Abstract:
A latching system includes a flexible hydraulic latch male portion, and a receiving rail female portion. The receiving rail female portion receives the hydraulic latch male portion therein. The latching system includes a hydraulic system for providing hydraulic fluid into the flexible hydraulic latch. The latching system includes a controlling device for controlling operation and hydraulic fluid insertion by the hydraulic system into the flexible hydraulic latch. The latching system includes an ejection system coupled to the hydraulic system or flexible hydraulic latch for reducing hydraulic fluid pressure within the flexible hydraulic latch during an ejection evolution.

Description:
GOVERNMENT LICENSE RIGHTS 
   This invention was made with Government support under U.S. Government contract F33615-97-2-3407 awarded by U.S. Air Force. The Government has certain rights in this invention. 

   FIELD OF THE INVENTION 
   This invention relates generally to latching mechanisms and, more specifically, to latching systems for aircraft canopies. 
   BACKGROUND OF THE INVENTION 
   Modern, moveable aircraft canopies contain many parts. The transparent portion of the canopy will be replaced several times during the life of an aircraft due to scratches and general deterioration. Transparency replacement requires costly frame disassembly and reassembly. 
   Attempts have been made to produce frameless aircraft canopies with little success. The frame provides structural stiffness and strong, secure, attachment points for hinges and latches. Any viable frameless canopy system must include a method for latching. Prior latching methods consisted of a male hook or pin located on the aircraft structure or canopy frame and a female receiver on the canopy frame structure or aircraft structure respectively. Such discrete latching methods produce concentrated loads, which cause bearing stress in the transparency in the region of the latch. 
   Glassy polymers craze at low stress levels. The effect of crazing on crack growth and localized failure is not well understood. Polymer transparencies yield at low stress levels and creep occurs after a fraction of service life. Cyclic, long-term loading, such as cockpit pressurization, induces creep and/or craze and reduces service life. Elevated temperatures, such as those experienced by high-speed aircraft, further increase the rate of creep and amplify the effect of crazing. 
   Therefore, there exists an unmet need to produce a latching system for a frameless canopy, which avoids plastic creep, and crazing due to concentrated loads yet securely holds the canopy in place. 
   SUMMARY OF THE INVENTION 
   The present invention provides a light weight and durable latching system for aircraft canopies. The present invention is less costly to produce and replace. 
   The present invention is a latching system for an aircraft canopy. An embodiment of the latching system includes a flexible hydraulic latch male portion adhesively coupled to the canopy, and a receiving rail female portion that is coupled to the aircraft fuselage. The receiving rail female portion receives the hydraulic latch male portion. The latching system includes a hydraulic system for providing hydraulic fluid into the flexible hydraulic latch. 
   According to an aspect of the invention, the latching system suitably includes a canopy controlling device for controlling canopy position and hydraulic fluid insertion by the hydraulic system into the flexible hydraulic latch. 
   According to another aspect, the latching system suitably includes an ejection system coupled to the hydraulic system or flexible hydraulic latch for reducing hydraulic fluid pressure within the flexible hydraulic latch during an ejection evolution. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings. 
       FIG. 1  illustrates an exemplary block diagram of the present invention; 
       FIG. 2  illustrates a perspective view of a latch formed in accordance with the present invention; 
       FIG. 3  illustrates a cross-section of the flexible portion of the latch; 
       FIGS. 4 and 5  illustrate the present invention in an open position and closed and locked positions, respectively; and 
       FIG. 6  is a trimetric exploded view of a latch attached to a canopy. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As shown in  FIG. 1 , the present invention provides a hydraulic latch system  20  for an aircraft canopy or for use in other latching applications, such as any door that separates zones of different pressure values. The components of the flexible hydraulic latch system  20  suitably include a flexible hydraulic latch  30  hydraulically coupled to a hydraulic system  32 . The hydraulic system  32  is suitably electro-mechanically coupled to a latch controller  34 . In an alternate embodiment, the hydraulic system  32  is electro-mechanically coupled to an ejection system  40  or the flexible hydraulic latch  30  is mechanically coupled to the ejection system  40 . 
   The latch controller  34  suitably provides electrical open and close signals to the hydraulic system  32 . The latch controller  34  suitably includes a cockpit open/close handle (not shown) that allows user to control position. The hydraulic system  32  injects substantially non-compressible fluid, such as without limitation Mil-H-83282 fluid, into the flexible hydraulic latch, when the hydraulic system  32  receives a close signal from the latch controller  34  and the latch  30  is in a closed position. The hydraulic system  32  extracts fluid from the latch  30  when the latch controller  34  provides an open signal. 
     FIG. 2  illustrates a perspective view of the latch  30 . The latch  30  includes end caps  50  and a flexible hydraulic latch male portion  52 . Each of the end caps  50  is suitably made of metal and is configured to securely receive an end of the flexible hydraulic latch male portion  52  therein. One of the end portions  50  includes a receiving port  56  that is configured to receive a connection to the hydraulic system  32  in order to receive hydraulic fluid into the end cap  50 . A cavity within the end cap  50  directs received hydraulic fluid into the flexible hydraulic latch male portion  52 . The opposite end portion contains an air purge valve. The air purge valve allows trapped air to be purged from the hydraulic system  32 . 
     FIG. 3  illustrates a cross-sectional view of the flexible hydraulic latch male portion  52 . The flexible hydraulic latch male portion  52  includes a section  58  that creates a circular cavity in the cross-section when filled with the hydraulic fluid. Two flanges  60  and  62  are attached to the portion  58 . The flexible hydraulic male portion  52  is suitably created from a neoprene rubber, such as without limitation Mil-R-6855 Class 260 Durometer Neoprene Rubber. The flexible hydraulic latch male portion  52  is suitably made with any rubber-like component that is resistant to ultraviolet and chemical attack and has an ability to operate in harsh temperature environments. In order for the flexible hydraulic latch male portion  52  to withstand some of the forces experienced in the latching of a canopy, the flexible hydraulic latch male portion  52  is reinforced with a reinforcing material  70 , such as without limitation, nylon fabric. In one embodiment, the reinforcement of the flexible hydraulic latch male portion  52  is engineered to withstand pull-off loads of 475 lbs/in or more. 
   The flexible hydraulic latch  52  is formed in a deflated state, such as that shown in FIG.  2  and FIG.  4 . As shown in  FIGS. 4 and 5 , the flanges  60  and  62  are shaped according to a base edge  80  of a canopy  82 . The flanges  60  and  62  are adhesively attached to the base edge  80 . In one embodiment, the canopy  82  is a polycarbonate canopy and the following are exemplary adhesives that can be used to bond the flanges  60  and  62  to the canopy  82 : DP-420, EC-2216, and EC-2615 by 3M; Uralane 5774 by CIBA-GEIGY; Click Bond 250 by Click Bond; and M-Bond AE 10 by Vishay Intertechnology. 
   The flexible hydraulic latch male portion  52  is suitably open on either end for receiving hydraulic fluid from the hydraulic system  32  through one or more of the end caps  50 . When the canopy  82  is in an open position, such as that shown in  FIG. 4 , the flexible hydraulic latch male portion  52  is evacuated sufficiently such that the latch male portion  52  maintains the fabricated state, i.e. the first section  58  forms an oval-shaped cavity. As the canopy closes, the unfilled or deflated section  58  slides into a receiving cavity  90  that is formed by a latch rail  96  that is attached around the cockpit of the aircraft (not shown). The cavity  90  includes a beveled opening area  98 , a reduced neck area  100 , and a circular latch area  102 . The beveled opening area  98  aids alignment and receives the latch male portion  52  therein and directs the latch male portion  52  through the neck  100  into the circular cavity  102 . 
   As shown in  FIG. 5 , after the canopy has positioned the latch male portion  52  into the circular cavity  102 , the hydraulic system  32  injects fluid into the latch male portion  52 , thereby expanding the latch male portion  52  to its full circular cross-sectional dimensions (state). When the canopy is fully closed and the latch male portion  52  is filled with hydraulic fluid, the flanges  60  and  62  mate with the edges of the rail  96  that form the beveled opening  98  and the neck  100 , and the expanded portion  58  mates with the walls of the circular cavity  102 . 
     FIG. 6  illustrates a trimetric exploded view of the canopy with two latch sections  120  and  121  attached to respective halves of the base of the canopy  82 . In this embodiment, the canopy  82  is latched and sealed by two latches  120  that are both controlled simultaneously by the hydraulic system  32 . The two latches  120  allow for safety by having redundancy. A latch rail  96  is attached to the fuselage of the aircraft (not shown) for receiving the latches  120  and  121 . 
   In one non-limiting embodiment, the ejection system  40  ( FIG. 1 ) instructs the hydraulic system  32  to purge the latch  30  of hydraulic fluid when an ejection is initiated. For example, the hydraulic system  32  can pump out or release hydraulic pressure in the latch  30 . The latch  30  can be purged by one or more mechanisms  200  ( FIG. 5 ) within the latch rail  96  that pierces the first section  58 , thereby allowing pressure release for hydraulic fluid during a canopy ejection. 
   While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.