Automatic pet door for large pets

An automatic pet door system comprising:

• (a) a substantially rectangular frame disposed over an opening in a hinged door, wherein a lower portion of the frame defines a passage through the opening;
• (b) a pet door moveable between a lower closed position for closing the passage and an upper open position for opening the passage;
• (c) a drive means lifting the pet door between the closed and open positions;
• (d) a magnetic transmitter worn by a pet, the magnetic transmitter generating a predetermined transmitter signal;
• (e) a detector located proximate the frame, the detector generating a detector signal in response to the transmitter signal when the pet approaches the pet door at a predetermined distance from the pet door;
• (f) a control means engaging the drive means to lift the pet door between the closed and open positions in response to the detector signal;
• (g) a microelectromechanical systems gyro disposed on the hinged door, the microelectromechanical systems gyro generating a gyro signal in response to a movement of the hinged door, the gyro signal overriding the detector signal, thus preventing lifting the pet door between the closed and open positions;
• (h) a counterweight means biasing the pet door towards the open position;
• wherein the frame comprises two substantially parallel vertical outer tubes, each outer tube comprising a rectangular cross section and a channel disposed along the length of the outer tube, such that openings of the channels are facing each other and slidably receiving the pet door;
• wherein the drive means comprises:
• a motor disposed on the frame;
• a first pulley disposed on the motor;
• a first cable having a first end fixedly attached to the first pulley and a second end fixedly attached to the pet door;
• wherein the motor, when energized, spinning the first pulley thereby causing the first cable to pull the pet door up to the open position, and wherein the motor, when not energized, allowing the pet door to move down to the closed position by way of the force of gravity;
• wherein the drive means further comprises:
• a second pulley disposed on the frame;
• a pivot pin disposed on the pet door:
• a locking means disposed on the pet door, the locking means preventing movement of the pet door upwardly from the closed position unless the pet door is moved by way of the motor;
• wherein the second end is fixedly attached to the locking means and wherein the first cable is feeding over the second pulley and through the pivot pin;
• wherein the counterweight means further comprises:
• a second cable comprising a proximal end and a distal end, the proximal end fixedly attached to the pet door;
• a third pulley disposed on the frame;
• a fourth pulley disposed in one of the outer tubes;
• an inner tube comprising a circular cross section, the inner tube disposed in the same outer tube as the fourth pulley, the inner tube fixedly attached to the outer tube;
• a metal rod affixed to the distal end, the metal rod slidably moving inside the inner tube between a bottom position when the pet door is in the open position and a top position when the pet door is in the closed position;
• wherein the second cable feeding over the third and fourth pulleys.