An appliance door latch provides a rotating hook supported on a linear carriage that may move along a line toward and away from a strike. A release of the strike from the rotating hook requires a compression of springs biasing the linear carriage which are then retained in a compressed state by a catch surface on the rotating hook. Re-engagement of the strike with the rotating hook releases the catch surface, causing the springs to pull the rotating hook and strike inward to aid in compressing a door gasket or the like.

CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of provisional Patent Application 60/550,526 filed Mar. 5, 2004 hereby incorporated by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     --  
       BACKGROUND OF THE INVENTION  
       [0003]     The present invention relates to a latching mechanism for doors on household appliances and particularly to latching mechanisms that provide assistance in compressing a door gasket or the like.  
         [0004]     Appliances such as dishwashers and front-loading washing machines may have an access door with a gasket that must be compressed to seal water within a washing chamber. Small area, highly compliant gaskets may be sealed by pressure from the user during the closing the door. The gasket may then be held in a compressed state by a latch mechanism.  
         [0005]     Gaskets which require more force may be compressed by a latch mechanism having a lever operated by the user to engage a catch and draw the catch inward with a lever advantage to compress the gasket and hold the door shut.  
         [0006]     A closing lever may be avoided in latch mechanisms that provide an “over-center” spring mechanism. During initial stages of closing of the door, closing force on the door is used to energize a spring. When the door closes past the over-center point, the spring releases its energy in a manner to pull the door fully closed. An example an over-center spring mechanism is described in U.S. Pat. No. 4,497,513 to Sasaki.  
         [0007]     A variation on the over-center spring mechanism energizes the spring as the door is opened and holds that energy until the door is closed again. An over-center design is still employed and therefore a slight compression of the spring is required when the door is closed to release the energy. A latch of this kind is disclosed in U.S. Pat. No. 2,833,578 to Burke.  
         [0008]     U.S. Pat. No. 6,290,270 to Spiessl shows a variation on Burke in which the latch spring is energized when the door is opened and held in the energized state by the rotation of a cam. When the door is closed, the cam is rotated by a strike to release the energized spring. This design reduces the force required to close the door by eliminating the need to compress an over-center spring mechanism during door closure.  
         [0009]     In this latter design, the cam is held on a lever, and the energized spring moves the lever and cam. The spring engages the lever “outboard” of the cam to produce the necessary force over the needed distance with a manageable spring size. The lever in this design provides for a relatively narrow latch but increases the required height of the latch because of the necessary length of the lever and the outboard position of the spring. The lever is subject to significant bending forces making it difficult to implement the lever using injection molded thermoplastic, a material that is otherwise desirable in this application.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     The present invention provides a latch in which a locking cam is held on a carriage that slides linearly, preferably under the force of a series of balanced springs. By eliminating the need for a lever subject to high bending forces, the present invention provides a more compact design that may be readily implemented with injection-molded parts.  
         [0011]     Specifically then, the present invention provides an appliance latch for retaining a strike and having a latch frame affixable to a portion of the appliance, for example, the door or appliance housing. A carriage slideably held by the latch frame moves along a line substantially parallel to an axis along which the latch receives the strike. At least one spring biases the carriage along this line in the direction from which the latch receives the strike. A rotating hook is supported by the carriage to move with the carriage and to rotate about an axis perpendicular to the line. The rotating hook rotates to capture a portion of the strike in a capture position when the strike enters the hook opening, and rotates to release the strike in a release position when the strike exits the hook opening. A catch holds the carriage in a first position along the line with the spring in a high state of compression when the rotating hook is in the release position and releases the carriage in a second position along the line with the spring in a lower state of compression when the rotating hook is in the capture position. In this way, energy stored in the spring when opening the latch is returned to aid in closing the latch.  
         [0012]     It is thus one object of at least one embodiment of the invention to provide a low closing force, gasket-compressing latch in a compact mechanism.  
         [0013]     Multiple compression springs may bias the carriage in a direction along which the latch receives the strike.  
         [0014]     It is thus another object of at least one embodiment of the invention to distribute the force required for compression of the gasket among multiple springs, to reduce bending forces on the carriage and to simply manufacturing.  
         [0015]     The multiple compression springs may be place symmetrically about the rotating hook, for example, at the corners of a rectangle surrounding the rotating hook.  
         [0016]     Thus it is another object of at least one embodiment of the invention to allow the springs to placed close to the hook to reduce shear on the carriage, facilitating the manufacture of the carriage from thermoplastic to provide reduced manufacturing cost, weight, and noise, and improved lubricity and resistance to water.  
         [0017]     The carriage may slide on rails fixed with respect to the latch frame and the compression springs may symmetrically flank each rail.  
         [0018]     Thus it is another object of at least one embodiment of the invention to provide a simple method of balancing the forces on the carriage to reduce binding.  
         [0019]     The rotating hook may include a cam surface compressed by the spring against a stop fixed with respect to the latch frame and the cam surface may have a high radius portion holding the carriage in the first position when the rotating hook is in the release position and the low radius portion releasing the carriage to a second position along the line with the spring in a lower state of compression when the rotating hook is in the capture position.  
         [0020]     It is thus another object of at least one embodiment of the invention to provide a simple mechanism for releasing the spring energy when the door is closed with minimal closing force.  
         [0021]     The stop may be a rod extending between the rails along which the carriage slides.  
         [0022]     Thus it is another object of at least one embodiment of the invention to align the force of the stop with the slides of the carriage to reduce binding and to provide dual use for the rails which both hold the stop and support the carriage for sliding.  
         [0023]     The appliance latch may further include a lock having a locked and unlocked state, the lock preventing the strike from exiting the latch when the lock is in the locked state.  
         [0024]     Thus, it is another object of at least one embodiment of the invention to provide the ability to lock the door from opening at certain times, for example, for safety purposes.  
         [0025]     The lock, in the locked state, may position a blocking member between the strike and structure fixed with respect to the latch frame so that a disengaging force on the strike does not place substantial force on the rotating hook or carriage.  
         [0026]     It is thus another object of at least one embodiment of the invention to provide a lock that shields the hook and carriage from potentially high disengaging forces allowing both to be constructed from thermoplastics.  
         [0027]     The lock may include a lock stop preventing the lock from moving to the locked state when the strike has not engaged the hook. The lock stop, for example, may be attached to the carriage to interfere with a sliding lock bar of the lock when the carriage is in a first position and the lock stop may be spring loaded to allow some movement of the carriage under forces from the strike when the carriage is in the first position and the lock is in the locked state.  
         [0028]     Thus it is another object of at least one embodiment of the invention to provide a lock that cannot be inadvertently activated when the door of the appliance is not fully closed and which may be simply incorporated into the linear carriage.  
         [0029]     A spring may be incorporated into the latch to bias the rotating hook toward the release position.  
         [0030]     It is thus another object of at least one embodiment of the invention to ensure that the rotating hook is properly positioned to receive the latch in the event frictional contact is lost between the rotating hook and the stop with jarring or vibration.  
         [0031]     The spring may be a leaf spring pressing against a surface of the rotating hook.  
         [0032]     It is thus another object of at least one embodiment of the invention to avoid the need for torsion springs that can be difficult to position in manufacturing.  
         [0033]     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]      FIG. 1  is a perspective view of the principal components of the latch of the present invention providing a linear carriage (abstracted for clarity) biased on springs and supporting a rotating hook abutting a stop to engage a strike;  
         [0035]      FIG. 2  is a cross-sectional view along line  2 -- 2  of  FIG. 1  showing the components of  FIG. 1  assembled on the linear carriage in a first position with springs in a high state of compression and the rotating hook in the release position prior to receiving the strike;  
         [0036]      FIG. 3  is a figure similar to that of  FIG. 2  showing the carriage in a second position with the springs in a lower state of compression and the rotating hook in the capture position;  
         [0037]      FIG. 4  is a view of the rotating hook showing its cam surfaces;  
         [0038]      FIG. 5  is a front elevational view of the lock mechanism that may be used with the latch of the present invention showing electrical connections to a door close switch, a locking state switch and a bi-directional actuator; and  
         [0039]      FIGS. 6 and 7  are fragmentary side views of the stop of  FIG. 5  showing the spring-loaded plunger providing a lock stop preventing locking when the linear carriage is in the first position.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0040]     Referring now to  FIG. 1 , an appliance latch  10  of the present invention works with a strike  12 , in this case, a U-shaped rod having a laterally extending strike bar  14 . The strike  12 , may be attached to a first portion  15  of an appliance, for example the appliance door, to be received by the appliance latch  10  attached to a second portion  17  of the appliance, for example, the appliance housing against which the door is closed.  
         [0041]     The strike bar  14  of the strike  12  may engage a hook opening  16  of a rotating hook  18 . The rotating hook  18  rotates on axle  27  about an axis  25  generally perpendicular to axis  20  and may receive the strike along an axis  20  in a direction  22 .  
         [0042]     The rotating hook  18  is mounted to a linear carriage  24  of the appliance latch  10 . The linear carriage  24  is supported on a plurality of springs  26  to move in a line substantially along axis  20 . The springs  26 , which may be helical compression springs, urge the linear carriage  24  along direction  22 .  
         [0043]     A stop  28  is positioned behind the rotating hook  18  with respect to the strike  12  and may be a laterally extending metal bar generally perpendicular to axis  20 . The stop  28  limits translative motion of the rotating hook  18  in direction  22  through interference between the stop  28  and cam surfaces  34  at the radial outer periphery of the rotating hook  18 . The stop  28  may also prevent rotation of the rotating hook  18  under certain circumstances to be described below.  
         [0044]     The stop  28  is held fixed by a pair of rails  30  (only one shown in  FIG. 1 ) with respect to a latch frame  32  attached to the second portion  17  of the appliance. The rails  30  also provide a sliding support for the linear carriage  24 .  
         [0045]     Referring momentarily to  FIG. 5 , the rotating hook  18  may be positioned approximately in the center of the linear carriage  24  and the springs  26  placed at comers of a rectangle circumscribing the rotating hook and symmetrically flanking about the axis of the rotating hook  18  and the rails  30  on which the linear carriage  24  rides to eliminate problems of binding or the like.  
         [0046]     Referring now to  FIGS. 2 and 4 , before the rotating hook  18  has fully received the strike  12 , the linear carriage  24  will be in a first state with springs  26  highly compressed and the linear carriage  24  moved fully forward in a direction opposite direction  22 . The linear carriage  24  is and held in this position with the springs  26  fully compressed by contact of a high-radius cam surface  34   a  of the rotating hook  18  with the stop  28  held by the rail  30 .  
         [0047]     When strike bar  14  of the strike  12  engages the hook opening  16  it causes a counterclockwise rotation  23  of the rotating hook  18  about axis  25 . This causes high-radius cam surface  34   a  to move away from stop  28  to be replaced by low-radius cam surface  34   b . Low-radius cam surface  34   b  allows the rotating hook  18  to move in direction  22  under the urging of the springs  26 . The backward movement of the rotating hook  18  draws along with it the strike  12  pulling the first portion  15  and second portion  17  of the appliance (shown in  FIG. 1 ) about a gasket  35 .  
         [0048]     The springs  26  are sized to compress the gasket  35  into a sealing condition. Resistance of the gasket  35  to compression causes the rotating hook  18  to experience a clockwise force as the rotating hook  18  pulls against the strike  12 . Referring to  FIGS. 3 and 4 , this clockwise force on the rotating hook  18  is resisted by a radially-extending cam surface  34   c  positioned between the high-radius cam surface  34   a  and the low-radius cam surface  34   b  which blocks clockwise motion of the rotating hook  18  once the linear carriage  24  has moved along direction  22  away from its first position.  
         [0049]     Referring now to  FIGS. 1 , and  3 , when the linear carriage  24  has fully moved backwards in direction  22 , into a second position with the springs  26  extended in a lower state of compression, the gasket  35  will be compressed into a sealed state and at equilibrium with springs  26 .  
         [0050]     When it is desired to open the door, a force may be applied to the strike  12  in a direction opposite direction  22 . Initially, this force draws the rotating hook  18  and the linear carriage  24  forward without rotation of the rotating hook  18  compressing springs  26 . Rotation of the rotating hook  18  is prevented by interference between stop  28  and radially-extending cam surface  34   c.    
         [0051]     When the linear carriage  24  is pulled fully forward, the radially extending cam surface  34  moves beyond the stop  28  and the rotating hook  18  is free to rotate in a clockwise direction, releasing the strike  12 . Rotation of the rotating hook  18  brings high-radius cam surface  34   a  back into contact with the stop  28  holding the linear carriage  24  inward by means of interfitting of stop  28  and high-radius cam surface  34   a.    
         [0052]     Referring again to  FIGS. 2 through 4 , generally free rotation of the rotating hook  18 , absent force from the strike  12 , is prevented by frictional contact between the stop  28  and the high-radius cam surface  34   a  or low-radius cam surface  34   b . Optionally, however, a restoring clockwise torque may be exerted on the hook  18  by a leaf spring  42  to ensure that the rotating hook  18  stays a fully clockwise position with jarring or vibration. The leaf spring  42  has one end attached to the linear carriage  24  and the other end pressing radially inward against a spiral cam surface  44  so that the inward pressing of the leaf spring  42  provides a slight clockwise bias to the rotating hook  18  preventing it from being misaligned during closing of the appliance door per  FIG. 2 . The end of the leaf spring  42  attached to the linear carriage  24  may have a hook end  46  allowing it to be snapped in place onto the linear carriage  24  after assembly of the rotating hook  18  to the linear carriage  24 . This design eliminates the need to install a torsion spring in compression around the axle  27  of the rotating hook  18  such as may prove difficult in manufacture.  
         [0053]     Referring now to  FIG. 1 , at times it may be desirable to prevent an opening of the appliance door simply by pulling on the door and accordingly, the present invention provides for lock  48  providing a bolt  50  shown in  FIGS. 1, 2  and  3  that may move between the latch frame  32  and the strike bar  14  when the appliance latch  10  is closed with the linear carriage  24  in the second position holding the door shut. Opening force (opposite direction  22 ) on the strike  12  pulls a lower lip  52  of the opening  16  of the hook  18  against the bolt  50  so that the rearward flat surface of the bolt  50  abuts a flat cam surface  54  of the lower lip  52 . Force on the rotating hook  18  by the strike  12  pulls the flat surface of the lower lip  52  against the flat surface of the bolt  50  so that the lower lip  52  is captured between strike bar  14  and bolt  50  with no net torque being exerted on the rotating hook  18  about axis  25 . Accordingly, the rotating hook  18  need not be able to withstand high shear forces exerted on the hook opening  16  by the strike bar  14 . Further, because force from the strike  12  is channeled into compression of the lower lip  52  excessive force is not applied to the linear carriage  24 . This permits the hook  18  and linear carriage  24  to be molded of common thermoplastic materials which provide high compression strength.  
         [0054]     The front surface of the bolt  50  away from the rotating hook  18  is fully supported by the latch frame  32  and ultimately the structure of the appliance housing or door on which the latch frame is mounted so that the bolt  50  also experiences primarily compressive as opposed to bending forces. For this reason, the bolt  50  may also be molded of common thermoplastic materials.  
         [0055]     Referring to  FIG. 5 , the bolt  50  may be attached to a slide  56  driven by a bi-directional solenoid  58  of type well-known in the art according to electrical signals provided to terminals  60 . The bi-directional solenoid may move the slide  56  to either of two lateral positions to push the bolt  50  leftward into position under the rotating hook  18  (per  FIG. 3 ) or to retract the bolt  50  rightward (as shown in  FIGS. 2 and 5 ).  
         [0056]     A pair of contacts  63  may communicate with the slide  56  to provide a signal through terminals  64  indicating that the bolt  50  is positioned to block the retraction of the strike  12  and a push button door closure switch  66  provides a signal that the door is closed through terminals  68 . Accordingly, a control circuit (not shown) attached to the terminals  60 ,  64  and  68  may enforce a sequence of operations of the appliance latch  10  allowing the bolt  50  to be moved leftward to lock the appliance latch  10  only when the door is closed as indicated by switch  66  and to allow starting of the appliance only after confirmation of that locking has occurred per contacts  63 .  
         [0057]     Referring to  FIGS. 5 and 6 , the slide  56  may include a projection  72  extending from the slide  56  in a direction perpendicular to the slide that may engage a spring-loaded lock stop  70  to prevent locking of the appliance latch  10  when the linear carriage  24  has not fully retracted to the second position. When the linear carriage  24  is in the first position, as shown in  FIG. 6 , with the springs  26  in a high state of compression, the lock stop  70  interferes with movement of the slide  56  leftward to a locking position by interference between projection  72  and the lock stop  70 . When the linear carriage  24  moves to the second position, as shown in  FIG. 7 , the lock stop  70  also moves upward allowing passage of projection  72  and leftward movement of the slide  56 .  
         [0058]     As shown in  FIG. 7 , when the slide  56  is in the leftward position and thus the appliance latch  10  is locked, the linear carriage  24  may be moved slightly by an attempted opening of the door. The lock stop  70  is spring loaded so as to retract slightly in this case, against the projection  72 . The lock stop  70  prevents the appliance latch  10  from being activated when the appliance latch  10  is not fully engaged and yet allows the linear carriage  24  to move slightly within a predefined range when it is in a locked condition.  
         [0059]     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.