Abstract:
A lever operated compression latch has an elongated, hook-ended pawl carrying a longitudinal slot, and is cam guided and pin rotated while translated to engage and withdraw from a keeper cup. The compound movement of the pawl includes a lateral translation towards the keeper cup while rotating there into, followed by a lateral withdrawal to exert a compression force between the latch body which is attached to a door and the keeper cup which is attached to a door frame. A series of interconnected links is operated by a lever handle to fold into one another to provide a compact envelope when the latch is closed and to expand outwardly to open the latch and disengage the pawl from the keeper when operated by the lever. Of this series of links, a pair of release links operates in contact with one another, and rotates on respective individual pivot points to extend outwardly from the latch envelope to engage a striker plate portion of the keeper cup. This striker engagement causes the release links to push the latch and the door from a sealing engagement with the keeper and door jamb for a short distance, prior to the latch and the door thereafter being fully opened. This striker engagement of the release links also causes the latch links to fold inwardly which rotates and translates the pawl into keeper engagement and compression. This operation is facilitated with a floating spring having one end operating as a pivot member. A detent engages one of the links to provide a physical indication to the handle lever between the hard closed position and the closed about to open position.

Description:
PRIOR APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 61/596,187, filed Feb. 7, 2012, and U.S. Provisional Application No. 61/596,571, filed Feb. 8, 2012, and U.S. Provisional Application No. 61/597,749, filed Feb. 11, 2012, which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to compression latches of the type used to latch gasket-lined doors or gasket-lined door jambs. Compression latches have been designed to secure gasketed doors, trunk lids, panels, covers, and other structures. Such compression latches require a pawl and a clamp or other member to compress a generally elastomeric gasket or O-ring when securing the door, trunk lid, panel, cover or other structure. 
     The take-up, i.e., the compression distance moved by the pawl, clamp, or other member, to pull a door against a door jamb establishes the degree of compression of the gasket and the sealing force thereof. The linear travel of a pull member, once a door makes contact with a cabinet, establishes the sealing force of the gasket. Gasketed enclosures are often found in industry. These can include computer and communications cabinets, electrical transformer enclosures, sterilizing and autoclave enclosures, incubation and artificial environment enclosures, cooling chambers and freezers, humidity and controlled environment chambers, and various types of ovens, among others. 
     Compression latches are generally manually operated. As such, they can be operated by a handle or a lever. Levers are found on latches where the compression forces required against a gasket are greater, or the length of travel of the pull is longer. However, compression latches are specifically adjusted or specifically designed or selected for the particular application and the particular environment in which they are used. Such particular application and particular environment can also dictate other operating features for a latch, such as the requirements for handle and door locking and position holding, as well as the proximity distance of the lock on a door to a door jamb when the pull of the latch begins to operate. 
     SUMMARY OF THE INVENTION 
     The present invention is designed to latch the door to an oven. Such an oven may be designed for many different purposes, such as a climate chamber, a drying oven, an annealing or tempering oven, or a food processing oven, among others. Each of these ovens has a gasket or seal which is compressed when the oven door is fully closed. Thus a compression latch operation is well suited for these structures. 
     The compression latch of the present invention is lever operated. This enables that a first latch unit can be mounted near the top of the oven door and a second latch unit can be mounted near the bottom of the door. A bar-type handle is attached to and vertically extends between the two latch levers. The vertical bar handle operates both levers and therefore both latches in unison. The latches engage respective striker-keepers mounted on the body of the oven. 
     It is important that the vertical bar have a specific fully closed position, a specific fully open position, and a discernable intermediate position where a technician knows the latch is still fully closed but about to start to open. This would assist in minimizing accidental openings allowing the escape of hot air and gases towards the technician. 
     When closing the door it is desirable that the latch pawl comes into contact with its striker/keeper at a specific distance before the door is fully closed. In this way, the further movement of the vertical bar and thereby the further movement of the respectively connected latch levers, contributes to the compressing forces each latch exerts on the door gasket. For example, the latch pawl can engage the striker/keeper when the door is 10-20 mm from being fully seated against the gasket. This would require a linear movement of a pawl/pull member slightly more than that distance in order to compress the gasket. 
     It is also desirable that the latch housing size be minimized so that the latch can be used with small ovens and/or relatively thin oven doors. An envelope size for the latch housing can be in the range of 40-70 cubic centimeters. An example might be about 33 millimeters long by about 85 millimeters wide by about 20 millimeters high. 
     It is further desirable that the handle lever of each latch, itself, has a stable locked state when the latch is in the fully open position, and that this locked state be released only when the door is pushed to the closed position with a manual force by a technician, wherein the locked state of the latch is released for the latch to move into a closing mode to engage the keeper/striker to lock and seal the door. 
     These are objectives that are realized in the latch design of the present invention that provides a compression operation from a small package which promotes user friendly smooth operation. The latch housing has a snap-in feature which minimizes the tooling and components needed for installation. The operation of the latch is effected by the movement of a lever handle from left to right and vice versa with an over center position indicator providing an indication when the latch is locked. A blocking feature inhibits the latch from being locked when the door is open. The design is such that a positive movement by a technician is needed to close the latch and to open it. 
     The latch includes a series of links which fold into one another resulting in a very small package when the latch is closed. In a closed position the footprint of the latch is essentially rectangular except for a housing mounting leg at one side and a snap-in clamp at the other side. 
     When manually operated, the handle lever rotates in a semi-circle, from a closed secure position, to a closed but about to engage to an open position (at the top of the arc), to beyond the top to an operational area of the semi-circle where the latch opens. 
     The latch utilizes a rectangular keeper/striker cup, mounted to the door jamb, having a pull engaging lip and a striker plate. An elongate lever, operated by the vertical handle, is mounted to a first pivot point for rotation. That pivot point holds a torsion spring which biases the lever to a closed position. 
     The lever is pinned to an elongate first link at one end of the link. The first link has a pivot point at about its mid-length for its rotation thereon. The other end of the link is pinned to a second link and pinned to a first end of an elongate pawl 
     The lever operated compression latch has an elongate, hook-ended pawl with a pawl body having a longitudinal slot. The pawl is cam guided, and pin rotated and translated, to engage with and withdraw from a keeper cup. A fixed position cam post rides within the pawl slot and controls the pawl lateral translation. This cam also defines a pivot point about which the pawl rotates. The compound movement of the pawl includes a lateral translation towards the keeper cup while rotating there into, followed by a lateral withdrawal to exert a compression force between the latch body which is attached to a door and the keeper cup which is attached to a door frame thereby compressing the gasket. 
     A series of interconnected links is operated by the lever handle to fold into one another to provide a compact envelope when the latch is closed. These links expand outwardly to open the latch and disengage the pawl from the keeper when operated by the lever movement to the open state. Of this series of links, a pair of release links operates in contact with one another, and rotates on respective individual pivot points to extend outwardly from the latch envelope to engage a striker plate portion of the keeper cup. This striker engagement causes the release links to push the latch and the door from a sealing engagement of the keeper and door jamb for a short distance, prior to the latch and the door thereafter being separated and fully opened. This short distance of movement prior to the open state is a safety measure. 
     The striker engagement of the release links also causes the latch links to fold inwardly, which rotates and translates the pawl into keeper engagement and compression. This operation is facilitated with a floating spring having one end operating as a pivot member. A detent engages one of the links to provide a physical indication to the handle lever between the hard closed position and the closed about to open position. 
     From the fully closed position, when the handle, i.e., lever rotates, the pawl becomes free to translate out of the latch towards the keeper cup and the release links push the latch away from the keeper cup. This releases the compression state. Then after a slight lag and a further rotation of the lever, the pawl rotates. The pawl rotation is about 75 degrees from the keeper engagement position to a position fully rotated from the keeper and into the latch housing. When the latch is fully open, the handle lever is positively held in the open position. When the latch is fully open, the release levers are in the fully outwardly extending position. The handle lever, itself, is only released from the fully open position when the release levers strike the striker plate of the keeper cup. This causes the first and second links to rotate which releases the handle for movement. 
     The first link has a finger on its handle lever engaging end which engages an indentation in the handle lever to hold it fixed in the open position. The release linkage rotation causes the first link to rotate out of the fixed holding engagement with the handle lever. 
     The operation of the latch pawl is such that when the pawl force is released from exerting force against a gasket, the pawl finger hook continues to overlap the pull engaging lip of the striker cup. The handle when the pawl is in this position is held in a detent movement inhibited position which must be overcome by an additional force. This additional force overcomes the detent and moves the drive links, i.e., the first and second links connected to the pawl. The further movement of these drive links rotates the pawl to clear the finger hook from the striker cup and then rotates the pawl to withdraw it into the latch body. When the pawl is in the fully retracted position the release links are in their fully extended position. With the release links in the fully extended position the drive links cannot move the pawl. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features, advantages and operation of the present invention will become readily apparent and further understood from a reading of the following detailed description with the accompanying drawings, in which like numerals refer to like elements, and in which: 
         FIG. 1  is a perspective view of the latch on an oven; 
         FIG. 2  is a perspective view of the door of the oven slightly open with the latch in an intermediate position; 
         FIG. 3  is a perspective view of the oven door fully open, and there being the use of two latches, i.e., an upper and lower one, with the lower latch in dashed lines and a handle bar connecting the upper and lower latches also shown in dashed lines; 
         FIG. 4  is a top view of the oven of  FIG. 1  with the latch fully opened and the door freely opened; 
         FIG. 5  is a right-hand operation latch top view with the keeper/striker in dashed lines and the latch in the fully open position; 
         FIG. 6  is a top view of the latch of  FIG. 5  in the intermediate or partial release position; 
         FIG. 7  is a top view of the latch of  FIG. 5  in the fully open position with the release linkage extended and the hook-ended pawl rotated into the latch housing, and showing a top view of the keeper/striker; 
         FIG. 7 a    is a perspective view of the latch; 
         FIG. 8  is a perspective view of a keeper/striker cup used with the latch with the back of the cup exploded away; 
         FIG. 9  is a plan/top view of the latch in the extreme closed position, the top housing member being removed; 
         FIG. 10  is a plan/top view of the latch in the engaged position, the top housing member being removed; 
         FIG. 11  is a plan/top view of the latch in the detent position, the top housing member being removed; 
         FIG. 12  is a plan/top view of the latch in the extreme open position, the top housing member  119  being removed; 
         FIG. 13  is a perspective exposed view of the latch components; 
         FIG. 14  is a plan/top view of the latch with the top of the housing removed and the latch in the closed position engaging the keeper/striker; 
         FIG. 15  is a front view of the latch of  FIG. 14  in the closed position showing sectional cuts A, B, and C; 
         FIG. 16  is a plan/top view of the closed latch of  FIG. 15  at section A-A; 
         FIG. 17  is a plan/top view of the closed latch  FIG. 15  at section B-B; 
         FIG. 18  is a plan/top view of the closed latch  FIG. 15  at section C-C; 
         FIG. 19  is a plan/top view of the latch with the top of the housing removed and the latch in the engaged position with the hooked finger of the pawl within the cup portion of the keeper/striker; 
         FIG. 20  is a front view of the latch of  FIG. 19  in the engaged position showing sectional cuts D, E and F; 
         FIG. 21  is a plan/top view of the engaged latch of  FIG. 20  at section D-D; 
         FIG. 22  is a plan/top view of the engaged latch of  FIG. 20  at section E-E; 
         FIG. 23  is a plan/top view of the engaged latch of  FIG. 20  at section F-F; 
         FIG. 24  is a plan/top view of the latch with the top of the housing removed and the latch in the detent position; 
         FIG. 25  is a front view of the latch of  FIG. 24  in the detent position showing sectional cuts G, H and J; 
         FIG. 26  is a plan/top view of the detented latch of  FIG. 25  at section G-G; 
         FIG. 27  is a plan/top view of the detented latch of  FIG. 25  at section H-H; 
         FIG. 28  is a plan/top view of the detented latch of  FIG. 25  at section J-J; 
         FIG. 29  is a plan/top view of the latch in the extreme open position; 
         FIG. 30  is a front view of the latch of  FIG. 29  in the open position showing section cuts K, L and M; 
         FIG. 31  is a plan/top view of the open latch of  FIG. 30  at section K-K; 
         FIG. 32  is a plan/top view of the open latch of  FIG. 30  at section L-L; 
         FIG. 33  is a plan/top view of the open latch of  FIG. 30  at section M-M; 
         FIG. 34  is a plan view of the latch with the tip of the housing removed and where the detent ball is in the depressed position where the pawl continues to be extended into the keeper and the release links are beginning to extend; 
         FIG. 35  is a front view of the latch of  FIG. 34  in the detent ball depressed position showing section cuts N, P and R; 
         FIG. 36  is a plan/top view of the latch of  FIG. 34  at section N-N; 
         FIG. 37  is a plan/top view of the latch of  FIG. 34  at section P-P; 
         FIG. 38  is a plan/top view of the latch of  FIG. 34  at section R-R; 
         FIG. 39  is a plan/top view of the closed latch of  FIG. 14  in the sectional view B-B of  FIG. 17 , but with the keeper/striker and its back plate mounted to a door jamb with mounting screws and nuts, and the gasket compressed, where the latch is positioned within the door; and 
         FIG. 40  is a plan/top view of the latch in the engaged detent position of  FIG. 27  showing section H-H. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is a latch  100  mounted on a door structure  501  of an enclosure such as an oven  500 ,  FIGS. 1-4 , which latch  100  has an extreme fully closed position, a detent position indicating a closed latch about to be opened, a further detent position indicating a partially opened latch, and an extreme fully open position. The latch is operated by a lever/handle. When in the extreme open position the lever/handle is held in a fixed abutment position so that it cannot be rotated towards the closed position. A release structure frees the handle when it moves against a striker plate mounted on a door jamb structure. 
       FIGS. 1, 2, 3, and 4  show the latch  100  mounted on an oven door  501  and the latch and door in the closed, partially released opened, opened with two latches and opened with a single latch, respectively. 
       FIGS. 5, 6 and 7  show the closed, engaged, and open positions of the latch  100 , respectively. The latch  100  is designed such that the operator will not cause it to strike against the door jamb mounted keeper/striker  201  while in the closed position,  FIG. 5 , nor will the operator cause the latch to strike against the door jamb mounted striker  201  while in the in the engaged position,  FIG. 6 . 
       FIG. 7 a    shows a perspective view of the latch, while  FIG. 8  shows an exploded perspective view of the keeper/striker  201 ,  202  for the latch  100 . The latch housing  101 ,  119  is a relatively quick installation. On one side there is an ear  401  with a vertical opening or channel  403  for a pin or screw  404 . On the other side there is a spring clamp  402   
     With the top housing member  119  removed, the latch is shown in detail in plan top views in  FIGS. 9, 10, 11, and 12 . In  FIG. 9 , the latch  100  is in the closed position. In  FIG. 10 , it is in the engaged position where the pawl  111  has traveled into the keeper/striker  201  cup so that the door is somewhat opened as shown in  FIG. 2 , but the pawl still engages the keeper to prohibit the complete opening of the door. In  FIG. 11 , the latch is in the detent position where the lever/handle  112  will not move freely indicating the door should not be closed in the latch in that position. In  FIG. 12  the latch is in the open position where the release links can engage the keeper striker plate  201  to close the latch. 
       FIG. 13  is a perspective exploded view of the latch showing its components. Shown is a top housing member  119  and a bottom housing member  101  and two interacting linkages, which for the purposes of describing the function of the latch  100  will be known as the main (drive) linkage, and the release linkage. 
     The main/drive linkage has a pawl operation housing pivot pin  105   a , a lever handle operation housing pivot pin  105   b , an upper main/drive link  108 , a pawl pivot pin  109 , a handle pivot pin  110 , a pawl  111  with a hooked end  230 , a lever handle  112 , a lower main/drive link  114 , a main/drive linkage biasing spring  117 , and a lever handle biasing spring  118 . The housing pawl operation pivot pin  105   a  and housing lever/handle operation pivot pin  105   b  are rotational fits in the bottom housing member  101  and the top housing member  119 , and provide motion constraints for the pawl  111  and lever/handle  112 . Link  108  and link  114  pivot about their mid-points each being rotationally constrained between the bottom housing member  101  and top housing member  119 . The pawl pivot pin  109  and lever/handle pivot pin  110  are rotationally constrained at opposite ends between the link  108  and the link  114 . The pawl  111  is rotationally constrained to the pawl pivot pin  109  and has a sliding/rotational fit to the pawl operation housing pivot pin  105   a . The lever/handle  112  is rotationally constrained to the lever/handle housing pivot pin  105   b  and has a sliding/rotational fit to the handle pivot pin  110 . 
     This arrangement enables a controlled linear and rotational transformation of the pawl  111  in relation to bottom housing member  101 , through an angular movement of the lever/handle  112  about the lever/handle operation housing pivot pin  105   b . The main/drive linkage spring  117  provides a bias to the main linkage  108 ,  112 , driving it to either extreme of its available motion, while the lever/handle biasing spring  118  provides a bias to the lever/handle  112 , driving a rotation about lever/handle housing pivot pin  105   b.    
     The arrangement of the linkage and geometry of the components ensures that at one extreme the main/drive linkage can only be driven via the lever/handle  112 , henceforth known as being in the locked position, while at the other extreme, the main linkage cannot be driven by lever/handle  112 , henceforth known as being in the open position. 
     The release linkage consists of lower fixed pivot link  106 , a lower floating pivot link  107 , a bearing  113 , an upper floating pivot link  115  and a upper fixed pivot link  116 . The link  106  and the link  107  are rotationally constrained at one end between bottom housing member  101  and top housing member  119 , while their other ends are rotationally constrained to link  107  and link  115  the pin position of which is movable. The other ends of link  107  and the link  115  are rotationally constrained to the pawl pivot pin  109  in the main/drive linkage. 
     The bearing  113  is a rotational fit to link  106  and acts as a roller to reduce friction between any surfaces it comes into contact with. This release linkage provides a means of moving the main/drive linkage from its extreme open position. 
     Both linkages are constrained between the bottom housing member  101  and top housing member  119 , which provide the only mechanical fixings for the whole latch assembly  100 . Each of the upper main/drive link  108  and the lower main/drive link  114  have a stub shaft  120  which extends through a stub shaft journal hole  120  in the respective adjacent outer face of the upper and lower housing members. This provides the central pivot point for these two links 
     Further, an arrangement consisting of a detent spring  102 , a steel ball  103  and detent retainer  104  provide an intermediate stop/detent position between the locked and open positions of the main linkage. This structure provides a physical indication that the lever has moved from the full closed/locked position to an intermediate position where opening is about to begin. The detent retainer  104  is pressed into the bottom housing member  101 , as an interference fit, forming a retaining feature for a steel ball  103 , which is biased in place by the detent spring  102 . 
     The main drive link spring  117  is a torsion spring with two arms each with a downward pointed end (foot). One end of the spring  117  is pinned to the bottom housing member  101  at a fixed point  220  and the other end of the spring  117  is pinned to the pivot point pin  109  between the main/drive links  114  and  108 . This permits the spring  117  to float between different positions. 
     The lever/handle biasing spring  118  is a torsion spring with one short straight arm and a longer arm with a downward extending pointed end (foot). This spring  118  sits in a torroid-shaped cavity  221  in the top face of the lever/handle  112 , a short radial extending slot  222  extend from the torroid cavity  221 . The short leg of the spring  118  sits in the slot  222  while the coil of the spring  118  sits in the torroid-shaped cavity  221 . The longer arm of the spring  118  has its downward end secured to a receiving hole  223  in the adjacent sidewall casting of the bottom housing member  101 . 
     The latch  100  essentially has three, two-piece links. The links are structured with top and bottom members being a “pair” so that they may be separated to install, i.e., receive the respective pivot pins. One paired release link  106 ,  116  has a fixed housing pin  105   b  and a floating pin  224  tying it to the second paired release link  107 ,  115 . 
     The other end of the second link  107 ,  115  is pinned  225  to the end of the pawl and the main/drive link  108 ,  114  with the pawl pivot pin  109  into which one end of the main/drive linkage spring  117  fits its upper arm downward leg. The opposite end of the main/drive links  108 ,  114  is each tied to the lever/handle  112  having the elongate cavity  226  with the side recess  227 . The lever/handle  112  rotates counter clockwise to open the latch and clockwise when the latch is being closed. 
       FIG. 14  shows a plan/top view of the latch  100  in the closed position with the pawl  111  engaging the keeper/striker  201 . The spring  117  has its downward leg engaging a point  220  on the bottom housing. The handle spring  118  has one leg engaging a bottom housing receiving hole  223  and the other leg positioned within a slot  222  in the lever handle  112 .  FIG. 15  shows a front view of the latch handle  112  extending outwardly (from a door) when the latch  100  is in the closed position showing sectional cuts A, B, and C through the latch  100 .  FIG. 16  shows the closed latch  100  engaging the keeper striker  201  with it pawl  111  hooked finger portion  230 . 
       FIG. 17  illustrates the hold closed position where the drive link pin  110  is held in the side recess  302  of the three lobed guide slot  301 . This slot  301  has a main slightly curved portion which is formed by a left lobe area  231  and a right lobe area  232 , which actually operates as a cam guideway for the pin  110  which operates as a cam follower. The side recess  302 , in the middle, holds the pin  110 ,  FIG. 17 , when the latch is in the extreme closed position. This is really a stop or detent-hold position, establishing a final clockwise rotation position for the lever/handle  112 . It also prevents link  108  and link  114  from rotating in a clockwise rotation. This in turn prevents the pawl  111  from moving, thus holding any compressive load generated between the latch and the keeper. 
       FIGS. 19, 20, 21, 22, and 23  show different sectional cut views of the latch  100  in the engaged position. The engage position is where the hooked finger  230  still engages the cup of the keeper/striker  201  to hold the door  501  closed and the gasket  323  still compressed, but the latch  100  is about to open. 
     In the engaged position, as shown in  FIG. 22 , the lever/handle  112  has been freely rotated counterclockwise about 10 degrees, at which point it provides a resistance indication, indicating that the latch while still closed is about to open. This resistance indication arises because the cam follower, i.e., pin  110 , is moved out of the side recess  302  to come into contact with the far side of the guide slot  301 ,  FIG. 22 . But as the pin  110  moves out of the side recess  302 , the links  108 ,  114  and the pawl  111  will be free to move, releasing any compression generated between the latch and the keeper  201 . 
     In normal use, rotating the handle though the initial 10 degrees releases the compression, which moves the main linkage  108 ,  114 , the pawl pivot pin  109 , the handle pivot pin  110  and the pawl  111  to an indeterminate position where the pin  110  will move someway into the right hand lobe of the guide slot  301  in the handle  112 , coming to rest when the compression force is reduced to zero. 
     As the lever/handle continues to rotate counterclockwise, the pin  110  is caused to move by the slot towards the right lobe. This action will start to rotate the link  108  clockwise which in turn will push the pawl  111  outwardly, being guided by its pawl slot  210  operation with the pawl operation housing pin  105   a . The secondary linkage  106 ,  107 ,  115  and  116  is also moving during this time and can assist the operator in overcoming any resistance or restriction caused by the gasket  323  taking a set and preventing the door form opening. 
       FIGS. 24, 25, 26, 27 and 28  show different sectional cut views of the latch  100  in the detent position. 
     When cam follower, pin  110 , is fully in the right lobe, because the lever/handle  112  has been rotated counterclockwise about another 15 degrees, the detent position is attained,  FIG. 27 . At this point there is sufficient resistance/friction in the mechanism to overcome the forces from the springs  117  and  118 . So in normal use, the user can move the lever/handle  112  counterclockwise to the stop caused by the detent feature. If the lever/handle  112  is released by the user at this point, it should remain in this position. This is to enable the door to be left ajar to release any pressure, steam or other gas from the inside of the enclosure while the pawl  111  remains engaged with the keeper  201 . 
     In the full detent position, the detent ball  103  is driven by the detent spring  102  and guided by the detent retainer  104  to contact the detent feature (dimple)  303  in the end of the main drive link  108 ,  FIG. 28 . This establishes the full lateral (straight outwardly transition) movement of the pawl,  FIG. 27  where the latch and the door is held in the “cracked-open” position shown in  FIG. 2 . In  FIG. 27  the pawl  111  is shown in its fully outwardly extending position. The further movement of the pawl will be a counterclockwise rotation about its housing pin  105   a . This is only a transitional position. It is not intended that the latch can be left in this position as the “vent” position is the one recited above. 
     The further counter clockwise rotation of the lever/handle  112  brings the latch to the open position,  FIG. 29 , where the pawl  111  is fully counterclockwise rotated into the housing (about 75 degrees). In this position the lever/handle  112  cannot rotate counterclockwise further because its right edge abuts the bottom housing member  101  wall,  FIGS. 29 and 31 .  FIGS. 29, 30, 31, 32 and 33  show the latch  100  in different sectional cut views in the extreme open position with the lever handle  118  held fixed from movement by the detent operation of the ball  103  against the detent indentation of the lower main drive link  114 , shown in  FIG. 28 .  FIG. 24  shows a plan view of the latch  100  where the detent ball  103  (shown in  FIG. 28 ) engages the detent indentation  233 , and holds the lever handle  112  positively in the fully open position. 
     As shown in  FIG. 28 , the detent spring  102  exerts a force against the detent retainer  104  which holds the detent ball  103  to engage the detent indentation (depression)  233 . 
     The lever/handle  112  and thereby the latch  100  is held in the open position with the cam pin  110  fully in the left lobe of the guide slot  301 ,  FIG. 32 . In this position, the end of the main/drive link  114  abuts the abutment shoulder  305  on the handle,  FIG. 33 . It is the pin  110  located within the left hand lobe of the guide slot  301  which prevents the lever/handle  112  from rotating. The abutment shoulder(s)  305  on the lever/handle  112  are only required during the latch closing movement, interacting with the end of the main/drive links  108 ,  114  to prevent the pin  110  from entering the side recess  302  of the guide slot  301  in the lever/handle  112  which would cause the mechanism to lock up. 
     However,  FIG. 33  does not show the lever/handle  112  as it is the lower link  114  which abuts the shoulder  305 . The upper main/drive link  108  is shown in  FIG. 31  and the lower link  114  is shown in  FIGS. 32 and 33 . 
     The benefit of the fixed pivot points is that they constrain a component&#39;s motion to one degree of freedom, thus enabling precise control of their movement. Controlled linear and angular displacement can only be achieved through either floating pivots, and/or sliding joints, although using a round pin within a slot enables a joint to slide and pivot within the same feature. 
     The floating main spring  117  ensures that the pawl  111  completes its full travel during either opening or closing, wherein the latch needs to change from one state to another without relying upon the operator. Thus, during opening, once the handle is rotated passed the detent position, the main spring  117  will drive the mechanism form the detent state to the fully open state without further movement of the handle. 
     During closing, the release linkage will push the main/drive linkage from the fully open state, through the detent state, where the main spring  117  will drive the main/drive linkage to ensure the pawl  111  is fully engaged with the keeper  201 . This ensures that the pawl does not unintentionally clash with the keeper. The detent state has been set to coincide with the “flip point” of the main mechanism so that the force required to hold the mechanism in that position is at it lowest despite the force being generated by the floating main spring  117  being at its greatest. 
     This is because the fixed end of the floating spring, the pivot point at the center of the pawl pin  109  and the center of ration of the main/drive links  108 ,  114  are collinear at this point. Rotation of the main/drive links  108 ,  114  in either direction will move the pawl pin  109  out of line with the fixed end of the floating spring and the center of rotation of the drive links  108 ,  114 . The force of the floating main spring  117  will drive the rotation of the main/drive links  108 ,  114  further in that direction. This effect can be achieved by another mechanism, but that would require springs to be located on or within one of the moving components, thereby requiring them to be larger, more expensive to produce and more complicated to assemble. 
       FIGS. 35, 36, 37, and 38  show different sectional cut views of the latch  100  held in the detent state. 
     The keeper/striker  201  and its back plate  202  are held to the door jamb  320  with mounting screws  322  and nuts  321 ,  FIGS. 39 and 40 . In the fully engaged (locked) position,  FIG. 39 , the pawl  111  hooked end  230  is fully exerted against the cup lip  234  to compress the gasket  323 . The travel of the pawl  111  is controlled by the operation of the cam pin  105   a  which operates within the pawl slot  210 . In the fully engaged and gasket depressed state, the link  114  has pulled the pawl  111  fully into the housing so that the pin  105   a  abuts the keeper/striker  201  end of the pawl  111 ,  FIG. 39 , and the gasket  323  is fully depressed to the sealing state. 
     In the release state, the link  114  has rotated so that the pawl  111  has moved outwardly from the housing so provide a space  235  between the main body of the oven and the oven door.  FIG. 40 . In this state, the pin  109  has been moved along the pawl slot  210  and the push-out link  115  has started to rotate outwardly. 
     The latch is held in the door  501  by the spring clamp  402 , on one side, and by the ear  401  having the channel  403  for receiving a mounting screw  404  which seats against the inside face of the door  501 , on the other side. 
     Many changes can be made in the above-described invention without departing from the intent and scope thereof. It is therefore intended that the above description be read in the illustrative sense and not in the limiting sense. Substitutions and changes can be made while still being within the scope and intent of the invention.