Samsung patents hinge design with gears for foldable phones

1. A foldable electronic device comprising: a first housing; a second housing; a hinge module rotatably coupling the first housing and the second housing with each other; and a flexible display extending from one surface of the first housing to one surface of the second housing across an area in which the hinge module is disposed, wherein the hinge module comprises: a gear member comprising a first rotation axis to rotate the first housing and a second rotation axis to rotate the second housing; a first rotation bracket rotatably connected to the gear member; a second rotation bracket rotatably connected to the gear member; a first hinge plate rotatably connected to the first rotation bracket by being coupled with at least a part of the first rotation bracket; and a second hinge plate rotatably connected to the second rotation bracket by being coupled with at least a part of the second rotation bracket, wherein each of the first rotation bracket and the second rotation bracket comprises a base, a plurality of arms, and a fastening portion protruding from one surface of the base in a longitudinal direction of the foldable electronic device, wherein the fastening portion of the first rotation bracket is formed to fasten the first hinge plate and the first rotation bracket to each other, and the fastening portion of the second rotation bracket is formed to fasten the second hinge plate and the second rotation bracket to each other, wherein the fastening portion of the first rotation bracket forms a third rotation axis to rotate the first hinge plate therearound and the fastening portion of the second rotation bracket forms a fourth rotation axis to rotate the second hinge plate therearound, wherein the gear member comprises a first gear and a second gear, wherein the hinge module further comprises: a first hinge arm connected to the first gear; and a second hinge arm connected to the second gear, wherein the first hinge arm and the second hinge arm are configured to respectively rotate the first rotation bracket and the second rotation bracket in response to an unfolding or a folding of the first housing and the second housing, wherein the first gear comprises a first teeth portion and a first shaft connected to the first teeth portion, wherein the second gear comprises a second teeth portion and a second shaft connected to the second teeth portion, wherein the first hinge arm and the second hinge arm are fixedly connected to the first shaft and the second shaft, respectively, and wherein the first hinge arm and the second hinge arm are fixed by press-fitting of an asymmetric cross-sectional structure of an end of the first shaft and an asymmetric cross-sectional structure of an end of the second shaft.