Method and apparatus for forming internal threads in tubes

A machine system for internally threading a tube by a non-cutting process, said system comprising:

• a fixture having at least one work station (14) for supporting lower portions of said tube (12);
• a vertically movable fixture head (34) having tube clamp means (36) for contacting upper portions of said tube (12) in the work station (14) when the head (34) is at a given position, said head (34) further carrying a lower tap clamp (88) outboard of said work station (14) for contacting an end of a tap (204) protruding through the tube (12);
• an upper tap clamp (98) outboard of said work station (14) opposite from said lower tap clamp (88);
• a horizontally movable tapping unit (200) with a removable tap (204) therein for forming internal threads in said tube (12);
• a stripper finger (214) connected to said tapping unit (200) and adapted to contact an outer edge of said tube when the tap (204) has passed through the tube (12);
• means (208) for disconnecting the tap (204) from the tapping unit (200);
• and
• motive means (59) for downwardly moving said head (34) to bring said tube clamp means (36) into engagement with the tube (12) to secure it in the work station (12) until the tap (204) has passed through the tube (12) to form internal threads therein, said motive means being further operative to move said head (34) upwardly to clamp the end of the tap (204) protruding through the tube (12) between said upper (98) and lower tap (88) clamps after being disconnected from the tapping unit (200);
• whereby said tapping unit (200) may be retracted with said stripper finger (214) pulling the threaded tube (12) from the work station (14) while the tap (204) remains clamped.

A method of internally threading tubes said method comprising:

• stacking said tubes (12) in a vertical chute (130) having an outlet of a given size emptying into a work station (14) for supporting the tubes;
• upwardly moving a fixture head (34) located adjacent to the outlet to a first open position to allow one of the tubes (12) to roll into the work station (14), said head carrying an upper tube clamp member (36);
• downwardly moving said fixture head (34) to contact the tube (12) with the upper clamp member (36) to hold it securely in the work station (14);
• threading the internal surface of the tube (12) by advancing a forming tap (204) connected to a horizontally movable tapping unit (200) through the tube (12) until the end of the tap (204) protrudes through the tube (12);
• disconnecting the tap (204) from the unit (200);
• moving the head (34) upwardly to clamp the end of the tap (204) between a fixed upper tap clamp (98) and a lower tap clamp (88) carried by the head (34);
• removing the threaded tube (12) from the work station (14) by retracting the tapping unit (200) and pulling the tube over the unclamped end of the tap (204) with a stripper finger (124) connected to the unit (200);
• readvancing the unit (200) to retrieve the tap (204);
• moving the head (34) downwardly to carry the lower tap clamp (88) to a position sufficient to unclamp the end of the tap (204) but not so far as to impede removal of the tap (204) from the work station (14) by the upper tube clamp (36);
• retracting the unit (200) to remove the tap (204) from the work station (14);
• and
• moving the head (34) upwardly to allow the next tube (12) in the chute (130) to roll into the work station (14) for threading.

A machine system for threading sucker rod coupling tubes, said system comprising:

• a fixture (10) including a base (30) through which a movable shaft (56) driven by a cylinder (59) vertically extends through central portions thereof;
• means (18) on the base (30) defining two work stations (14, 16) one on each side of the shaft (56);
• a head (34) connected to the shaft (56) and having two arm portions (52, 54) extending over said work stations (14, 16) providing upper tube clamp members (36) for each station;
• a pair of vertical chutes (130, 132) each having outlets adjacent said arms (52, 54) of the head (34) for feeding tubes into said work stations (14, 16);
• a bracket (80) mounted to front portions of said head (34) and being configured so as to provide two lower tap clamps (88, 90) in vertical alignment below and outboard of each work station (14, 16);
• a pair of stationary upper tap clamps (98, 100) in vertical alignment above said lower tap clamps (88, 90);
• and
• a horizontally movable dual tapping unit (200) having two taps (204) for simultaneously threading tubes (12, 12') contained in the two work stations (14, 16);
• a stripper finger (214) under each tap (204) and mounted for movement in unison with the tapping unit (200);
• whereby movement of said head (34) by the shaft (56) automatically controls feeding of the tubes (12, 12') into the work stations (14, 16), clamping of said tubes with the upper tube clamps (36) during threading thereof;
• and clamping of said tap (204) by said upper (98, 100) and lower (88, 90) tap clamps when the threaded tubes (12, 12') are removed from the work stations (14, 16) by the stripper fingers (214) during retraction of the tapping unit (200).

Apparatus (152) for feeding tubes (12, 12') into two spaced chutes (130, 132) communicating with work stations (14, 16) in a fixture (10) having a movable head (34), said apparatus comprising:

• a conveyor (150) disposed between upper portions of said chutes (130, 132) for holding a plurality of tubes in an end-to-end relationship;
• a rocker arm assembly (152) having a swinging member (160) for sequentially knocking the tubes off of the conveyor (150) and into said chutes (130, 132);
• and
• means (172) coupled between the head (34) and the member (160) for controlling the swinging thereof as a function of movement of the head.