Patent ID: 7845295

Claim:
A sewing arm mechanism of an embroidery machine, the sewing arm mechanism comprising: a needle bar vertical drive unit for vertically moving a needle bar by using a rotational driving force of an upper shaft; a cloth pressing member vertical drive unit for vertically moving a cloth pressing member by using the rotational driving force of an upper shaft: and a thread take-up lever drive cam base formed to have an eccentric direction opposite to the eccentric direction of the needle bar drive cam in weight center, thereby to correct the unbalance of the upper shaft caused by the needle bar drive reaction force or the cloth pressing member drive reaction force exerted on the upper shaft when the needle bar vertical drive unit or the cloth pressing member vertical drive unit is driven, wherein the sewing arm mechanism is configured in such a manner that the needle bar drive reaction force exerted on the upper shaft by the driving of the needle bar vertical drive unit, and the cloth pressing member drive reaction force exerted on the upper shaft by the driving of the cloth pressing member vertical drive unit act in opposite directions of each other, whereby the magnitudes of the reaction forces exerted on the upper shaft can be cancelled with each other, wherein the needle bar vertical drive unit comprises: a needle bar drive cam fitted on the periphery of the upper shaft; and a needle bar drive rod rotationally engaged with the outer periphery of the needle bar drive cam, wherein the cloth pressing member vertical drive unit comprises: a cloth pressing member drive cam fitted on the periphery of the upper shaft; a cloth pressing member drive rod rotationally engaged with the outer periphery of the cloth pressing member drive cam; a cloth pressing member drive cam base engaged with the cloth pressing member drive cam on one side of the cloth pressing member drive cam, and wherein the cloth pressing member vertical drive unit further comprises: a cloth pressing member drive cam collar engaged on the other side of the cloth pressing member drive cam, the cloth pressing member drive cam collar being formed in a shape oppositely eccentric to the eccentric direction of the needle bar drive cam fitted on the periphery of the upper shaft.