Patent Abstract:
A door latch for an appliance provides a U-shaped spring for engaging a strike having an expanded tip and passing between the arms of the U-shaped spring in a direction substantially perpendicular to the extent of those arms. Locking of the latch may be provided by collaring the distal ends of the arms to prevent their expansion once the strike is engaged.

Full Description:
RELATED APPLICATIONS 
     This application is based on International Application No. PCT/US 2011/032406, filed Apr. 14, 2011 and claims the benefit of U.S. provisional application 61/327,945, filed Apr. 26, 2010. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an appliance latch and in particular to a latch assembly retaining door closure in the event of a fire in the dryer. 
     BACKGROUND OF THE INVENTION 
     Clothes dryers may employ a rotating perforated drum into which clothes are placed and tumbled within circulation of heated air to dry the clothes. The drum may be accessible for loading and removing clothing through an opening in the front of the dryer cabinet that may be covered by a hinged door when the dryer is in use. Typically, the door is held closed by a spring latch that retains the door closed against the light force of tumbling clothing but that may be readily opened at any time by a higher force applied to the dryer door handle by the user. 
     In some situations, it may be desirable to provide a latch that will maintain the door in the closed position under elevated temperatures that may melt plastic components. In this way, in the event of a fire in the interior of the dryer, the door will remain closed confining the fire to the interior. 
     One such latch is described in US patent application 2009/0260198, assigned to the assignee of the present invention and hereby incorporated by reference, which discloses a strike having a bulbous tip that may be received between plastic jaws of a spring clip. The plastic jaws are biased by a metallic U-shaped spring having arms that open by deflecting or pivoting about an axis generally perpendicular to the motion of the strike. The arms of a metallic spring pass through the plastic jaws so that should the plastic jaws melt, the ends of the arms are nevertheless close enough to the strike to grip and retain the strike when the plastic jaws are gone. The plastic jaws, during normal operation, reduce the friction of engagement and disengagement of the latch with the strike. 
     A U-shaped spring holding the plastic jaws is attached at its base to a metal U-shaped bracket surrounding the U-shaped spring having legs extending forward to attach to the housing of the dryer behind an opening through which the strike would make pass. This metal U-shaped bracket holds the U-shaped spring in proper position even in the event of a fire. 
     SUMMARY OF THE INVENTION 
     The present invention provides a latch for a clothes dryers or the like in which the U-shaped spring of the prior art is rotated by 90 degrees so that the arms of the U-shaped spring clip pivot about axes generally parallel to the motion of the strike and the arms of the U-shaped spring clip extend across the strike and the opening. This configuration permits elimination of the U-shaped bracket permitting instead a simple plastic support because the U-shaped spring clip has an orientation that may retain itself on the strike and block retraction of the strike even in the absence of the support bracket. This orientation further permits greater flexibility in controlling the spring clip force constant in a shallow form factor. Finally, this orientation permits locking of the strike to be simply accomplished by collaring the ends of the U-shaped spring clip, these ends being displaced from and thus free from interference with the strike itself. 
     Specifically the present invention provides a latch strike retention assembly adapted to accept and retain a latch strike and including a substantially “U” shaped spring having opposing and substantially parallel arm portions extending from a common base portion. A support bracket holds the U-shaped spring behind an opening through which the strike must pass so that the arm portions of the U-shaped spring extend generally perpendicular to a direction of strike engagement with the arm portions, and the arm portions may flexibly separate within a plane perpendicular to the direction of latch engagement to receive and restrain the strike therebetween. 
     It is thus a feature of at least one embodiment of the invention to provide a latch with a shallow form factor. It is a further feature of this embodiment to permit use of a simple support bracket which may be in its simplest form a thin plate which does not require high-strength materials for proper support of the U-shaped spring. 
     The support bracket may be a thermoplastic material. 
     It is thus a feature of at least one embodiment of the invention to provide a design permitting a readily manufacturable injection molded support bracket while still ensuring that the door will remain latched at elevated temperatures that might melt or burn plastic. By sizing the U-shaped spring to be larger than the aperture and orienting the U-shaped spring across the aperture, retention of the strike may be maintained even without the support bracket. 
     The support bracket may include apertures receiving arm portions of the U-shaped spring when the arm portions are inserted into the apertures along the plane and may include a snap element capturing the based portion of the U-shaped spring against extraction from the apertures along the plane after insertion of the arm portions into the apertures past the snap element. 
     It is thus a feature of at least one embodiment of the invention to retain the elements of the latch together for easy manufacture while permitting necessary motion of the U-shaped spring. 
     The U-shaped spring is a single rod of substantially circular cross-section. 
     It is thus a feature of at least one embodiment of the invention to provide an extremely simple wire-form latch element whose orientation permits the necessary flexibility to be obtained in an arbitrary wire size. It is another feature of at least one embodiment of the invention to provide an outer surface of the U-shaped spring conducive to smooth engagement with a tapered strike. 
     The arm portions of the U-shaped spring distal to a point of engagement with the strike may have an un-flexed separation smaller than a corresponding thickness of the strike between the arm portions when the strike is engaged with the U-shaped spring, and/or the arm portions of the U-shaped spring at a point of engagement with the strike may have an un-flexed separation smaller than a corresponding thickness of the strike at the point of engagement. 
     It is thus a feature of at least one embodiment of the invention to ensure that the U-shaped spring is retained on the strike even in the absence of the support plate. 
     The U-shaped spring may extend at least three times the width of the base portion measured perpendicularly to the extent of the arm portions. 
     It is thus a feature of at least one embodiment of the invention to provide a substantially parallel separation of the arm portions of the U-shaped spring for robust engagement with the strike. It is another feature of at least one embodiment of the invention to permit engagement of the strike at a variety of positions along the U-shaped spring to accommodate vertical strike movement resulting from manufacturing tolerances and/or door hinge sag. 
     The latch strike may further include a collar movable relative to the U-shaped spring between: (a) a first locked position at least partially surrounding the arm portions of the U-shaped spring preventing separation of the arm portions to release the strike after the strike has passed through the U-shaped spring, and (b) a second unlocked position removed from the arm portions of the U-shaped spring permitting separation of the arm portions to release the strike after the strike has passed through the U-shaped spring. 
     It is thus a feature of at least one embodiment of the invention to provide a latch permitting simple addition of a locking function. 
     The U-shaped spring may be held substantially fixed with respect to the support bracket and the collar is movable with respect to the support bracket. 
     It is thus a feature of at least one embodiment of the invention to permit a locking during engagement of the latch and strike such as may impart a high frictional resistance to movement of the U-shaped spring. 
     The latch strike retention assembly may further include an electrically powered actuator moving the collar with respect to the support bracket between the locked and unlocked position in response to an electrical signal. 
     It is thus a feature of at least one embodiment of the invention to permit automatic locking of the door at certain appliance operating stages. 
     The actuator may be at least one electrical solenoid and/or may include a thermal actuator preventing movement of the collar from the locked to the unlocked position when power is disconnected from the electrical solenoid for a predetermined period of time corresponding to a thermal cooling. 
     It is thus a feature of at least one embodiment of the invention to permit rapid locking action as may be necessary for certain safety features while ensuring residual locking even under power loss conditions that nevertheless ultimately permit access through an unlocked door. 
     The latch strike retention may further include a strike sensor communicating with a first contact set to provide a signal dependent on engagement of the strike with the U-shaped spring. 
     It is thus a feature of at least one embodiment of the invention to permit determination of proper door position for locking. 
     The collar may further communicate with the first contacts to provide a signal dependent on engagement of the collar with the arm portions of the U-shaped spring. 
     It is thus a feature of at least one embodiment of the invention to permit a single signal to be used for effective lock control. By providing a signal only when the strike is in position and the collar properly placed, door closure can be detected by momentary operation of the electronic actuator and monitoring of the contacts, and complete locking may be confirmed by closure of the contacts. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a typical clothes dryer such as may employ the present invention showing locations of the strike and latch mechanism, the latter behind a front panel of the dryer; 
         FIG. 2  is an exploded fragmentary diagram of the latch mechanism positioned behind an opening in the front panel of the dryer, the latch mechanism including a plastic retainer element and U-shaped spring clip such as may receive a bulbous tip of a strike; 
         FIGS. 3 a - c    are front elevational, fragmentary side elevational and fragmentary top plan views of the strike engaged with the latch mechanism of  FIG. 2  showing blocking of the strike from retraction through the opening in the cabinet even without the plastic retainer element; 
         FIG. 4  is an orthogonal view of the rear of the latching mechanism of  FIG. 2  as assembled showing the retention of the U-shaped spring clip beneath bridges formed in the plastic retainer element as retained by a snap ramp; 
         FIGS. 5 and 6  are top plan views of the ends of the U-shaped spring clip in an embodiment where the ends may be moved out of a normal plane of the U-shaped spring clip within walls of a collar to prevent them from separating such as would permit release of the strike to provide a locking action; 
         FIGS. 7 a  and 7 b    are front elevational views of the U-shaped spring clip in an embodiment in which the spring clip is moved along the plane by an electric actuator to place the ends in between the walls of a collar to provide a locking; 
         FIGS. 8 a  and 8 b    are figures similar to those of  FIGS. 7 a  and 7 b    showing a movable collar for providing a locking action. 
     
    
    
     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to  FIG. 1 , an appliance  10 , such as the dryer, may provide for a housing  12  generally constructed of enameled steel or the like. The housing  12  may have a front panel  14  providing a drum access opening  16  leading to the dryer drum for the insertion and removal of clothes therethrough. The drum access opening  16  may be covered during use of the appliance  10  by a hinged door  18  having a door strike  20  attached to an outer edge of the rear of the door  18  to extend rearward therefrom. The door strike  20  may be received through a latch opening  22  in the front panel  14  to be retained by a latch mechanism (not shown in  FIG. 1 ) as will be described. 
     Referring now to  FIG. 2 , the strike  20  may extend generally along an axis  24  that also describes the local motion of the strike  20  as the door  18  is closed. The leading edge of the strike  20  as the door  18  is closed, and as is positioned toward the latch opening  22 , provides a bulbous end  26  that permits its retention by the strike retention mechanism  28  behind the latch opening  22 . 
     The strike retention mechanism  28  may include a U-shaped spring  32  and a support bracket  30  constructed of injection-molded thermoplastic. The U-shaped spring  32  provides two upwardly extending arms  36  formed by bending a round cross-section of steel wire in a U-shape until the arms  36  are substantially parallel as extending away from a base  39 . During use, as will be described, arms  36  may flex to pivot apart about an approximate pivot axis  38  parallel to but displaced from the axis  24  and in a plane  31  generally perpendicular to the axis  24  to admit the bulbous end  26  of the strike  20 . 
     The U-shaped spring  32  is retained in proper position to receive the strike  20  as corralled by the support bracket  30  which includes an escutcheon panel  40  abutting a rear surface of the front panel  14 . The escutcheon panel  40  includes an escutcheon aperture  42  allowing the strike  20  to pass through the escutcheon panel  40  to be received between the arms  36  of the U-shaped spring  32 . The escutcheon aperture  42  is surrounded by a collar  44  which has an outer periphery fitting snugly into the latch opening  22  of the front panel  14  and a beveled interior periphery helping to funnel the strike  20  into alignment with the escutcheon aperture  42 . The escutcheon panel  40  may be held against the front panel  14  by means of one or more screws  46  (only one shown for clarity) received by corresponding bores  48  in the escutcheon panel  40 . 
     Referring now to  FIG. 4 , the base  39  of the U-shaped spring  32  may fit around a boss  50  extending rearwardly from a rear surface of the escutcheon panel  40  about bores  48  beneath the escutcheon aperture  42 . The arms  36  of the U-shaped spring  32  may then extend upward toward a second boss  52  extending rearwardly from a rear surface of the escutcheon panel  40  about a second bore  48  above the escutcheon aperture  42 . The bosses  50  and  52  provide a surface for thread engagement by the screws  46  (shown in  FIG. 2 ). The arms  36  may be retained by molded bridge elements  54  on the rear surface of the escutcheon panel  40  having internal apertures  56  through which the arms  36  may pass while still providing for their ability to flex outward to receive the strike  20  through the escutcheon aperture  42 . The U-shaped spring  32  may be retained against removal from the apertures  56  by a snap element  51 . The snap element  51  provides a ramp surface assisting in sliding the U-shaped spring  32  into the apertures  35  along the plane, but a blocking surface preventing the reverse motion. 
     Referring now to  FIGS. 3 a - c   , the strike  20  may engage the U-shaped spring  32  after the bulbous end  26  of the strike  20  passes through an engagement plane  31  in which the arms  36  of the U-shaped spring  32  lie. The arms  36  of the U-shaped spring  32  will generally be parallel to each other for a height  60  suitable to accommodate different elevational positions of the strike  20  as may result from a sagging of the door  18  over time. The distal ends  62  of the arms  36  removed from the base  39  of the U-shaped spring  32  may be bent inward toward each other to have a reduced separation  66  when the parallel portions of the arms  36  of the U-shaped spring  32  are relaxed less than the horizontal width of the strike  20  between the arms  36 . More generally, the relaxed separation of the arms  36  may be less than the horizontal width of the strike  20  between the arms  36 . In these ways, even in the absence of the support bracket  30 , for example when melted or deformed, the U-shaped spring  32  will retain its grip on the strike  20  and be in a position to prevent withdrawal of the strike  20  through the latch opening  22  without application of force sufficient to spread the arms  36  apart as would be required during normal latching operation. 
     Referring momentarily also to  FIG. 2 , the bulbous end  26  of the strike  20  may have its leading apex  25  displaced upward with respect to an axis of the shaft of the strike  20  reflecting a predominance of downward displacement of the strike  20  over time with door sag. Further, the escutcheon aperture  42  may have a peripheral bevel to assist in guiding the bulbous end  26  of the strike  20  into the escutcheon aperture  42 . 
     Referring now to  FIG. 5 , the strike retention mechanism  28  may also provide a locking function preventing engagement or disengagement of the strike  20 . This locking may be accomplished by preventing a separation of the distal ends  62  of the arms  36  after they have received the bulbous end  26  of the strike  20 . In one embodiment, this may be accomplished by means of a locking wedge  70  fixed on the support bracket  30  whose movement along the plane  31  across the distal ends  62  (as shown in  FIG. 6 ) presses the distal ends  62  of the U-shaped spring  32  downward out of the plane  31  into an upwardly facing C collar  72  that prevents separation of the arms  36  and thus disengagement of the strike  20 . The locking wedge  70  may be moved by an electrical solenoid or the like. 
     Referring now to  FIGS. 7 a  and 7 b   , in an alternative embodiment, the separation of the distal ends  62  of the arms  36  of the U-shaped spring  32 , indicated by arrows  73 , may be prevented by sliding of the U-shaped spring  32  with respect to the support bracket  30  into a collar  72 ′ fixed on the support bracket  30 . The sliding is along the plane  31  generally in the direction  75  of the extent of the arms  36 . In this embodiment, the reduced separation  66  portion of the arms  36  is not required and those arms  36  may be substantially straight. 
     Movement of the U-shaped spring  32  in this manner may be accomplished by an electric actuator  74  attached to the base  39 , directly or through a linkage or the like, to allow both electrically controlled unlocking and locking with opposite motions of the electric actuator  74 . The electric actuator  74  may be any of a variety of electric actuators including single solenoids with permanent magnet cores, a single solenoid with a spring bias, opposed dual solenoids with standard ferromagnetic cores, wax motors, and bimetallic elements, electric motors, or the like. 
     Referring now to  FIGS. 8 a  and 8 b   , in an alternative embodiment, the U-shaped spring  32  may remain stationary with respect to the support bracket  30  and a collar  72 ″ may be moved into engagement (as shown in  FIG. 8 a   ) or disengagement (as shown in  FIG. 8 b   ) about the distal ends  62  of the U-shaped spring  32 . The collar  72 ″ may be mounted on a lever arm  76  to pivot about a pivot point  78  of the support bracket  30  under the control of actuator  74 ′. The actuator  74 ′ may be attached to an extension  77  of lever arm  76  on an opposite side of the pivot point  78 . This extension  77  may be in turn attached to a switch linkage  80  by a slide/pivot connection  82 . Movement of the extension  77  moves the switch linkage  80  about a pivot point  81  so that its end  83  opposite slide/pivot connection  82  opens a set of contacts  84  when the collar  72 ″ is disengaged from the distal ends  62  (as shown in  FIG. 8 a   ). When the collar  72 ″ is engaged with the distal ends  62 , preventing their separation and locking an engaged strike  20 , the end  83  is displaced from the contacts  84  so as not to interfere with their closing. 
     This embodiment may also provide for a pivoting strike sensor  86  having a first end  88  positioned between the arms  36  and within the opening  22  as shown in  FIG. 8 a   . In this state, a second end  90  of the strike sensor  86  also engages the contacts  84  to hold them open independent of the end  83  of the switch linkage  80  when the strike  20  has not been received. As shown in  FIG. 8 b   , when the strike  20  is engaged it presses the end  88  of the strike sensor  86  away from the opening  22  causing the strike sensor  86  to pivot about a pivot point  100  displacing end  90  away from the contacts  84  so as not to prevent their closure. 
     The result is that the contacts  84  may close only when both the collar  72 ″ is engaged on the distal ends  62  locking the strike  20  into the strike retention mechanism  28  and the strike  20  is engaged by the U-shaped spring  32 . This approach provides reduced wiring for the communication of both lock state (indicating a locking of the strike retention mechanism  28 ) and door closure state (indicating engagement of the strike  20  with the U-shaped spring  32 ). 
     In one embodiment, (shown in  FIG. 8 b   ) unlocking motion of the collar  72 ″ after it has been engaged on the distal ends  62  of the arms  36  may be prevented by a stop  102  inserted in the path of the extension  77  (or on any connected linkage) that would be traversed during that unlocking motion. The stop  102  may be moved into position by a wax motor or bimetallic strip actuator  104  wired in parallel or series with actuator  74 ′, the latter which may be a fast acting solenoid. In this manner a fast locking may be obtained through the action of actuator  74 ′ (being one or more solenoids) after which time the stop  102  will be placed according to the thermal time constant of the actuator  104 . In the event of power loss, the stop  102  will retain lock of the strike retention mechanism  28  for a period of time required for cooling of the actuator  104  preventing, for example, premature access to the appliance while parts may be in motion. 
     Alternatively, the actuator  74 ′ may be used alone and may be a thermal actuator if a slow locking speed may be tolerated. 
     The present invention contemplates that the arms  36  of the U-shaped spring  32  may be coated with a friction reducing substance such as a thermoplastic or may incorporate rollers or the like at points of contact with the strike  20  for the similar purpose, and/or that the strike  20  may be thermoplastic or have a thermoplastic coating over a metal core for similar friction reduction. The U-shaped spring  32  need not in all embodiments be formed of a single metal rod, but may be formed from two wires that are welded together or otherwise attached. 
     Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “left”, “right”, “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence, or order unless clearly indicated by the context. 
     When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     Various features of the invention are set forth in the following claims. It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention.

Technology Classification (CPC): 4