Patent ID: 6931986

Claim:
A strap machine automatically adjusting the strap tension comprising: A guide base for guiding a strap: An advance and retreat device consisting of a main wheel and a subordinate wheel positioned to abut to said main wheel with a gap, the strap passing through said gap clamped by said main and said subordinate wheel during operation of said main wheel, said main wheel driven by a power motor, said strap advanced and retreated by said main wheel and said subordinate wheel and guided to move in an arch frame of said strap machine to be strapped around an object placed on a worktable: and, Characterized by said subordinate wheel provided with two symmetrical sense members fixed flush with an outer circumferential surface of said subordinate wheel, a sensor positioned beside said subordinate wheel to touch and interact to said two sense members during rotation of said subordinate wheel, said sensor sensing advanced rounds and retreated rounds of said subordinate wheel, said sensor sending a signal of the advanced and the retreated rounds to a signal processor, said signal processor automatically calculating and recording the difference cardinality of the advanced and the retreated rounds, said processor sending the difference cardinality to a controller, said controller possible to control operation and stoppage of a motor of a strap tension device, said controller raising the current to said motor for augmenting pull force to delay the stopping of said motor so as to heighten the strap tension for an object being strapped in case of said difference cardinality becoming larger, said controller lowering the current to said motor to reduce the pulling force to stop said motor earlier and lowering the strap tension for an object in case of said difference cardinality becoming smaller.