Tube couplings

A tube coupling comprising a hollow body having an opening to be coupled with a tube, a collet having an annular portion having a central axis and resilient arms extending from the annular portion into the hollow body, said resilient arms being deflectable radially with respect to said central axis, a cam member, and means mounting said cam member on the body, said cam member having an internal tapered cam surface reducing in a direction extending out of the body, said cam surface being engageable with the resilient arms of the collet to compress the arms radially inwardly into engagement with the tube in the collet to hold a tube in the body, said collet being axially movable in either direction with respect to the cam member to increase or decrease the radial clamping action of the cam surface on the resilient arms against a tube encircled by the arms, and means located within said hollow body for varying additionally the compressive force applied to the collet by the cam surface of the cam member, said means being operable to adjust the position of the cam member relative to the body in the direction of the collet axis and thereby adjust the radial compressive force applied by the resilient arms to a tube within the collet.