This creation is a kind of cart type grass trimmer, main system includes gearbox driving, the manpower wheel of manpower handle control gearing, brake, and links height adjustment wheel in front end and constituted, wherein the outer cover screw both ends system of the differential gear in gearbox is via upper shield institute block, in order to thrown away outward when outer cover screw can be prevented surprisingly to be broken and the person that damages gearbox.本創作係一種推車式割草機，主要係包含有變速箱驅動、人力把手控制連動的人力輪、剎車，以及在前端連結高度調整輪所構成，其中變速箱內的差速齒輪之外蓋螺絲兩端係經由套蓋所擋止，俾可防止外蓋螺絲意外斷裂時向外甩出而損傷變速箱者。
