Patent Abstract:
An apparatus and method providing a quick-release latch mechanism for a walled enclosure access door. The latch mechanism includes a striker with one end slidably inserted into the enclosure and the other end located outside the enclosure. A keeper is located within the enclosure and adapted to releasably engage and be captively held by the striker when the access door is in the closed position. If necessary, the access door can be readily unlatched from within the enclosure by manually rotating the keeper away from the enclosure wall to disengage and cause removal of the striker as the access door is being manually pushed open from within the enclosure.

Full Description:
FIELD AND BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates generally to a door which is used to gain access to the interior of a steam generator and its related equipment, and more particularly to a door latch which can be quickly released by a person from within the steam generator or related equipment. 
         [0002]    Access doors for steam generators and related equipment (e.g., flues, ducts, windboxes, hoppers, air heaters, penthouses, vestibules, precipitators, baghouses, scrubbers, etc.) are used to gain entry into the interior of the steam generator apparatus and related equipment Installation and maintenance personnel need such access for movement of equipment and materials into and out of the steam generator and related equipment for installation, repair, and maintenance of the internal components and surfaces of the steam generator and related equipment. 
         [0003]    The prior art steam generator access door constructions are not known to have been equipped with latch mechanisms which can be unlatched from within the steam generator. 
         [0004]    The lack of providing steam generator access doors with a latch mechanism which is releasable from the inner side of the door has been due, in large part, to the harsh operating environment caused by the high temperature combustion product laden flue gas flowing through steam generators firing coal and other fossil fuels. These flue gases contain entrained products of combustion such as slag, ash, and/or soot which are deposited on the exposed surfaces of the steam generator. 
         [0005]    A variety of latch mechanisms which can be released from the inside of a door have been provided for freezers, refrigerators and the like, where the interiors are kept under a relatively clean environment. Such latch mechanisms are of multipart construction whose parts are automatically returned to the normal operative position after the door has been opened from the inside. See for example, U.S. Pat. Nos. 2,747,906; 2,849,250; 2,966,864; 3,936,086; and 4,372,591. 
         [0006]    Prior art latches which allow the opening of an access door from the indoor side are complex in construction and operation and may be difficult to manipulate in the dark and cramped quarters of a steam generator. 
       SUMMARY OF THE INVENTION 
       [0007]    It is therefore a principal aspect of the present invention to provide a quick-release latch structure which is of simplified construction and operation. 
         [0008]    A further aspect of the present invention is to provide an access door with an indoor latch release capable of withstanding the harsh environment of an operating fossil fuel fired steam generator. 
         [0009]    Another aspect of the present invention is to provide a latch structure requiring only a turn of a latch handle from inside the access door to release the striker and allow the access door to be pushed open. 
         [0010]    A further aspect of the present invention is to provide a rugged and durable latch structure including a striker releasable from inside the steam generator, and which is relatively inexpensive to fabricate and easy to assemble and manipulate. 
         [0011]    The present invention is drawn to a steam generator access door latch mechanism structured for quick release, if necessary, from within the steam generator. 
         [0012]    The quick-release latch mechanism must also be capable to withstand the harsh environment of an operating steam generator. The present invention accomplishes this by providing a latch mechanism which is simply comprised of two essential parts; i.e., a latch handle and a striker. Both the latch handle and the striker are disengaged and separately removed as the access door is being opened, and are manually returned to the normal operative position as the door is being closed. Thus, the latch handle and the striker are available for visual inspection and, if necessary, repair or replacement by maintenance personnel, each time that the access door is opened. 
         [0013]    In accordance with this invention, there is provided a quick-release latch mechanism for use with an access door for a walled enclosure. The access door is pivotably mounted on a door frame for swinging between open and closed positions. The quick-release latch mechanism includes a striker having a proximal end located on the outer side of the door and a distal end slidably extending into the enclosure through a corresponding slot formed in the door frame. A keeper is located within the enclosure adjacent the inner side of the door and adapted to releasably engage and be captively held by the striker when the door is in the closed position. If necessary, the access door can be quickly unlatched from within the enclosure by manually rotating the keeper away from the enclosure wall to disengage and cause removal of the striker from the slot as the door is manually pushed open from within the enclosure. 
         [0014]    The keeper is in the form of a latch handle having a forked cam at one end and a pistol-type grip at the other end. A catch pin is mounted in the forked cam end of the latch handle. 
         [0015]    The striker is formed with a latching hook at its distal end and a pivotably mounted threaded member at its proximal end. The latching hook includes a notch shaped to receive the catch pin of the latch handle. 
         [0016]    At least one yoke extends across the outer side of the access door, and has one end hinged to brackets secured to the door frame and the other end notched to engage the threaded member of the striker. A turning handle is threadably engaged with the threaded member at the proximal end of the striker to apply inward pressure to the exterior of the door by rotating the turning handle clockwise, while the door is in the closed position. 
         [0017]    When the access door is in the closed position, the pistol-type grip of the latch handle abuts or bears against the enclosure wall, and the forked cam end and catch pin are engaged with the striker latching hook. 
         [0018]    In accordance with the invention, if necessary, the access door can be readily opened, from within the enclosure, by manually rotating the latch handle away from the enclosure wall with an angle of rotation of about 90 degrees along a plane perpendicular to the wall to effect the release of the catch pin and disengagement of the latch handle from the striker latching hook thereby allowing the door to be manually pushed to the open position. 
         [0019]    Accordingly, another aspect of the present invention is drawn to a method of latching and unlatching a walled enclosure access door for quick release from within the enclosure, the method comprising the steps of pivotably mounting the door on a door frame for swinging the door between open and closed positions; providing a latch handle inside the enclosure, the latch handle having a pistol-type grip at one end and a forked cam at the other end with a catch pin mounted therein; providing a striker with a latching hook at one end and a pivotable threaded member at the other end; inserting the latching hook end into the enclosure; positioning the latch handle with the pistol-type grip end abutting the inside of the enclosure wall and the catch pin engaging the latching hook; pushing the door to its closed position for engagement with the threaded member of the striker; applying inward pressure to the exterior of the door while the door is in the closed position; and, if necessary, unlatching the door from within the enclosure by rotating the latch handle away from the enclosure wall thereby causing the catch pin to disengage itself from the latching hook with the latching hook being removed from the enclosure as the door is being manually pushed open. 
         [0020]    Another aspect of the invention involves the method of latching and unlatching a walled enclosure access door, wherein the step of unlatching the door includes rotating a quick-release latch handle 90 degrees from within the enclosure wall. 
         [0021]    Yet another aspect of the invention involves the method of latching and unlatching a walled enclosure access door, including the step of forming a slot in the door frame such that the latching hook is free to move into and out of the enclosure. 
         [0022]    Yet still another aspect of the invention involves the method of latching and unlatching a walled enclosure access door, including the step of mounting a yoke onto the door. 
         [0023]    Still another aspect of the invention involves the method of latching and unlatching a walled enclosure access door, wherein the step of applying inward pressure to the exterior of the door includes meshing the yoke with the threaded member of the striker. 
         [0024]    A further aspect of the invention involves the method of latching and unlatching a walled enclosure access door, wherein the step of meshing the yoke with the threaded member of the striker includes turning means threadably engaged with the threaded member of the striker. 
         [0025]    A still further aspect of the invention involves the method of latching and unlatching a walled enclosure access door, including the step of rotating the turning means clockwise to apply inward pressure to the exterior of the door. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a perspective view of a closed access door equipped with the quick-release latch mechanism of the present invention in the latched state, as seen from the indoor side; 
           [0027]      FIG. 2  is a perspective view of a closed access door equipped with the quick-release latch mechanism of the present invention in the latched state, as seen from the outdoor side; 
           [0028]      FIG. 3  is a perspective view of an access door equipped with the quick-release latch mechanism of the present invention in the process of being unlatched from the indoor side; 
           [0029]      FIG. 4  is a perspective view of an access door equipped with the quick-release latch mechanism of the present invention in the unlatched state and in the process of being opened from the indoor side; 
           [0030]      FIG. 5  is a perspective view of an access door equipped with the quick-release latch mechanism of the present invention in the unlatched state and in the process of being opened from the indoor side, as seen from the outdoor side; 
           [0031]      FIG. 6  is a perspective view of an access door equipped with the quick-release latch mechanism of the present invention in the unlatched state and in the process of being closed, as seen from the outdoor side; 
           [0032]      FIG. 7  is a perspective view of an access door equipped with the quick-release latch mechanism of the present invention in the process of being latched, as seen from the indoor side; 
           [0033]      FIG. 8  is a cut away top view of the quick-release latch mechanism of the present invention in the latched state; and 
           [0034]      FIG. 9  is a cut away top view of the quick-release latch mechanism of the present invention in the process of being unlatched. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0035]    Referring to drawings, wherein like reference numerals designate the same or functionally similar elements throughout the several drawings, there is shown in fragmentary fashion an upright wall  10  of a steam generator enclosure or passageway  12  which is provided with a wall opening  14  through which access may be had to the interior of the enclosure  12 . The opening  14  is of generally rectangular configuration, elongated in a vertical direction, and is defined by a door frame  16  provided in the upright wall  10 . A door casing  18  is mounted on the door frame  16 . A rectangular access door  20  overlaps the entire periphery of the casing  18  and is adapted to abut the casing  18  when the access door  20  is fully closed. The door  20  is reinforced by cross-stiffeners  19  affixed to the door side facing the interior of enclosure  12 . Grab bars  21  are mounted on the door frame  16  inside and outside of the enclosure  12  for ease of exit from and entry into the enclosure  12 . 
         [0036]    A pair of spaced upper and lower parallel horizontal yokes  22 , shown in  FIGS. 2 ,  5  and  6 , span the access door  20  and the door casing  18 . The yokes  22  are in the form of rigid channel members having a generally rectangular cross-section, and are bolted to corresponding brackets  24  which are in turn fixedly attached to the access door  20 . One end of each of the yokes  22  is hingedly secured about a corresponding pivot pin  26  mounted on a pair of support brackets  28  connected to the door frame  16 . Thus, the opening and closing of the access door  20  is readily effected through movement of the yokes  22  about the pivotal axis of pins  26 . Each of the yokes  22  is configured with a notch  29  at the other end, as shown in  FIG. 6 . 
         [0037]    In accordance with the present invention, there is provided a quick-release latch mechanism  30 , shown in  FIGS. 8 and 9 , with components thereof, particularly strikers  32 A-B and keepers  34 A-B being shown throughout the drawings. 
         [0038]    The strikers  32 A-B include a latching hook  36  formed at its distal end, and a coupler or clevis  40  formed at its proximal end. The latching hook  36  is configured with a notch  42  formed therein, and shown in  FIGS. 8 and 9 . The clevis  40  is pivotably connected to one end of a threaded member  44  by a pivot pin  46 . A turning handle  47  is threadably engaged with the threaded member  44 . 
         [0039]    Each of the keepers or latch handles  34  A-B is formed with a pistol-type grip  48  at one end and a forked cam  50  at the other end. The forked cam  50  includes a pair of supporting legs  52  which are spaced sufficiently apart so as to pivotably straddle the corresponding latching hook  36  of striker  32 A-B. A catch pin  54  is connected to the supporting legs  52  of the forked cam  50 . 
         [0040]    The following is a description of the operation of the access door latch mechanism  30  for quick release by a person from inside the steam generator enclosure or passageway  12 . The process of unlatching the access door  20  from the inside of enclosure  12  is effected by manually rotating the latch handles or keepers  34 A-B away from the enclosure wall  10  along a plane perpendicular to the wall  10  until the latch handles  34 A-B are disengaged from the corresponding latch strikers  32 A-B. 
         [0041]      FIG. 1  shows the access door  20  in the closed position as seen from the inside of enclosure  12 . Each of the of latch handles  34 A-B has its pistol-type grip  48  abutting or bearing against the enclosure wall  10  and its forked cam legs  52  pivotably straddling the latching hook  36 . 
         [0042]      FIG. 2  shows the access door  20  in the closed position as seen from the outside of enclosure  12 . The threaded members  44  of strikers  32 A-B are engaged with the notched ends  29  of yokes  22 . The turning handles  47  are rotated clockwise to apply inward pressure to the outer face or side of the closed access door  20 , and to thus secure the door  20  in its closed position. 
         [0043]      FIG. 3  shows the access door  20  in the process of being manually unlatched from the inside of enclosure  12 . The upper latch handle  34 A is in its engaged position with its pistol-type grip  48  abutting the enclosure wall  10  and its forked cam legs  52  pivotably straddled about the latching hook  36 . The lower latch handle  34 B is in the process of being manually disengaged from the latching hook  36  by the rotating of the pistol-type grip  48  away from the enclosure wall  10 , thereby causing the cam-action of the forked cam  50  to disengage the catch pin  54  from the latching hook  36 . The same procedure is followed in the manual disengagement of the upper latch handle  34 A from the latching hook  36  in order to complete the unlatching of the access door  20 . 
         [0044]      FIG. 4  shows the unlatched access door  20  as seen from the inside of enclosure  12 . The access door  20  is partially open and on its way to being manually pushed to a fully opened position. The latch handles  34 A-B have been manually disengaged from the respective latching hooks  36 , thereby unlatching the access door  20 . 
         [0045]      FIG. 5  shows the unlatched access door  20  as seen from the outside of enclosure  12 . The access door  20  is partially open and on its way to being manually pushed to a fully opened position. The latch hooks  36  are forced out of the enclosure  12  through the door frame slots  56  as the latch strikers  32  A-B are moved along with the access door  20  which is being pushed open from the inside of enclosure  12 . In order to seal against leakage of hot air or gases through the frame slots  56 , a resilient, high-temperature gasket  57  is provided for each frame slot  56  as shown. By being resilient or slightly compressible, the gaskets  57  provide a positive “feel” or indication as the cam-action engagement of the latch handles  34 A and  34   b  to the latching hooks  36  takes place. 
         [0046]      FIG. 6  shows the access door  20  in the process of being manually closed, as seen from the outside of enclosure  12 . In order to close and latch the access door  20 , the latching hooks  36  of latch strikers  32 A-B are slidably inserted through door frame slots  56  into the enclosure  12 , and the turning handles  47  and the threaded member  44  are pivoted clear of the closing path of the access door  20 . 
         [0047]      FIG. 7  shows the access door  20  in the process of being closed, as seen from the inside of enclosure  12 . The latch handles  34 A-B are manually placed into the enclosure  12  through the open access door  20 . The latch handle  34 A is being positioned so as to have the forked cam legs  52  pivotably straddling the latching hook  36  with the catch pin  54  resting in the latching hook notch  42 , and the pistol-type grip  48  being turned such that it will abut the enclosure wall  10 , as shown in  FIGS. 1 and 3 . The same procedure is followed in the manual engagement of the lower latch handle  34 B with the latching hook  36 . After the access door  20  is pushed to its closed position, the turning handles  47  and the threaded members  44  are pivoted to engage the yoke notches  29 . With the access door  20  thus closed, the turning handles  47  are rotated to apply inward pressure on the exterior face or side of the access door  20 , to secure the latching of the door  20  in its closed position, as shown in  FIG. 2 . 
         [0048]      FIG. 8  shows the latching mechanism  30  in a latched position. The latch striker  32  has its latching hook  36  extending into the enclosure  12  and in latched engagement with the cam  50  of latch handle  34  whose catch pin  54  rests in the notch  42  of latching hook  36 . The latch handle pistol-type grip  48  abuts the enclosure wall  10 . 
         [0049]      FIG. 9  shows the latching mechanism  30  in the process of being unlatched from the inside of enclosure  12 . The rotating of the latch handle  34  about 90 degrees from the enclosure wall  10  along a plane perpendicular to the wall  10  causes the cam-action of the latch handle cam  50  to move the catch pin  54  out of the notch  42  of the striker latching hook  36 . The thus unlatched handle  34  is manually removed from engagement with the latch striker  32 . 
         [0050]    Although the present invention has been described above with reference to particular means, materials, and embodiments, it is to be understood that this invention may be varied in many ways without departing from the spirit and scope thereof, and therefore is not limited to these disclosed particulars but extends instead to all equivalents within the scope of the following claims.

Technology Classification (CPC): 8