Abstract:
A combination switch is provided for a high-speed oven, the oven having a door. The combination switch has a rotatable cam ( 40 ) that is rotated when the door of the oven is moved between a closed position and an open position. The cam ( 40 ) has at least one lobe ( 50, 52 ) for engaging at least one safety-switch ( 44, 46 ) for actuation by the at least one lobe of the cam as the cam rotates. The at least one safety switch controls operation of at least a portion of the oven. A locking latch ( 48 ) is selectively moveable between an engaged position, in which the latch engages the cam ( 40 ) to limit rotation of the cam and thereby prevent opening of the door, and a disengaged position, in which the latch ( 48 ) does not engage the cam ( 40 ) and thereby allows opening of the door.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is the United States national phase of International Application No. PCT/U.S.2006/043569 filed on Nov. 8, 2006 and published in English on May 18, 2007 as International Publication No. WO 2007/056489 A1, which application claims priority to U.S. Provisional Application No. 60/734,918 filed on Nov. 9, 2005, the contents of both of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention generally relates to oven switches and particularly relates to a simplified switch mechanism to allow for microwave oven safety switches and a self-cleaning switch to be integrated into a single switching device. 
     2. Description of Related Art 
     In self cleaning ovens, it is necessary to raise the temperature of the cooking cavity to a pyrolytic level, typically in the range of approximately 900° F., to convert to ash any by-products of the cooking process that remain in the oven. For safety reasons, the oven door must be locked during the self cleaning process, and this has typically been accomplished by using a self-standing, motorized latch mechanism featuring a link or hook mounted behind the oven door frame. When activated, the latch mechanism engages the oven door to lock the door in a closed position. The latching system is typically a single mechanism mounted at the center of the oven door and activated automatically when the self cleaning cycle is initiated. 
     In microwave ovens, safety regulations require a safety circuit consisting of three switches connected in a manner to protect the operator from exposure to microwave energy when the oven door is opened. The switches, described as primary, secondary and monitor switches, insure the oven door is completely closed before the microwave circuit is enabled. The primary and secondary switches will prevent the flow of electric current to the microwave source when the oven door is at least partially open. The switches are operated by components mounted on the oven door, and each of the primary and secondary switches must have a different actuator to ensure redundancy or operation. The monitor switch ensures that that the oven cannot produce microwave energy in the event of failure or tampering of the primary or secondary switches. These switches must be mounted such that only the proper actuator is capable of operating them and tampering or other means will not allow the oven to produce microwave energy. 
     A combination oven with a self-clean feature must be equipped with both a self-cleaning safety switch and microwave safety switches. As used herein the terms “combination oven” and “multi-energy-source oven” have the same meaning and refer to ovens wherein microwave energy and some other form of thermal energy is utilized. 
     Although great strides have been made in the area of switches for ovens, many shortcomings remain. 
     SUMMARY OF THE INVENTION 
     There is a need for an improved switch system for a combination oven incorporating microwave safety switches and a self-cleaning cycle switch. 
     Therefore it is an object of the present invention to provide an improved switch system for a combination oven incorporating microwave safety switches and a self-cleaning cycle switch. 
     A combination switch is provided for a high-speed oven, the oven having a door. The combination switch has a rotatable cam that is rotated when the door of the oven is moved between a closed position and an open position. The cam has at least one lobe for engaging at least one safety switch for actuation by the at least one lobe of the cam as the cam rotates. The at least one safety switch controls operation of at least a portion of the oven. A locking latch is selectively moveable between an engaged position, in which the latch engages the cam to limit rotation of the cam and thereby prevent opening of the door, and a disengaged position, in which the latch does not engage the cam and thereby allows opening of the door. 
     The present invention provides several advantages, including: (1) providing a combination microwave safety switch and self-cleaning latch; (2) providing a simplified combination switch; and (3) providing a tamper-resistant switch. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The novel features believed to be characteristic of the invention are set forth in the appended claims. However, the invention itself, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is an oblique view of multi-energy-source oven having a combination switch according to the present invention; 
         FIG. 2  is an oblique view of the combination switch of  FIG. 1 ; 
         FIG. 3  is an oblique bottom view of the combination switch of  FIG. 1 , the components of the switch being shown in an “oven door open” orientation; 
         FIG. 4  is an oblique bottom view of the combination switch of  FIG. 1 , the components of the switch being shown in an “oven door closed” orientation; 
         FIG. 5  is an oblique bottom view of the combination switch of  FIG. 1 , the components of the switch being shown in an “oven door closed, self clean latch engaged” orientation; 
         FIG. 6  is an oblique top view of the combination switch of  FIG. 1 , the components of the switch being shown in an “oven door closed, self-clean latch engaged” orientation; and 
         FIG. 7  is an oblique view of a portion of the combination switch of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is directed to a simplified, compact, cam-driven switch system incorporating microwave safety switches and a self cleaning locking mechanism. The system of the invention is particularly useful when used with high-speed cooking ovens that combine electrical heating (or other types of thermal energy), microwave heating, and air impingement, the combination of which ensures high heat-transfer coefficients for cooking food much more rapidly than conventional ovens utilizing a single heat source. Combination ovens may be capable of pyrolytic self-cleaning. Although the switch system of the invention is described herein as being used with an oven using electric heating and air impingement, the switch system may be used on combination ovens having other forms of air movement and other forms of thermal energy, and the invention is not limited to use with the type of oven shown in the described embodiment. 
       FIGS. 1 through 7  illustrate a preferred embodiment of a combination switch according to the present invention, with  FIG. 1  showing the switch of the invention being installed on an exemplary version of a multi-energy-source oven. Oven  20  comprises blower motors  22 , magnetrons  24 , oven door  26 , face  27 , oven door microwave choke  28 , front frame apertures  29 , cooking cavity  30 , left- and right-side door-mounted actuators  32 , and left- and right-side combination switches  34 . Each actuator  32  has a lock aperture  33  for engaging a portion of the corresponding combination switch  34 . Left-side switch  34  is visible in  FIG. 1 , and  FIG. 2  shows right-side switch  34  removed from oven  20 . 
     Referring to  FIGS. 3 through 5 , right-side combination switch  34  is shown from the bottom, and switch  34  comprises frame  35 , cam shaft  36 , cam stop  38 , cam  40 , spring  42 , microwave safety monitor switch  44 , microwave secondary switch  46 , and self-clean safety latch  48 . Right- and left-side switches  34  are similarly constructed and configured, but each switch  34  is generally a mirror image of the other switch  34 . Switch  46  on one combination switch  34  is the primary switch, and switch  46  on the other combination switch  34  is the secondary switch. One combination switch  34  will be described below, though it should be understood that the description applies equally to the other switch  34 . As described herein monitor switch  44  is utilized only on one side, the right side. On the left side, the monitor switch may be replaced by another switch, for example a switch to control a light within the oven cavity. 
     To ensure magnetrons  24  of oven  20  is prevented from operating while door  26  is not fully closed, cam  40  is shaped to be engaged by the corresponding actuator  32  on door  26  as door  26  is opened and closed. Cam  40  is rotatable about cam shaft  36 , and cam  40  comprises back lobe  50  and a secondary high lobe  52 , which are formed on the peripheral edge of cam  40 . Actuator  32  causes cam  40  to rotate about cam shaft  36 , and cam  40  actuates switches  44 ,  46  at selected positions of door  26 .  FIG. 3  illustrates the position of components in switch  34  just before oven door  26  begins to engage the components of switch  34  when closing. Actuators  32  enter oven front frame aperture  29  and pass through an aperture  54  in frame  35 . 
     As door  26  further closes, actuator  32  begins to engage cam engaging tooth  56  of cam  40 , causing rotation of cam  40  in a counter-clockwise direction (as viewed in the figure) about cam shaft  36 . This rotation causes back lobe  50  to engage arm  58  of monitor switch  44  for closing switch  44 . Further rotation of cam  40  to the position in  FIG. 4  causes cam engaging tooth  56  to enter lock aperture  33  of actuator  32 . Spring  42  is attached at one end to cam  40  at point  60 , and point  60  is located a radial distance from the center of rotation of cam  40 . The opposite end of spring  42  is attached to frame  35 . This ensures that spring pressure is applied to urge rotation of cam  40 , which applies force to actuators  32  for causing door  26  to pull tight against face  27 , thereby improving the performance of door choke  28 . Additionally the pulling action of spring  42  provides the operator assistance with door closure, and the length or spring rate of spring  42  may be adjusted to achieve the desired door tension. 
     As illustrated in  FIG. 5 , once cam  40  has been fully rotated, switch  44  is activated by back lobe  50  and switch  46  has been activated later in the rotation of cam  40  by high lobe  52 . Although switches  44 ,  46  have been illustrated as activated by lobes  50 ,  52 , other combinations of lobes and normally open or normally closed switches may be utilized and applicant intends to encompass within this description any other combination of switches that will accomplish the same purpose and not be limited by the description herein. 
     Referring to  FIGS. 5 through 7 , switch  34  also provides for a self-cleaning locking mechanism.  FIG. 6  further illustrates right-side combination switch  34  from the top, and switch  34  further comprises locking mechanism drive system  62 , locking mechanism switch  64 , and spring  66 .  FIG. 7  shows detail of drive system  62 , which also comprises a cam  68  driven in rotation by drive system  62 . Spring  66  is attached at one end to cam  68  at a radial distance from the center of rotation of cam  68 , and the opposite end of spring  66  is attached to self-clean safety latch  48 . As drive system  62  rotates cam  68 , spring  66  moves in and out pivot latch  48  about pivot point  74 . In addition, cam  68  has a lobe  70  for engaging arm  72  of switch  64  as cam  68  rotates. 
     In those instances when self-cleaning is desired, with oven door  26  closed, a signal is sent to locking mechanism switch  64 , thereby activating a motor in drive system  62 . This moves the free end of latch  48  into engagement with a notch  76  in cam  40  adjacent cam engaging tooth  56 . As such, door mounted actuators  32  are locked by cam  40  and will not allow oven door  26  to be opened.  FIG. 4  illustrates the orientation of cam  40  and switches  44 ,  46  when oven door  26  is closed and self-cleaning latch  48  is disengaged.  FIG. 5  illustrates the orientation of cam  40  and switches  44 ,  46  when oven door  26  is closed and self-cleaning latch  48  is engaged to prevent rotation of cam  40 . When the self-cleaning cycle is completed, drive system  62  rotates cam  68  to a position in which spring  66  pushes latch  48  out of engagement with notch  70 , allowing cam  40  to rotate, which allows door  26  to be opened. 
     As previously described, safety switches  44 ,  46  will be open and prevent electricity flowing to the microwave circuit when oven door  26  is open. Primary switch  46 , secondary switch  46  (on the other combination switch  34 ) and monitor switches  44  are utilized in a manner wherein the primary and secondary switches  46  are mounted on different portions of door  26  and thereby operated by different actuators. As illustrated in  FIG. 1 , mounting of combination switch  34  at oven door top left and top right prevents deformation (e.g. flexing) of door  26 . Illustrated in  FIG. 1  is mounting at the top right and top left of door  26 , although other mounting positions may be utilized and applicant intends to encompass within this description any mounting configuration that will accomplish the same result as the herein described orientation. As such, a left side combination switch  34  is utilized. As described above, left-side switch  34  is configured in the same manner as right-side switch  34  and houses the secondary microwave safety switch  46  and may also house additional switches, for example an oven light switch (not shown). Additionally, because cam  40  operates to engage safety switches  44 ,  46 , the switches may be stacked one on top of the other, thereby providing redundancy of switching mechanisms (e.g. two monitor switches, two primary and two secondary switches), reducing service calls, in those instances where one of the switches fails. In that situation, the second stacked switch would still function and allow the microwave circuit to operate. It should be noted that locating combination switches  34  behind face  27  minimizes tampering with switch  34 . It should also be noted that a solid pin may be substituted for spring  66  to connect cam  68  to latch  48 . Spring  66  allows for disengagement of self clean safety latch  48  in those instances wherein drive system mechanism  62  fails with latch  48  engaging notch  76  in cam  40 . 
     The present invention provides several advantages, including: (1) providing a combination microwave safety switch and self-cleaning latch; (2) providing a simplified combination switch; and (3) providing a tamper-resistant switch. 
     While the exemplary embodiments of the present invention have been shown and described, it will be understood that various changes and modifications to the foregoing embodiments may become apparent to those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, the invention is not limited to the embodiments disclosed, but rather by the appended claims and their equivalents.