a stitch control mechanism in a preferred embodiment according to the present invention will be described hereinafter with reference to the accompanying drawings . fig1 is a top plan view of the base plate 1 of a carriage . arranged on the base plate 1 are a pair of stitch cams 3 and 4 disposed respectively on the opposite sides of a raising cam , not shown , and stitch cam control units 5 and 6 for adjusting the respective positions of the stitch cams 3 and 4 . the stitch cam control units 5 and 6 are in a mirror - image relation to each other and therefore only the stitch cam control unit 5 will be described . a slot 7 is formed in the base plate 1 to guide the stitch cam 3 for oblique movement . a sliding member 8 is fitted for sliding movement in the slot 7 . the stitch cam 3 and holding plate 9 are fixed respectively to the lower and upper surfaces of the sliding member 8 . a stitch cam control motor 11 is mounted on a motor base , not shown , provided on the upper surface of the base plate 1 . a stitch cam control cam 14 having a spiral cam strip 13 is fixed to the output shaft 12 of the stitch cam control motor 11 . the spiral cam strip 13 is held between cam rollers 15 and 16 provided on the stitch cam holding plate 9 . the cam roller 15 is directly supported on the stitch cam holding plate 9 , while the cam roller 16 is supported pivotally on one end of a swing arm 17 pivotally supported for swing motion on the stitch cam holding plate 9 . an extension spring 18 is extended between the other end of the swing arm 17 and the stitch cam holding plate 9 so as to press the cam roller 16 against the spiral cam strip 13 . the stitch cam control cam 14 has a projection 19 . a proximity sensor 20 provided on the base plate 1 detects the projection 19 upon the arrival of the stitch cam control cam 14 at its zero position to stop the stitch cam control motor 11 . when the stitch cam control cam 14 is at the zero position , the cam rollers 15 and 16 nip the spiral cam strip 13 therebetween at a position at a maximum distance away from the shaft 12 holding the stitch cam control cam 14 , and the stitch cam 3 is positioned at the highest position . suppose that one course of a knit fabric 1 has been stitched and the carriage has been reversed for travel to the left , as viewed in fig1 to start stitching the next new course . before starting the carriage for travel to the left for stitching a new course , the stitch cam control units 5 and 6 are operated to raise the stitch cam 3 to the highest position and to lower the stitch cam 4 to a position for forming loops of a predetermined loop size . in raising the stitch cam 3 , a signal is given to the stitch cam control motor 11 of the preceding stitch cam control unit 5 to turn the stitch cam control cam 14 counterclockwise and , upon the detection of the projection 19 of the stitch cam control cam 14 by the proximity sensor 20 , the motor 11 is stopped . in this state , the cam rollers 15 and 16 nipping the spiral cam strip 13 is at the maximum distance from the output shaft 12 of the motor 11 and the stitch cam holding plate 9 is raised to its highest position . consequently , the stitch cam 3 fixed to the sliding member 8 fixed to the stitch cam holding plate 9 is raised to its highest position . on the other hand , the succeeding stitch cam control unit 6 , in which the stitch cam control cam 14 has been at an angular position where the projection 19 is positioned opposite to the proximity sensor 20 and the stitch cam holding plate 9 is at its highest position until the completion of stitching the previous course , must lower the stitch cam 4 to a desired position corresponding to a predetermined loop size . the angle of rotation of the output shaft 12 of the motor 11 necessary for lowering the stitch cam 4 to the desired position is determined by the number of pulses to be applied to the motor 11 . in the stitch cam control unit 6 on the right - hand side in fig1 the stitch cam control cam 14 is turned by the stitch cam control motor 11 to move the stitch cam holding plate 9 through the cam rollers 15 and 16 engaging the spiral cam strip 13 of the stitch cam control cam 14 to its lowest position together with the stitch cam 4 . suppose that the downward movement of the stitch cam 3 is obstructed by some cause during the downward movement of the stitch cam 3 . the stitch cam control motor 11 continues its rotation to rotate the stitch cam control cam 14 continuously so that the cam roller 16 is pressed continuously by the spiral cam strip 13 even if the downward movement of the stitch cam 3 is obstructed . then , a safety action is exercised . although the cam roller 16 in contact with the inner surface of the spiral cam strip 13 is pressed by the spiral cam strip 13 as the working radius of the spiral cam strip 13 decreases gradually , the stitch cam holding plate 9 will not move downward . then , the swing arm 17 is turned counterclockwise against the tension of the spring 18 through the cam roller 16 by the spiral cam plate 13 to prevent inducing excessive stress in the component parts . a stitch control mechanism in accordance with the present invention employs a pair of cam rollers supported on a stitch cam holding plate so as to nip the spiral cam strip of a stitch cam control cam continuously in shifting a stitch cam . accordingly , the rotating stitch cam control cam and the linearly moving stitch cam holding plate are interlocked closely without allowing any lost motion between the stitch cam control cam and the stitch cam holding plate so that the stitch cam can accurately be shifted in response to the rotation of the stitch cam control cam .