Catcher pin assembly

Abstract

A catcher pin assembly for attachment to a catcher link of an aircraft frame, the catcher pin assembly comprising an engine mounting element 23 , a catcher pin 23 D, a compressible element 40, 41, 42, 43 , and a nut 38 which is lockable to the catcher pin 23 D, the compressible element 40, 41, 42, 43 being compressed between the pin and the mounting element and/or between the mounting element and the nut 38 , in the assembled condition of the assembly, such that the compressible element 40, 41, 42, 43 applies a predetermined resistance to rotation of the catcher pin 23 D relative to the mounting element 23 . The invention also relates to a method of testing a catcher pin assembly to determine if the catcher pin 23 D is carrying load from the catcher link, the method comprising applying a predetermined torque to the catcher pin 23 D sufficient to overcome the resistance to rotation of the catcher pin 23 D when it is unloaded, and determining whether the catcher pin 23 D rotates relative to the mounting element 23.

1 . A catcher pin assembly comprising a mounting element, a catcher pin, a compressible element, and a retaining element which is lockable to the catcher pin, the compressible element being compressed between a head of the pin and the mounting element and/or between the retaining element and the mounting element, in the assembled condition of the assembly, such that the compressible element applies a predetermined resistance to movement of the pin relative to the mounting element. 
   
   
       2 . A catcher pin assembly as claimed in  claim 1 , in which the compressible element comprises at least one spring washer. 
   
   
       3 . A catcher pin assembly as claimed in  claim 1 , in which the compressible element comprises at least one conical spring washer. 
   
   
       4 . A catcher pin assembly as claimed in  claim 1 , in which the compressible element and/or at least a part of the pin and/or the mounting element and/or the retaining element is provided with an anti-friction coating. 
   
   
       5 . A catcher pin assembly as claimed in  claim 1 , in which the retaining element comprises a nut. 
   
   
       6 . A catcher pin assembly as claimed in  claim 5 , in which the catcher pin comprises a stepped bolt, a shoulder being defined between a main shank portion and a threaded portion of the bolt, the shoulder limiting the motion of the nut as it is screwed onto the bolt. 
   
   
       7 . A catcher pin assembly as claimed in  claim 1 , in which the mounting element comprises a yoke. 
   
   
       8 . A catcher pin assembly as claimed in  claim 1  in which the mounting element comprises a failure tolerant mounting bracket for a rotary machine. 
   
   
       9 . A method of testing a catcher pin assembly of  claim 1  to determine if the catcher pin is carrying load applied by a structure supported on the mounting element, the method comprising applying a predetermined force to the catcher pin sufficient to overcome the said resistance to movement of the pin, and determining whether the pin moves relative to the mounting element. 
   
   
       10 . A method of testing a catcher pin assembly as claimed in  claim 9  in which the said predetermined force is a predetermined torque, and the said resistance to movement is a resistance to rotational movement of the pin. 
   
   
       11 . A method of testing a catcher pin assembly as claimed in  claim 9  in which the said structure comprises a rotary machine. 
   
   
       12 . A method of testing a catcher pin assembly comprising a catcher pin, a lockable retaining element and a mounting element, the method comprising passing the catcher pin through the mounting element into the lockable retaining element, using the retaining element to tighten the catcher pin assembly to a predetermined degree, locking the lockable retaining element to the catcher pin, determining an unloaded pin torque at which the catcher pin will just rotate relative to the mounting element when the catcher pin is not loaded, subsequently applying a test torque at least equal to the unloaded pin torque to the catcher pin, and determining whether the catcher pin moves relative to the mounting element. 
   
   
       13 . A method of testing a catcher pin assembly as claimed in  claim 12 , in which a compressible element is located on the catcher pin and is compressed between a head of the pin and the mounting element and/or between the retaining element and the mounting element when the catcher pin assembly is tightened. 
   
   
       14 . A method of testing a catcher pin assembly as claimed in  claim 13 , in which the compressible element comprises at least one conical spring washer. 
   
   
       15 . A method of testing a catcher pin assembly as claimed in  claim 12 , in which the lockable retaining element comprises a nut.