Needle bar tensioning apparatus

A method of coupling a shifter adjustment assembly to a tufting machine having a longitudinal dimension that is perpendicular to a transverse dimension, the tufting machine comprising a shifter having a first end and a second end, the shifter comprising a first continuous shaft that extends between the first and second ends of the shifter and a second continuous shaft that extends between the first and second ends of the shifter, the method comprising:

• modifying or replacing the first continuous shaft of the shifter to provide a first shaft segment and a second shaft segment;
• modifying or replacing the second continuous shaft of the shifter to provide a third shaft segment and a fourth shaft segment;
• and
• coupling a shifter adjustment assembly to the first, second, third, and fourth shaft segments, wherein the shifter adjustment assembly comprises:
• a first body that is configured to couple to the first ends of the first and third shaft segments;
• a second body that is configured to couple to the first ends of the second and fourth shaft segments;
• and
• a coupling between the first body and the second body, wherein the coupling is configured to releasably secure an axial position of the first body with respect to the second body along the longitudinal dimension,
• wherein the first body and second body define respective complementary surfaces that are configured for sliding engagement so that:
• movement between the first body and the second body in the transverse dimension is restricted;
• and
• movement between the first body and the second body in the longitudinal dimension is permitted.

A tufting apparatus having a longitudinal dimension and a transverse dimension, the tufting apparatus comprising:

• a shifter comprising:
• first, second, third, and fourth shaft segments, each of the first, second, third, and fourth shaft segments having respective first and second ends,
• wherein the first and second shaft segments are aligned and spaced apart in a longitudinal dimension,
• wherein the third and fourth shaft segments are aligned and spaced apart in the longitudinal dimension,
• wherein the first ends of the first and second shaft segments face one another,
• wherein the first ends of the third and fourth shaft segments face one another,
• wherein the third and fourth shaft segments are offset from the first and second shaft segments in a transverse dimension that is perpendicular to the longitudinal dimension;
• and
• a shifter adjustment assembly comprising:
• a first body that is configured to couple to the first ends of the first and third shaft segments;
• a second body that is configured to couple to the first ends of the second and fourth shaft segments;
• a coupling between the first body and the second body, wherein the coupling is configured to releasably secure an axial position of the first body with respect to the second body along the longitudinal dimension,
• wherein the first body and second body define respective complementary surfaces that are configured for sliding engagement so that:
• movement between the first body and the second body in the transverse dimension is restricted;
• and
• movement between the first body and the second body in the longitudinal dimension is permitted,
• wherein the first body is coupled to the first end of the first shaft segment and the first end of the third shaft segment and the second body is coupled to the first end of the second shaft segment and the first end of the fourth shaft segment so that movement between the first body and the second body in the longitudinal dimension effects corresponding relative movement along the longitudinal dimension between:
• the first and second shaft segments, and
• the third and fourth shaft segments.