam  40 , an oven door latch  50 , and two switches  60 ,  70 . The illustrated housing  20  is designed to be mounted to an oven via any suitable fastening mechanism (e.g., bolts, screws, glue, integral formation, etc.). Alternatively, the housing may be integrally formed with a portion of the oven.  
         [0033]     The motor  30  is an A/C synchronous motor, but may alternatively comprise any other suitable motor (e.g., D/C motor, hydraulic motor, etc.). The motor  30  preferably has enough torque that an additional gear train is not required to drive the assembly  10 . Omission of such a conventional gear train, such as that disclosed in U.S. Pat. No.  5 , 220 , 153 , enables the assembly  10  to be smaller, cheaper, and more reliable than conventional latch mechanisms.  
         [0034]     As shown in  FIG. 3 , the motor  30  has a rotatable output shaft  100  that engages a corresponding hole  110  in the cam  40  so that the cam  40  rotates with the output shaft  100  about an axis  120  of the motor  30 . As shown in  FIGS. 3, 4A , and  4 C, the illustrated output shaft  100  and hole  110  have mating double-D cross-sections, but may alternatively have any other suitable cross-sections or may be otherwise engaged to enable the cam  40  to be driven for rotation by the motor  30  (e.g., through a keyway, clamping screw, etc.).  
         [0035]     As shown in  FIGS. 3 and 4 C, the latch  50  pivotally connects to the cam  40  via a pivot pin  150  that fits into corresponding holes  160 ,  170  in the cam  40  and latch  50 , respectively. As shown in  FIG. 4C , the holes  160 ,  170  and pivot pin  150  define a latch pivot axis  180  that is offset from the motor axis  120 . As a result, the latch  50  pivotally connects to the output shaft  100  at a position that is offset from the motor axis  120 . The latch  50  can freely pivot relative to the cam  40  and output shaft  100  about the latch pivot axis  180 . While the cam  40  creates the offset pivotal connection between the latch  50  and the output shaft  100  in the illustrated embodiment, the offset pivotal connection may alternatively comprise a direct connection between the latch  50  and an enlarged output shaft or other suitable mechanism without deviating from the scope of the present invention.  
         [0036]     Pivotally connecting the latch  50  to the output shaft  100  (either directly or indirectly through the cam  40 ) eliminates the need for an intermediary connecting rod, such as those shown in U.S. Pat. Nos. 6,302,098 and 6,315,336.  
         [0037]     As shown in  FIG. 5 , a latch guide  200  extends downwardly from a central portion of the latch  50 . The illustrated latch guide  50  comprises a pin, but may alternatively comprise any other suitable shape. As shown in  FIG. 8 , the illustrated latch guide  200  is circular and is stamped into the latch  50  such that the guide  200  and latch  50  are integrally formed from one piece. The latch guide  200  therefore forms a large cylindrically shaped dimple in the latch  50 . However, the guide  200  and latch  50  may alternatively be integrally formed using any other suitable manufacturing technique (e.g., integral casting, molding, etc.). Alternatively, the latch guide  200  and latch  50  may be separately formed and subsequently secured to each other (e.g., via welding, threaded engagement, bolts, screws, glue, etc.) without deviating from the scope of the present invention.  
         [0038]     As shown in  FIG. 5 , a cam track  210  is formed in the housing  20 . In the illustrated embodiment, the cam track  210  is a slot that is die stamped into the housing  20 . The cam track has a curved cam/guide surface  220  that abuts the latch guide  200 . While the illustrated cam track  210  is die stamped into the housing  20 , the cam track  210  may alternatively be separately formed and subsequently mounted to the housing  20  (e.g., a curved rail mounted to the housing  20 ). Similarly, while the cam track  210  relies on a slot to define the curved cam surface  220 , the cam track  210  may alternatively comprise a rail or other similar structure that creates the curved guide surface  220 .  
         [0039]     While the illustrated curved cam surface  220  is disposed on the housing  20  and the latch guide  200  is disposed on the latch  50 , the curved cam surface  220  may alternatively be defined by a slot in the latch  50  and the latch guide  200  may be disposed on the housing  20  without deviating from the scope of the present invention.  
         [0040]     Rotational movement of the motor  30  moves the latch  50  between an open position (see  FIG. 6 ) and a closed position (see  FIG. 5 ). The curved cam surface  220  guides the latch guide  200  and latch  50  between the open and closed positions as the motor  30  moves the latch via the offset pivotal connection. When the latch  50  is in the open position shown in  FIG. 6 , it is constructed and arranged to allow opening and closing of an associated oven door  240  of an oven  245 . Conversely, as shown in  FIG. 5 , when the oven door  240  is closed and the latch  50  moves into its closed position, a catch plate  230  on the latch  50  engages a matching plate  250  of the oven door  240  to prevent the oven door  240  from opening relative to the oven  245 . In the illustrated embodiment, the motor  30  rotates the output shaft  100  in a single direction such that continuous rotation of the output shaft  100  cycles the latch  50  between its open and closed positions. Alternatively, the motor  30  could operate in opposing opening and closing directions such that the motor does not rotate a full 360 degrees.  
         [0041]     As shown in  FIG. 5 , the latch assembly  10  includes a reusable service/release feature that allows the latch  50  to be opened when the latch  50  is in the closed position without actuation of the motor  30 . Such a service feature enables a service person to gain access to the otherwise locked oven  245  if the latch assembly  10  fails (e.g., due to motor  30  failure) while the latch  50  is in the closed position. The service feature comprises a flange  260  that defines a portion of the curved cam surface  220  and a portion of the cam track  210 . The flange  260  may be peninsula-shaped as shown and is resiliently (i.e. elastically) deformable in a direction (to the left as shown in  FIG. 5 ) that allows the oven door latch  50  to move from the closed position into the open position without rotation of the output shaft  100 . Alternatively, the flange  260  may be plastically deformable such that the flange  260  may be bent back into shape after it is deformed to allow the latch  50  to be opened.  
         [0042]     To use the release feature, a service person uses a tool  265  such as that illustrated in  FIG. 2  of U.S. Pat. No. 6,302,098, hereby incorporated by reference in its entirety, to apply force to the latch  50  in the manner described that patent. As shown in  FIG. 7 , when a sufficient leftward force is applied to the closed latch  50 , the latch guide  200  deforms the flange  260  to the left, thereby allowing the latch  50  to move to the left, which releases the latch  50  from the plate  250  of the oven door  240 .  
         [0043]     The open position illustrated in  FIG. 7  places the latch  50  in a different position than the open position of the latch  50  during normal operation of the assembly  10  (see  FIG. 6 ). The term “open position” is used throughout this specification and claims to identify any position of the latch  50  in which the latch  50  does not lock the oven door  240  shut.  
         [0044]     Deformation of the flange  260  in one embodiment requires at least  10  pounds of force and in another embodiment requires about  20  pounds of force so that the latch  50  does not accidentally deform the flange  260  and move into the open position.  
         [0045]     The deformation of the flange  260  is elastic such that when the latch  50  is released after opening the oven door  240 , the flange  260  returns to its original shape and position (shown in solid lines in  FIG. 5 ). Consequently, use of the release/service feature does not break the assembly  10 , as is the case in conventional release features that rely on plastic/permanent deformation (see, e.g., U.S. Pat. No. 6,315,336), hereby incorporated by reference in its entirety. The illustrated flange  260  is integrally formed with the housing  20 . The housing  20  and flange  260  therefore preferably comprise a strong, resiliently deformable material. Alternatively, the flange  260  may be discrete from the housing  20  and comprise a material with specifically chosen elastic deformation properties (e.g., spring steel, rubber, etc.).  
         [0046]     The assembly  10  includes sensors that determine whether the latch  50  is open or closed. As shown in  FIG. 1 , the switches  60 ,  70  are mounted side-by-side to the housing  20 . The side-by-side mounting simplifies electrical connection to the oven by facilitating the use of a single electric terminal block connector that connects to both switches  60 ,  70 . As shown in  FIGS. 1, 2 ,  4 A, and  4 B, two cam surfaces  400 ,  410  are disposed on opposing radial sides of an upwardly facing axial end of the cam  40 . Accordingly, the cam surfaces  400 ,  410  face a direction that is parallel to the motor axis  120 . The inner cam surface  400  and inner switch  60  are disposed an equal distance from the motor axis  120  so that the cam surface  400  actuates the switch  60  when the cam surface  400  passes the switch  60 . The hole  160  and pivot axis  180  are positioned on the cam  40  such that the cam surface  400  actuates the switch  60  when the latch  50  is in the open position.  
         [0047]     The outer cam surface  410  and outer switch  70  are disposed an equal distance from the motor axis  120  so that the cam surface  410  actuates the switch  70  when the cam surface  410  passes the switch  70 , which occurs when the latch  50  is in the closed position. Consequently, actuation of the switch  70  indicates to the oven that the latch  50  is closed so that the oven can safely initiate a self-cleaning cycle. Conversely, actuation of the switch  60  indicates to the oven that the latch  50  is in the open position, that the oven door could be opened, and that self-cleaning should not be initiated or should be halted.  
         [0048]     The cam surface  410  and switch  70  are disposed farther from the motor axis  120  than the cam surface  400  and switch  60  so that the inner cam surface  400  does not actuate the outer switch  70  and the outer cam surface  410  does not actuate the inner switch  60 . Alternatively, all four switches  60 ,  70 , and cam surfaces  400 ,  410  could be disposed an equal distance from the motor axis  120 . In such an embodiment, the cam surfaces could extend to different vertical positions to selectively actuate vertically offset switches.  
         [0049]     Positioning the cam surfaces  400 ,  410  on the upper axial end of the cam  40  allows the switches  60 ,  70  to be mounted to the housing  20  in a compact position, which is closer to the motor  30  than is possible in conventional latch sensors that rely on circumferentially disposed cam surfaces (e.g., U.S. Pat. Nos. 5,220,153 and 6,315,336).  
         [0050]     While two switches  60 ,  70  and two cam surfaces  400 ,  410  are illustrated, a single cam surface and switch could alternatively be used. The cam surface and switch could be sized and positioned such that the switch is actuated when the latch  50  is closed and released when the latch  50  is open, or vice-versa. Alternatively, a single cam surface could actuate two switches that are appropriately circumferentially spaced around the motor to indicate that the latch  50  is open or closed. Moreover, the switches  60 ,  70  and cam surfaces  400 ,  410  may be replaced by any other suitable sensor mechanism that is capable of detecting whether the latch is open or closed without deviating from the scope of the present invention.  
         [0051]     The foregoing description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. To the contrary, those skilled in the art should appreciate that varieties may be constructed and employed without departing from the scope of the invention, aspects of which are recited by the claims appended hereto.