Abstract:
A locking system, in particular a locking system for aircraft landing gears. A space-saving, simple construction and little maintenance requirement of the locking system is achieved by at least one electromechanical drive unit, whose torque is transmitted to a drive shaft with a cam disk via axle-crossing transmitting. With the torque, the cam disk can move the locking system from the locked into the unlocked condition.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a locking system, in particular a locking system for aircraft landing gears according to the description herein, and to a method for operating a locking system for an aircraft. 
     Nowadays, modern aircraft mostly have hydraulic retractable landing gears. To ensure their air worthiness, in particular in high-speed flight, it is necessary that in operation the landing gear systems of such aircraft can safely be retracted, held and, if necessary, for instance during a landing operation, can just as safely be extended again. 
     Safely holding has so far been realized by locking systems which are mechanically connected with the structure of the aircraft and in the retracted condition of the landing gear system make a positive connection with the same. Such system is shown for instance in  FIG. 1 . 
     Only in the course of an externally activated hook opening movement is the landing gear system positively released and extended either hydraulically or by the acting gravitation. Due to the relatively high reliability requirements for such systems, the external activation of the hook opening movement now is achieved primarily by a hydraulically actuated piston and secondarily by a mechanical cable actuation or by an electromechanical actuating unit. 
     The cable systems of such mechanical actuating units frequently must be guided through the fuselage of the aircraft via pressure or temperature zones, deflection pulleys, guideways and distributors. What is disadvantageous here is the complex assembly, intensive maintenance and the varying cable tension due to different material properties in the system.  FIG. 1  shows such locking system for an aircraft. In the course of an externally activated hook opening movement, the landing gear can positively be released. Among other things, the hook opening movement can be activated mechanically by a cable system. The cable systems must be guided over a plurality of deflection pulleys and guideways, which is very expensive and also susceptible to failure. 
     Furthermore, locking systems with electromechanical actuating units are known from WO 2005/005252 A1. The same are realized by means of an electromagnetic coil or an electric motor with spindle or the like. Here, it is disadvantageous that the same cannot always be returned to the starting condition by simply shutting off the energy supply and are not capable of a reset/restart in any condition. 
     SUMMARY OF THE INVENTION 
     Therefore, it is the object of the present invention to develop a locking system as mentioned above such that the same has a space-saving and simple construction and requires little maintenance. 
     This object is solved by a locking system with the features herein. Accordingly, a locking system is provided, which in addition to the features known from the prior art includes a first electromechanical drive unit and a transmission as well as axle-crossing transmitting means for transmitting a torque from the drive unit to a drive shaft with a cam disk. The term axle-crossing designates the fact that the torque is transmitted e.g. by means of gear wheels or worm gears from a first shaft to a second shaft arranged at an arbitrary angle with respect to the first shaft. By means of the torque, the cam disk moves the locking system from the first into the second position. In engagement of the first means with the second means, however, both are fixed in the first position. 
     The first means can constitute e.g. a hook, and the second means can constitute e.g. a bolt. For unlocking the system, a torque is applied by the drive unit, which via the axle-crossing transmitting means is transmitted to a drive shaft which in turn is provided with a cam disk. Due to the rotation of the cam disk, the hook releases the retaining bolt. The retaining bolt advantageously forms part of a landing gear of an aircraft. For locking purposes, hook and bolt are returned to the first position. In the first position, the cam disk is disposed in a neutral position. The neutral position is a position in which the cam disk does not impede the hook in its freedom of movement. 
     The first driving device can comprise at least one electric motor, and the second driving device can comprise at least one hydraulic drive. By the term “first” and “second” drive unit it should, however, not be understood that e.g. the “first” drive unit necessarily is in primary use. This involves the advantage that for instance for the case of the failure of the aircraft hydraulics for instance the second driving device fails, but for instance the first driving device is ready for operation due to a different kind of drive. Consequently, the landing gear then can easily be unlocked, and the aircraft can be prepared for landing. 
     In addition, a first spring element advantageously is provided, which retracts the cam disk into the neutral position. This involves the advantage that the cam disk can be retracted in a simple manner without applying a torque by a drive unit. As a result, it still is possible to initiate retraction by the spring element with a single event, for instance by pressing a key. 
     The first means also can include an activating lever which is rotatably mounted on a shaft, and furthermore a hook which likewise is rotatably mounted on a shaft. The activating lever and the hook are connected with each other by a second spring element. This arrangement involves the advantage that the lever action can advantageously be used for the locking and unlocking operations. 
     Furthermore, the activating lever can comprise a rotatably mounted roller, on which the cam disk is at least partly rolling when transmitting the torque during the movement from the first into the second position. This roller involves the advantage that the frictional resistance occurring in the cam disk during rolling is kept as low as possible. 
     Another advantageous embodiment can consist in that in the second position the second spring element holds the activating lever and the hook in a stable position due to the spring force, which stable position can only be left by returning the locking bolt into the first position. This involves the advantage that separate retracting devices can be omitted. 
     It is likewise conceivable that the cam disk is connected with a freewheeling clutch. This involves the advantage that the cam disk on the one hand can transmit the torque with which the locking system is transferred from the first into the second position in one direction, and for instance for retracting the cam disk the same is decoupled from the drive unit. 
     The axle-crossing transmitting means advantageously can be configured as a worm or worm gear. This involves the advantage that an axle-crossing torque transmission can be realized with little space requirement. 
     It is likewise conceivable to configure the axle-crossing transmitting means as a gear wheel transmission, bevel gear transmission or friction gear transmission. 
     It is conceivable to configure the drive unit as an electric motor with a linearly arranged transmission. This arrangement allows an easy handling during assembly. 
     It can likewise be provided to configure the drive unit as a direct drive with a ring traveller/planetary gear combination. This involves the advantage that large gear ratios or large torques can be realized, and this with little space requirement. 
     In addition, it can be provided that the drive unit comprises redundant electric motors with freewheels and a transmission in a linear arrangement. As a result, the failure probability of the device can be reduced. 
     It can likewise be provided that the drive unit comprises redundant electric motors with freewheels and a transmission in a compact arrangement. Beside the failure-safety, this involves the advantage that the space requirement is further reduced. 
     It is furthermore conceivable that the drive unit comprises redundant electric motors with freewheels and a transmission in a 90° arrangement. 
     It can also be provided that the drive unit comprises an electric motor and a transmission in a linear arrangement with 900 worm gear transmission and a freewheel integrated in the worm gear. 
     This invention furthermore relates to a method for operating a locking system, in which for instance the landing gear of an aircraft is locked and unlocked by a locking system in accordance with the invention. 
     It is conceivable that the method of the invention is performed by the electromechanical drive unit, wherein the drive unit is operated by an on/off key. Thereby, it is avoided that in the case of too long an actuation of the drive, for instance by rotating the cam disk over 360°, there is a risk for the system. Thus, complex and expensive monitoring means can be saved. 
     It is particularly advantageous when the electromechanical drive unit of the locking system of the invention normally is used for the unlocking operation and the second drive unit is employed in the case of a failure of the electromechanical drive unit. For instance, a failure of the normally used drive unit can be detected by sensors and it can then automatically be switched over to the second drive unit. As a result, e.g. the pilot need not intervene separately. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantages of the invention are explained in detail with reference to an embodiment illustrated in the drawing, in which: 
         FIG. 1 : shows a perspective representation of a locking system for an aircraft in accordance with the prior art, 
         FIGS. 2A and 2B : show perspective representations of the front and rear side of a locking system according to one embodiment of the present invention, 
         FIG. 3 : shows a further perspective representation of the locking system as shown in  FIGS. 2A and 2B , 
         FIG. 4 : in turn shows a further perspective representation of the locking system as shown in  FIGS. 2A and 2B , 
         FIG. 5 : shows a side view of the locking system in the first position, 
         FIG. 6 : shows a side view of the locking system in the second position, unlocked by the device  20 , 
         FIG. 7 : shows a side view of the locking system, unlocked by the device  10 , 
         FIG. 8 : shows an electric motor and a transmission of the locking system in a linear arrangement, 
         FIG. 9 : shows a direct drive with ring traveller/planetary transmission combination in a perspective view, 
         FIG. 10 : shows a redundant electric motor with freewheels and a transmission in a linear arrangement in a perspective view, 
         FIG. 11 : shows redundant electric motors with freewheels and a transmission in a compact arrangement in a perspective view, 
         FIG. 12 : shows redundant electric motors with freewheels and a transmission in a 90° arrangement via worm gears in a perspective view, 
         FIG. 13 : shows an electric motor and transmission in a perspective view with worm gear transmission and an integrated freewheel in the worm gear. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 2 to 4  show perspective views of an embodiment of the locking device of the invention for a landing gear of an aircraft in a front and rear view, wherein an embodiment is shown in which two devices are provided for locking and unlocking and in which the first device  10  includes a drive unit  12  with an electric motor  12 ′ and a linearly arranged transmission  17 , and the second device  20  includes a hydraulic drive  20 ′. The axle-crossing transmitting means  15  and  16  are configured as a worm gear transmission  15 ′,  16 ′, wherein the worm gear transmission comprises a freewheel  50  integrated in the worm gear. 
       FIG. 5  shows the embodiment of the locking system of the invention in a side view. It is disposed in the first position, in which the system is locked. The first means  30  engages in the second means  40 . The second means  40  is a locking bolt  40 ′ of a landing gear system, and in the retracted condition of the landing gear system the means  30  can engage in the locking bolt  40 ′. The first means  30  includes an activating lever  32 , which is rotatably mounted on a shaft  34 . It likewise includes a hook  36 , which is rotatably mounted on the shaft  38 , wherein the activating lever  32  and the hook  36  are connected with each other by the spring element  39 , which is configured as a double spring. In the first position, the means  30  engages in the locking bolt  40 ′ via the hook  36 . The activating lever  32  in addition includes a rotatably mounted roller  31 , on which the cam disk  14  can at least partly roll when moving from the first into the second position. Via the first device  10  or via the second device  20 , the locking system can be moved from the first into the second position. 
     To guide the locking system from the first into the second position and thus unlock the system, a torque is applied by the drive unit  12 , which via the axle-crossing transmitting means  15 ′ and  16 ′ rotates the cam disk  14  mounted on the shaft  13  in anticlockwise direction. The cam disk  14  at least partly rolls on the roller  31 . As a result, an activating lever  32  can be depressed, whereby the hook  36  releases the bolt  40 . Via the spring  18 , the cam disk  14  can be retracted due to the freewheel  50  without cooperation of the drive unit  12 . 
     For safety reasons, a redundant driving device  20  is provided, which includes a hydraulic drive  20 ′. The same can depress the activating lever  32  via a lever  33 . 
       FIG. 6  shows the locking system in the unlocked condition in the second position, illustrated in a side view. The hydraulic drive  20 ′ is extended, whereby the activating lever  32  is depressed via the lever  33 . As a result, the hook  36  releases the locking bolt  40 ′. 
       FIG. 7  shows the locking system in the second position in a side view. By means of the drive unit  12  with the electric motor  12 ′, a torque is provided, which is transmitted to the cam disk  14  via the axle-crossing worm gear transmission  15 ′,  16 ′. Said cam disk depresses the activating lever  32 , whereby the hook  36  releases the locking bolt  40 . 
       FIG. 8  shows the drive unit  12  in a perspective view. The drive unit  12  includes an electric motor  12 ′ and furthermore a linearly arranged transmission  17 ′. 
       FIG. 9  shows a perspective view of the drive unit  12  configured as a direct drive  12 ″. The transmission is configured as a ring traveller/planetary transmission combination. 
       FIG. 10  shows the drive unit  12  in a perspective view. The drive unit  12  include two redundant electric motors  12 ′ with freewheels. The transmission  17  is arranged linearly with respect to the two redundant electric motors  12 ′. 
       FIG. 11  shows the drive unit  12  in a perspective view, wherein two redundant electric motors  12 ′ are provided. The transmission  17  is disposed above the two redundant electric motors  12 ′, so that a compact arrangement is obtained. 
       FIG. 12  shows the drive unit  12  configured with two redundant electric motors  12 ′. The two redundant electric motors  12 ′ are provided with freewheels, wherein the transmission is arranged at an angle of 90° via worm gears. 
       FIG. 13  shows the electric motor  12 ′ and the transmission  17  in a linear arrangement. The worm gear transmission is arranged at an angle of 90° and consists of the worm  15 ′ and the worm gear  16 ′. The worm gear  16 ′ has a freewheeling clutch  50 .