Method and apparatus for interlocking tubular members

Abstract

A method and apparatus for interlocking at least one first tube ( 10 ) having a first diametric spacing between opposite points of the tube wall with a second tube ( 4 ) having a second diametric spacing between opposite points of the tube wall which is larger than the first diametric spacing. The first tube is loaded over a mandrel ( 50 ) having a punching end ( 54 ), and disposed into a holding block ( 30 ) having a holding cavity ( 32 ) conforming closely to the outer surface of the first tube. The second tube is disposed over a receiving block ( 40 ), which has a receiving cavity conforming closely to the outer surface of the first tube. The punching end of the mandrel is driven through the second tube and into the cavity in the receiving block, followed by the first tube. When the first tube reaches a lower limit of the receiving cavity, the first tube is compressed axially. The mandrel supports the interior of the first tube, the holding cavity prevents the trailing portion of the first tube from swelling outwardly, and the receiving cavity prevents the leading portion of the first tube from swelling outwardly. Thus, the portion of the first tube disposed inside the second tubular member swells under the axial compressive force, permanently interlocking the first tube with the second tube. The punching steps can be separated from the remaining steps of the method of the invention, or the second tube can be pre-punched. In further embodiments the method and apparatus of the invention can create a clinched interlock and/or a ‘T’-shaped interlocked assembly.

1 . A method of interlocking a first tubular member having a first diametric spacing between opposite points of a wall of the first tubular member with a second tubular member having a second diametric spacing diametric spacing between opposite points of a wall of the first tubular member which is larger than or equal to the first diametric spacing, comprising the steps of: 
 a. punching through a wall of the second tubular member to create opposed holes each having a diametric spacing between opposite points of an edge of the hole substantially equal to the diametric spacing of the first tubular member,    b. disposing through the first tubular member a mandrel having a body with an exterior surface substantially conforming to an interior surface of the first tubular member, to support the interior surface of the first tubular member;    c. disposing a trailing end of the first tubular member within a holding cavity in a holding block, the holding cavity supporting an outer surface of the trailing end;    d. driving a leading end of the first tubular member through the wall of the second tubular member and into a receiving cavity in a receiving block, the receiving cavity supporting an outer surface of the leading end, until the leading end reaches a lower limit; and    e. applying an axial compressive force to the first tubular member; 
 whereby an unsupported portion of the first tubular member contained within the second tubular member swells under the axial compressive force, interlocking the first tubular member to the second tubular member.  
   
   
   
       2 . The method of  claim 1  wherein the mandrel is provided with a punching end and the steps of punching through the wall of the second tubular member and driving the leading end of the first tubular member through the wall of the second tubular member are performed in a single stroke.  
   
   
       3 . The method of  claim 1  wherein an entrance to the receiving cavity is bevelled.  
   
   
       4 . The method of  claim 1  wherein the second tubular member is disposed within a channel having a configuration conforming to an outer surface of the second tubular member and extending over an entrance to the receiving cavity.  
   
   
       5 . The method of  claim 4  wherein the channel is formed in the receiving block.  
   
   
       6 . The method of  claim 5  wherein the holding block is provided with a channel conforming to an outer surface of the second tubular member and extending over an entrance to the holding cavity.  
   
   
       7 . The method of  claim 6  including, before step a, the step of clamping the holding block against the receiving block.  
   
   
       8 . The method of  claim 7  wherein the first tubular member is driven through the second tubular member by a punch plate to which the mandrel is anchored.  
   
   
       9 . The method of  claim 1  for interlocking a plurality of first tubular members with the second tubular member.  
   
   
       10 . The method of  claim 1  wherein the lower limit of the receiving cavity is defined by a tube seat.  
   
   
       11 . A method of interlocking a first tubular member having a first diametric spacing between opposite points of a wall of the first tubular member with a second tubular member having a second diametric spacing between opposite points of a wall of the second tubular member which is larger than or equal to the first diametric spacing, and opposed holes each having a diametric spacing diametric spacing between opposite points of an edge of the hole substantially equal to the diametric spacing of the first tubular member, comprising the steps of: 
 a. disposing through the first tubular member a mandrel having a body with an exterior surface substantially conforming to an interior surface of the first tubular member, to support the interior surface of the first tubular member;    b. disposing a trailing end of the first tubular member within a holding cavity in a holding block, the holding cavity supporting an outer surface of the trailing end;    c. driving the a leading end of the first tubular member through the wall of the second tubular member and into a receiving cavity in a receiving block, the receiving cavity supporting an outer surface of the leading end, until the leading end reaches a lower limit; and    d. applying an axial compressive force to the first tubular member; 
 whereby an unsupported portion of the first tubular member contained within the second tubular member swells under the axial compressive force, interlocking the first tubular member to the second tubular member.  
   
   
   
       12 . The method of  claim 1  comprising, before the step of driving a leading end of the first tubular member through the wall of the second tubular member, the step of punching through a wall of the second tubular member.  
   
   
       13 . The method of  claim 11  wherein the mandrel is provided with a punching end and comprising, simultaneously with the step of driving a leading end of the first tubular member through the wall of the second tubular member, the step of punching through a wall of the second tubular member.  
   
   
       14 . An apparatus for interlocking at least one first tubular member having a first diametric spacing between opposite points of a wall of the first tubular member with a second tubular member having a second diametric spacing between opposite points of a wall of the second tubular member which is larger than the first diametric spacing, comprising 
 a holding block having at least one holding cavity for supporting an outer surface of a trailing end of the first tubular member,    a receiving block having at least one receiving cavity disposed in opposition to the holding cavity, for supporting an outer surface of a leading end of the first tubular member, the receiving cavity having a lower limit,    at least one mandrel having a body with an exterior surface substantially conforming to an interior surface of the first tubular member, to support the interior surface of the first tubular member, extending through the holding cavity, and    a punch,    whereby the punch creates opposed holes in a wall of the second tubular member, and the mandrel and a leading end of the first tubular member are driven through the wall of the second tubular member and into the receiving cavity, and when the leading end of the first tubular member reaches the lower limit an axial compressive force applied to the first tubular member causes an unsupported portion of the first tubular member contained within the second tubular member to swell under the axial compressive force, interlocking the first tubular member to the second tubular member.    
   
   
       15 . The apparatus of  claim 14  wherein the punch is provided by a punching end of the mandrel.  
   
   
       16 . The apparatus of  claim 14  wherein an entrance to the receiving cavity is bevelled.  
   
   
       17 . The apparatus of  claim 14  wherein the second tubular member is disposed within a channel having a configuration conforming to an outer surface of the second tubular member and extending over an entrance to the receiving cavity.  
   
   
       18 . The apparatus of  claim 17  wherein the channel is formed in the receiving block.  
   
   
       19 . The apparatus of  claim 18  wherein the holding block is provided with a channel conforming to an outer surface of the second tubular member and extending over an entrance to the holding cavity.  
   
   
       20 . The apparatus of  claim 19  wherein at least one of the holding block and the receiving block are movable and can be moved toward the other of the holding block and the receiving block.  
   
   
       21 . The apparatus of  claim 14  wherein the mandrel and first tubular member are driven through the second tubular member by the punch plate.  
   
   
       22 . The apparatus of  claim 14  comprising a plurality of mandrels, holding cavities and receiving cavities for interlocking a plurality of first tubular members with at least one second tubular member.  
   
   
       23 . The apparatus of  claim 14  wherein the lower limit of the receiving cavity is defined by a tube seat.  
   
   
       24 . A method of interlocking a first tubular member having a first diametric spacing between opposite points of a wall of the first tubular member with a second tubular member having a second diametric spacing diametric spacing between opposite points of a wall of the first tubular member which is larger than or equal to the first diametric spacing, comprising the steps of: 
 a. punching through a wall of the second tubular member to create a hole having a diametric spacing between opposite points of an edge of the hole substantially equal to the diametric spacing of the first tubular member,    b. disposing through the first tubular member a mandrel having a body with an exterior surface substantially conforming to an interior surface of the first tubular member, to support the interior surface of the first tubular member;    c. disposing a trailing end of the first tubular member within a holding cavity in a holding block, the holding cavity supporting an outer surface of the trailing end;    d. driving a leading end of the first tubular member through the wall of the second tubular member and against a diametrically opposed point of the wall of the second tubular member,    e. supporting the diametrically opposed point of the wall of the second tubular member to thus create a lower limit for the leading end of the first tubular member; and    f. applying an axial compressive force to the first tubular member; 
 whereby an unsupported portion of the first tubular member contained within the second tubular member swells under the axial compressive force, interlocking the first tubular member to the second tubular member.  
   
   
   
       25 . The method of  claim 24  wherein the mandrel is provided with a punching end and the step of punching through the wall of the second tubular member and driving the leading end of the first tubular member through the wall of the second tubular member are performed in a single stroke.  
   
   
       26 . The method of  claim 24  wherein the second tubular member is disposed within a channel having a configuration conforming to an outer surface of the second tubular member to support the diametrically opposed point of the wall of the second tubular member.  
   
   
       27 . The method of  claim 26  wherein the channel is formed in the receiving block.  
   
   
       28 . The method of  claim 27  wherein the holding block is provided with a channel conforming to an outer surface of the second tubular member and extending over an entrance to the holding cavity.  
   
   
       29 . The method of  claim 28  including, before step a, the step of clamping the holding block against the receiving block.  
   
   
       30 . The method of  claim 29  wherein the first tubular member is driven through the second tubular member by a punch plate to which the mandrel is anchored.  
   
   
       31 . The method of  claim 24  for interlocking a plurality of first tubular members with the second tubular member.