Patent Publication Number: US-2006013687-A1

Title: Device for detecting impacts on an aeronautic propeller

Description:
Device for detecting impacts on an aeronautic propeller assembly The present invention concerns the detection of impacts on an aeronautic propeller assembly made up of a hub and blades.  
      The object of the invention is to propose a device that permits knowing, over the service life of a blade, during planned maintenance or in case of an incident, whether the blade had been subjected to impacts beyond levels normally encountered in normal use. The invention proposes a reliable and autonomous means for detecting and recording any abnormal impact during use, which means can be consulted during maintenance operations.  
      In a parallel patent application, filed under the number PCT/FR 02 01727 and whose contents are integrated into the present application by reference, the Applicant has already proposed a device for detecting and recording impacts along several axes of an aeronautic propeller blade, characterized in that it comprises an accelerometer integrated at the center of an aeronautic propeller blade and an electronic module to record any occurrence of impact different from predetermined levels during its service life. The device comprises an accelerometer with at least two axes integrated at the top of the blade equilibration device and it records impacts in two planes perpendicular to the axis of the blade. The accelerometer signals can be transmitted remotely to an electronic module situated in any location whatever and this electronic module makes the recordings, but, advantageously, the electronic module (and all its attached elements such as power supply, which also serves the accelerometer) is also integrated into the root of the blade, so that the device is completely autonomous and integrated with the blade. Thus, according to this parallel application, so as to monitor, count and record abnormal impacts, an accelerometer with 2 or 3 axes connected to an autonomous electronic module supplying the accelerometer is integrated, recovering data sent back from the accelerometer, in order to compare these data to predetermined levels, storing occurrences beyond the predetermined levels in memory and integrating a memory reading device, either by direct connection, or by UHF remote transmission.  
      The preceding invention therefore proposes integrating, at the root of the blade, a completely autonomous system for measuring and recording impacts beyond predefined thresholds, so as to monitor, by interrogation of the system, the number of cases encountered in use for the different predefined thresholds.  
      The object of the present invention is to propose a variant of the preceding invention.  
      The invention achieves its object by means of a device for detecting and recording impacts along several axes on an aeronautic propeller assembly made up of a hub and blades, characterized in that it comprises a plurality of accelerometers, which are integrated at the hub of the aeronautic propeller assembly and are positioned at the respective root of a plurality of blades, as well as an electronic module to record, during its service life, any occurrence of impacts at various predetermined levels. Each accelerometer with one or two axes is integrated at the level of the hub/blade connection in the plane that is most suitable as a function of the number of axes, recording impacts during functioning.  
      Advantageously, the device comprises at least one accelerometer with at least 2 axes integrated at the hub and positioned in the plane of each blade. In the case where the number of blades is even in number, it is useful to install only one accelerometer in the same plane for two blades. 
    
    
      The invention will be better understood and other advantages and characteristics will be demonstrated upon reading the following description referring to the attached drawings in which:  
       FIG. 1  is a sectional view of a propeller hub and a propeller blade root showing the implantation of the sensor/electronic module system,  
       FIGS. 2 and 3  are surface views of a propeller showing the implantation of the sensors relative to the blades, respectively, which are even and uneven in number,  
       FIG. 4  is a variant of  FIG. 2  showing a simplified implantation in the case of an even number of blades,  
       FIG. 5  is a view of a variant of  FIG. 1  at the level of the reading means for the electronic module,  
       FIG. 6  is a diagram of the electronic module. 
    
    
       FIGS. 1 and 5  show one example of implantation of the impact sensor (accelerometer) and the electronic module relative to a root  10  of an aeronautic propeller blade  14 . The device of the invention comprises, on one hand, an accelerometer  1  with 2 or 3 axes, set in hub  13  in the neighborhood of root  10  and, on the other hand, an autonomous electronic module  2 , also positioned in hub  13  and connected to the accelerometer  1  via connection wires  3 .  
       FIG. 1  shows an electronic module  2  integrating a connector  4  for the function of reading the memories of module  2  by direct connection; the major appeal of this version is its autonomy associated with the very low [energy] consumption of the electronic module.  
      According to  FIGS. 2 and 3 , sensors  1 , associated with a single electronic module  2 , are equal in number to blades  14  and are situated in the plane of each blade. However, in the case of an even number of blades, as in the case of  FIG. 2 , the blades are placed opposite one another two by two, and a savings can be made by positioning a sensor in the common plane of two opposite blades; this is shown in  FIG. 4  where there are only 3 sensors 1 for 6 blades  14 .  
       FIG. 5  shows an electronic module integrating an infrared linking device  6  permitting very simple remote reading, eliminating the disadvantages of a physical connection.  
       FIG. 6  diagrams the electronic module  2  comprising a power supply  20  by means of a lithium-type battery, for example, a circuit  21  assuring the processing of the accelerometer signals, processing the data or feedback of the data via an analog/digital converter  22 , a microprocessor  23  and a permanent memory  24  permitting storing in the form of a table, the number of occurrences of impacts for each axis of accelerometers  1  for each predefined level. In order to equip the embodiment of  FIG. 5 , module  2  also comprises a transmission unit  25  to communicate with a transmitter Tx or a receiver Rx.