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RELATED APPLICATIONS 
       [0001]    This patent application is a non-provisional patent application of provisional patent application No. 62/041,899 entitled “Flush Door Latch” filed Aug. 26, 2014, priority from which is hereby claimed. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to hand-turned door latches used to hold moveable doors and panels in place, usually in their closed condition. More specifically, the invention relates to “pop-out” latches of the type where the handle retracts flush with the surrounding outer surface of the door or panel when the door is closed. 
       BACKGROUND OF THE INVENTION 
       [0003]    Latches with flush or near-flush handles have been devised in different ways so that the handle can be actuated to pop out for manual access. Many of these devices incorporate a reciprocal spring mechanism to accomplish this function. A mechanism may be employed to release the handle from its stowed, spring-loaded position. The handle can thereafter be turned so that the securing elements connected to the handle behind the door will rotate to a release position so that the door can be opened. After the door is closed, the handle is turned to the locking position and pushed in against the force of the spring to its stowed position, being secured there by the release mechanism. The handle may reside in a recessed housing or in a cutout of the door. 
         [0004]    A problem exists, however, with these devices in that there is no provision made to prevent the handle from being pushed in when it is not aligned with the recess in the door. If the handle is jammed against the door it can cause damage to either the handle or the door. There is therefore a need in the art for a door latch which prevents the handle from being pushed in unless it is properly aligned with its receiving recess. There is a further need for a door latch with this capability that is also compact and can be mounted directly to the door without a surrounding housing. Latches of this type need to be lightweight and easy to disassemble or replace when maintenance is called for. These needs are particularly acute in the aircraft industry. 
       SUMMARY OF THE INVENTION 
       [0005]    The flush-type latch of the present invention comprises a substantially cylindrical body having a flange adjacent one end and clamp means adjacent the other end for releasably mounting the latch to a panel such as a door panel. A cylindrical outer sleeve is axially retained within the body and is rotatable between two positions: a latch-open position and a latch-closed position. A handle is connected to an inner sleeve that is closely fitted within and keyed to a concentric outer sleeve to prevent relative rotation between the sleeves. This construction permits the inner sleeve to slide axially within the outer sleeve between extended and retracted positions while the sleeves must turn together. At least one inwardly extending control pin is affixed to the latch body and passes through aligned slots in both of the sleeves. By the location and direction of the slots, the rotation of the sleeves is permitted only when the inner sleeve is in the extended position. Furthermore, movement of the handle and inner sleeve axially to the retracted and stowed position is only permitted when the sleeves are in the latch closed position. A locking latch arm is affixed to the end of the outer sleeve and moves with turning the handle through the interconnecting engagement of the sleeves. As is customary, the locking arm is engageable with a suitable stationary structure to which the door panel can be secured. 
         [0006]    The inner sleeve is spring-biased in the extended position and held down in the retracted position by a catch and release trigger mechanism located in the top of the handle. This creates a convenient “pop-out” retractable handle that can reside wholly within a closely fitting outer housing or a recess formed or cut into the panel to which the latch is mounted. When installed, the latch body passes through a mounting hole in the panel and is clamped between an upper flange on the latch body and a threaded lock nut near the opposite end of the body. For further ease of maintenance, the locking arm is independently affixed to the latch mechanism by a threaded bolt so it can be removed without disturbing the rest of the latch. Thus, for ease of maintenance the entire latch assembly may be removed by loosening only one nut and one bolt. 
         [0007]    In preferred embodiments of the invention, the door latch has a retractable handle in which the handle can only be turned when it is in the extended position and in which the handle can only be retracted to the stowed position when it has first been rotated to the latch-closed position. In other preferred embodiments, the door latch does not require a surrounding housing and thus occupies a small volume. In other preferred embodiments, the door latch has a limited number of parts that may easily be disassembled for maintenance or replacement. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a latch in accordance with a preferred embodiment of the invention shown in a retracted position; 
           [0009]      FIG. 2  is perspective view of the latch of  FIG. 1  shown in an extended position; 
           [0010]      FIG. 3  is a side elevation of the latch shown in  FIG. 1  installed on a door panel ( 27 ) and stationary structure ( 28 ) shown in cross section; 
           [0011]      FIG. 4  is a sectional view of the latch taken along lines  4 - 4  of  FIG. 1 ; 
           [0012]      FIG. 5  is an exploded assembly view of the latch of  FIG. 1 ; 
           [0013]      FIG. 6  is a perspective in partial section of the inner sleeve ( 32 ), outer sleeve ( 36 ) and latch body ( 19 ) of the latch of  FIG. 1 ; and, 
           [0014]      FIG. 7  is a sectional view taken along lines  7 - 7  of  FIG. 2 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    A latch in accordance with a preferred embodiment of the invention is shown in  FIG. 1  and is designated generally by reference numeral  8 . The latch  8  includes an elongate handle  11  having a generally-planar top surface  11   a , opposed side walls  11   b , a central aperture  11   c , and a bottom surface  11   d . As best seen in  FIG. 5 , a release trigger  13  is mounted in the aperture  11   c . The release trigger  13  has a planar top surface  13   a  that aligns generally-coplanar with the top surface  11   a  of the handle, and two catches  10  on a barbed portion that extends generally transverse to the top surface  13   a . The trigger  13  is pivotally mounted on a widthwise-extending pin  15  that is seated in the opposed side walls  11   b  of the handle  11 . The trigger  13  pivots between first and second limit positions by depressing the top surface  13   a  against the biasing force of a torsion spring  12  surrounding the pivot pin  15 . In the first limit position, the catches  10  engage a widthwise-extending catch pin  16  and hold the handle  11  in a retracted position (when desired) as depicted in  FIG. 1 . In a second limit position, the catches  10  disengage from the catch pin  16  and allow the handle to be extended by the biasing force of a compression spring  35  within the inner sleeve  32  described below. Since the catches  10  are barbed, they are self-actuating by spring-biased lever action against the catch pin  16  as the handle is pushed into the fully retracted position. 
         [0016]    Referring to  FIG. 5 , a cylindrical hub  53  is fixed to and extends generally transverse from the bottom side  11   d  of the handle  11 . With reference to the handle shown in  FIGS. 1 and 2 , the hub  53  is fixed proximate the wider end of the handle, whereas the narrower end of the handle  11  is the portion to which the user grasps by hand. As best seen in  FIG. 5 , the hub has a pair of diametrically-opposed apertures  55  in the side walls. The apertures  55  are constructed and arranged in size and shape to align with a pair of apertures  57  in the inner sleeve  32  described below. 
         [0017]    The hub  53  is designed to coaxially align with and connect to an inner sleeve  32 . The inner sleeve has an elongate, generally-cylindrical shape. The inner diameter of the inner sleeve  32  is slightly larger than the outer diameter of the hub so that the hub  53  can coaxially align with and be inserted into the proximal (relative to the handle) end of the inner sleeve  32 . To connect the hub  53  to the inner sleeve, a pin  33  is inserted into the aligned apertures  55  and  57 . 
         [0018]    The outer surface of the inner sleeve  32  has diametrically-opposed, axially-extending splines  59 . In preferred embodiments, the splines  59  extend along the entire length of the inner sleeve  32 . As described below, the splines  59  are constructed and arranged to cooperatively engage and freely reciprocate within similarly-shaped grooves  61  in an outer sleeve  36 . The inner sleeve also has a pair of diametrically-opposed, L-shaped, motion-control slots  42  in the annular wall intermediate the splines  59 . In a preferred embodiment shown in  FIG. 5 , the motion-control slots  42  have a first portion  42   a  that extends axially along a substantial portion of the length of the inner sleeve (axial portion), and a second portion  42   b  that extends circumferentially less than about half of the circumference of the cylindrical wall of the inner sleeve (circumferential portion). As described below, the slots  42  control axial and rotational movement of the handle cooperatively with several other components. 
         [0019]    A pop-out biasing means is housed within the inner sleeve  32 . In preferred embodiments, the pop-out biasing means comprises a compression spring  32 . One end of the spring  32  contacts the distal end (relative to the handle) of the hub  53  while the other end sits on the bottom of the outer sleeve  36  as best seen in  FIG. 4 . As described below, the compression spring  32  urges the handle from the retracted position to the extended position when the handle  11  is rotated to a particular angular orientation relative to the latch body  19 . 
         [0020]    The inner sleeve cooperatively engages and telescopes within an outer sleeve  36 . The outer sleeve  36  is generally cylindrical and has an inner diameter slightly larger than the outer diameter of the inner sleeve  32 . A pair of axially-extending grooves  61  is formed in the interior surface of the outer sleeve  36 . In a preferred embodiment, the grooves extend the entire length of the outer sleeve  36  and have a shape that compliments the shape of the splines  44  so that the inner sleeve  32  can only translate axially within the outer sleeve  36 . 
         [0021]    The outer sleeve  36  has a pair of circumferentially-extending, motion-control slots  23  in the annular side wall. Preferably, the motion-control slots  23  are located near the proximal (relative to the handle) end of the outer sleeve  36 . The slots  23  are constructed and arranged to engage a pair of diametrically-opposed control pins  34  extending through the valve body  19 . The control pins  34  restrict translational (axial) movement of the outer sleeve in the valve body  19  and restrict rotational movement to a distance equal to the angular length of the slots  23 . As best seen in  FIGS. 6 and 7 , the control pins  34  also extend through the slots  42  in the inner sleeve  32 . As described in greater detail, the control pins  34  restrict movement of the inner sleeve within the valve body to translational (axial) movement only at one angular orientation, and to rotational movement only at its most resected axial position. 
         [0022]    As best seen in  FIG. 5 , the latch  8  has a body  19  that is substantially cylindrical and has an integral flange  17  proximate the top and a threaded portion  19   a  proximate the bottom. The threaded portion  19   a  of the body engages a clamp nut assembly  29  that includes a collar  20 , pressure lock ring  21  and lock nut  18 , which provides a mounting (clamp) force to a door panel captured between the flange  17  and the collar  20  as best seen in  FIG. 3 . 
         [0023]    A lock arm  23  projects radially outwardly from the bottom of the latch body  19 . The lock arm  23  has a generally-cylindrical body  23   a  and an integrally-formed, radially-projecting arm  23   b  as best seen in  FIGS. 1 ,  2  and  5 . The body  23   a  aligns axially with the latch body  19  and overlaps with it slightly. The arm body  23   a  is rotatably fixed to the latch body by a lock nut  31  and washer  49 . A plurality of washers  51  sit in between the arm body  23  and the axial end of the latch body  19  and allow the lock arm  23  to rotate into engagement with a stationary securing structure  28  such as shown in  FIG. 3 . 
         [0024]    In  FIG. 2 , the latch  8  is depicted in the released or extended position relative to the door panel to which the latch  8  is connected. When the trigger  13  is depressed, the catches  10  release from the catch pin  16  and the compression spring  35  urges the handle  11  outwardly. This feature is necessary when the latch is installed flush or sub-flush as shown in  FIG. 3 . 
         [0025]    In  FIG. 3 , the latch  8  is shown installed on a door panel  27  through a receiving hole  26  in the panel  27 . The latch  8  is mounted to the panel by a clamp force applied by the clamp nut assembly  29 . The body flange  17  tightens against the outer surface of the panel  27  while the collar  20  tightens against the inner surface of the panel  27 . When locked down, the latch handle  11  resides with a cavity  24  in the outer surface of the door panel  27  so that the handle  11  is flush or sub-flush with the outer surface. As further described herein, the handle  11  can be extended out of the recess  24  by depressing the trigger  13  and releasing the catches  10 . Then, when the handle is rotated, the locking arm  23  also rotates and disengages from the backside of the stationary structure  28 . The door panel  27  may then be opened. 
         [0026]    The internal construction of the latch  8  is shown in greater detail in  FIG. 4  in the retracted position. The catches  10  of the trigger  13  engage the catch pin  16  and releasably hold the handle in the retracted position against the force of the compressed pop-out spring  35 . The compression spring  35  extends through the inner sleeve  32 , which is open at both ends. The bottom or distal (relative to the handle) end of the spring  35  abuts the bottom end wall of the concentric outer sleeve  36 . The top or proximal (relative to the handle) end of the spring abuts the cylindrical hub  53  of the handle  11 . The handle  11  is rigidly affixed to the inner sleeve  32  by a pin  33  that is inserted through aligned bores  55 ,  57 . The inner sleeve  32  slidably engages the outer sleeve  36  by means of the splines  44  and mating grooves  61 , which prevent the inner sleeve  32  from rotating relative to the outer sleeve  36  as seen more clearly in  FIGS. 6 and 7 . Both sleeves are held captive to the latch body  19  by motion control pins  34 , which also prevent the sleeves from being pulled apart. This construction permits the inner sleeve  32  and handle  11  to telescope toward and away from the latch body  19  while the outer sleeve is permitted to rotate within the latch body  19 . The lock arm  23  is connected to the end of the outer sleeve  36  by the bolt  31 . Mating features (not shown) on the lock arm and outer sleeve end wall prevent their relative rotation. 
         [0027]      FIG. 5  shows an exploded assembly view of the latch  8 . This Figure more clearly shows the trigger spring  12 , which is held in operational position within the handle  11  by the pin  15 , and the barbed shape of the catches  10 . The alignment of the control pins  34  through holes in the latch body  19 , through the motion-control slots  23  of the outer sleeve  36 , and through the motion-control slots  42  of the inner sleeve captivate the handle  11  to the latch body  19  while limiting its rotation, and hence the rotational position of the lock arm  23 . The elements of the clamp nut assembly  29  and lock arm assembly are shown with like numbering as used in  FIGS. 1-4 . These elements include the collar  20 , pressure lock ring  21 , lock nut  18 , pressure seals  51 , lock arm  23 , bolt  31  and washer  49 . 
         [0028]    The inner and outer sleeves are shown in more detail in  FIGS. 6 and 7 . Both sleeves are diametrically symmetrical so that the structural features are identical pairs located 180 degrees apart. As seen in  FIG. 6 , the inner sleeve  32  has two motion control features; the pair of diametrically-opposed L-shaped slots  42  (only one shown here), and the two splines  44 . The splines  44  engage the grooves  61  in the outer sleeve  36 . The mating splines  44  and grooves  61  permit the sleeves to telescope but lock them against relative rotation. The axial portion  42   a  of the slots  42  prevent rotational movement of the inner sleeve  32  and handle  11  until the point of full extension of the inner sleeve  32 . This occurs when the control pins  34  are located at the bottom end of axial portion  42   a  of the slots  42 . At that location, the control pins  34  are also located in the circumferential portion  42   b  of the slots  42 . Only then can the handle  11  be turned from the latch-closed position to the latch-open position. With the handle  11  turned to the latch-open position, the control pins  34  contact the ends of circumferential portion  42   b  and are no longer in alignment with the axial portion  42   a  so that the handle  11  cannot be pushed inward to the retracted position. As best seen in  FIGS. 5 and 7 , the control pins  34  are fixed in radial bores in the housing  19  and extend inwardly through the outer sleeve  36  and then farther inwardly through the inner sleeve  32  as described above. 
         [0029]    By the mechanical relations depicted in  FIGS. 1-7  and as described above, it will be understood that the handle is rigidly connected to the lock arm rotationally while in slideable engagement with the latch body through engagement of the interconnecting sleeves. The sleeve slots and control pins allow the handle to be turned and moved toward or away from the body of the latch but in a controlled way. The handle can only be pushed to the retracted position when the rotation of the handle is returned to the latch-closed position and the handle is in alignment with the recess in the panel. 
         [0030]    Opening the latch from the closed retracted position is a three-step operation. The latch is shown in the latch-closed position and fully retracted. When the trigger  13  is depressed, the catches  10  are released, which allows the handle  11  to be pushed outwardly and extended by the force of the compression spring  35 . In this position shown in  FIG. 2 , the handle  11  can be easily grasped and rotated. This feature is essential if the latch handle is to be retracted and locked in a recess within the panel  27  as shown in  FIG. 3 . Once extended, the handle  11  and lock arm  23  can be rotated to the latch-open position. Rotation is permitted only in this extended position because of the control means discussed above. Afterward, the handle can be rotated back to the latch-closed position by reversing the steps of this sequence and pushing the handle to the fully retracted position against the force of the compression spring  35 . The above-described motion control means will not allow the handle to be pushed inwardly to the closed position unless the handle is first rotated to the closed position wherein the handle  11  is properly aligned with the recess in the door panel  27 . This functionality is an important aspect of the invention and prevents damage to the panel if the handle is pushed into contact with the panel (retracted) when it is not in alignment with the panel recess. When fully retracted, the handle is then secured in the closed position by the self-actuating reengagement of the trigger catches  10 . 
         [0031]    From the above description it will be apparent that the invention includes a compact latch occupying a very limited volume with minimal weight because the construction of the latch permits it to be mounted directly into a panel aperture. The latch is easy to repair or replace because the entire unit can be released from the moveable structure to which it is attached, such as a swing door, by unscrewing at most only two elements, a bolt and a nut. The lock arm is the component of the latch assembly which experiences the most wear and thus may need replacement over time. This can be done by removing only one retaining bolt without the need for disturbing the rest of the latch. The latch  8  also incorporates handle motion control means that prevents damage to the retractable handle and door panel. 
         [0032]    It will be readily understood by those in the mechanical arts that the dimensions of the various components of the invention can be selected to operate as described above without limitation to the particular configuration, proportions and dimensions shown in the preferred embodiment. As such the invention is to be defined only by the following claims and their legal equivalents.

Summary:
A “pop-out” latch includes trigger-actuated spring means for extending a latch handle out of a surrounding panel recess for ease of grasping. The handle is connected to an inner sleeve which is keyed to a concentric outer sleeve such that the sleeves turn together between open and closed positions while the inner sleeve can slide axially within the outer sleeve between extended and retracted positions. At least one control pin extends inwardly from the latch body through slots in both sleeves. By the location of the slots the rotation of the handle is only permitted when the inner sleeve is in the extended position. When closing the latch, movement of the handle and inner sleeve axially toward the retracted stowed position of the handle is only permitted when the handle is in alignment with the receiving panel recess.