medium speed 4-thread overlock sewing machine是什么意思

用法例句

According to the thread generation principle, the motion relationships among the needle, the lower and upper loopers of low and middle speed overlockers are quantitatively described.

以中、低速包缝机为研究对象，在定量构造出机针与上、下弯针之间的动作协调关系之后，提出对该类包缝机弯针机构进行精确尺度综合的方法。