Abstract:
A simplified oven door lock reduces the number of components subjected to fatigue from repeated tensile movement. The oven door lock includes a mounting plate, an actuator having an output shaft and the actuator being coupled to the mounting plate, a cam having a mounting hub at its center and an offset hub displaced from the mounting hub, the mounting hub of the cam being coupled to the output shaft actuator so the actuator rotates the cam with respect to the mounting plate, a lock pin extending upwardly at a first position from the mounting plate, an unlock pin extending upwardly at a second position from the mounting plate, a latch mounted to the offset hub of the cam so the latch extends between the lock pin and the unlock pin so that opposing sides of the latch plate slide against the lock pin and the unlock pin as the latch moves in response to the actuator rotating the cam.

Description:
CROSS-REFERENCES  
       [0001]     Cross-reference is made to co-pending U.S. patent application Ser. No. 10/730,296 (Attorney Docket No. 1007-0584), filed Dec. 8, 2003 entitled Motorized Oven Lock for Sealing Oven Door by Steve W. Smock, Harry I. Courter, Greg Wright and Tracy J. Talley, and U.S. patent application Ser. No. 10/730,475 (Attorney Docket No. 1007-0580), filed Dec. 8, 2003, entitled Motorized Oven Lock by Steve W. Smock, Harry I. Courter, Greg Wright and Tracy J. Talley. U.S. patent application Ser. Nos. 10/730,296 and 10/730,475 are both assigned to the same assignee as the present application and the disclosures of both applications are hereby incorporated by reference in their entirety.  
       TECHNICAL FIELD  
       [0002]     The devices disclosed herein relate generally to door locks for self-cleaning ovens and more particularly to oven door locks that block a door latch in its latched position during a self-cleaning cycle.  
       BACKGROUND  
       [0003]     A conventional gas or electric oven is subject to collecting deposits from whatever is placed in the oven to be cooked. Modern ovens are designed to self-clean upon demand by reducing these deposits to dust with high heat. This cleaning method is commonly known as pyrolytic cleaning. The high temperature used for pyrolytic cleaning poses a hazard if the oven door is opened during the cleaning cycle. To prevent this, an oven door lock is employed.  
         [0004]     Many types of oven door locks have been provided that lock the oven door for a period sufficient to complete a pyrolytic cleaning cycle once initiated. Many of these door locks use electrical motors, electromechanical devices or manual manipulation of mechanisms to move a latch to a position in which the latch prevents the oven door from being opened during a self-cleaning cycle. Examples of such locks are disclosed in Phillips, U.S. Pat. No. 6,079,756; Thuleen et al., U.S. Pat. No. 4,082,078; McWilliams, III, U.S. Pat. No. 5,493,099; Smith, U.S. Pat. No. 6,302,098; Swartzell, U.S. Pat. No. 6,315,336; and Malone et al., U.S. Pat. No. 5,220,153.  
         [0005]     The oven lock mechanisms in these and other known locks use complicated mechanical arrangements to move a latch member between a latched and an unlatched position. These mechanisms include springs and irregularly shaped guide slots to manipulate the latch movement between the latched and unlatched positions. The springs present issues of reliability as the spring metal material is subjected to repeated extensions and contractions over its life as well as temperature extremes. The irregular guide slots lead to variations during metal stamping of the plates that may make the latch operations differ from lock to lock. Quality control tolerances may need tightening to address these variations, but that response leads to an increased part rejection rate and added expense to the manufacturing process.  
       SUMMARY  
       [0006]     A simplified oven lock mechanism has been developed to reduce the complexity of oven door locks, eliminate parts that may contribute to a reduction in long term reliability, while providing consistent control of the door latch. A simplified oven door lock reduces the number of components subjected to fatigue from repeated tensile movement. The oven door lock includes a mounting plate, an actuator having an output shaft and the actuator being coupled to the mounting plate, a cam having a mounting hub at its center and an offset hub displaced from the mounting hub, the mounting hub of the cam being coupled to the output shaft actuator so the actuator rotates the cam with respect to the mounting plate, a lock pin extending upwardly at a first position from the mounting plate, an unlock pin extending upwardly at a second position from the mounting plate, a latch mounted to the offset hub of the cam so the latch extends between the lock pin and the unlock pin so that opposing sides of the latch plate slide against the lock pin and the unlock pin as the latch moves in response to the actuator rotating the cam.  
         [0007]     Additional features and advantages of the disclosed oven lock are apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of implementing a motorized oven lock as presently perceived.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The illustrative devices will be described hereinafter with reference to the attached drawings which are given as non-limiting examples only, in which:  
         [0009]      FIG. 1  is a perspective view of a self-cleaning oven with the oven door closed and the oven lock mechanism, which is shown in phantom lines, mounted at the front of the oven frame above the cooking chamber and below the cook top.  
         [0010]      FIG. 2  is a perspective view of the oven lock mechanism shown in  FIG. 1 .  
         [0011]      FIG. 3  is a top plan view of the oven lock mechanism shown in  FIG. 1  with the latch shown in the locking position and phantom lines showing the latch in the unlocked position.  
         [0012]      FIG. 4  is a top plan view similar to  FIG. 3  showing an alternative embodiment of a latch and pin arrangement for the oven lock mechanism shown in  FIG. 2  and  FIG. 3 .  
         [0013]      FIG. 5A, 5B ,  5 C,  5 D, and  5 E depict the interaction of the latch shown in  FIG. 4  with the pin arrangement to latch and unlatch the door of an oven. 
     
    
     DETAILED DESCRIPTION  
       [0014]     The oven door lock mechanism  30  illustrated and described herein enables the latch mechanism  30  to move a latch  36  to a position that locks the oven door  12  in response to a user selecting the self-cleaning cycle for the oven. Such a position is referred to herein as a latched position. The disclosed mechanism  30  facilitates movement of the latch  36  between the latched and unlatched positions without requiring springs or guide slots.  
         [0015]     As shown in  FIG. 1 , for example, the illustrated embodiment of the oven lock mechanism  30  is configured for mounting in a self cleaning oven  10 . The oven  10  includes a door  12  hinged at its bottom to a frame  14 . The frame  14  of the oven  10  is disposed about an oven chamber  16 . A cook top  18  is coupled to the frame and disposed above the oven chamber  16 . The door  12  closes at an interface formed by an inner face of the door  12  and an abutment surface of the oven frame  14 . The inner face of oven door  12  may be provided with a seal for engaging the abutment surface of the frame  14  to help seal oven chamber  16 . Those skilled in the art will recognize that alternatively, the abutment surface of the frame  14  may be provided with a seal for engaging the inner face of the oven door  12 . The disclosed embodiment of the oven door lock mechanism  30  is mounted at the top  26  of the frame  14  of the oven  10  just under the cook top  18 .  
         [0016]     As shown in  FIG. 2 , for example, the illustrated oven lock mechanism  30  includes a mounting plate  32 , a latch  36 , a cam  40 , a motor  44 , two cam-actuated snap switches  46  and  48 , a lock guide pin  50 , and an unlock pin  54 . In more detail, the mounting plate  32  may be a stamped or extruded metal piece made of, for example, G30 galvanized steel. The plate  32  provides a mounting surface for the components of the oven lock mechanism  30 . An upturned flange  58  is formed with a latch opening  60  through which the latch  36  extends for its latching and unlatching functions. The latch  36 , the cam  40 , the motor  44 , switch  48 , and pins  50  and  54  are mounted on one side of mounting plate  32  in the embodiment shown in  FIG. 2 , although the motor  44  may be mounted on the other side of the plate. Snap action switches  46  and  48  may be mounted to plate  32  using known methods, such as screws, for example.  
         [0017]     Screws  64 , for example, may also be used to mount the motor  44  to the mounting brackets  56  that extend upwardly from the plate  32 , as shown in  FIG. 2 . An output shaft of the motor  44  is eccentrically located with respect to the center of the motor and extends downwardly towards the plate  32 . The motor may be, for example, a synchronous induction AC high torque Oven Door Lock class “F” motor. Motor  44  may operate at 3 RPM in response to a 120 VAC, 60 Hz signal, although other speeds and operating voltages may be used.  
         [0018]     With continued reference to  FIG. 2 , lock guide pin  50  and the unlock pin  54  are protrusions that extend upwardly from the plate  32 . The pins may be mounted to the plate  32  with screws, for example, so they may be selectively mounted to the plate or they may be fixedly mounted to the plate by welding, staking, soldering, or the like. While the pins  50  and  54  are shown as being cylindrical, other shapes may be used to guide the movement of the latch  36  as it is urged by the rotation of the cam  40 . Pins  50  and  54  are positioned so they are on opposing sides of the latch  36  and are staggered with respect to one another. That is, a line drawn through the center of the short axis of one pin to the center of the short axis of the other pin is not perpendicular to longitudinal axis of the latch  36  when the latch is in the latched position. In some embodiments, the cross-section of the unlock pin  54  is larger than the cross-section of the lock guide pin  50 , as shown in  FIG. 2 . These differing dimensions facilitate the coordinated movement of the latch  36 , as configured in the figure, to the latched and unlatched positions, although other dimensions and latch arm configurations may be used. The pins  50 ,  54  and the latch  36  are preferably made from nickel-plated steel to improve their durability to wear from any engagement that may occur during the movement of the latch  36 .  
         [0019]     The cam is primarily circular in shape with a mounting collar  72  located at its center. The mounting collar  72  typically has a D-shaped opening to mount the D-shaped output shaft of typical Oven Door Lock motors, although other shapes may be used for the motor output shaft and cam mounting collar. The cam is preferably formed from a plastic material, such as glass-filled nylon, although other materials may be used. On the side opposite the motor  44 , an offset hub  84  ( FIG. 3 ) is provided on the cam  40 . The offset hub is eccentrically located on the cam  40  to rotationally displace the latch  36  as the cam is rotated by the motor  44 .  
         [0020]     The top view of the mechanism  30 , shown in  FIG. 3 , demonstrates the position of the latch  36  at the latched (solid lines) and the unlatched (dashed lines) positions. The lock pin  50  and the unlock pin  54  are positioned on the plate so they are not diametrically opposed to one another across the latch  36 . The unlock pin  54  is positioned with respect to the two positions of the offset hub  84  shown in the figure so that the rounded curve of the latch  36  is proximate the unlock pin  54  when the latch  36  is at the fully unlatched position. The unlock pin  54  helps hold the latch  36  in the fully unlatched position as any force directed against the latch  36  to move it to the latch position causes the rounded curve to engage the unlock pin  54 , which blocks its further movement. The lock pin  50  is positioned with respect to the offset hub so that it encounters the rearward portion of the curve in the latch  36  as it begins to move from the unlatched to the latched position. This interaction positively moves the latch quickly to the straight position for latch pull-in so the reach of the latch  36  is maximized for engaging the oven door  12 . This interaction enables the oven lock mechanism  30  to be used effectively with the tolerances for the gaps typically encountered between an unlatched oven door  12  and its frame  14 . Also, at the fully latched condition, the lock pin  50  blocks movement of the front of the lock aperture  74  if a force is applied to the latch  36  to unlatch it from the door  12 .  
         [0021]     With further reference to  FIG. 3 , the mounting plate  32  has snap action switches  46  and  48  mounted to the plate. The rounded mounting end  70  of the latch  36  is mounted about the offset hub  84 . The mounting collar  72  of the cam  40  is mounted about the output shaft of the motor  44  and the motor  44  is mounted to the mounting brackets extending from the plate  32 . In this configuration, the cam  40  is positioned between the motor  44  and the latch  36  and the latch  36  is positioned between the cam  40  and the mounting plate  32 .  
         [0022]     The motor  44  and the cam  40  are located so that the perimeter of the cam  40  selectively interacts with the actuators of the snap action switches  46  and  48 . Specifically, the perimeter of the cam  40  includes a switch interface  88  ( FIG. 3 ). The interface has a slope  90  at one end and a drop-off  94  at the other end. The drop-off  94  enables spring-biased switch actuator  98  to extend fully from switch  48 . When the cam rotates in the clockwise direction, as viewed in  FIG. 3 , the slope  90  urges the actuator against its spring bias so the actuator is depressed into the switch  48 . The perimeter of the cam  40  continues to hold the actuator  98  in the depressed state until the drop-off  94  passes by the actuator  98  so it fully extends. The switch  48  is either a normally open or normally closed switch with the actuator  98  in the extended position. The state of the switch changes in response to the switch being depressed. Likewise, the switch  46  is a normally open or a normally closed switch with its actuator  100  in the extended position. When the actuator  100  is depressed, as shown in  FIG. 3 , the switch changes state. The states of the switches  46  and  48  may be monitored by a controller for the oven to determine when to couple and de-couple motor  44  to power.  
         [0023]     In one embodiment, the latch  36  has the shape depicted in  FIG. 3 . The latch  36  in that figure has a rounded mounting end  70  that leads into two parallel sides. The side facing the lock guide pin  50  includes a lock aperture  74  that is illustrated as being roughly circular, although other shapes are possible. This side of the latch continues into a straight line that terminates into the outside edge of the hook  78 . The side of the latch  36  that faces the unlock pin  54  curves inwardly to form neck  80  of the hook  78 . The rounded corner where the straight side transitions to a curve to form a neck is an unlock detent  76 . The mounting of the latch  36  to the offset hub  84  of the cam  40  and the placement of the pins  50  and  54  enables the latching and unlatching of the oven lock to occur with reciprocating motion of the latch  36 .  
         [0024]     In more detail, the lock mechanism  30  is installed in an oven so the mechanism is below the countertop and above the oven chamber. The lock mechanism is centered so the latch  36  extends through the opening  60  and can selectively engage with and disengage from the oven door. With the latch in the open position, shown with dashed lines in  FIG. 3 , the oven door opens and closes for normal use. In this position, the interface  88  is proximate the actuator  100  so the actuator  100  is fully extended. Also, the offset hub of the cam  40  is at the six o&#39;clock position with respect to its center. In response to the self-cleaning cycle being selected, an electrical circuit for powering the motor is closed so the motor  44  begins to rotate in the clockwise direction as shown in  FIG. 3 . Alternatively, selection of the self-cleaning cycle may change the state of a switch that is coupled to an oven controller so the controller closes a circuit and powers the motor. As the cam rotates, the slope  90  depresses the actuator  100  so the switch  46  changes state. This change in state indicates the cam is rotating.  
         [0025]     As the cam continues to rotate, it carries the latch  36  with it. As the latch  36  rotates, the lock aperture  74  of the latch  36  almost immediately encounters the lock guide pin  50 . This interaction quickly uprights the latch  36  so it is perpendicular to the opening  60  and is at its maximum extension for lock pull-in. This interaction and extension occurs within the first  30  degrees of the cam rotation. As the cam continues to rotate towards the 12 o&#39;clock position, the mounting end  70  of the latch  36  is pulled away from the oven door. The lock guide pin  50  remains in contact with the curved edge of the aperture  74  until the juncture of the aperture  74  and neck  80  is proximate the pin  50 . During this movement, the hook  78  of the latch  36  engages the oven door and pulls the door towards the oven frame. The pull-in motion continues until the offset hub reaches the 12 o&#39;clock position.  
         [0026]     As shown in  FIG. 3 , the interface  88  is proximate the actuator  98  when the offset hub is at the 12 o&#39;clock position and the actuator  98  fully extends. Upon extension, the state of the switch  48  changes to indicate the cam has rotated from the 6 o&#39;clock position to the 12 o&#39;clock position. In response to this state change, the electrical circuit powering the motor  44  is opened and the motor is decoupled from power so the cam stops rotation and the oven remains locked. Alternatively, the state change in the switch may be detected by an oven controller that decouples the motor from electrical power.  
         [0027]     Upon completion of the self-cleaning cycle, the electrical circuit for powering the motor is closed so the motor  44  begins to rotate in the clockwise direction again. Alternatively, deactivation of the self-cleaning cycle may change the state of a switch that is coupled to an oven controller so the controller closes the circuit and powers the motor so it begins rotating in the clockwise direction. As the cam rotates in the clockwise direction, the slope  90  depresses the actuator  98  to indicate the cam has begun rotation. As the offset hub of the cam moves clockwise from the 12 o&#39;clock position, the mounting end  70  of the latch  36  moves the latch  36  forward. The lock aperture  74  acts as a clearance with respect to lock pin  50  to facilitate the unlatching motion. As the cam rotation continues, the movement of the latch  36  causes the unlock detent  76  to engage the unlock pin  54  to rotate the latch  36  so that the neck  80  is stopped by the outside edge of the opening  60 . In this position, the hook  78  is fully released from engagement with the oven door. After the cam has completed its 180 degree rotation, the switch interface  88  causes the actuator  100  to extend and the motor  44  is decoupled from power so the cam rotation stops. Once again, the user of the oven is able to open and close the door freely. The latch  36  remains in the unlatched position because any force pushing the latch  36  away from the outside edge of the opening  60  causes the unlock detent  76  to be blocked by the unlock pin  54 .  
         [0028]     In another embodiment, a latch  300 , shown in  FIG. 4 , is used with the unlock pin  308  and lock pin  310 . In this embodiment, the latch  300  is coupled to the offset hub of the cam  40  with a cradle and pin configuration. The pins  308  and  310  are staggered as explained above, but they are positioned so they are tangential to the parallel sides of the latch  300  when the latch  300  is perpendicular to the oven door. The pins  308  and  310  also have cross-sectional areas that are approximately equal to one another. The latch  300  includes a lock aperture  318  and an unlock aperture  320 . The unlock detent  318  and the lock aperture  320  parallel one another and are positioned on the sides of the latch  300  at approximately the same distance from the mounting end  70  of the latch  300 . In the embodiment shown in  FIG. 4 , the unlock detent is a protuberance that extends from the latch  300  and the lock aperture is a hollow in the opposing side of the latch  300 , although other shapes and configurations may be used.  
         [0029]     The action of the latch  300  is now described with reference to  FIGS. 5A through 5E . At the pulled-in and locked position ( FIG. 5A ), the pins  308  and  310  are adjacent the parallel sides of the latch  300  and are forward of the unlock detent  318  and the lock aperture  320 . In response to the motor commencing its rotation, the latch  300  begins to move forward to a position where the unlock pin  308  begins to interact with the unlock detent  318  ( FIG. 5B ). This interaction urges the latch  300  towards the lock pin  310 . This urging continues until the lock pin engages the lowest point in the lock aperture  320  and the unlock pin  308  is at the top of the unlock detent  318  ( FIG. 5C ). At this position, the latch is fully open and the edge of the opening  60  stops the movement of the latch  36 . Also, the cam interface  88  interacts with the actuators of the snap action switches to indicate the position has been reached and the motor stops rotating.  
         [0030]     Upon selection of a self-cleaning cycle, the motor and cam begin to rotate so the latch  300  is pulled away from the oven door. As the latch  300  is pulled from the door, the lock pin  310  begins to interact with the lock aperture  320  to turn the latch  300  so it is perpendicular to the door ( FIG. 5D ). As the latch continues to be pulled rearward by the rotation of the cam, the hook  78  engages the door and pulls it closed and latched ( FIG. 5E ). As the cam rotates past the actuator of the snap switch, as described above, power is decoupled from the motor and the cam rotation stops so the door remains locked until the self-cleaning cycle is complete.  
         [0031]     Although the oven door lock has been described in detail with reference to a certain illustrative embodiments, variations and modifications exist within the scope and spirit of the oven door lock as described and defined in the following claims.