Aeronautics and astronautics – Landing gear
Reexamination Certificate
2003-02-10
2004-10-12
Carone, Michael J. (Department: 3641)
Aeronautics and astronautics
Landing gear
C244S1020SS, C244S1040LS
Reexamination Certificate
active
06802476
ABSTRACT:
The present invention relates to a latch device, and more particularly to a device for latching an airplane landing gear or an airplane landing gear hatch.
BACKGROUND OF THE INVENTION
In a conventional approach, latch devices of this type comprise a box containing a set of hinged elements mounted to pivot about respective parallel axes, said assembly including at least a hook and a locking lever connected to said hook by associated elastically deformable return means. The hook can then be unlocked by acting on the locking lever either via first actuator means in a normal mode of operation, or via a second actuator means in an emergency mode of operation in the event of said first actuator means not managing to unlock the hook.
The state of the art is illustrated by document U.S. Pat. No. 5,288,037 in the name of the Applicant.
That document describes a latching box of the type comprising a hinged locking lever having a first branch that carries a bearing wheel co-operating with a cam surface of a hook, and having a second branch that is connected, by means of a linkage, to the outlet shaft of a motor and stepdown gear box unit. For emergency unlocking, an oblong slot is provided in the linkage so as to enable the hook to pivot in spite of being locked, and an independent actuator sufficient to pivot the unlocking lever and disengage the bearing wheel. The independent actuator is, however, made in the form of a single-use pyrotechnic actuator (triggering by a powder cartridge which releases a propeller gas).
It should be observed that such a pyrotechnic actuator cannot be compared to an independently electrically controlled electromechanical actuator, and that said pyrotechnic actuator is for emergency operation and not normal operation.
The technological background is also illustrated by documents DE-C-731 274, U.S. Pat. No. 3,504,406, and EP-A-0 265 197.
The main problem which the invention sets out to solve relates to the structure and arrangement of the first actuator means which is associated with the normal mode of operation.
This first actuator means is usually implemented in the form of a linear actuator of hydraulic type. The advantage of such actuators is that their operation is reliable, since the technology involved has been mastered for a long time. Reference can be made to document GB-A-2 161 202.
That document describes a bolt which, in normal circumstances, secures the parts forming the hook. Action on the rod enables said connection to be unlocked in the event of blockage, and to be rotated relative to said parts. The actuating means associated with normal operation is a conventional linear actuator of hydraulic type (actuator
28
).
At the end of the description, it is briefly indicated that electrically controlled actuating means can be used as a variant, but the text does not mention the power and the independent characteristic of said possible electrical control.
Present trends are more and more towards finding ways of limiting the use of hydraulic components because of their considerable weight, and also because of the risk of leakage that are associated therewith.
In addition, with the hydraulic arrangement that is conventionally used, a single power supply block is provided that delivers fluid both to the landing gear drive actuator and to the latch block. Thus, when it is desired to unlock the hook, the hydraulic control acts simultaneously on the drive actuator, thereby tending to further increase the load exerted on the hook, and consequently makes it necessary to use a latch device that is capable of developing sufficient force to be able to overcome the load exerted on the hook and to absorb the internal energy generated by opening the hook under such a heavy load. Naturally, the power required means that the elements provided are of non-negligible weight, and that is always unfavorable in the field of aviation.
OBJECT OF THE INVENTION
It would thus appear to be advantageous to design a latch device in which the first actuator means associated with normal mode operation is capable of achieving unlocking while developing a minimum amount of power, unlocking in normal mode then taking place without noise or vibration, and while nevertheless being capable of withstanding the high levels of heating that can be encountered.
As a subsidiary point, another problem relates to the second actuator means for use in emergency mode operation when the first actuator means does not manage to unlock the hook. This is a breakdown situation in which the landing gear fails to be extended normally. The weight of the landing gear then exerts a considerable load on the hook. Consequently, in order to manage to unlock the hook, it is necessary to develop a large level of force in order to overcome any seizing in the moving parts.
Traditionally, this second actuator means associated with emergency mode operation is constituted by an electromechanical actuator made in the form of a common electric motor controlling both the rodding of the airplane latch boxes and the associated hydraulic valves. This implies the presence of a linkage that is relatively heavy, and that is always difficult to adjust during maintenance. The manufacturer must ensure that a particular sequence takes place in an emergency situation: firstly the hydraulics are switched off, then they are connected to the return circuit, then the hatch latches are released, and finally the landing gear latches are released.
Under such circumstances, it would be advantageous to be able to provide a latch device having second actuator means associated with the emergency mode of operation, enabling high torque to be developed for the purpose of unlocking the hook while it is under load, but without it being necessary to overdimension the motors nor to suffer the constraints of using a linkage that is heavy.
BRIEF SUMMARY OF THE INVENTION
The invention solves the main problem mentioned above by means of a latch device, in particular for latching an airplane landing gear or an airplane landing gear hatch, the device comprising a box containing a set of hinged elements mounted to pivot about respective parallel axes, said assembly including at least one hook and a locking lever connected to said hook by associated elastically deformable return means, said hook being capable of being unlocked by acting on said locking lever either via a first actuator means in a normal mode of operation, or via a second actuator means in an emergency mode of operation when said first actuator means fails to unlock the hook, the first actuator means associated with the normal mode of operation then being a low power electromechanical actuator under independent electrical control.
In a preferred embodiment, the electromechanical actuator is an electromagnet fixed to the box, having a plunger core controlling axial or rotary displacement of a pusher acting on the locking lever.
It is then preferable for the electromagnet to include a spring urging the pusher towards a retracted position as soon as said electromagnet ceases to be excited, which position corresponds to the locking lever being in a locked position. In particular, the pusher of the electromagnet co-operates with a projecting appendix of the locking lever provided on said lever in the vicinity of the pivot axis thereof.
Also preferably, the electromagnet is of the type having dual coils, and preferably includes means for reducing its electricity consumption after the end of its unlocking stroke.
Advantageously, the electromagnet is fixed to the box in removable manner, and is easily accessible, so as to be capable of being replaced directly by another electromagnet without it being necessary to dismantle said box.
In a variant, provision could be made for the electromechanical actuator to be a linear electrical actuator, or indeed a motor and stepdown gear box unit, or a small-sized torque motor.
As a subsidiary point, it is also advantageous to provide for the second actuator means associated with the emergency mode of operation to be likewise an electromechanical actuator unde
Collet Olivier
Felemez Eric
Fremiot Sébastien
Liegeois Pierre-Yves
Perathoner Dominique
Carone Michael J.
Messier-Bugatti
Semunegus L.
Sughrue & Mion, PLLC
LandOfFree
Latch device, in particular for latching an airplane landing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Latch device, in particular for latching an airplane landing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Latch device, in particular for latching an airplane landing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3305303