see fig3 the release control means 102 includes an upper looper release change over arm 116 which connects the main change over arm 104 with the upper looper release body 96 the arm 116 is pivotally connected to the frame attachment plate 103 at its substantially central portion and also pivotally connected to the main change over arm 104 at its other end an engagement pin 117 is connected to the other end of the upper looper release change over arm 116 the engagement pin 117 is inserted in the groove 96a fig1 formed in the upper looper release body 96 the main change over arm 104 and first change over arm 112 are connected to each other by a second change over lever 118 with the above arrangement the main change over arm 104 is displaced longitudinally to drive the upper looper release body 96 through the upper looper release change over arm 116 along the upper looper shaft 83 the first change over arm 112 is then driven through the second change over arm 118 to displace the change over pin 110 and further the second change over arm 114 is driven through the first change over lever 115 to displace the back and.