Hinge assembly and foldable electronic device using the same

A hinge operable to a fixed open position where it is prevented from being closed and to a position where it is released from the fixed open position and is capable of being operated to a closed position, comprising:

• a first fixing assembly including a pintle and a first fixing member fixedly joined to the pintle, and wherein the electronic device includes first and second bodies pivotally connected to each other and one of the first and second bodies fixedly connected to the first fixing member;
• a second fixing member pivotally joined to the pintle and including a first position-limiting passage and a position limit defined thereon, and wherein the other of the first and second bodies is fixedly connected to the second fixing member;
• a first biasing device disposed on the pintle;
• a first positioning assembly including an urging member, a first cam, and a first cam follower disposed on the pintle and limited between the first biasing device and one side of a wall of the second fixing member, with the urging member including an extension extending over the first cam and selectively disposed in the first position-limiting passage, with the first cam including a locking slot selectively receiving the position limit and a second position-limiting passage receiving a length of the extension, with the first cam follower fixedly joined to the pintle, with the first cam and first cam follower in a first relative position where protrusions on a surface of the first cam are complementarily received in recesses on a surface of the first cam follower and the surfaces abut against each other, and in a second relative position where the protrusions are not received in the recesses and the surfaces are spaced from each other, with the extension disposed in and disengaged from the first position-limiting passage when the first cam and the first cam follower are in the first and second positions respectively, with the position limit disposed in and disengaged from the locking slot when the first cam and the first cam follower are in the first and second positions respectively;
• a second positioning assembly including a second cam member and a second cam follower disposed on the pintle, with the second cam member and the second fixing member articulated and pivoted together, with the second cam follower fixedly joined to the pintle, with the second cam and second cam follower in a first relative position where protrusions on a surface of the second cam are complementarily received in recesses on a surface of the second cam follower and the surfaces abut against each other, and in a second relative position where the protrusions are not received in the recesses and the surfaces are spaced from each other;
• and
• a second biasing device, and wherein the second positioning assembly is limited between the second biasing device and another side of the wall of the second fixing member;
• wherein the extension disengages from the first position-limiting passage, and the first cam and the first cam follower are in the second relative position, and the position limit disengages from the locking slot, when the hinge is in a first position and is closed;
• and
• wherein the hinge is operable to open to a second position from the first position, and wherein the hinge is in the fixed open position when it is in the second position, and wherein the urging member is pivoted by the second fixing member and the first cam is pivoted by the urging member during the operation of moving the hinge from the first to second positions, with the first position-limiting passage includes a distal end abutting against the extension, with the extension urges a terminal end of the second position-limiting passage, and wherein the extension is disposed in the first position-limiting passage, and the first cam and the first cam follower in the first relative position, and the position limit is received in the locking slot, when the hinge is in the second position;
• and
• wherein the hinge is operable to open to a third position from the second position, and wherein the extension disengages from the first position-limiting passage, and the first cam and the first cam follower are in the second relative position, when the hinge is in the third position, and wherein the hinge is operable to close rapidly from the third to the first positions, with the urging member adapted to be urged by the position limit during the operation of moving the hinge from third to the first positions.