Patent ID: 8857354

Claim:
A gas carrying threading device of sewing machine comprising: at least one looper having a hollow structure from a looper thread inlet to a looper loop-taker point thread outlet, a thread introduction portion inserting a looper thread which is led to said looper, a hollow thread guide portion having a thread guide outlet which connects to said thread introduction portion and performs a contact/separation for said looper thread inlet of said looper, a connecting portion moving said thread guide portion between a threading state that said thread guide outlet of said thread guide portion contacts to said looper thread inlet of said looper and a sewing state that said thread guide outlet of said thread guide portion separates from said looper thread inlet of said looper, and a gas supply portion feeding said looper thread from said thread introduction portion to said looper loop-taker point thread outlet through said looper when said thread guide portion is moved to said threading state, further comprising, when moving said connecting portion to contact and separate said thread guide outlet of said thread guide portion and said looper thread inlet of said looper freely, a looper threading/sewing changeover mechanism including, a push button for a pressing operation of a push button shaft which protrudes a control pin, a control groove cam which includes a first control groove cam portion, a second control groove cam portion and a third control groove cam portion which receive said control pin, a connecting movement plate which supports said thread guide portion and which is elastically repelled toward said threading state that said thread guide outlet of said thread guide portion contacts to said looper thread inlet of said looper by a first spring, and a connecting positioning plate rotating together with a main shaft integrally and having a peripheral surface that a tip portion of said push button shaft contacts and having a notch portion that said tip portion of said push button shaft is fitted, said looper threading/sewing changeover mechanism comprising a sewing state holding position which latches together said control pin at said first control groove cam portion at the time of a non-pressing operation of said push button and holds said sewing state, a threading preparatory state holding position which latches together said control pin at said second control groove cam portion at the time of a pressing operation of said push button, contacts said tip portion of said push button shaft to a peripheral surface of said connecting positioning plate and holds said connecting movement plate in a threading preparatory state, and a threading state holding position which fits said tip portion of said push button shaft into said notch portion of said connecting positioning plate by rotating said main shaft manually, fits loosely said control pin into said third control groove cam portion and holds said threading state.