Abstract:
A stored energy system for opening aircraft doors, especially useful in connection with emergency slide compartment doors. The system includes a mechanical energy door opening mechanism and a mechanical energy door latch mechanism leaving a latch actuator. Both the latch actuator and the door opening mechanism each have resident stored mechanical energy means wound by rotating an input shaft. Discharge of the energy is prevented by restraining a reverse rotation of the input device, thus enabling the mechanical energy means to be wound in only one direction. When the aircraft door is to be opened, the latch actuator delatches the door and subsequently the door opening mechanism employs a pivotably mounted arm to open the door.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to opening mechanisms for aircraft doors and, more particularly, to stored-energy mechanisms that can be actuated in emergencies to rapidly open aircraft doors for exposing emergency equipment, such as a door slide. 
     The need to open aircraft doors in emergencies frequently arises when electrical power is unavailable. Currently, such doors typically are opened in emergencies using mechanisms that are chemically based, such as pyrotechnics. However, these chemically-based mechanisms generally are inefficient, inelegant and extremely costly. In addition, it is impractical to test these mechanisms periodically after installation aboard an aircraft. These mechanisms also occasionally misfire while the plane is airborne, thereby triggering the early activation of important aircraft safety mechanisms. 
     There is thus a need for a non-pyrotechnic aircraft door opening mechanism that is less costly to operate, is inherently more reliable, and is operable independently of the aircraft&#39;s electrical power system. The present invention satisfies this need. 
     SUMMARY OF THE INVENTION 
     The present invention is embodied in an improved aircraft door opening mechanism that is operable to open an aircraft emergency device door during an emergency without the need for electrical power and without the need for pyrotechnics. The door is mounted on an aircraft frame such that, when it is in a closed position, it covers an opening in the frame and, when it is in an open position, it exposes the opening. The door opening mechanism includes door latching means that is movable between a latched position, in which it retains the door in its closed position, and an unlatched position, in which the door can be moved toward its open position. Door opening means also are included for moving the door from its closed position toward its open position when the door latching means is in its unlatched position. In accordance with the invention, the mechanism further includes a first resident means for storing mechanical energy, e.g. a clock spring or equivalent spring, which is selectively actuatable to cause the door latching mean to move to its unlatched position, and a second resident means for storing mechanical energy, e.g., a spiral torsion spring, which is selectively actuatable to cause the door opening means to move the door from its closed position toward its open position. Because the energy required to operate the door opening means is stored in a mechanical form, the mechanism can be operated without the need for electrical power and without the need for dangerous pyrotechnics. The mechanism, thereby, is highly reliable and low in cost, and its reliability can be readily confirmed by periodic non-destructive testing. 
     More particularly, the door latching means includes a support fixed relative to either the aircraft frame or the aircraft door and a door latch positioned to engage the other of the aircraft frame or the aircraft door. A clock spring is operatively connected between the support and the door latch and is adapted to urge the latch to move out of engagement with the door. In addition, restraint means are included for restraining movement of the door latch under the urging of the spring, but being selectively movable to an unlocked position in which the door latch may be moved under the urging of the spring. In a more-detailed feature of the invention, the door latching means further includes a shaft connected between the spring and the support, the shaft being rotatable about its axis so as to wind the spring and thereby store mechanical energy. One-way releasable locking means restrains the release of the spring&#39;s stored mechanical energy, until selective actuation. 
     The door opening means can include an arm that is pivotally mounted on a support fixed relative to the aircraft frame. A spiral torsion spring, or equivalent spring, is connected between the support and the arm so as to urge the arm into engagement with the door and thereby open the door. Restraint means are included for restraining the arm against such movement, until selectively actuated. Rotatable input means connected between the spiral torsion spring and the support is rotatable about an axis so as to torsionally wind the spring and thereby store mechanical energy. The spiral torsion spring can advantageously be torsionally wound about the same axis as the arm&#39;s pivot axis. 
     While the preferred embodiment utilizes both a clock spring and a spiral torsion spring for the unlatching of the aircraft door and the opening of the aircraft door, it is understood that many alternative types of springs will also serve to achieve the desired effect of replacing pyrotechnic devices previously used. 
     Other features and advantages of the present invention should become apparent from the following description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of an aircraft frame having an external door with a door latch actuator and a door opening mechanism embodying the present invention. 
     FIG. 1a is a rear elevational view of a latch mechanism included in the door operating mechanism, as viewed from the left side of FIG. 1, i.e., from the inside of the aircraft, including a set of latches and a door latch actuator. 
     FIG. 2 is an enlarged view of the latch actuator as viewed in FIG. 1a. 
     FIG. 3 is a cross-sectional view of the latch actuator, taken in the direction of arrows 3--3 in FIG. 2. 
     FIG. 4 is a front elevational view of the latch actuator, as viewed from the right side of FIG. 1. 
     FIG. 5 is a side elevational view of a mechanical door opening system included in the door operating mechanism of FIG. 1. 
     FIG. 6 is a front elevational view of the door opening system, taken in the direction of the arrows 6-6 in FIG. 5. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference now to the drawings, and particularly to FIGS. 1 and 1a, there is shown a mechanism for unlatching and opening an external door 11 pivotally secured to an aircraft frame 13. The door is shown in FIG. 1 by solid lines in its closed position and by phantom lines in its open position. A set of releasable latches 15 (FIG. 1a) initially retains the door in its closed position. When the door is to be opened, for example to facilitate an emergency exit from the aircraft, the latches are released by a latch actuator 17 that is connected to the latches by a connecting rod 19. Immediately after this release, a door opening mechanism 21 urges an arm 23 to pivot outwardly into engagement with the door, to pivot the door toward its open position. 
     With reference now to FIGS. 2-4, the door latch mechanism 25 will be described in greater detail. As previously mentioned, the actuator releases the set latches 15 via the intermediate connecting rod 19. The actuator includes a generally cylindrical housing 27, which carries a clock spring 29 that stores sufficient mechanical energy to release the latches when actuated. The spring is connected to the rod via a gear reduction assembly 31, with an input shaft 33 connected between the spring and the gear reduction assembly and an output shaft 35 connected between the gear reduction assembly and the rod. The gear reduction assembly reduces the rotational motion of the spring as it is being released and, in so doing, substantially increases the force it provides to the rod. A U-shaped crank 37 converts the small but forceful rotation of the output shaft into substantially longitudinal motion of the rod, to release the latches. 
     The clock spring 29 in the form of a spiral steel band is tightened within the housing 27 by rotation of an input shaft 33 which is configured to receive a standard mechanical tool. Rigidly affixed to this input shaft, on the exterior of the housing, is a ratchet gear 39, that is engaged by a pawl 41 that normally permits the input shaft 33 to rotate in only one direction, i.e., the direction that tightens the spring. This pawl also functions as a release mechanism that may be controlled either manually or by a solenoid 45. As shown in FIGS. 2 and 3, the solenoid includes a generally half-cylindrical housing 47 bolted to the back side of the actuator housing 27 and a plunger 49 connected to the pawl by a linkage assembly 51. The pawl is pivoted secured to the front side of the actuator housing at a pivot point 53. When the solenoid is actuated, the plunger pulls on the linkage assembly, to pivot the pawl out of engagement with the ratchet gear, thus enabling free rotation of the input shaft. 
     With specific reference to FIG. 3, the clock spring 29 is connected at one of its ends by a bolt 55 to the input shaft 33 and at the other of its ends by a bolt 57 to the actuator housing 27. The input shaft&#39;s interior end 58 is geared so as to couple with the gear reduction assembly 31. As the input shaft rotates, it meshes with the reduction gear wheel 59 effectively reducing the rotational velocity as seen at the reduction gear shaft mesh 61 by a factor n1. Thrust and journal bearings interact between the reduction gear wheel and spider 63. A planetary gear 65 is rotatably borne by a journal bearing on a shaft member 67 of the spider 63 and meshes with both the reduction gear wheel shaft 61 and a ring gear 69 that is fixed to the housing. As the planetary gear is of greater diameter than the reduction gear, a second gear reduction of a factor n2 is effected, causing rotation of the spider at a decreased rotational velocity and at a corresponding increased force. The spider has an output shaft 35 which protrudes from the exterior of the housing. The U-shaped crank 37 is rigidly attached by appropriate means to an end to the output shaft, such that rotation of the output shaft causes the arcuate movement of the U-shaped crank. The intermediate connecting rod 19 is pivotally connected at one end to the interior of the fork by a bolt 71. Intermittently, along its length, the rod is likewise pivotally connected by bolts 73 to the latches, which are pivotally mounted to the aircraft frame by bolts 75. It will thus be observed that rotation of the output shaft causes the latch assembly to function in the manner of a bell crank. 
     After the clock spring 29 has been wound by forwardly rotating the input shaft 33, it is restrained from release by the pawl 41 and ratchet gear 39. Upon receipt of a control signal, the solenoid 45 pulls the plunger 49 inwardly to withdraw the pawl from the ratchet gear, enabling reverse rotation of the input shaft. This reverse rotation is transmitted via the reduction gear assembly 31 to the crank 37, with rotational velocity reduced by a factor n1×n2, but a force increased by the same factor. With reference again to FIG. 1a, the arcuate movement of the crank pulls the connecting rod 19 roughly axially, to pivot the set of latches 15 out of their position retaining the door 11 in its closed position. The crank and latches are depicted in their closed positions, retaining the door, via solid lines, and in their open positions, not retaining the door, via dotted lines. 
     After the actuation of the latch actuator 17 as described above, the door opening mechanism 21 is actuated. With reference again to FIG. 1, the pivot arm 23 and door 11 are shown via solid lines in their closed positions and via dotted lines in their open positions. The pivot arm has at its free end a roller 77 for rolling contact with the door as the arm pivots outwardly. 
     With specific reference now to FIGS. 5 and 6, the door opening mechanism 21 includes a plate 79 secured to the aircraft frame 13, a spiral torsion spring 81, and a latch assembly 83. The spring is positioned around a shaft 85 integral with the support plate, and the pivot arm 23 is positioned to pivot about the same shaft. A spring-restraining arch 85 also is integral with the support plate, to retain a straight segment 87 at one end of the spiral spring 81. A similar straight segment 89 at the spring&#39;s opposite end bears against the pivot arm, such that the spring is arranged to apply a torque to the pivot arm relative to the support plate. 
     The pivot arm 23 is normally restrained from moving relative to the support plate 79 by interlocking first and second hooks 97 and 99. The first hook 97 is secured to the pivot arm 23 at the base of the pivot arm 101, by pulling a plunger 107 which is pivotally attached to the second hook, and the second hook is secured via a second support plate 103 to the aircraft frame 13. When the pivot arm 23 and the door 11 are to be opened, a solenoid 105, actuated by a control signal, withdraws the second hook 99 from the first hook 97, to release the restraint on the pivot arm. 
     At the side of the pivot arm facing away from the support plate, an input device 91 for pivoting the arm towards a restrained position is mounted by means of screws 93 to the pivot arm. As previously mentioned, a roller 77 is mounted at the pivot arm&#39;s free end, for rolling contact with the aircraft door 11 during opening. As shown in FIG. 1, the swinging ends of the pivot arm and the door are substantially aligned with each other when the door is in its closed position and the pivot arm is restrained from moving. When the door is to be moved to its open position, the restraint on the pivot arm is removed and the arm pivots outwardly such that the roller contacts the door and forces it to open. As the arm and door pivot open, the roller will roll along the door&#39;s inside surface. 
     While the above constitutes a detailed description of the preferred embodiment, it does not limit the invention as claimed, and, in fact, there are many permutations of the above elements which will achieve the same effect, namely to replace current pyrotechnic door opening systems with mechanical stored energy devices and function as a less costly, practical and efficient method of opening doors aboard aircraft in case of emergencies.