Blank for a flow forming method

Abstract

There is disclosed a tubular blank ( 31 ) for attaching to a stepped mandrel ( 41 ) of a flow forming assembly, wherein the tubular blank ( 31 ) has a stepped inner profile that may be tailored to the shape of the mandrel ( 41 ) before any flow forming is carried out on the blank ( 31 ). Also disclosed is a corresponding method of flow forming a shaped article by plastically deforming the tubular blank ( 31 ) over the stepped mandrel ( 41 ), where the forming of the shaped article may be carried out in one operation.

What is claimed is: 
     
         1 . A tubular blank ( 31 ) for attaching to a stepped mandrel ( 41 ) of a flow forming assembly, wherein the tubular blank ( 31 ) has a stepped inner profile. 
     
     
         2 . The tubular blank ( 31 ) as claimed in  claim 1 , wherein the tubular blank ( 31 ) has a stepped inner profile comprising:
 a first inner surface ( 32 ) extending circumferentially about a central longitudinal axis ( 50 ) to define a first inner volume ( 316 ) having a first inner diameter ( 34 );   a second inner surface ( 33 ) axially adjacent the first inner surface ( 32 ) and extending circumferentially about the central longitudinal axis ( 50 ) to define a second inner volume ( 317 ) having a second inner diameter ( 35 ) that is larger than the first inner diameter ( 34 ); and   an inner shoulder ( 36 ) between the first inner surface ( 32 ) and the second inner surface ( 33 ).   
     
     
         3 . The tubular blank ( 31 ) as claimed in  claim 2 , further comprising an end wall ( 37 ) extending radially inwardly from the second inner surface ( 33 ) to at least partly close the first inner volume ( 316 ). 
     
     
         4 . The tubular blank ( 31 ) as claimed in  claim 1 , wherein the tubular blank ( 31 ) is made of a material comprising at least one of a wrought steel, a nickel alloy and a titanium alloy. 
     
     
         5 . A flow forming kit comprising:
 a stepped mandrel ( 41 ) comprising a first mandrel region ( 42 ) having a first outer mandrel diameter ( 44 ) and a second mandrel region ( 43 ) having a larger second outer mandrel diameter ( 45 ); and   a tubular blank ( 31 ) as claimed in  claim 2 ;   wherein the tubular blank ( 31 ) is configured to cooperate with the stepped mandrel in that:   the first inner diameter ( 34 ) corresponds to the first outer mandrel diameter ( 44 ) such that the first inner volume ( 316 ) is suitable for receiving the first mandrel region ( 42 ); and   the second inner diameter ( 35 ) corresponds to the second outer mandrel diameter ( 45 ) such that the second inner volume ( 317 ) is suitable for receiving the second mandrel region ( 43 ).   
     
     
         6 . The flow forming kit as claimed in  claim 5 , wherein:
 the first inner surface ( 32 ) has an axial extent such that, when the first inner volume ( 316 ) receives the first mandrel region ( 42 ), an inner shoulder ( 36 ) of the blank ( 31 ) longitudinally opposes an outer mandrel shoulder ( 47 ) between the first mandrel region ( 42 ) and the second mandrel region ( 43 ).   
     
     
         7 . The flow forming kit as claimed in  claim 5 , wherein:
 the first inner surface ( 32 ) has an axial extent such that, when the first inner volume ( 316 ) is fully occupied by the first mandrel region ( 42 ), some but not all of the second mandrel region ( 43 ) is received by the second inner volume ( 317 ) of the blank ( 31 ), to support the blank ( 31 ) on the second mandrel region ( 43 ).   
     
     
         8 . The flow forming kit as claimed in  claim 5 , wherein a step of the inner profile has a shape that conforms to the shape of a step in the mandrel ( 41 ). 
     
     
         9 . A method of flow forming a shaped article ( 51 ), comprising:
 providing a stepped mandrel ( 41 ) that comprises a first mandrel region ( 42 ) having a first outer mandrel diameter ( 44 ) and a second mandrel region ( 43 ) having a second outer mandrel diameter ( 45 ) that is larger than the first outer mandrel diameter ( 44 );   providing a tubular blank ( 31 ) having a stepped inner profile;   locating the tubular blank ( 31 ) on the mandrel ( 41 ); and   plastically deforming the tubular blank ( 31 ) over the mandrel ( 41 ) to create the shaped article ( 51 ).   
     
     
         10 . The method of flow forming a shaped article ( 51 ) as claimed in  claim 9 , wherein:
 the tubular blank ( 31 ) comprises a first inner volume ( 316 ) having a first inner diameter ( 34 ) and a second inner volume ( 317 ) having a second inner diameter ( 35 ) that is larger than the first inner diameter ( 34 ); and   locating the tubular blank ( 31 ) on the mandrel ( 41 ) comprises the tubular blank ( 31 ) snugly receiving the first mandrel region ( 42 ) in the first inner volume ( 316 ) of the tubular blank ( 31 ).   
     
     
         11 . The method of flow forming a shaped article ( 51 ) as claimed in  claim 10 , comprising:
 locating the tubular blank ( 31 ) on the mandrel ( 41 ) such that an inner shoulder ( 36 ) of the blank ( 31 ) longitudinally opposes an outer shoulder ( 47 ) of the mandrel ( 41 ); and   plastically deforming the tubular blank ( 31 ) over the mandrel ( 41 ) such that the inner shoulder ( 36 ) of the blank ( 31 ) translates longitudinally along the first mandrel region ( 42 ) towards the outer shoulder ( 47 ) of the mandrel ( 41 ).   
     
     
         12 . The method of flow forming a shaped article ( 51 ) as claimed in  claim 11 , further comprising:
 one or more rollers engaging a first outer surface ( 311 ) of the blank ( 31 ), which is radially outwards of a first inner surface ( 32 ) defining the first inner volume ( 316 ), thereby elongating the first inner surface ( 32 ) such that the inner shoulder ( 36 ) translates longitudinally along the first mandrel region ( 42 ) towards the outer shoulder ( 47 ) of the mandrel ( 41 );   the one or more rollers disengaging the first outer surface ( 311 ) in response to determining that the inner shoulder ( 36 ) of the blank ( 31 ) is abutting the outer mandrel shoulder ( 47 ); and   the one or more rollers engaging a second outer surface ( 312 ) of the blank ( 31 ), which is radially outwards of a second inner surface ( 33 ) defining the second inner volume ( 317 ), thereby elongating the second inner surface ( 33 ) along the second mandrel region ( 43 ) while keeping the inner shoulder ( 36 ) of the blank ( 31 ) in an abutting arrangement with the outer mandrel shoulder ( 47 ).   
     
     
         13 . The method of flow forming a shaped article ( 51 ) as claimed in  claim 11 , wherein longitudinal translation of the inner shoulder ( 36 ) along the first mandrel region ( 42 ) causes the second inner volume ( 317 ) of the blank ( 31 ) to translate in the same longitudinal direction such that it snugly receives the second mandrel region ( 43 ). 
     
     
         14 . The method of flow forming a shaped article ( 51 ) as claimed  claim 9 , wherein plastically deforming the tubular blank ( 31 ) over the mandrel ( 41 ) to create the shaped article ( 51 ) comprises elongating the tubular blank ( 31 ) without changing the inner diameters of the tubular blank ( 31 ) during the flow forming method.