Method of coating the inner wall surface of a hollow body and a hollow bodycoated thereby

Abstract

A method of coating the inner wall surface of a hollow body, the one end side of which is open and comprises there a free perimeter edge. The method involves covering or masking a region of the inner wall surface, applying an electric potential to the pin holder, the applying an electrolyte to the uncovered region of the inner wall surface, said electrolyte containing a coating material that has a low electrical resistance at the transition between the metallic material of the cylindrical wall of the pin holder and the material of another metallic component part.

1 . A method of manufacturing an igniter unit, including a hollow pin holder ( 1 ) the one end side of which is open and comprises wall with a free perimeter edge ( 1 . 3 ), said method involving the following steps: 
 masking a region of the inner wall surface ( 1 . 2 . 1 ), said region taking departure from the free perimeter edge ( 1 . 3 ) and extending over a certain axial length of the pin holder's ( 1 ) wall;    applying an electric potential to the pin holder ( 1 );    applying an electrolyte to the uncovered region of the inner wall surface ( 1 . 2 . 1 ), said electrolyte containing a coating material that has a low electrical resistance at the transition between the metallic material of the cylindrical wall ( 1 . 2 ) of the pin holder ( 1 ) and the material of another metallic component part.    
     
     
         2 . The method in accordance with  claim 1  in which gold is the coating material.  
     
     
         3 . The method in accordance with  claim 1  in which the electrolyte is applied by spraying.  
     
     
         4 . The method in accordance with  claim 1  in which prior to depositing the electrolyte, the pin holder ( 1 ) is brought into a position in which its longitudinal axis ( 6 ) is oriented vertically and in which the free perimeter edge ( 1 . 3 ) is located at the bottom.  
     
     
         5 . The method in accordance with  claim 1  in which the electrolyte is continuously being supplied to the inner wall surface ( 1 . 2 . 1 ) of the pin holder ( 1 ).  
     
     
         6 . The method in accordance with  claim 1  in which the electrolyte is discontinuously being supplied to the inner wall surface ( 1 . 2 . 1 ) of the pin holder ( 1 ).  
     
     
         7 . The method in accordance with  claim 1  in which for electroplating, the pin holders ( 1 ) are disposed in receiving stations on a rotary table having a vertical axis.  
     
     
         8 . An igniter unit comprising: 
 a pin holder ( 1 ) having a cylindrical wall  9  ( 1 . 2 ) and an end side that is open and forms a perimeter edge ( 1 . 3 ), said cylinder wall including an inner wall surface;    an electrolytically deposited coating applied to the inner wall surface ( 1 . 2 . 1 ), said coating being made of a material that has a relatively low electrical resistance at the transition between the material of the wall ( 1 . 2 ) and another component part; and    said inner wall surface ( 1 . 2 . 1 ) comprising a coating-free region that extends from the free perimeter edge ( 1 . 3 ) over a certain axial length of the wall ( 1 . 2 ).    
     
     
         9 . The igniter unit in accordance with  claim 8  in which said pin holder ( 1 ) carries a metal pin ( 3 ) having one end of which is embedded into an isolating filling material ( 4 ) which in turn is enclosed by a portion ( 1 . 1 ) of the pin holder ( 1 ), said pin in the region of its length that faces the free perimeter edge ( 1 . 3 ) and protrudes from the isolating filling material is coated with the same material as the inner wall surface ( 1 . 2 . 1 ) of the pin holder ( 1 ).